4 * Copyright (C) 2002, Linus Torvalds.
8 * 04Jul2002 akpm@zip.com.au
10 * 11Sep2002 janetinc@us.ibm.com
11 * added readv/writev support.
12 * 29Oct2002 akpm@zip.com.au
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 <asm/atomic.h>
41 * How many user pages to map in one call to get_user_pages(). This determines
42 * the size of a structure on the stack.
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
57 * lock_type is DIO_LOCKING for regular files on direct-IO-naive filesystems.
58 * This determines whether we need to do the fancy locking which prevents
59 * direct-IO from being able to read uninitialised disk blocks. If its zero
60 * (blockdev) this locking is not done, and if it is DIO_OWN_LOCKING i_mutex is
61 * not held for the entire direct write (taken briefly, initially, during a
62 * direct read though, but its never held for the duration of a direct-IO).
66 /* BIO submission state */
67 struct bio *bio; /* bio under assembly */
70 loff_t i_size; /* i_size when submitted */
71 int lock_type; /* doesn't change */
72 unsigned blkbits; /* doesn't change */
73 unsigned blkfactor; /* When we're using an alignment which
74 is finer than the filesystem's soft
75 blocksize, this specifies how much
76 finer. blkfactor=2 means 1/4-block
77 alignment. Does not change */
78 unsigned start_zero_done; /* flag: sub-blocksize zeroing has
79 been performed at the start of a
81 int pages_in_io; /* approximate total IO pages */
82 size_t size; /* total request size (doesn't change)*/
83 sector_t block_in_file; /* Current offset into the underlying
84 file in dio_block units. */
85 unsigned blocks_available; /* At block_in_file. changes */
86 sector_t final_block_in_request;/* doesn't change */
87 unsigned first_block_in_page; /* doesn't change, Used only once */
88 int boundary; /* prev block is at a boundary */
89 int reap_counter; /* rate limit reaping */
90 get_block_t *get_block; /* block mapping function */
91 dio_iodone_t *end_io; /* IO completion function */
92 sector_t final_block_in_bio; /* current final block in bio + 1 */
93 sector_t next_block_for_io; /* next block to be put under IO,
94 in dio_blocks units */
95 struct buffer_head map_bh; /* last get_block() result */
98 * Deferred addition of a page to the dio. These variables are
99 * private to dio_send_cur_page(), submit_page_section() and
100 * dio_bio_add_page().
102 struct page *cur_page; /* The page */
103 unsigned cur_page_offset; /* Offset into it, in bytes */
104 unsigned cur_page_len; /* Nr of bytes at cur_page_offset */
105 sector_t cur_page_block; /* Where it starts */
108 * Page fetching state. These variables belong to dio_refill_pages().
110 int curr_page; /* changes */
111 int total_pages; /* doesn't change */
112 unsigned long curr_user_address;/* changes */
115 * Page queue. These variables belong to dio_refill_pages() and
118 struct page *pages[DIO_PAGES]; /* page buffer */
119 unsigned head; /* next page to process */
120 unsigned tail; /* last valid page + 1 */
121 int page_errors; /* errno from get_user_pages() */
123 /* BIO completion state */
124 atomic_t refcount; /* direct_io_worker() and bios */
125 spinlock_t bio_lock; /* protects BIO fields below */
126 struct bio *bio_list; /* singly linked via bi_private */
127 struct task_struct *waiter; /* waiting task (NULL if none) */
129 /* AIO related stuff */
130 struct kiocb *iocb; /* kiocb */
131 int is_async; /* is IO async ? */
132 int io_error; /* IO error in completion path */
133 ssize_t result; /* IO result */
137 * How many pages are in the queue?
139 static inline unsigned dio_pages_present(struct dio *dio)
141 return dio->tail - dio->head;
145 * Go grab and pin some userspace pages. Typically we'll get 64 at a time.
