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2571 lines
67 KiB
2571 lines
67 KiB
// SPDX-License-Identifier: GPL-2.0 |
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/* |
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* Memory Migration functionality - linux/mm/migrate.c |
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* |
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* Copyright (C) 2006 Silicon Graphics, Inc., Christoph Lameter |
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* |
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* Page migration was first developed in the context of the memory hotplug |
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* project. The main authors of the migration code are: |
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* |
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* IWAMOTO Toshihiro <[email protected]> |
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* Hirokazu Takahashi <[email protected]> |
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* Dave Hansen <[email protected]> |
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* Christoph Lameter |
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*/ |
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|
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#include <linux/migrate.h> |
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#include <linux/export.h> |
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#include <linux/swap.h> |
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#include <linux/swapops.h> |
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#include <linux/pagemap.h> |
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#include <linux/buffer_head.h> |
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#include <linux/mm_inline.h> |
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#include <linux/nsproxy.h> |
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#include <linux/pagevec.h> |
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#include <linux/ksm.h> |
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#include <linux/rmap.h> |
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#include <linux/topology.h> |
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#include <linux/cpu.h> |
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#include <linux/cpuset.h> |
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#include <linux/writeback.h> |
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#include <linux/mempolicy.h> |
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#include <linux/vmalloc.h> |
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#include <linux/security.h> |
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#include <linux/backing-dev.h> |
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#include <linux/compaction.h> |
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#include <linux/syscalls.h> |
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#include <linux/compat.h> |
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#include <linux/hugetlb.h> |
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#include <linux/hugetlb_cgroup.h> |
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#include <linux/gfp.h> |
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#include <linux/pfn_t.h> |
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#include <linux/memremap.h> |
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#include <linux/userfaultfd_k.h> |
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#include <linux/balloon_compaction.h> |
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#include <linux/page_idle.h> |
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#include <linux/page_owner.h> |
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#include <linux/sched/mm.h> |
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#include <linux/ptrace.h> |
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#include <linux/oom.h> |
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#include <linux/memory.h> |
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#include <linux/random.h> |
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#include <linux/sched/sysctl.h> |
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|
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#include <asm/tlbflush.h> |
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|
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#include <trace/events/migrate.h> |
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|
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#include "internal.h" |
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|
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int isolate_movable_page(struct page *page, isolate_mode_t mode) |
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{ |
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struct address_space *mapping; |
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|
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/* |
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* Avoid burning cycles with pages that are yet under __free_pages(), |
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* or just got freed under us. |
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* |
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* In case we 'win' a race for a movable page being freed under us and |
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* raise its refcount preventing __free_pages() from doing its job |
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* the put_page() at the end of this block will take care of |
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* release this page, thus avoiding a nasty leakage. |
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*/ |
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if (unlikely(!get_page_unless_zero(page))) |
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goto out; |
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|
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/* |
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* Check PageMovable before holding a PG_lock because page's owner |
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* assumes anybody doesn't touch PG_lock of newly allocated page |
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* so unconditionally grabbing the lock ruins page's owner side. |
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*/ |
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if (unlikely(!__PageMovable(page))) |
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goto out_putpage; |
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/* |
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* As movable pages are not isolated from LRU lists, concurrent |
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* compaction threads can race against page migration functions |
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* as well as race against the releasing a page. |
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* |
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* In order to avoid having an already isolated movable page |
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* being (wrongly) re-isolated while it is under migration, |
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* or to avoid attempting to isolate pages being released, |
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* lets be sure we have the page lock |
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* before proceeding with the movable page isolation steps. |
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*/ |
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if (unlikely(!trylock_page(page))) |
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goto out_putpage; |
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|
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if (!PageMovable(page) || PageIsolated(page)) |
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goto out_no_isolated; |
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|
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mapping = page_mapping(page); |
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VM_BUG_ON_PAGE(!mapping, page); |
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|
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if (!mapping->a_ops->isolate_page(page, mode)) |
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goto out_no_isolated; |
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|
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/* Driver shouldn't use PG_isolated bit of page->flags */ |
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WARN_ON_ONCE(PageIsolated(page)); |
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SetPageIsolated(page); |
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unlock_page(page); |
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|
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return 0; |
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|
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out_no_isolated: |
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unlock_page(page); |
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out_putpage: |
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put_page(page); |
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out: |
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return -EBUSY; |
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} |
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|
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static void putback_movable_page(struct page *page) |
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{ |
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struct address_space *mapping; |
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|
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mapping = page_mapping(page); |
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mapping->a_ops->putback_page(page); |
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ClearPageIsolated(page); |
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} |
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|
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/* |
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* Put previously isolated pages back onto the appropriate lists |
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* from where they were once taken off for compaction/migration. |
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* |
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* This function shall be used whenever the isolated pageset has been |
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* built from lru, balloon, hugetlbfs page. See isolate_migratepages_range() |
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* and isolate_huge_page(). |
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*/ |
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void putback_movable_pages(struct list_head *l) |
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{ |
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struct page *page; |
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struct page *page2; |
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|
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list_for_each_entry_safe(page, page2, l, lru) { |
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if (unlikely(PageHuge(page))) { |
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putback_active_hugepage(page); |
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continue; |
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} |
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list_del(&page->lru); |
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/* |
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* We isolated non-lru movable page so here we can use |
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* __PageMovable because LRU page's mapping cannot have |
