[PATCH 5/9] iomap: move the direct IO code into a separate file

Darrick J. Wong
2019-07-15T18:00:09Z

From: Darrick J. Wong <darrick.wong@oracle.com>

Move the direct IO code into a separate file so that we can group
related functions in a single file instead of having a single enormous
source file.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
fs/iomap.c | 554 ------------------------------------------------
fs/iomap/Makefile | 1
fs/iomap/direct-io.c | 562 +++++++++++++++++++++++++++++++++++++++++++++++++
include/linux/iomap.h | 7 +
4 files changed, 570 insertions(+), 554 deletions(-)
create mode 100644 fs/iomap/direct-io.c

diff --git a/fs/iomap.c b/fs/iomap.c
index ad994c408cb8..c983fedc7081 100644
--- a/fs/iomap.c
+++ b/fs/iomap.c
@@ -90,12 +90,6 @@ iomap_apply(struct inode *inode, loff_t pos, loff_t length, unsigned flags,
return written ? written : ret;
}

-static sector_t
-iomap_sector(struct iomap *iomap, loff_t pos)
-{
- return (iomap->addr + pos - iomap->offset) >> SECTOR_SHIFT;
-}
-
static struct iomap_page *
iomap_page_create(struct inode *inode, struct page *page)
{
@@ -1148,551 +1142,3 @@ vm_fault_t iomap_page_mkwrite(struct vm_fault *vmf, const struct iomap_ops *ops)
return block_page_mkwrite_return(ret);
}
EXPORT_SYMBOL_GPL(iomap_page_mkwrite);
-
-/*
- * Private flags for iomap_dio, must not overlap with the public ones in
- * iomap.h:
- */
-#define IOMAP_DIO_WRITE_FUA (1 << 28)
-#define IOMAP_DIO_NEED_SYNC (1 << 29)
-#define IOMAP_DIO_WRITE (1 << 30)
-#define IOMAP_DIO_DIRTY (1 << 31)
-
-struct iomap_dio {
- struct kiocb *iocb;
- iomap_dio_end_io_t *end_io;
- loff_t i_size;
- loff_t size;
- atomic_t ref;
- unsigned flags;
- int error;
- bool wait_for_completion;
-
- union {
- /* used during submission and for synchronous completion: */
- struct {
- struct iov_iter *iter;
- struct task_struct *waiter;
- struct request_queue *last_queue;
- blk_qc_t cookie;
- } submit;
-
- /* used for aio completion: */
- struct {
- struct work_struct work;
- } aio;
- };
-};
-
-int iomap_dio_iopoll(struct kiocb *kiocb, bool spin)
-{
- struct request_queue *q = READ_ONCE(kiocb->private);
-
- if (!q)
- return 0;
- return blk_poll(q, READ_ONCE(kiocb->ki_cookie), spin);
-}
-EXPORT_SYMBOL_GPL(iomap_dio_iopoll);
-
-static void iomap_dio_submit_bio(struct iomap_dio *dio, struct iomap *iomap,
- struct bio *bio)
-{
- atomic_inc(&dio->ref);
-
- if (dio->iocb->ki_flags & IOCB_HIPRI)
- bio_set_polled(bio, dio->iocb);
-
- dio->submit.last_queue = bdev_get_queue(iomap->bdev);
- dio->submit.cookie = submit_bio(bio);
-}
-
-static ssize_t iomap_dio_complete(struct iomap_dio *dio)
-{
- struct kiocb *iocb = dio->iocb;
- struct inode *inode = file_inode(iocb->ki_filp);
- loff_t offset = iocb->ki_pos;
- ssize_t ret;
-
- if (dio->end_io) {
- ret = dio->end_io(iocb,
- dio->error ? dio->error : dio->size,
- dio->flags);
- } else {
- ret = dio->error;
- }
-
- 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;
- iocb->ki_pos += ret;
- }
-
- /*
- * 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 (!dio->error &&
- (dio->flags & IOMAP_DIO_WRITE) && inode->i_mapping->nrpages) {
- int err;
- err = invalidate_inode_pages2_range(inode->i_mapping,
- offset >> PAGE_SHIFT,
- (offset + dio->size - 1) >> PAGE_SHIFT);
- if (err)
- dio_warn_stale_pagecache(iocb->ki_filp);
- }
-
- /*
- * If this is a DSYNC write, make sure we push it to stable storage now
- * that we've written data.
