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>
40 #include <linux/aio.h>
43 * How many user pages to map in one call to get_user_pages(). This determines
44 * the size of a structure in the slab cache
49 * This code generally works in units of "dio_blocks". A dio_block is
50 * somewhere between the hard sector size and the filesystem block size. it
51 * is determined on a per-invocation basis. When talking to the filesystem
52 * we need to convert dio_blocks to fs_blocks by scaling the dio_block quantity
53 * down by dio->blkfactor. Similarly, fs-blocksize quantities are converted
54 * to bio_block quantities by shifting left by blkfactor.
56 * If blkfactor is zero then the user's request was aligned to the filesystem's
60 /* dio_state only used in the submission path */
63 struct bio
*bio
; /* bio under assembly */
64 unsigned blkbits
; /* doesn't change */
65 unsigned blkfactor
; /* When we're using an alignment which
66 is finer than the filesystem's soft
67 blocksize, this specifies how much
68 finer. blkfactor=2 means 1/4-block
69 alignment. Does not change */
70 unsigned start_zero_done
; /* flag: sub-blocksize zeroing has
71 been performed at the start of a
73 int pages_in_io
; /* approximate total IO pages */
74 size_t size
; /* total request size (doesn't change)*/
75 sector_t block_in_file
; /* Current offset into the underlying
76 file in dio_block units. */
77 unsigned blocks_available
; /* At block_in_file. changes */
78 int reap_counter
; /* rate limit reaping */
79 sector_t final_block_in_request
;/* doesn't change */
80 int boundary
; /* prev block is at a boundary */
81 get_block_t
*get_block
; /* block mapping function */
82 dio_submit_t
*submit_io
; /* IO submition function */
84 loff_t logical_offset_in_bio
; /* current first logical block in bio */
85 sector_t final_block_in_bio
; /* current final block in bio + 1 */
86 sector_t next_block_for_io
; /* next block to be put under IO,
87 in dio_blocks units */
90 * Deferred addition of a page to the dio. These variables are
91 * private to dio_send_cur_page(), submit_page_section() and
94 struct page
*cur_page
; /* The page */
95 unsigned cur_page_offset
; /* Offset into it, in bytes */
96 unsigned cur_page_len
; /* Nr of bytes at cur_page_offset */
97 sector_t cur_page_block
; /* Where it starts */
98 loff_t cur_page_fs_offset
; /* Offset in file */
100 struct iov_iter
*iter
;
102 * Page queue. These variables belong to dio_refill_pages() and
105 unsigned head
; /* next page to process */
106 unsigned tail
; /* last valid page + 1 */
110 /* dio_state communicated between submission path and end_io */
112 int flags
; /* doesn't change */
115 loff_t i_size
; /* i_size when submitted */
116 dio_iodone_t
*end_io
; /* IO completion function */
118 void *private; /* copy from map_bh.b_private */
120 /* BIO completion state */
121 spinlock_t bio_lock
; /* protects BIO fields below */
122 int page_errors
; /* errno from get_user_pages() */
123 int is_async
; /* is IO async ? */
124 bool defer_completion
; /* defer AIO completion to workqueue? */
125 int io_error
; /* IO error in completion path */
126 unsigned long refcount
; /* direct_io_worker() and bios */
127 struct bio
*bio_list
; /* singly linked via bi_private */
128 struct task_struct
*waiter
; /* waiting task (NULL if none) */
130 /* AIO related stuff */
131 struct kiocb
*iocb
; /* kiocb */
132 ssize_t result
; /* IO result */
135 * pages[] (and any fields placed after it) are not zeroed out at
136 * allocation time. Don't add new fields after pages[] unless you
137 * wish that they not be zeroed.
140 struct page
*pages
[DIO_PAGES
]; /* page buffer */
141 struct work_struct complete_work
;/* deferred AIO completion */
143 } ____cacheline_aligned_in_smp
;
145 static struct kmem_cache
*dio_cache __read_mostly
;
148 * How many pages are in the queue?
150 static inline unsigned dio_pages_present(struct dio_submit
*sdio
)
152 return sdio
->tail
- sdio
->head
;
156 * Go grab and pin some userspace pages. Typically we'll get 64 at a time.
158 static inline int dio_refill_pages(struct dio
*dio
, struct dio_submit
*sdio
)
162 ret
= iov_iter_get_pages(sdio
->iter
, dio
->pages
, DIO_PAGES
* PAGE_SIZE
,
165 if (ret
< 0 && sdio
->blocks_available
&& (dio
->rw
& WRITE
)) {
166 struct page
*page
= ZERO_PAGE(0);
168 * A memory fault, but the filesystem has some outstanding
169 * mapped blocks. We need to use those blocks up to avoid
170 * leaking stale data in the file.