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* PAGE_MAPPING_MOVABLE. |
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*/ |
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if (unlikely(__PageMovable(page))) { |
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VM_BUG_ON_PAGE(!PageIsolated(page), page); |
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lock_page(page); |
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if (PageMovable(page)) |
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putback_movable_page(page); |
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else |
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ClearPageIsolated(page); |
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unlock_page(page); |
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put_page(page); |
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} else { |
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mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON + |
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page_is_file_lru(page), -thp_nr_pages(page)); |
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putback_lru_page(page); |
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} |
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} |
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} |
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|
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/* |
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* Restore a potential migration pte to a working pte entry |
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*/ |
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static bool remove_migration_pte(struct folio *folio, |
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struct vm_area_struct *vma, unsigned long addr, void *old) |
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{ |
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DEFINE_FOLIO_VMA_WALK(pvmw, old, vma, addr, PVMW_SYNC | PVMW_MIGRATION); |
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|
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while (page_vma_mapped_walk(&pvmw)) { |
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pte_t pte; |
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swp_entry_t entry; |
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struct page *new; |
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unsigned long idx = 0; |
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|
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/* pgoff is invalid for ksm pages, but they are never large */ |
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if (folio_test_large(folio) && !folio_test_hugetlb(folio)) |
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idx = linear_page_index(vma, pvmw.address) - pvmw.pgoff; |
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new = folio_page(folio, idx); |
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|
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#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION |
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/* PMD-mapped THP migration entry */ |
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if (!pvmw.pte) { |
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VM_BUG_ON_FOLIO(folio_test_hugetlb(folio) || |
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!folio_test_pmd_mappable(folio), folio); |
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remove_migration_pmd(&pvmw, new); |
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continue; |
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} |
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#endif |
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|
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folio_get(folio); |
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pte = pte_mkold(mk_pte(new, READ_ONCE(vma->vm_page_prot))); |
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if (pte_swp_soft_dirty(*pvmw.pte)) |
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pte = pte_mksoft_dirty(pte); |
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|
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/* |
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* Recheck VMA as permissions can change since migration started |
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*/ |
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entry = pte_to_swp_entry(*pvmw.pte); |
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if (is_writable_migration_entry(entry)) |
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pte = maybe_mkwrite(pte, vma); |
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else if (pte_swp_uffd_wp(*pvmw.pte)) |
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pte = pte_mkuffd_wp(pte); |
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|
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if (unlikely(is_device_private_page(new))) { |
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if (pte_write(pte)) |
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entry = make_writable_device_private_entry( |
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page_to_pfn(new)); |
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else |
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entry = make_readable_device_private_entry( |
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page_to_pfn(new)); |
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pte = swp_entry_to_pte(entry); |
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if (pte_swp_soft_dirty(*pvmw.pte)) |
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pte = pte_swp_mksoft_dirty(pte); |
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if (pte_swp_uffd_wp(*pvmw.pte)) |
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pte = pte_swp_mkuffd_wp(pte); |
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} |
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#ifdef CONFIG_HUGETLB_PAGE |
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if (folio_test_hugetlb(folio)) { |
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unsigned int shift = huge_page_shift(hstate_vma(vma)); |
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|
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pte = pte_mkhuge(pte); |
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pte = arch_make_huge_pte(pte, shift, vma->vm_flags); |
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if (folio_test_anon(folio)) |
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hugepage_add_anon_rmap(new, vma, pvmw.address); |
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else |
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page_dup_rmap(new, true); |
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set_huge_pte_at(vma->vm_mm, pvmw.address, pvmw.pte, pte); |
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} else |
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#endif |
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{ |
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if (folio_test_anon(folio)) |
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page_add_anon_rmap(new, vma, pvmw.address, false); |
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else |
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page_add_file_rmap(new, vma, false); |
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set_pte_at(vma->vm_mm, pvmw.address, pvmw.pte, pte); |
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} |
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if (vma->vm_flags & VM_LOCKED) |
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mlock_page_drain_local(); |
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trace_remove_migration_pte(pvmw.address, pte_val(pte), |
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compound_order(new)); |
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/* No need to invalidate - it was non-present before */ |
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update_mmu_cache(vma, pvmw.address, pvmw.pte); |
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} |
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return true; |
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} |
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/* |
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* Get rid of all migration entries and replace them by |
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* references to the indicated page. |
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*/ |
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void remove_migration_ptes(struct folio *src, struct folio *dst, bool locked) |
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{ |
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struct rmap_walk_control rwc = { |
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.rmap_one = remove_migration_pte, |
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.arg = src, |
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}; |
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if (locked) |
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rmap_walk_locked(dst, &rwc); |
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else |
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rmap_walk(dst, &rwc); |
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} |
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/* |
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* Something used the pte of a page under migration. We need to |
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* get to the page and wait until migration is finished. |
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* When we return from this function the fault will be retried. |
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*/ |
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void __migration_entry_wait(struct mm_struct *mm, pte_t *ptep, |
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spinlock_t *ptl) |
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{ |
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pte_t pte; |
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swp_entry_t entry; |
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spin_lock(ptl); |
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pte = *ptep; |
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if (!is_swap_pte(pte)) |
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goto out; |
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entry = pte_to_swp_entry(pte); |
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if (!is_migration_entry(entry)) |
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goto out; |
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migration_entry_wait_on_locked(entry, ptep, ptl); |
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return; |
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out: |
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pte_unmap_unlock(ptep, ptl); |
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} |
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void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd, |
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unsigned long address) |
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{ |
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spinlock_t *ptl = pte_lockptr(mm, pmd); |
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pte_t *ptep = pte_offset_map(pmd, address); |
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__migration_entry_wait(mm, ptep, ptl); |
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} |
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void migration_entry_wait_huge(struct vm_area_struct *vma, |
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struct mm_struct *mm, pte_t *pte) |
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{ |
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spinlock_t *ptl = huge_pte_lockptr(hstate_vma(vma), mm, pte); |
