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1346 lines
39 KiB
1346 lines
39 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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/* |
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* fs/direct-io.c |
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* |
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* Copyright (C) 2002, Linus Torvalds. |
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* |
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* O_DIRECT |
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* |
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* 04Jul2002 Andrew Morton |
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* Initial version |
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* 11Sep2002 [email protected] |
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* added readv/writev support. |
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* 29Oct2002 Andrew Morton |
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* rewrote bio_add_page() support. |
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* 30Oct2002 [email protected] |
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* added support for non-aligned IO. |
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* 06Nov2002 [email protected] |
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* added asynchronous IO support. |
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* 21Jul2003 [email protected] |
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* added IO completion notifier. |
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*/ |
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|
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#include <linux/kernel.h> |
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#include <linux/module.h> |
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#include <linux/types.h> |
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#include <linux/fs.h> |
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#include <linux/mm.h> |
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#include <linux/slab.h> |
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#include <linux/highmem.h> |
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#include <linux/pagemap.h> |
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#include <linux/task_io_accounting_ops.h> |
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#include <linux/bio.h> |
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#include <linux/wait.h> |
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#include <linux/err.h> |
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#include <linux/blkdev.h> |
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#include <linux/buffer_head.h> |
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#include <linux/rwsem.h> |
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#include <linux/uio.h> |
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#include <linux/atomic.h> |
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#include <linux/prefetch.h> |
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|
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#include "internal.h" |
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|
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/* |
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* How many user pages to map in one call to get_user_pages(). This determines |
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* the size of a structure in the slab cache |
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*/ |
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#define DIO_PAGES 64 |
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|
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/* |
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* Flags for dio_complete() |
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*/ |
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#define DIO_COMPLETE_ASYNC 0x01 /* This is async IO */ |
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#define DIO_COMPLETE_INVALIDATE 0x02 /* Can invalidate pages */ |
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|
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/* |
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* This code generally works in units of "dio_blocks". A dio_block is |
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* somewhere between the hard sector size and the filesystem block size. it |
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* is determined on a per-invocation basis. When talking to the filesystem |
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* we need to convert dio_blocks to fs_blocks by scaling the dio_block quantity |
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* down by dio->blkfactor. Similarly, fs-blocksize quantities are converted |
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* to bio_block quantities by shifting left by blkfactor. |
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* |
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* If blkfactor is zero then the user's request was aligned to the filesystem's |
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* blocksize. |
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*/ |
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|
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/* dio_state only used in the submission path */ |
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|
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struct dio_submit { |
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struct bio *bio; /* bio under assembly */ |
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unsigned blkbits; /* doesn't change */ |
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unsigned blkfactor; /* When we're using an alignment which |
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is finer than the filesystem's soft |
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blocksize, this specifies how much |
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finer. blkfactor=2 means 1/4-block |
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alignment. Does not change */ |
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unsigned start_zero_done; /* flag: sub-blocksize zeroing has |
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been performed at the start of a |
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write */ |
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int pages_in_io; /* approximate total IO pages */ |
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sector_t block_in_file; /* Current offset into the underlying |
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file in dio_block units. */ |
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unsigned blocks_available; /* At block_in_file. changes */ |
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int reap_counter; /* rate limit reaping */ |
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sector_t final_block_in_request;/* doesn't change */ |
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int boundary; /* prev block is at a boundary */ |
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get_block_t *get_block; /* block mapping function */ |
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dio_submit_t *submit_io; /* IO submition function */ |
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|
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loff_t logical_offset_in_bio; /* current first logical block in bio */ |
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sector_t final_block_in_bio; /* current final block in bio + 1 */ |
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sector_t next_block_for_io; /* next block to be put under IO, |
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in dio_blocks units */ |
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|
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/* |
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* Deferred addition of a page to the dio. These variables are |
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* private to dio_send_cur_page(), submit_page_section() and |
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* dio_bio_add_page(). |
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*/ |
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struct page *cur_page; /* The page */ |
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unsigned cur_page_offset; /* Offset into it, in bytes */ |
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unsigned cur_page_len; /* Nr of bytes at cur_page_offset */ |
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sector_t cur_page_block; /* Where it starts */ |
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loff_t cur_page_fs_offset; /* Offset in file */ |
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|
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struct iov_iter *iter; |
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/* |
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* Page queue. These variables belong to dio_refill_pages() and |
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* dio_get_page(). |
