| // SPDX-License-Identifier: GPL-2.0-only |
| /* |
| * fs/direct-io.c |
| * |
| * Copyright (C) 2002, Linus Torvalds. |
| * |
| * O_DIRECT |
| * |
| * 04Jul2002 Andrew Morton |
| * Initial version |
| * 11Sep2002 janetinc@us.ibm.com |
| * added readv/writev support. |
| * 29Oct2002 Andrew Morton |
| * rewrote bio_add_page() support. |
| * 30Oct2002 pbadari@us.ibm.com |
| * added support for non-aligned IO. |
| * 06Nov2002 pbadari@us.ibm.com |
| * added asynchronous IO support. |
| * 21Jul2003 nathans@sgi.com |
| * added IO completion notifier. |
| */ |
| |
| #include <linux/kernel.h> |
| #include <linux/module.h> |
| #include <linux/types.h> |
| #include <linux/fs.h> |
| #include <linux/mm.h> |
| #include <linux/slab.h> |
| #include <linux/highmem.h> |
| #include <linux/pagemap.h> |
| #include <linux/task_io_accounting_ops.h> |
| #include <linux/bio.h> |
| #include <linux/wait.h> |
| #include <linux/err.h> |
| #include <linux/blkdev.h> |
| #include <linux/buffer_head.h> |
| #include <linux/rwsem.h> |
| #include <linux/uio.h> |
| #include <linux/atomic.h> |
| #include <linux/prefetch.h> |
| |
| #include "internal.h" |
| |
| /* |
| * How many user pages to map in one call to get_user_pages(). This determines |
| * the size of a structure in the slab cache |
| */ |
| #define DIO_PAGES 64 |
| |
| /* |
| * Flags for dio_complete() |
| */ |
| #define DIO_COMPLETE_ASYNC 0x01 /* This is async IO */ |
| #define DIO_COMPLETE_INVALIDATE 0x02 /* Can invalidate pages */ |
| |
| /* |
| * This code generally works in units of "dio_blocks". A dio_block is |
| * somewhere between the hard sector size and the filesystem block size. it |
| * is determined on a per-invocation basis. When talking to the filesystem |
| * we need to convert dio_blocks to fs_blocks by scaling the dio_block quantity |
| * down by dio->blkfactor. Similarly, fs-blocksize quantities are converted |
| * to bio_block quantities by shifting left by blkfactor. |
| * |
| * If blkfactor is zero then the user's request was aligned to the filesystem's |
| * blocksize. |
| */ |
| |
| /* dio_state only used in the submission path */ |
| |
| struct dio_submit { |
| struct bio *bio; /* bio under assembly */ |
| unsigned blkbits; /* doesn't change */ |
| unsigned blkfactor; /* When we're using an alignment which |
| is finer than the filesystem's soft |
| blocksize, this specifies how much |
| finer. blkfactor=2 means 1/4-block |
| alignment. Does not change */ |
| unsigned start_zero_done; /* flag: sub-blocksize zeroing has |
| been performed at the start of a |
| write */ |
| int pages_in_io; /* approximate total IO pages */ |
| sector_t block_in_file; /* Current offset into the underlying |
| file in dio_block units. */ |
| unsigned blocks_available; /* At block_in_file. changes */ |
| int reap_counter; /* rate limit reaping */ |
| sector_t final_block_in_request;/* doesn't change */ |
| int boundary; /* prev block is at a boundary */ |
| get_block_t *get_block; /* block mapping function */ |
| dio_submit_t *submit_io; /* IO submition function */ |
| |
| loff_t logical_offset_in_bio; /* current first logical block in bio */ |
| sector_t final_block_in_bio; /* current final block in bio + 1 */ |
| sector_t next_block_for_io; /* next block to be put under IO, |
| in dio_blocks units */ |
| |
| /* |
| * Deferred addition of a page to the dio. These variables are |
| * private to dio_send_cur_page(), submit_page_section() and |
| * dio_bio_add_page(). |
| */ |
| struct page *cur_page; /* The page */ |
| unsigned cur_page_offset; /* Offset into it, in bytes */ |
| unsigned cur_page_len; /* Nr of bytes at cur_page_offset */ |
| sector_t cur_page_block; /* Where it starts */ |
| loff_t cur_page_fs_offset; /* Offset in file */ |
| |
| struct iov_iter *iter; |
| /* |
| * Page queue. These variables belong to dio_refill_pages() and |
| * dio_get_page(). |
| */ |
| unsigned head; /* next page to process */ |
| unsigned tail; /* last valid page + 1 */ |
| size_t from, to; |
| }; |
| |
| /* dio_state communicated between submission path and end_io */ |
| struct dio { |
| int flags; /* doesn't change */ |
| int op; |
| int op_flags; |
| blk_qc_t bio_cookie; |
| struct gendisk *bio_disk; |
| struct inode *inode; |
| loff_t i_size; /* i_size when submitted */ |
| dio_iodone_t *end_io; /* IO completion function */ |
| |
| void *private; /* copy from map_bh.b_private */ |
| |
| /* BIO completion state */ |
| spinlock_t bio_lock; /* protects BIO fields below */ |
| int page_errors; /* errno from get_user_pages() */ |
| int is_async; /* is IO async ? */ |
| bool defer_completion; /* defer AIO completion to workqueue? */ |
| bool should_dirty; /* if pages should be dirtied */ |
| int io_error; /* IO error in completion path */ |
| unsigned long refcount; /* direct_io_worker() and bios */ |
| struct bio *bio_list; /* singly linked via bi_private */ |
| struct task_struct *waiter; /* waiting task (NULL if none) */ |
| |
| /* AIO related stuff */ |
| struct kiocb *iocb; /* kiocb */ |
| ssize_t result; /* IO result */ |
| |
| /* |
| * pages[] (and any fields placed after it) are not zeroed out at |
| * allocation time. Don't add new fields after pages[] unless you |
| * wish that they not be zeroed. |
| */ |
| union { |
| struct page *pages[DIO_PAGES]; /* page buffer */ |
| struct work_struct complete_work;/* deferred AIO completion */ |
| }; |
| } ____cacheline_aligned_in_smp; |
| |
| static struct kmem_cache *dio_cache __read_mostly; |