147 static int dio_refill_pages(struct dio *dio)
152 nr_pages = min(dio->total_pages - dio->curr_page, DIO_PAGES);
153 down_read(¤t->mm->mmap_sem);
154 ret = get_user_pages(
155 current, /* Task for fault acounting */
156 current->mm, /* whose pages? */
157 dio->curr_user_address, /* Where from? */
158 nr_pages, /* How many pages? */
159 dio->rw == READ, /* Write to memory? */
163 up_read(¤t->mm->mmap_sem);
165 if (ret < 0 && dio->blocks_available && (dio->rw & WRITE)) {
166 struct page *page = ZERO_PAGE(dio->curr_user_address);
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;
183 dio->curr_user_address += ret * PAGE_SIZE;
184 dio->curr_page += ret;
194 * Get another userspace page. Returns an ERR_PTR on error. Pages are
195 * buffered inside the dio so that we can call get_user_pages() against a
196 * decent number of pages, less frequently. To provide nicer use of the
199 static struct page *dio_get_page(struct dio *dio)
201 if (dio_pages_present(dio) == 0) {
204 ret = dio_refill_pages(dio);
207 BUG_ON(dio_pages_present(dio) == 0);
209 return dio->pages[dio->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 releases locks as dictated by the locking type, lets interested parties
217 * know that a DIO operation has completed, and calculates the resulting return
218 * code for the operation.
220 * It lets the filesystem know if it registered an interest earlier via
221 * get_block. Pass the private field of the map buffer_head so that
222 * filesystems can use it to hold additional state between get_block calls and
225 static int dio_complete(struct dio *dio, loff_t offset, int ret)
227 ssize_t transferred = 0;
230 transferred = dio->result;
232 /* Check for short read case */
233 if ((dio->rw == READ) && ((offset + transferred) > dio->i_size))
234 transferred = dio->i_size - offset;
237 if (dio->end_io && dio->result)
238 dio->end_io(dio->iocb, offset, transferred,
239 dio->map_bh.b_private);
240 if (dio->lock_type == DIO_LOCKING)
241 /* lockdep: non-owner release */
242 up_read_non_owner(&dio->inode->i_alloc_sem);
245 ret = dio->page_errors;
255 * Called when a BIO has been processed. If the count goes to zero then IO is
256 * complete and we can signal this to the AIO layer.
258 static void dio_complete_aio(struct dio *dio)
262 ret = dio_complete(dio, dio->iocb->ki_pos, 0);
264 /* Complete AIO later if falling back to buffered i/o */
265 if (dio->result == dio->size ||
266 ((dio->rw == READ) && dio->result)) {
267 aio_complete(dio->iocb, ret, 0);
272 static int dio_bio_complete(struct dio *dio, struct bio *bio);
274 * Asynchronous IO callback.
276 static int dio_bio_end_aio(struct bio *bio, unsigned int bytes_done, int error)
278 struct dio *dio = bio->bi_private;
279 int waiter_holds_ref = 0;
285 /* cleanup the bio */
286 dio_bio_complete(dio, bio);
288 waiter_holds_ref = !!dio->waiter;
289 remaining = atomic_sub_return(1, (&dio->refcount));
290 if (remaining == 1 && waiter_holds_ref)
291 wake_up_process(dio->waiter);
294 dio_complete_aio(dio);
300 * The BIO completion handler simply queues the BIO up for the process-context
303 * During I/O bi_private points at the dio. After I/O, bi_private is used to
304 * implement a singly-linked list of completed BIOs, at dio->bio_list.
306 static int dio_bio_end_io(struct bio *bio, unsigned int bytes_done, int error)
308 struct dio *dio = bio->bi_private;
314 spin_lock_irqsave(&dio->bio_lock, flags);
315 bio->bi_private = dio->bio_list;
317 if ((atomic_sub_return(1, &dio->refcount) == 1) && dio->waiter)
318 wake_up_process(dio->waiter);
319 spin_unlock_irqrestore(&dio->bio_lock, flags);
324 dio_bio_alloc(struct dio *dio, struct block_device *bdev,
325 sector_t first_sector, int nr_vecs)
329 bio = bio_alloc(GFP_KERNEL, nr_vecs);
334 bio->bi_sector = first_sector;
336 bio->bi_end_io = dio_bio_end_aio;
338 bio->bi_end_io = dio_bio_end_io;
345 * In the AIO read case we speculatively dirty the pages before starting IO.
346 * During IO completion, any of these pages which happen to have been written
347 * back will be redirtied by bio_check_pages_dirty().
349 * bios hold a dio reference between submit_bio and ->end_io.
