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1// SPDX-License-Identifier: GPL-2.0-only2/*3 * fs/direct-io.c4 *5 * Copyright (C) 2002, Linus Torvalds.6 *7 * O_DIRECT8 *9 * 04Jul2002 Andrew Morton10 * Initial version11 * 11Sep2002 janetinc@us.ibm.com12 * added readv/writev support.13 * 29Oct2002 Andrew Morton14 * rewrote bio_add_page() support.15 * 30Oct2002 pbadari@us.ibm.com16 * added support for non-aligned IO.17 * 06Nov2002 pbadari@us.ibm.com18 * added asynchronous IO support.19 * 21Jul2003 nathans@sgi.com20 * added IO completion notifier.21 */22 23#include <linux/kernel.h>24#include <linux/module.h>25#include <linux/types.h>26#include <linux/fs.h>27#include <linux/mm.h>28#include <linux/slab.h>29#include <linux/highmem.h>30#include <linux/pagemap.h>31#include <linux/task_io_accounting_ops.h>32#include <linux/bio.h>33#include <linux/wait.h>34#include <linux/err.h>35#include <linux/blkdev.h>36#include <linux/buffer_head.h>37#include <linux/rwsem.h>38#include <linux/uio.h>39#include <linux/atomic.h>40 41#include "internal.h"42 43/*44 * How many user pages to map in one call to iov_iter_extract_pages(). This45 * determines the size of a structure in the slab cache46 */47#define DIO_PAGES 6448 49/*50 * Flags for dio_complete()51 */52#define DIO_COMPLETE_ASYNC 0x01 /* This is async IO */53#define DIO_COMPLETE_INVALIDATE 0x02 /* Can invalidate pages */54 55/*56 * This code generally works in units of "dio_blocks". A dio_block is57 * somewhere between the hard sector size and the filesystem block size. it58 * is determined on a per-invocation basis. When talking to the filesystem59 * we need to convert dio_blocks to fs_blocks by scaling the dio_block quantity60 * down by dio->blkfactor. Similarly, fs-blocksize quantities are converted61 * to bio_block quantities by shifting left by blkfactor.62 *63 * If blkfactor is zero then the user's request was aligned to the filesystem's64 * blocksize.65 */66 67/* dio_state only used in the submission path */68 69struct dio_submit {70 struct bio *bio; /* bio under assembly */71 unsigned blkbits; /* doesn't change */72 unsigned blkfactor; /* When we're using an alignment which73 is finer than the filesystem's soft74 blocksize, this specifies how much75 finer. blkfactor=2 means 1/4-block76 alignment. Does not change */77 unsigned start_zero_done; /* flag: sub-blocksize zeroing has78 been performed at the start of a79 write */80 int pages_in_io; /* approximate total IO pages */81 sector_t block_in_file; /* Current offset into the underlying82 file in dio_block units. */83 unsigned blocks_available; /* At block_in_file. changes */84 int reap_counter; /* rate limit reaping */85 sector_t final_block_in_request;/* doesn't change */86 int boundary; /* prev block is at a boundary */87 get_block_t *get_block; /* block mapping function */88 89 loff_t logical_offset_in_bio; /* current first logical block in bio */90 sector_t final_block_in_bio; /* current final block in bio + 1 */91 sector_t next_block_for_io; /* next block to be put under IO,92 in dio_blocks units */93 94 /*95 * Deferred addition of a page to the dio. These variables are96 * private to dio_send_cur_page(), submit_page_section() and97 * dio_bio_add_page().98 */99 struct page *cur_page; /* The page */100 unsigned cur_page_offset; /* Offset into it, in bytes */101 unsigned cur_page_len; /* Nr of bytes at cur_page_offset */102 sector_t cur_page_block; /* Where it starts */103 loff_t cur_page_fs_offset; /* Offset in file */104 105 struct iov_iter *iter;106 /*107 * Page queue. These variables belong to dio_refill_pages() and108 * dio_get_page().109 */110 unsigned head; /* next page to process */111 unsigned tail; /* last valid page + 1 */112 size_t from, to;113};114 115/* dio_state communicated between submission path and end_io */116struct dio {117 int flags; /* doesn't change */118 blk_opf_t opf; /* request operation type and flags */119 struct gendisk *bio_disk;120 struct inode *inode;121 loff_t i_size; /* i_size when submitted */122 dio_iodone_t *end_io; /* IO completion function */123 bool is_pinned; /* T if we have pins on the pages */124 125 void *private; /* copy from map_bh.b_private */126 127 /* BIO completion state */128 spinlock_t bio_lock; /* protects BIO fields below */129 int page_errors; /* err from iov_iter_extract_pages() */130 int is_async; /* is IO async ? */131 bool defer_completion; /* defer AIO completion to workqueue? */132 bool should_dirty; /* if pages should be dirtied */133 int io_error; /* IO error in completion path */134 unsigned long refcount; /* direct_io_worker() and bios */135 struct bio *bio_list; /* singly linked via bi_private */136 struct task_struct *waiter; /* waiting task (NULL if none) */137 138 /* AIO related stuff */139 struct kiocb *iocb; /* kiocb */140 ssize_t result; /* IO result */141 142 /*143 * pages[] (and any fields placed after it) are not zeroed out at144 * allocation time. Don't add new fields after pages[] unless you145 * wish that they not be zeroed.146 */147 union {148 struct page *pages[DIO_PAGES]; /* page buffer */149 struct work_struct complete_work;/* deferred AIO completion */150 };151} ____cacheline_aligned_in_smp;152 153static struct kmem_cache *dio_cache __ro_after_init;154 155/*156 * How many pages are in the queue?157 */158static inline unsigned dio_pages_present(struct dio_submit *sdio)159{160 return sdio->tail - sdio->head;161}162 163/*164 * Go grab and pin some userspace pages. Typically we'll get 64 at a time.165 */166static inline int dio_refill_pages(struct dio *dio, struct dio_submit *sdio)167{168 struct page **pages = dio->pages;169 const enum req_op dio_op = dio->opf & REQ_OP_MASK;170 ssize_t ret;171 172 ret = iov_iter_extract_pages(sdio->iter, &pages, LONG_MAX,173 DIO_PAGES, 0, &sdio->from);174 175 if (ret < 0 && sdio->blocks_available && dio_op == REQ_OP_WRITE) {176 /*177 * A memory fault, but the filesystem has some outstanding178 * mapped blocks. We need to use those blocks up to avoid179 * leaking stale data in the file.180 */181 if (dio->page_errors == 0)182 dio->page_errors = ret;183 dio->pages[0] = ZERO_PAGE(0);184 sdio->head = 0;185 sdio->tail = 1;186 sdio->from = 0;187 sdio->to = PAGE_SIZE;188 return 0;189 }190 191 if (ret >= 0) {192 ret += sdio->from;193 sdio->head = 0;194 sdio->tail = (ret + PAGE_SIZE - 1) / PAGE_SIZE;195 sdio->to = ((ret - 1) & (PAGE_SIZE - 1)) + 1;196 return 0;197 }198 return ret; 199}200 201/*202 * Get another userspace page. Returns an ERR_PTR on error. Pages are203 * buffered inside the dio so that we can call iov_iter_extract_pages()204 * against a decent number of pages, less frequently. To provide nicer use of205 * the L1 cache.206 */207static inline struct page *dio_get_page(struct dio *dio,208 struct dio_submit *sdio)209{210 if (dio_pages_present(sdio) == 0) {211 int ret;212 213 ret = dio_refill_pages(dio, sdio);214 if (ret)215 return ERR_PTR(ret);216 BUG_ON(dio_pages_present(sdio) == 0);217 }218 return dio->pages[sdio->head];219}220 221static void dio_pin_page(struct dio *dio, struct page *page)222{223 if (dio->is_pinned)224 folio_add_pin(page_folio(page));225}226 227static void dio_unpin_page(struct dio *dio, struct page *page)228{229 if (dio->is_pinned)230 unpin_user_page(page);231}232 233/*234 * dio_complete() - called when all DIO BIO I/O has been completed235 *236 * This drops i_dio_count, lets interested parties know that a DIO operation237 * has completed, and calculates the resulting return code for the operation.238 *239 * It lets the filesystem know if it registered an interest earlier via240 * get_block. Pass the private field of the map buffer_head so that241 * filesystems can use it to hold additional state between get_block calls and242 * dio_complete.243 */244static ssize_t dio_complete(struct dio *dio, ssize_t ret, unsigned int flags)245{246 const enum req_op dio_op = dio->opf & REQ_OP_MASK;247 loff_t offset = dio->iocb->ki_pos;248 ssize_t transferred = 0;249 int err;250 251 /*252 * AIO submission can race with bio completion to get here while253 * expecting to have the last io completed by bio completion.254 * In that case -EIOCBQUEUED is in fact not an error we want255 * to preserve through this call.256 */257 if (ret == -EIOCBQUEUED)258 ret = 0;259 260 if (dio->result) {261 transferred = dio->result;262 263 /* Check for short read case */264 if (dio_op == REQ_OP_READ &&265 ((offset + transferred) > dio->i_size))266 transferred = dio->i_size - offset;267 /* ignore EFAULT if some IO has been done */268 if (unlikely(ret == -EFAULT) && transferred)269 ret = 0;270 }271 272 if (ret == 0)273 ret = dio->page_errors;274 if (ret == 0)275 ret = dio->io_error;276 if (ret == 0)277 ret = transferred;278 279 if (dio->end_io) {280 // XXX: ki_pos??281 err = dio->end_io(dio->iocb, offset, ret, dio->private);282 if (err)283 ret = err;284 }285 286 /*287 * Try again to invalidate clean pages which might have been cached by288 * non-direct readahead, or faulted in by get_user_pages() if the source289 * of the write was an mmap'ed region of the file we're writing. Either290 * one is a pretty crazy thing to do, so we don't support it 100%. If291 * this invalidation fails, tough, the write still worked...292 *293 * And this page cache invalidation has to be after dio->end_io(), as294 * some filesystems convert unwritten extents to real allocations in295 * end_io() when necessary, otherwise a racing buffer read would cache296 * zeros from unwritten extents.297 */298 if (flags & DIO_COMPLETE_INVALIDATE &&299 ret > 0 && dio_op == REQ_OP_WRITE)300 kiocb_invalidate_post_direct_write(dio->iocb, ret);301 302 inode_dio_end(dio->inode);303 304 if (flags & DIO_COMPLETE_ASYNC) {305 /*306 * generic_write_sync expects ki_pos to have been updated307 * already, but the submission path only does this for308 * synchronous I/O.309 */310 dio->iocb->ki_pos += transferred;311 312 if (ret > 0 && dio_op == REQ_OP_WRITE)313 ret = generic_write_sync(dio->iocb, ret);314 dio->iocb->ki_complete(dio->iocb, ret);315 }316 317 kmem_cache_free(dio_cache, dio);318 return ret;319}320 321static void dio_aio_complete_work(struct work_struct *work)322{323 struct dio *dio = container_of(work, struct dio, complete_work);324 325 dio_complete(dio, 0, DIO_COMPLETE_ASYNC | DIO_COMPLETE_INVALIDATE);326}327 328static blk_status_t dio_bio_complete(struct dio *dio, struct bio *bio);329 330/*331 * Asynchronous IO callback. 