4 * Copyright (C) 2002, Linus Torvalds.
8 * 04Jul2002 Andrew Morton
10 * 11Sep2002 janetinc@us.ibm.com
11 * added readv/writev support.
12 * 29Oct2002 Andrew Morton
13 * rewrote bio_add_page() support.
14 * 30Oct2002 pbadari@us.ibm.com
15 * added support for non-aligned IO.
16 * 06Nov2002 pbadari@us.ibm.com
17 * added asynchronous IO support.
18 * 21Jul2003 nathans@sgi.com
19 * added IO completion notifier.
22 #include <linux/kernel.h>
23 #include <linux/module.h>
24 #include <linux/types.h>
27 #include <linux/slab.h>
28 #include <linux/highmem.h>
29 #include <linux/pagemap.h>
30 #include <linux/task_io_accounting_ops.h>
31 #include <linux/bio.h>
32 #include <linux/wait.h>
33 #include <linux/err.h>
34 #include <linux/blkdev.h>
35 #include <linux/buffer_head.h>
36 #include <linux/rwsem.h>
37 #include <linux/uio.h>
38 #include <linux/atomic.h>
39 #include <linux/prefetch.h>
42 * How many user pages to map in one call to get_user_pages(). This determines
43 * the size of a structure in the slab cache
48 * This code generally works in units of "dio_blocks". A dio_block is
49 * somewhere between the hard sector size and the filesystem block size. it
50 * is determined on a per-invocation basis. When talking to the filesystem
51 * we need to convert dio_blocks to fs_blocks by scaling the dio_block quantity
52 * down by dio->blkfactor. Similarly, fs-blocksize quantities are converted
53 * to bio_block quantities by shifting left by blkfactor.
55 * If blkfactor is zero then the user's request was aligned to the filesystem's
59 /* dio_state only used in the submission path */
62 struct bio
*bio
; /* bio under assembly */
63 unsigned blkbits
; /* doesn't change */
64 unsigned blkfactor
; /* When we're using an alignment which
65 is finer than the filesystem's soft
66 blocksize, this specifies how much
67 finer. blkfactor=2 means 1/4-block
68 alignment. Does not change */
69 unsigned start_zero_done
; /* flag: sub-blocksize zeroing has
70 been performed at the start of a
72 int pages_in_io
; /* approximate total IO pages */
73 sector_t block_in_file
; /* Current offset into the underlying
74 file in dio_block units. */
75 unsigned blocks_available
; /* At block_in_file. changes */
76 int reap_counter
; /* rate limit reaping */
77 sector_t final_block_in_request
;/* doesn't change */
78 int boundary
; /* prev block is at a boundary */
79 get_block_t
*get_block
; /* block mapping function */
80 dio_submit_t
*submit_io
; /* IO submition function */
82 loff_t logical_offset_in_bio
; /* current first logical block in bio */
83 sector_t final_block_in_bio
; /* current final block in bio + 1 */
84 sector_t next_block_for_io
; /* next block to be put under IO,
85 in dio_blocks units */
88 * Deferred addition of a page to the dio. These variables are
89 * private to dio_send_cur_page(), submit_page_section() and
92 struct page
*cur_page
; /* The page */
93 unsigned cur_page_offset
; /* Offset into it, in bytes */
94 unsigned cur_page_len
; /* Nr of bytes at cur_page_offset */
95 sector_t cur_page_block
; /* Where it starts */
96 loff_t cur_page_fs_offset
; /* Offset in file */
98 struct iov_iter
*iter
;
100 * Page queue. These variables belong to dio_refill_pages() and
103 unsigned head
; /* next page to process */
104 unsigned tail
; /* last valid page + 1 */
108 /* dio_state communicated between submission path and end_io */
110 int flags
; /* doesn't change */
113 loff_t i_size
; /* i_size when submitted */
114 dio_iodone_t
*end_io
; /* IO completion function */
116 void *private; /* copy from map_bh.b_private */
118 /* BIO completion state */
119 spinlock_t bio_lock
; /* protects BIO fields below */
120 int page_errors
; /* errno from get_user_pages() */
121 int is_async
; /* is IO async ? */
122 bool defer_completion
; /* defer AIO completion to workqueue? */
123 int io_error
; /* IO error in completion path */
124 unsigned long refcount
; /* direct_io_worker() and bios */
125 struct bio
*bio_list
; /* singly linked via bi_private */
126 struct task_struct
*waiter
; /* waiting task (NULL if none) */
128 /* AIO related stuff */
129 struct kiocb
*iocb
; /* kiocb */
130 ssize_t result
; /* IO result */
133 * pages[] (and any fields placed after it) are not zeroed out at
134 * allocation time. Don't add new fields after pages[] unless you
135 * wish that they not be zeroed.
138 struct page
*pages
[DIO_PAGES
]; /* page buffer */
139 struct work_struct complete_work
;/* deferred AIO completion */
141 } ____cacheline_aligned_in_smp
;
143 static struct kmem_cache
*dio_cache __read_mostly
;
146 * How many pages are in the queue?
148 static inline unsigned dio_pages_present(struct dio_submit
*sdio
)
150 return sdio
->tail
- sdio
->head
;
154 * Go grab and pin some userspace pages. Typically we'll get 64 at a time.