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*/ |
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unsigned head; /* next page to process */ |
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unsigned tail; /* last valid page + 1 */ |
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size_t from, to; |
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}; |
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|
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/* dio_state communicated between submission path and end_io */ |
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struct dio { |
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int flags; /* doesn't change */ |
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blk_opf_t opf; /* request operation type and flags */ |
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struct gendisk *bio_disk; |
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struct inode *inode; |
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loff_t i_size; /* i_size when submitted */ |
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dio_iodone_t *end_io; /* IO completion function */ |
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|
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void *private; /* copy from map_bh.b_private */ |
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|
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/* BIO completion state */ |
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spinlock_t bio_lock; /* protects BIO fields below */ |
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int page_errors; /* errno from get_user_pages() */ |
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int is_async; /* is IO async ? */ |
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bool defer_completion; /* defer AIO completion to workqueue? */ |
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bool should_dirty; /* if pages should be dirtied */ |
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int io_error; /* IO error in completion path */ |
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unsigned long refcount; /* direct_io_worker() and bios */ |
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struct bio *bio_list; /* singly linked via bi_private */ |
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struct task_struct *waiter; /* waiting task (NULL if none) */ |
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|
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/* AIO related stuff */ |
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struct kiocb *iocb; /* kiocb */ |
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ssize_t result; /* IO result */ |
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|
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/* |
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* pages[] (and any fields placed after it) are not zeroed out at |
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* allocation time. Don't add new fields after pages[] unless you |
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* wish that they not be zeroed. |
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*/ |
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union { |
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struct page *pages[DIO_PAGES]; /* page buffer */ |
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struct work_struct complete_work;/* deferred AIO completion */ |
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}; |
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} ____cacheline_aligned_in_smp; |
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|
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static struct kmem_cache *dio_cache __read_mostly; |
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|
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/* |
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* How many pages are in the queue? |
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*/ |
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static inline unsigned dio_pages_present(struct dio_submit *sdio) |
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{ |
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return sdio->tail - sdio->head; |
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} |
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|
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/* |
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* Go grab and pin some userspace pages. Typically we'll get 64 at a time. |
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*/ |
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static inline int dio_refill_pages(struct dio *dio, struct dio_submit *sdio) |
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{ |
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const enum req_op dio_op = dio->opf & REQ_OP_MASK; |
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ssize_t ret; |
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|
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ret = iov_iter_get_pages2(sdio->iter, dio->pages, LONG_MAX, DIO_PAGES, |
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&sdio->from); |
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|
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if (ret < 0 && sdio->blocks_available && dio_op == REQ_OP_WRITE) { |
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struct page *page = ZERO_PAGE(0); |
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/* |
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* A memory fault, but the filesystem has some outstanding |
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* mapped blocks. We need to use those blocks up to avoid |
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* leaking stale data in the file. |
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*/ |
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if (dio->page_errors == 0) |
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dio->page_errors = ret; |
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get_page(page); |
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dio->pages[0] = page; |
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sdio->head = 0; |
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sdio->tail = 1; |
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sdio->from = 0; |
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sdio->to = PAGE_SIZE; |
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return 0; |
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} |
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|
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if (ret >= 0) { |
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ret += sdio->from; |
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sdio->head = 0; |
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sdio->tail = (ret + PAGE_SIZE - 1) / PAGE_SIZE; |
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sdio->to = ((ret - 1) & (PAGE_SIZE - 1)) + 1; |
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return 0; |
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} |
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return ret; |
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} |
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|
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/* |
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* Get another userspace page. Returns an ERR_PTR on error. Pages are |
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* buffered inside the dio so that we can call get_user_pages() against a |
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* decent number of pages, less frequently. To provide nicer use of the |
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* L1 cache. |
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*/ |
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static inline struct page *dio_get_page(struct dio *dio, |
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struct dio_submit *sdio) |
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{ |
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if (dio_pages_present(sdio) == 0) { |
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int ret; |
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|
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ret = dio_refill_pages(dio, sdio); |
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if (ret) |
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return ERR_PTR(ret); |
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BUG_ON(dio_pages_present(sdio) == 0); |
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} |
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return dio->pages[sdio->head]; |
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} |
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|
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/* |
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* dio_complete() - called when all DIO BIO I/O has been completed |
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* |
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* This drops i_dio_count, lets interested parties know that a DIO operation |