332 */333static void dio_bio_end_aio(struct bio *bio)334{335 struct dio *dio = bio->bi_private;336 const enum req_op dio_op = dio->opf & REQ_OP_MASK;337 unsigned long remaining;338 unsigned long flags;339 bool defer_completion = false;340 341 /* cleanup the bio */342 dio_bio_complete(dio, bio);343 344 spin_lock_irqsave(&dio->bio_lock, flags);345 remaining = --dio->refcount;346 if (remaining == 1 && dio->waiter)347 wake_up_process(dio->waiter);348 spin_unlock_irqrestore(&dio->bio_lock, flags);349 350 if (remaining == 0) {351 /*352 * Defer completion when defer_completion is set or353 * when the inode has pages mapped and this is AIO write.354 * We need to invalidate those pages because there is a355 * chance they contain stale data in the case buffered IO356 * went in between AIO submission and completion into the357 * same region.358 */359 if (dio->result)360 defer_completion = dio->defer_completion ||361 (dio_op == REQ_OP_WRITE &&362 dio->inode->i_mapping->nrpages);363 if (defer_completion) {364 INIT_WORK(&dio->complete_work, dio_aio_complete_work);365 queue_work(dio->inode->i_sb->s_dio_done_wq,366 &dio->complete_work);367 } else {368 dio_complete(dio, 0, DIO_COMPLETE_ASYNC);369 }370 }371}372 373/*374 * The BIO completion handler simply queues the BIO up for the process-context375 * handler.376 *377 * During I/O bi_private points at the dio. After I/O, bi_private is used to378 * implement a singly-linked list of completed BIOs, at dio->bio_list.379 */380static void dio_bio_end_io(struct bio *bio)381{382 struct dio *dio = bio->bi_private;383 unsigned long flags;384 385 spin_lock_irqsave(&dio->bio_lock, flags);386 bio->bi_private = dio->bio_list;387 dio->bio_list = bio;388 if (--dio->refcount == 1 && dio->waiter)389 wake_up_process(dio->waiter);390 spin_unlock_irqrestore(&dio->bio_lock, flags);391}392 393static inline void394dio_bio_alloc(struct dio *dio, struct dio_submit *sdio,395 struct block_device *bdev,396 sector_t first_sector, int nr_vecs)397{398 struct bio *bio;399 400 /*401 * bio_alloc() is guaranteed to return a bio when allowed to sleep and402 * we request a valid number of vectors.403 */404 bio = bio_alloc(bdev, nr_vecs, dio->opf, GFP_KERNEL);405 bio->bi_iter.bi_sector = first_sector;406 if (dio->is_async)407 bio->bi_end_io = dio_bio_end_aio;408 else409 bio->bi_end_io = dio_bio_end_io;410 if (dio->is_pinned)411 bio_set_flag(bio, BIO_PAGE_PINNED);412 bio->bi_write_hint = file_inode(dio->iocb->ki_filp)->i_write_hint;413 414 sdio->bio = bio;415 sdio->logical_offset_in_bio = sdio->cur_page_fs_offset;416}417 418/*419 * In the AIO read case we speculatively dirty the pages before starting IO.420 * During IO completion, any of these pages which happen to have been written421 * back will be redirtied by bio_check_pages_dirty().422 *423 * bios hold a dio reference between submit_bio and ->end_io.424 */425static inline void dio_bio_submit(struct dio *dio, struct dio_submit *sdio)426{427 const enum req_op dio_op = dio->opf & REQ_OP_MASK;428 struct bio *bio = sdio->bio;429 unsigned long flags;430 431 bio->bi_private = dio;432 433 spin_lock_irqsave(&dio->bio_lock, flags);434 dio->refcount++;435 spin_unlock_irqrestore(&dio->bio_lock, flags);436 437 if (dio->is_async && dio_op == REQ_OP_READ && dio->should_dirty)438 bio_set_pages_dirty(bio);439 440 dio->bio_disk = bio->bi_bdev->bd_disk;441 442 submit_bio(bio);443 444 sdio->bio = NULL;445 sdio->boundary = 0;446 sdio->logical_offset_in_bio = 0;447}448 449/*450 * Release any resources in case of a failure451 */452static inline void dio_cleanup(struct dio *dio, struct dio_submit *sdio)453{454 if (dio->is_pinned)455 unpin_user_pages(dio->pages + sdio->head,456 sdio->tail - sdio->head);457 sdio->head = sdio->tail;458}459 460/*461 * Wait for the next BIO to complete. Remove it and return it. NULL is462 * returned once all BIOs have been completed. This must only be called once463 * all bios have been issued so that dio->refcount can only decrease. This464 * requires that the caller hold a reference on the dio.465 */466static struct bio *dio_await_one(struct dio *dio)467{468 unsigned long flags;469 struct bio *bio = NULL;470 471 spin_lock_irqsave(&dio->bio_lock, flags);472 473 /*474 * Wait as long as the list is empty and there are bios in flight. bio475 * completion drops the count, maybe adds to the list, and wakes while476 * holding the bio_lock so we don't need set_current_state()'s barrier477 * and can call it after testing our condition.478 */479 while (dio->refcount > 1 && dio->bio_list == NULL) {480 __set_current_state(TASK_UNINTERRUPTIBLE);481 dio->waiter = current;482 spin_unlock_irqrestore(&dio->bio_lock, flags);483 blk_io_schedule();484 /* wake up sets us TASK_RUNNING */485 spin_lock_irqsave(&dio->bio_lock, flags);486 dio->waiter = NULL;487 }488 if (dio->bio_list) {489 bio = dio->bio_list;490 dio->bio_list = bio->bi_private;491 }492 spin_unlock_irqrestore(&dio->bio_lock, flags);493 return bio;494}495 496/*497 * Process one completed BIO. No locks are held.498 */499static blk_status_t dio_bio_complete(struct