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__migration_entry_wait(mm, pte, ptl); |
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} |
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#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION |
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void pmd_migration_entry_wait(struct mm_struct *mm, pmd_t *pmd) |
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{ |
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spinlock_t *ptl; |
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ptl = pmd_lock(mm, pmd); |
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if (!is_pmd_migration_entry(*pmd)) |
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goto unlock; |
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migration_entry_wait_on_locked(pmd_to_swp_entry(*pmd), NULL, ptl); |
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return; |
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unlock: |
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spin_unlock(ptl); |
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} |
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#endif |
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static int expected_page_refs(struct address_space *mapping, struct page *page) |
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{ |
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int expected_count = 1; |
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if (mapping) |
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expected_count += compound_nr(page) + page_has_private(page); |
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return expected_count; |
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} |
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|
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/* |
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* Replace the page in the mapping. |
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* |
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* The number of remaining references must be: |
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* 1 for anonymous pages without a mapping |
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* 2 for pages with a mapping |
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* 3 for pages with a mapping and PagePrivate/PagePrivate2 set. |
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*/ |
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int folio_migrate_mapping(struct address_space *mapping, |
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struct folio *newfolio, struct folio *folio, int extra_count) |
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{ |
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XA_STATE(xas, &mapping->i_pages, folio_index(folio)); |
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struct zone *oldzone, *newzone; |
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int dirty; |
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int expected_count = expected_page_refs(mapping, &folio->page) + extra_count; |
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long nr = folio_nr_pages(folio); |
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|
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if (!mapping) { |
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/* Anonymous page without mapping */ |
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if (folio_ref_count(folio) != expected_count) |
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return -EAGAIN; |
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|
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/* No turning back from here */ |
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newfolio->index = folio->index; |
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newfolio->mapping = folio->mapping; |
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if (folio_test_swapbacked(folio)) |
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__folio_set_swapbacked(newfolio); |
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return MIGRATEPAGE_SUCCESS; |
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} |
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oldzone = folio_zone(folio); |
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newzone = folio_zone(newfolio); |
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|
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xas_lock_irq(&xas); |
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if (!folio_ref_freeze(folio, expected_count)) { |
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xas_unlock_irq(&xas); |
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return -EAGAIN; |
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} |
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|
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/* |
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* Now we know that no one else is looking at the folio: |
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* no turning back from here. |
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*/ |
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newfolio->index = folio->index; |
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newfolio->mapping = folio->mapping; |
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folio_ref_add(newfolio, nr); /* add cache reference */ |
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if (folio_test_swapbacked(folio)) { |
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__folio_set_swapbacked(newfolio); |
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if (folio_test_swapcache(folio)) { |
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folio_set_swapcache(newfolio); |
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newfolio->private = folio_get_private(folio); |
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} |
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} else { |
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VM_BUG_ON_FOLIO(folio_test_swapcache(folio), folio); |
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} |
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|
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/* Move dirty while page refs frozen and newpage not yet exposed */ |
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dirty = folio_test_dirty(folio); |
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if (dirty) { |
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folio_clear_dirty(folio); |
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folio_set_dirty(newfolio); |
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} |
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|
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xas_store(&xas, newfolio); |
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|
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/* |
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* Drop cache reference from old page by unfreezing |
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* to one less reference. |
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* We know this isn't the last reference. |
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*/ |
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folio_ref_unfreeze(folio, expected_count - nr); |
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|
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xas_unlock(&xas); |
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/* Leave irq disabled to prevent preemption while updating stats */ |
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|
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/* |
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* If moved to a different zone then also account |
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* the page for that zone. Other VM counters will be |
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* taken care of when we establish references to the |
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* new page and drop references to the old page. |
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* |
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* Note that anonymous pages are accounted for |
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* via NR_FILE_PAGES and NR_ANON_MAPPED if they |
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* are mapped to swap space. |
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*/ |
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if (newzone != oldzone) { |
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struct lruvec *old_lruvec, *new_lruvec; |
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struct mem_cgroup *memcg; |
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|
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memcg = folio_memcg(folio); |
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old_lruvec = mem_cgroup_lruvec(memcg, oldzone->zone_pgdat); |
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new_lruvec = mem_cgroup_lruvec(memcg, newzone->zone_pgdat); |
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|
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__mod_lruvec_state(old_lruvec, NR_FILE_PAGES, -nr); |
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__mod_lruvec_state(new_lruvec, NR_FILE_PAGES, nr); |
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if (folio_test_swapbacked(folio) && !folio_test_swapcache(folio)) { |
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__mod_lruvec_state(old_lruvec, NR_SHMEM, -nr); |
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__mod_lruvec_state(new_lruvec, NR_SHMEM, nr); |
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} |
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#ifdef CONFIG_SWAP |
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if (folio_test_swapcache(folio)) { |
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__mod_lruvec_state(old_lruvec, NR_SWAPCACHE, -nr); |
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__mod_lruvec_state(new_lruvec, NR_SWAPCACHE, nr); |
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} |
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#endif |
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if (dirty && mapping_can_writeback(mapping)) { |
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__mod_lruvec_state(old_lruvec, NR_FILE_DIRTY, -nr); |
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__mod_zone_page_state(oldzone, NR_ZONE_WRITE_PENDING, -nr); |
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__mod_lruvec_state(new_lruvec, NR_FILE_DIRTY, nr); |
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__mod_zone_page_state(newzone, NR_ZONE_WRITE_PENDING, nr); |
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} |
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} |
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local_irq_enable(); |
|
|
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return MIGRATEPAGE_SUCCESS; |
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} |
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EXPORT_SYMBOL(folio_migrate_mapping); |
|
|
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/* |
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* The expected number of remaining references is the same as that |
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* of folio_migrate_mapping(). |
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*/ |
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int migrate_huge_page_move_mapping(struct address_space *mapping, |
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struct page *newpage, struct page *page) |
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{ |
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XA_STATE(xas, &mapping->i_pages, page_index(page)); |
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int expected_count; |
|
|
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xas_lock_irq(&xas); |