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* has completed, and calculates the resulting return code for the operation. |
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* |
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* It lets the filesystem know if it registered an interest earlier via |
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* get_block. Pass the private field of the map buffer_head so that |
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* filesystems can use it to hold additional state between get_block calls and |
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* dio_complete. |
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*/ |
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static ssize_t dio_complete(struct dio *dio, ssize_t ret, unsigned int flags) |
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{ |
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const enum req_op dio_op = dio->opf & REQ_OP_MASK; |
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loff_t offset = dio->iocb->ki_pos; |
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ssize_t transferred = 0; |
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int err; |
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|
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/* |
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* AIO submission can race with bio completion to get here while |
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* expecting to have the last io completed by bio completion. |
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* In that case -EIOCBQUEUED is in fact not an error we want |
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* to preserve through this call. |
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*/ |
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if (ret == -EIOCBQUEUED) |
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ret = 0; |
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|
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if (dio->result) { |
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transferred = dio->result; |
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|
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/* Check for short read case */ |
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if (dio_op == REQ_OP_READ && |
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((offset + transferred) > dio->i_size)) |
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transferred = dio->i_size - offset; |
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/* ignore EFAULT if some IO has been done */ |
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if (unlikely(ret == -EFAULT) && transferred) |
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ret = 0; |
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} |
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|
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if (ret == 0) |
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ret = dio->page_errors; |
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if (ret == 0) |
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ret = dio->io_error; |
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if (ret == 0) |
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ret = transferred; |
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|
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if (dio->end_io) { |
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// XXX: ki_pos?? |
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err = dio->end_io(dio->iocb, offset, ret, dio->private); |
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if (err) |
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ret = err; |
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} |
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|
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/* |
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* Try again to invalidate clean pages which might have been cached by |
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* non-direct readahead, or faulted in by get_user_pages() if the source |
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* of the write was an mmap'ed region of the file we're writing. Either |
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* one is a pretty crazy thing to do, so we don't support it 100%. If |
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* this invalidation fails, tough, the write still worked... |
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* |
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* And this page cache invalidation has to be after dio->end_io(), as |
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* some filesystems convert unwritten extents to real allocations in |
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* end_io() when necessary, otherwise a racing buffer read would cache |
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* zeros from unwritten extents. |
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*/ |
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if (flags & DIO_COMPLETE_INVALIDATE && |
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ret > 0 && dio_op == REQ_OP_WRITE && |
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dio->inode->i_mapping->nrpages) { |
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err = invalidate_inode_pages2_range(dio->inode->i_mapping, |
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offset >> PAGE_SHIFT, |
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(offset + ret - 1) >> PAGE_SHIFT); |
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if (err) |
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dio_warn_stale_pagecache(dio->iocb->ki_filp); |
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} |
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inode_dio_end(dio->inode); |
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|
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if (flags & DIO_COMPLETE_ASYNC) { |
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/* |
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* generic_write_sync expects ki_pos to have been updated |
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* already, but the submission path only does this for |
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* synchronous I/O. |
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*/ |
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dio->iocb->ki_pos += transferred; |
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|
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if (ret > 0 && dio_op == REQ_OP_WRITE) |
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ret = generic_write_sync(dio->iocb, ret); |
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dio->iocb->ki_complete(dio->iocb, ret); |
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} |
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kmem_cache_free(dio_cache, dio); |
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return ret; |
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} |
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|
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static void dio_aio_complete_work(struct work_struct *work) |
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{ |
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struct dio *dio = container_of(work, struct dio, complete_work); |
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|
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dio_complete(dio, 0, DIO_COMPLETE_ASYNC | DIO_COMPLETE_INVALIDATE); |
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} |
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static blk_status_t dio_bio_complete(struct dio *dio, struct bio *bio); |
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/* |
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* Asynchronous IO callback. |
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*/ |
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static void dio_bio_end_aio(struct bio *bio) |
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{ |
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struct dio *dio = bio->bi_private; |
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const enum req_op dio_op = dio->opf & REQ_OP_MASK; |
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unsigned long remaining; |
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unsigned long flags; |
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bool defer_completion = false; |
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|
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/* cleanup the bio */ |
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dio_bio_complete(dio, bio); |
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|
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spin_lock_irqsave(&dio->bio_lock, flags); |
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remaining = --dio->refcount; |
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if (remaining == 1 && dio->waiter) |
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wake_up_process(dio->waiter); |
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spin_unlock_irqrestore(&dio->bio_lock, flags); |