| |
| /* |
| * How many pages are in the queue? |
| */ |
| static inline unsigned dio_pages_present(struct dio_submit *sdio) |
| { |
| return sdio->tail - sdio->head; |
| } |
| |
| /* |
| * Go grab and pin some userspace pages. Typically we'll get 64 at a time. |
| */ |
| static inline int dio_refill_pages(struct dio *dio, struct dio_submit *sdio) |
| { |
| ssize_t ret; |
| |
| ret = iov_iter_get_pages(sdio->iter, dio->pages, LONG_MAX, DIO_PAGES, |
| &sdio->from); |
| |
| if (ret < 0 && sdio->blocks_available && (dio->op == REQ_OP_WRITE)) { |
| struct page *page = ZERO_PAGE(0); |
| /* |
| * A memory fault, but the filesystem has some outstanding |
| * mapped blocks. We need to use those blocks up to avoid |
| * leaking stale data in the file. |
| */ |
| if (dio->page_errors == 0) |
| dio->page_errors = ret; |
| get_page(page); |
| dio->pages[0] = page; |
| sdio->head = 0; |
| sdio->tail = 1; |
| sdio->from = 0; |
| sdio->to = PAGE_SIZE; |
| return 0; |
| } |
| |
| if (ret >= 0) { |
| iov_iter_advance(sdio->iter, ret); |
| ret += sdio->from; |
| sdio->head = 0; |
| sdio->tail = (ret + PAGE_SIZE - 1) / PAGE_SIZE; |
| sdio->to = ((ret - 1) & (PAGE_SIZE - 1)) + 1; |
| return 0; |
| } |
| return ret; |
| } |
| |
| /* |
| * Get another userspace page. Returns an ERR_PTR on error. Pages are |
| * buffered inside the dio so that we can call get_user_pages() against a |
| * decent number of pages, less frequently. To provide nicer use of the |
| * L1 cache. |
| */ |
| static inline struct page *dio_get_page(struct dio *dio, |
| struct dio_submit *sdio) |
| { |
| if (dio_pages_present(sdio) == 0) { |
| int ret; |
| |
| ret = dio_refill_pages(dio, sdio); |
| if (ret) |
| return ERR_PTR(ret); |
| BUG_ON(dio_pages_present(sdio) == 0); |
| } |
| return dio->pages[sdio->head]; |
| } |
| |
| /* |
| * dio_complete() - called when all DIO BIO I/O has been completed |
| * |
| * This drops i_dio_count, lets interested parties know that a DIO operation |
| * has completed, and calculates the resulting return code for the operation. |
| * |
| * It lets the filesystem know if it registered an interest earlier via |
| * get_block. Pass the private field of the map buffer_head so that |
| * filesystems can use it to hold additional state between get_block calls and |
| * dio_complete. |
| */ |
| static ssize_t dio_complete(struct dio *dio, ssize_t ret, unsigned int flags) |
| { |
| loff_t offset = dio->iocb->ki_pos; |
| ssize_t transferred = 0; |
| int err; |
| |
| /* |
| * AIO submission can race with bio completion to get here while |
| * expecting to have the last io completed by bio completion. |
| * In that case -EIOCBQUEUED is in fact not an error we want |
| * to preserve through this call. |
| */ |
| if (ret == -EIOCBQUEUED) |
| ret = 0; |
| |
| if (dio->result) { |
| transferred = dio->result; |
| |
| /* Check for short read case */ |
| if ((dio->op == REQ_OP_READ) && |
| ((offset + transferred) > dio->i_size)) |
| transferred = dio->i_size - offset; |
| /* ignore EFAULT if some IO has been done */ |
| if (unlikely(ret == -EFAULT) && transferred) |
| ret = 0; |
| } |
| |
| if (ret == 0) |
| ret = dio->page_errors; |
| if (ret == 0) |
| ret = dio->io_error; |
| if (ret == 0) |
| ret = transferred; |
| |
| if (dio->end_io) { |
| // XXX: ki_pos?? |
| err = dio->end_io(dio->iocb, offset, ret, dio->private); |
| if (err) |
| ret = err; |
| } |
| |
| /* |
| * Try again to invalidate clean pages which might have been cached by |
| * non-direct readahead, or faulted in by get_user_pages() if the source |
| * of the write was an mmap'ed region of the file we're writing. Either |
| * one is a pretty crazy thing to do, so we don't support it 100%. If |
| * this invalidation fails, tough, the write still worked... |
| * |
| * And this page cache invalidation has to be after dio->end_io(), as |
| * some filesystems convert unwritten extents to real allocations in |
| * end_io() when necessary, otherwise a racing buffer read would cache |
| * zeros from unwritten extents. |
| */ |
| if (flags & DIO_COMPLETE_INVALIDATE && |
| ret > 0 && dio->op == REQ_OP_WRITE && |
| dio->inode->i_mapping->nrpages) { |
| err = invalidate_inode_pages2_range(dio->inode->i_mapping, |
| offset >> PAGE_SHIFT, |
| (offset + ret - 1) >> PAGE_SHIFT); |
| if (err) |
| dio_warn_stale_pagecache(dio->iocb->ki_filp); |
| } |
| |
| inode_dio_end(dio->inode); |
| |
| if (flags & DIO_COMPLETE_ASYNC) { |
| /* |
| * generic_write_sync expects ki_pos to have been updated |
| * already, but the submission path only does this for |
| * synchronous I/O. |
| */ |
| dio->iocb->ki_pos += transferred; |
| |
| if (ret > 0 && dio->op == REQ_OP_WRITE) |
| ret = generic_write_sync(dio->iocb, ret); |
| dio->iocb->ki_complete(dio->iocb, ret, 0); |
| } |
| |
| kmem_cache_free(dio_cache, dio); |
| return ret; |
| } |
| |
| static void dio_aio_complete_work(struct work_struct *work) |
| { |
| struct dio *dio = container_of(work, struct dio, complete_work); |
| |
| dio_complete(dio, 0, DIO_COMPLETE_ASYNC | DIO_COMPLETE_INVALIDATE); |
| } |
| |
| static blk_status_t dio_bio_complete(struct dio *dio, struct bio *bio); |
| |
| /* |
| * Asynchronous IO callback. |
| */ |
| static void dio_bio_end_aio(struct bio *bio) |
| { |
| struct dio *dio = bio->bi_private; |
| unsigned long remaining; |
| unsigned long flags; |
| bool defer_completion = false; |
| |
| /* cleanup the bio */ |
| dio_bio_complete(dio, bio); |
| |
