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3782 lines
106 KiB
3782 lines
106 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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/* |
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* linux/mm/filemap.c |
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* |
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* Copyright (C) 1994-1999 Linus Torvalds |
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*/ |
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|
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/* |
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* This file handles the generic file mmap semantics used by |
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* most "normal" filesystems (but you don't /have/ to use this: |
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* the NFS filesystem used to do this differently, for example) |
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*/ |
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#include <linux/export.h> |
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#include <linux/compiler.h> |
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#include <linux/dax.h> |
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#include <linux/fs.h> |
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#include <linux/sched/signal.h> |
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#include <linux/uaccess.h> |
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#include <linux/capability.h> |
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#include <linux/kernel_stat.h> |
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#include <linux/gfp.h> |
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#include <linux/mm.h> |
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#include <linux/swap.h> |
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#include <linux/mman.h> |
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#include <linux/pagemap.h> |
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#include <linux/file.h> |
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#include <linux/uio.h> |
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#include <linux/error-injection.h> |
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#include <linux/hash.h> |
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#include <linux/writeback.h> |
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#include <linux/backing-dev.h> |
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#include <linux/pagevec.h> |
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#include <linux/blkdev.h> |
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#include <linux/security.h> |
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#include <linux/cpuset.h> |
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#include <linux/hugetlb.h> |
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#include <linux/memcontrol.h> |
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#include <linux/cleancache.h> |
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#include <linux/shmem_fs.h> |
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#include <linux/rmap.h> |
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#include <linux/delayacct.h> |
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#include <linux/psi.h> |
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#include <linux/ramfs.h> |
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#include <linux/page_idle.h> |
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#include <asm/pgalloc.h> |
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#include <asm/tlbflush.h> |
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#include "internal.h" |
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|
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#define CREATE_TRACE_POINTS |
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#include <trace/events/filemap.h> |
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|
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/* |
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* FIXME: remove all knowledge of the buffer layer from the core VM |
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*/ |
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#include <linux/buffer_head.h> /* for try_to_free_buffers */ |
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|
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#include <asm/mman.h> |
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|
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/* |
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* Shared mappings implemented 30.11.1994. It's not fully working yet, |
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* though. |
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* |
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* Shared mappings now work. 15.8.1995 Bruno. |
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* |
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* finished 'unifying' the page and buffer cache and SMP-threaded the |
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* page-cache, 21.05.1999, Ingo Molnar <[email protected]> |
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* |
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* SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <[email protected]> |
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*/ |
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|
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/* |
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* Lock ordering: |
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* |
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* ->i_mmap_rwsem (truncate_pagecache) |
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* ->private_lock (__free_pte->__set_page_dirty_buffers) |
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* ->swap_lock (exclusive_swap_page, others) |
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* ->i_pages lock |
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* |
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* ->i_mutex |
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* ->i_mmap_rwsem (truncate->unmap_mapping_range) |
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* |
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* ->mmap_lock |
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* ->i_mmap_rwsem |
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* ->page_table_lock or pte_lock (various, mainly in memory.c) |
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* ->i_pages lock (arch-dependent flush_dcache_mmap_lock) |
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* |
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* ->mmap_lock |
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* ->lock_page (access_process_vm) |
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* |
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* ->i_mutex (generic_perform_write) |
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* ->mmap_lock (fault_in_pages_readable->do_page_fault) |
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* |
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* bdi->wb.list_lock |
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* sb_lock (fs/fs-writeback.c) |
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* ->i_pages lock (__sync_single_inode) |
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* |
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* ->i_mmap_rwsem |
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* ->anon_vma.lock (vma_adjust) |
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* |
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* ->anon_vma.lock |
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* ->page_table_lock or pte_lock (anon_vma_prepare and various) |
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* |
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* ->page_table_lock or pte_lock |
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* ->swap_lock (try_to_unmap_one) |
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* ->private_lock (try_to_unmap_one) |
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* ->i_pages lock (try_to_unmap_one) |
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* ->lruvec->lru_lock (follow_page->mark_page_accessed) |
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* ->lruvec->lru_lock (check_pte_range->isolate_lru_page) |
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* ->private_lock (page_remove_rmap->set_page_dirty) |
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* ->i_pages lock (page_remove_rmap->set_page_dirty) |
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* bdi.wb->list_lock (page_remove_rmap->set_page_dirty) |
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* ->inode->i_lock (page_remove_rmap->set_page_dirty) |
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* ->memcg->move_lock (page_remove_rmap->lock_page_memcg) |
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* bdi.wb->list_lock (zap_pte_range->set_page_dirty) |
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* ->inode->i_lock (zap_pte_range->set_page_dirty) |
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* ->private_lock (zap_pte_range->__set_page_dirty_buffers) |
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* |
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* ->i_mmap_rwsem |
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* ->tasklist_lock (memory_failure, collect_procs_ao) |
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*/ |
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|
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static void page_cache_delete(struct address_space *mapping, |
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struct page *page, void *shadow) |
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{ |
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XA_STATE(xas, &mapping->i_pages, page->index); |
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unsigned int nr = 1; |
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|
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mapping_set_update(&xas, mapping); |
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|
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/* hugetlb pages are represented by a single entry in the xarray */ |
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if (!PageHuge(page)) { |
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xas_set_order(&xas, page->index, compound_order(page)); |
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nr = compound_nr(page); |
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} |
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|
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VM_BUG_ON_PAGE(!PageLocked(page), page); |
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VM_BUG_ON_PAGE(PageTail(page), page); |
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VM_BUG_ON_PAGE(nr != 1 && shadow, page); |
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|
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xas_store(&xas, shadow); |
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xas_init_marks(&xas); |
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|
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page->mapping = NULL; |
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/* Leave page->index set: truncation lookup relies upon it */ |
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|
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if (shadow) { |
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mapping->nrexceptional += nr; |
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/* |
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* Make sure the nrexceptional update is committed before |
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* the nrpages update so that final truncate racing |
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* with reclaim does not see both counters 0 at the |
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* same time and miss a shadow entry. |
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*/ |
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smp_wmb(); |
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} |
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mapping->nrpages -= nr; |
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} |
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|
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static void unaccount_page_cache_page(struct address_space *mapping, |
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struct page *page) |
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{ |
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int nr; |
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|
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/* |
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* if we're uptodate, flush out into the cleancache, otherwise |
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* invalidate any existing cleancache entries. We can't leave |
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* stale data around in the cleancache once our page is gone |
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*/ |
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if (PageUptodate(page) && PageMappedToDisk(page)) |
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cleancache_put_page(page); |
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else |
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cleancache_invalidate_page(mapping, page); |
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|
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VM_BUG_ON_PAGE(PageTail(page), page); |
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VM_BUG_ON_PAGE(page_mapped(page), page); |
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if (!IS_ENABLED(CONFIG_DEBUG_VM) && unlikely(page_mapped(page))) { |
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int mapcount; |
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|
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pr_alert("BUG: Bad page cache in process %s pfn:%05lx\n", |
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current->comm, page_to_pfn(page)); |
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dump_page(page, "still mapped when deleted"); |
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dump_stack(); |
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add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE); |
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mapcount = page_mapcount(page); |
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if (mapping_exiting(mapping) && |
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page_count(page) >= mapcount + 2) { |
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/* |
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* All vmas have already been torn down, so it's |
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* a good bet that actually the page is unmapped, |
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* and we'd prefer not to leak it: if we're wrong, |
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* some other bad page check should catch it later. |
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*/ |
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page_mapcount_reset(page); |
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page_ref_sub(page, mapcount); |
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} |
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} |
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|
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/* hugetlb pages do not participate in page cache accounting. */ |
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if (PageHuge(page)) |
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return; |
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nr = thp_nr_pages(page); |
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|
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__mod_lruvec_page_state(page, NR_FILE_PAGES, -nr); |
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if (PageSwapBacked(page)) { |
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__mod_lruvec_page_state(page, NR_SHMEM, -nr); |
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if (PageTransHuge(page)) |
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__mod_lruvec_page_state(page, NR_SHMEM_THPS, -nr); |
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} else if (PageTransHuge(page)) { |
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__mod_lruvec_page_state(page, NR_FILE_THPS, -nr); |
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filemap_nr_thps_dec(mapping); |
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} |
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|
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/* |
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* At this point page must be either written or cleaned by |
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* truncate. Dirty page here signals a bug and loss of |
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* unwritten data. |
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* |