|
|
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if (remaining == 0) { |
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/* |
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* Defer completion when defer_completion is set or |
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* when the inode has pages mapped and this is AIO write. |
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* We need to invalidate those pages because there is a |
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* chance they contain stale data in the case buffered IO |
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* went in between AIO submission and completion into the |
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* same region. |
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*/ |
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if (dio->result) |
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defer_completion = dio->defer_completion || |
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(dio_op == REQ_OP_WRITE && |
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dio->inode->i_mapping->nrpages); |
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if (defer_completion) { |
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INIT_WORK(&dio->complete_work, dio_aio_complete_work); |
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queue_work(dio->inode->i_sb->s_dio_done_wq, |
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&dio->complete_work); |
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} else { |
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dio_complete(dio, 0, DIO_COMPLETE_ASYNC); |
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} |
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} |
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} |
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|
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/* |
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* The BIO completion handler simply queues the BIO up for the process-context |
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* handler. |
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* |
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* During I/O bi_private points at the dio. After I/O, bi_private is used to |
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* implement a singly-linked list of completed BIOs, at dio->bio_list. |
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*/ |
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static void dio_bio_end_io(struct bio *bio) |
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{ |
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struct dio *dio = bio->bi_private; |
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unsigned long flags; |
|
|
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spin_lock_irqsave(&dio->bio_lock, flags); |
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bio->bi_private = dio->bio_list; |
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dio->bio_list = bio; |
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if (--dio->refcount == 1 && dio->waiter) |
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wake_up_process(dio->waiter); |
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spin_unlock_irqrestore(&dio->bio_lock, flags); |
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} |
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|
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static inline void |
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dio_bio_alloc(struct dio *dio, struct dio_submit *sdio, |
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struct block_device *bdev, |
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sector_t first_sector, int nr_vecs) |
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{ |
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struct bio *bio; |
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|
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/* |
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* bio_alloc() is guaranteed to return a bio when allowed to sleep and |
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* we request a valid number of vectors. |
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*/ |
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bio = bio_alloc(bdev, nr_vecs, dio->opf, GFP_KERNEL); |
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bio->bi_iter.bi_sector = first_sector; |
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if (dio->is_async) |
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bio->bi_end_io = dio_bio_end_aio; |
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else |
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bio->bi_end_io = dio_bio_end_io; |
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sdio->bio = bio; |
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sdio->logical_offset_in_bio = sdio->cur_page_fs_offset; |
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} |
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|
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/* |
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* In the AIO read case we speculatively dirty the pages before starting IO. |
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* During IO completion, any of these pages which happen to have been written |
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* back will be redirtied by bio_check_pages_dirty(). |
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* |
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* bios hold a dio reference between submit_bio and ->end_io. |
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*/ |
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static inline void dio_bio_submit(struct dio *dio, struct dio_submit *sdio) |
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{ |
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const enum req_op dio_op = dio->opf & REQ_OP_MASK; |
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struct bio *bio = sdio->bio; |
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unsigned long flags; |
|
|
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bio->bi_private = dio; |
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|
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spin_lock_irqsave(&dio->bio_lock, flags); |
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dio->refcount++; |
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spin_unlock_irqrestore(&dio->bio_lock, flags); |
|
|
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if (dio->is_async && dio_op == REQ_OP_READ && dio->should_dirty) |
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bio_set_pages_dirty(bio); |
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|
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dio->bio_disk = bio->bi_bdev->bd_disk; |
|
|
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if (sdio->submit_io) |
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sdio->submit_io(bio, dio->inode, sdio->logical_offset_in_bio); |
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else |
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submit_bio(bio); |
|
|
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sdio->bio = NULL; |
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sdio->boundary = 0; |
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sdio->logical_offset_in_bio = 0; |
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} |
|
|
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/* |
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* Release any resources in case of a failure |
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*/ |
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static inline void dio_cleanup(struct dio *dio, struct dio_submit *sdio) |
|
{ |
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while (sdio->head < sdio->tail) |
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put_page(dio->pages[sdio->head++]); |
|
} |
|
|
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/* |
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* Wait for the next BIO to complete. Remove it and return it. NULL is |
|
* returned once all BIOs have been completed. This must only be called once |
|
* all bios have been issued so that dio->refcount can only decrease. This |
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* requires that the caller hold a reference on the dio. |
|
*/ |
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static struct bio *dio_await_one(struct dio *dio) |
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{ |
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unsigned long flags; |
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struct bio *bio = NULL; |
|
|
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spin_lock_irqsave(&dio->bio_lock, flags); |
|
|
|
/* |
|
* Wait as long as the list is empty and there are bios in flight. bio |
|
* completion drops the count, maybe adds to the list, and wakes while |
|
* holding the bio_lock so we don't need set_current_state()'s barrier |
|
* and can call it after testing our condition. |
|
*/ |
|
while (dio->refcount > 1 && dio->bio_list == NULL) { |
|
__set_current_state(TASK_UNINTERRUPTIBLE); |
|