172 if (dio
->page_errors
== 0)
173 dio
->page_errors
= ret
;
174 page_cache_get(page
);
175 dio
->pages
[0] = page
;
179 sdio
->to
= PAGE_SIZE
;
184 iov_iter_advance(sdio
->iter
, ret
);
187 sdio
->tail
= (ret
+ PAGE_SIZE
- 1) / PAGE_SIZE
;
188 sdio
->to
= ((ret
- 1) & (PAGE_SIZE
- 1)) + 1;
195 * Get another userspace page. Returns an ERR_PTR on error. Pages are
196 * buffered inside the dio so that we can call get_user_pages() against a
197 * decent number of pages, less frequently. To provide nicer use of the
200 static inline struct page
*dio_get_page(struct dio
*dio
,
201 struct dio_submit
*sdio
, size_t *from
, size_t *to
)
204 if (dio_pages_present(sdio
) == 0) {
207 ret
= dio_refill_pages(dio
, sdio
);
210 BUG_ON(dio_pages_present(sdio
) == 0);
213 *from
= n
? 0 : sdio
->from
;
214 *to
= (n
== sdio
->tail
- 1) ? sdio
->to
: PAGE_SIZE
;
215 return dio
->pages
[n
];
219 * dio_complete() - called when all DIO BIO I/O has been completed
220 * @offset: the byte offset in the file of the completed operation
222 * This drops i_dio_count, lets interested parties know that a DIO operation
223 * has completed, and calculates the resulting return code for the operation.
225 * It lets the filesystem know if it registered an interest earlier via
226 * get_block. Pass the private field of the map buffer_head so that
227 * filesystems can use it to hold additional state between get_block calls and
230 static ssize_t
dio_complete(struct dio
*dio
, loff_t offset
, ssize_t ret
,
233 ssize_t transferred
= 0;
236 * AIO submission can race with bio completion to get here while
237 * expecting to have the last io completed by bio completion.
238 * In that case -EIOCBQUEUED is in fact not an error we want
239 * to preserve through this call.
241 if (ret
== -EIOCBQUEUED
)
245 transferred
= dio
->result
;
247 /* Check for short read case */
248 if ((dio
->rw
== READ
) && ((offset
+ transferred
) > dio
->i_size
))
249 transferred
= dio
->i_size
- offset
;
253 ret
= dio
->page_errors
;
259 if (dio
->end_io
&& dio
->result
)
260 dio
->end_io(dio
->iocb
, offset
, transferred
, dio
->private);
262 inode_dio_done(dio
->inode
);
264 if (dio
->rw
& WRITE
) {
267 err
= generic_write_sync(dio
->iocb
->ki_filp
, offset
,
269 if (err
< 0 && ret
> 0)
273 aio_complete(dio
->iocb
, ret
, 0);
276 kmem_cache_free(dio_cache
, dio
);
280 static void dio_aio_complete_work(struct work_struct
*work
)
282 struct dio
*dio
= container_of(work
, struct dio
, complete_work
);
284 dio_complete(dio
, dio
->iocb
->ki_pos
, 0, true);
287 static int dio_bio_complete(struct dio
*dio
, struct bio
*bio
);
290 * Asynchronous IO callback.
292 static void dio_bio_end_aio(struct bio
*bio
, int error
)
294 struct dio
*dio
= bio
->bi_private
;
295 unsigned long remaining
;
298 /* cleanup the bio */
299 dio_bio_complete(dio
, bio
);
301 spin_lock_irqsave(&dio
->bio_lock
, flags
);
302 remaining
= --dio
->refcount
;
303 if (remaining
== 1 && dio
->waiter
)
304 wake_up_process(dio
->waiter
);
305 spin_unlock_irqrestore(&dio
->bio_lock
, flags
);
307 if (remaining
== 0) {
308 if (dio
->result
&& dio
->defer_completion
) {
309 INIT_WORK(&dio
->complete_work
, dio_aio_complete_work
);
310 queue_work(dio
->inode
->i_sb
->s_dio_done_wq
,
311 &dio
->complete_work
);
313 dio_complete(dio
, dio
->iocb
->ki_pos
, 0, true);
319 * The BIO completion handler simply queues the BIO up for the process-context
322 * During I/O bi_private points at the dio. After I/O, bi_private is used to
323 * implement a singly-linked list of completed BIOs, at dio->bio_list.
325 static void dio_bio_end_io(struct bio
*bio
, int error
)
327 struct dio
*dio
= bio
->bi_private
;
330 spin_lock_irqsave(&dio
->bio_lock
, flags
);
331 bio
->bi_private
= dio
->bio_list
;
333 if (--dio
->refcount
== 1 && dio
->waiter
)
334 wake_up_process(dio
->waiter
);
335 spin_unlock_irqrestore(&dio
->bio_lock
, flags
);
339 * dio_end_io - handle the end io action for the given bio
340 * @bio: The direct io bio thats being completed
341 * @error: Error if there was one
343 * This is meant to be called by any filesystem that uses their own dio_submit_t
344 * so that the DIO specific endio actions are dealt with after the filesystem
345 * has done it's completion work.
347 void dio_end_io(struct bio
*bio
, int error
)
349 struct dio
*dio
= bio
->bi_private
;
352 dio_bio_end_aio(bio
, error
);
354 dio_bio_end_io(bio
, error
);
356 EXPORT_SYMBOL_GPL(dio_end_io
);
359 dio_bio_alloc(struct dio
*dio
, struct dio_submit
*sdio
,
360 struct block_device
*bdev
,
361 sector_t first_sector
, int nr_vecs
)
366 * bio_alloc() is guaranteed to return a bio when called with
367 * __GFP_WAIT and we request a valid number of vectors.