- */
- if (ret > 0 && (dio->flags & IOMAP_DIO_NEED_SYNC))
- ret = generic_write_sync(iocb, ret);
-
- inode_dio_end(file_inode(iocb->ki_filp));
- kfree(dio);
-
- return ret;
-}
-
-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), 0);
-}
-
-/*
- * 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);
-}
-
-static 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)) {
- if (dio->wait_for_completion) {
- struct task_struct *waiter = dio->submit.waiter;
- WRITE_ONCE(dio->submit.waiter, NULL);
- blk_wake_io_task(waiter);
- } else if (dio->flags & IOMAP_DIO_WRITE) {
- struct inode *inode = file_inode(dio->iocb->ki_filp);
-
- INIT_WORK(&dio->aio.work, iomap_dio_complete_work);
- queue_work(inode->i_sb->s_dio_done_wq, &dio->aio.work);
- } else {
- iomap_dio_complete_work(&dio->aio.work);
- }
- }
-
- if (should_dirty) {
- bio_check_pages_dirty(bio);
- } else {
- bio_release_pages(bio, false);
- bio_put(bio);
- }
-}
-
-static void
-iomap_dio_zero(struct iomap_dio *dio, struct iomap *iomap, loff_t pos,
- unsigned len)
-{
- struct page *page = ZERO_PAGE(0);
- int flags = REQ_SYNC | REQ_IDLE;
- struct bio *bio;
-
- bio = bio_alloc(GFP_KERNEL, 1);
- bio_set_dev(bio, iomap->bdev);
- bio->bi_iter.bi_sector = iomap_sector(iomap, pos);
- bio->bi_private = dio;
- bio->bi_end_io = iomap_dio_bio_end_io;
-
- get_page(page);
- __bio_add_page(bio, page, len, 0);
- bio_set_op_attrs(bio, REQ_OP_WRITE, flags);
- iomap_dio_submit_bio(dio, iomap, bio);
-}
-
-static loff_t
-iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length,
- struct iomap_dio *dio, struct iomap *iomap)
-{
- unsigned int blkbits = blksize_bits(bdev_logical_block_size(iomap->bdev));
- unsigned int fs_block_size = i_blocksize(inode), pad;
- unsigned int align = iov_iter_alignment(dio->submit.iter);
- struct iov_iter iter;
- struct bio *bio;
- bool need_zeroout = false;
- bool use_fua = false;
- int nr_pages, ret = 0;
- size_t copied = 0;
-
- if ((pos | length | align) & ((1 << blkbits) - 1))
- 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 supports FUA. This allows us to avoid
- * cache flushes on IO completion.
- */
- if (!(iomap->flags & (IOMAP_F_SHARED|IOMAP_F_DIRTY)) &&
- (dio->flags & IOMAP_DIO_WRITE_FUA) &&
- blk_queue_fua(bdev_get_queue(iomap->bdev)))
- use_fua = true;
- }
-
- /*
- * Operate on a partial iter trimmed to the extent we were called for.
- * We'll update the iter in the dio once we're done with this extent.