156 static inline int dio_refill_pages(struct dio
*dio
, struct dio_submit
*sdio
)
160 ret
= iov_iter_get_pages(sdio
->iter
, dio
->pages
, LONG_MAX
, DIO_PAGES
,
163 if (ret
< 0 && sdio
->blocks_available
&& (dio
->rw
& WRITE
)) {
164 struct page
*page
= ZERO_PAGE(0);
166 * A memory fault, but the filesystem has some outstanding
167 * mapped blocks. We need to use those blocks up to avoid
168 * leaking stale data in the file.
170 if (dio
->page_errors
== 0)
171 dio
->page_errors
= ret
;
172 page_cache_get(page
);
173 dio
->pages
[0] = page
;
177 sdio
->to
= PAGE_SIZE
;
182 iov_iter_advance(sdio
->iter
, ret
);
185 sdio
->tail
= (ret
+ PAGE_SIZE
- 1) / PAGE_SIZE
;
186 sdio
->to
= ((ret
- 1) & (PAGE_SIZE
- 1)) + 1;
193 * Get another userspace page. Returns an ERR_PTR on error. Pages are
194 * buffered inside the dio so that we can call get_user_pages() against a
195 * decent number of pages, less frequently. To provide nicer use of the
198 static inline struct page
*dio_get_page(struct dio
*dio
,
199 struct dio_submit
*sdio
)
201 if (dio_pages_present(sdio
) == 0) {
204 ret
= dio_refill_pages(dio
, sdio
);
207 BUG_ON(dio_pages_present(sdio
) == 0);
209 return dio
->pages
[sdio
->head
];
213 * dio_complete() - called when all DIO BIO I/O has been completed
214 * @offset: the byte offset in the file of the completed operation
216 * This drops i_dio_count, lets interested parties know that a DIO operation
217 * has completed, and calculates the resulting return code for the operation.
219 * It lets the filesystem know if it registered an interest earlier via
220 * get_block. Pass the private field of the map buffer_head so that
221 * filesystems can use it to hold additional state between get_block calls and
224 static ssize_t
dio_complete(struct dio
*dio
, loff_t offset
, ssize_t ret
,
227 ssize_t transferred
= 0;
230 * AIO submission can race with bio completion to get here while
231 * expecting to have the last io completed by bio completion.
232 * In that case -EIOCBQUEUED is in fact not an error we want
233 * to preserve through this call.
235 if (ret
== -EIOCBQUEUED
)
239 transferred
= dio
->result
;
241 /* Check for short read case */
242 if ((dio
->rw
== READ
) && ((offset
+ transferred
) > dio
->i_size
))
243 transferred
= dio
->i_size
- offset
;
247 ret
= dio
->page_errors
;
253 if (dio
->end_io
&& dio
->result
)
254 dio
->end_io(dio
->iocb
, offset
, transferred
, dio
->private);
256 inode_dio_done(dio
->inode
);
258 if (dio
->rw
& WRITE
) {
261 err
= generic_write_sync(dio
->iocb
->ki_filp
, offset
,
263 if (err
< 0 && ret
> 0)
267 dio
->iocb
->ki_complete(dio
->iocb
, ret
, 0);
270 kmem_cache_free(dio_cache
, dio
);
274 static void dio_aio_complete_work(struct work_struct
*work
)
276 struct dio
*dio
= container_of(work
, struct dio
, complete_work
);
278 dio_complete(dio
, dio
->iocb
->ki_pos
, 0, true);
281 static int dio_bio_complete(struct dio
*dio
, struct bio
*bio
);
284 * Asynchronous IO callback.
286 static void dio_bio_end_aio(struct bio
*bio
, int error
)
288 struct dio
*dio
= bio
->bi_private
;
289 unsigned long remaining
;
292 /* cleanup the bio */
293 dio_bio_complete(dio
, bio
);
295 spin_lock_irqsave(&dio
->bio_lock
, flags
);
296 remaining
= --dio
->refcount
;
297 if (remaining
== 1 && dio
->waiter
)
298 wake_up_process(dio
->waiter
);
299 spin_unlock_irqrestore(&dio
->bio_lock
, flags
);
301 if (remaining
== 0) {
302 if (dio
->result
&& dio
->defer_completion
) {
303 INIT_WORK(&dio
->complete_work
, dio_aio_complete_work
);
304 queue_work(dio
->inode
->i_sb
->s_dio_done_wq
,
305 &dio
->complete_work
);
307 dio_complete(dio
, dio
->iocb
->ki_pos
, 0, true);
313 * The BIO completion handler simply queues the BIO up for the process-context
316 * During I/O bi_private points at the dio. After I/O, bi_private is used to
317 * implement a singly-linked list of completed BIOs, at dio->bio_list.
319 static void dio_bio_end_io(struct bio
*bio
, int error
)
321 struct dio
*dio
= bio
->bi_private
;
324 spin_lock_irqsave(&dio
->bio_lock
, flags
);
325 bio
->bi_private
= dio
->bio_list
;
327 if (--dio
->refcount
== 1 && dio
->waiter
)
328 wake_up_process(dio
->waiter
);
329 spin_unlock_irqrestore(&dio
->bio_lock
, flags
);
333 * dio_end_io - handle the end io action for the given bio
334 * @bio: The direct io bio thats being completed
335 * @error: Error if there was one
337 * This is meant to be called by any filesystem that uses their own dio_submit_t
338 * so that the DIO specific endio actions are dealt with after the filesystem
339 * has done it's completion work.