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expected_count = 2 + page_has_private(page); |
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if (page_count(page) != expected_count || xas_load(&xas) != page) { |
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xas_unlock_irq(&xas); |
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return -EAGAIN; |
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} |
|
|
|
if (!page_ref_freeze(page, expected_count)) { |
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xas_unlock_irq(&xas); |
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return -EAGAIN; |
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} |
|
|
|
newpage->index = page->index; |
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newpage->mapping = page->mapping; |
|
|
|
get_page(newpage); |
|
|
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xas_store(&xas, newpage); |
|
|
|
page_ref_unfreeze(page, expected_count - 1); |
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|
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xas_unlock_irq(&xas); |
|
|
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return MIGRATEPAGE_SUCCESS; |
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} |
|
|
|
/* |
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* Copy the flags and some other ancillary information |
|
*/ |
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void folio_migrate_flags(struct folio *newfolio, struct folio *folio) |
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{ |
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int cpupid; |
|
|
|
if (folio_test_error(folio)) |
|
folio_set_error(newfolio); |
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if (folio_test_referenced(folio)) |
|
folio_set_referenced(newfolio); |
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if (folio_test_uptodate(folio)) |
|
folio_mark_uptodate(newfolio); |
|
if (folio_test_clear_active(folio)) { |
|
VM_BUG_ON_FOLIO(folio_test_unevictable(folio), folio); |
|
folio_set_active(newfolio); |
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} else if (folio_test_clear_unevictable(folio)) |
|
folio_set_unevictable(newfolio); |
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if (folio_test_workingset(folio)) |
|
folio_set_workingset(newfolio); |
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if (folio_test_checked(folio)) |
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folio_set_checked(newfolio); |
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if (folio_test_mappedtodisk(folio)) |
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folio_set_mappedtodisk(newfolio); |
|
|
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/* Move dirty on pages not done by folio_migrate_mapping() */ |
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if (folio_test_dirty(folio)) |
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folio_set_dirty(newfolio); |
|
|
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if (folio_test_young(folio)) |
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folio_set_young(newfolio); |
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if (folio_test_idle(folio)) |
|
folio_set_idle(newfolio); |
|
|
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/* |
|
* Copy NUMA information to the new page, to prevent over-eager |
|
* future migrations of this same page. |
|
*/ |
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cpupid = page_cpupid_xchg_last(&folio->page, -1); |
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page_cpupid_xchg_last(&newfolio->page, cpupid); |
|
|
|
folio_migrate_ksm(newfolio, folio); |
|
/* |
|
* Please do not reorder this without considering how mm/ksm.c's |
|
* get_ksm_page() depends upon ksm_migrate_page() and PageSwapCache(). |
|
*/ |
|
if (folio_test_swapcache(folio)) |
|
folio_clear_swapcache(folio); |
|
folio_clear_private(folio); |
|
|
|
/* page->private contains hugetlb specific flags */ |
|
if (!folio_test_hugetlb(folio)) |
|
folio->private = NULL; |
|
|
|
/* |
|
* If any waiters have accumulated on the new page then |
|
* wake them up. |
|
*/ |
|
if (folio_test_writeback(newfolio)) |
|
folio_end_writeback(newfolio); |
|
|
|
/* |
|
* PG_readahead shares the same bit with PG_reclaim. The above |
|
* end_page_writeback() may clear PG_readahead mistakenly, so set the |
|
* bit after that. |
|
*/ |
|
if (folio_test_readahead(folio)) |
|
folio_set_readahead(newfolio); |
|
|
|
folio_copy_owner(newfolio, folio); |
|
|
|
if (!folio_test_hugetlb(folio)) |
|
mem_cgroup_migrate(folio, newfolio); |
|
} |
|
EXPORT_SYMBOL(folio_migrate_flags); |
|
|
|
void folio_migrate_copy(struct folio *newfolio, struct folio *folio) |
|
{ |
|
folio_copy(newfolio, folio); |
|
folio_migrate_flags(newfolio, folio); |
|
} |
|
EXPORT_SYMBOL(folio_migrate_copy); |
|
|
|
/************************************************************ |
|
* Migration functions |
|
***********************************************************/ |
|
|
|
/* |
|
* Common logic to directly migrate a single LRU page suitable for |
|
* pages that do not use PagePrivate/PagePrivate2. |
|
* |
|
* Pages are locked upon entry and exit. |
|
*/ |
|
int migrate_page(struct address_space *mapping, |
|
struct page *newpage, struct page *page, |
|
enum migrate_mode mode) |
|
{ |
|
struct folio *newfolio = page_folio(newpage); |
|
struct folio *folio = page_folio(page); |
|
int rc; |
|
|
|
BUG_ON(folio_test_writeback(folio)); /* Writeback must be complete */ |
|
|
|
rc = folio_migrate_mapping(mapping, newfolio, folio, 0); |
|
|
|
if (rc != MIGRATEPAGE_SUCCESS) |
|
return rc; |
|
|
|
if (mode != MIGRATE_SYNC_NO_COPY) |
|
folio_migrate_copy(newfolio, folio); |
|
else |
|
folio_migrate_flags(newfolio, folio); |
|
return MIGRATEPAGE_SUCCESS; |
|
} |
|
EXPORT_SYMBOL(migrate_page); |
|
|
|
#ifdef CONFIG_BLOCK |
|
/* Returns true if all buffers are successfully locked */ |
|
static bool buffer_migrate_lock_buffers(struct buffer_head *head, |
|
enum migrate_mode mode) |
|
{ |
|
struct buffer_head *bh = head; |
|
|
|
/* Simple case, sync compaction */ |
|
if (mode != MIGRATE_ASYNC) { |
|
do { |
|
lock_buffer(bh); |
|
bh = bh->b_this_page; |
|
|
|
} while (bh != head); |
|
|
|
return true; |
|
} |
|
|
|
/* async case, we cannot block on lock_buffer so use trylock_buffer */ |
|
do { |
|
if (!trylock_buffer(bh)) { |
|
/* |
|
* We failed to lock the buffer and cannot stall in |
|
* async migration. Release the taken locks |
|
*/ |
|
struct buffer_head *failed_bh = bh; |
|
bh = head; |
|
while (bh != failed_bh) { |
|
unlock_buffer(bh); |
|
bh = bh->b_this_page; |
|
} |
|
return false; |
|
} |
|
|
|
bh = bh->b_this_page; |
|
} while (bh != head); |
|
return true; |
|
} |
|
|
|
static int __buffer_migrate_page(struct address_space *mapping, |
|
struct page *newpage, struct page *page, enum migrate_mode mode, |
|
bool check_refs) |
|
{ |
|
struct buffer_head *bh, *head; |
|
int rc; |
|
int expected_count; |
|
|
|
if (!page_has_buffers(page)) |
|
return migrate_page(mapping, newpage, page, mode); |
|
|
|
/* Check whether page does not have extra refs before we do more work */ |
|
expected_count = expected_page_refs(mapping, page); |
|
if (page_count(page) != expected_count) |
|
return -EAGAIN; |
|
|
|
head = page_buffers(page); |
|
if (!buffer_migrate_lock_buffers(head, mode)) |
|
return -EAGAIN; |
|
|
|
if (check_refs) { |
|
bool busy; |
|
bool invalidated = false; |
|
|
|
recheck_buffers: |
|
busy = false; |
|
spin_lock(&mapping->private_lock); |
|
bh = head; |
|
do { |
|
if (atomic_read(&bh->b_count)) { |
|
busy = true; |
|
break; |
|
} |
|
bh = bh->b_this_page; |
|
} while (bh != head); |
|
if (busy) { |
|
if (invalidated) { |
|
rc = -EAGAIN; |
|
goto unlock_buffers; |
|
} |
|
spin_unlock(&mapping->private_lock); |
|
invalidate_bh_lrus(); |
|
invalidated = true; |
|
goto recheck_buffers; |
|
} |
|
} |
|
|
|
rc = migrate_page_move_mapping(mapping, newpage, page, 0); |
|
if (rc != MIGRATEPAGE_SUCCESS) |
|
goto unlock_buffers; |
|
|
|
attach_page_private(newpage, detach_page_private(page)); |
|
|
|
bh = head; |
|
do { |
|
set_bh_page(bh, newpage, bh_offset(bh)); |
|
bh = bh->b_this_page; |
|
|
|
} while (bh != head); |
|
|
|
if (mode != MIGRATE_SYNC_NO_COPY) |
|
migrate_page_copy(newpage, page); |
|
else |
|
migrate_page_states(newpage, page); |
|
|
|
rc = MIGRATEPAGE_SUCCESS; |
|
unlock_buffers: |
|
if (check_refs) |
|
spin_unlock(&mapping->private_lock); |
|
bh = head; |
|
do { |
|
unlock_buffer(bh); |
|
bh = bh->b_this_page; |
|
|
|
} while (bh != head); |
|
|
|
return rc; |
|
} |
|
|
|
/* |
|
* Migration function for pages with buffers. This function can only be used |
|
* if the underlying filesystem guarantees that no other references to "page" |
|
* exist. For example attached buffer heads are accessed only under page lock. |
|
*/ |
|
int buffer_migrate_page(struct address_space *mapping, |
|
struct page *newpage, struct page *page, enum migrate_mode mode) |
|
{ |
|
return __buffer_migrate_page(mapping, newpage, page, mode, false); |
|
} |
|
EXPORT_SYMBOL(buffer_migrate_page); |
|
|
|
/* |
|
* Same as above except that this variant is more careful and checks that there |
|
* are also no buffer head references. This function is the right one for |
|
* mappings where buffer heads are directly looked up and referenced (such as |
|
* block device mappings). |
|
*/ |
|
int buffer_migrate_page_norefs(struct address_space *mapping, |
|
struct page *newpage, struct page *page, enum migrate_mode mode) |
|
{ |
|
return __buffer_migrate_page(mapping, newpage, page, mode, true); |
|
} |
|
#endif |
|
|
|
/* |
|
* Writeback a page to clean the dirty state |
|
*/ |
|
static int writeout(struct address_space *mapping, struct page *page) |
|
{ |
|
struct folio *folio = page_folio(page); |
|
struct writeback_control wbc = { |
|
.sync_mode = WB_SYNC_NONE, |
|
.nr_to_write = 1, |
|
.range_start = 0, |
|
.range_end = LLONG_MAX, |
|
.for_reclaim = 1 |
|
}; |
|
int rc; |
|
|
|
if (!mapping->a_ops->writepage) |
|
/* No write method for the address space */ |
|
return -EINVAL; |
|
|
|
if (!clear_page_dirty_for_io(page)) |
|
/* Someone else already triggered a write */ |
|
return -EAGAIN; |
|
|
|
/* |
|
* A dirty page may imply that the underlying filesystem has |
|
* the page on some queue. So the page must be clean for |
|
* migration. Writeout may mean we loose the lock and the |
|
* page state is no longer what we checked for earlier. |
|
* At this point we know that the migration attempt cannot |
|
* be successful. |
|
*/ |
|
remove_migration_ptes(folio, folio, false); |
|
|
|
rc = mapping->a_ops->writepage(page, &wbc); |
|
|
|
if (rc != AOP_WRITEPAGE_ACTIVATE) |
|
/* unlocked. Relock */ |
|
lock_page(page); |
|
|
|
return (rc < 0) ? -EIO : -EAGAIN; |
|
} |
|
|
|
/* |
|
* Default handling if a filesystem does not provide a migration function. |
|
*/ |
|
static int fallback_migrate_page(struct address_space *mapping, |
|
struct page *newpage, struct page *page, enum migrate_mode mode) |
|
{ |
|
if (PageDirty(page)) { |
|
/* Only writeback pages in full synchronous migration */ |
|
switch (mode) { |
|
case MIGRATE_SYNC: |
|
case MIGRATE_SYNC_NO_COPY: |
|
break; |
|
default: |
|
return -EBUSY; |
|
} |
|
return writeout(mapping, page); |
|
} |
|
|
|
/* |
|
* Buffers may be managed in a filesystem specific way. |
|
* We must have no buffers or drop them. |
|
*/ |
|
if (page_has_private(page) && |
|
!try_to_release_page(page, GFP_KERNEL)) |
|
return mode == MIGRATE_SYNC ? -EAGAIN : -EBUSY; |
|
|
|
return migrate_page(mapping, newpage, page, mode); |
|
} |
|
|
|
/* |
|
* Move a page to a newly allocated page |
|
* The page is locked and all ptes have been successfully removed. |
|
* |
|
* The new page will have replaced the old page if this function |
|
* is successful. |
|
* |
|
* Return value: |
|
* < 0 - error code |
|
* MIGRATEPAGE_SUCCESS - success |
|
*/ |
|
static int move_to_new_page(struct page *newpage, struct page *page, |
|
enum migrate_mode mode) |
|
{ |
|
struct address_space *mapping; |
|
int rc = -EAGAIN; |
|
bool is_lru = !__PageMovable(page); |
|
|
|
VM_BUG_ON_PAGE(!PageLocked(page), page); |
|
VM_BUG_ON_PAGE(!PageLocked(newpage), newpage); |
|
|
|
mapping = page_mapping(page); |
|
|
|
if (likely(is_lru)) { |
|
if (!mapping) |
|
rc = migrate_page(mapping, newpage, page, mode); |
|
