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>
41 * How many user pages to map in one call to get_user_pages(). This determines
42 * the size of a structure in the slab cache
47 * This code generally works in units of "dio_blocks". A dio_block is
48 * somewhere between the hard sector size and the filesystem block size. it
49 * is determined on a per-invocation basis. When talking to the filesystem
50 * we need to convert dio_blocks to fs_blocks by scaling the dio_block quantity
51 * down by dio->blkfactor. Similarly, fs-blocksize quantities are converted
52 * to bio_block quantities by shifting left by blkfactor.
54 * If blkfactor is zero then the user's request was aligned to the filesystem's
58 /* dio_state only used in the submission path */
61 struct bio
*bio
; /* bio under assembly */
62 unsigned blkbits
; /* doesn't change */
63 unsigned blkfactor
; /* When we're using an alignment which
64 is finer than the filesystem's soft
65 blocksize, this specifies how much
66 finer. blkfactor=2 means 1/4-block
67 alignment. Does not change */
68 unsigned start_zero_done
; /* flag: sub-blocksize zeroing has
69 been performed at the start of a
71 int pages_in_io
; /* approximate total IO pages */
72 size_t size
; /* total request size (doesn't change)*/
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 sector_t final_block_in_request
;/* doesn't change */
77 unsigned first_block_in_page
; /* doesn't change, Used only once */
78 int boundary
; /* prev block is at a boundary */
79 int reap_counter
; /* rate limit reaping */
80 get_block_t
*get_block
; /* block mapping function */
81 dio_submit_t
*submit_io
; /* IO submition function */
83 loff_t logical_offset_in_bio
; /* current first logical block in bio */
84 sector_t final_block_in_bio
; /* current final block in bio + 1 */
85 sector_t next_block_for_io
; /* next block to be put under IO,
86 in dio_blocks units */
89 * Deferred addition of a page to the dio. These variables are
90 * private to dio_send_cur_page(), submit_page_section() and
93 struct page
*cur_page
; /* The page */
94 unsigned cur_page_offset
; /* Offset into it, in bytes */
95 unsigned cur_page_len
; /* Nr of bytes at cur_page_offset */
96 sector_t cur_page_block
; /* Where it starts */
97 loff_t cur_page_fs_offset
; /* Offset in file */
100 * Page fetching state. These variables belong to dio_refill_pages().
102 int curr_page
; /* changes */
103 int total_pages
; /* doesn't change */
104 unsigned long curr_user_address
;/* changes */
107 * Page queue. These variables belong to dio_refill_pages() and
110 unsigned head
; /* next page to process */
111 unsigned tail
; /* last valid page + 1 */
114 /* dio_state communicated between submission path and end_io */
116 int flags
; /* doesn't change */
119 loff_t i_size
; /* i_size when submitted */
120 dio_iodone_t
*end_io
; /* IO completion function */
121 struct buffer_head map_bh
; /* last get_block() result */
124 /* BIO completion state */
125 spinlock_t bio_lock
; /* protects BIO fields below */
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 int is_async
; /* is IO async ? */
133 int io_error
; /* IO error in completion path */
134 ssize_t result
; /* IO result */
136 int page_errors
; /* errno from get_user_pages() */
139 * pages[] (and any fields placed after it) are not zeroed out at
140 * allocation time. Don't add new fields after pages[] unless you
141 * wish that they not be zeroed.
143 struct page
*pages
[DIO_PAGES
]; /* page buffer */
146 static void __inode_dio_wait(struct inode
*inode
)
148 wait_queue_head_t
*wq
= bit_waitqueue(&inode
->i_state
, __I_DIO_WAKEUP
);
149 DEFINE_WAIT_BIT(q
, &inode
->i_state
, __I_DIO_WAKEUP
);
152 prepare_to_wait(wq
, &q
.wait
, TASK_UNINTERRUPTIBLE
);
153 if (atomic_read(&inode
->i_dio_count
))
155 } while (atomic_read(&inode
->i_dio_count
));
156 finish_wait(wq
, &q
.wait
);
160 * inode_dio_wait - wait for outstanding DIO requests to finish
161 * @inode: inode to wait for
163 * Waits for all pending direct I/O requests to finish so that we can
164 * proceed with a truncate or equivalent operation.
166 * Must be called under a lock that serializes taking new references
167 * to i_dio_count, usually by inode->i_mutex.
169 void inode_dio_wait(struct inode
*inode
)
171 if (atomic_read(&inode
->i_dio_count
))
172 __inode_dio_wait(inode
);
174 EXPORT_SYMBOL_GPL(inode_dio_wait
);
177 * inode_dio_done - signal finish of a direct I/O requests
178 * @inode: inode the direct I/O happens on
180 * This is called once we've finished processing a direct I/O request,
181 * and is used to wake up callers waiting for direct I/O to be quiesced.
183 void inode_dio_done(struct inode
*inode
)
185 if (atomic_dec_and_test(&inode
->i_dio_count
))
186 wake_up_bit(&inode
->i_state
, __I_DIO_WAKEUP
);
188 EXPORT_SYMBOL_GPL(inode_dio_done
);
191 * How many pages are in the queue?