369 bio
= bio_alloc(GFP_KERNEL
, nr_vecs
);
372 bio
->bi_iter
.bi_sector
= first_sector
;
374 bio
->bi_end_io
= dio_bio_end_aio
;
376 bio
->bi_end_io
= dio_bio_end_io
;
379 sdio
->logical_offset_in_bio
= sdio
->cur_page_fs_offset
;
383 * In the AIO read case we speculatively dirty the pages before starting IO.
384 * During IO completion, any of these pages which happen to have been written
385 * back will be redirtied by bio_check_pages_dirty().
387 * bios hold a dio reference between submit_bio and ->end_io.
389 static inline void dio_bio_submit(struct dio
*dio
, struct dio_submit
*sdio
)
391 struct bio
*bio
= sdio
->bio
;
394 bio
->bi_private
= dio
;
396 spin_lock_irqsave(&dio
->bio_lock
, flags
);
398 spin_unlock_irqrestore(&dio
->bio_lock
, flags
);
400 if (dio
->is_async
&& dio
->rw
== READ
)
401 bio_set_pages_dirty(bio
);
404 sdio
->submit_io(dio
->rw
, bio
, dio
->inode
,
405 sdio
->logical_offset_in_bio
);
407 submit_bio(dio
->rw
, bio
);
411 sdio
->logical_offset_in_bio
= 0;
415 * Release any resources in case of a failure
417 static inline void dio_cleanup(struct dio
*dio
, struct dio_submit
*sdio
)
419 while (sdio
->head
< sdio
->tail
)
420 page_cache_release(dio
->pages
[sdio
->head
++]);
424 * Wait for the next BIO to complete. Remove it and return it. NULL is
425 * returned once all BIOs have been completed. This must only be called once
426 * all bios have been issued so that dio->refcount can only decrease. This
427 * requires that that the caller hold a reference on the dio.
429 static struct bio
*dio_await_one(struct dio
*dio
)
432 struct bio
*bio
= NULL
;
434 spin_lock_irqsave(&dio
->bio_lock
, flags
);
437 * Wait as long as the list is empty and there are bios in flight. bio
438 * completion drops the count, maybe adds to the list, and wakes while
439 * holding the bio_lock so we don't need set_current_state()'s barrier
440 * and can call it after testing our condition.
442 while (dio
->refcount
> 1 && dio
->bio_list
== NULL
) {
443 __set_current_state(TASK_UNINTERRUPTIBLE
);
444 dio
->waiter
= current
;
445 spin_unlock_irqrestore(&dio
->bio_lock
, flags
);
447 /* wake up sets us TASK_RUNNING */
448 spin_lock_irqsave(&dio
->bio_lock
, flags
);
453 dio
->bio_list
= bio
->bi_private
;
455 spin_unlock_irqrestore(&dio
->bio_lock
, flags
);
460 * Process one completed BIO. No locks are held.
462 static int dio_bio_complete(struct dio
*dio
, struct bio
*bio
)
464 const int uptodate
= test_bit(BIO_UPTODATE
, &bio
->bi_flags
);
465 struct bio_vec
*bvec
;
469 dio
->io_error
= -EIO
;
471 if (dio
->is_async
&& dio
->rw
== READ
) {
472 bio_check_pages_dirty(bio
); /* transfers ownership */
474 bio_for_each_segment_all(bvec
, bio
, i
) {
475 struct page
*page
= bvec
->bv_page
;
477 if (dio
->rw
== READ
&& !PageCompound(page
))
478 set_page_dirty_lock(page
);
479 page_cache_release(page
);
483 return uptodate
? 0 : -EIO
;
487 * Wait on and process all in-flight BIOs. This must only be called once
488 * all bios have been issued so that the refcount can only decrease.
489 * This just waits for all bios to make it through dio_bio_complete. IO
490 * errors are propagated through dio->io_error and should be propagated via
493 static void dio_await_completion(struct dio
*dio
)
497 bio
= dio_await_one(dio
);
499 dio_bio_complete(dio
, bio
);
504 * A really large O_DIRECT read or write can generate a lot of BIOs. So
505 * to keep the memory consumption sane we periodically reap any completed BIOs
506 * during the BIO generation phase.
508 * This also helps to limit the peak amount of pinned userspace memory.
510 static inline int dio_bio_reap(struct dio
*dio
, struct dio_submit
*sdio
)
514 if (sdio
->reap_counter
++ >= 64) {
515 while (dio
->bio_list
) {
520 spin_lock_irqsave(&dio
->bio_lock
, flags
);
522 dio
->bio_list
= bio
->bi_private
;
523 spin_unlock_irqrestore(&dio
->bio_lock
, flags
);
524 ret2
= dio_bio_complete(dio
, bio
);
528 sdio
->reap_counter
= 0;
534 * Create workqueue for deferred direct IO completions. We allocate the
535 * workqueue when it's first needed. This avoids creating workqueue for
536 * filesystems that don't need it and also allows us to create the workqueue
537 * late enough so the we can include s_id in the name of the workqueue.
