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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-11 08:27:49 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-11 08:27:49 +0000
commitace9429bb58fd418f0c81d4c2835699bddf6bde6 (patch)
treeb2d64bc10158fdd5497876388cd68142ca374ed3 /fs/iomap/direct-io.c
parentInitial commit. (diff)
downloadlinux-ace9429bb58fd418f0c81d4c2835699bddf6bde6.tar.xz
linux-ace9429bb58fd418f0c81d4c2835699bddf6bde6.zip
Adding upstream version 6.6.15.upstream/6.6.15
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'fs/iomap/direct-io.c')
-rw-r--r--fs/iomap/direct-io.c754
1 files changed, 754 insertions, 0 deletions
diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
new file mode 100644
index 0000000000..bcd3f8cf5e
--- /dev/null
+++ b/fs/iomap/direct-io.c
@@ -0,0 +1,754 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2010 Red Hat, Inc.
+ * Copyright (c) 2016-2021 Christoph Hellwig.
+ */
+#include <linux/module.h>
+#include <linux/compiler.h>
+#include <linux/fs.h>
+#include <linux/fscrypt.h>
+#include <linux/pagemap.h>
+#include <linux/iomap.h>
+#include <linux/backing-dev.h>
+#include <linux/uio.h>
+#include <linux/task_io_accounting_ops.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_CALLER_COMP (1U << 26)
+#define IOMAP_DIO_INLINE_COMP (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
+ 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))
+ 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 ssize_t iomap_dio_deferred_complete(void *data)
+{
+ return iomap_dio_complete(data);
+}
+
+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);
+}
+
+void iomap_dio_bio_end_io(struct bio *bio)
+{
+ struct iomap_dio *dio = bio->bi_private;
+ bool should_dirty = (dio->flags & IOMAP_DIO_DIRTY);
+ struct kiocb *iocb = dio->iocb;
+
+ if (bio->bi_status)
+ iomap_dio_set_error(dio, blk_status_to_errno(bio->bi_status));
+ if (!atomic_dec_and_test(&dio->ref))
+ goto release_bio;
+
+ /*
+ * Synchronous dio, task itself will handle any completion work
+ * that needs after IO. All we need to do is wake the task.
+ */
+ if (dio->wait_for_completion) {
+ struct task_struct *waiter = dio->submit.waiter;
+
+ WRITE_ONCE(dio->submit.waiter, NULL);
+ blk_wake_io_task(waiter);
+ goto release_bio;
+ }
+
+ /*
+ * Flagged with IOMAP_DIO_INLINE_COMP, we can complete it inline
+ */
+ if (dio->flags & IOMAP_DIO_INLINE_COMP) {
+ WRITE_ONCE(iocb->private, NULL);
+ iomap_dio_complete_work(&dio->aio.work);
+ goto release_bio;
+ }
+
+ /*
+ * If this dio is flagged with IOMAP_DIO_CALLER_COMP, then schedule
+ * our completion that way to avoid an async punt to a workqueue.
+ */
+ if (dio->flags & IOMAP_DIO_CALLER_COMP) {
+ /* only polled IO cares about private cleared */
+ iocb->private = dio;
+ iocb->dio_complete = iomap_dio_deferred_complete;
+
+ /*
+ * Invoke ->ki_complete() directly. We've assigned our
+ * dio_complete callback handler, and since the issuer set
+ * IOCB_DIO_CALLER_COMP, we know their ki_complete handler will
+ * notice ->dio_complete being set and will defer calling that
+ * handler until it can be done from a safe task context.
+ *
+ * Note that the 'res' being passed in here is not important
+ * for this case. The actual completion value of the request
+ * will be gotten from dio_complete when that is run by the
+ * issuer.
+ */
+ iocb->ki_complete(iocb, 0);
+ goto release_bio;
+ }
+
+ /*
+ * 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(file_inode(iocb->ki_filp)->i_sb->s_dio_done_wq,
+ &dio->aio.work);
+release_bio:
+ 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);
+
+static void 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 page *page = ZERO_PAGE(0);
+ struct bio *bio;
+
+ bio = iomap_dio_alloc_bio(iter, dio, 1, 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;
+
+ __bio_add_page(bio, page, len, 0);
+ iomap_dio_submit_bio(iter, dio, bio, pos);
+}
+
+/*
+ * Figure out the bio's operation flags from the dio request, the
+ * mapping, and whether or not we want FUA. Note that we can end up
+ * clearing the WRITE_THROUGH flag in the dio request.
