diff options
Diffstat (limited to 'fs/iomap/direct-io.c')
| -rw-r--r-- | fs/iomap/direct-io.c | 853 |
1 files changed, 853 insertions, 0 deletions
diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c new file mode 100644 index 000000000000..8e273408453a --- /dev/null +++ b/fs/iomap/direct-io.c @@ -0,0 +1,853 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) 2010 Red Hat, Inc. + * Copyright (c) 2016-2025 Christoph Hellwig. + */ +#include <linux/fscrypt.h> +#include <linux/pagemap.h> +#include <linux/iomap.h> +#include <linux/task_io_accounting_ops.h> +#include "internal.h" +#include "trace.h" + +#include "../internal.h" + +/* + * Private flags for iomap_dio, must not overlap with the public ones in + * iomap.h: + */ +#define IOMAP_DIO_NO_INVALIDATE (1U << 26) +#define IOMAP_DIO_COMP_WORK (1U << 27) +#define IOMAP_DIO_WRITE_THROUGH (1U << 28) +#define IOMAP_DIO_NEED_SYNC (1U << 29) +#define IOMAP_DIO_WRITE (1U << 30) +#define IOMAP_DIO_DIRTY (1U << 31) + +struct iomap_dio { + struct kiocb *iocb; + const struct iomap_dio_ops *dops; + loff_t i_size; + loff_t size; + atomic_t ref; + unsigned flags; + int error; + size_t done_before; + bool wait_for_completion; + + union { + /* used during submission and for synchronous completion: */ + struct { + struct iov_iter *iter; + struct task_struct *waiter; + } submit; + + /* used for aio completion: */ + struct { + struct work_struct work; + } aio; + }; +}; + +static struct bio *iomap_dio_alloc_bio(const struct iomap_iter *iter, + struct iomap_dio *dio, unsigned short nr_vecs, blk_opf_t opf) +{ + if (dio->dops && dio->dops->bio_set) + return bio_alloc_bioset(iter->iomap.bdev, nr_vecs, opf, + GFP_KERNEL, dio->dops->bio_set); + return bio_alloc(iter->iomap.bdev, nr_vecs, opf, GFP_KERNEL); +} + +static void iomap_dio_submit_bio(const struct iomap_iter *iter, + struct iomap_dio *dio, struct bio *bio, loff_t pos) +{ + struct kiocb *iocb = dio->iocb; + + atomic_inc(&dio->ref); + + /* Sync dio can't be polled reliably */ + if ((iocb->ki_flags & IOCB_HIPRI) && !is_sync_kiocb(iocb)) { + bio_set_polled(bio, iocb); + WRITE_ONCE(iocb->private, bio); + } + + if (dio->dops && dio->dops->submit_io) { + dio->dops->submit_io(iter, bio, pos); + } else { + WARN_ON_ONCE(iter->iomap.flags & IOMAP_F_ANON_WRITE); + submit_bio(bio); + } +} + +ssize_t iomap_dio_complete(struct iomap_dio *dio) +{ + const struct iomap_dio_ops *dops = dio->dops; + struct kiocb *iocb = dio->iocb; + loff_t offset = iocb->ki_pos; + ssize_t ret = dio->error; + + if (dops && dops->end_io) + ret = dops->end_io(iocb, dio->size, ret, dio->flags); + + if (likely(!ret)) { + ret = dio->size; + /* check for short read */ + if (offset + ret > dio->i_size && + !(dio->flags & IOMAP_DIO_WRITE)) + ret = dio->i_size - offset; + } + + /* + * 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 ->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 (!dio->error && dio->size && (dio->flags & IOMAP_DIO_WRITE) && + !