341 void dio_end_io(struct bio
*bio
, int error
)
343 struct dio
*dio
= bio
->bi_private
;
346 dio_bio_end_aio(bio
, error
);
348 dio_bio_end_io(bio
, error
);
350 EXPORT_SYMBOL_GPL(dio_end_io
);
353 dio_bio_alloc(struct dio
*dio
, struct dio_submit
*sdio
,
354 struct block_device
*bdev
,
355 sector_t first_sector
, int nr_vecs
)
360 * bio_alloc() is guaranteed to return a bio when called with
361 * __GFP_WAIT and we request a valid number of vectors.
363 bio
= bio_alloc(GFP_KERNEL
, nr_vecs
);
366 bio
->bi_iter
.bi_sector
= first_sector
;
368 bio
->bi_end_io
= dio_bio_end_aio
;
370 bio
->bi_end_io
= dio_bio_end_io
;
373 sdio
->logical_offset_in_bio
= sdio
->cur_page_fs_offset
;
377 * In the AIO read case we speculatively dirty the pages before starting IO.
378 * During IO completion, any of these pages which happen to have been written
379 * back will be redirtied by bio_check_pages_dirty().
381 * bios hold a dio reference between submit_bio and ->end_io.
383 static inline void dio_bio_submit(struct dio
*dio
, struct dio_submit
*sdio
)
385 struct bio
*bio
= sdio
->bio
;
388 bio
->bi_private
= dio
;
390 spin_lock_irqsave(&dio
->bio_lock
, flags
);
392 spin_unlock_irqrestore(&dio
->bio_lock
, flags
);
394 if (dio
->is_async
&& dio
->rw
== READ
)
395 bio_set_pages_dirty(bio
);
398 sdio
->submit_io(dio
->rw
, bio
, dio
->inode
,
399 sdio
->logical_offset_in_bio
);
401 submit_bio(dio
->rw
, bio
);
405 sdio
->logical_offset_in_bio
= 0;
409 * Release any resources in case of a failure
411 static inline void dio_cleanup(struct dio
*dio
, struct dio_submit
*sdio
)
413 while (sdio
->head
< sdio
->tail
)
414 page_cache_release(dio
->pages
[sdio
->head
++]);
418 * Wait for the next BIO to complete. Remove it and return it. NULL is
419 * returned once all BIOs have been completed. This must only be called once
420 * all bios have been issued so that dio->refcount can only decrease. This
421 * requires that that the caller hold a reference on the dio.
423 static struct bio
*dio_await_one(struct dio
*dio
)
426 struct bio
*bio
= NULL
;
428 spin_lock_irqsave(&dio
->bio_lock
, flags
);
431 * Wait as long as the list is empty and there are bios in flight. bio
432 * completion drops the count, maybe adds to the list, and wakes while
433 * holding the bio_lock so we don't need set_current_state()'s barrier
434 * and can call it after testing our condition.
436 while (dio
->refcount
> 1 && dio
->bio_list
== NULL
) {
437 __set_current_state(TASK_UNINTERRUPTIBLE
);
438 dio
->waiter
= current
;
439 spin_unlock_irqrestore(&dio
->bio_lock
, flags
);
441 /* wake up sets us TASK_RUNNING */
442 spin_lock_irqsave(&dio
->bio_lock
, flags
);
447 dio
->bio_list
= bio
->bi_private
;
449 spin_unlock_irqrestore(&dio
->bio_lock
, flags
);
454 * Process one completed BIO. No locks are held.
456 static int dio_bio_complete(struct dio
*dio
, struct bio
*bio
)
458 const int uptodate
= test_bit(BIO_UPTODATE
, &bio
->bi_flags
);
459 struct bio_vec
*bvec
;
463 dio
->io_error
= -EIO
;
465 if (dio
->is_async
&& dio
->rw
== READ
) {
466 bio_check_pages_dirty(bio
); /* transfers ownership */
468 bio_for_each_segment_all(bvec
, bio
, i
) {
469 struct page
*page
= bvec
->bv_page
;
471 if (dio
->rw
== READ
&& !PageCompound(page
))
472 set_page_dirty_lock(page
);
473 page_cache_release(page
);
477 return uptodate
? 0 : -EIO
;
481 * Wait on and process all in-flight BIOs. This must only be called once
482 * all bios have been issued so that the refcount can only decrease.
483 * This just waits for all bios to make it through dio_bio_complete. IO
484 * errors are propagated through dio->io_error and should be propagated via
487 static void dio_await_completion(struct dio
*dio
)
491 bio
= dio_await_one(dio
);
493 dio_bio_complete(dio
, bio
);
498 * A really large O_DIRECT read or write can generate a lot of BIOs. So
499 * to keep the memory consumption sane we periodically reap any completed BIOs
500 * during the BIO generation phase.
502 * This also helps to limit the peak amount of pinned userspace memory.
504 static inline int dio_bio_reap(struct dio
*dio
, struct dio_submit
*sdio
)
508 if (sdio
->reap_counter
++ >= 64) {
509 while (dio
->bio_list
) {
514 spin_lock_irqsave(&dio
->bio_lock
, flags
);
516 dio
->bio_list
= bio
->bi_private
;
517 spin_unlock_irqrestore(&dio
->bio_lock
, flags
);
518 ret2
= dio_bio_complete(dio
, bio
);
522 sdio
->reap_counter
= 0;
528 * Create workqueue for deferred direct IO completions. We allocate the
529 * workqueue when it's first needed. This avoids creating workqueue for
530 * filesystems that don't need it and also allows us to create the workqueue
531 * late enough so the we can include s_id in the name of the workqueue.