- */
- iter = *dio->submit.iter;
- iov_iter_truncate(&iter, length);
-
- nr_pages = iov_iter_npages(&iter, BIO_MAX_PAGES);
- if (nr_pages <= 0)
- return nr_pages;
-
- 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(dio, iomap, pos - pad, pad);
- }
-
- do {
- size_t n;
- if (dio->error) {
- iov_iter_revert(dio->submit.iter, copied);
- return 0;
- }
-
- bio = bio_alloc(GFP_KERNEL, nr_pages);
- bio_set_dev(bio, iomap->bdev);
- bio->bi_iter.bi_sector = iomap_sector(iomap, pos);
- bio->bi_write_hint = dio->iocb->ki_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, &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) {
- bio->bi_opf = REQ_OP_WRITE | REQ_SYNC | REQ_IDLE;
- if (use_fua)
- bio->bi_opf |= REQ_FUA;
- else
- dio->flags &= ~IOMAP_DIO_WRITE_FUA;
- task_io_account_write(n);
- } else {
- bio->bi_opf = REQ_OP_READ;
- if (dio->flags & IOMAP_DIO_DIRTY)
- bio_set_pages_dirty(bio);
- }
-
- iov_iter_advance(dio->submit.iter, n);
-
- dio->size += n;
- pos += n;
- copied += n;
-
- nr_pages = iov_iter_npages(&iter, BIO_MAX_PAGES);
- iomap_dio_submit_bio(dio, iomap, bio);
- } 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(dio, iomap, pos, fs_block_size - pad);
- }
- return copied ? copied : ret;
-}
-
-static loff_t
-iomap_dio_hole_actor(loff_t length, struct iomap_dio *dio)
-{
- length = iov_iter_zero(length, dio->submit.iter);
- dio->size += length;
- return length;
-}
-
-static loff_t
-iomap_dio_inline_actor(struct inode *inode, loff_t pos, loff_t length,
- struct iomap_dio *dio, struct iomap *iomap)
-{
- struct iov_iter *iter = dio->submit.iter;
- size_t copied;
-
- BUG_ON(pos + length > PAGE_SIZE - offset_in_page(iomap->inline_data));
-
- if (dio->flags & IOMAP_DIO_WRITE) {
- loff_t size = inode->i_size;
-
- if (pos > size)
- memset(iomap->inline_data + size, 0, pos - size);
- copied = copy_from_iter(iomap->inline_data + pos, length, iter);
- if (copied) {
- if (pos + copied > size)
- i_size_write(inode, pos + copied);
- mark_inode_dirty(inode);
- }
- } else {
- copied = copy_to_iter(iomap->inline_data + pos, length, iter);
- }
- dio->size += copied;
- return copied;
-}
-
-static loff_t
-iomap_dio_actor(struct inode *inode, loff_t pos, loff_t length,
- void *data, struct iomap *iomap)
-{
- struct iomap_dio *dio = data;
-
- switch (iomap->type) {
- case IOMAP_HOLE:
- if (WARN_ON_ONCE(dio->flags & IOMAP_DIO_WRITE))
- return -EIO;
- return iomap_dio_hole_actor(length, dio);
- case IOMAP_UNWRITTEN:
- if (!(dio->flags & IOMAP_DIO_WRITE))
- return iomap_dio_hole_actor(length, dio);
- return iomap_dio_bio_actor(inode, pos, length, dio, iomap);
- case IOMAP_MAPPED:
- return iomap_dio_bio_actor(inode, pos, length, dio, iomap);
- case IOMAP_INLINE:
- return iomap_dio_inline_actor(inode, pos, length, dio, iomap);
- 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.
- */
-ssize_t
-iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
- const struct iomap_ops *ops, iomap_dio_end_io_t end_io)
-{
- struct address_space *mapping = iocb->ki_filp->f_mapping;
- struct inode *inode = file_inode(iocb->ki_filp);
- size_t count = iov_iter_count(iter);
- loff_t pos = iocb->ki_pos, start = pos;
- loff_t end = iocb->ki_pos + count - 1, ret = 0;
- unsigned int flags = IOMAP_DIRECT;
- bool wait_for_completion = is_sync_kiocb(iocb);
- struct blk_plug plug;
- struct iomap_dio *dio;
-
- lockdep_assert_held(&inode->i_rwsem);
-
- if (!count)
- return 0;
-
- dio = kmalloc(sizeof(*dio), GFP_KERNEL);
- if (!dio)
- return -ENOMEM;
-
- dio->iocb = iocb;
- atomic_set(&dio->ref, 1);
- dio->size = 0;
- dio->i_size = i_size_read(inode);
- dio->end_io = end_io;
- dio->error = 0;
- dio->flags = 0;
-
- dio->submit.iter = iter;
- dio->submit.waiter = current;
- dio->submit.cookie = BLK_QC_T_NONE;
- dio->submit.last_queue = NULL;
-
- if (iov_iter_rw(iter) == READ) {
- if (pos >= dio->i_size)
- goto out_free_dio;
-
- if (iter_is_iovec(iter) && iov_iter_rw(iter) == READ)
- dio->flags |= IOMAP_DIO_DIRTY;
- } else {
- flags |= IOMAP_WRITE;
- dio->flags |= IOMAP_DIO_WRITE;
-
- /* for data sync or sync, we need sync completion processing */
- if (iocb->ki_flags & IOCB_DSYNC)
- dio->flags |= IOMAP_DIO_NEED_SYNC;
-
- /*
- * For datasync only writes, we optimistically try using FUA for
- * this IO. 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_DSYNC | IOCB_SYNC)) == IOCB_DSYNC)
- dio->flags |= IOMAP_DIO_WRITE_FUA;
- }
-
- if (iocb->ki_flags & IOCB_NOWAIT) {
- if (filemap_range_has_page(mapping, start, end)) {
- ret = -EAGAIN;
- goto out_free_dio;
- }
- flags |= IOMAP_NOWAIT;
- }
-
- ret = filemap_write_and_wait_range(mapping, start, end);
- if (ret)
- goto out_free_dio;
-
- /*
- * Try to invalidate cache pages for the range we're direct
- * writing. If this invalidation fails, tough, the write will
- * still work, but racing two incompatible write paths is a
- * pretty crazy thing to do, so we don't support it 100%.