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* This fixes dirty accounting after removing the page entirely |
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* but leaves PageDirty set: it has no effect for truncated |
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* page and anyway will be cleared before returning page into |
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* buddy allocator. |
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*/ |
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if (WARN_ON_ONCE(PageDirty(page))) |
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account_page_cleaned(page, mapping, inode_to_wb(mapping->host)); |
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} |
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|
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/* |
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* Delete a page from the page cache and free it. Caller has to make |
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* sure the page is locked and that nobody else uses it - or that usage |
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* is safe. The caller must hold the i_pages lock. |
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*/ |
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void __delete_from_page_cache(struct page *page, void *shadow) |
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{ |
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struct address_space *mapping = page->mapping; |
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trace_mm_filemap_delete_from_page_cache(page); |
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unaccount_page_cache_page(mapping, page); |
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page_cache_delete(mapping, page, shadow); |
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} |
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static void page_cache_free_page(struct address_space *mapping, |
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struct page *page) |
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{ |
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void (*freepage)(struct page *); |
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freepage = mapping->a_ops->freepage; |
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if (freepage) |
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freepage(page); |
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if (PageTransHuge(page) && !PageHuge(page)) { |
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page_ref_sub(page, thp_nr_pages(page)); |
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VM_BUG_ON_PAGE(page_count(page) <= 0, page); |
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} else { |
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put_page(page); |
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} |
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} |
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|
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/** |
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* delete_from_page_cache - delete page from page cache |
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* @page: the page which the kernel is trying to remove from page cache |
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* |
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* This must be called only on pages that have been verified to be in the page |
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* cache and locked. It will never put the page into the free list, the caller |
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* has a reference on the page. |
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*/ |
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void delete_from_page_cache(struct page *page) |
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{ |
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struct address_space *mapping = page_mapping(page); |
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unsigned long flags; |
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BUG_ON(!PageLocked(page)); |
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xa_lock_irqsave(&mapping->i_pages, flags); |
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__delete_from_page_cache(page, NULL); |
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xa_unlock_irqrestore(&mapping->i_pages, flags); |
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page_cache_free_page(mapping, page); |
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} |
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EXPORT_SYMBOL(delete_from_page_cache); |
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|
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/* |
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* page_cache_delete_batch - delete several pages from page cache |
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* @mapping: the mapping to which pages belong |
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* @pvec: pagevec with pages to delete |
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* |
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* The function walks over mapping->i_pages and removes pages passed in @pvec |
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* from the mapping. The function expects @pvec to be sorted by page index |
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* and is optimised for it to be dense. |
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* It tolerates holes in @pvec (mapping entries at those indices are not |
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* modified). The function expects only THP head pages to be present in the |
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* @pvec. |
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* |
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* The function expects the i_pages lock to be held. |
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*/ |
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static void page_cache_delete_batch(struct address_space *mapping, |
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struct pagevec *pvec) |
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{ |
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XA_STATE(xas, &mapping->i_pages, pvec->pages[0]->index); |
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int total_pages = 0; |
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int i = 0; |
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struct page *page; |
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mapping_set_update(&xas, mapping); |
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xas_for_each(&xas, page, ULONG_MAX) { |
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if (i >= pagevec_count(pvec)) |
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break; |
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/* A swap/dax/shadow entry got inserted? Skip it. */ |
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if (xa_is_value(page)) |
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continue; |
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/* |
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* A page got inserted in our range? Skip it. We have our |
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* pages locked so they are protected from being removed. |
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* If we see a page whose index is higher than ours, it |
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* means our page has been removed, which shouldn't be |
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* possible because we're holding the PageLock. |
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*/ |
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if (page != pvec->pages[i]) { |
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VM_BUG_ON_PAGE(page->index > pvec->pages[i]->index, |
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page); |
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continue; |
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} |
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WARN_ON_ONCE(!PageLocked(page)); |
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|
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if (page->index == xas.xa_index) |
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page->mapping = NULL; |
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/* Leave page->index set: truncation lookup relies on it */ |
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|
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/* |
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* Move to the next page in the vector if this is a regular |
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* page or the index is of the last sub-page of this compound |
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* page. |
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*/ |
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if (page->index + compound_nr(page) - 1 == xas.xa_index) |
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i++; |
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xas_store(&xas, NULL); |
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total_pages++; |
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} |
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mapping->nrpages -= total_pages; |
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} |
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|
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void delete_from_page_cache_batch(struct address_space *mapping, |
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struct pagevec *pvec) |
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{ |
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int i; |
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unsigned long flags; |
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|
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if (!pagevec_count(pvec)) |
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return; |
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xa_lock_irqsave(&mapping->i_pages, flags); |
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for (i = 0; i < pagevec_count(pvec); i++) { |
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trace_mm_filemap_delete_from_page_cache(pvec->pages[i]); |
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|
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unaccount_page_cache_page(mapping, pvec->pages[i]); |
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} |
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page_cache_delete_batch(mapping, pvec); |
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xa_unlock_irqrestore(&mapping->i_pages, flags); |
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for (i = 0; i < pagevec_count(pvec); i++) |
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page_cache_free_page(mapping, pvec->pages[i]); |
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} |
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|
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int filemap_check_errors(struct address_space *mapping) |
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{ |
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int ret = 0; |
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/* Check for outstanding write errors */ |
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if (test_bit(AS_ENOSPC, &mapping->flags) && |
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test_and_clear_bit(AS_ENOSPC, &mapping->flags)) |
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ret = -ENOSPC; |
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if (test_bit(AS_EIO, &mapping->flags) && |
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test_and_clear_bit(AS_EIO, &mapping->flags)) |
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ret = -EIO; |
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return ret; |
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} |
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EXPORT_SYMBOL(filemap_check_errors); |
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|
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static int filemap_check_and_keep_errors(struct address_space *mapping) |
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{ |
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/* Check for outstanding write errors */ |
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if (test_bit(AS_EIO, &mapping->flags)) |
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return -EIO; |
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if (test_bit(AS_ENOSPC, &mapping->flags)) |
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return -ENOSPC; |
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return 0; |
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} |
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|
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/** |
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* __filemap_fdatawrite_range - start writeback on mapping dirty pages in range |
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* @mapping: address space structure to write |
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* @start: offset in bytes where the range starts |
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* @end: offset in bytes where the range ends (inclusive) |
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* @sync_mode: enable synchronous operation |
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* |
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* Start writeback against all of a mapping's dirty pages that lie |
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* within the byte offsets <start, end> inclusive. |
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* |
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* If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as |
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* opposed to a regular memory cleansing writeback. The difference between |
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* these two operations is that if a dirty page/buffer is encountered, it must |
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* be waited upon, and not just skipped over. |
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* |
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* Return: %0 on success, negative error code otherwise. |
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*/ |
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int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start, |
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loff_t end, int sync_mode) |
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{ |
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int ret; |
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struct writeback_control wbc = { |
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.sync_mode = sync_mode, |
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.nr_to_write = LONG_MAX, |
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.range_start = start, |
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.range_end = end, |
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}; |
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|
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if (!mapping_can_writeback(mapping) || |
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!mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) |
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return 0; |
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|
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wbc_attach_fdatawrite_inode(&wbc, mapping->host); |
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ret = do_writepages(mapping, &wbc); |
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wbc_detach_inode(&wbc); |
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return ret; |
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} |
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|
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static inline int __filemap_fdatawrite(struct address_space *mapping, |
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int sync_mode) |
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{ |
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return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode); |
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} |
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|
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int filemap_fdatawrite(struct address_space *mapping) |
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{ |
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return __filemap_fdatawrite(mapping, WB_SYNC_ALL); |
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} |
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EXPORT_SYMBOL(filemap_fdatawrite); |
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|
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int filemap_fdatawrite_range(struct address_space *mapping, loff_t start, |
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loff_t end) |
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{ |
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return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL); |