193 static inline unsigned dio_pages_present(struct dio_submit
*sdio
)
195 return sdio
->tail
- sdio
->head
;
199 * Go grab and pin some userspace pages. Typically we'll get 64 at a time.
201 static int dio_refill_pages(struct dio
*dio
, struct dio_submit
*sdio
)
206 nr_pages
= min(sdio
->total_pages
- sdio
->curr_page
, DIO_PAGES
);
207 ret
= get_user_pages_fast(
208 sdio
->curr_user_address
, /* Where from? */
209 nr_pages
, /* How many pages? */
210 dio
->rw
== READ
, /* Write to memory? */
211 &dio
->pages
[0]); /* Put results here */
213 if (ret
< 0 && sdio
->blocks_available
&& (dio
->rw
& WRITE
)) {
214 struct page
*page
= ZERO_PAGE(0);
216 * A memory fault, but the filesystem has some outstanding
217 * mapped blocks. We need to use those blocks up to avoid
218 * leaking stale data in the file.
220 if (dio
->page_errors
== 0)
221 dio
->page_errors
= ret
;
222 page_cache_get(page
);
223 dio
->pages
[0] = page
;
231 sdio
->curr_user_address
+= ret
* PAGE_SIZE
;
232 sdio
->curr_page
+= ret
;
242 * Get another userspace page. Returns an ERR_PTR on error. Pages are
243 * buffered inside the dio so that we can call get_user_pages() against a
244 * decent number of pages, less frequently. To provide nicer use of the
247 static struct page
*dio_get_page(struct dio
*dio
, struct dio_submit
*sdio
)
249 if (dio_pages_present(sdio
) == 0) {
252 ret
= dio_refill_pages(dio
, sdio
);
255 BUG_ON(dio_pages_present(sdio
) == 0);
257 return dio
->pages
[sdio
->head
++];
261 * dio_complete() - called when all DIO BIO I/O has been completed
262 * @offset: the byte offset in the file of the completed operation
264 * This releases locks as dictated by the locking type, lets interested parties
265 * know that a DIO operation has completed, and calculates the resulting return
266 * code for the operation.
268 * It lets the filesystem know if it registered an interest earlier via
269 * get_block. Pass the private field of the map buffer_head so that
270 * filesystems can use it to hold additional state between get_block calls and
273 static ssize_t
dio_complete(struct dio
*dio
, loff_t offset
, ssize_t ret
, bool is_async
)
275 ssize_t transferred
= 0;
278 * AIO submission can race with bio completion to get here while
279 * expecting to have the last io completed by bio completion.
280 * In that case -EIOCBQUEUED is in fact not an error we want
281 * to preserve through this call.
283 if (ret
== -EIOCBQUEUED
)
287 transferred
= dio
->result
;
289 /* Check for short read case */
290 if ((dio
->rw
== READ
) && ((offset
+ transferred
) > dio
->i_size
))
291 transferred
= dio
->i_size
- offset
;
295 ret
= dio
->page_errors
;
301 if (dio
->end_io
&& dio
->result
) {
302 dio
->end_io(dio
->iocb
, offset
, transferred
,
303 dio
->map_bh
.b_private
, ret
, is_async
);
306 aio_complete(dio
->iocb
, ret
, 0);
307 inode_dio_done(dio
->inode
);
313 static int dio_bio_complete(struct dio
*dio
, struct bio
*bio
);
315 * Asynchronous IO callback.
317 static void dio_bio_end_aio(struct bio
*bio
, int error
)
319 struct dio
*dio
= bio
->bi_private
;
320 unsigned long remaining
;
323 /* cleanup the bio */
324 dio_bio_complete(dio
, bio
);
326 spin_lock_irqsave(&dio
->bio_lock
, flags
);
327 remaining
= --dio
->refcount
;
328 if (remaining
== 1 && dio
->waiter
)
329 wake_up_process(dio
->waiter
);
330 spin_unlock_irqrestore(&dio
->bio_lock
, flags
);
332 if (remaining
== 0) {
333 dio_complete(dio
, dio
->iocb
->ki_pos
, 0, true);
339 * The BIO completion handler simply queues the BIO up for the process-context
342 * During I/O bi_private points at the dio. After I/O, bi_private is used to
343 * implement a singly-linked list of completed BIOs, at dio->bio_list.
345 static void dio_bio_end_io(struct bio
*bio
, int error
)
347 struct dio
*dio
= bio
->bi_private
;
350 spin_lock_irqsave(&dio
->bio_lock
, flags
);
351 bio
->bi_private
= dio
->bio_list
;
353 if (--dio
->refcount
== 1 && dio
->waiter
)
354 wake_up_process(dio
->waiter
);
355 spin_unlock_irqrestore(&dio
->bio_lock
, flags
);
359 * dio_end_io - handle the end io action for the given bio
360 * @bio: The direct io bio thats being completed
361 * @error: Error if there was one
363 * This is meant to be called by any filesystem that uses their own dio_submit_t
364 * so that the DIO specific endio actions are dealt with after the filesystem
365 * has done it's completion work.