- */
- ret = invalidate_inode_pages2_range(mapping,
- start >> PAGE_SHIFT, end >> PAGE_SHIFT);
- if (ret)
- dio_warn_stale_pagecache(iocb->ki_filp);
- ret = 0;
-
- if (iov_iter_rw(iter) == WRITE && !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);
- do {
- ret = iomap_apply(inode, pos, count, flags, ops, dio,
- iomap_dio_actor);
- if (ret <= 0) {
- /* magic error code to fall back to buffered I/O */
- if (ret == -ENOTBLK) {
- wait_for_completion = true;
- ret = 0;
- }
- break;
- }
- pos += ret;
-
- if (iov_iter_rw(iter) == READ && pos >= dio->i_size)
- break;
- } while ((count = iov_iter_count(iter)) > 0);
- blk_finish_plug(&plug);
-
- if (ret < 0)
- iomap_dio_set_error(dio, ret);
-
- /*
- * If all the writes we issued were FUA, we don't need to flush the
- * cache on IO completion. Clear the sync flag for this case.
- */
- if (dio->flags & IOMAP_DIO_WRITE_FUA)
- dio->flags &= ~IOMAP_DIO_NEED_SYNC;
-
- WRITE_ONCE(iocb->ki_cookie, dio->submit.cookie);
- WRITE_ONCE(iocb->private, dio->submit.last_queue);
-
- /*
- * We are about to drop our additional submission reference, which
- * might be the last reference to the dio. There are three 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)
- return -EIOCBQUEUED;
-
- for (;;) {
- set_current_state(TASK_UNINTERRUPTIBLE);
- if (!READ_ONCE(dio->submit.waiter))
- break;
-
- if (!(iocb->ki_flags & IOCB_HIPRI) ||
- !dio->submit.last_queue ||
- !blk_poll(dio->submit.last_queue,
- dio->submit.cookie, true))
- io_schedule();
- }
- __set_current_state(TASK_RUNNING);
- }
-
- return iomap_dio_complete(dio);
-
-out_free_dio:
- kfree(dio);
- return ret;
-}
-EXPORT_SYMBOL_GPL(iomap_dio_rw);
diff --git a/fs/iomap/Makefile b/fs/iomap/Makefile
index 12dc7f844bbd..3e158f38b8e2 100644
--- a/fs/iomap/Makefile
+++ b/fs/iomap/Makefile
@@ -9,6 +9,7 @@ ccflags-y += -I $(srctree)/$(src)/..
obj-$(CONFIG_FS_IOMAP) += iomap.o

iomap-y += \
+ direct-io.o \
fiemap.o \
seek.o

diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
new file mode 100644
index 000000000000..c99e5b085c34
--- /dev/null
+++ b/fs/iomap/direct-io.c
@@ -0,0 +1,562 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2010 Red Hat, Inc.
+ * Copyright (c) 2016-2018 Christoph Hellwig.