351 static void dio_bio_submit(struct dio *dio)
353 struct bio *bio = dio->bio;
355 bio->bi_private = dio;
356 atomic_inc(&dio->refcount);
357 if (dio->is_async && dio->rw == READ)
358 bio_set_pages_dirty(bio);
359 submit_bio(dio->rw, bio);
366 * Release any resources in case of a failure
368 static void dio_cleanup(struct dio *dio)
370 while (dio_pages_present(dio))
371 page_cache_release(dio_get_page(dio));
374 static int wait_for_more_bios(struct dio *dio)
376 assert_spin_locked(&dio->bio_lock);
378 return (atomic_read(&dio->refcount) > 1) && (dio->bio_list == NULL);
382 * Wait for the next BIO to complete. Remove it and return it. NULL is
383 * returned once all BIOs have been completed. This must only be called once
384 * all bios have been issued so that dio->refcount can only decrease. This
385 * requires that that the caller hold a reference on the dio.
387 static struct bio *dio_await_one(struct dio *dio)
390 struct bio *bio = NULL;
392 spin_lock_irqsave(&dio->bio_lock, flags);
393 while (wait_for_more_bios(dio)) {
394 set_current_state(TASK_UNINTERRUPTIBLE);
395 if (wait_for_more_bios(dio)) {
396 dio->waiter = current;
397 spin_unlock_irqrestore(&dio->bio_lock, flags);
399 spin_lock_irqsave(&dio->bio_lock, flags);
402 set_current_state(TASK_RUNNING);
406 dio->bio_list = bio->bi_private;
408 spin_unlock_irqrestore(&dio->bio_lock, flags);
413 * Process one completed BIO. No locks are held.
415 static int dio_bio_complete(struct dio *dio, struct bio *bio)
417 const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
418 struct bio_vec *bvec = bio->bi_io_vec;
422 dio->io_error = -EIO;
424 if (dio->is_async && dio->rw == READ) {
425 bio_check_pages_dirty(bio); /* transfers ownership */
427 for (page_no = 0; page_no < bio->bi_vcnt; page_no++) {
428 struct page *page = bvec[page_no].bv_page;
430 if (dio->rw == READ && !PageCompound(page))
431 set_page_dirty_lock(page);
432 page_cache_release(page);
436 return uptodate ? 0 : -EIO;
440 * Wait on and process all in-flight BIOs. This must only be called once
441 * all bios have been issued so that the refcount can only decrease.
442 * This just waits for all bios to make it through dio_bio_complete. IO
443 * errors are propogated through dio->io_error and should be propogated via
446 static void dio_await_completion(struct dio *dio)
450 bio = dio_await_one(dio);
452 dio_bio_complete(dio, bio);
457 * A really large O_DIRECT read or write can generate a lot of BIOs. So
458 * to keep the memory consumption sane we periodically reap any completed BIOs
459 * during the BIO generation phase.
461 * This also helps to limit the peak amount of pinned userspace memory.
463 static int dio_bio_reap(struct dio *dio)
467 if (dio->reap_counter++ >= 64) {
468 while (dio->bio_list) {
473 spin_lock_irqsave(&dio->bio_lock, flags);
475 dio->bio_list = bio->bi_private;
476 spin_unlock_irqrestore(&dio->bio_lock, flags);
477 ret2 = dio_bio_complete(dio, bio);
481 dio->reap_counter = 0;
487 * Call into the fs to map some more disk blocks. We record the current number
488 * of available blocks at dio->blocks_available. These are in units of the
489 * fs blocksize, (1 << inode->i_blkbits).
491 * The fs is allowed to map lots of blocks at once. If it wants to do that,
492 * it uses the passed inode-relative block number as the file offset, as usual.
494 * get_block() is passed the number of i_blkbits-sized blocks which direct_io
495 * has remaining to do. The fs should not map more than this number of blocks.
497 * If the fs has mapped a lot of blocks, it should populate bh->b_size to
498 * indicate how much contiguous disk space has been made available at
501 * If *any* of the mapped blocks are new, then the fs must set buffer_new().
502 * This isn't very efficient...
504 * In the case of filesystem holes: the fs may return an arbitrarily-large
505 * hole by returning an appropriate value in b_size and by clearing
506 * buffer_mapped(). However the direct-io code will only process holes one
507 * block at a time - it will repeatedly call get_block() as it walks the hole.