539 static int sb_init_dio_done_wq(struct super_block
*sb
)
541 struct workqueue_struct
*old
;
542 struct workqueue_struct
*wq
= alloc_workqueue("dio/%s",
548 * This has to be atomic as more DIOs can race to create the workqueue
550 old
= cmpxchg(&sb
->s_dio_done_wq
, NULL
, wq
);
551 /* Someone created workqueue before us? Free ours... */
553 destroy_workqueue(wq
);
557 static int dio_set_defer_completion(struct dio
*dio
)
559 struct super_block
*sb
= dio
->inode
->i_sb
;
561 if (dio
->defer_completion
)
563 dio
->defer_completion
= true;
564 if (!sb
->s_dio_done_wq
)
565 return sb_init_dio_done_wq(sb
);
570 * Call into the fs to map some more disk blocks. We record the current number
571 * of available blocks at sdio->blocks_available. These are in units of the
572 * fs blocksize, (1 << inode->i_blkbits).
574 * The fs is allowed to map lots of blocks at once. If it wants to do that,
575 * it uses the passed inode-relative block number as the file offset, as usual.
577 * get_block() is passed the number of i_blkbits-sized blocks which direct_io
578 * has remaining to do. The fs should not map more than this number of blocks.
580 * If the fs has mapped a lot of blocks, it should populate bh->b_size to
581 * indicate how much contiguous disk space has been made available at
584 * If *any* of the mapped blocks are new, then the fs must set buffer_new().
585 * This isn't very efficient...
587 * In the case of filesystem holes: the fs may return an arbitrarily-large
588 * hole by returning an appropriate value in b_size and by clearing
589 * buffer_mapped(). However the direct-io code will only process holes one
590 * block at a time - it will repeatedly call get_block() as it walks the hole.
592 static int get_more_blocks(struct dio
*dio
, struct dio_submit
*sdio
,
593 struct buffer_head
*map_bh
)
596 sector_t fs_startblk
; /* Into file, in filesystem-sized blocks */
597 sector_t fs_endblk
; /* Into file, in filesystem-sized blocks */
598 unsigned long fs_count
; /* Number of filesystem-sized blocks */
600 unsigned int i_blkbits
= sdio
->blkbits
+ sdio
->blkfactor
;
603 * If there was a memory error and we've overwritten all the
604 * mapped blocks then we can now return that memory error
606 ret
= dio
->page_errors
;
608 BUG_ON(sdio
->block_in_file
>= sdio
->final_block_in_request
);
609 fs_startblk
= sdio
->block_in_file
>> sdio
->blkfactor
;
610 fs_endblk
= (sdio
->final_block_in_request
- 1) >>
612 fs_count
= fs_endblk
- fs_startblk
+ 1;
615 map_bh
->b_size
= fs_count
<< i_blkbits
;
618 * For writes inside i_size on a DIO_SKIP_HOLES filesystem we
619 * forbid block creations: only overwrites are permitted.
620 * We will return early to the caller once we see an
621 * unmapped buffer head returned, and the caller will fall
622 * back to buffered I/O.
624 * Otherwise the decision is left to the get_blocks method,
625 * which may decide to handle it or also return an unmapped
628 create
= dio
->rw
& WRITE
;
629 if (dio
->flags
& DIO_SKIP_HOLES
) {
630 if (sdio
->block_in_file
< (i_size_read(dio
->inode
) >>
635 ret
= (*sdio
->get_block
)(dio
->inode
, fs_startblk
,
638 /* Store for completion */
639 dio
->private = map_bh
->b_private
;
641 if (ret
== 0 && buffer_defer_completion(map_bh
))
642 ret
= dio_set_defer_completion(dio
);
648 * There is no bio. Make one now.
650 static inline int dio_new_bio(struct dio
*dio
, struct dio_submit
*sdio
,
651 sector_t start_sector
, struct buffer_head
*map_bh
)
656 ret
= dio_bio_reap(dio
, sdio
);
659 sector
= start_sector
<< (sdio
->blkbits
- 9);
660 nr_pages
= min(sdio
->pages_in_io
, bio_get_nr_vecs(map_bh
->b_bdev
));
661 BUG_ON(nr_pages
<= 0);
662 dio_bio_alloc(dio
, sdio
, map_bh
->b_bdev
, sector
, nr_pages
);
669 * Attempt to put the current chunk of 'cur_page' into the current BIO. If
670 * that was successful then update final_block_in_bio and take a ref against
671 * the just-added page.
673 * Return zero on success. Non-zero means the caller needs to start a new BIO.
675 static inline int dio_bio_add_page(struct dio_submit
*sdio
)
679 ret
= bio_add_page(sdio
->bio
, sdio
->cur_page
,
680 sdio
->cur_page_len
, sdio
->cur_page_offset
);
681 if (ret
== sdio
->cur_page_len
) {
683 * Decrement count only, if we are done with this page
685 if ((sdio
->cur_page_len
+ sdio
->cur_page_offset
) == PAGE_SIZE
)
687 page_cache_get(sdio
->cur_page
);
688 sdio
->final_block_in_bio
= sdio
->cur_page_block
+
689 (sdio
->cur_page_len
>> sdio
->blkbits
);
698 * Put cur_page under IO. The section of cur_page which is described by
699 * cur_page_offset,cur_page_len is put into a BIO. The section of cur_page
700 * starts on-disk at cur_page_block.
702 * We take a ref against the page here (on behalf of its presence in the bio).