367 void dio_end_io(struct bio
*bio
, int error
)
369 struct dio
*dio
= bio
->bi_private
;
372 dio_bio_end_aio(bio
, error
);
374 dio_bio_end_io(bio
, error
);
376 EXPORT_SYMBOL_GPL(dio_end_io
);
379 dio_bio_alloc(struct dio
*dio
, struct dio_submit
*sdio
,
380 struct block_device
*bdev
,
381 sector_t first_sector
, int nr_vecs
)
386 * bio_alloc() is guaranteed to return a bio when called with
387 * __GFP_WAIT and we request a valid number of vectors.
389 bio
= bio_alloc(GFP_KERNEL
, nr_vecs
);
392 bio
->bi_sector
= first_sector
;
394 bio
->bi_end_io
= dio_bio_end_aio
;
396 bio
->bi_end_io
= dio_bio_end_io
;
399 sdio
->logical_offset_in_bio
= sdio
->cur_page_fs_offset
;
403 * In the AIO read case we speculatively dirty the pages before starting IO.
404 * During IO completion, any of these pages which happen to have been written
405 * back will be redirtied by bio_check_pages_dirty().
407 * bios hold a dio reference between submit_bio and ->end_io.
409 static void dio_bio_submit(struct dio
*dio
, struct dio_submit
*sdio
)
411 struct bio
*bio
= sdio
->bio
;
414 bio
->bi_private
= dio
;
416 spin_lock_irqsave(&dio
->bio_lock
, flags
);
418 spin_unlock_irqrestore(&dio
->bio_lock
, flags
);
420 if (dio
->is_async
&& dio
->rw
== READ
)
421 bio_set_pages_dirty(bio
);
424 sdio
->submit_io(dio
->rw
, bio
, dio
->inode
,
425 sdio
->logical_offset_in_bio
);
427 submit_bio(dio
->rw
, bio
);
431 sdio
->logical_offset_in_bio
= 0;
435 * Release any resources in case of a failure
437 static void dio_cleanup(struct dio
*dio
, struct dio_submit
*sdio
)
439 while (dio_pages_present(sdio
))
440 page_cache_release(dio_get_page(dio
, sdio
));
444 * Wait for the next BIO to complete. Remove it and return it. NULL is
445 * returned once all BIOs have been completed. This must only be called once
446 * all bios have been issued so that dio->refcount can only decrease. This
447 * requires that that the caller hold a reference on the dio.
449 static struct bio
*dio_await_one(struct dio
*dio
)
452 struct bio
*bio
= NULL
;
454 spin_lock_irqsave(&dio
->bio_lock
, flags
);
457 * Wait as long as the list is empty and there are bios in flight. bio
458 * completion drops the count, maybe adds to the list, and wakes while
459 * holding the bio_lock so we don't need set_current_state()'s barrier
460 * and can call it after testing our condition.
462 while (dio
->refcount
> 1 && dio
->bio_list
== NULL
) {
463 __set_current_state(TASK_UNINTERRUPTIBLE
);
464 dio
->waiter
= current
;
465 spin_unlock_irqrestore(&dio
->bio_lock
, flags
);
467 /* wake up sets us TASK_RUNNING */
468 spin_lock_irqsave(&dio
->bio_lock
, flags
);
473 dio
->bio_list
= bio
->bi_private
;
475 spin_unlock_irqrestore(&dio
->bio_lock
, flags
);
480 * Process one completed BIO. No locks are held.
482 static int dio_bio_complete(struct dio
*dio
, struct bio
*bio
)
484 const int uptodate
= test_bit(BIO_UPTODATE
, &bio
->bi_flags
);
485 struct bio_vec
*bvec
= bio
->bi_io_vec
;
489 dio
->io_error
= -EIO
;
491 if (dio
->is_async
&& dio
->rw
== READ
) {
492 bio_check_pages_dirty(bio
); /* transfers ownership */
494 for (page_no
= 0; page_no
< bio
->bi_vcnt
; page_no
++) {
495 struct page
*page
= bvec
[page_no
].bv_page
;
497 if (dio
->rw
== READ
&& !PageCompound(page
))
498 set_page_dirty_lock(page
);
499 page_cache_release(page
);
503 return uptodate
? 0 : -EIO
;
507 * Wait on and process all in-flight BIOs. This must only be called once
508 * all bios have been issued so that the refcount can only decrease.
509 * This just waits for all bios to make it through dio_bio_complete. IO
510 * errors are propagated through dio->io_error and should be propagated via
513 static void dio_await_completion(struct dio
*dio
)
517 bio
= dio_await_one(dio
);
519 dio_bio_complete(dio
, bio
);
524 * A really large O_DIRECT read or write can generate a lot of BIOs. So
525 * to keep the memory consumption sane we periodically reap any completed BIOs
526 * during the BIO generation phase.
528 * This also helps to limit the peak amount of pinned userspace memory.