else if (mapping->a_ops->migratepage) |
|
/* |
|
* Most pages have a mapping and most filesystems |
|
* provide a migratepage callback. Anonymous pages |
|
* are part of swap space which also has its own |
|
* migratepage callback. This is the most common path |
|
* for page migration. |
|
*/ |
|
rc = mapping->a_ops->migratepage(mapping, newpage, |
|
page, mode); |
|
else |
|
rc = fallback_migrate_page(mapping, newpage, |
|
page, mode); |
|
} else { |
|
/* |
|
* In case of non-lru page, it could be released after |
|
* isolation step. In that case, we shouldn't try migration. |
|
*/ |
|
VM_BUG_ON_PAGE(!PageIsolated(page), page); |
|
if (!PageMovable(page)) { |
|
rc = MIGRATEPAGE_SUCCESS; |
|
ClearPageIsolated(page); |
|
goto out; |
|
} |
|
|
|
rc = mapping->a_ops->migratepage(mapping, newpage, |
|
page, mode); |
|
WARN_ON_ONCE(rc == MIGRATEPAGE_SUCCESS && |
|
!PageIsolated(page)); |
|
} |
|
|
|
/* |
|
* When successful, old pagecache page->mapping must be cleared before |
|
* page is freed; but stats require that PageAnon be left as PageAnon. |
|
*/ |
|
if (rc == MIGRATEPAGE_SUCCESS) { |
|
if (__PageMovable(page)) { |
|
VM_BUG_ON_PAGE(!PageIsolated(page), page); |
|
|
|
/* |
|
* We clear PG_movable under page_lock so any compactor |
|
* cannot try to migrate this page. |
|
*/ |
|
ClearPageIsolated(page); |
|
} |
|
|
|
/* |
|
* Anonymous and movable page->mapping will be cleared by |
|
* free_pages_prepare so don't reset it here for keeping |
|
* the type to work PageAnon, for example. |
|
*/ |
|
if (!PageMappingFlags(page)) |
|
page->mapping = NULL; |
|
|
|
if (likely(!is_zone_device_page(newpage))) |
|
flush_dcache_folio(page_folio(newpage)); |
|
} |
|
out: |
|
return rc; |
|
} |
|
|
|
static int __unmap_and_move(struct page *page, struct page *newpage, |
|
int force, enum migrate_mode mode) |
|
{ |
|
struct folio *folio = page_folio(page); |
|
struct folio *dst = page_folio(newpage); |
|
int rc = -EAGAIN; |
|
bool page_was_mapped = false; |
|
struct anon_vma *anon_vma = NULL; |
|
bool is_lru = !__PageMovable(page); |
|
|
|
if (!trylock_page(page)) { |
|
if (!force || mode == MIGRATE_ASYNC) |
|
goto out; |
|
|
|
/* |
|
* It's not safe for direct compaction to call lock_page. |
|
* For example, during page readahead pages are added locked |
|
* to the LRU. Later, when the IO completes the pages are |
|
* marked uptodate and unlocked. However, the queueing |
|
* could be merging multiple pages for one bio (e.g. |
|
* mpage_readahead). If an allocation happens for the |
|
* second or third page, the process can end up locking |
|
* the same page twice and deadlocking. Rather than |
|
* trying to be clever about what pages can be locked, |
|
* avoid the use of lock_page for direct compaction |
|
* altogether. |
|
*/ |
|
if (current->flags & PF_MEMALLOC) |
|
goto out; |
|
|
|
lock_page(page); |
|
} |
|
|
|
if (PageWriteback(page)) { |
|
/* |
|
* Only in the case of a full synchronous migration is it |
|
* necessary to wait for PageWriteback. In the async case, |
|
* the retry loop is too short and in the sync-light case, |
|
* the overhead of stalling is too much |
|
*/ |
|
switch (mode) { |
|
case MIGRATE_SYNC: |
|
case MIGRATE_SYNC_NO_COPY: |
|
break; |
|
default: |
|
rc = -EBUSY; |
|
goto out_unlock; |
|
} |
|
if (!force) |
|
goto out_unlock; |
|
wait_on_page_writeback(page); |
|
} |
|
|
|
/* |
|
* By try_to_migrate(), page->mapcount goes down to 0 here. In this case, |
|
* we cannot notice that anon_vma is freed while we migrates a page. |
|
* This get_anon_vma() delays freeing anon_vma pointer until the end |
|
* of migration. File cache pages are no problem because of page_lock() |
|
* File Caches may use write_page() or lock_page() in migration, then, |
|
* just care Anon page here. |
|
* |
|
* Only page_get_anon_vma() understands the subtleties of |
|
* getting a hold on an anon_vma from outside one of its mms. |
|
* But if we cannot get anon_vma, then we won't need it anyway, |
|
* because that implies that the anon page is no longer mapped |
|
* (and cannot be remapped so long as we hold the page lock). |
|
*/ |
|
if (PageAnon(page) && !PageKsm(page)) |
|
anon_vma = page_get_anon_vma(page); |
|
|
|
/* |
|
* Block others from accessing the new page when we get around to |
|
* establishing additional references. We are usually the only one |
|
* holding a reference to newpage at this point. We used to have a BUG |
|
* here if trylock_page(newpage) fails, but would like to allow for |
|
* cases where there might be a race with the previous use of newpage. |
|
* This is much like races on refcount of oldpage: just don't BUG(). |
|
*/ |
|
if (unlikely(!trylock_page(newpage))) |
|
goto out_unlock; |
|
|
|
if (unlikely(!is_lru)) { |
|
rc = move_to_new_page(newpage, page, mode); |
|
goto out_unlock_both; |
|
} |
|
|
|
/* |
|
* Corner case handling: |
|
* 1. When a new swap-cache page is read into, it is added to the LRU |
|
* and treated as swapcache but it has no rmap yet. |
|
* Calling try_to_unmap() against a page->mapping==NULL page will |
|
* trigger a BUG. So handle it here. |
|
* 2. An orphaned page (see truncate_cleanup_page) might have |
|
* fs-private metadata. The page can be picked up due to memory |
|
* offlining. Everywhere else except page reclaim, the page is |
|
* invisible to the vm, so the page can not be migrated. So try to |
|
* free the metadata, so the page can be freed. |
|
*/ |
|
if (!page->mapping) { |
|
VM_BUG_ON_PAGE(PageAnon(page), page); |
|
if (page_has_private(page)) { |
|
try_to_free_buffers(page); |
|
goto out_unlock_both; |
|
} |
|
} else if (page_mapped(page)) { |
|
/* Establish migration ptes */ |
|
VM_BUG_ON_PAGE(PageAnon(page) && !PageKsm(page) && !anon_vma, |
|
page); |
|
try_to_migrate(folio, 0); |
|
page_was_mapped = true; |
|
} |
|
|
|
if (!page_mapped(page)) |
|
rc = move_to_new_page(newpage, page, mode); |
|
|
|
/* |
|
* When successful, push newpage to LRU immediately: so that if it |
|
* turns out to be an mlocked page, remove_migration_ptes() will |
|
* automatically build up the correct newpage->mlock_count for it. |
|
* |
|
* We would like to do something similar for the old page, when |
|
* unsuccessful, and other cases when a page has been temporarily |
|
* isolated from the unevictable LRU: but this case is the easiest. |
|
*/ |
|
if (rc == MIGRATEPAGE_SUCCESS) { |
|
lru_cache_add(newpage); |
|
if (page_was_mapped) |
|
lru_add_drain(); |
|
} |
|
|
|
if (page_was_mapped) |
|
remove_migration_ptes(folio, |
|
rc == MIGRATEPAGE_SUCCESS ? dst : folio, false); |
|
|
|
out_unlock_both: |
|
unlock_page(newpage); |
|
out_unlock: |
|
/* Drop an anon_vma reference if we took one */ |
|
if (anon_vma) |
|
put_anon_vma(anon_vma); |
|
unlock_page(page); |
|
out: |
|
/* |
|
* If migration is successful, decrease refcount of the newpage, |
|
* which will not free the page because new page owner increased |
|
* refcounter. |
|
*/ |
|
if (rc == MIGRATEPAGE_SUCCESS) |
|
put_page(newpage); |
|
|
|
return rc; |
|
} |
|
|
|
/* |
|
* Obtain the lock on page, remove all ptes and migrate the page |
|
* to the newly allocated page in newpage. |
|
*/ |
|
static int unmap_and_move(new_page_t get_new_page, |
|
free_page_t put_new_page, |
|
unsigned long private, struct page *page, |
|
int force, enum migrate_mode mode, |
|
enum migrate_reason reason, |
|
struct list_head *ret) |
|
{ |
|
int rc = MIGRATEPAGE_SUCCESS; |
|
struct page *newpage = NULL; |
|
|
|
if (!thp_migration_supported() && PageTransHuge(page)) |
|
return -ENOSYS; |
|
|
|
if (page_count(page) == 1) { |
|
/* page was freed from under us. So we are done. */ |
|
ClearPageActive(page); |
|
ClearPageUnevictable(page); |
|
if (unlikely(__PageMovable(page))) { |
|
lock_page(page); |
|
if (!PageMovable(page)) |
|
ClearPageIsolated(page); |
|
unlock_page(page); |
|
} |
|
goto out; |
|
} |
|
|
|
newpage = get_new_page(page, private); |
|
if (!newpage) |
|
return -ENOMEM; |
|
|
|
rc = __unmap_and_move(page, newpage, force, mode); |
|
if (rc == MIGRATEPAGE_SUCCESS) |
|
set_page_owner_migrate_reason(newpage, reason); |
|
|
|
out: |
|
if (rc != -EAGAIN) { |
|
/* |
|
* A page that has been migrated has all references |
|
* removed and will be freed. A page that has not been |
|
* migrated will have kept its references and be restored. |
|
*/ |
|
list_del(&page->lru); |
|
} |
|
|
|
/* |
|
* If migration is successful, releases reference grabbed during |
|
* isolation. Otherwise, restore the page to right list unless |
|
* we want to retry. |
|
*/ |
|
if (rc == MIGRATEPAGE_SUCCESS) { |
|
/* |
|
* Compaction can migrate also non-LRU pages which are |
|
* not accounted to NR_ISOLATED_*. They can be recognized |
|
* as __PageMovable |
|
*/ |
|
if (likely(!__PageMovable(page))) |
|
mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON + |
|
page_is_file_lru(page), -thp_nr_pages(page)); |
|
|
|
if (reason != MR_MEMORY_FAILURE) |
|
/* |
|
* We release the page in page_handle_poison. |
|
*/ |
|
put_page(page); |
|
} else { |
|
if (rc != -EAGAIN) |
|
list_add_tail(&page->lru, ret); |
|
|
|
if (put_new_page) |
|
put_new_page(newpage, private); |
|
else |
|
put_page(newpage); |
|
} |
|
|
|
return rc; |
|
} |
|
|
|
/* |
|
* Counterpart of unmap_and_move_page() for hugepage migration. |
|
* |
|
* This function doesn't wait the completion of hugepage I/O |
|
* because there is no race between I/O and migration for hugepage. |
|
* Note that currently hugepage I/O occurs only in direct I/O |
|
* where no lock is held and PG_writeback is irrelevant, |
|
* and writeback status of all subpages are counted in the reference |
|
* count of the head page (i.e. if all subpages of a 2MB hugepage are |
|
* under direct I/O, the reference of the head page is 512 and a bit more.) |
|
* This means that when we try to migrate hugepage whose subpages are |
|
* doing direct I/O, some references remain after try_to_unmap() and |
|
* hugepage migration fails without data corruption. |
|
* |
|
* There is also no race when direct I/O is issued on the page under migration, |
|
* because then pte is replaced with migration swap entry and direct I/O code |
|
* will wait in the page fault for migration to complete. |
|
*/ |
|
static int unmap_and_move_huge_page(new_page_t get_new_page, |
|
free_page_t put_new_page, unsigned long private, |
|
struct page *hpage, int force, |
|
enum migrate_mode mode, int reason, |
|
struct list_head *ret) |
|
{ |
|
struct folio *dst, *src = page_folio(hpage); |
|
int rc = -EAGAIN; |
|
int page_was_mapped = 0; |
|
struct page *new_hpage; |
|
struct anon_vma *anon_vma = NULL; |
|
struct address_space *mapping = NULL; |
|
|
|
/* |
|
* Migratability of hugepages depends on architectures and their size. |
|
* This check is necessary because some callers of hugepage migration |
|
* like soft offline and memory hotremove don't walk through page |
|
* tables or check whether the hugepage is pmd-based or not before |
|
* kicking migration. |
|
*/ |
|
if (!hugepage_migration_supported(page_hstate(hpage))) { |
|
list_move_tail(&hpage->lru, ret); |
|
return -ENOSYS; |
|
} |
|
|
|
if (page_count(hpage) == 1) { |
|
/* page was freed from under us. So we are done. */ |
|
putback_active_hugepage(hpage); |
|
return MIGRATEPAGE_SUCCESS; |
|
} |
|
|
|
new_hpage = get_new_page(hpage, private); |
|
if (!new_hpage) |
|
return -ENOMEM; |
|
dst = page_folio(new_hpage); |
|
|
|
if (!trylock_page(hpage)) { |
|
if (!force) |
|
goto out; |
|
switch (mode) { |
|
case MIGRATE_SYNC: |
|
case MIGRATE_SYNC_NO_COPY: |
|
break; |
|
default: |
|
goto out; |
|
} |
|
lock_page(hpage); |
|
} |
|
|
|
/* |
|
* Check for pages which are in the process of being freed. Without |
|
* page_mapping() set, hugetlbfs specific move page routine will not |
|
* be called and we could leak usage counts for subpools. |
|
*/ |
|
if (hugetlb_page_subpool(hpage) && !page_mapping(hpage)) { |
|
rc = -EBUSY; |
|
goto out_unlock; |
|
} |
|
|
|
if (PageAnon(hpage)) |
|
anon_vma = page_get_anon_vma(hpage); |
|
|
|
if (unlikely(!trylock_page(new_hpage))) |
|
goto put_anon; |
|
|
|
if (page_mapped(hpage)) { |
|
bool mapping_locked = false; |
|
enum ttu_flags ttu = 0; |
|
|
|
if (!PageAnon(hpage)) { |
|
/* |
|
* In shared mappings, try_to_unmap could potentially |
|
* call huge_pmd_unshare. Because of this, take |
|
* semaphore in write mode here and set TTU_RMAP_LOCKED |
|
* to let lower levels know we have taken the lock. |
|