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} |
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EXPORT_SYMBOL(filemap_fdatawrite_range); |
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|
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/** |
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* filemap_flush - mostly a non-blocking flush |
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* @mapping: target address_space |
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* |
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* This is a mostly non-blocking flush. Not suitable for data-integrity |
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* purposes - I/O may not be started against all dirty pages. |
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* |
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* Return: %0 on success, negative error code otherwise. |
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*/ |
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int filemap_flush(struct address_space *mapping) |
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{ |
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return __filemap_fdatawrite(mapping, WB_SYNC_NONE); |
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} |
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EXPORT_SYMBOL(filemap_flush); |
|
|
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/** |
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* filemap_range_has_page - check if a page exists in range. |
|
* @mapping: address space within which to check |
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* @start_byte: offset in bytes where the range starts |
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* @end_byte: offset in bytes where the range ends (inclusive) |
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* |
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* Find at least one page in the range supplied, usually used to check if |
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* direct writing in this range will trigger a writeback. |
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* |
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* Return: %true if at least one page exists in the specified range, |
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* %false otherwise. |
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*/ |
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bool filemap_range_has_page(struct address_space *mapping, |
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loff_t start_byte, loff_t end_byte) |
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{ |
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struct page *page; |
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XA_STATE(xas, &mapping->i_pages, start_byte >> PAGE_SHIFT); |
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pgoff_t max = end_byte >> PAGE_SHIFT; |
|
|
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if (end_byte < start_byte) |
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return false; |
|
|
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rcu_read_lock(); |
|
for (;;) { |
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page = xas_find(&xas, max); |
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if (xas_retry(&xas, page)) |
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continue; |
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/* Shadow entries don't count */ |
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if (xa_is_value(page)) |
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continue; |
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/* |
|
* We don't need to try to pin this page; we're about to |
|
* release the RCU lock anyway. It is enough to know that |
|
* there was a page here recently. |
|
*/ |
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break; |
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} |
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rcu_read_unlock(); |
|
|
|
return page != NULL; |
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} |
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EXPORT_SYMBOL(filemap_range_has_page); |
|
|
|
static void __filemap_fdatawait_range(struct address_space *mapping, |
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loff_t start_byte, loff_t end_byte) |
|
{ |
|
pgoff_t index = start_byte >> PAGE_SHIFT; |
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pgoff_t end = end_byte >> PAGE_SHIFT; |
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struct pagevec pvec; |
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int nr_pages; |
|
|
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if (end_byte < start_byte) |
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return; |
|
|
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pagevec_init(&pvec); |
|
while (index <= end) { |
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unsigned i; |
|
|
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nr_pages = pagevec_lookup_range_tag(&pvec, mapping, &index, |
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end, PAGECACHE_TAG_WRITEBACK); |
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if (!nr_pages) |
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break; |
|
|
|
for (i = 0; i < nr_pages; i++) { |
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struct page *page = pvec.pages[i]; |
|
|
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wait_on_page_writeback(page); |
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ClearPageError(page); |
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} |
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pagevec_release(&pvec); |
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cond_resched(); |
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} |
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} |
|
|
|
/** |
|
* filemap_fdatawait_range - wait for writeback to complete |
|
* @mapping: address space structure to wait for |
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* @start_byte: offset in bytes where the range starts |
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* @end_byte: offset in bytes where the range ends (inclusive) |
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* |
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* Walk the list of under-writeback pages of the given address space |
|
* in the given range and wait for all of them. Check error status of |
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* the address space and return it. |
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* |
|
* Since the error status of the address space is cleared by this function, |
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* callers are responsible for checking the return value and handling and/or |
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* reporting the error. |
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* |
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* Return: error status of the address space. |
|
*/ |
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int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte, |
|
loff_t end_byte) |
|
{ |
|
__filemap_fdatawait_range(mapping, start_byte, end_byte); |
|
return filemap_check_errors(mapping); |
|
} |
|
EXPORT_SYMBOL(filemap_fdatawait_range); |
|
|
|
/** |
|
* filemap_fdatawait_range_keep_errors - wait for writeback to complete |
|
* @mapping: address space structure to wait for |
|
* @start_byte: offset in bytes where the range starts |
|
* @end_byte: offset in bytes where the range ends (inclusive) |
|
* |
|
* Walk the list of under-writeback pages of the given address space in the |
|
* given range and wait for all of them. Unlike filemap_fdatawait_range(), |
|
* this function does not clear error status of the address space. |
|
* |
|
* Use this function if callers don't handle errors themselves. Expected |
|
* call sites are system-wide / filesystem-wide data flushers: e.g. sync(2), |
|
* fsfreeze(8) |
|
*/ |
|
int filemap_fdatawait_range_keep_errors(struct address_space *mapping, |
|
loff_t start_byte, loff_t end_byte) |
|
{ |
|
__filemap_fdatawait_range(mapping, start_byte, end_byte); |
|
return filemap_check_and_keep_errors(mapping); |
|
} |
|
EXPORT_SYMBOL(filemap_fdatawait_range_keep_errors); |
|
|
|
/** |
|
* file_fdatawait_range - wait for writeback to complete |
|
* @file: file pointing to address space structure to wait for |
|
* @start_byte: offset in bytes where the range starts |
|
* @end_byte: offset in bytes where the range ends (inclusive) |
|
* |
|
* Walk the list of under-writeback pages of the address space that file |
|
* refers to, in the given range and wait for all of them. Check error |
|
* status of the address space vs. the file->f_wb_err cursor and return it. |
|
* |
|
* Since the error status of the file is advanced by this function, |
|
* callers are responsible for checking the return value and handling and/or |
|
* reporting the error. |
|
* |
|
* Return: error status of the address space vs. the file->f_wb_err cursor. |
|
*/ |
|
int file_fdatawait_range(struct file *file, loff_t start_byte, loff_t end_byte) |
|
{ |
|
struct address_space *mapping = file->f_mapping; |
|
|
|
__filemap_fdatawait_range(mapping, start_byte, end_byte); |
|
return file_check_and_advance_wb_err(file); |
|
} |
|
EXPORT_SYMBOL(file_fdatawait_range); |
|
|
|
/** |
|
* filemap_fdatawait_keep_errors - wait for writeback without clearing errors |
|
* @mapping: address space structure to wait for |
|
* |
|
* Walk the list of under-writeback pages of the given address space |
|
* and wait for all of them. Unlike filemap_fdatawait(), this function |
|
* does not clear error status of the address space. |
|
* |
|
* Use this function if callers don't handle errors themselves. Expected |
|
* call sites are system-wide / filesystem-wide data flushers: e.g. sync(2), |
|
* fsfreeze(8) |
|
* |
|
* Return: error status of the address space. |
|
*/ |
|
int filemap_fdatawait_keep_errors(struct address_space *mapping) |
|
{ |
|
__filemap_fdatawait_range(mapping, 0, LLONG_MAX); |
|
return filemap_check_and_keep_errors(mapping); |
|
} |
|
EXPORT_SYMBOL(filemap_fdatawait_keep_errors); |
|
|
|
/* Returns true if writeback might be needed or already in progress. */ |
|
static bool mapping_needs_writeback(struct address_space *mapping) |
|
{ |
|
if (dax_mapping(mapping)) |
|
return mapping->nrexceptional; |
|
|
|
return mapping->nrpages; |
|
} |
|
|
|
/** |
|
* filemap_write_and_wait_range - write out & wait on a file range |
|
* @mapping: the address_space for the pages |
|
* @lstart: offset in bytes where the range starts |
|
* @lend: offset in bytes where the range ends (inclusive) |
|
* |
|
* Write out and wait upon file offsets lstart->lend, inclusive. |
|
* |
|
* Note that @lend is inclusive (describes the last byte to be written) so |
|
* that this function can be used to write to the very end-of-file (end = -1). |
|
* |
|
* Return: error status of the address space. |
|
*/ |
|
int filemap_write_and_wait_range(struct address_space *mapping, |
|
loff_t lstart, loff_t lend) |
|
{ |
|
int err = 0; |
|
|
|
if (mapping_needs_writeback(mapping)) { |
|
err = __filemap_fdatawrite_range(mapping, lstart, lend, |
|
WB_SYNC_ALL); |
|
/* |
|
* Even if the above returned error, the pages may be |
|
* written partially (e.g. -ENOSPC), so we wait for it. |
|
* But the -EIO is special case, it may indicate the worst |
|
* thing (e.g. bug) happened, so we avoid waiting for it. |
|
*/ |
|
if (err != -EIO) { |
|
int err2 = filemap_fdatawait_range(mapping, |
|
lstart, lend); |
|
if (!err) |
|
err = err2; |
|
} else { |
|
/* Clear any previously stored errors */ |
|
filemap_check_errors(mapping); |
|
} |
|
} else { |
|
err = filemap_check_errors(mapping); |
|
} |
|
return err; |
|
} |
|
EXPORT_SYMBOL(filemap_write_and_wait_range); |
|
|
|
void __filemap_set_wb_err(struct address_space *mapping, int err) |
|
{ |
|
errseq_t eseq = errseq_set(&mapping->wb_err, err); |
|
|
|
trace_filemap_set_wb_err(mapping, eseq); |
|
} |
|
EXPORT_SYMBOL(__filemap_set_wb_err); |
|
|
|
/** |
|
* file_check_and_advance_wb_err - report wb error (if any) that was previously |
|
* and advance wb_err to current one |
|
* @file: struct file on which the error is being reported |
|
* |
|
* When userland calls fsync (or something like nfsd does the equivalent), we |
|
* want to report any writeback errors that occurred since the last fsync (or |
|
* since the file was opened if there haven't been any). |
|
* |
|
* Grab the wb_err from the mapping. If it matches what we have in the file, |
|
* then just quickly return 0. The file is all caught up. |
|
* |
|
* If it doesn't match, then take the mapping value, set the "seen" flag in |
|
* it and try to swap it into place. If it works, or another task beat us |
|
* to it with the new value, then update the f_wb_err and return the error |
|
* portion. The error at this point must be reported via proper channels |
|
* (a'la fsync, or NFS COMMIT operation, etc.). |
|
* |
|
* While we handle mapping->wb_err with atomic operations, the f_wb_err |
|
* value is protected by the f_lock since we must ensure that it reflects |
|
* the latest value swapped in for this file descriptor. |
|
* |
|
* Return: %0 on success, negative error code otherwise. |
|
*/ |
|
int file_check_and_advance_wb_err(struct file *file) |
|
{ |
|
int err = 0; |
|
errseq_t old = READ_ONCE(file->f_wb_err); |
|
struct address_space *mapping = file->f_mapping; |
|
|
|
/* Locklessly handle the common case where nothing has changed */ |
|
if (errseq_check(&mapping->wb_err, old)) { |
|
/* Something changed, must use slow path */ |
|
spin_lock(&file->f_lock); |
|
old = file->f_wb_err; |
|
err = errseq_check_and_advance(&mapping->wb_err, |
|
&file->f_wb_err); |
|
trace_file_check_and_advance_wb_err(file, old); |
|
spin_unlock(&file->f_lock); |
|
} |
|
|
|
/* |
|
* We're mostly using this function as a drop in replacement for |
|
* filemap_check_errors. Clear AS_EIO/AS_ENOSPC to emulate the effect |
|
* that the legacy code would have had on these flags. |
|
*/ |
|
clear_bit(AS_EIO, &mapping->flags); |
|
clear_bit(AS_ENOSPC, &mapping->flags); |
|
return err; |
|
} |
|
EXPORT_SYMBOL(file_check_and_advance_wb_err); |
|
|
|
/** |
|
* file_write_and_wait_range - write out & wait on a file range |
|
* @file: file pointing to address_space with pages |
|
* @lstart: offset in bytes where the range starts |
|
* @lend: offset in bytes where the range ends (inclusive) |
|
* |
|
* Write out and wait upon file offsets lstart->lend, inclusive. |
|
* |
|
* Note that @lend is inclusive (describes the last byte to be written) so |
|
* that this function can be used to write to the very end-of-file (end = -1). |
|
* |
|
* After writing out and waiting on the data, we check and advance the |
|
* f_wb_err cursor to the latest value, and return any errors detected there. |
|
* |
|
* Return: %0 on success, negative error code otherwise. |
|
*/ |
|
int file_write_and_wait_range(struct file *file, loff_t lstart, loff_t lend) |
|
{ |
|
int err = 0, err2; |
|
struct address_space *mapping = file->f_mapping; |
|
|
|
if (mapping_needs_writeback(mapping)) { |
|
err = __filemap_fdatawrite_range(mapping, lstart, lend, |
|
WB_SYNC_ALL); |
|
/* See comment of filemap_write_and_wait() */ |
|
if (err != -EIO) |
|
__filemap_fdatawait_range(mapping, lstart, lend); |
|
} |
|
err2 = file_check_and_advance_wb_err(file); |
|
if (!err) |
|
err = err2; |
|
return err; |
|
} |
|
EXPORT_SYMBOL(file_write_and_wait_range); |
|
|
|
/** |
|
* replace_page_cache_page - replace a pagecache page with a new one |
|
* @old: page to be replaced |
|
* @new: page to replace with |
|
* |
|
* This function replaces a page in the pagecache with a new one. On |
|
* success it acquires the pagecache reference for the new page and |
|
* drops it for the old page. Both the old and new pages must be |
|
* locked. This function does not add the new page to the LRU, the |
|
* caller must do that. |
|
* |
|
* The remove + add is atomic. This function cannot fail. |
|
*/ |
|
void replace_page_cache_page(struct page *old, struct page *new) |
|
{ |
|
struct address_space *mapping = old->mapping; |
|
void (*freepage)(struct page *) = mapping->a_ops->freepage; |
|
pgoff_t offset = old->index; |
|
XA_STATE(xas, &mapping->i_pages, offset); |
|
unsigned long flags; |
|
|
|
VM_BUG_ON_PAGE(!PageLocked(old), old); |
|
VM_BUG_ON_PAGE(!PageLocked(new), new); |
|
VM_BUG_ON_PAGE(new->mapping, new); |
|
|
|
get_page(new); |
|
new->mapping = mapping; |
|
new->index = offset; |
|
|
|
mem_cgroup_migrate(old, new); |
|
|
|
xas_lock_irqsave(&xas, flags); |
|
xas_store(&xas, new); |
|
|
|
old->mapping = NULL; |
|
/* hugetlb pages do not participate in page cache accounting. */ |
|
if (!PageHuge(old)) |
|
__dec_lruvec_page_state(old, NR_FILE_PAGES); |
|
if (!PageHuge(new)) |
|
__inc_lruvec_page_state(new, NR_FILE_PAGES); |
|
if (PageSwapBacked(old)) |
|
__dec_lruvec_page_state(old, NR_SHMEM); |
|
if (PageSwapBacked(new)) |
|
__inc_lruvec_page_state(new, NR_SHMEM); |
|
xas_unlock_irqrestore(&xas, flags); |
|
if (freepage) |
|
freepage(old); |
|
put_page(old); |
|
} |
|
EXPORT_SYMBOL_GPL(replace_page_cache_page); |
|
|
|
noinline int __add_to_page_cache_locked(struct page *page, |
|
struct address_space *mapping, |
|
pgoff_t offset, gfp_t gfp, |
|
void **shadowp) |
|
{ |
|
XA_STATE(xas, &mapping->i_pages, offset); |
|
int huge = PageHuge(page); |
|
int error; |
|
bool charged = false; |
|
|
|
VM_BUG_ON_PAGE(!PageLocked(page), page); |
|
VM_BUG_ON_PAGE(PageSwapBacked(page), page); |
|
mapping_set_update(&xas, mapping); |
|
|
|
get_page(page); |