704 * The caller of this function is responsible for removing cur_page from the
705 * dio, and for dropping the refcount which came from that presence.
707 static inline int dio_send_cur_page(struct dio
*dio
, struct dio_submit
*sdio
,
708 struct buffer_head
*map_bh
)
713 loff_t cur_offset
= sdio
->cur_page_fs_offset
;
714 loff_t bio_next_offset
= sdio
->logical_offset_in_bio
+
715 sdio
->bio
->bi_iter
.bi_size
;
718 * See whether this new request is contiguous with the old.
720 * Btrfs cannot handle having logically non-contiguous requests
721 * submitted. For example if you have
723 * Logical: [0-4095][HOLE][8192-12287]
724 * Physical: [0-4095] [4096-8191]
726 * We cannot submit those pages together as one BIO. So if our
727 * current logical offset in the file does not equal what would
728 * be the next logical offset in the bio, submit the bio we
731 if (sdio
->final_block_in_bio
!= sdio
->cur_page_block
||
732 cur_offset
!= bio_next_offset
)
733 dio_bio_submit(dio
, sdio
);
736 if (sdio
->bio
== NULL
) {
737 ret
= dio_new_bio(dio
, sdio
, sdio
->cur_page_block
, map_bh
);
742 if (dio_bio_add_page(sdio
) != 0) {
743 dio_bio_submit(dio
, sdio
);
744 ret
= dio_new_bio(dio
, sdio
, sdio
->cur_page_block
, map_bh
);
746 ret
= dio_bio_add_page(sdio
);
755 * An autonomous function to put a chunk of a page under deferred IO.
757 * The caller doesn't actually know (or care) whether this piece of page is in
758 * a BIO, or is under IO or whatever. We just take care of all possible
759 * situations here. The separation between the logic of do_direct_IO() and
760 * that of submit_page_section() is important for clarity. Please don't break.
762 * The chunk of page starts on-disk at blocknr.
764 * We perform deferred IO, by recording the last-submitted page inside our
765 * private part of the dio structure. If possible, we just expand the IO
766 * across that page here.
768 * If that doesn't work out then we put the old page into the bio and add this
769 * page to the dio instead.
772 submit_page_section(struct dio
*dio
, struct dio_submit
*sdio
, struct page
*page
,
773 unsigned offset
, unsigned len
, sector_t blocknr
,
774 struct buffer_head
*map_bh
)
778 if (dio
->rw
& WRITE
) {
780 * Read accounting is performed in submit_bio()
782 task_io_account_write(len
);
786 * Can we just grow the current page's presence in the dio?
788 if (sdio
->cur_page
== page
&&
789 sdio
->cur_page_offset
+ sdio
->cur_page_len
== offset
&&
790 sdio
->cur_page_block
+
791 (sdio
->cur_page_len
>> sdio
->blkbits
) == blocknr
) {
792 sdio
->cur_page_len
+= len
;
797 * If there's a deferred page already there then send it.
799 if (sdio
->cur_page
) {
800 ret
= dio_send_cur_page(dio
, sdio
, map_bh
);
801 page_cache_release(sdio
->cur_page
);
802 sdio
->cur_page
= NULL
;
807 page_cache_get(page
); /* It is in dio */
808 sdio
->cur_page
= page
;
809 sdio
->cur_page_offset
= offset
;
810 sdio
->cur_page_len
= len
;
811 sdio
->cur_page_block
= blocknr
;
812 sdio
->cur_page_fs_offset
= sdio
->block_in_file
<< sdio
->blkbits
;
815 * If sdio->boundary then we want to schedule the IO now to
816 * avoid metadata seeks.
818 if (sdio
->boundary
) {
819 ret
= dio_send_cur_page(dio
, sdio
, map_bh
);
820 dio_bio_submit(dio
, sdio
);
821 page_cache_release(sdio
->cur_page
);
822 sdio
->cur_page
= NULL
;
828 * Clean any dirty buffers in the blockdev mapping which alias newly-created
829 * file blocks. Only called for S_ISREG files - blockdevs do not set
832 static void clean_blockdev_aliases(struct dio
*dio
, struct buffer_head
*map_bh
)
837 nblocks
= map_bh
->b_size
>> dio
->inode
->i_blkbits
;
839 for (i
= 0; i
< nblocks
; i
++) {
840 unmap_underlying_metadata(map_bh
->b_bdev
,
841 map_bh
->b_blocknr
+ i
);
846 * If we are not writing the entire block and get_block() allocated
847 * the block for us, we need to fill-in the unused portion of the
848 * block with zeros. This happens only if user-buffer, fileoffset or
849 * io length is not filesystem block-size multiple.
851 * `end' is zero if we're doing the start of the IO, 1 at the end of the
854 static inline void dio_zero_block(struct dio
*dio
, struct dio_submit
*sdio
,
855 int end
, struct buffer_head
*map_bh
)
857 unsigned dio_blocks_per_fs_block
;
858 unsigned this_chunk_blocks
; /* In dio_blocks */
859 unsigned this_chunk_bytes
;
862 sdio
->start_zero_done
= 1;
863 if (!sdio
->blkfactor
|| !buffer_new(map_bh
))
866 dio_blocks_per_fs_block
= 1 << sdio
->blkfactor
;
867 this_chunk_blocks
= sdio
->block_in_file
& (dio_blocks_per_fs_block
- 1);
869 if (!this_chunk_blocks
)
873 * We need to zero out part of an fs block. It is either at the
874 * beginning or the end of the fs block.