(dio->flags & IOMAP_DIO_NO_INVALIDATE)) + kiocb_invalidate_post_direct_write(iocb, dio->size); + + inode_dio_end(file_inode(iocb->ki_filp)); + + if (ret > 0) { + iocb->ki_pos += ret; + + /* + * If this is a DSYNC write, make sure we push it to stable + * storage now that we've written data. + */ + if (dio->flags & IOMAP_DIO_NEED_SYNC) + ret = generic_write_sync(iocb, ret); + if (ret > 0) + ret += dio->done_before; + } + trace_iomap_dio_complete(iocb, dio->error, ret); + kfree(dio); + return ret; +} +EXPORT_SYMBOL_GPL(iomap_dio_complete); + +static void iomap_dio_complete_work(struct work_struct *work) +{ + struct iomap_dio *dio = container_of(work, struct iomap_dio, aio.work); + struct kiocb *iocb = dio->iocb; + + iocb->ki_complete(iocb, iomap_dio_complete(dio)); +} + +/* + * Set an error in the dio if none is set yet. We have to use cmpxchg + * as the submission context and the completion context(s) can race to + * update the error. + */ +static inline void iomap_dio_set_error(struct iomap_dio *dio, int ret) +{ + cmpxchg(&dio->error, 0, ret); +} + +/* + * Called when dio->ref reaches zero from an I/O completion. + */ +static void iomap_dio_done(struct iomap_dio *dio) +{ + struct kiocb *iocb = dio->iocb; + + if (dio->wait_for_completion) { + /* + * Synchronous I/O, task itself will handle any completion work + * that needs after IO. All we need to do is wake the task. + */ + struct task_struct *waiter = dio->submit.waiter; + + WRITE_ONCE(dio->submit.waiter, NULL); + blk_wake_io_task(waiter); + return; + } + + /* + * Always run error completions in user context. These are not + * performance critical and some code relies on taking sleeping locks + * for error handling. + */ + if (dio->error) + dio->flags |= IOMAP_DIO_COMP_WORK; + + /* + * Never invalidate pages from this context to avoid deadlocks with + * buffered I/O completions when called from the ioend workqueue, + * or avoid sleeping when called directly from ->bi_end_io. + * Tough luck if you hit the tiny race with someone dirtying the range + * right between this check and the actual completion. + */ + if ((dio->flags & IOMAP_DIO_WRITE) && + !(dio->flags & IOMAP_DIO_COMP_WORK)) { + if (dio->iocb->ki_filp->f_mapping->nrpages) + dio->flags |= IOMAP_DIO_COMP_WORK; + else + dio->flags |= IOMAP_DIO_NO_INVALIDATE; + } + + if (dio->flags & IOMAP_DIO_COMP_WORK) { + struct inode *inode = file_inode(iocb->ki_filp); + + /* + * Async DIO completion that requires filesystem level + * completion work gets punted to a work queue to complete as + * the operation may require more IO to be issued to finalise + * filesystem metadata changes or guarantee data integrity. + */ + INIT_WORK(&dio->aio.work, iomap_dio_complete_work); + queue_work(inode->i_sb->s_dio_done_wq, &dio->aio.work); + return; + } + + WRITE_ONCE(iocb->private, NULL); + iomap_dio_complete_work(&dio->aio.work); +} + +void iomap_dio_bio_end_io(struct bio *bio) +{ + struct iomap_dio *dio = bio->bi_private; + bool should_dirty = (dio->flags & IOMAP_DIO_DIRTY); + + if (bio->bi_status) + iomap_dio_set_error(dio, blk_status_to_errno(bio->bi_status)); + + if (atomic_dec_and_test(&dio->ref)) + iomap_dio_done(dio); + + if (should_dirty) { + bio_check_pages_dirty(bio); + } else { + bio_release_pages(bio, false); + bio_put(bio); + } +} +EXPORT_SYMBOL_GPL(iomap_dio_bio_end_io); + +u32 iomap_finish_ioend_direct(struct iomap_ioend *ioend) +{ + struct iomap_dio *dio = ioend->io_bio.bi_private; + bool should_dirty = (dio->flags & IOMAP_DIO_DIRTY); + u32 vec_count = ioend->io_bio.bi_vcnt; + + if (ioend->io_error) + iomap_dio_set_error(dio, ioend->io_error); + + if (atomic_dec_and_test(&dio->ref)) { + /* + * Try to avoid another context switch for the completion given + * that we are already called from the ioend completion + * workqueue. + */ + dio->flags &= ~IOMAP_DIO_COMP_WORK; + iomap_dio_done(dio); + } + + if (should_dirty) { + bio_check_pages_dirty(&ioend->io_bio); + } else { + bio_release_pages(&ioend->io_bio, false); + bio_put(&ioend->io_bio); + } + + /* + * Return the number of bvecs completed as even direct I/O completions + * do significant per-folio work and we'll still want to give up the + * CPU after a lot of completions. + */ + return vec_count; +} + +static int iomap_dio_zero(const struct iomap_iter *iter, struct iomap_dio *dio, + loff_t pos, unsigned len) +{ + struct inode *inode = file_inode(dio->iocb->ki_filp); + struct bio *bio; + struct folio *zero_folio = largest_zero_folio(); + int nr_vecs = max(1, i_blocksize(inode) / folio_size(zero_folio)); + + if (!len) + return 0; + + /* + * This limit shall never be reached as most filesystems have a + * maximum blocksize of 64k. + */ + if (WARN_ON_ONCE(nr_vecs > BIO_MAX_VECS)) + return -EINVAL; + + bio = iomap_dio_alloc_bio(iter, dio, nr_vecs, + REQ_OP_WRITE | REQ_SYNC | REQ_IDLE); + fscrypt_set_bio_crypt_ctx(bio, inode, pos >> inode->i_blkbits, + GFP_KERNEL); + bio->bi_iter.bi_sector = iomap_sector(&iter->iomap, pos); + bio->bi_private = dio; + bio->bi_end_io = iomap_dio_bio_end_io; + + while (len > 0) { + unsigned int io_len = min(len, folio_size(zero_folio)); + + bio_add_folio_nofail(bio, zero_folio, io_len, 0); + len -= io_len; + } + iomap_dio_submit_bio(iter, dio, bio, pos); + + return 0; +} + +static int iomap_dio_bio_iter(struct iomap_iter *iter, struct iomap_dio *dio) +{ + const struct iomap *iomap = &iter->iomap; + struct inode *inode = iter->inode; + unsigned int fs_block_size = i_blocksize(inode), pad; + const loff_t length = iomap_length(iter); + loff_t pos = iter->pos; + blk_opf_t bio_opf = REQ_SYNC | REQ_IDLE; + struct bio *bio; + bool need_zeroout = false; + int nr_pages, ret = 0; + u64 copied = 0; + size_t orig_count; + unsigned int alignment; + + /* + * File systems that write out of place and always allocate new blocks + * need each bio to be block aligned as that's the unit of allocation. + */ + if (dio->flags & IOMAP_DIO_FSBLOCK_ALIGNED) + alignment = fs_block_size; + else + alignment = bdev_logical_block_size(iomap->bdev); + + if ((pos | length) & (alignment - 1)) + return -EINVAL; + + if (dio->flags & IOMAP_DIO_WRITE) { + bool need_completion_work = true; + + switch (iomap->type) { + case IOMAP_MAPPED: + /* + * Directly mapped I/O does not inherently need to do + * work at I/O completion time. But there are various + * cases below where this will get set again. + */ + need_completion_work = false; + break; + case IOMAP_UNWRITTEN: + dio->flags |= IOMAP_DIO_UNWRITTEN; + need_zeroout = true; + break; + default: + break; + } + + if (iomap->flags & IOMAP_F_ATOMIC_BIO) { + /* + * Ensure that the mapping covers the full write + * length, otherwise it won't be submitted as a single + * bio, which is required to use hardware atomics. + */ + if (length != iter->len) + return -EINVAL; + bio_opf |= REQ_ATOMIC; + } + + if (iomap->flags & IOMAP_F_SHARED) { + /* + * Unsharing of needs to update metadata at I/O + * completion time. + */ + need_completion_work = true; + dio->flags |= IOMAP_DIO_COW; + } + + if (iomap->flags & IOMAP_F_NEW) { + /* + * Newly allocated blocks might need recording in + * metadata at I/O completion time. + */ + need_completion_work = true; + need_zeroout = true; + } + + /* + * Use a FUA write if we need datasync semantics and this is a + * pure overwrite that doesn't require any metadata updates. + * + * This allows us to avoid cache flushes on I/O completion. + */ + if (dio->flags & IOMAP_DIO_WRITE_THROUGH) { + if (!need_completion_work && + !