| spin_lock_irqsave(&dio->bio_lock, flags); |
| remaining = --dio->refcount; |
| if (remaining == 1 && dio->waiter) |
| wake_up_process(dio->waiter); |
| spin_unlock_irqrestore(&dio->bio_lock, flags); |
| |
| if (remaining == 0) { |
| /* |
| * Defer completion when defer_completion is set or |
| * when the inode has pages mapped and this is AIO write. |
| * We need to invalidate those pages because there is a |
| * chance they contain stale data in the case buffered IO |
| * went in between AIO submission and completion into the |
| * same region. |
| */ |
| if (dio->result) |
| defer_completion = dio->defer_completion || |
| (dio->op == REQ_OP_WRITE && |
| dio->inode->i_mapping->nrpages); |
| if (defer_completion) { |
| INIT_WORK(&dio->complete_work, dio_aio_complete_work); |
| queue_work(dio->inode->i_sb->s_dio_done_wq, |
| &dio->complete_work); |
| } else { |
| dio_complete(dio, 0, DIO_COMPLETE_ASYNC); |
| } |
| } |
| } |
| |
| /* |
| * The BIO completion handler simply queues the BIO up for the process-context |
| * handler. |
| * |
| * During I/O bi_private points at the dio. After I/O, bi_private is used to |
| * implement a singly-linked list of completed BIOs, at dio->bio_list. |
| */ |
| static void dio_bio_end_io(struct bio *bio) |
| { |
| struct dio *dio = bio->bi_private; |
| unsigned long flags; |
| |
| spin_lock_irqsave(&dio->bio_lock, flags); |
| bio->bi_private = dio->bio_list; |
| dio->bio_list = bio; |
| if (--dio->refcount == 1 && dio->waiter) |
| wake_up_process(dio->waiter); |
| spin_unlock_irqrestore(&dio->bio_lock, flags); |
| } |
| |
| static inline void |
| dio_bio_alloc(struct dio *dio, struct dio_submit *sdio, |
| struct block_device *bdev, |
| sector_t first_sector, int nr_vecs) |
| { |
| struct bio *bio; |
| |
| /* |
| * bio_alloc() is guaranteed to return a bio when allowed to sleep and |
| * we request a valid number of vectors. |
| */ |
| bio = bio_alloc(GFP_KERNEL, nr_vecs); |
| |
| bio_set_dev(bio, bdev); |
| bio->bi_iter.bi_sector = first_sector; |
| bio_set_op_attrs(bio, dio->op, dio->op_flags); |
| if (dio->is_async) |
| bio->bi_end_io = dio_bio_end_aio; |
| else |
| bio->bi_end_io = dio_bio_end_io; |
| |
| bio->bi_write_hint = dio->iocb->ki_hint; |
| |
| sdio->bio = bio; |
| sdio->logical_offset_in_bio = sdio->cur_page_fs_offset; |
| } |
| |
| /* |
| * In the AIO read case we speculatively dirty the pages before starting IO. |
| * During IO completion, any of these pages which happen to have been written |
| * back will be redirtied by bio_check_pages_dirty(). |
| * |
| * bios hold a dio reference between submit_bio and ->end_io. |
| */ |
| static inline void dio_bio_submit(struct dio *dio, struct dio_submit *sdio) |
| { |
| struct bio *bio = sdio->bio; |
| unsigned long flags; |
| |
| bio->bi_private = dio; |
| |
| spin_lock_irqsave(&dio->bio_lock, flags); |
| dio->refcount++; |
| spin_unlock_irqrestore(&dio->bio_lock, flags); |
| |
| if (dio->is_async && dio->op == REQ_OP_READ && dio->should_dirty) |
| bio_set_pages_dirty(bio); |
| |
| dio->bio_disk = bio->bi_disk; |
| |
| if (sdio->submit_io) { |
| sdio->submit_io(bio, dio->inode, sdio->logical_offset_in_bio); |
| dio->bio_cookie = BLK_QC_T_NONE; |
| } else |
| dio->bio_cookie = submit_bio(bio); |
| |
| sdio->bio = NULL; |
| sdio->boundary = 0; |
| sdio->logical_offset_in_bio = 0; |
| } |
| |
| /* |
| * Release any resources in case of a failure |
| */ |
| static inline void dio_cleanup(struct dio *dio, struct dio_submit *sdio) |
| { |
| while (sdio->head < sdio->tail) |
| put_page(dio->pages[sdio->head++]); |
| } |
| |
| /* |
| * Wait for the next BIO to complete. Remove it and return it. NULL is |
| * returned once all BIOs have been completed. This must only be called once |
| * all bios have been issued so that dio->refcount can only decrease. This |
| * requires that that the caller hold a reference on the dio. |
| */ |
| static struct bio *dio_await_one(struct dio *dio) |
| { |
| unsigned long flags; |
| struct bio *bio = NULL; |
| |
| spin_lock_irqsave(&dio->bio_lock, flags); |
| |
| /* |
| * Wait as long as the list is empty and there are bios in flight. bio |
| * completion drops the count, maybe adds to the list, and wakes while |
| * holding the bio_lock so we don't need set_current_state()'s barrier |
| * and can call it after testing our condition. |
| */ |
| while (dio->refcount > 1 && dio->bio_list == NULL) { |
| __set_current_state(TASK_UNINTERRUPTIBLE); |
| dio->waiter = current; |
| spin_unlock_irqrestore(&dio->bio_lock, flags); |
| if (!(dio->iocb->ki_flags & IOCB_HIPRI) || |
| !blk_poll(dio->bio_disk->queue, dio->bio_cookie, true)) |
| blk_io_schedule(); |
| /* wake up sets us TASK_RUNNING */ |
| spin_lock_irqsave(&dio->bio_lock, flags); |
| dio->waiter = NULL; |
| } |
| if (dio->bio_list) { |
| bio = dio->bio_list; |
| dio->bio_list = bio->bi_private; |
| } |
| spin_unlock_irqrestore(&dio->bio_lock, flags); |
| return bio; |
| } |
| |
| /* |
| * Process one completed BIO. No locks are held. |
| */ |
| static blk_status_t dio_bio_complete(struct dio *dio, struct bio *bio) |
| { |
| blk_status_t err = bio->bi_status; |
| bool should_dirty = dio->op == REQ_OP_READ && dio->should_dirty; |
| |
| if (err) { |
| if (err == BLK_STS_AGAIN && (bio->bi_opf & REQ_NOWAIT)) |
| dio->io_error = -EAGAIN; |
| else |
| dio->io_error = -EIO; |
| } |
| |
| if (dio->is_async && should_dirty) { |
| bio_check_pages_dirty(bio); /* transfers ownership */ |
| } else { |