509 static int get_more_blocks(struct dio *dio)
512 struct buffer_head *map_bh = &dio->map_bh;
513 sector_t fs_startblk; /* Into file, in filesystem-sized blocks */
514 unsigned long fs_count; /* Number of filesystem-sized blocks */
515 unsigned long dio_count;/* Number of dio_block-sized blocks */
516 unsigned long blkmask;
520 * If there was a memory error and we've overwritten all the
521 * mapped blocks then we can now return that memory error
523 ret = dio->page_errors;
525 BUG_ON(dio->block_in_file >= dio->final_block_in_request);
526 fs_startblk = dio->block_in_file >> dio->blkfactor;
527 dio_count = dio->final_block_in_request - dio->block_in_file;
528 fs_count = dio_count >> dio->blkfactor;
529 blkmask = (1 << dio->blkfactor) - 1;
530 if (dio_count & blkmask)
534 map_bh->b_size = fs_count << dio->inode->i_blkbits;
536 create = dio->rw & WRITE;
537 if (dio->lock_type == DIO_LOCKING) {
538 if (dio->block_in_file < (i_size_read(dio->inode) >>
541 } else if (dio->lock_type == DIO_NO_LOCKING) {
546 * For writes inside i_size we forbid block creations: only
547 * overwrites are permitted. We fall back to buffered writes
548 * at a higher level for inside-i_size block-instantiating
551 ret = (*dio->get_block)(dio->inode, fs_startblk,
558 * There is no bio. Make one now.
560 static int dio_new_bio(struct dio *dio, sector_t start_sector)
565 ret = dio_bio_reap(dio);
568 sector = start_sector << (dio->blkbits - 9);
569 nr_pages = min(dio->pages_in_io, bio_get_nr_vecs(dio->map_bh.b_bdev));
570 BUG_ON(nr_pages <= 0);
571 ret = dio_bio_alloc(dio, dio->map_bh.b_bdev, sector, nr_pages);
578 * Attempt to put the current chunk of 'cur_page' into the current BIO. If
579 * that was successful then update final_block_in_bio and take a ref against
580 * the just-added page.
582 * Return zero on success. Non-zero means the caller needs to start a new BIO.
584 static int dio_bio_add_page(struct dio *dio)
588 ret = bio_add_page(dio->bio, dio->cur_page,
589 dio->cur_page_len, dio->cur_page_offset);
590 if (ret == dio->cur_page_len) {
592 * Decrement count only, if we are done with this page
594 if ((dio->cur_page_len + dio->cur_page_offset) == PAGE_SIZE)
596 page_cache_get(dio->cur_page);
597 dio->final_block_in_bio = dio->cur_page_block +
598 (dio->cur_page_len >> dio->blkbits);
607 * Put cur_page under IO. The section of cur_page which is described by
608 * cur_page_offset,cur_page_len is put into a BIO. The section of cur_page
609 * starts on-disk at cur_page_block.
611 * We take a ref against the page here (on behalf of its presence in the bio).
613 * The caller of this function is responsible for removing cur_page from the
614 * dio, and for dropping the refcount which came from that presence.
616 static int dio_send_cur_page(struct dio *dio)
622 * See whether this new request is contiguous with the old
624 if (dio->final_block_in_bio != dio->cur_page_block)
627 * Submit now if the underlying fs is about to perform a
634 if (dio->bio == NULL) {
635 ret = dio_new_bio(dio, dio->cur_page_block);
640 if (dio_bio_add_page(dio) != 0) {
642 ret = dio_new_bio(dio, dio->cur_page_block);
644 ret = dio_bio_add_page(dio);
653 * An autonomous function to put a chunk of a page under deferred IO.
655 * The caller doesn't actually know (or care) whether this piece of page is in
656 * a BIO, or is under IO or whatever. We just take care of all possible
657 * situations here. The separation between the logic of do_direct_IO() and
658 * that of submit_page_section() is important for clarity. Please don't break.
660 * The chunk of page starts on-disk at blocknr.
662 * We perform deferred IO, by recording the last-submitted page inside our
663 * private part of the dio structure. If possible, we just expand the IO
664 * across that page here.