(iomap->flags & IOMAP_F_DIRTY) && + (!bdev_write_cache(iomap->bdev) || + bdev_fua(iomap->bdev))) + bio_opf |= REQ_FUA; + else + dio->flags &= ~IOMAP_DIO_WRITE_THROUGH; + } + + /* + * We can only do inline completion for pure overwrites that + * don't require additional I/O at completion time. + * + * This rules out writes that need zeroing or metdata updates to + * convert unwritten or shared extents. + * + * Writes that extend i_size are also not supported, but this is + * handled in __iomap_dio_rw(). + */ + if (need_completion_work) + dio->flags |= IOMAP_DIO_COMP_WORK; + + bio_opf |= REQ_OP_WRITE; + } else { + bio_opf |= REQ_OP_READ; + } + + /* + * Save the original count and trim the iter to just the extent we + * are operating on right now. The iter will be re-expanded once + * we are done. + */ + orig_count = iov_iter_count(dio->submit.iter); + iov_iter_truncate(dio->submit.iter, length); + + if (!iov_iter_count(dio->submit.iter)) + goto out; + + /* + * The rules for polled IO completions follow the guidelines as the + * ones we set for inline and deferred completions. If none of those + * are available for this IO, clear the polled flag. + */ + if (dio->flags & IOMAP_DIO_COMP_WORK) + dio->iocb->ki_flags &= ~IOCB_HIPRI; + + if (need_zeroout) { + /* zero out from the start of the block to the write offset */ + pad = pos & (fs_block_size - 1); + + ret = iomap_dio_zero(iter, dio, pos - pad, pad); + if (ret) + goto out; + } + + nr_pages = bio_iov_vecs_to_alloc(dio->submit.iter, BIO_MAX_VECS); + do { + size_t n; + if (dio->error) { + iov_iter_revert(dio->submit.iter, copied); + copied = ret = 0; + goto out; + } + + bio = iomap_dio_alloc_bio(iter, dio, nr_pages, bio_opf); + fscrypt_set_bio_crypt_ctx(bio, inode, pos >> inode->i_blkbits, + GFP_KERNEL); + bio->bi_iter.bi_sector = iomap_sector(iomap, pos); + bio->bi_write_hint = inode->i_write_hint; + bio->bi_ioprio = dio->iocb->ki_ioprio; + bio->bi_private = dio; + bio->bi_end_io = iomap_dio_bio_end_io; + + ret = bio_iov_iter_get_pages(bio, dio->submit.iter, + alignment - 1); + if (unlikely(ret)) { + /* + * We have to stop part way through an IO. We must fall + * through to the sub-block tail zeroing here, otherwise + * this short IO may expose stale data in the tail of + * the block we haven't written data to. + */ + bio_put(bio); + goto zero_tail; + } + + n = bio->bi_iter.bi_size; + if (WARN_ON_ONCE((bio_opf & REQ_ATOMIC) && n != length)) { + /* + * An atomic write bio must cover the complete length, + * which it doesn't, so error. We may need to zero out + * the tail (complete FS block), similar to when + * bio_iov_iter_get_pages() returns an error, above. + */ + ret = -EINVAL; + bio_put(bio); + goto zero_tail; + } + if (dio->flags & IOMAP_DIO_WRITE) + task_io_account_write(n); + else if (dio->flags & IOMAP_DIO_DIRTY) + bio_set_pages_dirty(bio); + + dio->size += n; + copied += n; + + nr_pages = bio_iov_vecs_to_alloc(dio->submit.iter, + BIO_MAX_VECS); + /* + * We can only poll for single bio I/Os. + */ + if (nr_pages) + dio->iocb->ki_flags &= ~IOCB_HIPRI; + iomap_dio_submit_bio(iter, dio, bio, pos); + pos += n; + } while (nr_pages); + + /* + * We need to zeroout the tail of a sub-block write if the extent type + * requires