dio *dio, struct bio *bio)500{501 blk_status_t err = bio->bi_status;502 const enum req_op dio_op = dio->opf & REQ_OP_MASK;503 bool should_dirty = dio_op == REQ_OP_READ && dio->should_dirty;504 505 if (err) {506 if (err == BLK_STS_AGAIN && (bio->bi_opf & REQ_NOWAIT))507 dio->io_error = -EAGAIN;508 else509 dio->io_error = -EIO;510 }511 512 if (dio->is_async && should_dirty) {513 bio_check_pages_dirty(bio); /* transfers ownership */514 } else {515 bio_release_pages(bio, should_dirty);516 bio_put(bio);517 }518 return err;519}520 521/*522 * Wait on and process all in-flight BIOs. This must only be called once523 * all bios have been issued so that the refcount can only decrease.524 * This just waits for all bios to make it through dio_bio_complete. IO525 * errors are propagated through dio->io_error and should be propagated via526 * dio_complete().527 */528static void dio_await_completion(struct dio *dio)529{530 struct bio *bio;531 do {532 bio = dio_await_one(dio);533 if (bio)534 dio_bio_complete(dio, bio);535 } while (bio);536}537 538/*539 * A really large O_DIRECT read or write can generate a lot of BIOs. So540 * to keep the memory consumption sane we periodically reap any completed BIOs541 * during the BIO generation phase.542 *543 * This also helps to limit the peak amount of pinned userspace memory.544 */545static inline int dio_bio_reap(struct dio *dio, struct dio_submit *sdio)546{547 int ret = 0;548 549 if (sdio->reap_counter++ >= 64) {550 while (dio->bio_list) {551 unsigned long flags;552 struct bio *bio;553 int ret2;554 555 spin_lock_irqsave(&dio->bio_lock, flags);556 bio = dio->bio_list;557 dio->bio_list = bio->bi_private;558 spin_unlock_irqrestore(&dio->bio_lock, flags);559 ret2 = blk_status_to_errno(dio_bio_complete(dio, bio));560 if (ret == 0)561 ret = ret2;562 }563 sdio->reap_counter = 0;564 }565 return ret;566}567 568static int dio_set_defer_completion(struct dio *dio)569{570 struct super_block *sb = dio->inode->i_sb;571 572 if (dio->defer_completion)573 return 0;574 dio->defer_completion = true;575 if (!sb->s_dio_done_wq)576 return sb_init_dio_done_wq(sb);577 return 0;578}579 580/*581 * Call into the fs to map some more disk blocks. We record the current number582 * of available blocks at sdio->blocks_available. These are in units of the583 * fs blocksize, i_blocksize(inode).584 *585 * The fs is allowed to map lots of blocks at once. If it wants to do that,586 * it uses the passed inode-relative block number as the file offset, as usual.587 *588 * get_block() is passed the number of i_blkbits-sized blocks which direct_io589 * has remaining to do. The fs should not map more than this number of blocks.590 *591 * If the fs has mapped a lot of blocks, it should populate bh->b_size to592 * indicate how much contiguous disk space has been made available at593 * bh->b_blocknr.594 *595 * If *any* of the mapped blocks are new, then the fs must set buffer_new().596 * This isn't very efficient...597 *598 * In the case of filesystem holes: the fs may return an arbitrarily-large599 * hole by returning an appropriate value in b_size and by clearing600 * buffer_mapped(). However the direct-io code will only process holes one601 * block at a time - it will repeatedly call get_block() as it walks the hole.602 */603static int get_more_blocks(struct dio *dio, struct dio_submit *sdio,604 struct buffer_head *map_bh)605{606 const enum req_op dio_op = dio->opf & REQ_OP_MASK;607 int ret;608 sector_t fs_startblk; /* Into file, in filesystem-sized blocks */609 sector_t fs_endblk; /* Into file, in filesystem-sized blocks */610 unsigned long fs_count; /* Number of filesystem-sized blocks */611 int create;612 unsigned int i_blkbits = sdio->blkbits + sdio->blkfactor;613 loff_t i_size;614 615 /*616 * If there was a memory error and we've overwritten all the617 * mapped blocks then we can now return that memory error618 */619 ret = dio->page_errors;620 if (ret == 0) {621 BUG_ON(sdio->block_in_file >= sdio->final_block_in_request);622 fs_startblk = sdio->block_in_file >> sdio->blkfactor;623 fs_endblk = (sdio->final_block_in_request - 1) >>624 sdio->blkfactor;625 fs_count = fs_endblk - fs_startblk + 1;626 627 map_bh->b_state = 0;628 map_bh->b_size = fs_count << i_blkbits;629 630 /*631 * For writes that could fill holes inside i_size on a632 * DIO_SKIP_HOLES filesystem we forbid block creations: only633 * overwrites are permitted. We will return early to the caller634 * once we see an unmapped buffer head returned, and the caller635 * will fall back to buffered I/O.636 *637 * Otherwise the decision is left to the get_blocks method,638 * which may decide to handle it or also return an unmapped639 * buffer head.640 */641 create = dio_op == REQ_OP_WRITE;642 if (dio->flags & DIO_SKIP_HOLES) {643 i_size = i_size_read(dio->inode);644 if (i_size && fs_startblk <= (i_size - 1) >> i_blkbits)645 create = 0;646 }647 648 ret = (*sdio->get_block)(dio->inode, fs_startblk,649 map_bh, create);650 651 /* Store for completion */652 dio->private = map_bh->b_private;653 654 if (ret == 0 && buffer_defer_completion(map_bh))655 ret = dio_set_defer_completion(dio);656 }657 return