666 * If that doesn't work out then we put the old page into the bio and add this
667 * page to the dio instead.
670 submit_page_section(struct dio *dio, struct page *page,
671 unsigned offset, unsigned len, sector_t blocknr)
675 if (dio->rw & WRITE) {
677 * Read accounting is performed in submit_bio()
679 task_io_account_write(len);
683 * Can we just grow the current page's presence in the dio?
685 if ( (dio->cur_page == page) &&
686 (dio->cur_page_offset + dio->cur_page_len == offset) &&
687 (dio->cur_page_block +
688 (dio->cur_page_len >> dio->blkbits) == blocknr)) {
689 dio->cur_page_len += len;
692 * If dio->boundary then we want to schedule the IO now to
693 * avoid metadata seeks.
696 ret = dio_send_cur_page(dio);
697 page_cache_release(dio->cur_page);
698 dio->cur_page = NULL;
704 * If there's a deferred page already there then send it.
707 ret = dio_send_cur_page(dio);
708 page_cache_release(dio->cur_page);
709 dio->cur_page = NULL;
714 page_cache_get(page); /* It is in dio */
715 dio->cur_page = page;
716 dio->cur_page_offset = offset;
717 dio->cur_page_len = len;
718 dio->cur_page_block = blocknr;
724 * Clean any dirty buffers in the blockdev mapping which alias newly-created
725 * file blocks. Only called for S_ISREG files - blockdevs do not set
728 static void clean_blockdev_aliases(struct dio *dio)
733 nblocks = dio->map_bh.b_size >> dio->inode->i_blkbits;
735 for (i = 0; i < nblocks; i++) {
736 unmap_underlying_metadata(dio->map_bh.b_bdev,
737 dio->map_bh.b_blocknr + i);
742 * If we are not writing the entire block and get_block() allocated
743 * the block for us, we need to fill-in the unused portion of the
744 * block with zeros. This happens only if user-buffer, fileoffset or
745 * io length is not filesystem block-size multiple.
747 * `end' is zero if we're doing the start of the IO, 1 at the end of the
750 static void dio_zero_block(struct dio *dio, int end)
752 unsigned dio_blocks_per_fs_block;
753 unsigned this_chunk_blocks; /* In dio_blocks */
754 unsigned this_chunk_bytes;
757 dio->start_zero_done = 1;
758 if (!dio->blkfactor || !buffer_new(&dio->map_bh))
761 dio_blocks_per_fs_block = 1 << dio->blkfactor;
762 this_chunk_blocks = dio->block_in_file & (dio_blocks_per_fs_block - 1);
764 if (!this_chunk_blocks)
768 * We need to zero out part of an fs block. It is either at the
769 * beginning or the end of the fs block.
772 this_chunk_blocks = dio_blocks_per_fs_block - this_chunk_blocks;
774 this_chunk_bytes = this_chunk_blocks << dio->blkbits;
776 page = ZERO_PAGE(dio->curr_user_address);
777 if (submit_page_section(dio, page, 0, this_chunk_bytes,
778 dio->next_block_for_io))
781 dio->next_block_for_io += this_chunk_blocks;
785 * Walk the user pages, and the file, mapping blocks to disk and generating
786 * a sequence of (page,offset,len,block) mappings. These mappings are injected
787 * into submit_page_section(), which takes care of the next stage of submission
789 * Direct IO against a blockdev is different from a file. Because we can
790 * happily perform page-sized but 512-byte aligned IOs. It is important that
791 * blockdev IO be able to have fine alignment and large sizes.
793 * So what we do is to permit the ->get_block function to populate bh.b_size
794 * with the size of IO which is permitted at this offset and this i_blkbits.
796 * For best results, the blockdev should be set up with 512-byte i_blkbits and
797 * it should set b_size to PAGE_SIZE or more inside get_block(). This gives
798 * fine alignment but still allows this function to work in PAGE_SIZE units.