zeroing or the write extends beyond EOF. If we don't zero + * the block tail in the latter case, we can expose stale data via mmap + * reads of the EOF block. + */ +zero_tail: + if (need_zeroout || + ((dio->flags & IOMAP_DIO_WRITE) && pos >= i_size_read(inode))) { + /* zero out from the end of the write to the end of the block */ + pad = pos & (fs_block_size - 1); + if (pad) + ret = iomap_dio_zero(iter, dio, pos, + fs_block_size - pad); + } +out: + /* Undo iter limitation to current extent */ + iov_iter_reexpand(dio->submit.iter, orig_count - copied); + if (copied) + return iomap_iter_advance(iter, copied); + return ret; +} + +static int iomap_dio_hole_iter(struct iomap_iter *iter, struct iomap_dio *dio) +{ + loff_t length = iov_iter_zero(iomap_length(iter), dio->submit.iter); + + dio->size += length; + if (!length) + return -EFAULT; + return iomap_iter_advance(iter, length); +} + +static int iomap_dio_inline_iter(struct iomap_iter *iomi, struct iomap_dio *dio) +{ + const struct iomap *iomap = &iomi->iomap; + struct iov_iter *iter = dio->submit.iter; + void *inline_data = iomap_inline_data(iomap, iomi->pos); + loff_t length = iomap_length(iomi); + loff_t pos = iomi->pos; + u64 copied; + + if (WARN_ON_ONCE(!inline_data)) + return -EIO; + + if (WARN_ON_ONCE(!iomap_inline_data_valid(iomap))) + return -EIO; + + if (dio->flags & IOMAP_DIO_WRITE) { + loff_t size = iomi->inode->i_size; + + if (pos > size) + memset(iomap_inline_data(iomap, size), 0, pos - size); + copied = copy_from_iter(inline_data, length, iter); + if (copied) { + if (pos + copied > size) + i_size_write(iomi->inode, pos + copied); + mark_inode_dirty(iomi->inode); + } + } else { + copied = copy_to_iter(inline_data, length, iter); + } + dio->size += copied; + if (!copied) + return -EFAULT; + return iomap_iter_advance(iomi, copied); +} + +static int iomap_dio_iter(struct iomap_iter *iter, struct iomap_dio *dio) +{ + switch (iter->iomap.type) { + case IOMAP_HOLE: + if (WARN_ON_ONCE(dio->flags & IOMAP_DIO_WRITE)) + return -EIO; + return iomap_dio_hole_iter(iter, dio); + case IOMAP_UNWRITTEN: + if (!(dio->flags & IOMAP_DIO_WRITE)) + return iomap_dio_hole_iter(iter, dio); + return iomap_dio_bio_iter(iter, dio); + case IOMAP_MAPPED: + return iomap_dio_bio_iter(iter, dio); + case IOMAP_INLINE: + return iomap_dio_inline_iter(iter, dio); + case IOMAP_DELALLOC: + /* + * DIO is not serialised against mmap() access at all, and so + * if the page_mkwrite occurs between the writeback and the + * iomap_iter() call in the DIO path, then it will see the + * DELALLOC block that the page-mkwrite allocated. + */ + pr_warn_ratelimited("Direct I/O collision with buffered writes! File: %pD4 Comm: %.20s\n", + dio->iocb->ki_filp, current->comm); + return -EIO; + default: + WARN_ON_ONCE(1); + return -EIO; + } +} + +/* + * iomap_dio_rw() always completes O_[D]SYNC writes regardless of whether the IO + * is being issued as AIO or not. This allows us to optimise pure data writes + * to use REQ_FUA rather than requiring generic_write_sync() to issue a + * REQ_FLUSH post write. This is slightly tricky because a single request here + * can be mapped into multiple disjoint IOs and only a subset of the IOs issued + * may be pure data writes. In that case, we still need to do a full data sync + * completion. + * + * When page faults are disabled and @dio_flags includes IOMAP_DIO_PARTIAL, + * __iomap_dio_rw can return a