ret;658}659 660/*661 * There is no bio. Make one now.662 */663static inline int dio_new_bio(struct dio *dio, struct dio_submit *sdio,664 sector_t start_sector, struct buffer_head *map_bh)665{666 sector_t sector;667 int ret, nr_pages;668 669 ret = dio_bio_reap(dio, sdio);670 if (ret)671 goto out;672 sector = start_sector << (sdio->blkbits - 9);673 nr_pages = bio_max_segs(sdio->pages_in_io);674 BUG_ON(nr_pages <= 0);675 dio_bio_alloc(dio, sdio, map_bh->b_bdev, sector, nr_pages);676 sdio->boundary = 0;677out:678 return ret;679}680 681/*682 * Attempt to put the current chunk of 'cur_page' into the current BIO. If683 * that was successful then update final_block_in_bio and take a ref against684 * the just-added page.685 *686 * Return zero on success. Non-zero means the caller needs to start a new BIO.687 */688static inline int dio_bio_add_page(struct dio *dio, struct dio_submit *sdio)689{690 int ret;691 692 ret = bio_add_page(sdio->bio, sdio->cur_page,693 sdio->cur_page_len, sdio->cur_page_offset);694 if (ret == sdio->cur_page_len) {695 /*696 * Decrement count only, if we are done with this page697 */698 if ((sdio->cur_page_len + sdio->cur_page_offset) == PAGE_SIZE)699 sdio->pages_in_io--;700 dio_pin_page(dio, sdio->cur_page);701 sdio->final_block_in_bio = sdio->cur_page_block +702 (sdio->cur_page_len >> sdio->blkbits);703 ret = 0;704 } else {705 ret = 1;706 }707 return ret;708}709 710/*711 * Put cur_page under IO. The section of cur_page which is described by712 * cur_page_offset,cur_page_len is put into a BIO. The section of cur_page713 * starts on-disk at cur_page_block.714 *715 * We take a ref against the page here (on behalf of its presence in the bio).716 *717 * The caller of this function is responsible for removing cur_page from the718 * dio, and for dropping the refcount which came from that presence.719 */720static inline int dio_send_cur_page(struct dio *dio, struct dio_submit *sdio,721 struct buffer_head *map_bh)722{723 int ret = 0;724 725 if (sdio->bio) {726 loff_t cur_offset = sdio->cur_page_fs_offset;727 loff_t bio_next_offset = sdio->logical_offset_in_bio +728 sdio->bio->bi_iter.bi_size;729 730 /*731 * See whether this new request is contiguous with the old.732 *733 * Btrfs cannot handle having logically non-contiguous requests734 * submitted. For example if you have735 *736 * Logical: [0-4095][HOLE][8192-12287]737 * Physical: [0-4095] [4096-8191]738 *739 * We cannot submit those pages together as one BIO. So if our740 * current logical offset in the file does not equal what would741 * be the next logical offset in the bio, submit the bio we742 * have.743 */744 if (sdio->final_block_in_bio != sdio->cur_page_block ||745 cur_offset != bio_next_offset)746 dio_bio_submit(dio, sdio);747 }748 749 if (sdio->bio == NULL) {750 ret = dio_new_bio(dio, sdio, sdio->cur_page_block, map_bh);751 if (ret)752 goto out;753 }754 755 if (dio_bio_add_page(dio, sdio) != 0) {756 dio_bio_submit(dio, sdio);757 ret = dio_new_bio(dio, sdio, sdio->cur_page_block, map_bh);758 if (ret == 0) {759 ret = dio_bio_add_page(dio, sdio);760 BUG_ON(ret != 0);761 }762 }763out:764 return ret;765}766 767/*768 * An autonomous function to put a chunk of a page under deferred IO.769 *770 * The caller doesn't actually know (or care) whether this piece of page is in771 * a BIO, or is under IO or whatever. We just take care of all possible 772 * situations here. The separation between the logic of do_direct_IO() and773 * that of submit_page_section() is important for clarity. Please don't break.774 *775 * The chunk of page starts on-disk at blocknr.776 *777 * We perform deferred IO, by recording the last-submitted page inside our778 * private part of the dio structure. If possible, we just expand the IO779 * across that page here.780 *781 * If that doesn't work out then we put the old page into the bio and add this782 * page to the dio instead.783 */784static inline int785submit_page_section(struct dio *dio, struct dio_submit *sdio, struct page *page,786 unsigned offset, unsigned len, sector_t blocknr,787 struct buffer_head *map_bh)788{789 const enum req_op dio_op = dio->opf & REQ_OP_MASK;790 int ret = 0;791 int boundary = sdio->boundary; /* dio_send_cur_page may clear it */792 793 if (dio_op == REQ_OP_WRITE) {794 /*795 * Read accounting is performed in submit_bio()796 */797 task_io_account_write(len);798 }799 800 /*801 * Can we just grow the current page's presence in the dio?802 */803 if (sdio->cur_page == page &&804 sdio->cur_page_offset + sdio->cur_page_len == offset &&805 sdio->cur_page_block +806 (sdio->cur_page_len >> sdio->blkbits) == blocknr) {807 sdio->cur_page_len += len;808 goto out;809 }810 811 /*812 * If there's a deferred page already there then send it.813 */814 if (sdio->cur_page) {815 ret = dio_send_cur_page(dio, sdio, map_bh);816 dio_unpin_page(dio, sdio->cur_page);817 sdio->cur_page = NULL;818 if (ret)819 return ret;820 }821 822 dio_pin_page(dio, page); /* It is in dio */823 sdio->cur_page = page;824 sdio->cur_page_offset = offset;825 sdio->cur_page_len = len;826 sdio->cur_page_block = blocknr;827 sdio->cur_page_fs_offset = sdio->block_in_file << sdio->blkbits;828out:829 /*830 * If boundary then we want to schedule the IO now to831 * avoid metadata seeks.832 */833 if (boundary) {834 ret = dio_send_cur_page(dio, sdio, map_bh);835 if (sdio->bio)836 dio_bio_submit(dio, sdio);837 dio_unpin_page(dio, sdio->cur_page);838 sdio->cur_page = NULL;839 }840 return ret;841}842 843/*844 * If we are not writing the entire block and get_block() allocated845 * the block for us, we need to fill-in the unused portion of the846 * block with zeros. This happens only if user-buffer, fileoffset or847 * io length is not filesystem block-size multiple.848 *849 * `end' is zero if we're doing the start of the IO, 1 at the end of the850 * IO.851 */852static inline void dio_zero_block(struct dio *dio, struct dio_submit *sdio,853 int end, struct buffer_head *map_bh)854{855 unsigned dio_blocks_per_fs_block;856 unsigned this_chunk_blocks; /* In dio_blocks */857 unsigned this_chunk_bytes;858 struct page *page;859 860 sdio->start_zero_done = 1;861 if (!sdio->blkfactor || !buffer_new(map_bh))862 return;863 864 dio_blocks_per_fs_block = 1 << sdio->blkfactor;865 this_chunk_blocks = sdio->block_in_file & (dio_blocks_per_fs_block - 1);866 867 if (!this_chunk_blocks)868 return;869 870 /*871 * We need to zero out part of an fs block. It is either at the872 * beginning or the end of the fs block.873 */874 if (end) 875 this_chunk_blocks = dio_blocks_per_fs_block - this_chunk_blocks;876 877 this_chunk_bytes = this_chunk_blocks << sdio->blkbits;878 879 page = ZERO_PAGE(0);880 if (submit_page_section(dio, sdio, page, 0, this_chunk_bytes,881 sdio->next_block_for_io, map_bh))882 return;883 884 sdio->next_block_for_io += this_chunk_blocks;885}886 887/*888 * Walk the user pages, and the file, mapping blocks to disk and generating889 * a sequence of (page,offset,len,block) mappings. These mappings are injected890 * into submit_page_section(), which takes care of the next stage of submission891 *892 * Direct IO against a blockdev is different from a file. Because we can893 * happily perform page-sized but 512-byte aligned IOs. It is important that894 * blockdev IO be able to have fine alignment and large sizes.895 *896 * So what we do is to permit the ->get_block function to populate bh.b_size897 * with the size of IO which is permitted at this offset and this i_blkbits.898 *899 * For best results, the blockdev should be set up with 512-byte i_blkbits and900 * it should set b_size to PAGE_SIZE or more inside get_block(). This gives901 * fine alignment but still allows this function to work in PAGE_SIZE units.902 */903static int do_direct_IO(struct dio *dio, struct dio_submit *sdio,904 struct buffer_head *map_bh)905{906 const enum req_op dio_op = dio->opf & REQ_OP_MASK;907 const unsigned blkbits = sdio->blkbits;908 const unsigned i_blkbits = blkbits + sdio->blkfactor;909 int ret = 0;910 911 while (sdio->block_in_file < sdio->final_block_in_request) {912 struct page *page;913 size_t from, to;914 915 page = dio_get_page(dio, sdio);916 if (IS_ERR(page)) {917 ret = PTR_ERR(page);918 goto out;919 }920 from = sdio->head ? 0 : sdio->from;921 to = (sdio->head == sdio->tail - 1) ? sdio->to : PAGE_SIZE;922 sdio->head++;923 924 while (from < to) {925 unsigned this_chunk_bytes; /* # of bytes mapped */926 unsigned this_chunk_blocks; /* # of blocks */927 unsigned u;928 929 if (sdio->blocks_available == 0) {930 /*931 * Need to go and map some more disk932 */933 unsigned long blkmask;934 unsigned long dio_remainder;935 936 ret = get_more_blocks(dio, sdio, map_bh);937 if (ret) {938 dio_unpin_page(dio, page);939 goto out;940 }941 if (!buffer_mapped(map_bh))942 goto do_holes;943 944 sdio->blocks_available =945 map_bh->b_size >> blkbits;946 sdio->next_block_for_io =947 map_bh->b_blocknr << sdio->blkfactor;948 if (buffer_new(map_bh)) {949 clean_bdev_aliases(950 map_bh->b_bdev,951 map_bh->b_blocknr,952 map_bh->b_size >> i_blkbits);953 }954 955 if (!sdio->blkfactor)956 goto do_holes;957 958 blkmask = (1 << sdio->blkfactor) - 1;959 dio_remainder = (sdio->block_in_file & blkmask);960 961 /*962 * If we are at the start of IO and that IO963 * starts partway into a fs-block,964 * dio_remainder will be non-zero. If the IO965 * is a read then we can simply advance the IO966 * cursor to the first block which is to be967 * read. But if the IO is a write and the968 * block was newly allocated we cannot do that;969 * the start of the fs block must be zeroed out970 * on-disk971 */972 if (!buffer_new(map_bh))973 sdio->next_block_for_io += dio_remainder;974 sdio->blocks_available -= dio_remainder;975 }976do_holes:977 /* Handle holes */978 if (!buffer_mapped(map_bh)) {979 loff_t i_size_aligned;980 981 /* AKPM: eargh, -ENOTBLK is a hack */982 if (dio_op == REQ_OP_WRITE) {983 dio_unpin_page(dio, page);984 return -ENOTBLK;985 }986 987 /*988 * Be sure to account for a partial block as the989 * last block in the file990 */991 i_size_aligned = ALIGN(i_size_read(dio->inode),992 1 << blkbits);993 if (sdio->block_in_file >=994 i_size_aligned >> blkbits) {995 /* We hit eof */996 dio_unpin_page(dio, page);997 goto out;998 }999 zero_user(page, from, 1 << blkbits);1000 sdio->block_in_file++;1001 from += 1 << blkbits;1002 dio->result += 1 << blkbits;1003 goto next_block;1004 }1005 1006 /*1007 * If we're performing IO which has an alignment which1008 * is finer than the underlying fs, go check to see if1009 * we must zero out the start of this block.1010 */1011 if (unlikely(sdio->blkfactor && !sdio->start_zero_done))1012 dio_zero_block(dio, sdio, 0, map_bh);1013 1014 /*1015 * Work out, in this_chunk_blocks, how much disk we1016 * can add to this page1017 */1018 this_chunk_blocks = sdio->blocks_available;1019 u = (to - from) >> blkbits;1020 if (this_chunk_blocks > u)1021 this_chunk_blocks = u;1022 u = sdio->final_block_in_request - sdio->block_in_file;1023 if (this_chunk_blocks > u)1024 this_chunk_blocks = u;1025 this_chunk_bytes = this_chunk_blocks << blkbits;1026 BUG_ON(this_chunk_bytes == 0);1027 1028 if (this_chunk_blocks == sdio->blocks_available)1029 sdio->boundary = buffer_boundary(map_bh);1030 ret = submit_page_section(dio, sdio, page,1031 from,1032 this_chunk_bytes,1033 sdio->next_block_for_io,1034 map_bh);1035 if (ret) {1036 dio_unpin_page(dio, page);1037 goto out;1038 }1039 sdio->next_block_for_io += this_chunk_blocks;1040 1041 sdio->block_in_file += this_chunk_blocks;1042 from += this_chunk_bytes;1043 dio->result += this_chunk_bytes;1044 sdio->blocks_available -= this_chunk_blocks;1045next_block:1046 BUG_ON(sdio->block_in_file > sdio->final_block_in_request);1047 if (sdio->block_in_file == sdio->final_block_in_request)1048 break;1049 }1050 1051 /* Drop the pin which was taken in get_user_pages() */1052 dio_unpin_page(dio, page);1053 }1054out:1055 return ret;1056}1057 1058static inline int drop_refcount(struct dio *dio)1059{1060 int ret2;1061 unsigned long flags;1062 1063 /*1064 * Sync will always be dropping the final ref and completing the1065 * operation. AIO can if it was a broken operation described above or1066 * in fact if all the bios race to complete before we get here. In1067 * that case dio_complete() translates the EIOCBQUEUED into the proper1068 * return code that the caller will hand to ->complete().1069 *1070 * This is managed by the bio_lock instead of being an atomic_t so that1071 * completion paths can drop their ref and use the remaining count to1072 * decide to wake the submission path atomically.1073 */1074 spin_lock_irqsave(&dio->bio_lock, flags);1075 ret2 = --dio->refcount;1076 spin_unlock_irqrestore(&dio->bio_lock, flags);1077 return ret2;1078}1079 1080/*1081 * This is a library function for use by filesystem drivers.1082 *1083 * The locking rules are governed by the flags parameter:1084 * - if the flags value contains DIO_LOCKING we use a fancy locking1085 * scheme for dumb filesystems.1086 * For writes this function is called under i_mutex and returns with1087 * i_mutex held, for reads, i_mutex is not held on entry, but it is1088 * taken and dropped again before returning.1089 * - if the flags value does NOT contain DIO_LOCKING we don't use any1090 * internal locking but rather rely on the filesystem to synchronize1091 * direct I/O reads/writes versus each other and truncate.1092 *1093 * To help with locking against truncate we incremented the i_dio_count1094 * counter before starting direct I/O, and decrement it once we are done.1095 * Truncate can wait for it to reach zero to provide exclusion. It is1096 * expected that filesystem provide exclusion between new direct I/O1097 * and truncates. For DIO_LOCKING filesystems this is done by i_mutex,1098 * but other filesystems need to take care of this on their own.1099 *1100 * NOTE: if you pass "sdio" to anything by pointer make sure that function1101 * is always inlined. Otherwise gcc is unable to split the structure into1102 * individual fields and will generate much worse code. This is important1103 * for the whole file.1104 */1105ssize_t __blockdev_direct_IO(struct kiocb *iocb, struct inode *inode,1106 struct block_device *bdev, struct iov_iter *iter,1107 get_block_t get_block, dio_iodone_t end_io,1108 int flags)1109{1110 unsigned i_blkbits = READ_ONCE(inode->i_blkbits);1111 unsigned blkbits = i_blkbits;1112 unsigned blocksize_mask = (1 << blkbits) - 1;1113 ssize_t retval = -EINVAL;1114 const size_t count = iov_iter_count(iter);1115 loff_t offset = iocb->ki_pos;1116 const loff_t end = offset + count;1117 struct dio *dio;1118 struct dio_submit sdio = { NULL, };1119 struct buffer_head map_bh = { 0, };1120 struct blk_plug plug;1121 unsigned long align = offset | iov_iter_alignment(iter);1122 1123 /* watch out for a 0 len io from a tricksy fs */1124 if (iov_iter_rw(iter) == READ && !count)1125 return 0;1126 1127 dio = kmem_cache_alloc(dio_cache, GFP_KERNEL);1128 if (!dio)1129 return -ENOMEM;1130 /*1131 * Believe it or not, zeroing out the page array caused a .5%1132 * performance regression in a database benchmark. So, we take1133 * care to only zero out what's needed.1134 */1135 memset(dio, 0, offsetof(struct dio, pages));1136 1137 dio->flags = flags;1138 if (dio->flags & DIO_LOCKING && iov_iter_rw(iter) == READ) {1139 /* will be released by direct_io_worker */1140 inode_lock(inode);1141 }1142 dio->is_pinned = iov_iter_extract_will_pin(iter);1143 1144 /* Once we