530 static int dio_bio_reap(struct dio
*dio
, struct dio_submit
*sdio
)
534 if (sdio
->reap_counter
++ >= 64) {
535 while (dio
->bio_list
) {
540 spin_lock_irqsave(&dio
->bio_lock
, flags
);
542 dio
->bio_list
= bio
->bi_private
;
543 spin_unlock_irqrestore(&dio
->bio_lock
, flags
);
544 ret2
= dio_bio_complete(dio
, bio
);
548 sdio
->reap_counter
= 0;
554 * Call into the fs to map some more disk blocks. We record the current number
555 * of available blocks at sdio->blocks_available. These are in units of the
556 * fs blocksize, (1 << inode->i_blkbits).
558 * The fs is allowed to map lots of blocks at once. If it wants to do that,
559 * it uses the passed inode-relative block number as the file offset, as usual.
561 * get_block() is passed the number of i_blkbits-sized blocks which direct_io
562 * has remaining to do. The fs should not map more than this number of blocks.
564 * If the fs has mapped a lot of blocks, it should populate bh->b_size to
565 * indicate how much contiguous disk space has been made available at
568 * If *any* of the mapped blocks are new, then the fs must set buffer_new().
569 * This isn't very efficient...
571 * In the case of filesystem holes: the fs may return an arbitrarily-large
572 * hole by returning an appropriate value in b_size and by clearing
573 * buffer_mapped(). However the direct-io code will only process holes one
574 * block at a time - it will repeatedly call get_block() as it walks the hole.
576 static int get_more_blocks(struct dio
*dio
, struct dio_submit
*sdio
)
579 struct buffer_head
*map_bh
= &dio
->map_bh
;
580 sector_t fs_startblk
; /* Into file, in filesystem-sized blocks */
581 unsigned long fs_count
; /* Number of filesystem-sized blocks */
582 unsigned long dio_count
;/* Number of dio_block-sized blocks */
583 unsigned long blkmask
;
587 * If there was a memory error and we've overwritten all the
588 * mapped blocks then we can now return that memory error
590 ret
= dio
->page_errors
;
592 BUG_ON(sdio
->block_in_file
>= sdio
->final_block_in_request
);
593 fs_startblk
= sdio
->block_in_file
>> sdio
->blkfactor
;
594 dio_count
= sdio
->final_block_in_request
- sdio
->block_in_file
;
595 fs_count
= dio_count
>> sdio
->blkfactor
;
596 blkmask
= (1 << sdio
->blkfactor
) - 1;
597 if (dio_count
& blkmask
)
601 map_bh
->b_size
= fs_count
<< dio
->inode
->i_blkbits
;
604 * For writes inside i_size on a DIO_SKIP_HOLES filesystem we
605 * forbid block creations: only overwrites are permitted.
606 * We will return early to the caller once we see an
607 * unmapped buffer head returned, and the caller will fall
608 * back to buffered I/O.
610 * Otherwise the decision is left to the get_blocks method,
611 * which may decide to handle it or also return an unmapped
614 create
= dio
->rw
& WRITE
;
615 if (dio
->flags
& DIO_SKIP_HOLES
) {
616 if (sdio
->block_in_file
< (i_size_read(dio
->inode
) >>
621 ret
= (*sdio
->get_block
)(dio
->inode
, fs_startblk
,
628 * There is no bio. Make one now.
630 static int dio_new_bio(struct dio
*dio
, struct dio_submit
*sdio
,
631 sector_t start_sector
)
636 ret
= dio_bio_reap(dio
, sdio
);
639 sector
= start_sector
<< (sdio
->blkbits
- 9);
640 nr_pages
= min(sdio
->pages_in_io
, bio_get_nr_vecs(dio
->map_bh
.b_bdev
));
641 nr_pages
= min(nr_pages
, BIO_MAX_PAGES
);
642 BUG_ON(nr_pages
<= 0);
643 dio_bio_alloc(dio
, sdio
, dio
->map_bh
.b_bdev
, sector
, nr_pages
);
650 * Attempt to put the current chunk of 'cur_page' into the current BIO. If
651 * that was successful then update final_block_in_bio and take a ref against
652 * the just-added page.
654 * Return zero on success. Non-zero means the caller needs to start a new BIO.
656 static int dio_bio_add_page(struct dio_submit
*sdio
)
660 ret
= bio_add_page(sdio
->bio
, sdio
->cur_page
,
661 sdio
->cur_page_len
, sdio
->cur_page_offset
);
662 if (ret
== sdio
->cur_page_len
) {
664 * Decrement count only, if we are done with this page
666 if ((sdio
->cur_page_len
+ sdio
->cur_page_offset
) == PAGE_SIZE
)
668 page_cache_get(sdio
->cur_page
);
669 sdio
->final_block_in_bio
= sdio
->cur_page_block
+
670 (sdio
->cur_page_len
>> sdio
->blkbits
);
679 * Put cur_page under IO. The section of cur_page which is described by
680 * cur_page_offset,cur_page_len is put into a BIO. The section of cur_page
681 * starts on-disk at cur_page_block.
683 * We take a ref against the page here (on behalf of its presence in the bio).
685 * The caller of this function is responsible for removing cur_page from the
686 * dio, and for dropping the refcount which came from that presence.