dio->waiter = current; |
|
spin_unlock_irqrestore(&dio->bio_lock, flags); |
|
blk_io_schedule(); |
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/* wake up sets us TASK_RUNNING */ |
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spin_lock_irqsave(&dio->bio_lock, flags); |
|
dio->waiter = NULL; |
|
} |
|
if (dio->bio_list) { |
|
bio = dio->bio_list; |
|
dio->bio_list = bio->bi_private; |
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} |
|
spin_unlock_irqrestore(&dio->bio_lock, flags); |
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return bio; |
|
} |
|
|
|
/* |
|
* Process one completed BIO. No locks are held. |
|
*/ |
|
static blk_status_t dio_bio_complete(struct dio *dio, struct bio *bio) |
|
{ |
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blk_status_t err = bio->bi_status; |
|
const enum req_op dio_op = dio->opf & REQ_OP_MASK; |
|
bool should_dirty = dio_op == REQ_OP_READ && dio->should_dirty; |
|
|
|
if (err) { |
|
if (err == BLK_STS_AGAIN && (bio->bi_opf & REQ_NOWAIT)) |
|
dio->io_error = -EAGAIN; |
|
else |
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dio->io_error = -EIO; |
|
} |
|
|
|
if (dio->is_async && should_dirty) { |
|
bio_check_pages_dirty(bio); /* transfers ownership */ |
|
} else { |
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bio_release_pages(bio, should_dirty); |
|
bio_put(bio); |
|
} |
|
return err; |
|
} |
|
|
|
/* |
|
* Wait on and process all in-flight BIOs. This must only be called once |
|
* all bios have been issued so that the refcount can only decrease. |
|
* This just waits for all bios to make it through dio_bio_complete. IO |
|
* errors are propagated through dio->io_error and should be propagated via |
|
* dio_complete(). |
|
*/ |
|
static void dio_await_completion(struct dio *dio) |
|
{ |
|
struct bio *bio; |
|
do { |
|
bio = dio_await_one(dio); |
|
if (bio) |
|
dio_bio_complete(dio, bio); |
|
} while (bio); |
|
} |
|
|
|
/* |
|
* A really large O_DIRECT read or write can generate a lot of BIOs. So |
|
* to keep the memory consumption sane we periodically reap any completed BIOs |
|
* during the BIO generation phase. |
|
* |
|
* This also helps to limit the peak amount of pinned userspace memory. |
|
*/ |
|
static inline int dio_bio_reap(struct dio *dio, struct dio_submit *sdio) |
|
{ |
|
int ret = 0; |
|
|
|
if (sdio->reap_counter++ >= 64) { |
|
while (dio->bio_list) { |
|
unsigned long flags; |
|
struct bio *bio; |
|
int ret2; |
|
|
|
spin_lock_irqsave(&dio->bio_lock, flags); |
|
bio = dio->bio_list; |
|
dio->bio_list = bio->bi_private; |
|
spin_unlock_irqrestore(&dio->bio_lock, flags); |
|
ret2 = blk_status_to_errno(dio_bio_complete(dio, bio)); |
|
if (ret == 0) |
|
ret = ret2; |
|
} |
|
sdio->reap_counter = 0; |
|
} |
|
return ret; |
|
} |
|
|
|
/* |
|
* Create workqueue for deferred direct IO completions. We allocate the |
|
* workqueue when it's first needed. This avoids creating workqueue for |
|
* filesystems that don't need it and also allows us to create the workqueue |
|
* late enough so the we can include s_id in the name of the workqueue. |
|
*/ |
|
int sb_init_dio_done_wq(struct super_block *sb) |
|
{ |
|
struct workqueue_struct *old; |
|
struct workqueue_struct *wq = alloc_workqueue("dio/%s", |
|
WQ_MEM_RECLAIM, 0, |
|
sb->s_id); |
|
if (!wq) |
|
return -ENOMEM; |
|
/* |
|
* This has to be atomic as more DIOs can race to create the workqueue |
|
*/ |
|
old = cmpxchg(&sb->s_dio_done_wq, NULL, wq); |
|
/* Someone created workqueue before us? Free ours... */ |
|
if (old) |
|
destroy_workqueue(wq); |
|
return 0; |
|
} |
|
|
|
static int dio_set_defer_completion(struct dio *dio) |
|
{ |
|
struct super_block *sb = dio->inode->i_sb; |
|
|
|
if (dio->defer_completion) |
|
return 0; |
|
dio->defer_completion = true; |
|
if (!sb->s_dio_done_wq) |
|
return sb_init_dio_done_wq(sb); |
|
return 0; |
|
} |
|
|
|
/* |
|
* Call into the fs to map some more disk blocks. We record the current number |
|
* of available blocks at sdio->blocks_available. These are in units of the |
|
* fs blocksize, i_blocksize(inode). |
|
* |
|
* The fs is allowed to map lots of blocks at once. If it wants to do that, |
|
* it uses the passed inode-relative block number as the file offset, as usual. |
|
* |
|
* get_block() is passed the number of i_blkbits-sized blocks which direct_io |
|
* has remaining to do. The fs should not map more than this number of blocks. |
|
* |
|
* If the fs has mapped a lot of blocks, it should populate bh->b_size to |
|
* indicate how much contiguous disk space has been made available at |
|
* bh->b_blocknr. |
|
* |
|
* If *any* of the mapped blocks are new, then the fs must set buffer_new(). |
|
* This isn't very efficient... |
|
* |
|
* In the case of filesystem holes: the fs may return an arbitrarily-large |
|
* hole by returning an appropriate value in b_size and by clearing |
|
* buffer_mapped(). However the direct-io code will only process holes one |
|
* block at a time - it will repeatedly call get_block() as it walks the hole. |
|
*/ |
|
static int get_more_blocks(struct dio *dio, struct dio_submit *sdio, |
|
struct buffer_head *map_bh) |
|
{ |
|
const enum req_op dio_op = dio->opf & REQ_OP_MASK; |
|
int ret; |
|
sector_t fs_startblk; /* Into file, in filesystem-sized blocks */ |
|
sector_t fs_endblk; /* Into file, in filesystem-sized blocks */ |
|
unsigned long fs_count; /* Number of filesystem-sized blocks */ |
|
int create; |
|
unsigned int i_blkbits = sdio->blkbits + sdio->blkfactor; |
|
loff_t i_size; |
|
|
|
/* |
|
* If there was a memory error and we've overwritten all the |
|
* mapped blocks then we can now return that memory error |
|
*/ |
|
ret = dio->page_errors; |
|
if (ret == 0) { |
|
BUG_ON(sdio->block_in_file >= sdio->final_block_in_request); |
|
fs_startblk = sdio->block_in_file >> sdio->blkfactor; |
|
fs_endblk = (sdio->final_block_in_request - 1) >> |
|
sdio->blkfactor; |
|
fs_count = fs_endblk - fs_startblk + 1; |
|
|
|
map_bh->b_state = 0; |
|
map_bh->b_size = fs_count << i_blkbits; |
|
|
|
/* |
|
* For writes that could fill holes inside i_size on a |
|
* DIO_SKIP_HOLES filesystem we forbid block creations: only |
|
* overwrites are permitted. We will return early to the caller |
|
* once we see an unmapped buffer head returned, and the caller |
|
* will fall back to buffered I/O. |
|
* |
|
* Otherwise the decision is left to the get_blocks method, |
|
* which may decide to handle it or also return an unmapped |
|
* buffer head. |
|
*/ |
|
create = dio_op == REQ_OP_WRITE; |
|
if (dio->flags & DIO_SKIP_HOLES) { |
|
i_size = i_size_read(dio->inode); |
|
if (i_size && fs_startblk <= (i_size - 1) >> i_blkbits) |
|
create = 0; |
|
} |
|
|
|
ret = (*sdio->get_block)(dio->inode, fs_startblk, |
|
map_bh, create); |
|
|
|
/* Store for completion */ |
|
dio->private = map_bh->b_private; |
|
|
|
if (ret == 0 && buffer_defer_completion(map_bh)) |
|
ret = dio_set_defer_completion(dio); |
|
} |
|
return ret; |
|
} |
|
|
|
/* |
|
* There is no bio. Make one now. |
|
*/ |
|
static inline int dio_new_bio(struct dio *dio, struct dio_submit *sdio, |
|
sector_t start_sector, struct buffer_head *map_bh) |
|
{ |
|
sector_t sector; |
|
int ret, nr_pages; |
|
|
|
ret = dio_bio_reap(dio, sdio); |
|
if (ret) |
|
goto out; |
|
sector = start_sector << (sdio->blkbits - 9); |
|
nr_pages = bio_max_segs(sdio->pages_in_io); |
|
BUG_ON(nr_pages <= 0); |
|
dio_bio_alloc(dio, sdio, map_bh->b_bdev, sector, nr_pages); |
|
sdio->boundary = 0; |
|
out: |
|
return ret; |
|
} |
|
|
|
/* |
|
* Attempt to put the current chunk of 'cur_page' into the current BIO. If |
|
* that was successful then update final_block_in_bio and take a ref against |
|
* the just-added page. |
|
* |
|
* Return zero on success. Non-zero means the caller needs to start a new BIO. |
|
*/ |
|
static inline int dio_bio_add_page(struct dio_submit *sdio) |
|
{ |
|
int ret; |
|
|
|
ret = bio_add_page(sdio->bio, sdio->cur_page, |
|
sdio->cur_page_len, sdio->cur_page_offset); |
|
if (ret == sdio->cur_page_len) { |
|
/* |
|
* Decrement count only, if we are done with this page |
|
*/ |
|
if ((sdio->cur_page_len + sdio->cur_page_offset) == PAGE_SIZE) |
|
sdio->pages_in_io--; |
|
get_page(sdio->cur_page); |
|
sdio->final_block_in_bio = sdio->cur_page_block + |
|
(sdio->cur_page_len >> sdio->blkbits); |
|
ret = 0; |
|
} else { |
|
ret = 1; |
|
} |
|
return ret; |
|
} |
|
|
|
/* |
|
* Put cur_page under IO. The section of cur_page which is described by |
|
* cur_page_offset,cur_page_len is put into a BIO. The section of cur_page |
|
* starts on-disk at cur_page_block. |
|
* |
|
* We take a ref against the page here (on behalf of its presence in the bio). |
|
* |
|
* The caller of this function is responsible for removing cur_page from the |
|
* dio, and for dropping the refcount which came from that presence. |
|
*/ |
|
static inline int dio_send_cur_page(struct dio *dio, struct dio_submit *sdio, |
|
struct buffer_head *map_bh) |
|
{ |
|
int ret = 0; |
|
|
|
if (sdio->bio) { |
|
loff_t cur_offset = sdio->cur_page_fs_offset; |
|
loff_t bio_next_offset = sdio->logical_offset_in_bio + |
|
sdio->bio->bi_iter.bi_size; |
|
|
|
/* |
|
* See whether this new request is contiguous with the old. |
|
* |
|
* Btrfs cannot handle having logically non-contiguous requests |
|
* submitted. For example if you have |
|
* |
|
* Logical: [0-4095][HOLE][8192-12287] |
|
* Physical: [0-4095] [4096-8191] |
|
* |
|
* We cannot submit those pages together as one BIO. So if our |
|
* current logical offset in the file does not equal what would |