+ */
+static inline blk_opf_t iomap_dio_bio_opflags(struct iomap_dio *dio,
+ const struct iomap *iomap, bool use_fua)
+{
+ blk_opf_t opflags = REQ_SYNC | REQ_IDLE;
+
+ if (!(dio->flags & IOMAP_DIO_WRITE))
+ return REQ_OP_READ;
+
+ opflags |= REQ_OP_WRITE;
+ if (use_fua)
+ opflags |= REQ_FUA;
+ else
+ dio->flags &= ~IOMAP_DIO_WRITE_THROUGH;
+
+ return opflags;
+}
+
+static loff_t iomap_dio_bio_iter(const 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;
+ loff_t length = iomap_length(iter);
+ loff_t pos = iter->pos;
+ blk_opf_t bio_opf;
+ struct bio *bio;
+ bool need_zeroout = false;
+ bool use_fua = false;
+ int nr_pages, ret = 0;
+ size_t copied = 0;
+ size_t orig_count;
+
+ if ((pos | length) & (bdev_logical_block_size(iomap->bdev) - 1) ||
+ !bdev_iter_is_aligned(iomap->bdev, dio->submit.iter))
+ return -EINVAL;
+
+ if (iomap->type == IOMAP_UNWRITTEN) {
+ dio->flags |= IOMAP_DIO_UNWRITTEN;
+ need_zeroout = true;
+ }
+
+ if (iomap->flags & IOMAP_F_SHARED)
+ dio->flags |= IOMAP_DIO_COW;
+
+ if (iomap->flags & IOMAP_F_NEW) {
+ need_zeroout = true;
+ } else if (iomap->type == IOMAP_MAPPED) {
+ /*
+ * Use a FUA write if we need datasync semantics, this is a pure
+ * data IO that doesn't require any metadata updates (including
+ * after IO completion such as unwritten extent conversion) and
+ * the underlying device either supports FUA or doesn't have
+ * a volatile write cache. This allows us to avoid cache flushes
+ * on IO completion. If we can't use writethrough and need to
+ * sync, disable in-task completions as dio completion will
+ * need to call generic_write_sync() which will do a blocking
+ * fsync / cache flush call.
+ */
+ if (!(iomap->flags & (IOMAP_F_SHARED|IOMAP_F_DIRTY)) &&
+ (dio->flags & IOMAP_DIO_WRITE_THROUGH) &&
+ (bdev_fua(iomap->bdev) || !bdev_write_cache(iomap->bdev)))
+ use_fua = true;
+ else if (dio->flags & IOMAP_DIO_NEED_SYNC)
+ dio->flags &= ~IOMAP_DIO_CALLER_COMP;
+ }
+
+ /*
+ * 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;
+
+ /*
+ * We can only do deferred completion for pure overwrites that
+ * don't require additional IO at completion. This rules out
+ * writes that need zeroing or extent conversion, extend
+ * the file size, or issue journal IO or cache flushes
+ * during completion processing.
+ */
+ if (need_zeroout ||
+ ((dio->flags & IOMAP_DIO_NEED_SYNC) && !use_fua) ||
+ ((dio->flags & IOMAP_DIO_WRITE) && pos >= i_size_read(inode)))
+ dio->flags &= ~IOMAP_DIO_CALLER_COMP;
+
+ /*
+ * 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_INLINE_COMP|IOMAP_DIO_CALLER_COMP)))
+ 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);
+ if (pad)
+ iomap_dio_zero(iter, dio, pos - pad, pad);
+ }
+
+ /*
+ * Set the operation flags early so that bio_iov_iter_get_pages
+ * can set up the page vector appropriately for a ZONE_APPEND
+ * operation.
+ */
+ bio_opf = iomap_dio_bio_opflags(dio, iomap, use_fua);
+
+ 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_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);
+ 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 (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)
+ 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 copied;
+ return ret;
+}
+
+static loff_t iomap_dio_hole_iter(const 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 length;
+}
+
+static loff_t iomap_dio_inline_iter(const 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;
+ size_t copied;
+
+ 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 copied;
+}
+
+static loff_t iomap_dio_iter(const 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 (iov_iter_rw(iter) == READ) {
+ /* reads can always complete inline */
+ dio->flags |= IOMAP_DIO_INLINE_COMP;
+
+ 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;
+
+ /*
+ * Flag as supporting deferred completions, if the issuer
+ * groks it. This can avoid a workqueue punt for writes.
+ * We may later clear this flag if we need to do other IO
+ * as part of this IO completion.
+ */
+ if (iocb->ki_flags & IOCB_DIO_CALLER_COMP)
+ dio->flags |= IOMAP_DIO_CALLER_COMP;
+
+ 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;
+ }
+
+ /* 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;
+ }
+
+ /*
+ * 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);
+ 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.processed = 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.
+ */
+ if (dio->flags & IOMAP_DIO_WRITE_THROUGH)
+ dio->flags &= ~IOMAP_DIO_NEED_SYNC;
+
+ /*
+ * 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);