688 static int dio_send_cur_page(struct dio
*dio
, struct dio_submit
*sdio
)
693 loff_t cur_offset
= sdio
->cur_page_fs_offset
;
694 loff_t bio_next_offset
= sdio
->logical_offset_in_bio
+
698 * See whether this new request is contiguous with the old.
700 * Btrfs cannot handle having logically non-contiguous requests
701 * submitted. For example if you have
703 * Logical: [0-4095][HOLE][8192-12287]
704 * Physical: [0-4095] [4096-8191]
706 * We cannot submit those pages together as one BIO. So if our
707 * current logical offset in the file does not equal what would
708 * be the next logical offset in the bio, submit the bio we
711 if (sdio
->final_block_in_bio
!= sdio
->cur_page_block
||
712 cur_offset
!= bio_next_offset
)
713 dio_bio_submit(dio
, sdio
);
715 * Submit now if the underlying fs is about to perform a
718 else if (sdio
->boundary
)
719 dio_bio_submit(dio
, sdio
);
722 if (sdio
->bio
== NULL
) {
723 ret
= dio_new_bio(dio
, sdio
, sdio
->cur_page_block
);
728 if (dio_bio_add_page(sdio
) != 0) {
729 dio_bio_submit(dio
, sdio
);
730 ret
= dio_new_bio(dio
, sdio
, sdio
->cur_page_block
);
732 ret
= dio_bio_add_page(sdio
);
741 * An autonomous function to put a chunk of a page under deferred IO.
743 * The caller doesn't actually know (or care) whether this piece of page is in
744 * a BIO, or is under IO or whatever. We just take care of all possible
745 * situations here. The separation between the logic of do_direct_IO() and
746 * that of submit_page_section() is important for clarity. Please don't break.
748 * The chunk of page starts on-disk at blocknr.
750 * We perform deferred IO, by recording the last-submitted page inside our
751 * private part of the dio structure. If possible, we just expand the IO
752 * across that page here.
754 * If that doesn't work out then we put the old page into the bio and add this
755 * page to the dio instead.
758 submit_page_section(struct dio
*dio
, struct dio_submit
*sdio
, struct page
*page
,
759 unsigned offset
, unsigned len
, sector_t blocknr
)
763 if (dio
->rw
& WRITE
) {
765 * Read accounting is performed in submit_bio()
767 task_io_account_write(len
);
771 * Can we just grow the current page's presence in the dio?
773 if (sdio
->cur_page
== page
&&
774 sdio
->cur_page_offset
+ sdio
->cur_page_len
== offset
&&
775 sdio
->cur_page_block
+
776 (sdio
->cur_page_len
>> sdio
->blkbits
) == blocknr
) {
777 sdio
->cur_page_len
+= len
;
780 * If sdio->boundary then we want to schedule the IO now to
781 * avoid metadata seeks.
783 if (sdio
->boundary
) {
784 ret
= dio_send_cur_page(dio
, sdio
);
785 page_cache_release(sdio
->cur_page
);
786 sdio
->cur_page
= NULL
;
792 * If there's a deferred page already there then send it.
794 if (sdio
->cur_page
) {
795 ret
= dio_send_cur_page(dio
, sdio
);
796 page_cache_release(sdio
->cur_page
);
797 sdio
->cur_page
= NULL
;
802 page_cache_get(page
); /* It is in dio */
803 sdio
->cur_page
= page
;
804 sdio
->cur_page_offset
= offset
;
805 sdio
->cur_page_len
= len
;
806 sdio
->cur_page_block
= blocknr
;
807 sdio
->cur_page_fs_offset
= sdio
->block_in_file
<< sdio
->blkbits
;
813 * Clean any dirty buffers in the blockdev mapping which alias newly-created
814 * file blocks. Only called for S_ISREG files - blockdevs do not set
817 static void clean_blockdev_aliases(struct dio
*dio
)
822 nblocks
= dio
->map_bh
.b_size
>> dio
->inode
->i_blkbits
;
824 for (i
= 0; i
< nblocks
; i
++) {
825 unmap_underlying_metadata(dio
->map_bh
.b_bdev
,
826 dio
->map_bh
.b_blocknr
+ i
);
831 * If we are not writing the entire block and get_block() allocated
832 * the block for us, we need to fill-in the unused portion of the
833 * block with zeros. This happens only if user-buffer, fileoffset or
834 * io length is not filesystem block-size multiple.
836 * `end' is zero if we're doing the start of the IO, 1 at the end of the
839 static void dio_zero_block(struct dio
*dio
, struct dio_submit
*sdio
, int end
)
841 unsigned dio_blocks_per_fs_block
;
842 unsigned this_chunk_blocks
; /* In dio_blocks */
843 unsigned this_chunk_bytes
;
846 sdio
->start_zero_done
= 1;
847 if (!sdio
->blkfactor
|| !buffer_new(&dio
->map_bh
))
850 dio_blocks_per_fs_block
= 1 << sdio
->blkfactor
;
851 this_chunk_blocks
= sdio
->block_in_file
& (dio_blocks_per_fs_block
- 1);
853 if (!this_chunk_blocks
)
857 * We need to zero out part of an fs block. It is either at the
858 * beginning or the end of the fs block.