+ */
+#include <linux/module.h>
+#include <linux/compiler.h>
+#include <linux/fs.h>
+#include <linux/iomap.h>
+#include <linux/backing-dev.h>
+#include <linux/uio.h>
+#include <linux/task_io_accounting_ops.h>
+
+#include "internal.h"
+
+/*
+ * Private flags for iomap_dio, must not overlap with the public ones in
+ * iomap.h:
+ */
+#define IOMAP_DIO_WRITE_FUA (1 << 28)
+#define IOMAP_DIO_NEED_SYNC (1 << 29)
+#define IOMAP_DIO_WRITE (1 << 30)
+#define IOMAP_DIO_DIRTY (1 << 31)
+
+struct iomap_dio {
+ struct kiocb *iocb;
+ iomap_dio_end_io_t *end_io;
+ loff_t i_size;
+ loff_t size;
+ atomic_t ref;
+ unsigned flags;
+ int error;
+ bool wait_for_completion;
+
+ union {
+ /* used during submission and for synchronous completion: */
+ struct {
+ struct iov_iter *iter;
+ struct task_struct *waiter;
+ struct request_queue *last_queue;
+ blk_qc_t cookie;
+ } submit;
+
+ /* used for aio completion: */
+ struct {
+ struct work_struct work;
+ } aio;
+ };
+};
+
+int iomap_dio_iopoll(struct kiocb *kiocb, bool spin)
+{
+ struct request_queue *q = READ_ONCE(kiocb->private);
+
+ if (!q)
+ return 0;
+ return blk_poll(q, READ_ONCE(kiocb->ki_cookie), spin);
+}
+EXPORT_SYMBOL_GPL(iomap_dio_iopoll);
+
+static void iomap_dio_submit_bio(struct iomap_dio *dio, struct iomap *iomap,
+ struct bio *bio)
+{
+ atomic_inc(&dio->ref);
+
+ if (dio->iocb->ki_flags & IOCB_HIPRI)
+ bio_set_polled(bio, dio->iocb);
+
+ dio->submit.last_queue = bdev_get_queue(iomap->bdev);
+ dio->submit.cookie = submit_bio(bio);
+}
+
+static ssize_t iomap_dio_complete(struct iomap_dio *dio)
+{
+ struct kiocb *iocb = dio->iocb;
+ struct inode *inode = file_inode(iocb->ki_filp);
+ loff_t offset = iocb->ki_pos;
+ ssize_t ret;
+
+ if (dio->end_io) {
+ ret = dio->end_io(iocb,
+ dio->error ? dio->error : dio->size,
+ dio->flags);
+ } else {
+ ret = dio->error;
+ }
+
+ 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;
+ iocb->ki_pos += ret;
+ }
+
+ /*
+ * 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 (!dio->error &&
+ (dio->flags & IOMAP_DIO_WRITE) && inode->i_mapping->nrpages) {
+ int err;
+ err = invalidate_inode_pages2_range(inode->i_mapping,
+ offset >> PAGE_SHIFT,
+ (offset + dio->size - 1) >> PAGE_SHIFT);
+ if (err)
+ dio_warn_stale_pagecache(iocb->ki_filp);
+ }
+
+ /*
+ * If this is a DSYNC write, make sure we push it to stable storage now
+ * that we've written data.