partial result if it encounters a non-resident + * page in @iter after preparing a transfer. In that case, the non-resident + * pages can be faulted in and the request resumed with @done_before set to the + * number of bytes previously transferred. The request will then complete with + * the correct total number of bytes transferred; this is essential for + * completing partial requests asynchronously. + * + * Returns -ENOTBLK In case of a page invalidation invalidation failure for + * writes. The callers needs to fall back to buffered I/O in this case. + */ +struct iomap_dio * +__iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter, + const struct iomap_ops *ops, const struct iomap_dio_ops *dops, + unsigned int dio_flags, void *private, size_t done_before) +{ + struct inode *inode = file_inode(iocb->ki_filp); + struct iomap_iter iomi = { + .inode = inode, + .pos = iocb->ki_pos, + .len = iov_iter_count(iter), + .flags = IOMAP_DIRECT, + .private = private, + }; + bool wait_for_completion = + is_sync_kiocb(iocb) || (dio_flags & IOMAP_DIO_FORCE_WAIT); + struct blk_plug plug; + struct iomap_dio *dio; + loff_t ret = 0; + + trace_iomap_dio_rw_begin(iocb, iter, dio_flags, done_before); + + if (!iomi.len) + return NULL; + + dio = kmalloc(sizeof(*dio), GFP_KERNEL); + if (!dio) + return ERR_PTR(-ENOMEM); + + dio->iocb = iocb; + atomic_set(&dio->ref, 1); + dio->size = 0; + dio->i_size = i_size_read(inode); + dio->dops = dops; + dio->error = 0; + dio->flags = 0; + dio->done_before = done_before; + + dio->submit.iter = iter; + dio->submit.waiter = current; + + if (iocb->ki_flags & IOCB_NOWAIT) + iomi.flags |= IOMAP_NOWAIT; + + if (dio_flags & IOMAP_DIO_FSBLOCK_ALIGNED) + dio->flags |= IOMAP_DIO_FSBLOCK_ALIGNED; + + if (iov_iter_rw(iter) == READ) { + if (iomi.pos >= dio->i_size) + goto out_free_dio; + + if (user_backed_iter(iter)) + dio->flags |= IOMAP_DIO_DIRTY; + + ret = kiocb_write_and_wait(iocb, iomi.len); + if (ret) + goto out_free_dio; + } else { + iomi.flags |= IOMAP_WRITE; + dio->flags |= IOMAP_DIO_WRITE; + + if (dio_flags & IOMAP_DIO_OVERWRITE_ONLY) { + ret = -EAGAIN; + if (iomi.pos >= dio->i_size || + iomi.pos + iomi.len > dio->i_size) + goto out_free_dio; + iomi.flags |= IOMAP_OVERWRITE_ONLY; + } + + if (iocb->ki_flags & IOCB_ATOMIC) + iomi.flags |= IOMAP_ATOMIC; + + /* for data sync or sync, we need sync completion processing */ + if (iocb_is_dsync(iocb)) { + dio->flags |= IOMAP_DIO_NEED_SYNC; + + /* + * For datasync only writes, we optimistically try using + * WRITE_THROUGH for this IO. This flag requires either + * FUA writes through the device's write cache, or a + * normal write to a device without a volatile write + * cache. For the former, Any non-FUA write that occurs + * will clear this flag, hence we know before completion + * whether a cache flush is necessary. + */ + if (!(iocb->ki_flags & IOCB_SYNC)) + dio->flags |= IOMAP_DIO_WRITE_THROUGH; + } + + /* + * i_size updates must to happen from process context. + */ + if (iomi.pos + iomi.len > dio->i_size) + dio->flags |= IOMAP_DIO_COMP_WORK; + + /* + * Try to invalidate cache pages for the range we are writing. + * If this invalidation fails, let the caller fall back to + * buffered I/O. + */ + ret = kiocb_invalidate_pages(iocb, iomi.len); + if (ret) { + if (ret != -EAGAIN) { + trace_iomap_dio_invalidate_fail(inode, iomi.pos, + iomi.len); + if (iocb->ki_flags & IOCB_ATOMIC) { + /* + * folio