877 this_chunk_blocks
= dio_blocks_per_fs_block
- this_chunk_blocks
;
879 this_chunk_bytes
= this_chunk_blocks
<< sdio
->blkbits
;
882 if (submit_page_section(dio
, sdio
, page
, 0, this_chunk_bytes
,
883 sdio
->next_block_for_io
, map_bh
))
886 sdio
->next_block_for_io
+= this_chunk_blocks
;
890 * Walk the user pages, and the file, mapping blocks to disk and generating
891 * a sequence of (page,offset,len,block) mappings. These mappings are injected
892 * into submit_page_section(), which takes care of the next stage of submission
894 * Direct IO against a blockdev is different from a file. Because we can
895 * happily perform page-sized but 512-byte aligned IOs. It is important that
896 * blockdev IO be able to have fine alignment and large sizes.
898 * So what we do is to permit the ->get_block function to populate bh.b_size
899 * with the size of IO which is permitted at this offset and this i_blkbits.
901 * For best results, the blockdev should be set up with 512-byte i_blkbits and
902 * it should set b_size to PAGE_SIZE or more inside get_block(). This gives
903 * fine alignment but still allows this function to work in PAGE_SIZE units.
905 static int do_direct_IO(struct dio
*dio
, struct dio_submit
*sdio
,
906 struct buffer_head
*map_bh
)
908 const unsigned blkbits
= sdio
->blkbits
;
911 while (sdio
->block_in_file
< sdio
->final_block_in_request
) {
914 page
= dio_get_page(dio
, sdio
, &from
, &to
);
921 unsigned this_chunk_bytes
; /* # of bytes mapped */
922 unsigned this_chunk_blocks
; /* # of blocks */
925 if (sdio
->blocks_available
== 0) {
927 * Need to go and map some more disk
929 unsigned long blkmask
;
930 unsigned long dio_remainder
;
932 ret
= get_more_blocks(dio
, sdio
, map_bh
);
934 page_cache_release(page
);
937 if (!buffer_mapped(map_bh
))
940 sdio
->blocks_available
=
941 map_bh
->b_size
>> sdio
->blkbits
;
942 sdio
->next_block_for_io
=
943 map_bh
->b_blocknr
<< sdio
->blkfactor
;
944 if (buffer_new(map_bh
))
945 clean_blockdev_aliases(dio
, map_bh
);
947 if (!sdio
->blkfactor
)
950 blkmask
= (1 << sdio
->blkfactor
) - 1;
951 dio_remainder
= (sdio
->block_in_file
& blkmask
);
954 * If we are at the start of IO and that IO
955 * starts partway into a fs-block,
956 * dio_remainder will be non-zero. If the IO
957 * is a read then we can simply advance the IO
958 * cursor to the first block which is to be
959 * read. But if the IO is a write and the
960 * block was newly allocated we cannot do that;
961 * the start of the fs block must be zeroed out
964 if (!buffer_new(map_bh
))
965 sdio
->next_block_for_io
+= dio_remainder
;
966 sdio
->blocks_available
-= dio_remainder
;
970 if (!buffer_mapped(map_bh
)) {
971 loff_t i_size_aligned
;
973 /* AKPM: eargh, -ENOTBLK is a hack */
974 if (dio
->rw
& WRITE
) {
975 page_cache_release(page
);
980 * Be sure to account for a partial block as the
981 * last block in the file
983 i_size_aligned
= ALIGN(i_size_read(dio
->inode
),
985 if (sdio
->block_in_file
>=
986 i_size_aligned
>> blkbits
) {
988 page_cache_release(page
);
991 zero_user(page
, from
, 1 << blkbits
);
992 sdio
->block_in_file
++;
993 from
+= 1 << blkbits
;
994 dio
->result
+= 1 << blkbits
;
999 * If we're performing IO which has an alignment which
1000 * is finer than the underlying fs, go check to see if
1001 * we must zero out the start of this block.
1003 if (unlikely(sdio
->blkfactor
&& !sdio
->start_zero_done
))
1004 dio_zero_block(dio
, sdio
, 0, map_bh
);
1007 * Work out, in this_chunk_blocks, how much disk we
1008 * can add to this page
1010 this_chunk_blocks
= sdio
->blocks_available
;
1011 u
= (to
- from
) >> blkbits
;
1012 if (this_chunk_blocks
> u
)
1013 this_chunk_blocks
= u
;
1014 u
= sdio
->final_block_in_request
- sdio
->block_in_file
;
1015 if (this_chunk_blocks
> u
)
1016 this_chunk_blocks
= u
;
1017 this_chunk_bytes
= this_chunk_blocks
<< blkbits
;
1018 BUG_ON(this_chunk_bytes
== 0);
1020 if (this_chunk_blocks
== sdio
->blocks_available
)
1021 sdio
->boundary
= buffer_boundary(map_bh
);
1022 ret
= submit_page_section(dio
, sdio
, page
,
1025 sdio
->next_block_for_io
,
1028 page_cache_release(page
);
1031 sdio
->next_block_for_io
+= this_chunk_blocks
;
1033 sdio
->block_in_file
+= this_chunk_blocks
;
1034 from
+= this_chunk_bytes
;
1035 dio
->result
+= this_chunk_bytes
;
1036 sdio
->blocks_available
-= this_chunk_blocks
;
1038 BUG_ON(sdio
->block_in_file
> sdio
->final_block_in_request
);
1039 if (sdio
->block_in_file
== sdio
->final_block_in_request
)
1043 /* Drop the ref which was taken in get_user_pages() */
1044 page_cache_release(page
);
1050 static inline int drop_refcount(struct dio
*dio
)
1053 unsigned long flags
;
1056 * Sync will always be dropping the final ref and completing the
1057 * operation. AIO can if it was a broken operation described above or
1058 * in fact if all the bios race to complete before we get here. In
1059 * that case dio_complete() translates the EIOCBQUEUED into the proper
1060 * return code that the caller will hand to aio_complete().