|
page->mapping = mapping; |
|
page->index = offset; |
|
|
|
if (!huge) { |
|
error = mem_cgroup_charge(page, current->mm, gfp); |
|
if (error) |
|
goto error; |
|
charged = true; |
|
} |
|
|
|
gfp &= GFP_RECLAIM_MASK; |
|
|
|
do { |
|
unsigned int order = xa_get_order(xas.xa, xas.xa_index); |
|
void *entry, *old = NULL; |
|
|
|
if (order > thp_order(page)) |
|
xas_split_alloc(&xas, xa_load(xas.xa, xas.xa_index), |
|
order, gfp); |
|
xas_lock_irq(&xas); |
|
xas_for_each_conflict(&xas, entry) { |
|
old = entry; |
|
if (!xa_is_value(entry)) { |
|
xas_set_err(&xas, -EEXIST); |
|
goto unlock; |
|
} |
|
} |
|
|
|
if (old) { |
|
if (shadowp) |
|
*shadowp = old; |
|
/* entry may have been split before we acquired lock */ |
|
order = xa_get_order(xas.xa, xas.xa_index); |
|
if (order > thp_order(page)) { |
|
xas_split(&xas, old, order); |
|
xas_reset(&xas); |
|
} |
|
} |
|
|
|
xas_store(&xas, page); |
|
if (xas_error(&xas)) |
|
goto unlock; |
|
|
|
if (old) |
|
mapping->nrexceptional--; |
|
mapping->nrpages++; |
|
|
|
/* hugetlb pages do not participate in page cache accounting */ |
|
if (!huge) |
|
__inc_lruvec_page_state(page, NR_FILE_PAGES); |
|
unlock: |
|
xas_unlock_irq(&xas); |
|
} while (xas_nomem(&xas, gfp)); |
|
|
|
if (xas_error(&xas)) { |
|
error = xas_error(&xas); |
|
if (charged) |
|
mem_cgroup_uncharge(page); |
|
goto error; |
|
} |
|
|
|
trace_mm_filemap_add_to_page_cache(page); |
|
return 0; |
|
error: |
|
page->mapping = NULL; |
|
/* Leave page->index set: truncation relies upon it */ |
|
put_page(page); |
|
return error; |
|
} |
|
ALLOW_ERROR_INJECTION(__add_to_page_cache_locked, ERRNO); |
|
|
|
/** |
|
* add_to_page_cache_locked - add a locked page to the pagecache |
|
* @page: page to add |
|
* @mapping: the page's address_space |
|
* @offset: page index |
|
* @gfp_mask: page allocation mode |
|
* |
|
* This function is used to add a page to the pagecache. It must be locked. |
|
* This function does not add the page to the LRU. The caller must do that. |
|
* |
|
* Return: %0 on success, negative error code otherwise. |
|
*/ |
|
int add_to_page_cache_locked(struct page *page, struct address_space *mapping, |
|
pgoff_t offset, gfp_t gfp_mask) |
|
{ |
|
return __add_to_page_cache_locked(page, mapping, offset, |
|
gfp_mask, NULL); |
|
} |
|
EXPORT_SYMBOL(add_to_page_cache_locked); |
|
|
|
int add_to_page_cache_lru(struct page *page, struct address_space *mapping, |
|
pgoff_t offset, gfp_t gfp_mask) |
|
{ |
|
void *shadow = NULL; |
|
int ret; |
|
|
|
__SetPageLocked(page); |
|
ret = __add_to_page_cache_locked(page, mapping, offset, |
|
gfp_mask, &shadow); |
|
if (unlikely(ret)) |
|
__ClearPageLocked(page); |
|
else { |
|
/* |
|
* The page might have been evicted from cache only |
|
* recently, in which case it should be activated like |
|
* any other repeatedly accessed page. |
|
* The exception is pages getting rewritten; evicting other |
|
* data from the working set, only to cache data that will |
|
* get overwritten with something else, is a waste of memory. |
|
*/ |
|
WARN_ON_ONCE(PageActive(page)); |
|
if (!(gfp_mask & __GFP_WRITE) && shadow) |
|
workingset_refault(page, shadow); |
|
lru_cache_add(page); |
|
} |
|
return ret; |
|
} |
|
EXPORT_SYMBOL_GPL(add_to_page_cache_lru); |
|
|
|
#ifdef CONFIG_NUMA |
|
struct page *__page_cache_alloc(gfp_t gfp) |
|
{ |
|
int n; |
|
struct page *page; |
|
|
|
if (cpuset_do_page_mem_spread()) { |
|
unsigned int cpuset_mems_cookie; |
|
do { |
|
cpuset_mems_cookie = read_mems_allowed_begin(); |
|
n = cpuset_mem_spread_node(); |
|
page = __alloc_pages_node(n, gfp, 0); |
|
} while (!page && read_mems_allowed_retry(cpuset_mems_cookie)); |
|
|
|
return page; |
|
} |
|
return alloc_pages(gfp, 0); |
|
} |
|
EXPORT_SYMBOL(__page_cache_alloc); |
|
#endif |
|
|
|
/* |
|
* In order to wait for pages to become available there must be |
|
* waitqueues associated with pages. By using a hash table of |
|
* waitqueues where the bucket discipline is to maintain all |
|
* waiters on the same queue and wake all when any of the pages |
|
* become available, and for the woken contexts to check to be |
|
* sure the appropriate page became available, this saves space |
|
* at a cost of "thundering herd" phenomena during rare hash |
|
* collisions. |
|
*/ |
|
#define PAGE_WAIT_TABLE_BITS 8 |
|
#define PAGE_WAIT_TABLE_SIZE (1 << PAGE_WAIT_TABLE_BITS) |
|
static wait_queue_head_t page_wait_table[PAGE_WAIT_TABLE_SIZE] __cacheline_aligned; |
|
|
|
static wait_queue_head_t *page_waitqueue(struct page *page) |
|
{ |
|
return &page_wait_table[hash_ptr(page, PAGE_WAIT_TABLE_BITS)]; |
|
} |
|
|
|
void __init pagecache_init(void) |
|
{ |
|
int i; |
|
|
|
for (i = 0; i < PAGE_WAIT_TABLE_SIZE; i++) |
|
init_waitqueue_head(&page_wait_table[i]); |
|
|
|
page_writeback_init(); |
|
} |
|
|
|
/* |
|
* The page wait code treats the "wait->flags" somewhat unusually, because |
|
* we have multiple different kinds of waits, not just the usual "exclusive" |
|
* one. |
|
* |
|
* We have: |
|
* |
|
* (a) no special bits set: |
|
* |
|
* We're just waiting for the bit to be released, and when a waker |
|
* calls the wakeup function, we set WQ_FLAG_WOKEN and wake it up, |
|
* and remove it from the wait queue. |
|
* |
|
* Simple and straightforward. |
|
* |
|
* (b) WQ_FLAG_EXCLUSIVE: |
|
* |
|
* The waiter is waiting to get the lock, and only one waiter should |
|
* be woken up to avoid any thundering herd behavior. We'll set the |
|
* WQ_FLAG_WOKEN bit, wake it up, and remove it from the wait queue. |
|
* |
|
* This is the traditional exclusive wait. |
|
* |
|
* (c) WQ_FLAG_EXCLUSIVE | WQ_FLAG_CUSTOM: |
|
* |
|
* The waiter is waiting to get the bit, and additionally wants the |
|
* lock to be transferred to it for fair lock behavior. If the lock |
|
* cannot be taken, we stop walking the wait queue without waking |
|
* the waiter. |
|
* |
|
* This is the "fair lock handoff" case, and in addition to setting |
|
* WQ_FLAG_WOKEN, we set WQ_FLAG_DONE to let the waiter easily see |
|
* that it now has the lock. |
|
*/ |
|
static int wake_page_function(wait_queue_entry_t *wait, unsigned mode, int sync, void *arg) |
|
{ |
|
unsigned int flags; |
|
struct wait_page_key *key = arg; |
|
struct wait_page_queue *wait_page |
|
= container_of(wait, struct wait_page_queue, wait); |
|
|
|
if (!wake_page_match(wait_page, key)) |
|
return 0; |
|
|
|
/* |
|
* If it's a lock handoff wait, we get the bit for it, and |
|
* stop walking (and do not wake it up) if we can't. |
|
*/ |
|
flags = wait->flags; |
|
if (flags & WQ_FLAG_EXCLUSIVE) { |
|
if (test_bit(key->bit_nr, &key->page->flags)) |
|
return -1; |
|
if (flags & WQ_FLAG_CUSTOM) { |
|
if (test_and_set_bit(key->bit_nr, &key->page->flags)) |
|
return -1; |
|
flags |= WQ_FLAG_DONE; |
|
} |
|
} |
|
|
|
/* |
|
* We are holding the wait-queue lock, but the waiter that |
|
* is waiting for this will be checking the flags without |
|
* any locking. |
|
* |
|
* So update the flags atomically, and wake up the waiter |
|
* afterwards to avoid any races. This store-release pairs |
|
* with the load-acquire in wait_on_page_bit_common(). |
|
*/ |
|
smp_store_release(&wait->flags, flags | WQ_FLAG_WOKEN); |
|
wake_up_state(wait->private, mode); |
|
|
|
/* |
|
* Ok, we have successfully done what we're waiting for, |
|
* and we can unconditionally remove the wait entry. |
|
* |
|
* Note that this pairs with the "finish_wait()" in the |
|
* waiter, and has to be the absolute last thing we do. |
|
* After this list_del_init(&wait->entry) the wait entry |
|
* might be de-allocated and the process might even have |
|
* exited. |
|
*/ |
|
list_del_init_careful(&wait->entry); |
|
return (flags & WQ_FLAG_EXCLUSIVE) != 0; |
|
} |
|
|
|
static void wake_up_page_bit(struct page *page, int bit_nr) |
|
{ |
|
wait_queue_head_t *q = page_waitqueue(page); |
|
struct wait_page_key key; |
|
unsigned long flags; |
|
wait_queue_entry_t bookmark; |
|
|
|
key.page = page; |
|
key.bit_nr = bit_nr; |
|
key.page_match = 0; |
|
|
|
bookmark.flags = 0; |
|
bookmark.private = NULL; |
|
bookmark.func = NULL; |
|
INIT_LIST_HEAD(&bookmark.entry); |
|
|
|
spin_lock_irqsave(&q->lock, flags); |
|
__wake_up_locked_key_bookmark(q, TASK_NORMAL, &key, &bookmark); |
|
|
|
while (bookmark.flags & WQ_FLAG_BOOKMARK) { |
|
/* |
|
* Take a breather from holding the lock, |
|
* allow pages that finish wake up asynchronously |
|
* to acquire the lock and remove themselves |
|
* from wait queue |
|
*/ |
|
spin_unlock_irqrestore(&q->lock, flags); |
|
cpu_relax(); |
|
spin_lock_irqsave(&q->lock, flags); |
|
__wake_up_locked_key_bookmark(q, TASK_NORMAL, &key, &bookmark); |
|
} |
|
|
|
/* |
|
* It is possible for other pages to have collided on the waitqueue |
|
* hash, so in that case check for a page match. That prevents a long- |
|
* term waiter |
|
* |
|
* It is still possible to miss a case here, when we woke page waiters |
|
* and removed them from the waitqueue, but there are still other |
|
* page waiters. |
|
*/ |
|
if (!waitqueue_active(q) || !key.page_match) { |
|
ClearPageWaiters(page); |
|
/* |
|
* It's possible to miss clearing Waiters here, when we woke |
|
* our page waiters, but the hashed waitqueue has waiters for |
|
* other pages on it. |
|
* |
|
* That's okay, it's a rare case. The next waker will clear it. |
|
*/ |
|
} |
|
spin_unlock_irqrestore(&q->lock, flags); |
|
} |
|
|
|
static void wake_up_page(struct page *page, int bit) |
|
{ |
|
if (!PageWaiters(page)) |
|
return; |
|
wake_up_page_bit(page, bit); |
|
} |
|
|
|
/* |
|
* A choice of three behaviors for wait_on_page_bit_common(): |
|
*/ |
|
enum behavior { |
|
EXCLUSIVE, /* Hold ref to page and take the bit when woken, like |
|
* __lock_page() waiting on then setting PG_locked. |
|
*/ |
|
SHARED, /* Hold ref to page and check the bit when woken, like |
|
* wait_on_page_writeback() waiting on PG_writeback. |
|
*/ |
|
DROP, /* Drop ref to page before wait, no check when woken, |
|
* like put_and_wait_on_page_locked() on PG_locked. |
|
*/ |
|
}; |
|
|
|
/* |
|
* Attempt to check (or get) the page bit, and mark us done |
|
* if successful. |
|
*/ |
|
static inline bool trylock_page_bit_common(struct page *page, int bit_nr, |
|
struct wait_queue_entry *wait) |
|
{ |
|
if (wait->flags & WQ_FLAG_EXCLUSIVE) { |
|
if (test_and_set_bit(bit_nr, &page->flags)) |
|
return false; |
|
} else if (test_bit(bit_nr, &page->flags)) |
|
return false; |
|
|
|
wait->flags |= WQ_FLAG_WOKEN | WQ_FLAG_DONE; |
|
return true; |
|
} |
|
|
|
/* How many times do we accept lock stealing from under a waiter? */ |
|
int sysctl_page_lock_unfairness = 5; |
|
|
|
static inline int wait_on_page_bit_common(wait_queue_head_t *q, |
|
struct page *page, int bit_nr, int state, enum behavior behavior) |
|
{ |
|
int unfairness = sysctl_page_lock_unfairness; |
|
struct wait_page_queue wait_page; |
|
wait_queue_entry_t *wait = &wait_page.wait; |
|
bool thrashing = false; |
|
bool delayacct = false; |
|
unsigned long pflags; |
|
|
|
if (bit_nr == PG_locked && |
|
!PageUptodate(page) && PageWorkingset(page)) { |
|
if (!PageSwapBacked(page)) { |
|
delayacct_thrashing_start(); |
|
delayacct = true; |
|
} |
|
psi_memstall_enter(&pflags); |
|
thrashing = true; |
|
} |
|
|
|
init_wait(wait); |
|
wait->func = wake_page_function; |
|
wait_page.page = page; |
|
wait_page.bit_nr = bit_nr; |
|
|
|
repeat: |
|
wait->flags = 0; |
|
if (behavior == EXCLUSIVE) { |
|
wait->flags = WQ_FLAG_EXCLUSIVE; |
|
if (--unfairness < 0) |
|
wait->flags |= WQ_FLAG_CUSTOM; |
|
} |
|
|
|
/* |
|
* Do one last check whether we can get the |
|
* page bit synchronously. |
|
* |
|
* Do the SetPageWaiters() marking before that |
|
* to let any waker we _just_ missed know they |
|
* need to wake us up (otherwise they'll never |
|
* even go to the slow case that looks at the |
|
* page queue), and add ourselves to the wait |
|
* queue if we need to sleep. |
|
* |
|
* This part needs to be done under the queue |
|
* lock to avoid races. |
|
*/ |
|
spin_lock_irq(&q->lock); |
|
SetPageWaiters(page); |
|
if (!trylock_page_bit_common(page, bit_nr, wait)) |
|
__add_wait_queue_entry_tail(q, wait); |
|
spin_unlock_irq(&q->lock); |
|
|
|
/* |
|
* From now on, all the logic will be based on |
|
* the WQ_FLAG_WOKEN and WQ_FLAG_DONE flag, to |
|
* see whether the page bit testing has already |
|
* been done by the wake function. |
|
* |
|
* We can drop our reference to the page. |
|
*/ |
|
if (behavior == DROP) |
|
put_page(page); |
|
|
|
/* |
|
* Note that until the "finish_wait()", or until |
|
* we see the WQ_FLAG_WOKEN flag, we need to |
|
* be very careful with the 'wait->flags', because |
|
* we may race with a waker that sets them. |
|
*/ |
|
for (;;) { |
|
unsigned int flags; |
|
|
|
set_current_state(state); |
|
|
|
/* Loop until we've been woken or interrupted */ |
|
flags = smp_load_acquire(&wait->flags); |
|
if (!(flags & WQ_FLAG_WOKEN)) { |
|
if (signal_pending_state(state, current)) |
|
break; |
|
|
|
io_schedule(); |
|
continue; |
|
} |
|
|
|
/* If we were non-exclusive, we're done */ |
|
if (behavior != EXCLUSIVE) |
|
break; |
|
|
|
/* If the waker got the lock for us, we're done */ |
|
if (flags & WQ_FLAG_DONE) |
|
break; |
|
|
|
/* |
|
* Otherwise, if we're getting the lock, we need to |
|
* try to get it ourselves. |
|
* |
|
* And if that fails, we'll have to retry this all. |
|
*/ |
|
if (unlikely(test_and_set_bit(bit_nr, &page->flags))) |
|
goto repeat; |
|
|
|
wait->flags |= WQ_FLAG_DONE; |
|
break; |
|
} |
|
|
|
/* |
|
* If a signal happened, this 'finish_wait()' may remove the last |
|
* waiter from the wait-queues, but the PageWaiters bit will remain |
|
* set. That's ok. The next wakeup will take care of it, and trying |
|
* to do it here would be difficult and prone to races. |
|
*/ |
|
finish_wait(q, wait); |
|
|
|
if (thrashing) { |
|
if (delayacct) |
|
delayacct_thrashing_end(); |
|
psi_memstall_leave(&pflags); |
|
} |
|
|
|
/* |
|
* NOTE! The wait->flags weren't stable until we've done the |
|
* 'finish_wait()', and we could have exited the loop above due |
|
* to a signal, and had a wakeup event happen after the signal |
|
* test but before the 'finish_wait()'. |
|
* |
|
* So only after the finish_wait() can we reliably determine |
|
* if we got woken up or not, so we can now figure out the final |
|
* return value based on that state without races. |
|
* |
|
* Also note that WQ_FLAG_WOKEN is sufficient for a non-exclusive |
|
* waiter, but an exclusive one requires WQ_FLAG_DONE. |
|
*/ |
|
if (behavior == EXCLUSIVE) |
|
return wait->flags & WQ_FLAG_DONE ? 0 : -EINTR; |
|
|
|
return wait->flags & WQ_FLAG_WOKEN ? 0 : -EINTR; |
|
} |
|
|
|
void wait_on_page_bit(struct page *page, int bit_nr) |
|
{ |
|
wait_queue_head_t *q = page_waitqueue(page); |
|
wait_on_page_bit_common(q, page, bit_nr, TASK_UNINTERRUPTIBLE, SHARED); |
|
} |
|
EXPORT_SYMBOL(wait_on_page_bit); |
|
|
|
int wait_on_page_bit_killable(struct page *page, int bit_nr) |
|
{ |
|
wait_queue_head_t *q = page_waitqueue(page); |
|
return wait_on_page_bit_common(q, page, bit_nr, TASK_KILLABLE, SHARED); |
|
} |
|
EXPORT_SYMBOL(wait_on_page_bit_killable); |
|
|
|
/** |
|
* put_and_wait_on_page_locked - Drop a reference and wait for it to be unlocked |
|
* @page: The page to wait for. |
|
* @state: The sleep state (TASK_KILLABLE, TASK_UNINTERRUPTIBLE, etc). |
|
* |
|
* The caller should hold a reference on @page. They expect the page to |
|
* become unlocked relatively soon, but do not wish to hold up migration |
|
* (for example) by holding the reference while waiting for the page to |
|
* come unlocked. After this function returns, the caller should not |
|
* dereference @page. |
|
* |
|
* Return: 0 if the page was unlocked or -EINTR if interrupted by a signal. |
|
*/ |
|
int put_and_wait_on_page_locked(struct page *page, int state) |
|
{ |
|
wait_queue_head_t *q; |
|
|
|
page = compound_head(page); |
|
q = page_waitqueue(page); |
|
return wait_on_page_bit_common(q, page, PG_locked, state, DROP); |
|
} |
|
|
|
/** |
|
* add_page_wait_queue - Add an arbitrary waiter to a page's wait queue |
|
* @page: Page defining the wait queue of interest |
|
* @waiter: Waiter to add to the queue |
|
* |
|
* Add an arbitrary @waiter to the wait queue for the nominated @page. |
|
*/ |
|
void add_page_wait_queue(struct page *page, wait_queue_entry_t *waiter) |
|
{ |
|
wait_queue_head_t *q = page_waitqueue(page); |
|
unsigned long flags; |
|
|
|
spin_lock_irqsave(&q->lock, flags); |
|
__add_wait_queue_entry_tail(q, waiter); |
|
SetPageWaiters(page); |
|
spin_unlock_irqrestore(&q->lock, flags); |
|
} |
|
EXPORT_SYMBOL_GPL(add_page_wait_queue); |
|
|
|
#ifndef clear_bit_unlock_is_negative_byte |
|
|
|
/* |
|
* PG_waiters is the high bit in the same byte as PG_lock. |
|
* |
|
* On x86 (and on many other architectures), we can clear PG_lock and |
|
* test the sign bit at the same time. But if the architecture does |
|
* not support that special operation, we just do this all by hand |
|
* instead. |
|
* |
|
* The read of PG_waiters has to be after (or concurrently with) PG_locked |
|
* being cleared, but a memory barrier should be unnecessary since it is |
|
* in the same byte as PG_locked. |
|
*/ |
|
static inline bool clear_bit_unlock_is_negative_byte(long nr, volatile void *mem) |
|
{ |
|
clear_bit_unlock(nr, mem); |
|
/* smp_mb__after_atomic(); */ |
|
return test_bit(PG_waiters, mem); |
|
} |
|
|
|
#endif |
|
|
|
/** |
|
* unlock_page - unlock a locked page |
|
* @page: the page |
|
* |
|
* Unlocks the page and wakes up sleepers in wait_on_page_locked(). |
|
* Also wakes sleepers in wait_on_page_writeback() because the wakeup |
|
* mechanism between PageLocked pages and PageWriteback pages is shared. |
|
* But that's OK - sleepers in wait_on_page_writeback() just go back to sleep. |
|
* |
|
* Note that this depends on PG_waiters being the sign bit in the byte |
|
* that contains PG_locked - thus the BUILD_BUG_ON(). That allows us to |
|