861 this_chunk_blocks
= dio_blocks_per_fs_block
- this_chunk_blocks
;
863 this_chunk_bytes
= this_chunk_blocks
<< sdio
->blkbits
;
866 if (submit_page_section(dio
, sdio
, page
, 0, this_chunk_bytes
,
867 sdio
->next_block_for_io
))
870 sdio
->next_block_for_io
+= this_chunk_blocks
;
874 * Walk the user pages, and the file, mapping blocks to disk and generating
875 * a sequence of (page,offset,len,block) mappings. These mappings are injected
876 * into submit_page_section(), which takes care of the next stage of submission
878 * Direct IO against a blockdev is different from a file. Because we can
879 * happily perform page-sized but 512-byte aligned IOs. It is important that
880 * blockdev IO be able to have fine alignment and large sizes.
882 * So what we do is to permit the ->get_block function to populate bh.b_size
883 * with the size of IO which is permitted at this offset and this i_blkbits.
885 * For best results, the blockdev should be set up with 512-byte i_blkbits and
886 * it should set b_size to PAGE_SIZE or more inside get_block(). This gives
887 * fine alignment but still allows this function to work in PAGE_SIZE units.
889 static int do_direct_IO(struct dio
*dio
, struct dio_submit
*sdio
)
891 const unsigned blkbits
= sdio
->blkbits
;
892 const unsigned blocks_per_page
= PAGE_SIZE
>> blkbits
;
894 unsigned block_in_page
;
895 struct buffer_head
*map_bh
= &dio
->map_bh
;
898 /* The I/O can start at any block offset within the first page */
899 block_in_page
= sdio
->first_block_in_page
;
901 while (sdio
->block_in_file
< sdio
->final_block_in_request
) {
902 page
= dio_get_page(dio
, sdio
);
908 while (block_in_page
< blocks_per_page
) {
909 unsigned offset_in_page
= block_in_page
<< blkbits
;
910 unsigned this_chunk_bytes
; /* # of bytes mapped */
911 unsigned this_chunk_blocks
; /* # of blocks */
914 if (sdio
->blocks_available
== 0) {
916 * Need to go and map some more disk
918 unsigned long blkmask
;
919 unsigned long dio_remainder
;
921 ret
= get_more_blocks(dio
, sdio
);
923 page_cache_release(page
);
926 if (!buffer_mapped(map_bh
))
929 sdio
->blocks_available
=
930 map_bh
->b_size
>> sdio
->blkbits
;
931 sdio
->next_block_for_io
=
932 map_bh
->b_blocknr
<< sdio
->blkfactor
;
933 if (buffer_new(map_bh
))
934 clean_blockdev_aliases(dio
);
936 if (!sdio
->blkfactor
)
939 blkmask
= (1 << sdio
->blkfactor
) - 1;
940 dio_remainder
= (sdio
->block_in_file
& blkmask
);
943 * If we are at the start of IO and that IO
944 * starts partway into a fs-block,
945 * dio_remainder will be non-zero. If the IO
946 * is a read then we can simply advance the IO
947 * cursor to the first block which is to be
948 * read. But if the IO is a write and the
949 * block was newly allocated we cannot do that;
950 * the start of the fs block must be zeroed out
953 if (!buffer_new(map_bh
))
954 sdio
->next_block_for_io
+= dio_remainder
;
955 sdio
->blocks_available
-= dio_remainder
;
959 if (!buffer_mapped(map_bh
)) {
960 loff_t i_size_aligned
;
962 /* AKPM: eargh, -ENOTBLK is a hack */
963 if (dio
->rw
& WRITE
) {
964 page_cache_release(page
);
969 * Be sure to account for a partial block as the
970 * last block in the file
972 i_size_aligned
= ALIGN(i_size_read(dio
->inode
),
974 if (sdio
->block_in_file
>=
975 i_size_aligned
>> blkbits
) {
977 page_cache_release(page
);
980 zero_user(page
, block_in_page
<< blkbits
,
982 sdio
->block_in_file
++;
988 * If we're performing IO which has an alignment which
989 * is finer than the underlying fs, go check to see if
990 * we must zero out the start of this block.