|
* be the next logical offset in the bio, submit the bio we |
|
* have. |
|
*/ |
|
if (sdio->final_block_in_bio != sdio->cur_page_block || |
|
cur_offset != bio_next_offset) |
|
dio_bio_submit(dio, sdio); |
|
} |
|
|
|
if (sdio->bio == NULL) { |
|
ret = dio_new_bio(dio, sdio, sdio->cur_page_block, map_bh); |
|
if (ret) |
|
goto out; |
|
} |
|
|
|
if (dio_bio_add_page(sdio) != 0) { |
|
dio_bio_submit(dio, sdio); |
|
ret = dio_new_bio(dio, sdio, sdio->cur_page_block, map_bh); |
|
if (ret == 0) { |
|
ret = dio_bio_add_page(sdio); |
|
BUG_ON(ret != 0); |
|
} |
|
} |
|
out: |
|
return ret; |
|
} |
|
|
|
/* |
|
* An autonomous function to put a chunk of a page under deferred IO. |
|
* |
|
* The caller doesn't actually know (or care) whether this piece of page is in |
|
* a BIO, or is under IO or whatever. We just take care of all possible |
|
* situations here. The separation between the logic of do_direct_IO() and |
|
* that of submit_page_section() is important for clarity. Please don't break. |
|
* |
|
* The chunk of page starts on-disk at blocknr. |
|
* |
|
* We perform deferred IO, by recording the last-submitted page inside our |
|
* private part of the dio structure. If possible, we just expand the IO |
|
* across that page here. |
|
* |
|
* If that doesn't work out then we put the old page into the bio and add this |
|
* page to the dio instead. |
|
*/ |
|
static inline int |
|
submit_page_section(struct dio *dio, struct dio_submit *sdio, struct page *page, |
|
unsigned offset, unsigned len, sector_t blocknr, |
|
struct buffer_head *map_bh) |
|
{ |
|
const enum req_op dio_op = dio->opf & REQ_OP_MASK; |
|
int ret = 0; |
|
int boundary = sdio->boundary; /* dio_send_cur_page may clear it */ |
|
|
|
if (dio_op == REQ_OP_WRITE) { |
|
/* |
|
* Read accounting is performed in submit_bio() |
|
*/ |
|
task_io_account_write(len); |
|
} |
|
|
|
/* |
|
* Can we just grow the current page's presence in the dio? |
|
*/ |
|
if (sdio->cur_page == page && |
|
sdio->cur_page_offset + sdio->cur_page_len == offset && |
|
sdio->cur_page_block + |
|
(sdio->cur_page_len >> sdio->blkbits) == blocknr) { |
|
sdio->cur_page_len += len; |
|
goto out; |
|
} |
|
|
|
/* |
|
* If there's a deferred page already there then send it. |
|
*/ |
|
if (sdio->cur_page) { |
|
ret = dio_send_cur_page(dio, sdio, map_bh); |
|
put_page(sdio->cur_page); |
|
sdio->cur_page = NULL; |
|
if (ret) |
|
return ret; |
|
} |
|
|
|
get_page(page); /* It is in dio */ |
|
sdio->cur_page = page; |
|
sdio->cur_page_offset = offset; |
|
sdio->cur_page_len = len; |
|
sdio->cur_page_block = blocknr; |
|
sdio->cur_page_fs_offset = sdio->block_in_file << sdio->blkbits; |
|
out: |
|
/* |
|
* If boundary then we want to schedule the IO now to |
|
* avoid metadata seeks. |
|
*/ |
|
if (boundary) { |
|
ret = dio_send_cur_page(dio, sdio, map_bh); |
|
if (sdio->bio) |
|
dio_bio_submit(dio, sdio); |
|
put_page(sdio->cur_page); |
|
sdio->cur_page = NULL; |
|
} |
|
return ret; |
|
} |
|
|
|
/* |
|
* If we are not writing the entire block and get_block() allocated |
|
* the block for us, we need to fill-in the unused portion of the |
|
* block with zeros. This happens only if user-buffer, fileoffset or |
|
* io length is not filesystem block-size multiple. |
|
* |
|
* `end' is zero if we're doing the start of the IO, 1 at the end of the |
|
* IO. |
|
*/ |
|
static inline void dio_zero_block(struct dio *dio, struct dio_submit *sdio, |
|
int end, struct buffer_head *map_bh) |
|
{ |
|
unsigned dio_blocks_per_fs_block; |
|
unsigned this_chunk_blocks; /* In dio_blocks */ |
|
unsigned this_chunk_bytes; |
|
struct page *page; |
|
|
|
sdio->start_zero_done = 1; |
|
if (!sdio->blkfactor || !buffer_new(map_bh)) |
|
return; |
|
|
|
dio_blocks_per_fs_block = 1 << sdio->blkfactor; |
|
this_chunk_blocks = sdio->block_in_file & (dio_blocks_per_fs_block - 1); |
|
|
|
if (!this_chunk_blocks) |
|
return; |
|
|
|
/* |
|
* We need to zero out part of an fs block. It is either at the |
|
* beginning or the end of the fs block. |
|
*/ |
|
if (end) |
|
this_chunk_blocks = dio_blocks_per_fs_block - this_chunk_blocks; |
|
|
|
this_chunk_bytes = this_chunk_blocks << sdio->blkbits; |
|
|
|
page = ZERO_PAGE(0); |
|
if (submit_page_section(dio, sdio, page, 0, this_chunk_bytes, |
|
sdio->next_block_for_io, map_bh)) |
|
return; |
|
|
|
sdio->next_block_for_io += this_chunk_blocks; |
|
} |
|
|
|
/* |
|
* Walk the user pages, and the file, mapping blocks to disk and generating |
|
* a sequence of (page,offset,len,block) mappings. These mappings are injected |
|
* into submit_page_section(), which takes care of the next stage of submission |
|
* |
|
* Direct IO against a blockdev is different from a file. Because we can |
|
* happily perform page-sized but 512-byte aligned IOs. It is important that |
|
* blockdev IO be able to have fine alignment and large sizes. |
|
* |
|
* So what we do is to permit the ->get_block function to populate bh.b_size |
|
* with the size of IO which is permitted at this offset and this i_blkbits. |
|
* |
|
* For best results, the blockdev should be set up with 512-byte i_blkbits and |
|
* it should set b_size to PAGE_SIZE or more inside get_block(). This gives |
|
* fine alignment but still allows this function to work in PAGE_SIZE units. |
|
*/ |
|
static int do_direct_IO(struct dio *dio, struct dio_submit *sdio, |
|
struct buffer_head *map_bh) |
|
{ |
|
const enum req_op dio_op = dio->opf & REQ_OP_MASK; |
|
const unsigned blkbits = sdio->blkbits; |
|
const unsigned i_blkbits = blkbits + sdio->blkfactor; |
|
int ret = 0; |
|
|
|
while (sdio->block_in_file < sdio->final_block_in_request) { |
|
struct page *page; |
|
size_t from, to; |
|
|
|
page = dio_get_page(dio, sdio); |
|
if (IS_ERR(page)) { |
|
ret = PTR_ERR(page); |
|
goto out; |
|
} |
|
from = sdio->head ? 0 : sdio->from; |
|
to = (sdio->head == sdio->tail - 1) ? sdio->to : PAGE_SIZE; |
|
sdio->head++; |
|
|
|
while (from < to) { |
|
unsigned this_chunk_bytes; /* # of bytes mapped */ |
|
unsigned this_chunk_blocks; /* # of blocks */ |
|
unsigned u; |
|
|
|
if (sdio->blocks_available == 0) { |
|
/* |
|
* Need to go and map some more disk |
|
*/ |
|
unsigned long blkmask; |
|
unsigned long dio_remainder; |
|
|
|
ret = get_more_blocks(dio, sdio, map_bh); |
|
if (ret) { |
|
put_page(page); |
|
goto out; |
|
} |
|
if (!buffer_mapped(map_bh)) |
|
goto do_holes; |
|
|
|
sdio->blocks_available = |
|
map_bh->b_size >> blkbits; |
|
sdio->next_block_for_io = |
|
map_bh->b_blocknr << sdio->blkfactor; |
|
if (buffer_new(map_bh)) { |
|
clean_bdev_aliases( |
|
map_bh->b_bdev, |
|
map_bh->b_blocknr, |
|
map_bh->b_size >> i_blkbits); |
|
} |
|
|
|
if (!sdio->blkfactor) |
|
goto do_holes; |
|
|
|
blkmask = (1 << sdio->blkfactor) - 1; |
|
dio_remainder = (sdio->block_in_file & blkmask); |
|
|
|
/* |
|
* If we are at the start of IO and that IO |
|
* starts partway into a fs-block, |
|
* dio_remainder will be non-zero. If the IO |
|
* is a read then we can simply advance the IO |
|
* cursor to the first block which is to be |
|
* read. But if the IO is a write and the |
|
* block was newly allocated we cannot do that; |
|
* the start of the fs block must be zeroed out |
|
* on-disk |
|
*/ |
|
if (!buffer_new(map_bh)) |
|
sdio->next_block_for_io += dio_remainder; |
|
sdio->blocks_available -= dio_remainder; |
|
} |
|
do_holes: |
|
/* Handle holes */ |
|
if (!buffer_mapped(map_bh)) { |
|
loff_t i_size_aligned; |
|
|
|
/* AKPM: eargh, -ENOTBLK is a hack */ |
|
if (dio_op == REQ_OP_WRITE) { |
|
put_page(page); |
|
return -ENOTBLK; |
|
} |
|
|
|
/* |
|
* Be sure to account for a partial block as the |
|
* last block in the file |
|
*/ |
|
i_size_aligned = ALIGN(i_size_read(dio->inode), |
|
1 << blkbits); |
|
if (sdio->block_in_file >= |
|
i_size_aligned >> blkbits) { |
|
/* We hit eof */ |
|
put_page(page); |
|
goto out; |
|
} |
|
zero_user(page, from, 1 << blkbits); |
|
sdio->block_in_file++; |
|
from += 1 << blkbits; |
|
dio->result += 1 << blkbits; |
|
goto next_block; |
|
} |
|
|
|
/* |
|
* If we're performing IO which has an alignment which |
|
* is finer than the underlying fs, go check to see if |
|
* we must zero out the start of this block. |
|
*/ |
|
if (unlikely(sdio->blkfactor && !sdio->start_zero_done)) |
|
dio_zero_block(dio, sdio, 0, map_bh); |
|
|
|
/* |
|
* Work out, in this_chunk_blocks, how much disk we |
|
* can add to this page |
|
*/ |
|
this_chunk_blocks = sdio->blocks_available; |
|
u = (to - from) >> blkbits; |
|
if (this_chunk_blocks > u) |
|
this_chunk_blocks = u; |
|
u = sdio->final_block_in_request - sdio->block_in_file; |
|
if (this_chunk_blocks > u) |
|
this_chunk_blocks = u; |
|
this_chunk_bytes = this_chunk_blocks << blkbits; |
|
BUG_ON(this_chunk_bytes == 0); |
|
|
|
if (this_chunk_blocks == sdio->blocks_available) |
|
sdio->boundary = buffer_boundary(map_bh); |
|
ret = submit_page_section(dio, sdio, page, |
|
from, |
|
this_chunk_bytes, |
|
sdio->next_block_for_io, |
|
map_bh); |
|
if (ret) { |
|
put_page(page); |
|
goto out; |
|
} |
|
sdio->next_block_for_io += this_chunk_blocks; |
|
|
|
sdio->block_in_file += this_chunk_blocks; |
|
from += this_chunk_bytes; |
|
dio->result += this_chunk_bytes; |
|
sdio->blocks_available -= this_chunk_blocks; |
|
next_block: |
|
BUG_ON(sdio->block_in_file > sdio->final_block_in_request); |
|
if (sdio->block_in_file == sdio->final_block_in_request) |
|
break; |
|
} |
|
|
|
/* Drop the ref which was taken in get_user_pages() */ |
|
put_page(page); |
|
} |
|
out: |
|
return ret; |
|
} |