533 static int sb_init_dio_done_wq(struct super_block
*sb
)
535 struct workqueue_struct
*old
;
536 struct workqueue_struct
*wq
= alloc_workqueue("dio/%s",
542 * This has to be atomic as more DIOs can race to create the workqueue
544 old
= cmpxchg(&sb
->s_dio_done_wq
, NULL
, wq
);
545 /* Someone created workqueue before us? Free ours... */
547 destroy_workqueue(wq
);
551 static int dio_set_defer_completion(struct dio
*dio
)
553 struct super_block
*sb
= dio
->inode
->i_sb
;
555 if (dio
->defer_completion
)
557 dio
->defer_completion
= true;
558 if (!sb
->s_dio_done_wq
)
559 return sb_init_dio_done_wq(sb
);
564 * Call into the fs to map some more disk blocks. We record the current number
565 * of available blocks at sdio->blocks_available. These are in units of the
566 * fs blocksize, (1 << inode->i_blkbits).
568 * The fs is allowed to map lots of blocks at once. If it wants to do that,
569 * it uses the passed inode-relative block number as the file offset, as usual.
571 * get_block() is passed the number of i_blkbits-sized blocks which direct_io
572 * has remaining to do. The fs should not map more than this number of blocks.
574 * If the fs has mapped a lot of blocks, it should populate bh->b_size to
575 * indicate how much contiguous disk space has been made available at
578 * If *any* of the mapped blocks are new, then the fs must set buffer_new().
579 * This isn't very efficient...
581 * In the case of filesystem holes: the fs may return an arbitrarily-large
582 * hole by returning an appropriate value in b_size and by clearing
583 * buffer_mapped(). However the direct-io code will only process holes one
584 * block at a time - it will repeatedly call get_block() as it walks the hole.
586 static int get_more_blocks(struct dio
*dio
, struct dio_submit
*sdio
,
587 struct buffer_head
*map_bh
)
590 sector_t fs_startblk
; /* Into file, in filesystem-sized blocks */
591 sector_t fs_endblk
; /* Into file, in filesystem-sized blocks */
592 unsigned long fs_count
; /* Number of filesystem-sized blocks */
594 unsigned int i_blkbits
= sdio
->blkbits
+ sdio
->blkfactor
;
597 * If there was a memory error and we've overwritten all the
598 * mapped blocks then we can now return that memory error
600 ret
= dio
->page_errors
;
602 BUG_ON(sdio
->block_in_file
>= sdio
->final_block_in_request
);
603 fs_startblk
= sdio
->block_in_file
>> sdio
->blkfactor
;
604 fs_endblk
= (sdio
->final_block_in_request
- 1) >>
606 fs_count
= fs_endblk
- fs_startblk
+ 1;
609 map_bh
->b_size
= fs_count
<< i_blkbits
;
612 * For writes inside i_size on a DIO_SKIP_HOLES filesystem we
613 * forbid block creations: only overwrites are permitted.
614 * We will return early to the caller once we see an
615 * unmapped buffer head returned, and the caller will fall
616 * back to buffered I/O.
618 * Otherwise the decision is left to the get_blocks method,
619 * which may decide to handle it or also return an unmapped
622 create
= dio
->rw
& WRITE
;
623 if (dio
->flags
& DIO_SKIP_HOLES
) {
624 if (sdio
->block_in_file
< (i_size_read(dio
->inode
) >>
629 ret
= (*sdio
->get_block
)(dio
->inode
, fs_startblk
,
632 /* Store for completion */
633 dio
->private = map_bh
->b_private
;
635 if (ret
== 0 && buffer_defer_completion(map_bh
))
636 ret
= dio_set_defer_completion(dio
);
642 * There is no bio. Make one now.
644 static inline int dio_new_bio(struct dio
*dio
, struct dio_submit
*sdio
,
645 sector_t start_sector
, struct buffer_head
*map_bh
)
650 ret
= dio_bio_reap(dio
, sdio
);
653 sector
= start_sector
<< (sdio
->blkbits
- 9);
654 nr_pages
= min(sdio
->pages_in_io
, bio_get_nr_vecs(map_bh
->b_bdev
));
655 BUG_ON(nr_pages
<= 0);
656 dio_bio_alloc(dio
, sdio
, map_bh
->b_bdev
, sector
, nr_pages
);
663 * Attempt to put the current chunk of 'cur_page' into the current BIO. If
664 * that was successful then update final_block_in_bio and take a ref against
665 * the just-added page.
667 * Return zero on success. Non-zero means the caller needs to start a new BIO.
669 static inline int dio_bio_add_page(struct dio_submit
*sdio
)
673 ret
= bio_add_page(sdio
->bio
, sdio
->cur_page
,
674 sdio
->cur_page_len
, sdio
->cur_page_offset
);
675 if (ret
== sdio
->cur_page_len
) {
677 * Decrement count only, if we are done with this page
679 if ((sdio
->cur_page_len
+ sdio
->cur_page_offset
) == PAGE_SIZE
)
681 page_cache_get(sdio
->cur_page
);
682 sdio
->final_block_in_bio
= sdio
->cur_page_block
+
683 (sdio
->cur_page_len
>> sdio
->blkbits
);
692 * Put cur_page under IO. The section of cur_page which is described by
693 * cur_page_offset,cur_page_len is put into a BIO. The section of cur_page
694 * starts on-disk at cur_page_block.