*/ |
|
mapping = hugetlb_page_mapping_lock_write(hpage); |
|
if (unlikely(!mapping)) |
|
goto unlock_put_anon; |
|
|
|
mapping_locked = true; |
|
ttu |= TTU_RMAP_LOCKED; |
|
} |
|
|
|
try_to_migrate(src, ttu); |
|
page_was_mapped = 1; |
|
|
|
if (mapping_locked) |
|
i_mmap_unlock_write(mapping); |
|
} |
|
|
|
if (!page_mapped(hpage)) |
|
rc = move_to_new_page(new_hpage, hpage, mode); |
|
|
|
if (page_was_mapped) |
|
remove_migration_ptes(src, |
|
rc == MIGRATEPAGE_SUCCESS ? dst : src, false); |
|
|
|
unlock_put_anon: |
|
unlock_page(new_hpage); |
|
|
|
put_anon: |
|
if (anon_vma) |
|
put_anon_vma(anon_vma); |
|
|
|
if (rc == MIGRATEPAGE_SUCCESS) { |
|
move_hugetlb_state(hpage, new_hpage, reason); |
|
put_new_page = NULL; |
|
} |
|
|
|
out_unlock: |
|
unlock_page(hpage); |
|
out: |
|
if (rc == MIGRATEPAGE_SUCCESS) |
|
putback_active_hugepage(hpage); |
|
else if (rc != -EAGAIN) |
|
list_move_tail(&hpage->lru, ret); |
|
|
|
/* |
|
* If migration was not successful and there's a freeing callback, use |
|
* it. Otherwise, put_page() will drop the reference grabbed during |
|
* isolation. |
|
*/ |
|
if (put_new_page) |
|
put_new_page(new_hpage, private); |
|
else |
|
putback_active_hugepage(new_hpage); |
|
|
|
return rc; |
|
} |
|
|
|
static inline int try_split_thp(struct page *page, struct page **page2, |
|
struct list_head *from) |
|
{ |
|
int rc = 0; |
|
|
|
lock_page(page); |
|
rc = split_huge_page_to_list(page, from); |
|
unlock_page(page); |
|
if (!rc) |
|
list_safe_reset_next(page, *page2, lru); |
|
|
|
return rc; |
|
} |
|
|
|
/* |
|
* migrate_pages - migrate the pages specified in a list, to the free pages |
|
* supplied as the target for the page migration |
|
* |
|
* @from: The list of pages to be migrated. |
|
* @get_new_page: The function used to allocate free pages to be used |
|
* as the target of the page migration. |
|
* @put_new_page: The function used to free target pages if migration |
|
* fails, or NULL if no special handling is necessary. |
|
* @private: Private data to be passed on to get_new_page() |
|
* @mode: The migration mode that specifies the constraints for |
|
* page migration, if any. |
|
* @reason: The reason for page migration. |
|
* @ret_succeeded: Set to the number of normal pages migrated successfully if |
|
* the caller passes a non-NULL pointer. |
|
* |
|
* The function returns after 10 attempts or if no pages are movable any more |
|
* because the list has become empty or no retryable pages exist any more. |
|
* It is caller's responsibility to call putback_movable_pages() to return pages |
|
* to the LRU or free list only if ret != 0. |
|
* |
|
* Returns the number of {normal page, THP, hugetlb} that were not migrated, or |
|
* an error code. The number of THP splits will be considered as the number of |
|
* non-migrated THP, no matter how many subpages of the THP are migrated successfully. |
|
*/ |
|
int migrate_pages(struct list_head *from, new_page_t get_new_page, |
|
free_page_t put_new_page, unsigned long private, |
|
enum migrate_mode mode, int reason, unsigned int *ret_succeeded) |
|
{ |
|
int retry = 1; |
|
int thp_retry = 1; |
|
int nr_failed = 0; |
|
int nr_failed_pages = 0; |
|
int nr_succeeded = 0; |
|
int nr_thp_succeeded = 0; |
|
int nr_thp_failed = 0; |
|
int nr_thp_split = 0; |
|
int pass = 0; |
|
bool is_thp = false; |
|
struct page *page; |
|
struct page *page2; |
|
int rc, nr_subpages; |
|
LIST_HEAD(ret_pages); |
|
LIST_HEAD(thp_split_pages); |
|
bool nosplit = (reason == MR_NUMA_MISPLACED); |
|
bool no_subpage_counting = false; |
|
|
|
trace_mm_migrate_pages_start(mode, reason); |
|
|
|
thp_subpage_migration: |
|
for (pass = 0; pass < 10 && (retry || thp_retry); pass++) { |
|
retry = 0; |
|
thp_retry = 0; |
|
|
|
list_for_each_entry_safe(page, page2, from, lru) { |
|
retry: |
|
/* |
|
* THP statistics is based on the source huge page. |
|
* Capture required information that might get lost |
|
* during migration. |
|
*/ |
|
is_thp = PageTransHuge(page) && !PageHuge(page); |
|
nr_subpages = compound_nr(page); |
|
cond_resched(); |
|
|
|
if (PageHuge(page)) |
|
rc = unmap_and_move_huge_page(get_new_page, |
|
put_new_page, private, page, |
|
pass > 2, mode, reason, |
|
&ret_pages); |
|
else |
|
rc = unmap_and_move(get_new_page, put_new_page, |
|
private, page, pass > 2, mode, |
|
reason, &ret_pages); |
|
/* |
|
* The rules are: |
|
* Success: non hugetlb page will be freed, hugetlb |
|
* page will be put back |
|
* -EAGAIN: stay on the from list |
|
* -ENOMEM: stay on the from list |
|
* Other errno: put on ret_pages list then splice to |
|
* from list |
|
*/ |
|
switch(rc) { |
|
/* |
|
* THP migration might be unsupported or the |
|
* allocation could've failed so we should |
|
* retry on the same page with the THP split |
|
* to base pages. |
|
* |
|
* Head page is retried immediately and tail |
|
* pages are added to the tail of the list so |
|
* we encounter them after the rest of the list |
|
* is processed. |
|
*/ |
|
case -ENOSYS: |
|
/* THP migration is unsupported */ |
|
if (is_thp) { |
|
nr_thp_failed++; |
|
if (!try_split_thp(page, &page2, &thp_split_pages)) { |
|
nr_thp_split++; |
|
goto retry; |
|
} |
|
|
|
nr_failed_pages += nr_subpages; |
|
break; |
|
} |
|
|
|
/* Hugetlb migration is unsupported */ |
|
if (!no_subpage_counting) |
|
nr_failed++; |
|
nr_failed_pages += nr_subpages; |
|
break; |
|
case -ENOMEM: |
|
/* |
|
* When memory is low, don't bother to try to migrate |
|
* other pages, just exit. |
|
* THP NUMA faulting doesn't split THP to retry. |
|
*/ |
|
if (is_thp && !nosplit) { |
|
nr_thp_failed++; |
|
if (!try_split_thp(page, &page2, &thp_split_pages)) { |
|
nr_thp_split++; |
|
goto retry; |
|
} |
|
|
|
nr_failed_pages += nr_subpages; |
|
goto out; |
|
} |
|
|
|
if (!no_subpage_counting) |
|
nr_failed++; |
|
nr_failed_pages += nr_subpages; |
|
goto out; |
|
case -EAGAIN: |
|
if (is_thp) { |
|
thp_retry++; |
|
break; |
|
} |
|
retry++; |
|
break; |
|
case MIGRATEPAGE_SUCCESS: |
|
nr_succeeded += nr_subpages; |
|
if (is_thp) { |
|
nr_thp_succeeded++; |
|
break; |
|
} |
|
break; |
|
default: |
|
/* |
|
* Permanent failure (-EBUSY, etc.): |
|
* unlike -EAGAIN case, the failed page is |
|
* removed from migration page list and not |
|
* retried in the next outer loop. |
|
*/ |
|
if (is_thp) { |
|
nr_thp_failed++; |
|
nr_failed_pages += nr_subpages; |
|
break; |
|
} |
|
|
|
if (!no_subpage_counting) |
|
nr_failed++; |
|
nr_failed_pages += nr_subpages; |
|
break; |
|
} |
|
} |
|
} |
|
nr_failed += retry; |
|
nr_thp_failed += thp_retry; |
|
/* |
|
* Try to migrate subpages of fail-to-migrate THPs, no nr_failed |
|
* counting in this round, since all subpages of a THP is counted |
|
* as 1 failure in the first round. |
|
*/ |
|
if (!list_empty(&thp_split_pages)) { |
|
/* |
|
* Move non-migrated pages (after 10 retries) to ret_pages |
|
* to avoid migrating them again. |
|
*/ |
|
list_splice_init(from, &ret_pages); |
|
list_splice_init(&thp_split_pages, from); |
|
no_subpage_counting = true; |
|
retry = 1; |
|
goto thp_subpage_migration; |
|
} |
|
|
|
rc = nr_failed + nr_thp_failed; |
|
out: |
|
/* |
|
* Put the permanent failure page back to migration list, they |
|
* will be put back to the right list by the caller. |
|
*/ |
|
list_splice(&ret_pages, from); |
|
|
|
count_vm_events(PGMIGRATE_SUCCESS, nr_succeeded); |
|
count_vm_events(PGMIGRATE_FAIL, nr_failed_pages); |
|
count_vm_events(THP_MIGRATION_SUCCESS, nr_thp_succeeded); |
|
count_vm_events(THP_MIGRATION_FAIL, nr_thp_failed); |
|
count_vm_events(THP_MIGRATION_SPLIT, nr_thp_split); |
|
trace_mm_migrate_pages(nr_succeeded, nr_failed_pages, nr_thp_succeeded, |
|
nr_thp_failed, nr_thp_split, mode, reason); |
|
|
|
if (ret_succeeded) |
|
*ret_succeeded = nr_succeeded; |
|
|
|
return rc; |
|
} |
|
|
|
struct page *alloc_migration_target(struct page *page, unsigned long private) |
|
{ |
|
struct folio *folio = page_folio(page); |
|
struct migration_target_control *mtc; |
|
gfp_t gfp_mask; |
|
unsigned int order = 0; |
|
struct folio *new_folio = NULL; |
|
int nid; |
|
int zidx; |
|
|
|
mtc = (struct migration_target_control *)private; |
|
gfp_mask = mtc->gfp_mask; |
|
nid = mtc->nid; |
|
if (nid == NUMA_NO_NODE) |
|
nid = folio_nid(folio); |
|
|
|
if (folio_test_hugetlb(folio)) { |
|
struct hstate *h = page_hstate(&folio->page); |
|
|
|
gfp_mask = htlb_modify_alloc_mask(h, gfp_mask); |
|
return alloc_huge_page_nodemask(h, nid, mtc->nmask, gfp_mask); |
|
} |
|
|
|
if (folio_test_large(folio)) { |
|
/* |
|
* clear __GFP_RECLAIM to make the migration callback |
|
* consistent with regular THP allocations. |
|
*/ |
|
gfp_mask &= ~__GFP_RECLAIM; |
|
gfp_mask |= GFP_TRANSHUGE; |
|
order = folio_order(folio); |
|
} |
|
zidx = zone_idx(folio_zone(folio)); |
|
if (is_highmem_idx(zidx) || zidx == ZONE_MOVABLE) |
|
gfp_mask |= __GFP_HIGHMEM; |
|
|
|
new_folio = __folio_alloc(gfp_mask, order, nid, mtc->nmask); |
|
|
|
return &new_folio->page; |
|
} |
|
|
|
#ifdef CONFIG_NUMA |
|
|
|
static int store_status(int __user *status, int start, int value, int nr) |
|
{ |
|
while (nr-- > 0) { |
|
if (put_user(value, status + start)) |
|
return -EFAULT; |
|
start++; |
|
} |
|
|
|
return 0; |
|
} |
|
|
|
static int do_move_pages_to_node(struct mm_struct *mm, |
|
struct list_head *pagelist, int node) |
|
{ |
|
int err; |
|
struct migration_target_control mtc = { |
|
.nid = node, |
|
.gfp_mask = GFP_HIGHUSER_MOVABLE | __GFP_THISNODE, |
|
}; |
|
|
|
err = migrate_pages(pagelist, alloc_migration_target, NULL, |
|
(unsigned long)&mtc, MIGRATE_SYNC, MR_SYSCALL, NULL); |
|
if (err) |
|
putback_movable_pages(pagelist); |
|
return err; |
|
} |
|
|
|
/* |
|
* Resolves the given address to a struct page, isolates it from the LRU and |
|
* puts it to the given pagelist. |
|
* Returns: |
|
* errno - if the page cannot be found/isolated |
|
* 0 - when it doesn't have to be migrated because it is already on the |
|
* target node |
|
* 1 - when it has been queued |
|
*/ |
|
static int add_page_for_migration(struct mm_struct *mm, unsigned long addr, |
|
int node, struct list_head *pagelist, bool migrate_all) |
|
{ |
|
struct vm_area_struct *vma; |
|
struct page *page; |
|
int err; |
|
|
|
mmap_read_lock(mm); |
|
err = -EFAULT; |
|
vma = find_vma(mm, addr); |
|
if (!vma || addr < vma->vm_start || !vma_migratable(vma)) |
|
goto out; |
|
|
|
/* FOLL_DUMP to ignore special (like zero) pages */ |
|
page = follow_page(vma, addr, FOLL_GET | FOLL_DUMP); |
|
|
|
err = PTR_ERR(page); |
|
if (IS_ERR(page)) |
|
goto out; |
|
|
|
err = -ENOENT; |
|
if (!page) |
|
goto out; |
|
|
|
err = 0; |
|
if (page_to_nid(page) == node) |
|
goto out_putpage; |
|
|
|
err = -EACCES; |
|
if (page_mapcount(page) > 1 && !migrate_all) |
|
goto out_putpage; |
|
|
|
if (PageHuge(page)) { |
|
if (PageHead(page)) { |
|
isolate_huge_page(page, pagelist); |
|
err = 1; |
|
} |
|
} else { |
|
struct page *head; |
|
|
|
head = compound_head(page); |
|
err = isolate_lru_page(head); |
|
if (err) |
|
goto out_putpage; |
|
|
|
err = 1; |
|
list_add_tail(&head->lru, pagelist); |
|
mod_node_page_state(page_pgdat(head), |
|
NR_ISOLATED_ANON + page_is_file_lru(head), |
|
thp_nr_pages(head)); |
|
} |
|
out_putpage: |
|
/* |
|
* Either remove the duplicate refcount from |
|
* isolate_lru_page() or drop the page ref if it was |
|
* not isolated. |
|
*/ |
|
put_page(page); |
|
out: |
|
mmap_read_unlock(mm); |
|
return err; |
|
} |
|
|
|
static int move_pages_and_store_status(struct mm_struct *mm, int node, |
|
struct list_head *pagelist, int __user *status, |
|
int start, int i, unsigned long nr_pages) |
|
{ |
|
int err; |
|
|
|
if (list_empty(pagelist)) |
|
return 0; |
|
|
|
err = do_move_pages_to_node(mm, pagelist, node); |
|
if (err) { |
|
/* |
|
* Positive err means the number of failed |
|
* pages to migrate. Since we are going to |
|
* abort and return the number of non-migrated |
|
* pages, so need to include the rest of the |
|
* nr_pages that have not been attempted as |
|
* well. |
|
*/ |
|
if (err > 0) |
|
err += nr_pages - i - 1; |
|
return err; |
|
} |
|
return store_status(status, start, node, i - start); |
|
} |
|
|
|
/* |
|
* Migrate an array of page address onto an array of nodes and fill |
|
* the corresponding array of status. |
|
*/ |
|
static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes, |
|
unsigned long nr_pages, |
|
const void __user * __user *pages, |
|