* clear the PG_locked bit and test PG_waiters at the same time fairly |
|
* portably (architectures that do LL/SC can test any bit, while x86 can |
|
* test the sign bit). |
|
*/ |
|
void unlock_page(struct page *page) |
|
{ |
|
BUILD_BUG_ON(PG_waiters != 7); |
|
page = compound_head(page); |
|
VM_BUG_ON_PAGE(!PageLocked(page), page); |
|
if (clear_bit_unlock_is_negative_byte(PG_locked, &page->flags)) |
|
wake_up_page_bit(page, PG_locked); |
|
} |
|
EXPORT_SYMBOL(unlock_page); |
|
|
|
/** |
|
* end_page_writeback - end writeback against a page |
|
* @page: the page |
|
*/ |
|
void end_page_writeback(struct page *page) |
|
{ |
|
/* |
|
* TestClearPageReclaim could be used here but it is an atomic |
|
* operation and overkill in this particular case. Failing to |
|
* shuffle a page marked for immediate reclaim is too mild to |
|
* justify taking an atomic operation penalty at the end of |
|
* ever page writeback. |
|
*/ |
|
if (PageReclaim(page)) { |
|
ClearPageReclaim(page); |
|
rotate_reclaimable_page(page); |
|
} |
|
|
|
/* |
|
* Writeback does not hold a page reference of its own, relying |
|
* on truncation to wait for the clearing of PG_writeback. |
|
* But here we must make sure that the page is not freed and |
|
* reused before the wake_up_page(). |
|
*/ |
|
get_page(page); |
|
if (!test_clear_page_writeback(page)) |
|
BUG(); |
|
|
|
smp_mb__after_atomic(); |
|
wake_up_page(page, PG_writeback); |
|
put_page(page); |
|
} |
|
EXPORT_SYMBOL(end_page_writeback); |
|
|
|
/* |
|
* After completing I/O on a page, call this routine to update the page |
|
* flags appropriately |
|
*/ |
|
void page_endio(struct page *page, bool is_write, int err) |
|
{ |
|
if (!is_write) { |
|
if (!err) { |
|
SetPageUptodate(page); |
|
} else { |
|
ClearPageUptodate(page); |
|
SetPageError(page); |
|
} |
|
unlock_page(page); |
|
} else { |
|
if (err) { |
|
struct address_space *mapping; |
|
|
|
SetPageError(page); |
|
mapping = page_mapping(page); |
|
if (mapping) |
|
mapping_set_error(mapping, err); |
|
} |
|
end_page_writeback(page); |
|
} |
|
} |
|
EXPORT_SYMBOL_GPL(page_endio); |
|
|
|
/** |
|
* __lock_page - get a lock on the page, assuming we need to sleep to get it |
|
* @__page: the page to lock |
|
*/ |
|
void __lock_page(struct page *__page) |
|
{ |
|
struct page *page = compound_head(__page); |
|
wait_queue_head_t *q = page_waitqueue(page); |
|
wait_on_page_bit_common(q, page, PG_locked, TASK_UNINTERRUPTIBLE, |
|
EXCLUSIVE); |
|
} |
|
EXPORT_SYMBOL(__lock_page); |
|
|
|
int __lock_page_killable(struct page *__page) |
|
{ |
|
struct page *page = compound_head(__page); |
|
wait_queue_head_t *q = page_waitqueue(page); |
|
return wait_on_page_bit_common(q, page, PG_locked, TASK_KILLABLE, |
|
EXCLUSIVE); |
|
} |
|
EXPORT_SYMBOL_GPL(__lock_page_killable); |
|
|
|
int __lock_page_async(struct page *page, struct wait_page_queue *wait) |
|
{ |
|
struct wait_queue_head *q = page_waitqueue(page); |
|
int ret = 0; |
|
|
|
wait->page = page; |
|
wait->bit_nr = PG_locked; |
|
|
|
spin_lock_irq(&q->lock); |
|
__add_wait_queue_entry_tail(q, &wait->wait); |
|
SetPageWaiters(page); |
|
ret = !trylock_page(page); |
|
/* |
|
* If we were successful now, we know we're still on the |
|
* waitqueue as we're still under the lock. This means it's |
|
* safe to remove and return success, we know the callback |
|
* isn't going to trigger. |
|
*/ |
|
if (!ret) |
|
__remove_wait_queue(q, &wait->wait); |
|
else |
|
ret = -EIOCBQUEUED; |
|
spin_unlock_irq(&q->lock); |
|
return ret; |
|
} |
|
|
|
/* |
|
* Return values: |
|
* 1 - page is locked; mmap_lock is still held. |
|
* 0 - page is not locked. |
|
* mmap_lock has been released (mmap_read_unlock(), unless flags had both |
|
* FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_RETRY_NOWAIT set, in |
|
* which case mmap_lock is still held. |
|
* |
|
* If neither ALLOW_RETRY nor KILLABLE are set, will always return 1 |
|
* with the page locked and the mmap_lock unperturbed. |
|
*/ |
|
int __lock_page_or_retry(struct page *page, struct mm_struct *mm, |
|
unsigned int flags) |
|
{ |
|
if (fault_flag_allow_retry_first(flags)) { |
|
/* |
|
* CAUTION! In this case, mmap_lock is not released |
|
* even though return 0. |
|
*/ |
|
if (flags & FAULT_FLAG_RETRY_NOWAIT) |
|
return 0; |
|
|
|
mmap_read_unlock(mm); |
|
if (flags & FAULT_FLAG_KILLABLE) |
|
wait_on_page_locked_killable(page); |
|
else |
|
wait_on_page_locked(page); |
|
return 0; |
|
} |
|
if (flags & FAULT_FLAG_KILLABLE) { |
|
int ret; |
|
|
|
ret = __lock_page_killable(page); |
|
if (ret) { |
|
mmap_read_unlock(mm); |
|
return 0; |
|
} |
|
} else { |
|
__lock_page(page); |
|
} |
|
return 1; |
|
|
|
} |
|
|
|
/** |
|
* page_cache_next_miss() - Find the next gap in the page cache. |
|
* @mapping: Mapping. |
|
* @index: Index. |
|
* @max_scan: Maximum range to search. |
|
* |
|
* Search the range [index, min(index + max_scan - 1, ULONG_MAX)] for the |
|
* gap with the lowest index. |
|
* |
|
* This function may be called under the rcu_read_lock. However, this will |
|
* not atomically search a snapshot of the cache at a single point in time. |
|
* For example, if a gap is created at index 5, then subsequently a gap is |
|
* created at index 10, page_cache_next_miss covering both indices may |
|
* return 10 if called under the rcu_read_lock. |
|
* |
|
* Return: The index of the gap if found, otherwise an index outside the |
|
* range specified (in which case 'return - index >= max_scan' will be true). |
|
* In the rare case of index wrap-around, 0 will be returned. |
|
*/ |
|
pgoff_t page_cache_next_miss(struct address_space *mapping, |
|
pgoff_t index, unsigned long max_scan) |
|
{ |
|
XA_STATE(xas, &mapping->i_pages, index); |
|
|
|
while (max_scan--) { |
|
void *entry = xas_next(&xas); |
|
if (!entry || xa_is_value(entry)) |
|
break; |
|
if (xas.xa_index == 0) |
|
break; |
|
} |
|
|
|
return xas.xa_index; |
|
} |
|
EXPORT_SYMBOL(page_cache_next_miss); |
|
|
|
/** |
|
* page_cache_prev_miss() - Find the previous gap in the page cache. |
|
* @mapping: Mapping. |
|
* @index: Index. |
|
* @max_scan: Maximum range to search. |
|
* |
|
* Search the range [max(index - max_scan + 1, 0), index] for the |
|
* gap with the highest index. |
|
* |
|
* This function may be called under the rcu_read_lock. However, this will |
|
* not atomically search a snapshot of the cache at a single point in time. |
|
* For example, if a gap is created at index 10, then subsequently a gap is |
|
* created at index 5, page_cache_prev_miss() covering both indices may |
|
* return 5 if called under the rcu_read_lock. |
|
* |
|
* Return: The index of the gap if found, otherwise an index outside the |
|
* range specified (in which case 'index - return >= max_scan' will be true). |
|
* In the rare case of wrap-around, ULONG_MAX will be returned. |
|
*/ |
|
pgoff_t page_cache_prev_miss(struct address_space *mapping, |
|
pgoff_t index, unsigned long max_scan) |
|
{ |
|
XA_STATE(xas, &mapping->i_pages, index); |
|
|
|
while (max_scan--) { |
|
void *entry = xas_prev(&xas); |
|
if (!entry || xa_is_value(entry)) |
|
break; |
|
if (xas.xa_index == ULONG_MAX) |
|
break; |
|
} |
|
|
|
return xas.xa_index; |
|
} |
|
EXPORT_SYMBOL(page_cache_prev_miss); |
|
|
|
/* |
|
* mapping_get_entry - Get a page cache entry. |
|
* @mapping: the address_space to search |
|
* @index: The page cache index. |
|
* |
|
* Looks up the page cache slot at @mapping & @offset. If there is a |
|
* page cache page, the head page is returned with an increased refcount. |
|
* |
|
* If the slot holds a shadow entry of a previously evicted page, or a |
|
* swap entry from shmem/tmpfs, it is returned. |
|
* |
|
* Return: The head page or shadow entry, %NULL if nothing is found. |
|
*/ |
|
static struct page *mapping_get_entry(struct address_space *mapping, |
|
pgoff_t index) |
|
{ |
|
XA_STATE(xas, &mapping->i_pages, index); |
|
struct page *page; |
|
|
|
rcu_read_lock(); |
|
repeat: |
|
xas_reset(&xas); |
|
page = xas_load(&xas); |
|
if (xas_retry(&xas, page)) |
|
goto repeat; |
|
/* |
|
* A shadow entry of a recently evicted page, or a swap entry from |
|
* shmem/tmpfs. Return it without attempting to raise page count. |
|
*/ |
|
if (!page || xa_is_value(page)) |
|
goto out; |
|
|
|
if (!page_cache_get_speculative(page)) |
|
goto repeat; |
|
|
|
/* |
|
* Has the page moved or been split? |
|
* This is part of the lockless pagecache protocol. See |
|
* include/linux/pagemap.h for details. |
|
*/ |
|
if (unlikely(page != xas_reload(&xas))) { |
|
put_page(page); |
|
goto repeat; |
|
} |
|
out: |
|
rcu_read_unlock(); |
|
|
|
return page; |
|
} |
|
|
|
/** |
|
* pagecache_get_page - Find and get a reference to a page. |
|
* @mapping: The address_space to search. |
|
* @index: The page index. |
|
* @fgp_flags: %FGP flags modify how the page is returned. |
|
* @gfp_mask: Memory allocation flags to use if %FGP_CREAT is specified. |
|
* |
|
* Looks up the page cache entry at @mapping & @index. |
|
* |
|
* @fgp_flags can be zero or more of these flags: |
|
* |
|
* * %FGP_ACCESSED - The page will be marked accessed. |
|
* * %FGP_LOCK - The page is returned locked. |
|
* * %FGP_HEAD - If the page is present and a THP, return the head page |
|
* rather than the exact page specified by the index. |
|
* * %FGP_ENTRY - If there is a shadow / swap / DAX entry, return it |
|
* instead of allocating a new page to replace it. |
|
* * %FGP_CREAT - If no page is present then a new page is allocated using |
|
* @gfp_mask and added to the page cache and the VM's LRU list. |
|
* The page is returned locked and with an increased refcount. |
|
* * %FGP_FOR_MMAP - The caller wants to do its own locking dance if the |
|
* page is already in cache. If the page was allocated, unlock it before |
|
* returning so the caller can do the same dance. |
|
* * %FGP_WRITE - The page will be written |
|
* * %FGP_NOFS - __GFP_FS will get cleared in gfp mask |
|
* * %FGP_NOWAIT - Don't get blocked by page lock |
|
* |
|
* If %FGP_LOCK or %FGP_CREAT are specified then the function may sleep even |
|
* if the %GFP flags specified for %FGP_CREAT are atomic. |
|
* |
|
* If there is a page cache page, it is returned with an increased refcount. |
|
* |
|
* Return: The found page or %NULL otherwise. |
|
*/ |
|
struct page *pagecache_get_page(struct address_space *mapping, pgoff_t index, |
|
int fgp_flags, gfp_t gfp_mask) |
|
{ |
|
struct page *page; |
|
|
|
repeat: |
|
page = mapping_get_entry(mapping, index); |
|
if (xa_is_value(page)) { |
|
if (fgp_flags & FGP_ENTRY) |
|
return page; |
|
page = NULL; |
|
} |
|
if (!page) |
|
goto no_page; |
|
|
|
if (fgp_flags & FGP_LOCK) { |
|
if (fgp_flags & FGP_NOWAIT) { |
|
if (!trylock_page(page)) { |
|
put_page(page); |
|
return NULL; |
|
} |
|
} else { |
|
lock_page(page); |
|
} |
|
|
|
/* Has the page been truncated? */ |
|
if (unlikely(page->mapping != mapping)) { |
|
unlock_page(page); |
|
put_page(page); |
|
goto repeat; |
|
} |
|
VM_BUG_ON_PAGE(!thp_contains(page, index), page); |
|
} |
|
|
|
if (fgp_flags & FGP_ACCESSED) |
|
mark_page_accessed(page); |
|
else if (fgp_flags & FGP_WRITE) { |
|
/* Clear idle flag for buffer write */ |
|
if (page_is_idle(page)) |
|
clear_page_idle(page); |
|
} |
|
if (!(fgp_flags & FGP_HEAD)) |
|
page = find_subpage(page, index); |
|
|
|
no_page: |
|
if (!page && (fgp_flags & FGP_CREAT)) { |
|
int err; |
|
if ((fgp_flags & FGP_WRITE) && mapping_can_writeback(mapping)) |
|
gfp_mask |= __GFP_WRITE; |
|
if (fgp_flags & FGP_NOFS) |
|
gfp_mask &= ~__GFP_FS; |
|
|
|
page = __page_cache_alloc(gfp_mask); |
|
if (!page) |
|
return NULL; |
|
|
|
if (WARN_ON_ONCE(!(fgp_flags & (FGP_LOCK | FGP_FOR_MMAP)))) |
|
fgp_flags |= FGP_LOCK; |
|
|
|
/* Init accessed so avoid atomic mark_page_accessed later */ |
|
if (fgp_flags & FGP_ACCESSED) |
|
__SetPageReferenced(page); |
|
|
|
err = add_to_page_cache_lru(page, mapping, index, gfp_mask); |
|
if (unlikely(err)) { |
|
put_page(page); |
|
page = NULL; |
|
if (err == -EEXIST) |
|
goto repeat; |
|
} |
|
|
|
/* |
|
* add_to_page_cache_lru locks the page, and for mmap we expect |
|
* an unlocked page. |
|
*/ |
|
if (page && (fgp_flags & FGP_FOR_MMAP)) |
|
unlock_page(page); |
|
} |
|
|
|
return page; |
|
} |
|
EXPORT_SYMBOL(pagecache_get_page); |
|
|
|
static inline struct page *find_get_entry(struct xa_state *xas, pgoff_t max, |
|
xa_mark_t mark) |
|
{ |
|
struct page *page; |
|
|
|
retry: |
|
if (mark == XA_PRESENT) |
|
page = xas_find(xas, max); |
|
else |
|
page = xas_find_marked(xas, max, mark); |
|
|
|
if (xas_retry(xas, page)) |
|
goto retry; |
|
/* |
|
* A shadow entry of a recently evicted page, a swap |
|
* entry from shmem/tmpfs or a DAX entry. Return it |
|
* without attempting to raise page count. |
|
*/ |
|
if (!page || xa_is_value(page)) |
|
return page; |
|
|
|
if (!page_cache_get_speculative(page)) |
|
goto reset; |
|
|
|
/* Has the page moved or been split? */ |
|
if (unlikely(page != xas_reload(xas))) { |
|
put_page(page); |
|
goto reset; |
|
} |
|
|
|
return page; |
|
reset: |
|
xas_reset(xas); |
|
goto retry; |
|
} |
|
|
|
/** |
|
* find_get_entries - gang pagecache lookup |
|
* @mapping: The address_space to search |
|
* @start: The starting page cache index |
|
* @end: The final page index (inclusive). |
|
* @pvec: Where the resulting entries are placed. |
|
* @indices: The cache indices corresponding to the entries in @entries |
|
* |
|
* find_get_entries() will search for and return a batch of entries in |
|
* the mapping. The entries are placed in @pvec. find_get_entries() |
|
* takes a reference on any actual pages it returns. |
|
* |
|
* The search returns a group of mapping-contiguous page cache entries |
|
* with ascending indexes. There may be holes in the indices due to |
|
* not-present pages. |
|
* |
|
* Any shadow entries of evicted pages, or swap entries from |
|
* shmem/tmpfs, are included in the returned array. |
|
* |
|
* If it finds a Transparent Huge Page, head or tail, find_get_entries() |
|
* stops at that page: the caller is likely to have a better way to handle |
|
* the compound page as a whole, and then skip its extent, than repeatedly |
|
* calling find_get_entries() to return all its tails. |
|
* |
|
* Return: the number of pages and shadow entries which were found. |
|
*/ |
|
unsigned find_get_entries(struct address_space *mapping, pgoff_t start, |
|
pgoff_t end, struct pagevec *pvec, pgoff_t *indices) |
|
{ |
|
XA_STATE(xas, &mapping->i_pages, start); |
|
struct page *page; |
|
unsigned int ret = 0; |
|
unsigned nr_entries = PAGEVEC_SIZE; |
|
|
|
rcu_read_lock(); |
|
while ((page = find_get_entry(&xas, end, XA_PRESENT))) { |
|
/* |
|
* Terminate early on finding a THP, to allow the caller to |
|
* handle it all at once; but continue if this is hugetlbfs. |
|
*/ |
|
if (!xa_is_value(page) && PageTransHuge(page) && |
|
!PageHuge(page)) { |
|
page = find_subpage(page, xas.xa_index); |
|
nr_entries = ret + 1; |
|
} |
|
|
|
indices[ret] = xas.xa_index; |
|
pvec->pages[ret] = page; |
|
if (++ret == nr_entries) |
|
break; |
|
} |
|
rcu_read_unlock(); |
|
|
|
pvec->nr = ret; |
|
return ret; |
|
} |
|
|
|
/** |
|
* find_lock_entries - Find a batch of pagecache entries. |
|
* @mapping: The address_space to search. |
|
* @start: The starting page cache index. |
|
* @end: The final page index (inclusive). |
|
* @pvec: Where the resulting entries are placed. |
|
* @indices: The cache indices of the entries in @pvec. |
|
* |
|
* find_lock_entries() will return a batch of entries from @mapping. |
|
* Swap, shadow and DAX entries are included. Pages are returned |
|
* locked and with an incremented refcount. Pages which are locked by |
|
* somebody else or under writeback are skipped. Only the head page of |
|
* a THP is returned. Pages which are partially outside the range are |
|
* not returned. |
|
* |
|
* The entries have ascending indexes. The indices may not be consecutive |
|
* due to not-present entries, THP pages, pages which could not be locked |
|
* or pages under writeback. |
|
* |
|
* Return: The number of entries which were found. |
|
*/ |
|
unsigned find_lock_entries(struct address_space *mapping, pgoff_t start, |
|
pgoff_t end, struct pagevec *pvec, pgoff_t *indices) |
|
{ |
|
XA_STATE(xas, &mapping->i_pages, start); |
|
struct page *page; |
|
|
|
rcu_read_lock(); |
|
while ((page = find_get_entry(&xas, end, XA_PRESENT))) { |
|
if (!xa_is_value(page)) { |
|
if (page->index < start) |
|
goto put; |
|
VM_BUG_ON_PAGE(page->index != xas.xa_index, page); |
|
if (page->index + thp_nr_pages(page) - 1 > end) |
|
goto put; |
|
if (!trylock_page(page)) |
|
goto put; |
|
if (page->mapping != mapping || PageWriteback(page)) |
|
goto unlock; |
|
VM_BUG_ON_PAGE(!thp_contains(page, xas.xa_index), |
|
page); |
|
} |
|
indices[pvec->nr] = xas.xa_index; |
|
if (!pagevec_add(pvec, page)) |
|
break; |
|
goto next; |
|
unlock: |
|
unlock_page(page); |
|
put: |
|
put_page(page); |
|
next: |
|
if (!xa_is_value(page) && PageTransHuge(page)) { |
|
unsigned int nr_pages = thp_nr_pages(page); |
|
|
|
/* Final THP may cross MAX_LFS_FILESIZE on 32-bit */ |
|
xas_set(&xas, page->index + nr_pages); |
|
if (xas.xa_index < nr_pages) |
|
break; |
|
} |
|
} |
|
rcu_read_unlock(); |
|
|
|
return pagevec_count(pvec); |
|
} |
|
|
|
/** |
|
* find_get_pages_range - gang pagecache lookup |
|
* @mapping: The address_space to search |
|
* @start: The starting page index |
|
* @end: The final page index (inclusive) |
|
* @nr_pages: The maximum number of pages |
|
* @pages: Where the resulting pages are placed |
|
* |
|
* find_get_pages_range() will search for and return a group of up to @nr_pages |
|
* pages in the mapping starting at index @start and up to index @end |
|
* (inclusive). The pages are placed at @pages. find_get_pages_range() takes |
|
* a reference against the returned pages. |
|
* |
|
* The search returns a group of mapping-contiguous pages with ascending |
|
* indexes. There may be holes in the indices due to not-present pages. |
|