|
|
|
static inline int drop_refcount(struct dio *dio) |
|
{ |
|
int ret2; |
|
unsigned long flags; |
|
|
|
/* |
|
* Sync will always be dropping the final ref and completing the |
|
* operation. AIO can if it was a broken operation described above or |
|
* in fact if all the bios race to complete before we get here. In |
|
* that case dio_complete() translates the EIOCBQUEUED into the proper |
|
* return code that the caller will hand to ->complete(). |
|
* |
|
* This is managed by the bio_lock instead of being an atomic_t so that |
|
* completion paths can drop their ref and use the remaining count to |
|
* decide to wake the submission path atomically. |
|
*/ |
|
spin_lock_irqsave(&dio->bio_lock, flags); |
|
ret2 = --dio->refcount; |
|
spin_unlock_irqrestore(&dio->bio_lock, flags); |
|
return ret2; |
|
} |
|
|
|
/* |
|
* This is a library function for use by filesystem drivers. |
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* |
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* The locking rules are governed by the flags parameter: |
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* - if the flags value contains DIO_LOCKING we use a fancy locking |
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* scheme for dumb filesystems. |
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* For writes this function is called under i_mutex and returns with |
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* i_mutex held, for reads, i_mutex is not held on entry, but it is |
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* taken and dropped again before returning. |
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* - if the flags value does NOT contain DIO_LOCKING we don't use any |
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* internal locking but rather rely on the filesystem to synchronize |
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* direct I/O reads/writes versus each other and truncate. |
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* |
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* To help with locking against truncate we incremented the i_dio_count |
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* counter before starting direct I/O, and decrement it once we are done. |
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* Truncate can wait for it to reach zero to provide exclusion. It is |
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* expected that filesystem provide exclusion between new direct I/O |
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* and truncates. For DIO_LOCKING filesystems this is done by i_mutex, |
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* but other filesystems need to take care of this on their own. |
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* |
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* NOTE: if you pass "sdio" to anything by pointer make sure that function |
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* is always inlined. Otherwise gcc is unable to split the structure into |
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* individual fields and will generate much worse code. This is important |
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* for the whole file. |
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*/ |
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ssize_t __blockdev_direct_IO(struct kiocb *iocb, struct inode *inode, |
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struct block_device *bdev, struct iov_iter *iter, |
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get_block_t get_block, dio_iodone_t end_io, |
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dio_submit_t submit_io, int flags) |
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{ |
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unsigned i_blkbits = READ_ONCE(inode->i_blkbits); |
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unsigned blkbits = i_blkbits; |
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unsigned blocksize_mask = (1 << blkbits) - 1; |
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ssize_t retval = -EINVAL; |
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const size_t count = iov_iter_count(iter); |
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loff_t offset = iocb->ki_pos; |
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const loff_t end = offset + count; |
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struct dio *dio; |
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struct dio_submit sdio = { 0, }; |
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struct buffer_head map_bh = { 0, }; |
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struct blk_plug plug; |
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unsigned long align = offset | iov_iter_alignment(iter); |
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|
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/* |
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* Avoid references to bdev if not absolutely needed to give |
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* the early prefetch in the caller enough time. |
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*/ |
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|
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/* watch out for a 0 len io from a tricksy fs */ |
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if (iov_iter_rw(iter) == READ && !count) |
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return 0; |
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|
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dio = kmem_cache_alloc(dio_cache, GFP_KERNEL); |
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if (!dio) |
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return -ENOMEM; |
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/* |
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* Believe it or not, zeroing out the page array caused a .5% |
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* performance regression in a database benchmark. So, we take |
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* care to only zero out what's needed. |
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*/ |
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memset(dio, 0, offsetof(struct dio, pages)); |
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|
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dio->flags = flags; |
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if (dio->flags & DIO_LOCKING && iov_iter_rw(iter) == READ) { |
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/* will be released by direct_io_worker */ |
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inode_lock(inode); |
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} |
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|
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/* Once we sampled i_size check for reads beyond EOF */ |
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dio->i_size = i_size_read(inode); |
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if (iov_iter_rw(iter) == READ && offset >= dio->i_size) { |
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retval = 0; |
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goto fail_dio; |
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} |
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|
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if (align & blocksize_mask) { |
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if (bdev) |
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blkbits = blksize_bits(bdev_logical_block_size(bdev)); |
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blocksize_mask = (1 << blkbits) - 1; |
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if (align & blocksize_mask) |
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goto fail_dio; |
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} |
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|
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if (dio->flags & DIO_LOCKING && iov_iter_rw(iter) == READ) { |
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struct address_space *mapping = iocb->ki_filp->f_mapping; |
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|
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retval = filemap_write_and_wait_range(mapping, offset, end - 1); |
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if (retval) |
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goto fail_dio; |
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} |
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|
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/* |
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* For file extending writes updating i_size before data writeouts |
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* complete can expose uninitialized blocks in dumb filesystems. |
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* In that case we need to wait for I/O completion even if asked |
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* for an asynchronous write. |
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*/ |
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if (is_sync_kiocb(iocb)) |
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dio->is_async = false; |