const int __user *nodes, |
|
int __user *status, int flags) |
|
{ |
|
int current_node = NUMA_NO_NODE; |
|
LIST_HEAD(pagelist); |
|
int start, i; |
|
int err = 0, err1; |
|
|
|
lru_cache_disable(); |
|
|
|
for (i = start = 0; i < nr_pages; i++) { |
|
const void __user *p; |
|
unsigned long addr; |
|
int node; |
|
|
|
err = -EFAULT; |
|
if (get_user(p, pages + i)) |
|
goto out_flush; |
|
if (get_user(node, nodes + i)) |
|
goto out_flush; |
|
addr = (unsigned long)untagged_addr(p); |
|
|
|
err = -ENODEV; |
|
if (node < 0 || node >= MAX_NUMNODES) |
|
goto out_flush; |
|
if (!node_state(node, N_MEMORY)) |
|
goto out_flush; |
|
|
|
err = -EACCES; |
|
if (!node_isset(node, task_nodes)) |
|
goto out_flush; |
|
|
|
if (current_node == NUMA_NO_NODE) { |
|
current_node = node; |
|
start = i; |
|
} else if (node != current_node) { |
|
err = move_pages_and_store_status(mm, current_node, |
|
&pagelist, status, start, i, nr_pages); |
|
if (err) |
|
goto out; |
|
start = i; |
|
current_node = node; |
|
} |
|
|
|
/* |
|
* Errors in the page lookup or isolation are not fatal and we simply |
|
* report them via status |
|
*/ |
|
err = add_page_for_migration(mm, addr, current_node, |
|
&pagelist, flags & MPOL_MF_MOVE_ALL); |
|
|
|
if (err > 0) { |
|
/* The page is successfully queued for migration */ |
|
continue; |
|
} |
|
|
|
/* |
|
* The move_pages() man page does not have an -EEXIST choice, so |
|
* use -EFAULT instead. |
|
*/ |
|
if (err == -EEXIST) |
|
err = -EFAULT; |
|
|
|
/* |
|
* If the page is already on the target node (!err), store the |
|
* node, otherwise, store the err. |
|
*/ |
|
err = store_status(status, i, err ? : current_node, 1); |
|
if (err) |
|
goto out_flush; |
|
|
|
err = move_pages_and_store_status(mm, current_node, &pagelist, |
|
status, start, i, nr_pages); |
|
if (err) |
|
goto out; |
|
current_node = NUMA_NO_NODE; |
|
} |
|
out_flush: |
|
/* Make sure we do not overwrite the existing error */ |
|
err1 = move_pages_and_store_status(mm, current_node, &pagelist, |
|
status, start, i, nr_pages); |
|
if (err >= 0) |
|
err = err1; |
|
out: |
|
lru_cache_enable(); |
|
return err; |
|
} |
|
|
|
/* |
|
* Determine the nodes of an array of pages and store it in an array of status. |
|
*/ |
|
static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages, |
|
const void __user **pages, int *status) |
|
{ |
|
unsigned long i; |
|
|
|
mmap_read_lock(mm); |
|
|
|
for (i = 0; i < nr_pages; i++) { |
|
unsigned long addr = (unsigned long)(*pages); |
|
struct vm_area_struct *vma; |
|
struct page *page; |
|
int err = -EFAULT; |
|
|
|
vma = vma_lookup(mm, addr); |
|
if (!vma) |
|
goto set_status; |
|
|
|
/* FOLL_DUMP to ignore special (like zero) pages */ |
|
page = follow_page(vma, addr, FOLL_DUMP); |
|
|
|
err = PTR_ERR(page); |
|
if (IS_ERR(page)) |
|
goto set_status; |
|
|
|
err = page ? page_to_nid(page) : -ENOENT; |
|
set_status: |
|
*status = err; |
|
|
|
pages++; |
|
status++; |
|
} |
|
|
|
mmap_read_unlock(mm); |
|
} |
|
|
|
static int get_compat_pages_array(const void __user *chunk_pages[], |
|
const void __user * __user *pages, |
|
unsigned long chunk_nr) |
|
{ |
|
compat_uptr_t __user *pages32 = (compat_uptr_t __user *)pages; |
|
compat_uptr_t p; |
|
int i; |
|
|
|
for (i = 0; i < chunk_nr; i++) { |
|
if (get_user(p, pages32 + i)) |
|
return -EFAULT; |
|
chunk_pages[i] = compat_ptr(p); |
|
} |
|
|
|
return 0; |
|
} |
|
|
|
/* |
|
* Determine the nodes of a user array of pages and store it in |
|
* a user array of status. |
|
*/ |
|
static int do_pages_stat(struct mm_struct *mm, unsigned long nr_pages, |
|
const void __user * __user *pages, |
|
int __user *status) |
|
{ |
|
#define DO_PAGES_STAT_CHUNK_NR 16 |
|
const void __user *chunk_pages[DO_PAGES_STAT_CHUNK_NR]; |
|
int chunk_status[DO_PAGES_STAT_CHUNK_NR]; |
|
|
|
while (nr_pages) { |
|
unsigned long chunk_nr; |
|
|
|
chunk_nr = nr_pages; |
|
if (chunk_nr > DO_PAGES_STAT_CHUNK_NR) |
|
chunk_nr = DO_PAGES_STAT_CHUNK_NR; |
|
|
|
if (in_compat_syscall()) { |
|
if (get_compat_pages_array(chunk_pages, pages, |
|
chunk_nr)) |
|
break; |
|
} else { |
|
if (copy_from_user(chunk_pages, pages, |
|
chunk_nr * sizeof(*chunk_pages))) |
|
break; |
|
} |
|
|
|
do_pages_stat_array(mm, chunk_nr, chunk_pages, chunk_status); |
|
|
|
if (copy_to_user(status, chunk_status, chunk_nr * sizeof(*status))) |
|
break; |
|
|
|
pages += chunk_nr; |
|
status += chunk_nr; |
|
nr_pages -= chunk_nr; |
|
} |
|
return nr_pages ? -EFAULT : 0; |
|
} |
|
|
|
static struct mm_struct *find_mm_struct(pid_t pid, nodemask_t *mem_nodes) |
|
{ |
|
struct task_struct *task; |
|
struct mm_struct *mm; |
|
|
|
/* |
|
* There is no need to check if current process has the right to modify |
|
* the specified process when they are same. |
|
*/ |
|
if (!pid) { |
|
mmget(current->mm); |
|
*mem_nodes = cpuset_mems_allowed(current); |
|
return current->mm; |
|
} |
|
|
|
/* Find the mm_struct */ |
|
rcu_read_lock(); |
|
task = find_task_by_vpid(pid); |
|
if (!task) { |
|
rcu_read_unlock(); |
|
return ERR_PTR(-ESRCH); |
|
} |
|
get_task_struct(task); |
|
|
|
/* |
|
* Check if this process has the right to modify the specified |
|
* process. Use the regular "ptrace_may_access()" checks. |
|
*/ |
|
if (!ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS)) { |
|
rcu_read_unlock(); |
|
mm = ERR_PTR(-EPERM); |
|
goto out; |
|
} |
|
rcu_read_unlock(); |
|
|
|
mm = ERR_PTR(security_task_movememory(task)); |
|
if (IS_ERR(mm)) |
|
goto out; |
|
*mem_nodes = cpuset_mems_allowed(task); |
|
mm = get_task_mm(task); |
|
out: |
|
put_task_struct(task); |
|
if (!mm) |
|
mm = ERR_PTR(-EINVAL); |
|
return mm; |
|
} |
|
|
|
/* |
|
* Move a list of pages in the address space of the currently executing |
|
* process. |
|
*/ |
|
static int kernel_move_pages(pid_t pid, unsigned long nr_pages, |
|
const void __user * __user *pages, |
|
const int __user *nodes, |
|
int __user *status, int flags) |
|
{ |
|
struct mm_struct *mm; |
|
int err; |
|
nodemask_t task_nodes; |
|
|
|
/* Check flags */ |
|
if (flags & ~(MPOL_MF_MOVE|MPOL_MF_MOVE_ALL)) |
|
return -EINVAL; |
|
|
|
if ((flags & MPOL_MF_MOVE_ALL) && !capable(CAP_SYS_NICE)) |
|
return -EPERM; |
|
|
|
mm = find_mm_struct(pid, &task_nodes); |
|
if (IS_ERR(mm)) |
|
return PTR_ERR(mm); |
|
|
|
if (nodes) |
|
err = do_pages_move(mm, task_nodes, nr_pages, pages, |
|
nodes, status, flags); |
|
else |
|
err = do_pages_stat(mm, nr_pages, pages, status); |
|
|
|
mmput(mm); |
|
return err; |
|
} |
|
|
|
SYSCALL_DEFINE6(move_pages, pid_t, pid, unsigned long, nr_pages, |
|
const void __user * __user *, pages, |
|
const int __user *, nodes, |
|
int __user *, status, int, flags) |
|
{ |
|
return kernel_move_pages(pid, nr_pages, pages, nodes, status, flags); |
|
} |
|
|
|
#ifdef CONFIG_NUMA_BALANCING |
|
/* |
|
* Returns true if this is a safe migration target node for misplaced NUMA |
|
* pages. Currently it only checks the watermarks which crude |
|
*/ |
|
static bool migrate_balanced_pgdat(struct pglist_data *pgdat, |
|
unsigned long nr_migrate_pages) |
|
{ |
|
int z; |
|
|
|
for (z = pgdat->nr_zones - 1; z >= 0; z--) { |
|
struct zone *zone = pgdat->node_zones + z; |
|
|
|
if (!populated_zone(zone)) |
|
continue; |
|
|
|
/* Avoid waking kswapd by allocating pages_to_migrate pages. */ |
|
if (!zone_watermark_ok(zone, 0, |
|
high_wmark_pages(zone) + |
|
nr_migrate_pages, |
|
ZONE_MOVABLE, 0)) |
|
continue; |
|
return true; |
|
} |
|
return false; |
|
} |
|
|
|
static struct page *alloc_misplaced_dst_page(struct page *page, |
|
unsigned long data) |
|
{ |
|
int nid = (int) data; |
|
int order = compound_order(page); |
|
gfp_t gfp = __GFP_THISNODE; |
|
struct folio *new; |
|
|
|
if (order > 0) |
|
gfp |= GFP_TRANSHUGE_LIGHT; |
|
else { |
|
gfp |= GFP_HIGHUSER_MOVABLE | __GFP_NOMEMALLOC | __GFP_NORETRY | |
|
__GFP_NOWARN; |
|
gfp &= ~__GFP_RECLAIM; |
|
} |
|
new = __folio_alloc_node(gfp, order, nid); |
|
|
|
return &new->page; |
|
} |
|
|
|
static int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page) |
|
{ |
|
int page_lru; |
|
int nr_pages = thp_nr_pages(page); |
|
int order = compound_order(page); |
|
|
|
VM_BUG_ON_PAGE(order && !PageTransHuge(page), page); |
|
|
|
/* Do not migrate THP mapped by multiple processes */ |
|
if (PageTransHuge(page) && total_mapcount(page) > 1) |
|
return 0; |
|
|
|
/* Avoid migrating to a node that is nearly full */ |
|
if (!migrate_balanced_pgdat(pgdat, nr_pages)) { |
|
int z; |
|
|
|
if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING)) |
|
return 0; |
|
for (z = pgdat->nr_zones - 1; z >= 0; z--) { |
|
if (populated_zone(pgdat->node_zones + z)) |
|
break; |
|
} |
|
wakeup_kswapd(pgdat->node_zones + z, 0, order, ZONE_MOVABLE); |
|
return 0; |
|
} |
|
|
|
if (isolate_lru_page(page)) |
|
return 0; |
|
|
|
page_lru = page_is_file_lru(page); |
|
mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON + page_lru, |
|
nr_pages); |
|
|
|
/* |
|
* Isolating the page has taken another reference, so the |
|
* caller's reference can be safely dropped without the page |
|
* disappearing underneath us during migration. |
|
*/ |
|
put_page(page); |
|
return 1; |
|
} |
|
|
|
/* |
|
* Attempt to migrate a misplaced page to the specified destination |
|
* node. Caller is expected to have an elevated reference count on |
|
* the page that will be dropped by this function before returning. |
|
*/ |
|
int migrate_misplaced_page(struct page *page, struct vm_area_struct *vma, |
|
int node) |
|
{ |
|
pg_data_t *pgdat = NODE_DATA(node); |
|
int isolated; |
|
int nr_remaining; |
|
unsigned int nr_succeeded; |
|
LIST_HEAD(migratepages); |
|
int nr_pages = thp_nr_pages(page); |
|
|
|
/* |
|
* Don't migrate file pages that are mapped in multiple processes |
|
* with execute permissions as they are probably shared libraries. |
|
*/ |
|
if (page_mapcount(page) != 1 && page_is_file_lru(page) && |
|
(vma->vm_flags & VM_EXEC)) |
|
goto out; |
|
|
|
/* |
|
* Also do not migrate dirty pages as not all filesystems can move |
|
* dirty pages in MIGRATE_ASYNC mode which is a waste of cycles. |
|
*/ |
|
if (page_is_file_lru(page) && PageDirty(page)) |
|
goto out; |
|
|
|
isolated = numamigrate_isolate_page(pgdat, page); |
|
if (!isolated) |
|
goto out; |
|
|
|
list_add(&page->lru, &migratepages); |
|
nr_remaining = migrate_pages(&migratepages, alloc_misplaced_dst_page, |
|
NULL, node, MIGRATE_ASYNC, |
|
MR_NUMA_MISPLACED, &nr_succeeded); |
|
if (nr_remaining) { |
|
if (!list_empty(&migratepages)) { |
|
list_del(&page->lru); |
|
mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON + |
|
page_is_file_lru(page), -nr_pages); |
|
putback_lru_page(page); |
|
} |
|
isolated = 0; |
|
} |
|
if (nr_succeeded) { |
|
count_vm_numa_events(NUMA_PAGE_MIGRATE, nr_succeeded); |
|
if (!node_is_toptier(page_to_nid(page)) && node_is_toptier(node)) |
|
mod_node_page_state(pgdat, PGPROMOTE_SUCCESS, |
|
nr_succeeded); |
|
} |
|
BUG_ON(!list_empty(&migratepages)); |
|
return isolated; |
|
|
|
out: |
|
put_page(page); |
|
return 0; |
|
} |
|
#endif /* CONFIG_NUMA_BALANCING */ |
|
#endif /* CONFIG_NUMA */ |
|
|
|
/* |
|
* node_demotion[] example: |
|
* |
|
* Consider a system with two sockets. Each socket has |
|
* three classes of memory attached: fast, medium and slow. |
|
* Each memory class is placed in its own NUMA node. The |
|
* CPUs are placed in the node with the "fast" memory. The |
|
* 6 NUMA nodes (0-5) might be split among the sockets like |
|
* this: |
|
* |
|
* Socket A: 0, 1, 2 |
|
* Socket B: 3, 4, 5 |
|
* |
|
* When Node 0 fills up, its memory should be migrated to |
|
* Node 1. When Node 1 fills up, it should be migrated to |
|
* Node 2. The migration path start on the nodes with the |
|
* processors (since allocations default to this node) and |
|
* fast memory, progress through medium and end with the |
|
* slow memory: |
|
* |
|
* 0 -> 1 -> 2 -> stop |
|
* 3 -> 4 -> 5 -> stop |
|
* |
|
* This is represented in the node_demotion[] like this: |
|
* |
|
* { nr=1, nodes[0]=1 }, // Node 0 migrates to 1 |
|
* { nr=1, nodes[0]=2 }, // Node 1 migrates to 2 |
|
* { nr=0, nodes[0]=-1 }, // Node 2 does not migrate |
|
* { nr=1, nodes[0]=4 }, // Node 3 migrates to 4 |
|
* { nr=1, nodes[0]=5 }, // Node 4 migrates to 5 |
|
* { nr=0, nodes[0]=-1 }, // Node 5 does not migrate |
|
* |
|
* Moreover some systems may have multiple slow memory nodes. |
|
* Suppose a system has one socket with 3 memory nodes, node 0 |
|