696 * We take a ref against the page here (on behalf of its presence in the bio).
698 * The caller of this function is responsible for removing cur_page from the
699 * dio, and for dropping the refcount which came from that presence.
701 static inline int dio_send_cur_page(struct dio
*dio
, struct dio_submit
*sdio
,
702 struct buffer_head
*map_bh
)
707 loff_t cur_offset
= sdio
->cur_page_fs_offset
;
708 loff_t bio_next_offset
= sdio
->logical_offset_in_bio
+
709 sdio
->bio
->bi_iter
.bi_size
;
712 * See whether this new request is contiguous with the old.
714 * Btrfs cannot handle having logically non-contiguous requests
715 * submitted. For example if you have
717 * Logical: [0-4095][HOLE][8192-12287]
718 * Physical: [0-4095] [4096-8191]
720 * We cannot submit those pages together as one BIO. So if our
721 * current logical offset in the file does not equal what would
722 * be the next logical offset in the bio, submit the bio we
725 if (sdio
->final_block_in_bio
!= sdio
->cur_page_block
||
726 cur_offset
!= bio_next_offset
)
727 dio_bio_submit(dio
, sdio
);
730 if (sdio
->bio
== NULL
) {
731 ret
= dio_new_bio(dio
, sdio
, sdio
->cur_page_block
, map_bh
);
736 if (dio_bio_add_page(sdio
) != 0) {
737 dio_bio_submit(dio
, sdio
);
738 ret
= dio_new_bio(dio
, sdio
, sdio
->cur_page_block
, map_bh
);
740 ret
= dio_bio_add_page(sdio
);
749 * An autonomous function to put a chunk of a page under deferred IO.
751 * The caller doesn't actually know (or care) whether this piece of page is in
752 * a BIO, or is under IO or whatever. We just take care of all possible
753 * situations here. The separation between the logic of do_direct_IO() and
754 * that of submit_page_section() is important for clarity. Please don't break.
756 * The chunk of page starts on-disk at blocknr.
758 * We perform deferred IO, by recording the last-submitted page inside our
759 * private part of the dio structure. If possible, we just expand the IO
760 * across that page here.
762 * If that doesn't work out then we put the old page into the bio and add this
763 * page to the dio instead.
766 submit_page_section(struct dio
*dio
, struct dio_submit
*sdio
, struct page
*page
,
767 unsigned offset
, unsigned len
, sector_t blocknr
,
768 struct buffer_head
*map_bh
)
772 if (dio
->rw
& WRITE
) {
774 * Read accounting is performed in submit_bio()
776 task_io_account_write(len
);
780 * Can we just grow the current page's presence in the dio?
782 if (sdio
->cur_page
== page
&&
783 sdio
->cur_page_offset
+ sdio
->cur_page_len
== offset
&&
784 sdio
->cur_page_block
+
785 (sdio
->cur_page_len
>> sdio
->blkbits
) == blocknr
) {
786 sdio
->cur_page_len
+= len
;
791 * If there's a deferred page already there then send it.
793 if (sdio
->cur_page
) {
794 ret
= dio_send_cur_page(dio
, sdio
, map_bh
);
795 page_cache_release(sdio
->cur_page
);
796 sdio
->cur_page
= NULL
;
801 page_cache_get(page
); /* It is in dio */
802 sdio
->cur_page
= page
;
803 sdio
->cur_page_offset
= offset
;
804 sdio
->cur_page_len
= len
;
805 sdio
->cur_page_block
= blocknr
;
806 sdio
->cur_page_fs_offset
= sdio
->block_in_file
<< sdio
->blkbits
;
809 * If sdio->boundary then we want to schedule the IO now to
810 * avoid metadata seeks.
812 if (sdio
->boundary
) {
813 ret
= dio_send_cur_page(dio
, sdio
, map_bh
);
814 dio_bio_submit(dio
, sdio
);
815 page_cache_release(sdio
->cur_page
);
816 sdio
->cur_page
= NULL
;
822 * Clean any dirty buffers in the blockdev mapping which alias newly-created
823 * file blocks. Only called for S_ISREG files - blockdevs do not set
826 static void clean_blockdev_aliases(struct dio
*dio
, struct buffer_head
*map_bh
)
831 nblocks
= map_bh
->b_size
>> dio
->inode
->i_blkbits
;
833 for (i
= 0; i
< nblocks
; i
++) {
834 unmap_underlying_metadata(map_bh
->b_bdev
,
835 map_bh
->b_blocknr
+ i
);
840 * If we are not writing the entire block and get_block() allocated
841 * the block for us, we need to fill-in the unused portion of the
842 * block with zeros. This happens only if user-buffer, fileoffset or
843 * io length is not filesystem block-size multiple.
845 * `end' is zero if we're doing the start of the IO, 1 at the end of the
848 static inline void dio_zero_block(struct dio
*dio
, struct dio_submit
*sdio
,
849 int end
, struct buffer_head
*map_bh
)
851 unsigned dio_blocks_per_fs_block
;
852 unsigned this_chunk_blocks
; /* In dio_blocks */
853 unsigned this_chunk_bytes
;
856 sdio
->start_zero_done
= 1;
857 if (!sdio
->blkfactor
|| !buffer_new(map_bh
))
860 dio_blocks_per_fs_block
= 1 << sdio
->blkfactor
;
861 this_chunk_blocks
= sdio
->block_in_file
& (dio_blocks_per_fs_block
- 1);
863 if (!this_chunk_blocks
)
867 * We need to zero out part of an fs block. It is either at the
868 * beginning or the end of the fs block.