* We also update @start to index the next page for the traversal. |
|
* |
|
* Return: the number of pages which were found. If this number is |
|
* smaller than @nr_pages, the end of specified range has been |
|
* reached. |
|
*/ |
|
unsigned find_get_pages_range(struct address_space *mapping, pgoff_t *start, |
|
pgoff_t end, unsigned int nr_pages, |
|
struct page **pages) |
|
{ |
|
XA_STATE(xas, &mapping->i_pages, *start); |
|
struct page *page; |
|
unsigned ret = 0; |
|
|
|
if (unlikely(!nr_pages)) |
|
return 0; |
|
|
|
rcu_read_lock(); |
|
while ((page = find_get_entry(&xas, end, XA_PRESENT))) { |
|
/* Skip over shadow, swap and DAX entries */ |
|
if (xa_is_value(page)) |
|
continue; |
|
|
|
pages[ret] = find_subpage(page, xas.xa_index); |
|
if (++ret == nr_pages) { |
|
*start = xas.xa_index + 1; |
|
goto out; |
|
} |
|
} |
|
|
|
/* |
|
* We come here when there is no page beyond @end. We take care to not |
|
* overflow the index @start as it confuses some of the callers. This |
|
* breaks the iteration when there is a page at index -1 but that is |
|
* already broken anyway. |
|
*/ |
|
if (end == (pgoff_t)-1) |
|
*start = (pgoff_t)-1; |
|
else |
|
*start = end + 1; |
|
out: |
|
rcu_read_unlock(); |
|
|
|
return ret; |
|
} |
|
|
|
/** |
|
* find_get_pages_contig - gang contiguous pagecache lookup |
|
* @mapping: The address_space to search |
|
* @index: The starting page index |
|
* @nr_pages: The maximum number of pages |
|
* @pages: Where the resulting pages are placed |
|
* |
|
* find_get_pages_contig() works exactly like find_get_pages(), except |
|
* that the returned number of pages are guaranteed to be contiguous. |
|
* |
|
* Return: the number of pages which were found. |
|
*/ |
|
unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index, |
|
unsigned int nr_pages, struct page **pages) |
|
{ |
|
XA_STATE(xas, &mapping->i_pages, index); |
|
struct page *page; |
|
unsigned int ret = 0; |
|
|
|
if (unlikely(!nr_pages)) |
|
return 0; |
|
|
|
rcu_read_lock(); |
|
for (page = xas_load(&xas); page; page = xas_next(&xas)) { |
|
if (xas_retry(&xas, page)) |
|
continue; |
|
/* |
|
* If the entry has been swapped out, we can stop looking. |
|
* No current caller is looking for DAX entries. |
|
*/ |
|
if (xa_is_value(page)) |
|
break; |
|
|
|
if (!page_cache_get_speculative(page)) |
|
goto retry; |
|
|
|
/* Has the page moved or been split? */ |
|
if (unlikely(page != xas_reload(&xas))) |
|
goto put_page; |
|
|
|
pages[ret] = find_subpage(page, xas.xa_index); |
|
if (++ret == nr_pages) |
|
break; |
|
continue; |
|
put_page: |
|
put_page(page); |
|
retry: |
|
xas_reset(&xas); |
|
} |
|
rcu_read_unlock(); |
|
return ret; |
|
} |
|
EXPORT_SYMBOL(find_get_pages_contig); |
|
|
|
/** |
|
* find_get_pages_range_tag - Find and return head pages matching @tag. |
|
* @mapping: the address_space to search |
|
* @index: the starting page index |
|
* @end: The final page index (inclusive) |
|
* @tag: the tag index |
|
* @nr_pages: the maximum number of pages |
|
* @pages: where the resulting pages are placed |
|
* |
|
* Like find_get_pages(), except we only return head pages which are tagged |
|
* with @tag. @index is updated to the index immediately after the last |
|
* page we return, ready for the next iteration. |
|
* |
|
* Return: the number of pages which were found. |
|
*/ |
|
unsigned find_get_pages_range_tag(struct address_space *mapping, pgoff_t *index, |
|
pgoff_t end, xa_mark_t tag, unsigned int nr_pages, |
|
struct page **pages) |
|
{ |
|
XA_STATE(xas, &mapping->i_pages, *index); |
|
struct page *page; |
|
unsigned ret = 0; |
|
|
|
if (unlikely(!nr_pages)) |
|
return 0; |
|
|
|
rcu_read_lock(); |
|
while ((page = find_get_entry(&xas, end, tag))) { |
|
/* |
|
* Shadow entries should never be tagged, but this iteration |
|
* is lockless so there is a window for page reclaim to evict |
|
* a page we saw tagged. Skip over it. |
|
*/ |
|
if (xa_is_value(page)) |
|
continue; |
|
|
|
pages[ret] = page; |
|
if (++ret == nr_pages) { |
|
*index = page->index + thp_nr_pages(page); |
|
goto out; |
|
} |
|
} |
|
|
|
/* |
|
* We come here when we got to @end. We take care to not overflow the |
|
* index @index as it confuses some of the callers. This breaks the |
|
* iteration when there is a page at index -1 but that is already |
|
* broken anyway. |
|
*/ |
|
if (end == (pgoff_t)-1) |
|
*index = (pgoff_t)-1; |
|
else |
|
*index = end + 1; |
|
out: |
|
rcu_read_unlock(); |
|
|
|
return ret; |
|
} |
|
EXPORT_SYMBOL(find_get_pages_range_tag); |
|
|
|
/* |
|
* CD/DVDs are error prone. When a medium error occurs, the driver may fail |
|
* a _large_ part of the i/o request. Imagine the worst scenario: |
|
* |
|
* ---R__________________________________________B__________ |
|
* ^ reading here ^ bad block(assume 4k) |
|
* |
|
* read(R) => miss => readahead(R...B) => media error => frustrating retries |
|
* => failing the whole request => read(R) => read(R+1) => |
|
* readahead(R+1...B+1) => bang => read(R+2) => read(R+3) => |
|
* readahead(R+3...B+2) => bang => read(R+3) => read(R+4) => |
|
* readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ...... |
|
* |
|
* It is going insane. Fix it by quickly scaling down the readahead size. |
|
*/ |
|
static void shrink_readahead_size_eio(struct file_ra_state *ra) |
|
{ |
|
ra->ra_pages /= 4; |
|
} |
|
|
|
/* |
|
* filemap_get_read_batch - Get a batch of pages for read |
|
* |
|
* Get a batch of pages which represent a contiguous range of bytes |
|
* in the file. No tail pages will be returned. If @index is in the |
|
* middle of a THP, the entire THP will be returned. The last page in |
|
* the batch may have Readahead set or be not Uptodate so that the |
|
* caller can take the appropriate action. |
|
*/ |
|
static void filemap_get_read_batch(struct address_space *mapping, |
|
pgoff_t index, pgoff_t max, struct pagevec *pvec) |
|
{ |
|
XA_STATE(xas, &mapping->i_pages, index); |
|
struct page *head; |
|
|
|
rcu_read_lock(); |
|
for (head = xas_load(&xas); head; head = xas_next(&xas)) { |
|
if (xas_retry(&xas, head)) |
|
continue; |
|
if (xas.xa_index > max || xa_is_value(head)) |
|
break; |
|
if (!page_cache_get_speculative(head)) |
|
goto retry; |
|
|
|
/* Has the page moved or been split? */ |
|
if (unlikely(head != xas_reload(&xas))) |
|
goto put_page; |
|
|
|
if (!pagevec_add(pvec, head)) |
|
break; |
|
if (!PageUptodate(head)) |
|
break; |
|
if (PageReadahead(head)) |
|
break; |
|
xas.xa_index = head->index + thp_nr_pages(head) - 1; |
|
xas.xa_offset = (xas.xa_index >> xas.xa_shift) & XA_CHUNK_MASK; |
|
continue; |
|
put_page: |
|
put_page(head); |
|
retry: |
|
xas_reset(&xas); |
|
} |
|
rcu_read_unlock(); |
|
} |
|
|
|
static int filemap_read_page(struct file *file, struct address_space *mapping, |
|
struct page *page) |
|
{ |
|
int error; |
|
|
|
/* |
|
* A previous I/O error may have been due to temporary failures, |
|
* eg. multipath errors. PG_error will be set again if readpage |
|
* fails. |
|
*/ |
|
ClearPageError(page); |
|
/* Start the actual read. The read will unlock the page. */ |
|
error = mapping->a_ops->readpage(file, page); |
|
if (error) |
|
return error; |
|
|
|
error = wait_on_page_locked_killable(page); |
|
if (error) |
|
return error; |
|
if (PageUptodate(page)) |
|
return 0; |
|
if (!page->mapping) /* page truncated */ |
|
return AOP_TRUNCATED_PAGE; |
|
shrink_readahead_size_eio(&file->f_ra); |
|
return -EIO; |
|
} |
|
|
|
static bool filemap_range_uptodate(struct address_space *mapping, |
|
loff_t pos, struct iov_iter *iter, struct page *page) |
|
{ |
|
int count; |
|
|
|
if (PageUptodate(page)) |
|
return true; |
|
/* pipes can't handle partially uptodate pages */ |
|
if (iov_iter_is_pipe(iter)) |
|
return false; |
|
if (!mapping->a_ops->is_partially_uptodate) |
|
return false; |
|
if (mapping->host->i_blkbits >= (PAGE_SHIFT + thp_order(page))) |
|
return false; |
|
|
|
count = iter->count; |
|
if (page_offset(page) > pos) { |
|
count -= page_offset(page) - pos; |
|
pos = 0; |
|
} else { |
|
pos -= page_offset(page); |
|
} |
|
|
|
return mapping->a_ops->is_partially_uptodate(page, pos, count); |
|
} |
|
|
|
static int filemap_update_page(struct kiocb *iocb, |
|
struct address_space *mapping, struct iov_iter *iter, |
|
struct page *page) |
|
{ |
|
int error; |
|
|
|
if (!trylock_page(page)) { |
|
if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_NOIO)) |
|
return -EAGAIN; |
|
if (!(iocb->ki_flags & IOCB_WAITQ)) { |
|
put_and_wait_on_page_locked(page, TASK_KILLABLE); |
|
return AOP_TRUNCATED_PAGE; |
|
} |
|
error = __lock_page_async(page, iocb->ki_waitq); |
|
if (error) |
|
return error; |
|
} |
|
|
|
if (!page->mapping) |
|
goto truncated; |
|
|
|
error = 0; |
|
if (filemap_range_uptodate(mapping, iocb->ki_pos, iter, page)) |
|
goto unlock; |
|
|
|
error = -EAGAIN; |
|
if (iocb->ki_flags & (IOCB_NOIO | IOCB_NOWAIT | IOCB_WAITQ)) |
|
goto unlock; |
|
|
|
error = filemap_read_page(iocb->ki_filp, mapping, page); |
|
if (error == AOP_TRUNCATED_PAGE) |
|
put_page(page); |
|
return error; |
|
truncated: |
|
unlock_page(page); |
|
put_page(page); |
|
return AOP_TRUNCATED_PAGE; |
|
unlock: |
|
unlock_page(page); |
|
return error; |
|
} |
|
|
|
static int filemap_create_page(struct file *file, |
|
struct address_space *mapping, pgoff_t index, |
|
struct pagevec *pvec) |
|
{ |
|
struct page *page; |
|
int error; |
|
|
|
page = page_cache_alloc(mapping); |
|
if (!page) |
|
return -ENOMEM; |
|
|
|
error = add_to_page_cache_lru(page, mapping, index, |
|
mapping_gfp_constraint(mapping, GFP_KERNEL)); |
|
if (error == -EEXIST) |
|
error = AOP_TRUNCATED_PAGE; |
|
if (error) |
|
goto error; |
|
|
|
error = filemap_read_page(file, mapping, page); |
|
if (error) |
|
goto error; |
|
|
|
pagevec_add(pvec, page); |
|
return 0; |
|
error: |
|
put_page(page); |
|
return error; |
|
} |
|
|
|
static int filemap_readahead(struct kiocb *iocb, struct file *file, |
|
struct address_space *mapping, struct page *page, |
|
pgoff_t last_index) |
|
{ |
|
if (iocb->ki_flags & IOCB_NOIO) |
|
return -EAGAIN; |
|
page_cache_async_readahead(mapping, &file->f_ra, file, page, |
|
page->index, last_index - page->index); |
|
return 0; |
|
} |
|
|
|
static int filemap_get_pages(struct kiocb *iocb, struct iov_iter *iter, |
|
struct pagevec *pvec) |
|
{ |
|
struct file *filp = iocb->ki_filp; |
|
struct address_space *mapping = filp->f_mapping; |
|
struct file_ra_state *ra = &filp->f_ra; |
|
pgoff_t index = iocb->ki_pos >> PAGE_SHIFT; |
|
pgoff_t last_index; |
|
struct page *page; |
|
int err = 0; |
|
|
|
last_index = DIV_ROUND_UP(iocb->ki_pos + iter->count, PAGE_SIZE); |
|
retry: |
|
if (fatal_signal_pending(current)) |
|
return -EINTR; |
|
|
|
filemap_get_read_batch(mapping, index, last_index, pvec); |
|
if (!pagevec_count(pvec)) { |
|
if (iocb->ki_flags & IOCB_NOIO) |
|
return -EAGAIN; |
|
page_cache_sync_readahead(mapping, ra, filp, index, |
|
last_index - index); |
|
filemap_get_read_batch(mapping, index, last_index, pvec); |
|
} |
|
if (!pagevec_count(pvec)) { |
|
if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_WAITQ)) |
|
return -EAGAIN; |
|
err = filemap_create_page(filp, mapping, |
|
iocb->ki_pos >> PAGE_SHIFT, pvec); |
|
if (err == AOP_TRUNCATED_PAGE) |
|
goto retry; |
|
return err; |
|
} |
|
|
|
page = pvec->pages[pagevec_count(pvec) - 1]; |
|
if (PageReadahead(page)) { |
|
err = filemap_readahead(iocb, filp, mapping, page, last_index); |
|
if (err) |
|
goto err; |
|
} |
|
if (!PageUptodate(page)) { |
|
if ((iocb->ki_flags & IOCB_WAITQ) && pagevec_count(pvec) > 1) |
|
iocb->ki_flags |= IOCB_NOWAIT; |
|
err = filemap_update_page(iocb, mapping, iter, page); |
|
if (err) |
|
goto err; |
|
} |
|
|
|
return 0; |
|
err: |
|
if (err < 0) |
|
put_page(page); |
|
if (likely(--pvec->nr)) |
|
return 0; |
|
if (err == AOP_TRUNCATED_PAGE) |
|
goto retry; |
|
return err; |
|
} |
|
|
|
/** |
|
* filemap_read - Read data from the page cache. |
|
* @iocb: The iocb to read. |
|
* @iter: Destination for the data. |
|
* @already_read: Number of bytes already read by the caller. |
|
* |
|
* Copies data from the page cache. If the data is not currently present, |
|
* uses the readahead and readpage address_space operations to fetch it. |
|
* |
|
* Return: Total number of bytes copied, including those already read by |
|
* the caller. If an error happens before any bytes are copied, returns |
|
* a negative error number. |
|
*/ |
|
ssize_t filemap_read(struct kiocb *iocb, struct iov_iter *iter, |
|
ssize_t already_read) |
|
{ |
|
struct file *filp = iocb->ki_filp; |
|
struct file_ra_state *ra = &filp->f_ra; |
|
struct address_space *mapping = filp->f_mapping; |
|
struct inode *inode = mapping->host; |
|
struct pagevec pvec; |
|
int i, error = 0; |
|
bool writably_mapped; |
|
loff_t isize, end_offset; |
|
|
|
if (unlikely(iocb->ki_pos >= inode->i_sb->s_maxbytes)) |
|
return 0; |
|
if (unlikely(!iov_iter_count(iter))) |
|
return 0; |
|
|
|
iov_iter_truncate(iter, inode->i_sb->s_maxbytes); |
|
pagevec_init(&pvec); |
|
|
|
do { |
|
cond_resched(); |
|
|
|
/* |
|
* If we've already successfully copied some data, then we |
|
* can no longer safely return -EIOCBQUEUED. Hence mark |
|
* an async read NOWAIT at that point. |
|
*/ |
|
if ((iocb->ki_flags & IOCB_WAITQ) && already_read) |
|
iocb->ki_flags |= IOCB_NOWAIT; |
|
|
|
error = filemap_get_pages(iocb, iter, &pvec); |
|
if (error < 0) |
|
break; |
|
|
|
/* |
|
* i_size must be checked after we know the pages are Uptodate. |
|
* |
|
* Checking i_size after the check allows us to calculate |
|
* the correct value for "nr", which means the zero-filled |
|
* part of the page is not copied back to userspace (unless |
|
* another truncate extends the file - this is desired though). |
|
*/ |
|
isize = i_size_read(inode); |
|
if (unlikely(iocb->ki_pos >= isize)) |
|
goto put_pages; |
|
end_offset = min_t(loff_t, isize, iocb->ki_pos + iter->count); |
|
|
|
/* |
|
* Once we start copying data, we don't want to be touching any |
|
* cachelines that might be contended: |
|
*/ |
|
writably_mapped = mapping_writably_mapped(mapping); |
|
|
|
/* |
|
* When a sequential read accesses a page several times, only |
|
* mark it as accessed the first time. |
|
*/ |
|
if (iocb->ki_pos >> PAGE_SHIFT != |
|
ra->prev_pos >> PAGE_SHIFT) |
|
mark_page_accessed(pvec.pages[0]); |
|
|
|
for (i = 0; i < pagevec_count(&pvec); i++) { |
|
struct page *page = pvec.pages[i]; |
|
size_t page_size = thp_size(page); |
|
size_t offset = iocb->ki_pos & (page_size - 1); |
|
size_t bytes = min_t(loff_t, end_offset - iocb->ki_pos, |
|
page_size - offset); |
|
size_t copied; |
|
|
|
if (end_offset < page_offset(page)) |
|
break; |
|
if (i > 0) |
|
mark_page_accessed(page); |
|
/* |
|
* If users can be writing to this page using arbitrary |
|
* virtual addresses, take care about potential aliasing |
|
* before reading the page on the kernel side. |
|
*/ |
|
if (writably_mapped) { |
|
int j; |
|
|
|
for (j = 0; j < thp_nr_pages(page); j++) |
|
flush_dcache_page(page + j); |
|
} |
|
|
|
copied = copy_page_to_iter(page, offset, bytes, iter); |
|
|
|
already_read += copied; |
|
iocb->ki_pos += copied; |
|
ra->prev_pos = iocb->ki_pos; |
|
|
|
if (copied < bytes) { |
|
error = -EFAULT; |
|
break; |
|
} |
|
} |
|
put_pages: |
|
for (i = 0; i < pagevec_count(&pvec); i++) |
|
put_page(pvec.pages[i]); |
|
pagevec_reinit(&pvec); |
|
} while (iov_iter_count(iter) && iocb->ki_pos < isize && !error); |
|
|
|
file_accessed(filp); |
|
|
|
return already_read ? already_read : error; |
|
} |
|
EXPORT_SYMBOL_GPL(filemap_read); |
|
|
|
/** |
|
* generic_file_read_iter - generic filesystem read routine |
|
* @iocb: kernel I/O control block |
|
* @iter: destination for the data read |
|
* |
|
* This is the "read_iter()" routine for all filesystems |
|
* that can use the page cache directly. |
|
* |
|
* The IOCB_NOWAIT flag in iocb->ki_flags indicates that -EAGAIN shall |
|
* be returned when no data can be read without waiting for I/O requests |
|
* to complete; it doesn't prevent readahead. |
|
* |
|
* The IOCB_NOIO flag in iocb->ki_flags indicates that no new I/O |
|
* requests shall be made for the read or for readahead. When no data |
|
* can be read, -EAGAIN shall be returned. When readahead would be |
|
* triggered, a partial, possibly empty read shall be returned. |
|
* |
|
* Return: |
|
* * number of bytes copied, even for partial reads |
|
* * negative error code (or 0 if IOCB_NOIO) if nothing was read |
|
*/ |
|
ssize_t |
|
generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter) |
|
{ |
|
size_t count = iov_iter_count(iter); |
|
ssize_t retval = 0; |
|
|
|
if (!count) |
|
return 0; /* skip atime */ |
|
|
|
if (iocb->ki_flags & IOCB_DIRECT) { |
|
struct file *file = iocb->ki_filp; |
|
struct address_space *mapping = file->f_mapping; |
|
struct inode *inode = mapping->host; |
|
loff_t size; |
|
|
|
size = i_size_read(inode); |
|
if (iocb->ki_flags & IOCB_NOWAIT) { |
|
if (filemap_range_has_page(mapping, iocb->ki_pos, |
|
iocb->ki_pos + count - 1)) |
|
return -EAGAIN; |
|
} else { |
|
retval = filemap_write_and_wait_range(mapping, |
|
iocb->ki_pos, |
|
iocb->ki_pos + count - 1); |
|
if (retval < 0) |
|
return retval; |
|
} |
|
|
|
file_accessed(file); |
|
|
|
retval = mapping->a_ops->direct_IO(iocb, iter); |
|
if (retval >= 0) { |
|
iocb->ki_pos += retval; |
|
count -= retval; |
|
} |
|
if (retval != -EIOCBQUEUED) |
|
iov_iter_revert(iter, count - iov_iter_count(iter)); |
|
|
|
/* |
|
* Btrfs can have a short DIO read if we encounter |
|
* compressed extents, so if there was an error, or if |
|
* we've already read everything we wanted to, or if |
|
* there was a short read because we hit EOF, go ahead |
|
* and return. Otherwise fallthrough to buffered io for |
|
* the rest of the read. Buffered reads will not work for |
|
* DAX files, so don't bother trying. |
|
*/ |
|
if (retval < 0 || !count || iocb->ki_pos >= size || |
|
IS_DAX(inode)) |
|
return retval; |
|
} |
|
|
|