800 static int do_direct_IO(struct dio *dio)
802 const unsigned blkbits = dio->blkbits;
803 const unsigned blocks_per_page = PAGE_SIZE >> blkbits;
805 unsigned block_in_page;
806 struct buffer_head *map_bh = &dio->map_bh;
809 /* The I/O can start at any block offset within the first page */
810 block_in_page = dio->first_block_in_page;
812 while (dio->block_in_file < dio->final_block_in_request) {
813 page = dio_get_page(dio);
819 while (block_in_page < blocks_per_page) {
820 unsigned offset_in_page = block_in_page << blkbits;
821 unsigned this_chunk_bytes; /* # of bytes mapped */
822 unsigned this_chunk_blocks; /* # of blocks */
825 if (dio->blocks_available == 0) {
827 * Need to go and map some more disk
829 unsigned long blkmask;
830 unsigned long dio_remainder;
832 ret = get_more_blocks(dio);
834 page_cache_release(page);
837 if (!buffer_mapped(map_bh))
840 dio->blocks_available =
841 map_bh->b_size >> dio->blkbits;
842 dio->next_block_for_io =
843 map_bh->b_blocknr << dio->blkfactor;
844 if (buffer_new(map_bh))
845 clean_blockdev_aliases(dio);
850 blkmask = (1 << dio->blkfactor) - 1;
851 dio_remainder = (dio->block_in_file & blkmask);
854 * If we are at the start of IO and that IO
855 * starts partway into a fs-block,
856 * dio_remainder will be non-zero. If the IO
857 * is a read then we can simply advance the IO
858 * cursor to the first block which is to be
859 * read. But if the IO is a write and the
860 * block was newly allocated we cannot do that;
861 * the start of the fs block must be zeroed out
864 if (!buffer_new(map_bh))
865 dio->next_block_for_io += dio_remainder;
866 dio->blocks_available -= dio_remainder;
870 if (!buffer_mapped(map_bh)) {
872 loff_t i_size_aligned;
874 /* AKPM: eargh, -ENOTBLK is a hack */
875 if (dio->rw & WRITE) {
876 page_cache_release(page);
881 * Be sure to account for a partial block as the
882 * last block in the file
884 i_size_aligned = ALIGN(i_size_read(dio->inode),
886 if (dio->block_in_file >=
887 i_size_aligned >> blkbits) {
889 page_cache_release(page);
892 kaddr = kmap_atomic(page, KM_USER0);
893 memset(kaddr + (block_in_page << blkbits),
895 flush_dcache_page(page);
896 kunmap_atomic(kaddr, KM_USER0);
897 dio->block_in_file++;
903 * If we're performing IO which has an alignment which
904 * is finer than the underlying fs, go check to see if
905 * we must zero out the start of this block.
907 if (unlikely(dio->blkfactor && !dio->start_zero_done))
908 dio_zero_block(dio, 0);
911 * Work out, in this_chunk_blocks, how much disk we
912 * can add to this page
914 this_chunk_blocks = dio->blocks_available;
915 u = (PAGE_SIZE - offset_in_page) >> blkbits;
916 if (this_chunk_blocks > u)
917 this_chunk_blocks = u;
918 u = dio->final_block_in_request - dio->block_in_file;
919 if (this_chunk_blocks > u)
920 this_chunk_blocks = u;
921 this_chunk_bytes = this_chunk_blocks << blkbits;
922 BUG_ON(this_chunk_bytes == 0);
924 dio->boundary = buffer_boundary(map_bh);
925 ret = submit_page_section(dio, page, offset_in_page,
926 this_chunk_bytes, dio->next_block_for_io);
928 page_cache_release(page);
931 dio->next_block_for_io += this_chunk_blocks;
933 dio->block_in_file += this_chunk_blocks;
934 block_in_page += this_chunk_blocks;
935 dio->blocks_available -= this_chunk_blocks;
937 BUG_ON(dio->block_in_file > dio->final_block_in_request);
938 if (dio->block_in_file == dio->final_block_in_request)
942 /* Drop the ref which was taken in get_user_pages() */
943 page_cache_release(page);
951 * Releases both i_mutex and i_alloc_sem
954 direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode,
955 const struct iovec *iov, loff_t offset, unsigned long nr_segs,
956 unsigned blkbits, get_block_t get_block, dio_iodone_t end_io,
959 unsigned long user_addr;
968 dio->blkbits = blkbits;
969 dio->blkfactor = inode->i_blkbits - blkbits;
970 dio->start_zero_done = 0;
972 dio->block_in_file = offset >> blkbits;
973 dio->blocks_available = 0;
974 dio->cur_page = NULL;
977 dio->reap_counter = 0;
978 dio->get_block = get_block;
979 dio->end_io = end_io;
980 dio->map_bh.b_private = NULL;
981 dio->final_block_in_bio = -1;
982 dio->next_block_for_io = -1;
984 dio->page_errors = 0;
988 dio->i_size = i_size_read(inode);
990 atomic_set(&dio->refcount, 1);
991 spin_lock_init(&dio->bio_lock);
992 dio->bio_list = NULL;
996 * In case of non-aligned buffers, we may need 2 more
997 * pages since we need to zero out first and last block.