1062 * This is managed by the bio_lock instead of being an atomic_t so that
1063 * completion paths can drop their ref and use the remaining count to
1064 * decide to wake the submission path atomically.
1066 spin_lock_irqsave(&dio
->bio_lock
, flags
);
1067 ret2
= --dio
->refcount
;
1068 spin_unlock_irqrestore(&dio
->bio_lock
, flags
);
1073 * This is a library function for use by filesystem drivers.
1075 * The locking rules are governed by the flags parameter:
1076 * - if the flags value contains DIO_LOCKING we use a fancy locking
1077 * scheme for dumb filesystems.
1078 * For writes this function is called under i_mutex and returns with
1079 * i_mutex held, for reads, i_mutex is not held on entry, but it is
1080 * taken and dropped again before returning.
1081 * - if the flags value does NOT contain DIO_LOCKING we don't use any
1082 * internal locking but rather rely on the filesystem to synchronize
1083 * direct I/O reads/writes versus each other and truncate.
1085 * To help with locking against truncate we incremented the i_dio_count
1086 * counter before starting direct I/O, and decrement it once we are done.
1087 * Truncate can wait for it to reach zero to provide exclusion. It is
1088 * expected that filesystem provide exclusion between new direct I/O
1089 * and truncates. For DIO_LOCKING filesystems this is done by i_mutex,
1090 * but other filesystems need to take care of this on their own.
1092 * NOTE: if you pass "sdio" to anything by pointer make sure that function
1093 * is always inlined. Otherwise gcc is unable to split the structure into
1094 * individual fields and will generate much worse code. This is important
1095 * for the whole file.
1097 static inline ssize_t
1098 do_blockdev_direct_IO(int rw
, struct kiocb
*iocb
, struct inode
*inode
,
1099 struct block_device
*bdev
, struct iov_iter
*iter
, loff_t offset
,
1100 get_block_t get_block
, dio_iodone_t end_io
,
1101 dio_submit_t submit_io
, int flags
)
1103 unsigned i_blkbits
= ACCESS_ONCE(inode
->i_blkbits
);
1104 unsigned blkbits
= i_blkbits
;
1105 unsigned blocksize_mask
= (1 << blkbits
) - 1;
1106 ssize_t retval
= -EINVAL
;
1107 loff_t end
= offset
+ iov_iter_count(iter
);
1109 struct dio_submit sdio
= { 0, };
1110 struct buffer_head map_bh
= { 0, };
1111 struct blk_plug plug
;
1112 unsigned long align
= offset
| iov_iter_alignment(iter
);
1118 * Avoid references to bdev if not absolutely needed to give
1119 * the early prefetch in the caller enough time.
1122 if (align
& blocksize_mask
) {
1124 blkbits
= blksize_bits(bdev_logical_block_size(bdev
));
1125 blocksize_mask
= (1 << blkbits
) - 1;
1126 if (align
& blocksize_mask
)
1130 /* watch out for a 0 len io from a tricksy fs */
1131 if (rw
== READ
&& !iov_iter_count(iter
))
1134 dio
= kmem_cache_alloc(dio_cache
, GFP_KERNEL
);
1139 * Believe it or not, zeroing out the page array caused a .5%
1140 * performance regression in a database benchmark. So, we take
1141 * care to only zero out what's needed.
1143 memset(dio
, 0, offsetof(struct dio
, pages
));
1146 if (dio
->flags
& DIO_LOCKING
) {
1148 struct address_space
*mapping
=
1149 iocb
->ki_filp
->f_mapping
;
1151 /* will be released by direct_io_worker */
1152 mutex_lock(&inode
->i_mutex
);
1154 retval
= filemap_write_and_wait_range(mapping
, offset
,
1157 mutex_unlock(&inode
->i_mutex
);
1158 kmem_cache_free(dio_cache
, dio
);
1165 * For file extending writes updating i_size before data writeouts
1166 * complete can expose uninitialized blocks in dumb filesystems.
1167 * In that case we need to wait for I/O completion even if asked
1168 * for an asynchronous write.