| bio_release_pages(bio, should_dirty); |
| bio_put(bio); |
| } |
| return err; |
| } |
| |
| /* |
| * Wait on and process all in-flight BIOs. This must only be called once |
| * all bios have been issued so that the refcount can only decrease. |
| * This just waits for all bios to make it through dio_bio_complete. IO |
| * errors are propagated through dio->io_error and should be propagated via |
| * dio_complete(). |
| */ |
| static void dio_await_completion(struct dio *dio) |
| { |
| struct bio *bio; |
| do { |
| bio = dio_await_one(dio); |
| if (bio) |
| dio_bio_complete(dio, bio); |
| } while (bio); |
| } |
| |
| /* |
| * A really large O_DIRECT read or write can generate a lot of BIOs. So |
| * to keep the memory consumption sane we periodically reap any completed BIOs |
| * during the BIO generation phase. |
| * |
| * This also helps to limit the peak amount of pinned userspace memory. |
| */ |
| static inline int dio_bio_reap(struct dio *dio, struct dio_submit *sdio) |
| { |
| int ret = 0; |
| |
| if (sdio->reap_counter++ >= 64) { |
| while (dio->bio_list) { |
| unsigned long flags; |
| struct bio *bio; |
| int ret2; |
| |
| spin_lock_irqsave(&dio->bio_lock, flags); |
| bio = dio->bio_list; |
| dio->bio_list = bio->bi_private; |
| spin_unlock_irqrestore(&dio->bio_lock, flags); |
| ret2 = blk_status_to_errno(dio_bio_complete(dio, bio)); |
| if (ret == 0) |
| ret = ret2; |
| } |
| sdio->reap_counter = 0; |
| } |
| return ret; |
| } |
| |
| /* |
| * Create workqueue for deferred direct IO completions. We allocate the |
| * workqueue when it's first needed. This avoids creating workqueue for |
| * filesystems that don't need it and also allows us to create the workqueue |
| * late enough so the we can include s_id in the name of the workqueue. |
| */ |
| int sb_init_dio_done_wq(struct super_block *sb) |
| { |
| struct workqueue_struct *old; |
| struct workqueue_struct *wq = alloc_workqueue("dio/%s", |
| WQ_MEM_RECLAIM, 0, |
| sb->s_id); |
| if (!wq) |
| return -ENOMEM; |
| /* |
| * This has to be atomic as more DIOs can race to create the workqueue |
| */ |
| old = cmpxchg(&sb->s_dio_done_wq, NULL, wq); |
| /* Someone created workqueue before us? Free ours... */ |
| if (old) |
| destroy_workqueue(wq); |
| return 0; |
| } |
| |
| static int dio_set_defer_completion(struct dio *dio) |
| { |
| struct super_block *sb = dio->inode->i_sb; |
| |
| if (dio->defer_completion) |
| return 0; |
| dio->defer_completion = true; |
| if (!sb->s_dio_done_wq) |
| return sb_init_dio_done_wq(sb); |
| return 0; |
| } |
| |
| /* |
| * Call into the fs to map some more disk blocks. We record the current number |
| * of available blocks at sdio->blocks_available. These are in units of the |
| * fs blocksize, i_blocksize(inode). |
| * |
| * The fs is allowed to map lots of blocks at once. If it wants to do that, |
| * it uses the passed inode-relative block number as the file offset, as usual. |
| * |
| * get_block() is passed the number of i_blkbits-sized blocks which direct_io |
| * has remaining to do. The fs should not map more than this number of blocks. |
| * |
| * If the fs has mapped a lot of blocks, it should populate bh->b_size to |
| * indicate how much contiguous disk space has been made available at |
| * bh->b_blocknr. |
| * |
| * If *any* of the mapped blocks are new, then the fs must set buffer_new(). |
| * This isn't very efficient... |
| * |
| * In the case of filesystem holes: the fs may return an arbitrarily-large |
| * hole by returning an appropriate value in b_size and by clearing |
| * buffer_mapped(). However the direct-io code will only process holes one |
| * block at a time - it will repeatedly call get_block() as it walks the hole. |
| */ |
| static int get_more_blocks(struct dio *dio, struct dio_submit *sdio, |
| struct buffer_head *map_bh) |
| { |
| int ret; |
| sector_t fs_startblk; /* Into file, in filesystem-sized blocks */ |
| sector_t fs_endblk; /* Into file, in filesystem-sized blocks */ |
| unsigned long fs_count; /* Number of filesystem-sized blocks */ |
| int create; |
| unsigned int i_blkbits = sdio->blkbits + sdio->blkfactor; |
| loff_t i_size; |
| |
| /* |
| * If there was a memory error and we've overwritten all the |
| * mapped blocks then we can now return that memory error |
| */ |
| ret = dio->page_errors; |
| if (ret == 0) { |
| BUG_ON(sdio->block_in_file >= sdio->final_block_in_request); |
| fs_startblk = sdio->block_in_file >> sdio->blkfactor; |
| fs_endblk = (sdio->final_block_in_request - 1) >> |
| sdio->blkfactor; |
| fs_count = fs_endblk - fs_startblk + 1; |
| |
| map_bh->b_state = 0; |
| map_bh->b_size = fs_count << i_blkbits; |
| |
| /* |
| * For writes that could fill holes inside i_size on a |
| * DIO_SKIP_HOLES filesystem we forbid block creations: only |
| * overwrites are permitted. We will return early to the caller |
| * once we see an unmapped buffer head returned, and the caller |
| * will fall back to buffered I/O. |
| * |
| * Otherwise the decision is left to the get_blocks method, |
| * which may decide to handle it or also return an unmapped |
| * buffer head. |
| */ |
| create = dio->op == REQ_OP_WRITE; |
| if (dio->flags & DIO_SKIP_HOLES) { |
| i_size = i_size_read(dio->inode); |
| if (i_size && fs_startblk <= (i_size - 1) >> i_blkbits) |
| create = 0; |
| } |
| |
| ret = (*sdio->get_block)(dio->inode, fs_startblk, |
| map_bh, create); |
| |
| /* Store for completion */ |
| dio->private = map_bh->b_private; |