871 this_chunk_blocks
= dio_blocks_per_fs_block
- this_chunk_blocks
;
873 this_chunk_bytes
= this_chunk_blocks
<< sdio
->blkbits
;
876 if (submit_page_section(dio
, sdio
, page
, 0, this_chunk_bytes
,
877 sdio
->next_block_for_io
, map_bh
))
880 sdio
->next_block_for_io
+= this_chunk_blocks
;
884 * Walk the user pages, and the file, mapping blocks to disk and generating
885 * a sequence of (page,offset,len,block) mappings. These mappings are injected
886 * into submit_page_section(), which takes care of the next stage of submission
888 * Direct IO against a blockdev is different from a file. Because we can
889 * happily perform page-sized but 512-byte aligned IOs. It is important that
890 * blockdev IO be able to have fine alignment and large sizes.
892 * So what we do is to permit the ->get_block function to populate bh.b_size
893 * with the size of IO which is permitted at this offset and this i_blkbits.
895 * For best results, the blockdev should be set up with 512-byte i_blkbits and
896 * it should set b_size to PAGE_SIZE or more inside get_block(). This gives
897 * fine alignment but still allows this function to work in PAGE_SIZE units.
899 static int do_direct_IO(struct dio
*dio
, struct dio_submit
*sdio
,
900 struct buffer_head
*map_bh
)
902 const unsigned blkbits
= sdio
->blkbits
;
905 while (sdio
->block_in_file
< sdio
->final_block_in_request
) {
909 page
= dio_get_page(dio
, sdio
);
914 from
= sdio
->head
? 0 : sdio
->from
;
915 to
= (sdio
->head
== sdio
->tail
- 1) ? sdio
->to
: PAGE_SIZE
;
919 unsigned this_chunk_bytes
; /* # of bytes mapped */
920 unsigned this_chunk_blocks
; /* # of blocks */
923 if (sdio
->blocks_available
== 0) {
925 * Need to go and map some more disk
927 unsigned long blkmask
;
928 unsigned long dio_remainder
;
930 ret
= get_more_blocks(dio
, sdio
, map_bh
);
932 page_cache_release(page
);
935 if (!buffer_mapped(map_bh
))
938 sdio
->blocks_available
=
939 map_bh
->b_size
>> sdio
->blkbits
;
940 sdio
->next_block_for_io
=
941 map_bh
->b_blocknr
<< sdio
->blkfactor
;
942 if (buffer_new(map_bh
))
943 clean_blockdev_aliases(dio
, map_bh
);
945 if (!sdio
->blkfactor
)
948 blkmask
= (1 << sdio
->blkfactor
) - 1;
949 dio_remainder
= (sdio
->block_in_file
& blkmask
);
952 * If we are at the start of IO and that IO
953 * starts partway into a fs-block,
954 * dio_remainder will be non-zero. If the IO
955 * is a read then we can simply advance the IO
956 * cursor to the first block which is to be
957 * read. But if the IO is a write and the
958 * block was newly allocated we cannot do that;
959 * the start of the fs block must be zeroed out
962 if (!buffer_new(map_bh
))
963 sdio
->next_block_for_io
+= dio_remainder
;
964 sdio
->blocks_available
-= dio_remainder
;
968 if (!buffer_mapped(map_bh
)) {
969 loff_t i_size_aligned
;
971 /* AKPM: eargh, -ENOTBLK is a hack */
972 if (dio
->rw
& WRITE
) {
973 page_cache_release(page
);
978 * Be sure to account for a partial block as the
979 * last block in the file
981 i_size_aligned
= ALIGN(i_size_read(dio
->inode
),
983 if (sdio
->block_in_file
>=
984 i_size_aligned
>> blkbits
) {
986 page_cache_release(page
);
989 zero_user(page
, from
, 1 << blkbits
);
990 sdio
->block_in_file
++;
991 from
+= 1 << blkbits
;
992 dio
->result
+= 1 << blkbits
;
997 * If we're performing IO which has an alignment which
998 * is finer than the underlying fs, go check to see if
999 * we must zero out the start of this block.