992 if (unlikely(sdio
->blkfactor
&& !sdio
->start_zero_done
))
993 dio_zero_block(dio
, sdio
, 0);
996 * Work out, in this_chunk_blocks, how much disk we
997 * can add to this page
999 this_chunk_blocks
= sdio
->blocks_available
;
1000 u
= (PAGE_SIZE
- offset_in_page
) >> blkbits
;
1001 if (this_chunk_blocks
> u
)
1002 this_chunk_blocks
= u
;
1003 u
= sdio
->final_block_in_request
- sdio
->block_in_file
;
1004 if (this_chunk_blocks
> u
)
1005 this_chunk_blocks
= u
;
1006 this_chunk_bytes
= this_chunk_blocks
<< blkbits
;
1007 BUG_ON(this_chunk_bytes
== 0);
1009 sdio
->boundary
= buffer_boundary(map_bh
);
1010 ret
= submit_page_section(dio
, sdio
, page
,
1013 sdio
->next_block_for_io
);
1015 page_cache_release(page
);
1018 sdio
->next_block_for_io
+= this_chunk_blocks
;
1020 sdio
->block_in_file
+= this_chunk_blocks
;
1021 block_in_page
+= this_chunk_blocks
;
1022 sdio
->blocks_available
-= this_chunk_blocks
;
1024 BUG_ON(sdio
->block_in_file
> sdio
->final_block_in_request
);
1025 if (sdio
->block_in_file
== sdio
->final_block_in_request
)
1029 /* Drop the ref which was taken in get_user_pages() */
1030 page_cache_release(page
);
1038 direct_io_worker(int rw
, struct kiocb
*iocb
, struct inode
*inode
,
1039 const struct iovec
*iov
, loff_t offset
, unsigned long nr_segs
,
1040 unsigned blkbits
, get_block_t get_block
, dio_iodone_t end_io
,
1041 dio_submit_t submit_io
, struct dio
*dio
, struct dio_submit
*sdio
)
1043 unsigned long user_addr
;
1044 unsigned long flags
;
1052 sdio
->blkbits
= blkbits
;
1053 sdio
->blkfactor
= inode
->i_blkbits
- blkbits
;
1054 sdio
->block_in_file
= offset
>> blkbits
;
1056 sdio
->get_block
= get_block
;
1057 dio
->end_io
= end_io
;
1058 sdio
->submit_io
= submit_io
;
1059 sdio
->final_block_in_bio
= -1;
1060 sdio
->next_block_for_io
= -1;
1063 dio
->i_size
= i_size_read(inode
);
1065 spin_lock_init(&dio
->bio_lock
);
1069 * In case of non-aligned buffers, we may need 2 more
1070 * pages since we need to zero out first and last block.
1072 if (unlikely(sdio
->blkfactor
))
1073 sdio
->pages_in_io
= 2;
1075 for (seg
= 0; seg
< nr_segs
; seg
++) {
1076 user_addr
= (unsigned long)iov
[seg
].iov_base
;
1077 sdio
->pages_in_io
+=
1078 ((user_addr
+iov
[seg
].iov_len
+PAGE_SIZE
-1)/PAGE_SIZE
1079 - user_addr
/PAGE_SIZE
);
1082 for (seg
= 0; seg
< nr_segs
; seg
++) {
1083 user_addr
= (unsigned long)iov
[seg
].iov_base
;
1084 sdio
->size
+= bytes
= iov
[seg
].iov_len
;
1086 /* Index into the first page of the first block */
1087 sdio
->first_block_in_page
= (user_addr
& ~PAGE_MASK
) >> blkbits
;
1088 sdio
->final_block_in_request
= sdio
->block_in_file
+
1090 /* Page fetching state */
1093 sdio
->curr_page
= 0;
1095 sdio
->total_pages
= 0;
1096 if (user_addr
& (PAGE_SIZE
-1)) {
1097 sdio
->total_pages
++;
1098 bytes
-= PAGE_SIZE
- (user_addr
& (PAGE_SIZE
- 1));
1100 sdio
->total_pages
+= (bytes
+ PAGE_SIZE
- 1) / PAGE_SIZE
;
1101 sdio
->curr_user_address
= user_addr
;
1103 ret
= do_direct_IO(dio
, sdio
);
1105 dio
->result
+= iov
[seg
].iov_len
-
1106 ((sdio
->final_block_in_request
- sdio
->block_in_file
) <<
1110 dio_cleanup(dio
, sdio
);
1113 } /* end iovec loop */
1115 if (ret
== -ENOTBLK
) {
1117 * The remaining part of the request will be
1118 * be handled by buffered I/O when we return
1123 * There may be some unwritten disk at the end of a part-written
1124 * fs-block-sized block. Go zero that now.
1126 dio_zero_block(dio
, sdio
, 1);
1128 if (sdio
->cur_page
) {
1129 ret2
= dio_send_cur_page(dio
, sdio
);
1132 page_cache_release(sdio
->cur_page
);
1133 sdio
->cur_page
= NULL
;
1136 dio_bio_submit(dio
, sdio
);
1139 * It is possible that, we return short IO due to end of file.
1140 * In that case, we need to release all the pages we got hold on.
1142 dio_cleanup(dio
, sdio
);
1145 * All block lookups have been performed. For READ requests
1146 * we can let i_mutex go now that its achieved its purpose
1147 * of protecting us from looking up uninitialized blocks.
1149 if (rw
== READ
&& (dio
->flags
& DIO_LOCKING
))
1150 mutex_unlock(&dio
->inode
->i_mutex
);
1153 * The only time we want to leave bios in flight is when a successful
1154 * partial aio read or full aio write have been setup. In that case
1155 * bio completion will call aio_complete. The only time it's safe to
1156 * call aio_complete is when we return -EIOCBQUEUED, so we key on that.
1157 * This had *better* be the only place that raises -EIOCBQUEUED.