| |
| if (ret == 0 && buffer_defer_completion(map_bh)) |
| ret = dio_set_defer_completion(dio); |
| } |
| return ret; |
| } |
| |
| /* |
| * There is no bio. Make one now. |
| */ |
| static inline int dio_new_bio(struct dio *dio, struct dio_submit *sdio, |
| sector_t start_sector, struct buffer_head *map_bh) |
| { |
| sector_t sector; |
| int ret, nr_pages; |
| |
| ret = dio_bio_reap(dio, sdio); |
| if (ret) |
| goto out; |
| sector = start_sector << (sdio->blkbits - 9); |
| nr_pages = min(sdio->pages_in_io, BIO_MAX_PAGES); |
| BUG_ON(nr_pages <= 0); |
| dio_bio_alloc(dio, sdio, map_bh->b_bdev, sector, nr_pages); |
| sdio->boundary = 0; |
| out: |
| return ret; |
| } |
| |
| /* |
| * Attempt to put the current chunk of 'cur_page' into the current BIO. If |
| * that was successful then update final_block_in_bio and take a ref against |
| * the just-added page. |
| * |
| * Return zero on success. Non-zero means the caller needs to start a new BIO. |
| */ |
| static inline int dio_bio_add_page(struct dio_submit *sdio) |
| { |
| int ret; |
| |
| ret = bio_add_page(sdio->bio, sdio->cur_page, |
| sdio->cur_page_len, sdio->cur_page_offset); |
| if (ret == sdio->cur_page_len) { |
| /* |
| * Decrement count only, if we are done with this page |
| */ |
| if ((sdio->cur_page_len + sdio->cur_page_offset) == PAGE_SIZE) |
| sdio->pages_in_io--; |
| get_page(sdio->cur_page); |
| sdio->final_block_in_bio = sdio->cur_page_block + |
| (sdio->cur_page_len >> sdio->blkbits); |
| ret = 0; |
| } else { |
| ret = 1; |
| } |
| return ret; |
| } |
| |
| /* |
| * Put cur_page under IO. The section of cur_page which is described by |
| * cur_page_offset,cur_page_len is put into a BIO. The section of cur_page |
| * starts on-disk at cur_page_block. |
| * |
| * We take a ref against the page here (on behalf of its presence in the bio). |
| * |
| * The caller of this function is responsible for removing cur_page from the |
| * dio, and for dropping the refcount which came from that presence. |
| */ |
| static inline int dio_send_cur_page(struct dio *dio, struct dio_submit *sdio, |
| struct buffer_head *map_bh) |
| { |
| int ret = 0; |
| |
| if (sdio->bio) { |
| loff_t cur_offset = sdio->cur_page_fs_offset; |
| loff_t bio_next_offset = sdio->logical_offset_in_bio + |
| sdio->bio->bi_iter.bi_size; |
| |
| /* |
| * See whether this new request is contiguous with the old. |
| * |
| * Btrfs cannot handle having logically non-contiguous requests |
| * submitted. For example if you have |
| * |
| * Logical: [0-4095][HOLE][8192-12287] |
| * Physical: [0-4095] [4096-8191] |
| * |
| * We cannot submit those pages together as one BIO. So if our |
| * current logical offset in the file does not equal what would |
| * be the next logical offset in the bio, submit the bio we |
| * have. |
| */ |
| if (sdio->final_block_in_bio != sdio->cur_page_block || |
| cur_offset != bio_next_offset) |
| dio_bio_submit(dio, sdio); |
| } |
| |
| if (sdio->bio == NULL) { |
| ret = dio_new_bio(dio, sdio, sdio->cur_page_block, map_bh); |
| if (ret) |
| goto out; |
| } |
| |
| if (dio_bio_add_page(sdio) != 0) { |
| dio_bio_submit(dio, sdio); |
| ret = dio_new_bio(dio, sdio, sdio->cur_page_block, map_bh); |
| if (ret == 0) { |
| ret = dio_bio_add_page(sdio); |
| BUG_ON(ret != 0); |
| } |
| } |
| out: |
| return ret; |
| } |
| |
| /* |
| * An autonomous function to put a chunk of a page under deferred IO. |
| * |
| * The caller doesn't actually know (or care) whether this piece of page is in |
| * a BIO, or is under IO or whatever. We just take care of all possible |
| * situations here. The separation between the logic of do_direct_IO() and |
| * that of submit_page_section() is important for clarity. Please don't break. |
| * |
| * The chunk of page starts on-disk at blocknr. |
| * |
| * We perform deferred IO, by recording the last-submitted page inside our |
| * private part of the dio structure. If possible, we just expand the IO |
| * across that page here. |
| * |
| * If that doesn't work out then we put the old page into the bio and add this |
| * page to the dio instead. |
| */ |
| static inline int |
| submit_page_section(struct dio *dio, struct dio_submit *sdio, struct page *page, |
| unsigned offset, unsigned len, sector_t blocknr, |
| struct buffer_head *map_bh) |
| { |
| int ret = 0; |
| |
| if (dio->op == REQ_OP_WRITE) { |
| /* |
| * Read accounting is performed in submit_bio() |
| */ |
| task_io_account_write(len); |
| } |
| |
| /* |
| * Can we just grow the current page's presence in the dio? |
| */ |
| if (sdio->cur_page == page && |
| sdio->cur_page_offset + sdio->cur_page_len == offset && |
| sdio->cur_page_block + |
| (sdio->cur_page_len >> sdio->blkbits) == blocknr) { |
| sdio->cur_page_len += len; |
| goto out; |
| } |
| |
| /* |
| * If there's a deferred page already there then send it. |
| */ |
| if (sdio->cur_page) { |
| ret = dio_send_cur_page(dio, sdio, map_bh); |
| put_page(sdio->cur_page); |
| sdio->cur_page = NULL; |
| if (ret) |
| return ret; |
| } |
| |
| get_page(page); /* It is in dio */ |
| sdio->cur_page = page; |
| sdio->cur_page_offset = offset; |
| sdio->cur_page_len = len; |
| sdio->cur_page_block = blocknr; |
| sdio->cur_page_fs_offset = sdio->block_in_file << sdio->blkbits; |
| out: |
| /* |
| * If sdio->boundary then we want to schedule the IO now to |
| * avoid metadata seeks. |
| */ |
| if (sdio->boundary) { |
| ret = dio_send_cur_page(dio, sdio, map_bh); |