1170 if (is_sync_kiocb(iocb
))
1171 dio
->is_async
= false;
1172 else if (!(dio
->flags
& DIO_ASYNC_EXTEND
) &&
1173 (rw
& WRITE
) && end
> i_size_read(inode
))
1174 dio
->is_async
= false;
1176 dio
->is_async
= true;
1182 * For AIO O_(D)SYNC writes we need to defer completions to a workqueue
1183 * so that we can call ->fsync.
1185 if (dio
->is_async
&& (rw
& WRITE
) &&
1186 ((iocb
->ki_filp
->f_flags
& O_DSYNC
) ||
1187 IS_SYNC(iocb
->ki_filp
->f_mapping
->host
))) {
1188 retval
= dio_set_defer_completion(dio
);
1191 * We grab i_mutex only for reads so we don't have
1192 * to release it here
1194 kmem_cache_free(dio_cache
, dio
);
1200 * Will be decremented at I/O completion time.
1202 atomic_inc(&inode
->i_dio_count
);
1205 sdio
.blkbits
= blkbits
;
1206 sdio
.blkfactor
= i_blkbits
- blkbits
;
1207 sdio
.block_in_file
= offset
>> blkbits
;
1209 sdio
.get_block
= get_block
;
1210 dio
->end_io
= end_io
;
1211 sdio
.submit_io
= submit_io
;
1212 sdio
.final_block_in_bio
= -1;
1213 sdio
.next_block_for_io
= -1;
1216 dio
->i_size
= i_size_read(inode
);
1218 spin_lock_init(&dio
->bio_lock
);
1222 sdio
.final_block_in_request
=
1223 (offset
+ iov_iter_count(iter
)) >> blkbits
;
1226 * In case of non-aligned buffers, we may need 2 more
1227 * pages since we need to zero out first and last block.
1229 if (unlikely(sdio
.blkfactor
))
1230 sdio
.pages_in_io
= 2;
1232 sdio
.pages_in_io
+= iov_iter_npages(iter
, INT_MAX
);
1234 blk_start_plug(&plug
);
1236 retval
= do_direct_IO(dio
, &sdio
, &map_bh
);
1238 dio_cleanup(dio
, &sdio
);
1240 if (retval
== -ENOTBLK
) {
1242 * The remaining part of the request will be
1243 * be handled by buffered I/O when we return
1248 * There may be some unwritten disk at the end of a part-written
1249 * fs-block-sized block. Go zero that now.
1251 dio_zero_block(dio
, &sdio
, 1, &map_bh
);
1253 if (sdio
.cur_page
) {
1256 ret2
= dio_send_cur_page(dio
, &sdio
, &map_bh
);
1259 page_cache_release(sdio
.cur_page
);
1260 sdio
.cur_page
= NULL
;
1263 dio_bio_submit(dio
, &sdio
);
1265 blk_finish_plug(&plug
);
1268 * It is possible that, we return short IO due to end of file.
1269 * In that case, we need to release all the pages we got hold on.
1271 dio_cleanup(dio
, &sdio
);
1274 * All block lookups have been performed. For READ requests
1275 * we can let i_mutex go now that its achieved its purpose
1276 * of protecting us from looking up uninitialized blocks.
1278 if (rw
== READ
&& (dio
->flags
& DIO_LOCKING
))
1279 mutex_unlock(&dio
->inode
->i_mutex
);
1282 * The only time we want to leave bios in flight is when a successful
1283 * partial aio read or full aio write have been setup. In that case
1284 * bio completion will call aio_complete. The only time it's safe to
1285 * call aio_complete is when we return -EIOCBQUEUED, so we key on that.
1286 * This had *better* be the only place that raises -EIOCBQUEUED.
1288 BUG_ON(retval
== -EIOCBQUEUED
);
1289 if (dio
->is_async
&& retval
== 0 && dio
->result
&&
1290 ((rw
== READ
) || (dio
->result
== sdio
.size
)))
1291 retval
= -EIOCBQUEUED
;
1293 if (retval
!= -EIOCBQUEUED
)
1294 dio_await_completion(dio
);
1296 if (drop_refcount(dio
) == 0) {
1297 retval
= dio_complete(dio
, offset
, retval
, false);
1299 BUG_ON(retval
!= -EIOCBQUEUED
);
1306 __blockdev_direct_IO(int rw
, struct kiocb
*iocb
, struct inode
*inode
,
1307 struct block_device
*bdev
, struct iov_iter
*iter
, loff_t offset
,
1308 get_block_t get_block
, dio_iodone_t end_io
,
1309 dio_submit_t submit_io
, int flags
)
1312 * The block device state is needed in the end to finally
1313 * submit everything. Since it's likely to be cache cold
1314 * prefetch it here as first thing to hide some of the
1317 * Attempt to prefetch the pieces we likely need later.
1319 prefetch(&bdev
->bd_disk
->part_tbl
);
1320 prefetch(bdev
->bd_queue
);
1321 prefetch((char *)bdev
->bd_queue
+ SMP_CACHE_BYTES
);
1323 return do_blockdev_direct_IO(rw
, iocb
, inode
, bdev
, iter
, offset
,
1324 get_block
, end_io
, submit_io
, flags
);
1327 EXPORT_SYMBOL(__blockdev_direct_IO
);
1329 static __init
int dio_init(void)
1331 dio_cache
= KMEM_CACHE(dio
, SLAB_PANIC
);
1334 module_init(dio_init
)