return filemap_read(iocb, iter, retval); |
|
} |
|
EXPORT_SYMBOL(generic_file_read_iter); |
|
|
|
static inline loff_t page_seek_hole_data(struct xa_state *xas, |
|
struct address_space *mapping, struct page *page, |
|
loff_t start, loff_t end, bool seek_data) |
|
{ |
|
const struct address_space_operations *ops = mapping->a_ops; |
|
size_t offset, bsz = i_blocksize(mapping->host); |
|
|
|
if (xa_is_value(page) || PageUptodate(page)) |
|
return seek_data ? start : end; |
|
if (!ops->is_partially_uptodate) |
|
return seek_data ? end : start; |
|
|
|
xas_pause(xas); |
|
rcu_read_unlock(); |
|
lock_page(page); |
|
if (unlikely(page->mapping != mapping)) |
|
goto unlock; |
|
|
|
offset = offset_in_thp(page, start) & ~(bsz - 1); |
|
|
|
do { |
|
if (ops->is_partially_uptodate(page, offset, bsz) == seek_data) |
|
break; |
|
start = (start + bsz) & ~(bsz - 1); |
|
offset += bsz; |
|
} while (offset < thp_size(page)); |
|
unlock: |
|
unlock_page(page); |
|
rcu_read_lock(); |
|
return start; |
|
} |
|
|
|
static inline |
|
unsigned int seek_page_size(struct xa_state *xas, struct page *page) |
|
{ |
|
if (xa_is_value(page)) |
|
return PAGE_SIZE << xa_get_order(xas->xa, xas->xa_index); |
|
return thp_size(page); |
|
} |
|
|
|
/** |
|
* mapping_seek_hole_data - Seek for SEEK_DATA / SEEK_HOLE in the page cache. |
|
* @mapping: Address space to search. |
|
* @start: First byte to consider. |
|
* @end: Limit of search (exclusive). |
|
* @whence: Either SEEK_HOLE or SEEK_DATA. |
|
* |
|
* If the page cache knows which blocks contain holes and which blocks |
|
* contain data, your filesystem can use this function to implement |
|
* SEEK_HOLE and SEEK_DATA. This is useful for filesystems which are |
|
* entirely memory-based such as tmpfs, and filesystems which support |
|
* unwritten extents. |
|
* |
|
* Return: The requested offset on successs, or -ENXIO if @whence specifies |
|
* SEEK_DATA and there is no data after @start. There is an implicit hole |
|
* after @end - 1, so SEEK_HOLE returns @end if all the bytes between @start |
|
* and @end contain data. |
|
*/ |
|
loff_t mapping_seek_hole_data(struct address_space *mapping, loff_t start, |
|
loff_t end, int whence) |
|
{ |
|
XA_STATE(xas, &mapping->i_pages, start >> PAGE_SHIFT); |
|
pgoff_t max = (end - 1) >> PAGE_SHIFT; |
|
bool seek_data = (whence == SEEK_DATA); |
|
struct page *page; |
|
|
|
if (end <= start) |
|
return -ENXIO; |
|
|
|
rcu_read_lock(); |
|
while ((page = find_get_entry(&xas, max, XA_PRESENT))) { |
|
loff_t pos = (u64)xas.xa_index << PAGE_SHIFT; |
|
unsigned int seek_size; |
|
|
|
if (start < pos) { |
|
if (!seek_data) |
|
goto unlock; |
|
start = pos; |
|
} |
|
|
|
seek_size = seek_page_size(&xas, page); |
|
pos = round_up(pos + 1, seek_size); |
|
start = page_seek_hole_data(&xas, mapping, page, start, pos, |
|
seek_data); |
|
if (start < pos) |
|
goto unlock; |
|
if (start >= end) |
|
break; |
|
if (seek_size > PAGE_SIZE) |
|
xas_set(&xas, pos >> PAGE_SHIFT); |
|
if (!xa_is_value(page)) |
|
put_page(page); |
|
} |
|
if (seek_data) |
|
start = -ENXIO; |
|
unlock: |
|
rcu_read_unlock(); |
|
if (page && !xa_is_value(page)) |
|
put_page(page); |
|
if (start > end) |
|
return end; |
|
return start; |
|
} |
|
|
|
#ifdef CONFIG_MMU |
|
#define MMAP_LOTSAMISS (100) |
|
/* |
|
* lock_page_maybe_drop_mmap - lock the page, possibly dropping the mmap_lock |
|
* @vmf - the vm_fault for this fault. |
|
* @page - the page to lock. |
|
* @fpin - the pointer to the file we may pin (or is already pinned). |
|
* |
|
* This works similar to lock_page_or_retry in that it can drop the mmap_lock. |
|
* It differs in that it actually returns the page locked if it returns 1 and 0 |
|
* if it couldn't lock the page. If we did have to drop the mmap_lock then fpin |
|
* will point to the pinned file and needs to be fput()'ed at a later point. |
|
*/ |
|
static int lock_page_maybe_drop_mmap(struct vm_fault *vmf, struct page *page, |
|
struct file **fpin) |
|
{ |
|
if (trylock_page(page)) |
|
return 1; |
|
|
|
/* |
|
* NOTE! This will make us return with VM_FAULT_RETRY, but with |
|
* the mmap_lock still held. That's how FAULT_FLAG_RETRY_NOWAIT |
|
* is supposed to work. We have way too many special cases.. |
|
*/ |
|
if (vmf->flags & FAULT_FLAG_RETRY_NOWAIT) |
|
return 0; |
|
|
|
*fpin = maybe_unlock_mmap_for_io(vmf, *fpin); |
|
if (vmf->flags & FAULT_FLAG_KILLABLE) { |
|
if (__lock_page_killable(page)) { |
|
/* |
|
* We didn't have the right flags to drop the mmap_lock, |
|
* but all fault_handlers only check for fatal signals |
|
* if we return VM_FAULT_RETRY, so we need to drop the |
|
* mmap_lock here and return 0 if we don't have a fpin. |
|
*/ |
|
if (*fpin == NULL) |
|
mmap_read_unlock(vmf->vma->vm_mm); |
|
return 0; |
|
} |
|
} else |
|
__lock_page(page); |
|
return 1; |
|
} |
|
|
|
|
|
/* |
|
* Synchronous readahead happens when we don't even find a page in the page |
|
* cache at all. We don't want to perform IO under the mmap sem, so if we have |
|
* to drop the mmap sem we return the file that was pinned in order for us to do |
|
* that. If we didn't pin a file then we return NULL. The file that is |
|
* returned needs to be fput()'ed when we're done with it. |
|
*/ |
|
static struct file *do_sync_mmap_readahead(struct vm_fault *vmf) |
|
{ |
|
struct file *file = vmf->vma->vm_file; |
|
struct file_ra_state *ra = &file->f_ra; |
|
struct address_space *mapping = file->f_mapping; |
|
DEFINE_READAHEAD(ractl, file, mapping, vmf->pgoff); |
|
struct file *fpin = NULL; |
|
unsigned int mmap_miss; |
|
|
|
/* If we don't want any read-ahead, don't bother */ |
|
if (vmf->vma->vm_flags & VM_RAND_READ) |
|
return fpin; |
|
if (!ra->ra_pages) |
|
return fpin; |
|
|
|
if (vmf->vma->vm_flags & VM_SEQ_READ) { |
|
fpin = maybe_unlock_mmap_for_io(vmf, fpin); |
|
page_cache_sync_ra(&ractl, ra, ra->ra_pages); |
|
return fpin; |
|
} |
|
|
|
/* Avoid banging the cache line if not needed */ |
|
mmap_miss = READ_ONCE(ra->mmap_miss); |
|
if (mmap_miss < MMAP_LOTSAMISS * 10) |
|
WRITE_ONCE(ra->mmap_miss, ++mmap_miss); |
|
|
|
/* |
|
* Do we miss much more than hit in this file? If so, |
|
* stop bothering with read-ahead. It will only hurt. |
|
*/ |
|
if (mmap_miss > MMAP_LOTSAMISS) |
|
return fpin; |
|
|
|
/* |
|
* mmap read-around |
|
*/ |
|
fpin = maybe_unlock_mmap_for_io(vmf, fpin); |
|
ra->start = max_t(long, 0, vmf->pgoff - ra->ra_pages / 2); |
|
ra->size = ra->ra_pages; |
|
ra->async_size = ra->ra_pages / 4; |
|
ractl._index = ra->start; |
|
do_page_cache_ra(&ractl, ra->size, ra->async_size); |
|
return fpin; |
|
} |
|
|
|
/* |
|
* Asynchronous readahead happens when we find the page and PG_readahead, |
|
* so we want to possibly extend the readahead further. We return the file that |
|
* was pinned if we have to drop the mmap_lock in order to do IO. |
|
*/ |
|
static struct file *do_async_mmap_readahead(struct vm_fault *vmf, |
|
struct page *page) |
|
{ |
|
struct file *file = vmf->vma->vm_file; |
|
struct file_ra_state *ra = &file->f_ra; |
|
struct address_space *mapping = file->f_mapping; |
|
struct file *fpin = NULL; |
|
unsigned int mmap_miss; |
|
pgoff_t offset = vmf->pgoff; |
|
|
|
/* If we don't want any read-ahead, don't bother */ |
|
if (vmf->vma->vm_flags & VM_RAND_READ || !ra->ra_pages) |
|
return fpin; |
|
mmap_miss = READ_ONCE(ra->mmap_miss); |
|
if (mmap_miss) |
|
WRITE_ONCE(ra->mmap_miss, --mmap_miss); |
|
if (PageReadahead(page)) { |
|
fpin = maybe_unlock_mmap_for_io(vmf, fpin); |
|
page_cache_async_readahead(mapping, ra, file, |
|
page, offset, ra->ra_pages); |
|
} |
|
return fpin; |
|
} |
|
|
|
/** |
|
* filemap_fault - read in file data for page fault handling |
|
* @vmf: struct vm_fault containing details of the fault |
|
* |
|
* filemap_fault() is invoked via the vma operations vector for a |
|
* mapped memory region to read in file data during a page fault. |
|
* |
|
* The goto's are kind of ugly, but this streamlines the normal case of having |
|
* it in the page cache, and handles the special cases reasonably without |
|
* having a lot of duplicated code. |
|
* |
|
* vma->vm_mm->mmap_lock must be held on entry. |
|
* |
|
* If our return value has VM_FAULT_RETRY set, it's because the mmap_lock |
|
* may be dropped before doing I/O or by lock_page_maybe_drop_mmap(). |
|
* |
|
* If our return value does not have VM_FAULT_RETRY set, the mmap_lock |
|
* has not been released. |
|
* |
|
* We never return with VM_FAULT_RETRY and a bit from VM_FAULT_ERROR set. |
|
* |
|
* Return: bitwise-OR of %VM_FAULT_ codes. |
|
*/ |
|
vm_fault_t filemap_fault(struct vm_fault *vmf) |
|
{ |
|
int error; |
|
struct file *file = vmf->vma->vm_file; |
|
struct file *fpin = NULL; |
|
struct address_space *mapping = file->f_mapping; |
|
struct file_ra_state *ra = &file->f_ra; |
|
struct inode *inode = mapping->host; |
|
pgoff_t offset = vmf->pgoff; |
|
pgoff_t max_off; |
|
struct page *page; |
|
vm_fault_t ret = 0; |
|
|
|
max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE); |
|
if (unlikely(offset >= max_off)) |
|
return VM_FAULT_SIGBUS; |
|
|
|
/* |
|
* Do we have something in the page cache already? |
|
*/ |
|
page = find_get_page(mapping, offset); |
|
if (likely(page) && !(vmf->flags & FAULT_FLAG_TRIED)) { |
|
/* |
|
* We found the page, so try async readahead before |
|
* waiting for the lock. |
|
*/ |
|
fpin = do_async_mmap_readahead(vmf, page); |
|
} else if (!page) { |
|
/* No page in the page cache at all */ |
|
count_vm_event(PGMAJFAULT); |
|
count_memcg_event_mm(vmf->vma->vm_mm, PGMAJFAULT); |
|
ret = VM_FAULT_MAJOR; |
|
fpin = do_sync_mmap_readahead(vmf); |
|
retry_find: |
|
page = pagecache_get_page(mapping, offset, |
|
FGP_CREAT|FGP_FOR_MMAP, |
|
vmf->gfp_mask); |
|
if (!page) { |
|
if (fpin) |
|
goto out_retry; |
|
return VM_FAULT_OOM; |
|
} |
|
} |
|
|
|
if (!lock_page_maybe_drop_mmap(vmf, page, &fpin)) |
|
goto out_retry; |
|
|
|
/* Did it get truncated? */ |
|
if (unlikely(compound_head(page)->mapping != mapping)) { |
|
unlock_page(page); |
|
put_page(page); |
|
goto retry_find; |
|
} |
|
VM_BUG_ON_PAGE(page_to_pgoff(page) != offset, page); |
|
|
|
/* |
|
* We have a locked page in the page cache, now we need to check |
|
* that it's up-to-date. If not, it is going to be due to an error. |
|
*/ |
|
if (unlikely(!PageUptodate(page))) |
|
goto page_not_uptodate; |
|
|
|
/* |
|
* We've made it this far and we had to drop our mmap_lock, now is the |
|
* time to return to the upper layer and have it re-find the vma and |
|
* redo the fault. |
|
*/ |
|
if (fpin) { |
|
unlock_page(page); |
|
goto out_retry; |
|
} |
|
|
|
/* |
|
* Found the page and have a reference on it. |
|
* We must recheck i_size under page lock. |
|
*/ |
|
max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE); |
|
if (unlikely(offset >= max_off)) { |
|
unlock_page(page); |
|
put_page(page); |
|
return VM_FAULT_SIGBUS; |
|
} |
|
|
|
vmf->page = page; |
|
return ret | VM_FAULT_LOCKED; |
|
|
|
page_not_uptodate: |
|
/* |
|
* Umm, take care of errors if the page isn't up-to-date. |
|
* Try to re-read it _once_. We do this synchronously, |
|
* because there really aren't any performance issues here |
|
* and we need to check for errors. |
|
*/ |
|
ClearPageError(page); |
|
fpin = maybe_unlock_mmap_for_io(vmf, fpin); |
|
error = mapping->a_ops->readpage(file, page); |
|
if (!error) { |
|
wait_on_page_locked(page); |
|
if (!PageUptodate(page)) |
|
error = -EIO; |
|
} |
|
if (fpin) |
|
goto out_retry; |
|
put_page(page); |
|
|
|
if (!error || error == AOP_TRUNCATED_PAGE) |
|
goto retry_find; |
|
|
|
shrink_readahead_size_eio(ra); |
|
return VM_FAULT_SIGBUS; |
|
|
|
out_retry: |
|
/* |
|
* We dropped the mmap_lock, we need to return to the fault handler to |
|
* re-find the vma and come back and find our hopefully still populated |
|
* page. |
|
*/ |
|
if (page) |
|
put_page(page); |
|
if (fpin) |
|
fput(fpin); |
|
return ret | VM_FAULT_RETRY; |
|
} |
|
EXPORT_SYMBOL(filemap_fault); |
|
|
|
static bool filemap_map_pmd(struct vm_fault *vmf, struct page *page) |
|
{ |
|
struct mm_struct *mm = vmf->vma->vm_mm; |
|
|
|
/* Huge page is mapped? No need to proceed. */ |
|
if (pmd_trans_huge(*vmf->pmd)) { |
|
unlock_page(page); |
|
put_page(page); |
|
return true; |
|
} |
|
|
|
if (pmd_none(*vmf->pmd) && PageTransHuge(page)) { |
|
vm_fault_t ret = do_set_pmd(vmf, page); |
|
if (!ret) { |
|
/* The page is mapped successfully, reference consumed. */ |
|
unlock_page(page); |
|
return true; |
|
} |
|
} |
|
|
|
if (pmd_none(*vmf->pmd)) { |
|
vmf->ptl = pmd_lock(mm, vmf->pmd); |
|
if (likely(pmd_none(*vmf->pmd))) { |
|
mm_inc_nr_ptes(mm); |
|
pmd_populate(mm, vmf->pmd, vmf->prealloc_pte); |
|
vmf->prealloc_pte = NULL; |
|
} |
|
spin_unlock(vmf->ptl); |
|
} |
|
|
|
/* See comment in handle_pte_fault() */ |
|
if (pmd_devmap_trans_unstable(vmf->pmd)) { |
|
unlock_page(page); |
|
put_page(page); |
|
return true; |
|
} |
|
|
|
return false; |
|
} |
|
|
|
static struct page *next_uptodate_page(struct page *page, |
|
struct address_space *mapping, |
|
struct xa_state *xas, pgoff_t end_pgoff) |
|
{ |
|
unsigned long max_idx; |
|
|
|
do { |
|
if (!page) |
|
return NULL; |
|
if (xas_retry(xas, page)) |
|
continue; |
|
if (xa_is_value(page)) |
|
continue; |
|
if (PageLocked(page)) |
|
continue; |
|
if (!page_cache_get_speculative(page)) |
|
continue; |
|
/* Has the page moved or been split? */ |
|
if (unlikely(page != xas_reload(xas))) |
|
goto skip; |
|
if (!PageUptodate(page) || PageReadahead(page)) |
|
goto skip; |
|
if (PageHWPoison(page)) |
|
goto skip; |
|
if (!trylock_page(page)) |
|
goto skip; |
|
if (page->mapping != mapping) |
|
goto unlock; |
|
if (!PageUptodate(page)) |
|
goto unlock; |
|
max_idx = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE); |
|
if (xas->xa_index >= max_idx) |
|
goto unlock; |
|
return page; |
|
unlock: |
|
unlock_page(page); |
|
skip: |
|
put_page(page); |
|
} while ((page = xas_next_entry(xas, end_pgoff)) != NULL); |
|
|
|
return NULL; |
|
} |
|
|
|
static inline struct page *first_map_page(struct address_space *mapping, |
|
struct xa_state *xas, |
|
pgoff_t end_pgoff) |
|
{ |
|
return next_uptodate_page(xas_find(xas, end_pgoff), |
|
mapping, xas, end_pgoff); |
|
} |
|
|
|
static inline struct page *next_map_page(struct address_space *mapping, |
|
struct xa_state *xas, |
|
pgoff_t end_pgoff) |
|
{ |
|
return next_uptodate_page(xas_next_entry(xas, end_pgoff), |
|
mapping, xas, end_pgoff); |
|
} |
|
|
|
vm_fault_t filemap_map_pages(struct vm_fault *vmf, |
|
pgoff_t start_pgoff, pgoff_t end_pgoff) |
|
{ |
|
struct vm_area_struct *vma = vmf->vma; |
|
struct file *file = vma->vm_file; |
|
struct address_space *mapping = file->f_mapping; |
|
pgoff_t last_pgoff = start_pgoff; |
|
unsigned long addr; |
|
XA_STATE(xas, &mapping->i_pages, start_pgoff); |
|
struct page *head, *page; |
|
unsigned int mmap_miss = READ_ONCE(file->f_ra.mmap_miss); |
|
vm_fault_t ret = 0; |
|
|
|
rcu_read_lock(); |
|
head = first_map_page(mapping, &xas, end_pgoff); |
|
if (!head) |
|
goto out; |
|
|
|
if (filemap_map_pmd(vmf, head)) { |
|
ret = VM_FAULT_NOPAGE; |
|
goto out; |
|
} |
|
|
|
addr = vma->vm_start + ((start_pgoff - vma->vm_pgoff) << PAGE_SHIFT); |
|
vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, addr, &vmf->ptl); |
|
do { |
|
page = find_subpage(head, xas.xa_index); |
|
if (PageHWPoison(page)) |
|
goto unlock; |
|
|
|
if (mmap_miss > 0) |
|
mmap_miss--; |
|
|
|
addr += (xas.xa_index - last_pgoff) << PAGE_SHIFT; |
|
vmf->pte += xas.xa_index - last_pgoff; |
|
last_pgoff = xas.xa_index; |
|
|
|
if (!pte_none(*vmf->pte)) |
|
goto unlock; |
|
|
|
/* We're about to handle the fault */ |
|
if (vmf->address == addr) |
|
ret = VM_FAULT_NOPAGE; |
|
|
|
do_set_pte(vmf, page, addr); |
|
/* no need to invalidate: a not-present page won't be cached */ |
|
update_mmu_cache(vma, addr, vmf->pte); |
|
unlock_page(head); |
|
continue; |
|
unlock: |
|
unlock_page(head); |
|
put_page(head); |
|
} while ((head = next_map_page(mapping, &xas, end_pgoff)) != NULL); |
|
pte_unmap_unlock(vmf->pte, vmf->ptl); |
|
out: |
|
rcu_read_unlock(); |
|
WRITE_ONCE(file->f_ra.mmap_miss, mmap_miss); |
|
return ret; |
|
} |
|
EXPORT_SYMBOL(filemap_map_pages); |
|
|
|
vm_fault_t filemap_page_mkwrite(struct vm_fault *vmf) |
|
{ |
|
struct address_space *mapping = vmf->vma->vm_file->f_mapping; |
|
struct page *page = vmf->page; |
|
vm_fault_t ret = VM_FAULT_LOCKED; |
|
|
|
sb_start_pagefault(mapping->host->i_sb); |
|
file_update_time(vmf->vma->vm_file); |
|
lock_page(page); |
|
if (page->mapping != mapping) { |
|
unlock_page(page); |
|
ret = VM_FAULT_NOPAGE; |
|
goto out; |
|
} |
|
/* |
|
* We mark the page dirty already here so that when freeze is in |
|
* progress, we are guaranteed that writeback during freezing will |
|
* see the dirty page and writeprotect it again. |
|
*/ |
|
set_page_dirty(page); |
|
wait_for_stable_page(page); |
|
out: |
|
sb_end_pagefault(mapping->host->i_sb); |
|
return ret; |
|
} |
|
|
|
const struct vm_operations_struct generic_file_vm_ops = { |
|
.fault = filemap_fault, |
|
.map_pages = filemap_map_pages, |
|
.page_mkwrite = filemap_page_mkwrite, |
|
}; |
|
|
|
/* This is used for a general mmap of a disk file */ |
|
|
|
int generic_file_mmap(struct file * file, struct vm_area_struct * vma) |
|
{ |
|
struct address_space *mapping = file->f_mapping; |
|
|
|
if (!mapping->a_ops->readpage) |
|
return -ENOEXEC; |
|
file_accessed(file); |
|
vma->vm_ops = &generic_file_vm_ops; |
|
return 0; |
|
} |
|
|
|
/* |
|
* This is for filesystems which do not implement ->writepage. |
|
*/ |
|
int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma) |
|
{ |
|
if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE)) |
|
return -EINVAL; |
|
return generic_file_mmap(file, vma); |
|
} |
|
#else |
|
vm_fault_t filemap_page_mkwrite(struct vm_fault *vmf) |
|
{ |
|
return VM_FAULT_SIGBUS; |
|
} |
|
int generic_file_mmap(struct file * file, struct vm_area_struct * vma) |
|
{ |
|
return -ENOSYS; |
|
} |
|