1001 if (unlikely(sdio
->blkfactor
&& !sdio
->start_zero_done
))
1002 dio_zero_block(dio
, sdio
, 0, map_bh
);
1005 * Work out, in this_chunk_blocks, how much disk we
1006 * can add to this page
1008 this_chunk_blocks
= sdio
->blocks_available
;
1009 u
= (to
- from
) >> blkbits
;
1010 if (this_chunk_blocks
> u
)
1011 this_chunk_blocks
= u
;
1012 u
= sdio
->final_block_in_request
- sdio
->block_in_file
;
1013 if (this_chunk_blocks
> u
)
1014 this_chunk_blocks
= u
;
1015 this_chunk_bytes
= this_chunk_blocks
<< blkbits
;
1016 BUG_ON(this_chunk_bytes
== 0);
1018 if (this_chunk_blocks
== sdio
->blocks_available
)
1019 sdio
->boundary
= buffer_boundary(map_bh
);
1020 ret
= submit_page_section(dio
, sdio
, page
,
1023 sdio
->next_block_for_io
,
1026 page_cache_release(page
);
1029 sdio
->next_block_for_io
+= this_chunk_blocks
;
1031 sdio
->block_in_file
+= this_chunk_blocks
;
1032 from
+= this_chunk_bytes
;
1033 dio
->result
+= this_chunk_bytes
;
1034 sdio
->blocks_available
-= this_chunk_blocks
;
1036 BUG_ON(sdio
->block_in_file
> sdio
->final_block_in_request
);
1037 if (sdio
->block_in_file
== sdio
->final_block_in_request
)
1041 /* Drop the ref which was taken in get_user_pages() */
1042 page_cache_release(page
);
1048 static inline int drop_refcount(struct dio
*dio
)
1051 unsigned long flags
;
1054 * Sync will always be dropping the final ref and completing the
1055 * operation. AIO can if it was a broken operation described above or
1056 * in fact if all the bios race to complete before we get here. In
1057 * that case dio_complete() translates the EIOCBQUEUED into the proper
1058 * return code that the caller will hand to ->complete().
1060 * This is managed by the bio_lock instead of being an atomic_t so that
1061 * completion paths can drop their ref and use the remaining count to
1062 * decide to wake the submission path atomically.
1064 spin_lock_irqsave(&dio
->bio_lock
, flags
);
1065 ret2
= --dio
->refcount
;
1066 spin_unlock_irqrestore(&dio
->bio_lock
, flags
);
1071 * This is a library function for use by filesystem drivers.
1073 * The locking rules are governed by the flags parameter:
1074 * - if the flags value contains DIO_LOCKING we use a fancy locking
1075 * scheme for dumb filesystems.
1076 * For writes this function is called under i_mutex and returns with
1077 * i_mutex held, for reads, i_mutex is not held on entry, but it is
1078 * taken and dropped again before returning.
1079 * - if the flags value does NOT contain DIO_LOCKING we don't use any
1080 * internal locking but rather rely on the filesystem to synchronize
1081 * direct I/O reads/writes versus each other and truncate.
1083 * To help with locking against truncate we incremented the i_dio_count
1084 * counter before starting direct I/O, and decrement it once we are done.
1085 * Truncate can wait for it to reach zero to provide exclusion. It is
1086 * expected that filesystem provide exclusion between new direct I/O
1087 * and truncates. For DIO_LOCKING filesystems this is done by i_mutex,
1088 * but other filesystems need to take care of this on their own.
1090 * NOTE: if you pass "sdio" to anything by pointer make sure that function
1091 * is always inlined. Otherwise gcc is unable to split the structure into
1092 * individual fields and will generate much worse code. This is important
1093 * for the whole file.
1095 static inline ssize_t
1096 do_blockdev_direct_IO(struct kiocb
*iocb
, struct inode
*inode
,
1097 struct block_device
*bdev
, struct iov_iter
*iter
,
1098 loff_t offset
, get_block_t get_block
, dio_iodone_t end_io
,
1099 dio_submit_t submit_io
, int flags
)
1101 unsigned i_blkbits
= ACCESS_ONCE(inode
->i_blkbits
);
1102 unsigned blkbits
= i_blkbits
;
1103 unsigned blocksize_mask
= (1 << blkbits
) - 1;
1104 ssize_t retval
= -EINVAL
;
1105 size_t count
= iov_iter_count(iter
);
1106 loff_t end
= offset
+ count
;
1108 struct dio_submit sdio
= { 0, };
1109 struct buffer_head map_bh
= { 0, };
1110 struct blk_plug plug
;
1111 unsigned long align
= offset
| iov_iter_alignment(iter
);
1114 * Avoid references to bdev if not absolutely needed to give
1115 * the early prefetch in the caller enough time.
1118 if (align
& blocksize_mask
) {
1120 blkbits
= blksize_bits(bdev_logical_block_size(bdev
));
1121 blocksize_mask
= (1 << blkbits
) - 1;
1122 if (align
& blocksize_mask
)
1126 /* watch out for a 0 len io from a tricksy fs */
1127 if (iov_iter_rw(iter
) == READ
&& !iov_iter_count(iter
))
1130 dio
= kmem_cache_alloc(dio_cache
, GFP_KERNEL
);
1135 * Believe it or not, zeroing out the page array caused a .5%
1136 * performance regression in a database benchmark. So, we take
1137 * care to only zero out what's needed.
1139 memset(dio
, 0, offsetof(struct dio
, pages
));
1142 if (dio
->flags
& DIO_LOCKING
) {
1143 if (iov_iter_rw(iter
) == READ
) {
1144 struct address_space
*mapping
=
1145 iocb
->ki_filp
->f_mapping
;
1147 /* will be released by direct_io_worker */
1148 mutex_lock(&inode
->i_mutex
);
1150 retval
= filemap_write_and_wait_range(mapping
, offset
,
1153 mutex_unlock(&inode
->i_mutex
);
1154 kmem_cache_free(dio_cache
, dio
);
1161 * For file extending writes updating i_size before data writeouts
1162 * complete can expose uninitialized blocks in dumb filesystems.
1163 * In that case we need to wait for I/O completion even if asked
1164 * for an asynchronous write.