| if (sdio->bio) |
| dio_bio_submit(dio, sdio); |
| put_page(sdio->cur_page); |
| sdio->cur_page = NULL; |
| } |
| return ret; |
| } |
| |
| /* |
| * If we are not writing the entire block and get_block() allocated |
| * the block for us, we need to fill-in the unused portion of the |
| * block with zeros. This happens only if user-buffer, fileoffset or |
| * io length is not filesystem block-size multiple. |
| * |
| * `end' is zero if we're doing the start of the IO, 1 at the end of the |
| * IO. |
| */ |
| static inline void dio_zero_block(struct dio *dio, struct dio_submit *sdio, |
| int end, struct buffer_head *map_bh) |
| { |
| unsigned dio_blocks_per_fs_block; |
| unsigned this_chunk_blocks; /* In dio_blocks */ |
| unsigned this_chunk_bytes; |
| struct page *page; |
| |
| sdio->start_zero_done = 1; |
| if (!sdio->blkfactor || !buffer_new(map_bh)) |
| return; |
| |
| dio_blocks_per_fs_block = 1 << sdio->blkfactor; |
| this_chunk_blocks = sdio->block_in_file & (dio_blocks_per_fs_block - 1); |
| |
| if (!this_chunk_blocks) |
| return; |
| |
| /* |
| * We need to zero out part of an fs block. It is either at the |
| * beginning or the end of the fs block. |
| */ |
| if (end) |
| this_chunk_blocks = dio_blocks_per_fs_block - this_chunk_blocks; |
| |
| this_chunk_bytes = this_chunk_blocks << sdio->blkbits; |
| |
| page = ZERO_PAGE(0); |
| if (submit_page_section(dio, sdio, page, 0, this_chunk_bytes, |
| sdio->next_block_for_io, map_bh)) |
| return; |
| |
| sdio->next_block_for_io += this_chunk_blocks; |
| } |
| |
| /* |
| * Walk the user pages, and the file, mapping blocks to disk and generating |
| * a sequence of (page,offset,len,block) mappings. These mappings are injected |
| * into submit_page_section(), which takes care of the next stage of submission |
| * |
| * Direct IO against a blockdev is different from a file. Because we can |
| * happily perform page-sized but 512-byte aligned IOs. It is important that |
| * blockdev IO be able to have fine alignment and large sizes. |
| * |
| * So what we do is to permit the ->get_block function to populate bh.b_size |
| * with the size of IO which is permitted at this offset and this i_blkbits. |
| * |
| * For best results, the blockdev should be set up with 512-byte i_blkbits and |
| * it should set b_size to PAGE_SIZE or more inside get_block(). This gives |
| * fine alignment but still allows this function to work in PAGE_SIZE units. |
| */ |
| static int do_direct_IO(struct dio *dio, struct dio_submit *sdio, |
| struct buffer_head *map_bh) |
| { |
| const unsigned blkbits = sdio->blkbits; |
| const unsigned i_blkbits = blkbits + sdio->blkfactor; |
| int ret = 0; |
| |
| while (sdio->block_in_file < sdio->final_block_in_request) { |
| struct page *page; |
| size_t from, to; |
| |
| page = dio_get_page(dio, sdio); |
| if (IS_ERR(page)) { |
| ret = PTR_ERR(page); |
| goto out; |
| } |
| from = sdio->head ? 0 : sdio->from; |
| to = (sdio->head == sdio->tail - 1) ? sdio->to : PAGE_SIZE; |
| sdio->head++; |
| |
| while (from < to) { |
| unsigned this_chunk_bytes; /* # of bytes mapped */ |
| unsigned this_chunk_blocks; /* # of blocks */ |
| unsigned u; |
| |
| if (sdio->blocks_available == 0) { |
| /* |
| * Need to go and map some more disk |
| */ |
| unsigned long blkmask; |
| unsigned long dio_remainder; |
| |
| ret = get_more_blocks(dio, sdio, map_bh); |
| if (ret) { |
| put_page(page); |
| goto out; |
| } |
| if (!buffer_mapped(map_bh)) |
| goto do_holes; |
| |
| sdio->blocks_available = |
| map_bh->b_size >> blkbits; |
| sdio->next_block_for_io = |
| map_bh->b_blocknr << sdio->blkfactor; |
| if (buffer_new(map_bh)) { |
| clean_bdev_aliases( |
| map_bh->b_bdev, |
| map_bh->b_blocknr, |
| map_bh->b_size >> i_blkbits); |
| } |
| |
| if (!sdio->blkfactor) |
| goto do_holes; |
| |
| blkmask = (1 << sdio->blkfactor) - 1; |
| dio_remainder = (sdio->block_in_file & blkmask); |
| |
| /* |
| * If we are at the start of IO and that IO |
| * starts partway into a fs-block, |
| * dio_remainder will be non-zero. If the IO |
| * is a read then we can simply advance the IO |
| * cursor to the first block which is to be |
| * read. But if the IO is a write and the |
| * block was newly allocated we cannot do that; |
| * the start of the fs block must be zeroed out |
| * on-disk |
| */ |
| if (!buffer_new(map_bh)) |
| sdio->next_block_for_io += dio_remainder; |
| sdio->blocks_available -= dio_remainder; |
| } |
| do_holes: |
| /* Handle holes */ |
| if (!buffer_mapped(map_bh)) { |
| loff_t i_size_aligned; |
| |
| /* AKPM: eargh, -ENOTBLK is a hack */ |
| if (dio->op == REQ_OP_WRITE) { |
| put_page(page); |
| return -ENOTBLK; |
| } |
| |
| /* |
| * Be sure to account for a partial block as the |
| * last block in the file |
| */ |
| i_size_aligned = ALIGN(i_size_read(dio->inode), |
| 1 << blkbits); |
| if (sdio->block_in_file >= |
| i_size_aligned >> blkbits) { |
| /* We hit eof */ |
| put_page(page); |
| goto out; |
| } |
| zero_user(page, from, 1 << blkbits); |
| sdio->block_in_file++; |
| from += 1 << blkbits; |
| dio->result += 1 << blkbits; |
| goto next_block; |
| } |
| |
| /* |
| * If we're performing IO which has an alignment which |
| * is finer than the underlying fs, go check to see if |
| * we must zero out the start of this block. |
| */ |
| if (unlikely(sdio->blkfactor && !sdio->start_zero_done)) |
| dio_zero_block(dio, sdio, 0, map_bh); |
| |
| /* |
| * Work out, in this_chunk_blocks, how much disk we |