int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma) |
|
{ |
|
return -ENOSYS; |
|
} |
|
#endif /* CONFIG_MMU */ |
|
|
|
EXPORT_SYMBOL(filemap_page_mkwrite); |
|
EXPORT_SYMBOL(generic_file_mmap); |
|
EXPORT_SYMBOL(generic_file_readonly_mmap); |
|
|
|
static struct page *wait_on_page_read(struct page *page) |
|
{ |
|
if (!IS_ERR(page)) { |
|
wait_on_page_locked(page); |
|
if (!PageUptodate(page)) { |
|
put_page(page); |
|
page = ERR_PTR(-EIO); |
|
} |
|
} |
|
return page; |
|
} |
|
|
|
static struct page *do_read_cache_page(struct address_space *mapping, |
|
pgoff_t index, |
|
int (*filler)(void *, struct page *), |
|
void *data, |
|
gfp_t gfp) |
|
{ |
|
struct page *page; |
|
int err; |
|
repeat: |
|
page = find_get_page(mapping, index); |
|
if (!page) { |
|
page = __page_cache_alloc(gfp); |
|
if (!page) |
|
return ERR_PTR(-ENOMEM); |
|
err = add_to_page_cache_lru(page, mapping, index, gfp); |
|
if (unlikely(err)) { |
|
put_page(page); |
|
if (err == -EEXIST) |
|
goto repeat; |
|
/* Presumably ENOMEM for xarray node */ |
|
return ERR_PTR(err); |
|
} |
|
|
|
filler: |
|
if (filler) |
|
err = filler(data, page); |
|
else |
|
err = mapping->a_ops->readpage(data, page); |
|
|
|
if (err < 0) { |
|
put_page(page); |
|
return ERR_PTR(err); |
|
} |
|
|
|
page = wait_on_page_read(page); |
|
if (IS_ERR(page)) |
|
return page; |
|
goto out; |
|
} |
|
if (PageUptodate(page)) |
|
goto out; |
|
|
|
/* |
|
* Page is not up to date and may be locked due to one of the following |
|
* case a: Page is being filled and the page lock is held |
|
* case b: Read/write error clearing the page uptodate status |
|
* case c: Truncation in progress (page locked) |
|
* case d: Reclaim in progress |
|
* |
|
* Case a, the page will be up to date when the page is unlocked. |
|
* There is no need to serialise on the page lock here as the page |
|
* is pinned so the lock gives no additional protection. Even if the |
|
* page is truncated, the data is still valid if PageUptodate as |
|
* it's a race vs truncate race. |
|
* Case b, the page will not be up to date |
|
* Case c, the page may be truncated but in itself, the data may still |
|
* be valid after IO completes as it's a read vs truncate race. The |
|
* operation must restart if the page is not uptodate on unlock but |
|
* otherwise serialising on page lock to stabilise the mapping gives |
|
* no additional guarantees to the caller as the page lock is |
|
* released before return. |
|
* Case d, similar to truncation. If reclaim holds the page lock, it |
|
* will be a race with remove_mapping that determines if the mapping |
|
* is valid on unlock but otherwise the data is valid and there is |
|
* no need to serialise with page lock. |
|
* |
|
* As the page lock gives no additional guarantee, we optimistically |
|
* wait on the page to be unlocked and check if it's up to date and |
|
* use the page if it is. Otherwise, the page lock is required to |
|
* distinguish between the different cases. The motivation is that we |
|
* avoid spurious serialisations and wakeups when multiple processes |
|
* wait on the same page for IO to complete. |
|
*/ |
|
wait_on_page_locked(page); |
|
if (PageUptodate(page)) |
|
goto out; |
|
|
|
/* Distinguish between all the cases under the safety of the lock */ |
|
lock_page(page); |
|
|
|
/* Case c or d, restart the operation */ |
|
if (!page->mapping) { |
|
unlock_page(page); |
|
put_page(page); |
|
goto repeat; |
|
} |
|
|
|
/* Someone else locked and filled the page in a very small window */ |
|
if (PageUptodate(page)) { |
|
unlock_page(page); |
|
goto out; |
|
} |
|
|
|
/* |
|
* A previous I/O error may have been due to temporary |
|
* failures. |
|
* Clear page error before actual read, PG_error will be |
|
* set again if read page fails. |
|
*/ |
|
ClearPageError(page); |
|
goto filler; |
|
|
|
out: |
|
mark_page_accessed(page); |
|
return page; |
|
} |
|
|
|
/** |
|
* read_cache_page - read into page cache, fill it if needed |
|
* @mapping: the page's address_space |
|
* @index: the page index |
|
* @filler: function to perform the read |
|
* @data: first arg to filler(data, page) function, often left as NULL |
|
* |
|
* Read into the page cache. If a page already exists, and PageUptodate() is |
|
* not set, try to fill the page and wait for it to become unlocked. |
|
* |
|
* If the page does not get brought uptodate, return -EIO. |
|
* |
|
* Return: up to date page on success, ERR_PTR() on failure. |
|
*/ |
|
struct page *read_cache_page(struct address_space *mapping, |
|
pgoff_t index, |
|
int (*filler)(void *, struct page *), |
|
void *data) |
|
{ |
|
return do_read_cache_page(mapping, index, filler, data, |
|
mapping_gfp_mask(mapping)); |
|
} |
|
EXPORT_SYMBOL(read_cache_page); |
|
|
|
/** |
|
* read_cache_page_gfp - read into page cache, using specified page allocation flags. |
|
* @mapping: the page's address_space |
|
* @index: the page index |
|
* @gfp: the page allocator flags to use if allocating |
|
* |
|
* This is the same as "read_mapping_page(mapping, index, NULL)", but with |
|
* any new page allocations done using the specified allocation flags. |
|
* |
|
* If the page does not get brought uptodate, return -EIO. |
|
* |
|
* Return: up to date page on success, ERR_PTR() on failure. |
|
*/ |
|
struct page *read_cache_page_gfp(struct address_space *mapping, |
|
pgoff_t index, |
|
gfp_t gfp) |
|
{ |
|
return do_read_cache_page(mapping, index, NULL, NULL, gfp); |
|
} |
|
EXPORT_SYMBOL(read_cache_page_gfp); |
|
|
|
int pagecache_write_begin(struct file *file, struct address_space *mapping, |
|
loff_t pos, unsigned len, unsigned flags, |
|
struct page **pagep, void **fsdata) |
|
{ |
|
const struct address_space_operations *aops = mapping->a_ops; |
|
|
|
return aops->write_begin(file, mapping, pos, len, flags, |
|
pagep, fsdata); |
|
} |
|
EXPORT_SYMBOL(pagecache_write_begin); |
|
|
|
int pagecache_write_end(struct file *file, struct address_space *mapping, |
|
loff_t pos, unsigned len, unsigned copied, |
|
struct page *page, void *fsdata) |
|
{ |
|
const struct address_space_operations *aops = mapping->a_ops; |
|
|
|
return aops->write_end(file, mapping, pos, len, copied, page, fsdata); |
|
} |
|
EXPORT_SYMBOL(pagecache_write_end); |
|
|
|
/* |
|
* Warn about a page cache invalidation failure during a direct I/O write. |
|
*/ |
|
void dio_warn_stale_pagecache(struct file *filp) |
|
{ |
|
static DEFINE_RATELIMIT_STATE(_rs, 86400 * HZ, DEFAULT_RATELIMIT_BURST); |
|
char pathname[128]; |
|
char *path; |
|
|
|
errseq_set(&filp->f_mapping->wb_err, -EIO); |
|
if (__ratelimit(&_rs)) { |
|
path = file_path(filp, pathname, sizeof(pathname)); |
|
if (IS_ERR(path)) |
|
path = "(unknown)"; |
|
pr_crit("Page cache invalidation failure on direct I/O. Possible data corruption due to collision with buffered I/O!\n"); |
|
pr_crit("File: %s PID: %d Comm: %.20s\n", path, current->pid, |
|
current->comm); |
|
} |
|
} |
|
|
|
ssize_t |
|
generic_file_direct_write(struct kiocb *iocb, struct iov_iter *from) |
|
{ |
|
struct file *file = iocb->ki_filp; |
|
struct address_space *mapping = file->f_mapping; |
|
struct inode *inode = mapping->host; |
|
loff_t pos = iocb->ki_pos; |
|
ssize_t written; |
|
size_t write_len; |
|
pgoff_t end; |
|
|
|
write_len = iov_iter_count(from); |
|
end = (pos + write_len - 1) >> PAGE_SHIFT; |
|
|
|
if (iocb->ki_flags & IOCB_NOWAIT) { |
|
/* If there are pages to writeback, return */ |
|
if (filemap_range_has_page(file->f_mapping, pos, |
|
pos + write_len - 1)) |
|
return -EAGAIN; |
|
} else { |
|
written = filemap_write_and_wait_range(mapping, pos, |
|
pos + write_len - 1); |
|
if (written) |
|
goto out; |
|
} |
|
|
|
/* |
|
* After a write we want buffered reads to be sure to go to disk to get |
|
* the new data. We invalidate clean cached page from the region we're |
|
* about to write. We do this *before* the write so that we can return |
|
* without clobbering -EIOCBQUEUED from ->direct_IO(). |
|
*/ |
|
written = invalidate_inode_pages2_range(mapping, |
|
pos >> PAGE_SHIFT, end); |
|
/* |
|
* If a page can not be invalidated, return 0 to fall back |
|
* to buffered write. |
|
*/ |
|
if (written) { |
|
if (written == -EBUSY) |
|
return 0; |
|
goto out; |
|
} |
|
|
|
written = mapping->a_ops->direct_IO(iocb, from); |
|
|
|
/* |
|
* Finally, try again to invalidate clean pages which might have been |
|
* cached by non-direct readahead, or faulted in by get_user_pages() |
|
* if the source of the write was an mmap'ed region of the file |
|
* we're writing. Either one is a pretty crazy thing to do, |
|
* so we don't support it 100%. If this invalidation |
|
* fails, tough, the write still worked... |
|
* |
|
* Most of the time we do not need this since dio_complete() will do |
|
* the invalidation for us. However there are some file systems that |
|
* do not end up with dio_complete() being called, so let's not break |
|
* them by removing it completely. |
|
* |
|
* Noticeable example is a blkdev_direct_IO(). |
|
* |
|
* Skip invalidation for async writes or if mapping has no pages. |
|
*/ |
|
if (written > 0 && mapping->nrpages && |
|
invalidate_inode_pages2_range(mapping, pos >> PAGE_SHIFT, end)) |
|
dio_warn_stale_pagecache(file); |
|
|
|
if (written > 0) { |
|
pos += written; |
|
write_len -= written; |
|
if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) { |
|
i_size_write(inode, pos); |
|
mark_inode_dirty(inode); |
|
} |
|
iocb->ki_pos = pos; |
|
} |
|
if (written != -EIOCBQUEUED) |
|
iov_iter_revert(from, write_len - iov_iter_count(from)); |
|
out: |
|
return written; |
|
} |
|
EXPORT_SYMBOL(generic_file_direct_write); |
|
|
|
/* |
|
* Find or create a page at the given pagecache position. Return the locked |
|
* page. This function is specifically for buffered writes. |
|
*/ |
|
struct page *grab_cache_page_write_begin(struct address_space *mapping, |
|
pgoff_t index, unsigned flags) |
|
{ |
|
struct page *page; |
|
int fgp_flags = FGP_LOCK|FGP_WRITE|FGP_CREAT; |
|
|
|
if (flags & AOP_FLAG_NOFS) |
|
fgp_flags |= FGP_NOFS; |
|
|
|
page = pagecache_get_page(mapping, index, fgp_flags, |
|
mapping_gfp_mask(mapping)); |
|
if (page) |
|
wait_for_stable_page(page); |
|
|
|
return page; |
|
} |
|
EXPORT_SYMBOL(grab_cache_page_write_begin); |
|
|
|
ssize_t generic_perform_write(struct file *file, |
|
struct iov_iter *i, loff_t pos) |
|
{ |
|
struct address_space *mapping = file->f_mapping; |
|
const struct address_space_operations *a_ops = mapping->a_ops; |
|
long status = 0; |
|
ssize_t written = 0; |
|
unsigned int flags = 0; |
|
|
|
do { |
|
struct page *page; |
|
unsigned long offset; /* Offset into pagecache page */ |
|
unsigned long bytes; /* Bytes to write to page */ |
|
size_t copied; /* Bytes copied from user */ |
|
void *fsdata; |
|
|
|
offset = (pos & (PAGE_SIZE - 1)); |
|
bytes = min_t(unsigned long, PAGE_SIZE - offset, |
|
iov_iter_count(i)); |
|
|
|
again: |
|
/* |
|
* Bring in the user page that we will copy from _first_. |
|
* Otherwise there's a nasty deadlock on copying from the |
|
* same page as we're writing to, without it being marked |
|
* up-to-date. |
|
* |
|
* Not only is this an optimisation, but it is also required |
|
* to check that the address is actually valid, when atomic |
|
* usercopies are used, below. |
|
*/ |
|
if (unlikely(iov_iter_fault_in_readable(i, bytes))) { |
|
status = -EFAULT; |
|
break; |
|
} |
|
|
|
if (fatal_signal_pending(current)) { |
|
status = -EINTR; |
|
break; |
|
} |
|
|
|
status = a_ops->write_begin(file, mapping, pos, bytes, flags, |
|
&page, &fsdata); |
|
if (unlikely(status < 0)) |
|
break; |
|
|
|
if (mapping_writably_mapped(mapping)) |
|
flush_dcache_page(page); |
|
|
|
copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes); |
|
flush_dcache_page(page); |
|
|
|
status = a_ops->write_end(file, mapping, pos, bytes, copied, |
|
page, fsdata); |
|
if (unlikely(status < 0)) |
|
break; |
|
copied = status; |
|
|
|
cond_resched(); |
|
|
|
iov_iter_advance(i, copied); |
|
if (unlikely(copied == 0)) { |
|
/* |
|
* If we were unable to copy any data at all, we must |
|
* fall back to a single segment length write. |
|
* |
|
* If we didn't fallback here, we could livelock |
|
* because not all segments in the iov can be copied at |
|
* once without a pagefault. |
|
*/ |
|
bytes = min_t(unsigned long, PAGE_SIZE - offset, |
|
iov_iter_single_seg_count(i)); |
|
goto again; |
|
} |
|
pos += copied; |
|
written += copied; |
|
|
|
balance_dirty_pages_ratelimited(mapping); |
|
} while (iov_iter_count(i)); |
|
|
|
return written ? written : status; |
|
} |
|
EXPORT_SYMBOL(generic_perform_write); |
|
|
|
/** |
|
* __generic_file_write_iter - write data to a file |
|
* @iocb: IO state structure (file, offset, etc.) |
|
* @from: iov_iter with data to write |
|
* |
|
* This function does all the work needed for actually writing data to a |
|
* file. It does all basic checks, removes SUID from the file, updates |
|
* modification times and calls proper subroutines depending on whether we |
|
* do direct IO or a standard buffered write. |
|
* |
|
* It expects i_mutex to be grabbed unless we work on a block device or similar |
|
* object which does not need locking at all. |
|
* |
|
* This function does *not* take care of syncing data in case of O_SYNC write. |
|
* A caller has to handle it. This is mainly due to the fact that we want to |
|
* avoid syncing under i_mutex. |
|
* |
|
* Return: |
|
* * number of bytes written, even for truncated writes |
|
* * negative error code if no data has been written at all |
|
*/ |
|
ssize_t __generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from) |
|
{ |
|
struct file *file = iocb->ki_filp; |
|
struct address_space * mapping = file->f_mapping; |
|
struct inode *inode = mapping->host; |
|
ssize_t written = 0; |
|
ssize_t err; |
|
ssize_t status; |
|
|
|
/* We can write back this queue in page reclaim */ |
|
current->backing_dev_info = inode_to_bdi(inode); |
|
err = file_remove_privs(file); |
|
if (err) |
|
goto out; |
|
|
|
err = file_update_time(file); |
|
if (err) |
|
goto out; |
|
|
|
if (iocb->ki_flags & IOCB_DIRECT) { |
|
loff_t pos, endbyte; |
|
|
|
written = generic_file_direct_write(iocb, from); |
|
/* |
|
* If the write stopped short of completing, fall back to |
|
* buffered writes. Some filesystems do this for writes to |
|
* holes, for example. For DAX files, a buffered write will |
|
* not succeed (even if it did, DAX does not handle dirty |
|
* page-cache pages correctly). |
|
*/ |
|
if (written < 0 || !iov_iter_count(from) || IS_DAX(inode)) |
|
goto out; |
|
|
|
status = generic_perform_write(file, from, pos = iocb->ki_pos); |
|
/* |
|
* If generic_perform_write() returned a synchronous error |
|
* then we want to return the number of bytes which were |
|
* direct-written, or the error code if that was zero. Note |
|
* that this differs from normal direct-io semantics, which |
|
* will return -EFOO even if some bytes were written. |
|
*/ |
|
if (unlikely(status < 0)) { |
|
err = status; |
|
goto out; |
|
} |
|
/* |
|
* We need to ensure that the page cache pages are written to |
|
* disk and invalidated to preserve the expected O_DIRECT |
|
* semantics. |
|
*/ |
|
endbyte = pos + status - 1; |
|
err = filemap_write_and_wait_range(mapping, pos, endbyte); |
|
if (err == 0) { |
|
iocb->ki_pos = endbyte + 1; |
|
written += status; |
|
invalidate_mapping_pages(mapping, |
|
pos >> PAGE_SHIFT, |
|
endbyte >> PAGE_SHIFT); |
|
} else { |
|
/* |
|
* We don't know how much we wrote, so just return |
|
* the number of bytes which were direct-written |
|
*/ |
|
} |
|
} else { |
|
written = generic_perform_write(file, from, iocb->ki_pos); |
|
if (likely(written > 0)) |
|
iocb->ki_pos += written; |
|
} |
|
out: |
|
current->backing_dev_info = NULL; |
|
return written ? written : err; |
|
} |
|
EXPORT_SYMBOL(__generic_file_write_iter); |
|
|
|
/** |
|
* generic_file_write_iter - write data to a file |
|
* @iocb: IO state structure |
|
* @from: iov_iter with data to write |
|
* |
|
* This is a wrapper around __generic_file_write_iter() to be used by most |
|
* filesystems. It takes care of syncing the file in case of O_SYNC file |
|
* and acquires i_mutex as needed. |
|
* Return: |
|
* * negative error code if no data has been written at all of |
|
* vfs_fsync_range() failed for a synchronous write |
|
* * number of bytes written, even for truncated writes |
|
*/ |
|
ssize_t generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from) |
|
{ |
|
struct file *file = iocb->ki_filp; |
|
struct inode *inode = file->f_mapping->host; |
|
ssize_t ret; |
|
|
|
inode_lock(inode); |
|
ret = generic_write_checks(iocb, from); |
|
if (ret > 0) |
|
ret = __generic_file_write_iter(iocb, from); |
|
inode_unlock(inode); |
|
|
|
if (ret > 0) |
|
ret = generic_write_sync(iocb, ret); |
|
return ret; |
|
} |
|
EXPORT_SYMBOL(generic_file_write_iter); |
|
|
|
/** |
|
* try_to_release_page() - release old fs-specific metadata on a page |
|
* |
|
* @page: the page which the kernel is trying to free |
|
* @gfp_mask: memory allocation flags (and I/O mode) |
|
* |
|
* The address_space is to try to release any data against the page |
|
* (presumably at page->private). |
|
* |
|
* This may also be called if PG_fscache is set on a page, indicating that the |
|
* page is known to the local caching routines. |
|
* |
|
* The @gfp_mask argument specifies whether I/O may be performed to release |
|
* this page (__GFP_IO), and whether the call may block (__GFP_RECLAIM & __GFP_FS). |
|
* |
|
* Return: %1 if the release was successful, otherwise return zero. |
|
*/ |
|
int try_to_release_page(struct page *page, gfp_t gfp_mask) |
|
{ |
|
struct address_space * const mapping = page->mapping; |
|
|
|
BUG_ON(!PageLocked(page)); |
|
if (PageWriteback(page)) |
|
return 0; |
|
|
|
if (mapping && mapping->a_ops->releasepage) |
|
return mapping->a_ops->releasepage(page, gfp_mask); |
|
return try_to_free_buffers(page); |
|
} |
|
|
|
EXPORT_SYMBOL(try_to_release_page);
|
|
|