999 if (unlikely(dio->blkfactor))
1000 dio->pages_in_io = 2;
1002 dio->pages_in_io = 0;
1004 for (seg = 0; seg < nr_segs; seg++) {
1005 user_addr = (unsigned long)iov[seg].iov_base;
1007 ((user_addr+iov[seg].iov_len +PAGE_SIZE-1)/PAGE_SIZE
1008 - user_addr/PAGE_SIZE);
1011 for (seg = 0; seg < nr_segs; seg++) {
1012 user_addr = (unsigned long)iov[seg].iov_base;
1013 dio->size += bytes = iov[seg].iov_len;
1015 /* Index into the first page of the first block */
1016 dio->first_block_in_page = (user_addr & ~PAGE_MASK) >> blkbits;
1017 dio->final_block_in_request = dio->block_in_file +
1019 /* Page fetching state */
1024 dio->total_pages = 0;
1025 if (user_addr & (PAGE_SIZE-1)) {
1027 bytes -= PAGE_SIZE - (user_addr & (PAGE_SIZE - 1));
1029 dio->total_pages += (bytes + PAGE_SIZE - 1) / PAGE_SIZE;
1030 dio->curr_user_address = user_addr;
1032 ret = do_direct_IO(dio);
1034 dio->result += iov[seg].iov_len -
1035 ((dio->final_block_in_request - dio->block_in_file) <<
1042 } /* end iovec loop */
1044 if (ret == -ENOTBLK && (rw & WRITE)) {
1046 * The remaining part of the request will be
1047 * be handled by buffered I/O when we return
1052 * There may be some unwritten disk at the end of a part-written
1053 * fs-block-sized block. Go zero that now.
1055 dio_zero_block(dio, 1);
1057 if (dio->cur_page) {
1058 ret2 = dio_send_cur_page(dio);
1061 page_cache_release(dio->cur_page);
1062 dio->cur_page = NULL;
1065 dio_bio_submit(dio);
1067 /* All IO is now issued, send it on its way */
1068 blk_run_address_space(inode->i_mapping);
1071 * It is possible that, we return short IO due to end of file.
1072 * In that case, we need to release all the pages we got hold on.
1077 * All block lookups have been performed. For READ requests
1078 * we can let i_mutex go now that its achieved its purpose
1079 * of protecting us from looking up uninitialized blocks.
1081 if ((rw == READ) && (dio->lock_type == DIO_LOCKING))
1082 mutex_unlock(&dio->inode->i_mutex);
1085 * OK, all BIOs are submitted, so we can decrement bio_count to truly
1086 * reflect the number of to-be-processed BIOs.
1088 if (dio->is_async) {
1089 int should_wait = 0;
1091 if (dio->result < dio->size && (rw & WRITE)) {
1092 dio->waiter = current;
1099 dio_await_completion(dio);
1101 /* this can free the dio */
1102 if (atomic_dec_and_test(&dio->refcount))
1103 dio_complete_aio(dio);
1108 dio_await_completion(dio);
1110 ret = dio_complete(dio, offset, ret);
1112 /* We could have also come here on an AIO file extend */
1113 if (!is_sync_kiocb(iocb) && (rw & WRITE) &&
1114 ret >= 0 && dio->result == dio->size)
1116 * For AIO writes where we have completed the
1117 * i/o, we have to mark the the aio complete.
1119 aio_complete(iocb, ret, 0);
1121 if (atomic_dec_and_test(&dio->refcount))
1130 * This is a library function for use by filesystem drivers.
1131 * The locking rules are governed by the dio_lock_type parameter.
1133 * DIO_NO_LOCKING (no locking, for raw block device access)
1134 * For writes, i_mutex is not held on entry; it is never taken.