| * can add to this page |
| */ |
| this_chunk_blocks = sdio->blocks_available; |
| u = (to - from) >> blkbits; |
| if (this_chunk_blocks > u) |
| this_chunk_blocks = u; |
| u = sdio->final_block_in_request - sdio->block_in_file; |
| if (this_chunk_blocks > u) |
| this_chunk_blocks = u; |
| this_chunk_bytes = this_chunk_blocks << blkbits; |
| BUG_ON(this_chunk_bytes == 0); |
| |
| if (this_chunk_blocks == sdio->blocks_available) |
| sdio->boundary = buffer_boundary(map_bh); |
| ret = submit_page_section(dio, sdio, page, |
| from, |
| this_chunk_bytes, |
| sdio->next_block_for_io, |
| map_bh); |
| if (ret) { |
| put_page(page); |
| goto out; |
| } |
| sdio->next_block_for_io += this_chunk_blocks; |
| |
| sdio->block_in_file += this_chunk_blocks; |
| from += this_chunk_bytes; |
| dio->result += this_chunk_bytes; |
| sdio->blocks_available -= this_chunk_blocks; |
| next_block: |
| BUG_ON(sdio->block_in_file > sdio->final_block_in_request); |
| if (sdio->block_in_file == sdio->final_block_in_request) |
| break; |
| } |
| |
| /* Drop the ref which was taken in get_user_pages() */ |
| put_page(page); |
| } |
| out: |
| return ret; |
| } |
| |
| static inline int drop_refcount(struct dio *dio) |
| { |
| int ret2; |
| unsigned long flags; |
| |
| /* |
| * Sync will always be dropping the final ref and completing the |
| * operation. AIO can if it was a broken operation described above or |
| * in fact if all the bios race to complete before we get here. In |
| * that case dio_complete() translates the EIOCBQUEUED into the proper |
| * return code that the caller will hand to ->complete(). |
| * |
| * This is managed by the bio_lock instead of being an atomic_t so that |
| * completion paths can drop their ref and use the remaining count to |
| * decide to wake the submission path atomically. |
| */ |
| spin_lock_irqsave(&dio->bio_lock, flags); |
| ret2 = --dio->refcount; |
| spin_unlock_irqrestore(&dio->bio_lock, flags); |
| return ret2; |
| } |
| |
| /* |
| * This is a library function for use by filesystem drivers. |
| * |
| * The locking rules are governed by the flags parameter: |
| * - if the flags value contains DIO_LOCKING we use a fancy locking |
| * scheme for dumb filesystems. |
| * For writes this function is called under i_mutex and returns with |
| * i_mutex held, for reads, i_mutex is not held on entry, but it is |
| * taken and dropped again before returning. |
| * - if the flags value does NOT contain DIO_LOCKING we don't use any |
| * internal locking but rather rely on the filesystem to synchronize |
| * direct I/O reads/writes versus each other and truncate. |
| * |
| * To help with locking against truncate we incremented the i_dio_count |
| * counter before starting direct I/O, and decrement it once we are done. |
| * Truncate can wait for it to reach zero to provide exclusion. It is |
| * expected that filesystem provide exclusion between new direct I/O |
| * and truncates. For DIO_LOCKING filesystems this is done by i_mutex, |
| * but other filesystems need to take care of this on their own. |
| * |
| * NOTE: if you pass "sdio" to anything by pointer make sure that function |
| * is always inlined. Otherwise gcc is unable to split the structure into |
| * individual fields and will generate much worse code. This is important |
| * for the whole file. |
| */ |
| static inline ssize_t |
| do_blockdev_direct_IO(struct kiocb *iocb, struct inode *inode, |
| struct block_device *bdev, struct iov_iter *iter, |
| get_block_t get_block, dio_iodone_t end_io, |
| dio_submit_t submit_io, int flags) |
| { |
| unsigned i_blkbits = READ_ONCE(inode->i_blkbits); |
| unsigned blkbits = i_blkbits; |
| unsigned blocksize_mask = (1 << blkbits) - 1; |
| ssize_t retval = -EINVAL; |
| const size_t count = iov_iter_count(iter); |
| loff_t offset = iocb->ki_pos; |
| const loff_t end = offset + count; |
| struct dio *dio; |
| struct dio_submit sdio = { 0, }; |
| struct buffer_head map_bh = { 0, }; |
| struct blk_plug plug; |
| unsigned long align = offset | iov_iter_alignment(iter); |
| |
| /* |
| * Avoid references to bdev if not absolutely needed to give |
| * the early prefetch in the caller enough time. |
| */ |
| |
| if (align & blocksize_mask) { |
| if (bdev) |
| blkbits = blksize_bits(bdev_logical_block_size(bdev)); |
| blocksize_mask = (1 << blkbits) - 1; |
| if (align & blocksize_mask) |
| goto out; |
| } |
| |
| /* watch out for a 0 len io from a tricksy fs */ |
| if (iov_iter_rw(iter) == READ && !count) |
| return 0; |
| |
| dio = kmem_cache_alloc(dio_cache, GFP_KERNEL); |
| retval = -ENOMEM; |
| if (!dio) |
| goto out; |
| /* |
| * Believe it or not, zeroing out the page array caused a .5% |
| * performance regression in a database benchmark. So, we take |
| * care to only zero out what's needed. |
| */ |
| memset(dio, 0, offsetof(struct dio, pages)); |
| |
| dio->flags = flags; |
| if (dio->flags & DIO_LOCKING) { |
| if (iov_iter_rw(iter) == READ) { |
| struct address_space *mapping = |
| iocb->ki_filp->f_mapping; |
| |
| /* will be released by direct_io_worker */ |
| inode_lock(inode); |
| |
| retval = filemap_write_and_wait_range(mapping, offset, |
| end - 1); |
| if (retval) { |
| inode_unlock(inode); |
| kmem_cache_free(dio_cache, dio); |
| goto out; |
| } |
| } |
| } |
| |
| /* Once we sampled i_size check for reads beyond EOF */ |
| dio->i_size = i_size_read(inode); |
| if (iov_iter_rw(iter) == READ && offset >= dio->i_size) { |