invalidation failed, maybe + * this is transient, unlock and see if + * the caller tries again. + */ + ret = -EAGAIN; + } else { + /* fall back to buffered write */ + ret = -ENOTBLK; + } + } + goto out_free_dio; + } + } + + if (!wait_for_completion && !inode->i_sb->s_dio_done_wq) { + ret = sb_init_dio_done_wq(inode->i_sb); + if (ret < 0) + goto out_free_dio; + } + + inode_dio_begin(inode); + + blk_start_plug(&plug); + while ((ret = iomap_iter(&iomi, ops)) > 0) { + iomi.status = iomap_dio_iter(&iomi, dio); + + /* + * We can only poll for single bio I/Os. + */ + iocb->ki_flags &= ~IOCB_HIPRI; + } + + blk_finish_plug(&plug); + + /* + * We only report that we've read data up to i_size. + * Revert iter to a state corresponding to that as some callers (such + * as the splice code) rely on it. + */ + if (iov_iter_rw(iter) == READ && iomi.pos >= dio->i_size) + iov_iter_revert(iter, iomi.pos - dio->i_size); + + if (ret == -EFAULT && dio->size && (dio_flags & IOMAP_DIO_PARTIAL)) { + if (!(iocb->ki_flags & IOCB_NOWAIT)) + wait_for_completion = true; + ret = 0; + } + + /* magic error code to fall back to buffered I/O */ + if (ret == -ENOTBLK) { + wait_for_completion = true; + ret = 0; + } + if (ret < 0) + iomap_dio_set_error(dio, ret); + + /* + * If all the writes we issued were already written through to the + * media, we don't need to flush the cache on IO completion. Clear the + * sync flag for this case. + * + * Otherwise clear the inline completion flag if any sync work is + * needed, as that needs to be performed from process context. + */ + if (dio->flags & IOMAP_DIO_WRITE_THROUGH) + dio->flags &= ~IOMAP_DIO_NEED_SYNC; + else if (dio->flags & IOMAP_DIO_NEED_SYNC) + dio->flags |= IOMAP_DIO_COMP_WORK; + + /* + * We are about to drop our additional submission reference, which + * might be the last reference to the dio. There are three different + * ways we can progress here: + * + * (a) If this is the last reference we will always complete and free + * the dio ourselves. + * (b) If this is not the last reference, and we serve an asynchronous + * iocb, we must never touch the dio after the decrement, the + * I/O completion handler will complete and free it. + * (c) If this is not the last reference, but we serve a synchronous + * iocb, the I/O completion handler will wake us up on the drop + * of the final reference, and we will complete and free it here + * after we got woken by the I/O completion handler. + */ + dio->wait_for_completion = wait_for_completion; + if (!atomic_dec_and_test(&dio->ref)) { + if (!wait_for_completion) { + trace_iomap_dio_rw_queued(inode, iomi.pos, iomi.len); + return ERR_PTR(-EIOCBQUEUED); + } + + for (;;) { + set_current_state(TASK_UNINTERRUPTIBLE); + if (!READ_ONCE(dio->submit.waiter)) + break; + + blk_io_schedule(); + } + __set_current_state(TASK_RUNNING); + } + + return dio; + +out_free_dio: + kfree(dio); + if (ret) + return ERR_PTR(ret); + return NULL; +} +EXPORT_SYMBOL_GPL(__iomap_dio_rw); + +ssize_t +iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter, + const struct iomap_ops *ops, const struct iomap_dio_ops *dops, + unsigned int dio_flags, void *private, size_t done_before) +{ + struct iomap_dio *dio; + + dio = __iomap_dio_rw(iocb, iter, ops, dops, dio_flags, private, + done_before); + if (IS_ERR_OR_NULL(dio)) + return PTR_ERR_OR_ZERO(dio); + return iomap_dio_complete(dio); +} +EXPORT_SYMBOL_GPL(iomap_dio_rw); |