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else if (iov_iter_rw(iter) == WRITE && end > i_size_read(inode)) |
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dio->is_async = false; |
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else |
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dio->is_async = true; |
|
|
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dio->inode = inode; |
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if (iov_iter_rw(iter) == WRITE) { |
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dio->opf = REQ_OP_WRITE | REQ_SYNC | REQ_IDLE; |
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if (iocb->ki_flags & IOCB_NOWAIT) |
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dio->opf |= REQ_NOWAIT; |
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} else { |
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dio->opf = REQ_OP_READ; |
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} |
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|
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/* |
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* For AIO O_(D)SYNC writes we need to defer completions to a workqueue |
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* so that we can call ->fsync. |
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*/ |
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if (dio->is_async && iov_iter_rw(iter) == WRITE) { |
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retval = 0; |
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if (iocb_is_dsync(iocb)) |
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retval = dio_set_defer_completion(dio); |
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else if (!dio->inode->i_sb->s_dio_done_wq) { |
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/* |
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* In case of AIO write racing with buffered read we |
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* need to defer completion. We can't decide this now, |
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* however the workqueue needs to be initialized here. |
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*/ |
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retval = sb_init_dio_done_wq(dio->inode->i_sb); |
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} |
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if (retval) |
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goto fail_dio; |
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} |
|
|
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/* |
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* Will be decremented at I/O completion time. |
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*/ |
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inode_dio_begin(inode); |
|
|
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retval = 0; |
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sdio.blkbits = blkbits; |
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sdio.blkfactor = i_blkbits - blkbits; |
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sdio.block_in_file = offset >> blkbits; |
|
|
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sdio.get_block = get_block; |
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dio->end_io = end_io; |
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sdio.submit_io = submit_io; |
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sdio.final_block_in_bio = -1; |
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sdio.next_block_for_io = -1; |
|
|
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dio->iocb = iocb; |
|
|
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spin_lock_init(&dio->bio_lock); |
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dio->refcount = 1; |
|
|
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dio->should_dirty = user_backed_iter(iter) && iov_iter_rw(iter) == READ; |
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sdio.iter = iter; |
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sdio.final_block_in_request = end >> blkbits; |
|
|
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/* |
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* In case of non-aligned buffers, we may need 2 more |
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* pages since we need to zero out first and last block. |
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*/ |
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if (unlikely(sdio.blkfactor)) |
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sdio.pages_in_io = 2; |
|
|
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sdio.pages_in_io += iov_iter_npages(iter, INT_MAX); |
|
|
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blk_start_plug(&plug); |
|
|
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retval = do_direct_IO(dio, &sdio, &map_bh); |
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if (retval) |
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dio_cleanup(dio, &sdio); |
|
|
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if (retval == -ENOTBLK) { |
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/* |
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* The remaining part of the request will be |
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* handled by buffered I/O when we return |
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*/ |
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retval = 0; |
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} |
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/* |
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* There may be some unwritten disk at the end of a part-written |
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* fs-block-sized block. Go zero that now. |
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*/ |
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dio_zero_block(dio, &sdio, 1, &map_bh); |
|
|
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if (sdio.cur_page) { |
|
ssize_t ret2; |
|
|
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ret2 = dio_send_cur_page(dio, &sdio, &map_bh); |
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if (retval == 0) |
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retval = ret2; |
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put_page(sdio.cur_page); |
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sdio.cur_page = NULL; |
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} |
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if (sdio.bio) |
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dio_bio_submit(dio, &sdio); |
|
|
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blk_finish_plug(&plug); |
|
|
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/* |
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* It is possible that, we return short IO due to end of file. |
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* In that case, we need to release all the pages we got hold on. |
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*/ |
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dio_cleanup(dio, &sdio); |
|
|
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/* |
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* All block lookups have been performed. For READ requests |
|
* we can let i_mutex go now that its achieved its purpose |
|
* of protecting us from looking up uninitialized blocks. |
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*/ |
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if (iov_iter_rw(iter) == READ && (dio->flags & DIO_LOCKING)) |
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inode_unlock(dio->inode); |
|
|
|
/* |
|
* The only time we want to leave bios in flight is when a successful |
|
* partial aio read or full aio write have been setup. In that case |
|
* bio completion will call aio_complete. The only time it's safe to |
|
* call aio_complete is when we return -EIOCBQUEUED, so we key on that. |
|
* This had *better* be the only place that raises -EIOCBQUEUED. |
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*/ |
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BUG_ON(retval == -EIOCBQUEUED); |
|
if (dio->is_async && retval == 0 && dio->result && |
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(iov_iter_rw(iter) == READ || dio->result == count)) |
|
retval = -EIOCBQUEUED; |
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else |
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dio_await_completion(dio); |
|
|
|
if (drop_refcount(dio) == 0) { |
|
retval = dio_complete(dio, retval, DIO_COMPLETE_INVALIDATE); |
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} else |
|
BUG_ON(retval != -EIOCBQUEUED); |
|
|
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return retval; |
|
|
|
fail_dio: |
|
if (dio->flags & DIO_LOCKING && iov_iter_rw(iter) == READ) |
|
inode_unlock(inode); |
|
|
|
kmem_cache_free(dio_cache, dio); |
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return retval; |
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} |
|
EXPORT_SYMBOL(__blockdev_direct_IO); |
|
|
|
static __init int dio_init(void) |
|
{ |
|
dio_cache = KMEM_CACHE(dio, SLAB_PANIC); |
|
return 0; |
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} |
|
module_init(dio_init)
|
|
|