1136 * DIO_LOCKING (simple locking for regular files)
1137 * For writes we are called under i_mutex and return with i_mutex held, even
1138 * though it is internally dropped.
1139 * For reads, i_mutex is not held on entry, but it is taken and dropped before
1142 * DIO_OWN_LOCKING (filesystem provides synchronisation and handling of
1143 * uninitialised data, allowing parallel direct readers and writers)
1144 * For writes we are called without i_mutex, return without it, never touch it.
1145 * For reads we are called under i_mutex and return with i_mutex held, even
1146 * though it may be internally dropped.
1148 * Additional i_alloc_sem locking requirements described inline below.
1151 __blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
1152 struct block_device *bdev, const struct iovec *iov, loff_t offset,
1153 unsigned long nr_segs, get_block_t get_block, dio_iodone_t end_io,
1159 unsigned blkbits = inode->i_blkbits;
1160 unsigned bdev_blkbits = 0;
1161 unsigned blocksize_mask = (1 << blkbits) - 1;
1162 ssize_t retval = -EINVAL;
1163 loff_t end = offset;
1165 int release_i_mutex = 0;
1166 int acquire_i_mutex = 0;
1172 bdev_blkbits = blksize_bits(bdev_hardsect_size(bdev));
1174 if (offset & blocksize_mask) {
1176 blkbits = bdev_blkbits;
1177 blocksize_mask = (1 << blkbits) - 1;
1178 if (offset & blocksize_mask)
1182 /* Check the memory alignment. Blocks cannot straddle pages */
1183 for (seg = 0; seg < nr_segs; seg++) {
1184 addr = (unsigned long)iov[seg].iov_base;
1185 size = iov[seg].iov_len;
1187 if ((addr & blocksize_mask) || (size & blocksize_mask)) {
1189 blkbits = bdev_blkbits;
1190 blocksize_mask = (1 << blkbits) - 1;
1191 if ((addr & blocksize_mask) || (size & blocksize_mask))
1196 dio = kmalloc(sizeof(*dio), GFP_KERNEL);
1202 * For block device access DIO_NO_LOCKING is used,
1203 * neither readers nor writers do any locking at all
1204 * For regular files using DIO_LOCKING,
1205 * readers need to grab i_mutex and i_alloc_sem
1206 * writers need to grab i_alloc_sem only (i_mutex is already held)
1207 * For regular files using DIO_OWN_LOCKING,
1208 * neither readers nor writers take any locks here
1210 dio->lock_type = dio_lock_type;
1211 if (dio_lock_type != DIO_NO_LOCKING) {
1212 /* watch out for a 0 len io from a tricksy fs */
1213 if (rw == READ && end > offset) {
1214 struct address_space *mapping;
1216 mapping = iocb->ki_filp->f_mapping;
1217 if (dio_lock_type != DIO_OWN_LOCKING) {
1218 mutex_lock(&inode->i_mutex);
1219 release_i_mutex = 1;
1222 retval = filemap_write_and_wait_range(mapping, offset,
1229 if (dio_lock_type == DIO_OWN_LOCKING) {
1230 mutex_unlock(&inode->i_mutex);
1231 acquire_i_mutex = 1;
1235 if (dio_lock_type == DIO_LOCKING)
1236 /* lockdep: not the owner will release it */
1237 down_read_non_owner(&inode->i_alloc_sem);
1241 * For file extending writes updating i_size before data
1242 * writeouts complete can expose uninitialized blocks. So
1243 * even for AIO, we need to wait for i/o to complete before
1244 * returning in this case.
1246 dio->is_async = !is_sync_kiocb(iocb) && !((rw & WRITE) &&
1247 (end > i_size_read(inode)));
1249 retval = direct_io_worker(rw, iocb, inode, iov, offset,
1250 nr_segs, blkbits, get_block, end_io, dio);
1252 if (rw == READ && dio_lock_type == DIO_LOCKING)
1253 release_i_mutex = 0;
1256 if (release_i_mutex)
1257 mutex_unlock(&inode->i_mutex);
1258 else if (acquire_i_mutex)
1259 mutex_lock(&inode->i_mutex);
1262 EXPORT_SYMBOL(__blockdev_direct_IO);