1166 if (is_sync_kiocb(iocb
))
1167 dio
->is_async
= false;
1168 else if (!(dio
->flags
& DIO_ASYNC_EXTEND
) &&
1169 iov_iter_rw(iter
) == WRITE
&& end
> i_size_read(inode
))
1170 dio
->is_async
= false;
1172 dio
->is_async
= true;
1175 dio
->rw
= iov_iter_rw(iter
) == WRITE
? WRITE_ODIRECT
: READ
;
1178 * For AIO O_(D)SYNC writes we need to defer completions to a workqueue
1179 * so that we can call ->fsync.
1181 if (dio
->is_async
&& iov_iter_rw(iter
) == WRITE
&&
1182 ((iocb
->ki_filp
->f_flags
& O_DSYNC
) ||
1183 IS_SYNC(iocb
->ki_filp
->f_mapping
->host
))) {
1184 retval
= dio_set_defer_completion(dio
);
1187 * We grab i_mutex only for reads so we don't have
1188 * to release it here
1190 kmem_cache_free(dio_cache
, dio
);
1196 * Will be decremented at I/O completion time.
1198 atomic_inc(&inode
->i_dio_count
);
1201 sdio
.blkbits
= blkbits
;
1202 sdio
.blkfactor
= i_blkbits
- blkbits
;
1203 sdio
.block_in_file
= offset
>> blkbits
;
1205 sdio
.get_block
= get_block
;
1206 dio
->end_io
= end_io
;
1207 sdio
.submit_io
= submit_io
;
1208 sdio
.final_block_in_bio
= -1;
1209 sdio
.next_block_for_io
= -1;
1212 dio
->i_size
= i_size_read(inode
);
1214 spin_lock_init(&dio
->bio_lock
);
1218 sdio
.final_block_in_request
=
1219 (offset
+ iov_iter_count(iter
)) >> blkbits
;
1222 * In case of non-aligned buffers, we may need 2 more
1223 * pages since we need to zero out first and last block.
1225 if (unlikely(sdio
.blkfactor
))
1226 sdio
.pages_in_io
= 2;
1228 sdio
.pages_in_io
+= iov_iter_npages(iter
, INT_MAX
);
1230 blk_start_plug(&plug
);
1232 retval
= do_direct_IO(dio
, &sdio
, &map_bh
);
1234 dio_cleanup(dio
, &sdio
);
1236 if (retval
== -ENOTBLK
) {
1238 * The remaining part of the request will be
1239 * be handled by buffered I/O when we return
1244 * There may be some unwritten disk at the end of a part-written
1245 * fs-block-sized block. Go zero that now.
1247 dio_zero_block(dio
, &sdio
, 1, &map_bh
);
1249 if (sdio
.cur_page
) {
1252 ret2
= dio_send_cur_page(dio
, &sdio
, &map_bh
);
1255 page_cache_release(sdio
.cur_page
);
1256 sdio
.cur_page
= NULL
;
1259 dio_bio_submit(dio
, &sdio
);
1261 blk_finish_plug(&plug
);
1264 * It is possible that, we return short IO due to end of file.
1265 * In that case, we need to release all the pages we got hold on.
1267 dio_cleanup(dio
, &sdio
);
1270 * All block lookups have been performed. For READ requests
1271 * we can let i_mutex go now that its achieved its purpose
1272 * of protecting us from looking up uninitialized blocks.
1274 if (iov_iter_rw(iter
) == READ
&& (dio
->flags
& DIO_LOCKING
))
1275 mutex_unlock(&dio
->inode
->i_mutex
);
1278 * The only time we want to leave bios in flight is when a successful
1279 * partial aio read or full aio write have been setup. In that case
1280 * bio completion will call aio_complete. The only time it's safe to
1281 * call aio_complete is when we return -EIOCBQUEUED, so we key on that.
1282 * This had *better* be the only place that raises -EIOCBQUEUED.
1284 BUG_ON(retval
== -EIOCBQUEUED
);
1285 if (dio
->is_async
&& retval
== 0 && dio
->result
&&
1286 (iov_iter_rw(iter
) == READ
|| dio
->result
== count
))
1287 retval
= -EIOCBQUEUED
;
1289 dio_await_completion(dio
);
1291 if (drop_refcount(dio
) == 0) {
1292 retval
= dio_complete(dio
, offset
, retval
, false);
1294 BUG_ON(retval
!= -EIOCBQUEUED
);
1300 ssize_t
__blockdev_direct_IO(struct kiocb
*iocb
, struct inode
*inode
,
1301 struct block_device
*bdev
, struct iov_iter
*iter
,
1302 loff_t offset
, get_block_t get_block
,
1303 dio_iodone_t end_io
, dio_submit_t submit_io
,
1307 * The block device state is needed in the end to finally
1308 * submit everything. Since it's likely to be cache cold
1309 * prefetch it here as first thing to hide some of the
1312 * Attempt to prefetch the pieces we likely need later.
1314 prefetch(&bdev
->bd_disk
->part_tbl
);
1315 prefetch(bdev
->bd_queue
);
1316 prefetch((char *)bdev
->bd_queue
+ SMP_CACHE_BYTES
);
1318 return do_blockdev_direct_IO(iocb
, inode
, bdev
, iter
, offset
, get_block
,
1319 end_io
, submit_io
, flags
);
1322 EXPORT_SYMBOL(__blockdev_direct_IO
);
1324 static __init
int dio_init(void)
1326 dio_cache
= KMEM_CACHE(dio
, SLAB_PANIC
);
1329 module_init(dio_init
)