1159 BUG_ON(ret
== -EIOCBQUEUED
);
1160 if (dio
->is_async
&& ret
== 0 && dio
->result
&&
1161 ((rw
& READ
) || (dio
->result
== sdio
->size
)))
1164 if (ret
!= -EIOCBQUEUED
)
1165 dio_await_completion(dio
);
1168 * Sync will always be dropping the final ref and completing the
1169 * operation. AIO can if it was a broken operation described above or
1170 * in fact if all the bios race to complete before we get here. In
1171 * that case dio_complete() translates the EIOCBQUEUED into the proper
1172 * return code that the caller will hand to aio_complete().
1174 * This is managed by the bio_lock instead of being an atomic_t so that
1175 * completion paths can drop their ref and use the remaining count to
1176 * decide to wake the submission path atomically.
1178 spin_lock_irqsave(&dio
->bio_lock
, flags
);
1179 ret2
= --dio
->refcount
;
1180 spin_unlock_irqrestore(&dio
->bio_lock
, flags
);
1183 ret
= dio_complete(dio
, offset
, ret
, false);
1186 BUG_ON(ret
!= -EIOCBQUEUED
);
1192 * This is a library function for use by filesystem drivers.
1194 * The locking rules are governed by the flags parameter:
1195 * - if the flags value contains DIO_LOCKING we use a fancy locking
1196 * scheme for dumb filesystems.
1197 * For writes this function is called under i_mutex and returns with
1198 * i_mutex held, for reads, i_mutex is not held on entry, but it is
1199 * taken and dropped again before returning.
1200 * - if the flags value does NOT contain DIO_LOCKING we don't use any
1201 * internal locking but rather rely on the filesystem to synchronize
1202 * direct I/O reads/writes versus each other and truncate.
1204 * To help with locking against truncate we incremented the i_dio_count
1205 * counter before starting direct I/O, and decrement it once we are done.
1206 * Truncate can wait for it to reach zero to provide exclusion. It is
1207 * expected that filesystem provide exclusion between new direct I/O
1208 * and truncates. For DIO_LOCKING filesystems this is done by i_mutex,
1209 * but other filesystems need to take care of this on their own.
1212 __blockdev_direct_IO(int rw
, struct kiocb
*iocb
, struct inode
*inode
,
1213 struct block_device
*bdev
, const struct iovec
*iov
, loff_t offset
,
1214 unsigned long nr_segs
, get_block_t get_block
, dio_iodone_t end_io
,
1215 dio_submit_t submit_io
, int flags
)
1220 unsigned blkbits
= inode
->i_blkbits
;
1221 unsigned bdev_blkbits
= 0;
1222 unsigned blocksize_mask
= (1 << blkbits
) - 1;
1223 ssize_t retval
= -EINVAL
;
1224 loff_t end
= offset
;
1226 struct dio_submit sdio
= { 0, };
1232 bdev_blkbits
= blksize_bits(bdev_logical_block_size(bdev
));
1234 if (offset
& blocksize_mask
) {
1236 blkbits
= bdev_blkbits
;
1237 blocksize_mask
= (1 << blkbits
) - 1;
1238 if (offset
& blocksize_mask
)
1242 /* Check the memory alignment. Blocks cannot straddle pages */
1243 for (seg
= 0; seg
< nr_segs
; seg
++) {
1244 addr
= (unsigned long)iov
[seg
].iov_base
;
1245 size
= iov
[seg
].iov_len
;
1247 if ((addr
& blocksize_mask
) || (size
& blocksize_mask
)) {
1249 blkbits
= bdev_blkbits
;
1250 blocksize_mask
= (1 << blkbits
) - 1;
1251 if ((addr
& blocksize_mask
) || (size
& blocksize_mask
))
1256 /* watch out for a 0 len io from a tricksy fs */
1257 if (rw
== READ
&& end
== offset
)
1260 dio
= kmalloc(sizeof(*dio
), GFP_KERNEL
);
1265 * Believe it or not, zeroing out the page array caused a .5%
1266 * performance regression in a database benchmark. So, we take
1267 * care to only zero out what's needed.
1269 memset(dio
, 0, offsetof(struct dio
, pages
));
1272 if (dio
->flags
& DIO_LOCKING
) {
1274 struct address_space
*mapping
=
1275 iocb
->ki_filp
->f_mapping
;
1277 /* will be released by direct_io_worker */
1278 mutex_lock(&inode
->i_mutex
);
1280 retval
= filemap_write_and_wait_range(mapping
, offset
,
1283 mutex_unlock(&inode
->i_mutex
);
1291 * Will be decremented at I/O completion time.
1293 atomic_inc(&inode
->i_dio_count
);
1296 * For file extending writes updating i_size before data
1297 * writeouts complete can expose uninitialized blocks. So
1298 * even for AIO, we need to wait for i/o to complete before
1299 * returning in this case.
1301 dio
->is_async
= !is_sync_kiocb(iocb
) && !((rw
& WRITE
) &&
1302 (end
> i_size_read(inode
)));
1304 retval
= direct_io_worker(rw
, iocb
, inode
, iov
, offset
,
1305 nr_segs
, blkbits
, get_block
, end_io
,
1306 submit_io
, dio
, &sdio
);
1311 EXPORT_SYMBOL(__blockdev_direct_IO
);