| if (dio->flags & DIO_LOCKING) |
| inode_unlock(inode); |
| kmem_cache_free(dio_cache, dio); |
| retval = 0; |
| goto out; |
| } |
| |
| /* |
| * For file extending writes updating i_size before data writeouts |
| * complete can expose uninitialized blocks in dumb filesystems. |
| * In that case we need to wait for I/O completion even if asked |
| * for an asynchronous write. |
| */ |
| if (is_sync_kiocb(iocb)) |
| dio->is_async = false; |
| else if (iov_iter_rw(iter) == WRITE && end > i_size_read(inode)) |
| dio->is_async = false; |
| else |
| dio->is_async = true; |
| |
| dio->inode = inode; |
| if (iov_iter_rw(iter) == WRITE) { |
| dio->op = REQ_OP_WRITE; |
| dio->op_flags = REQ_SYNC | REQ_IDLE; |
| if (iocb->ki_flags & IOCB_NOWAIT) |
| dio->op_flags |= REQ_NOWAIT; |
| } else { |
| dio->op = REQ_OP_READ; |
| } |
| if (iocb->ki_flags & IOCB_HIPRI) |
| dio->op_flags |= REQ_HIPRI; |
| |
| /* |
| * For AIO O_(D)SYNC writes we need to defer completions to a workqueue |
| * so that we can call ->fsync. |
| */ |
| if (dio->is_async && iov_iter_rw(iter) == WRITE) { |
| retval = 0; |
| if (iocb->ki_flags & IOCB_DSYNC) |
| retval = dio_set_defer_completion(dio); |
| else if (!dio->inode->i_sb->s_dio_done_wq) { |
| /* |
| * In case of AIO write racing with buffered read we |
| * need to defer completion. We can't decide this now, |
| * however the workqueue needs to be initialized here. |
| */ |
| retval = sb_init_dio_done_wq(dio->inode->i_sb); |
| } |
| if (retval) { |
| /* |
| * We grab i_mutex only for reads so we don't have |
| * to release it here |
| */ |
| kmem_cache_free(dio_cache, dio); |
| goto out; |
| } |
| } |
| |
| /* |
| * Will be decremented at I/O completion time. |
| */ |
| inode_dio_begin(inode); |
| |
| retval = 0; |
| sdio.blkbits = blkbits; |
| sdio.blkfactor = i_blkbits - blkbits; |
| sdio.block_in_file = offset >> blkbits; |
| |
| sdio.get_block = get_block; |
| dio->end_io = end_io; |
| sdio.submit_io = submit_io; |
| sdio.final_block_in_bio = -1; |
| sdio.next_block_for_io = -1; |
| |
| dio->iocb = iocb; |
| |
| spin_lock_init(&dio->bio_lock); |
| dio->refcount = 1; |
| |
| dio->should_dirty = iter_is_iovec(iter) && iov_iter_rw(iter) == READ; |
| sdio.iter = iter; |
| sdio.final_block_in_request = end >> blkbits; |
| |
| /* |
| * In case of non-aligned buffers, we may need 2 more |
| * pages since we need to zero out first and last block. |
| */ |
| if (unlikely(sdio.blkfactor)) |
| sdio.pages_in_io = 2; |
| |
| sdio.pages_in_io += iov_iter_npages(iter, INT_MAX); |
| |
| blk_start_plug(&plug); |
| |
| retval = do_direct_IO(dio, &sdio, &map_bh); |
| if (retval) |
| dio_cleanup(dio, &sdio); |
| |
| if (retval == -ENOTBLK) { |
| /* |
| * The remaining part of the request will be |
| * be handled by buffered I/O when we return |
| */ |
| retval = 0; |
| } |
| /* |
| * There may be some unwritten disk at the end of a part-written |
| * fs-block-sized block. Go zero that now. |
| */ |
| dio_zero_block(dio, &sdio, 1, &map_bh); |
| |
| if (sdio.cur_page) { |
| ssize_t ret2; |
| |
| ret2 = dio_send_cur_page(dio, &sdio, &map_bh); |
| if (retval == 0) |
| retval = ret2; |
| put_page(sdio.cur_page); |
| sdio.cur_page = NULL; |
| } |
| if (sdio.bio) |
| dio_bio_submit(dio, &sdio); |
| |
| blk_finish_plug(&plug); |
| |
| /* |
| * It is possible that, we return short IO due to end of file. |
| * In that case, we need to release all the pages we got hold on. |
| */ |
| dio_cleanup(dio, &sdio); |
| |
| /* |
| * All block lookups have been performed. For READ requests |
| * we can let i_mutex go now that its achieved its purpose |
| * of protecting us from looking up uninitialized blocks. |
| */ |
| if (iov_iter_rw(iter) == READ && (dio->flags & DIO_LOCKING)) |
| inode_unlock(dio->inode); |
| |
| /* |
| * The only time we want to leave bios in flight is when a successful |
| * partial aio read or full aio write have been setup. In that case |
| * bio completion will call aio_complete. The only time it's safe to |
| * call aio_complete is when we return -EIOCBQUEUED, so we key on that. |
| * This had *better* be the only place that raises -EIOCBQUEUED. |
| */ |
| BUG_ON(retval == -EIOCBQUEUED); |
| if (dio->is_async && retval == 0 && dio->result && |
| (iov_iter_rw(iter) == READ || dio->result == count)) |
| retval = -EIOCBQUEUED; |
| else |
| dio_await_completion(dio); |
| |
| if (drop_refcount(dio) == 0) { |
| retval = dio_complete(dio, retval, DIO_COMPLETE_INVALIDATE); |
| } else |
| BUG_ON(retval != -EIOCBQUEUED); |
| |
| out: |
| return retval; |
| } |
| |
| ssize_t __blockdev_direct_IO(struct kiocb *iocb, struct inode *inode, |
| struct block_device *bdev, struct iov_iter *iter, |
| get_block_t get_block, |
| dio_iodone_t end_io, dio_submit_t submit_io, |
| int flags) |
| { |
| /* |
| * The block device state is needed in the end to finally |
| * submit everything. Since it's likely to be cache cold |
| * prefetch it here as first thing to hide some of the |
| * latency. |
| * |
| * Attempt to prefetch the pieces we likely need later. |
| */ |
| prefetch(&bdev->bd_disk->part_tbl); |
| prefetch(bdev->bd_queue); |
| prefetch((char *)bdev->bd_queue + SMP_CACHE_BYTES); |
| |
| return do_blockdev_direct_IO(iocb, inode, bdev, iter, get_block, |
| end_io, submit_io, flags); |
| } |
| |
| EXPORT_SYMBOL(__blockdev_direct_IO); |
| |
| static __init int dio_init(void) |
| { |
| dio_cache = KMEM_CACHE(dio, SLAB_PANIC); |
| return 0; |
| } |
| module_init(dio_init) |