sampled i_size check for reads beyond EOF */1145 dio->i_size = i_size_read(inode);1146 if (iov_iter_rw(iter) == READ && offset >= dio->i_size) {1147 retval = 0;1148 goto fail_dio;1149 }1150 1151 if (align & blocksize_mask) {1152 if (bdev)1153 blkbits = blksize_bits(bdev_logical_block_size(bdev));1154 blocksize_mask = (1 << blkbits) - 1;1155 if (align & blocksize_mask)1156 goto fail_dio;1157 }1158 1159 if (dio->flags & DIO_LOCKING && iov_iter_rw(iter) == READ) {1160 struct address_space *mapping = iocb->ki_filp->f_mapping;1161 1162 retval = filemap_write_and_wait_range(mapping, offset, end - 1);1163 if (retval)1164 goto fail_dio;1165 }1166 1167 /*1168 * For file extending writes updating i_size before data writeouts1169 * complete can expose uninitialized blocks in dumb filesystems.1170 * In that case we need to wait for I/O completion even if asked1171 * for an asynchronous write.1172 */1173 if (is_sync_kiocb(iocb))1174 dio->is_async = false;1175 else if (iov_iter_rw(iter) == WRITE && end > i_size_read(inode))1176 dio->is_async = false;1177 else1178 dio->is_async = true;1179 1180 dio->inode = inode;1181 if (iov_iter_rw(iter) == WRITE) {1182 dio->opf = REQ_OP_WRITE | REQ_SYNC | REQ_IDLE;1183 if (iocb->ki_flags & IOCB_NOWAIT)1184 dio->opf |= REQ_NOWAIT;1185 } else {1186 dio->opf = REQ_OP_READ;1187 }1188 1189 /*1190 * For AIO O_(D)SYNC writes we need to defer completions to a workqueue1191 * so that we can call ->fsync.1192 */1193 if (dio->is_async && iov_iter_rw(iter) == WRITE) {1194 retval = 0;1195 if (iocb_is_dsync(iocb))1196 retval = dio_set_defer_completion(dio);1197 else if (!dio->inode->i_sb->s_dio_done_wq) {1198 /*1199 * In case of AIO write racing with buffered read we1200 * need to defer completion. We can't decide this now,1201 * however the workqueue needs to be initialized here.1202 */1203 retval = sb_init_dio_done_wq(dio->inode->i_sb);1204 }1205 if (retval)1206 goto fail_dio;1207 }1208 1209 /*1210 * Will be decremented at I/O completion time.1211 */1212 inode_dio_begin(inode);1213 1214 sdio.blkbits = blkbits;1215 sdio.blkfactor = i_blkbits - blkbits;1216 sdio.block_in_file = offset >> blkbits;1217 1218 sdio.get_block = get_block;1219 dio->end_io = end_io;1220 sdio.final_block_in_bio = -1;1221 sdio.next_block_for_io = -1;1222 1223 dio->iocb = iocb;1224 1225 spin_lock_init(&dio->bio_lock);1226 dio->refcount = 1;1227 1228 dio->should_dirty = user_backed_iter(iter) && iov_iter_rw(iter) == READ;1229 sdio.iter = iter;1230 sdio.final_block_in_request = end >> blkbits;1231 1232 /*1233 * In case of non-aligned buffers, we may need 2 more1234 * pages since we need to zero out first and last block.1235 */1236 if (unlikely(sdio.blkfactor))1237 sdio.pages_in_io = 2;1238 1239 sdio.pages_in_io += iov_iter_npages(iter, INT_MAX);1240 1241 blk_start_plug(&plug);1242 1243 retval = do_direct_IO(dio, &sdio, &map_bh);1244 if (retval)1245 dio_cleanup(dio, &sdio);1246 1247 if (retval == -ENOTBLK) {1248 /*1249 * The remaining part of the request will be1250 * handled by buffered I/O when we return1251 */1252 retval = 0;1253 }1254 /*1255 * There may be some unwritten disk at the end of a part-written1256 * fs-block-sized block. Go zero that now.1257 */1258 dio_zero_block(dio, &sdio, 1, &map_bh);1259 1260 if (sdio.cur_page) {1261 ssize_t ret2;1262 1263 ret2 = dio_send_cur_page(dio, &sdio, &map_bh);1264 if (retval == 0)1265 retval = ret2;1266 dio_unpin_page(dio, sdio.cur_page);1267 sdio.cur_page = NULL;1268 }1269 if (sdio.bio)1270 dio_bio_submit(dio, &sdio);1271 1272 blk_finish_plug(&plug);1273 1274 /*1275 * It is possible that, we return short IO due to end of file.1276 * In that case, we need to release all the pages we got hold on.1277 */1278 dio_cleanup(dio, &sdio);1279 1280 /*1281 * All block lookups have been performed. For READ requests1282 * we can let i_mutex go now that its achieved its purpose1283 * of protecting us from looking up uninitialized blocks.1284 */1285 if (iov_iter_rw(iter) == READ && (dio->flags & DIO_LOCKING))1286 inode_unlock(dio->inode);1287 1288 /*1289 * The only time we want to leave bios in flight is when a successful1290 * partial aio read or full aio write have been setup. In that case1291 * bio completion will call aio_complete. The only time it's safe to1292 * call aio_complete is when we return -EIOCBQUEUED, so we key on that.1293 * This had *better* be the only place that raises -EIOCBQUEUED.1294 */1295 BUG_ON(retval == -EIOCBQUEUED);1296 if (dio->is_async && retval == 0 && dio->result &&1297 (iov_iter_rw(iter) == READ || dio->result == count))1298 retval = -EIOCBQUEUED;1299 else1300 dio_await_completion(dio);1301 1302 if (drop_refcount(dio) == 0) {1303 retval = dio_complete(dio, retval, DIO_COMPLETE_INVALIDATE);1304 } else1305 BUG_ON(retval != -EIOCBQUEUED);1306 1307 return retval;1308 1309fail_dio:1310 if (dio->flags & DIO_LOCKING && iov_iter_rw(iter) == READ)1311 inode_unlock(inode);1312 1313 kmem_cache_free(dio_cache, dio);1314 return retval;1315}1316EXPORT_SYMBOL(__blockdev_direct_IO);1317 1318static __init int dio_init(void)1319{1320 dio_cache = KMEM_CACHE(dio, SLAB_PANIC);1321 return 0;1322}1323module_init(dio_init)1324