* is fast memory type, and node 1/2 both are slow memory |
|
* type, and the distance between fast memory node and slow |
|
* memory node is same. So the migration path should be: |
|
* |
|
* 0 -> 1/2 -> stop |
|
* |
|
* This is represented in the node_demotion[] like this: |
|
* { nr=2, {nodes[0]=1, nodes[1]=2} }, // Node 0 migrates to node 1 and node 2 |
|
* { nr=0, nodes[0]=-1, }, // Node 1 dose not migrate |
|
* { nr=0, nodes[0]=-1, }, // Node 2 does not migrate |
|
*/ |
|
|
|
/* |
|
* Writes to this array occur without locking. Cycles are |
|
* not allowed: Node X demotes to Y which demotes to X... |
|
* |
|
* If multiple reads are performed, a single rcu_read_lock() |
|
* must be held over all reads to ensure that no cycles are |
|
* observed. |
|
*/ |
|
#define DEFAULT_DEMOTION_TARGET_NODES 15 |
|
|
|
#if MAX_NUMNODES < DEFAULT_DEMOTION_TARGET_NODES |
|
#define DEMOTION_TARGET_NODES (MAX_NUMNODES - 1) |
|
#else |
|
#define DEMOTION_TARGET_NODES DEFAULT_DEMOTION_TARGET_NODES |
|
#endif |
|
|
|
struct demotion_nodes { |
|
unsigned short nr; |
|
short nodes[DEMOTION_TARGET_NODES]; |
|
}; |
|
|
|
static struct demotion_nodes *node_demotion __read_mostly; |
|
|
|
/** |
|
* next_demotion_node() - Get the next node in the demotion path |
|
* @node: The starting node to lookup the next node |
|
* |
|
* Return: node id for next memory node in the demotion path hierarchy |
|
* from @node; NUMA_NO_NODE if @node is terminal. This does not keep |
|
* @node online or guarantee that it *continues* to be the next demotion |
|
* target. |
|
*/ |
|
int next_demotion_node(int node) |
|
{ |
|
struct demotion_nodes *nd; |
|
unsigned short target_nr, index; |
|
int target; |
|
|
|
if (!node_demotion) |
|
return NUMA_NO_NODE; |
|
|
|
nd = &node_demotion[node]; |
|
|
|
/* |
|
* node_demotion[] is updated without excluding this |
|
* function from running. RCU doesn't provide any |
|
* compiler barriers, so the READ_ONCE() is required |
|
* to avoid compiler reordering or read merging. |
|
* |
|
* Make sure to use RCU over entire code blocks if |
|
* node_demotion[] reads need to be consistent. |
|
*/ |
|
rcu_read_lock(); |
|
target_nr = READ_ONCE(nd->nr); |
|
|
|
switch (target_nr) { |
|
case 0: |
|
target = NUMA_NO_NODE; |
|
goto out; |
|
case 1: |
|
index = 0; |
|
break; |
|
default: |
|
/* |
|
* If there are multiple target nodes, just select one |
|
* target node randomly. |
|
* |
|
* In addition, we can also use round-robin to select |
|
* target node, but we should introduce another variable |
|
* for node_demotion[] to record last selected target node, |
|
* that may cause cache ping-pong due to the changing of |
|
* last target node. Or introducing per-cpu data to avoid |
|
* caching issue, which seems more complicated. So selecting |
|
* target node randomly seems better until now. |
|
*/ |
|
index = get_random_int() % target_nr; |
|
break; |
|
} |
|
|
|
target = READ_ONCE(nd->nodes[index]); |
|
|
|
out: |
|
rcu_read_unlock(); |
|
return target; |
|
} |
|
|
|
#if defined(CONFIG_HOTPLUG_CPU) |
|
/* Disable reclaim-based migration. */ |
|
static void __disable_all_migrate_targets(void) |
|
{ |
|
int node, i; |
|
|
|
if (!node_demotion) |
|
return; |
|
|
|
for_each_online_node(node) { |
|
node_demotion[node].nr = 0; |
|
for (i = 0; i < DEMOTION_TARGET_NODES; i++) |
|
node_demotion[node].nodes[i] = NUMA_NO_NODE; |
|
} |
|
} |
|
|
|
static void disable_all_migrate_targets(void) |
|
{ |
|
__disable_all_migrate_targets(); |
|
|
|
/* |
|
* Ensure that the "disable" is visible across the system. |
|
* Readers will see either a combination of before+disable |
|
* state or disable+after. They will never see before and |
|
* after state together. |
|
* |
|
* The before+after state together might have cycles and |
|
* could cause readers to do things like loop until this |
|
* function finishes. This ensures they can only see a |
|
* single "bad" read and would, for instance, only loop |
|
* once. |
|
*/ |
|
synchronize_rcu(); |
|
} |
|
|
|
/* |
|
* Find an automatic demotion target for 'node'. |
|
* Failing here is OK. It might just indicate |
|
* being at the end of a chain. |
|
*/ |
|
static int establish_migrate_target(int node, nodemask_t *used, |
|
int best_distance) |
|
{ |
|
int migration_target, index, val; |
|
struct demotion_nodes *nd; |
|
|
|
if (!node_demotion) |
|
return NUMA_NO_NODE; |
|
|
|
nd = &node_demotion[node]; |
|
|
|
migration_target = find_next_best_node(node, used); |
|
if (migration_target == NUMA_NO_NODE) |
|
return NUMA_NO_NODE; |
|
|
|
/* |
|
* If the node has been set a migration target node before, |
|
* which means it's the best distance between them. Still |
|
* check if this node can be demoted to other target nodes |
|
* if they have a same best distance. |
|
*/ |
|
if (best_distance != -1) { |
|
val = node_distance(node, migration_target); |
|
if (val > best_distance) |
|
goto out_clear; |
|
} |
|
|
|
index = nd->nr; |
|
if (WARN_ONCE(index >= DEMOTION_TARGET_NODES, |
|
"Exceeds maximum demotion target nodes\n")) |
|
goto out_clear; |
|
|
|
nd->nodes[index] = migration_target; |
|
nd->nr++; |
|
|
|
return migration_target; |
|
out_clear: |
|
node_clear(migration_target, *used); |
|
return NUMA_NO_NODE; |
|
} |
|
|
|
/* |
|
* When memory fills up on a node, memory contents can be |
|
* automatically migrated to another node instead of |
|
* discarded at reclaim. |
|
* |
|
* Establish a "migration path" which will start at nodes |
|
* with CPUs and will follow the priorities used to build the |
|
* page allocator zonelists. |
|
* |
|
* The difference here is that cycles must be avoided. If |
|
* node0 migrates to node1, then neither node1, nor anything |
|
* node1 migrates to can migrate to node0. Also one node can |
|
* be migrated to multiple nodes if the target nodes all have |
|
* a same best-distance against the source node. |
|
* |
|
* This function can run simultaneously with readers of |
|
* node_demotion[]. However, it can not run simultaneously |
|
* with itself. Exclusion is provided by memory hotplug events |
|
* being single-threaded. |
|
*/ |
|
static void __set_migration_target_nodes(void) |
|
{ |
|
nodemask_t next_pass = NODE_MASK_NONE; |
|
nodemask_t this_pass = NODE_MASK_NONE; |
|
nodemask_t used_targets = NODE_MASK_NONE; |
|
int node, best_distance; |
|
|
|
/* |
|
* Avoid any oddities like cycles that could occur |
|
* from changes in the topology. This will leave |
|
* a momentary gap when migration is disabled. |
|
*/ |
|
disable_all_migrate_targets(); |
|
|
|
/* |
|
* Allocations go close to CPUs, first. Assume that |
|
* the migration path starts at the nodes with CPUs. |
|
*/ |
|
next_pass = node_states[N_CPU]; |
|
again: |
|
this_pass = next_pass; |
|
next_pass = NODE_MASK_NONE; |
|
/* |
|
* To avoid cycles in the migration "graph", ensure |
|
* that migration sources are not future targets by |
|
* setting them in 'used_targets'. Do this only |
|
* once per pass so that multiple source nodes can |
|
* share a target node. |
|
* |
|
* 'used_targets' will become unavailable in future |
|
* passes. This limits some opportunities for |
|
* multiple source nodes to share a destination. |
|
*/ |
|
nodes_or(used_targets, used_targets, this_pass); |
|
|
|
for_each_node_mask(node, this_pass) { |
|
best_distance = -1; |
|
|
|
/* |
|
* Try to set up the migration path for the node, and the target |
|
* migration nodes can be multiple, so doing a loop to find all |
|
* the target nodes if they all have a best node distance. |
|
*/ |
|
do { |
|
int target_node = |
|
establish_migrate_target(node, &used_targets, |
|
best_distance); |
|
|
|
if (target_node == NUMA_NO_NODE) |
|
break; |
|
|
|
if (best_distance == -1) |
|
best_distance = node_distance(node, target_node); |
|
|
|
/* |
|
* Visit targets from this pass in the next pass. |
|
* Eventually, every node will have been part of |
|
* a pass, and will become set in 'used_targets'. |
|
*/ |
|
node_set(target_node, next_pass); |
|
} while (1); |
|
} |
|
/* |
|
* 'next_pass' contains nodes which became migration |
|
* targets in this pass. Make additional passes until |
|
* no more migrations targets are available. |
|
*/ |
|
if (!nodes_empty(next_pass)) |
|
goto again; |
|
} |
|
|
|
/* |
|
* For callers that do not hold get_online_mems() already. |
|
*/ |
|
void set_migration_target_nodes(void) |
|
{ |
|
get_online_mems(); |
|
__set_migration_target_nodes(); |
|
put_online_mems(); |
|
} |
|
|
|
/* |
|
* This leaves migrate-on-reclaim transiently disabled between |
|
* the MEM_GOING_OFFLINE and MEM_OFFLINE events. This runs |
|
* whether reclaim-based migration is enabled or not, which |
|
* ensures that the user can turn reclaim-based migration at |
|
* any time without needing to recalculate migration targets. |
|
* |
|
* These callbacks already hold get_online_mems(). That is why |
|
* __set_migration_target_nodes() can be used as opposed to |
|
* set_migration_target_nodes(). |
|
*/ |
|
static int __meminit migrate_on_reclaim_callback(struct notifier_block *self, |
|
unsigned long action, void *_arg) |
|
{ |
|
struct memory_notify *arg = _arg; |
|
|
|
/* |
|
* Only update the node migration order when a node is |
|
* changing status, like online->offline. This avoids |
|
* the overhead of synchronize_rcu() in most cases. |
|
*/ |
|
if (arg->status_change_nid < 0) |
|
return notifier_from_errno(0); |
|
|
|
switch (action) { |
|
case MEM_GOING_OFFLINE: |
|
/* |
|
* Make sure there are not transient states where |
|
* an offline node is a migration target. This |
|
* will leave migration disabled until the offline |
|
* completes and the MEM_OFFLINE case below runs. |
|
*/ |
|
disable_all_migrate_targets(); |
|
break; |
|
case MEM_OFFLINE: |
|
case MEM_ONLINE: |
|
/* |
|
* Recalculate the target nodes once the node |
|
* reaches its final state (online or offline). |
|
*/ |
|
__set_migration_target_nodes(); |
|
break; |
|
case MEM_CANCEL_OFFLINE: |
|
/* |
|
* MEM_GOING_OFFLINE disabled all the migration |
|
* targets. Reenable them. |
|
*/ |
|
__set_migration_target_nodes(); |
|
break; |
|
case MEM_GOING_ONLINE: |
|
case MEM_CANCEL_ONLINE: |
|
break; |
|
} |
|
|
|
return notifier_from_errno(0); |
|
} |
|
|
|
void __init migrate_on_reclaim_init(void) |
|
{ |
|
node_demotion = kmalloc_array(nr_node_ids, |
|
sizeof(struct demotion_nodes), |
|
GFP_KERNEL); |
|
WARN_ON(!node_demotion); |
|
|
|
hotplug_memory_notifier(migrate_on_reclaim_callback, 100); |
|
/* |
|
* At this point, all numa nodes with memory/CPus have their state |
|
* properly set, so we can build the demotion order now. |
|
* Let us hold the cpu_hotplug lock just, as we could possibily have |
|
* CPU hotplug events during boot. |
|
*/ |
|
cpus_read_lock(); |
|
set_migration_target_nodes(); |
|
cpus_read_unlock(); |
|
} |
|
#endif /* CONFIG_HOTPLUG_CPU */ |
|
|
|
bool numa_demotion_enabled = false; |
|
|
|
#ifdef CONFIG_SYSFS |
|
static ssize_t numa_demotion_enabled_show(struct kobject *kobj, |
|
struct kobj_attribute *attr, char *buf) |
|
{ |
|
return sysfs_emit(buf, "%s\n", |
|
numa_demotion_enabled ? "true" : "false"); |
|
} |
|
|
|
static ssize_t numa_demotion_enabled_store(struct kobject *kobj, |
|
struct kobj_attribute *attr, |
|
const char *buf, size_t count) |
|
{ |
|
if (!strncmp(buf, "true", 4) || !strncmp(buf, "1", 1)) |
|
numa_demotion_enabled = true; |
|
else if (!strncmp(buf, "false", 5) || !strncmp(buf, "0", 1)) |
|
numa_demotion_enabled = false; |
|
else |
|
return -EINVAL; |
|
|
|
return count; |
|
} |
|
|
|
static struct kobj_attribute numa_demotion_enabled_attr = |
|
__ATTR(demotion_enabled, 0644, numa_demotion_enabled_show, |
|
numa_demotion_enabled_store); |
|
|
|
static struct attribute *numa_attrs[] = { |
|
&numa_demotion_enabled_attr.attr, |
|
NULL, |
|
}; |
|
|
|
static const struct attribute_group numa_attr_group = { |
|
.attrs = numa_attrs, |
|
}; |
|
|
|
static int __init numa_init_sysfs(void) |
|
{ |
|
int err; |
|
struct kobject *numa_kobj; |
|
|
|
numa_kobj = kobject_create_and_add("numa", mm_kobj); |
|
if (!numa_kobj) { |
|
pr_err("failed to create numa kobject\n"); |
|
return -ENOMEM; |
|
} |
|
err = sysfs_create_group(numa_kobj, &numa_attr_group); |
|
if (err) { |
|
pr_err("failed to register numa group\n"); |
|
goto delete_obj; |
|
} |
|
return 0; |
|
|
|
delete_obj: |
|
kobject_put(numa_kobj); |
|
return err; |
|
} |
|
subsys_initcall(numa_init_sysfs); |
|
#endif
|
|
|