+ */
+ if (ret > 0 && (dio->flags & IOMAP_DIO_NEED_SYNC))
+ ret = generic_write_sync(iocb, ret);
+
+ inode_dio_end(file_inode(iocb->ki_filp));
+ kfree(dio);
+
+ return ret;
+}
+
+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), 0);
+}
+
+/*
+ * 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);
+}
+
+static 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)) {
+ if (dio->wait_for_completion) {
+ struct task_struct *waiter = dio->submit.waiter;
+ WRITE_ONCE(dio->submit.waiter, NULL);
+ blk_wake_io_task(waiter);
+ } else if (dio->flags & IOMAP_DIO_WRITE) {
+ struct inode *inode = file_inode(dio->iocb->ki_filp);
+
+ INIT_WORK(&dio->aio.work, iomap_dio_complete_work);
+ queue_work(inode->i_sb->s_dio_done_wq, &dio->aio.work);
+ } else {
+ iomap_dio_complete_work(&dio->aio.work);
+ }
+ }
+
+ if (should_dirty) {
+ bio_check_pages_dirty(bio);
+ } else {
+ bio_release_pages(bio, false);
+ bio_put(bio);
+ }
+}
+
+static void
+iomap_dio_zero(struct iomap_dio *dio, struct iomap *iomap, loff_t pos,
+ unsigned len)
+{
+ struct page *page = ZERO_PAGE(0);
+ int flags = REQ_SYNC | REQ_IDLE;
+ struct bio *bio;
+
+ bio = bio_alloc(GFP_KERNEL, 1);
+ bio_set_dev(bio, iomap->bdev);
+ bio->bi_iter.bi_sector = iomap_sector(iomap, pos);
+ bio->bi_private = dio;
+ bio->bi_end_io = iomap_dio_bio_end_io;
+
+ get_page(page);
+ __bio_add_page(bio, page, len, 0);
+ bio_set_op_attrs(bio, REQ_OP_WRITE, flags);
+ iomap_dio_submit_bio(dio, iomap, bio);
+}
+
+static loff_t
+iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length,
+ struct iomap_dio *dio, struct iomap *iomap)
+{
+ unsigned int blkbits = blksize_bits(bdev_logical_block_size(iomap->bdev));
+ unsigned int fs_block_size = i_blocksize(inode), pad;
+ unsigned int align = iov_iter_alignment(dio->submit.iter);
+ struct iov_iter iter;
+ struct bio *bio;
+ bool need_zeroout = false;
+ bool use_fua = false;
+ int nr_pages, ret = 0;
+ size_t copied = 0;
+
+ if ((pos | length | align) & ((1 << blkbits) - 1))
+ 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 supports FUA. This allows us to avoid
+ * cache flushes on IO completion.
+ */
+ if (!(iomap->flags & (IOMAP_F_SHARED|IOMAP_F_DIRTY)) &&
+ (dio->flags & IOMAP_DIO_WRITE_FUA) &&
+ blk_queue_fua(bdev_get_queue(iomap->bdev)))
+ use_fua = true;
+ }
+
+ /*
+ * Operate on a partial iter trimmed to the extent we were called for.
+ * We'll update the iter in the dio once we're done with this extent.
+ */
+ iter = *dio->submit.iter;
+ iov_iter_truncate(&iter, length);
+
+ nr_pages = iov_iter_npages(&iter, BIO_MAX_PAGES);
+ if (nr_pages <= 0)
+ return nr_pages;
+
+ 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(dio, iomap, pos - pad, pad);
+ }
+
+ do {
+ size_t n;
+ if (dio->error) {
+ iov_iter_revert(dio->submit.iter, copied);
+ return 0;
+ }
+
+ bio = bio_alloc(GFP_KERNEL, nr_pages);
+ bio_set_dev(bio, iomap->bdev);
+ bio->bi_iter.bi_sector = iomap_sector(iomap, pos);
+ bio->bi_write_hint = dio->iocb->ki_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, &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) {
+ bio->bi_opf = REQ_OP_WRITE | REQ_SYNC | REQ_IDLE;
+ if (use_fua)
+ bio->bi_opf |= REQ_FUA;
+ else
+ dio->flags &= ~IOMAP_DIO_WRITE_FUA;
+ task_io_account_write(n);
+ } else {
+ bio->bi_opf = REQ_OP_READ;
+ if (dio->flags & IOMAP_DIO_DIRTY)
+ bio_set_pages_dirty(bio);
+ }
+
+ iov_iter_advance(dio->submit.iter, n);
+
+ dio->size += n;
+ pos += n;
+ copied += n;
+
+ nr_pages = iov_iter_npages(&iter, BIO_MAX_PAGES);
+ iomap_dio_submit_bio(dio, iomap, bio);
+ } 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(dio, iomap, pos, fs_block_size - pad);
+ }
+ return copied ? copied : ret;
+}
+
+static loff_t
+iomap_dio_hole_actor(loff_t length, struct iomap_dio *dio)
+{
+ length = iov_iter_zero(length, dio->submit.iter);
+ dio->size += length;
+ return length;
+}
+
+static loff_t
+iomap_dio_inline_actor(struct inode *inode, loff_t pos, loff_t length,
+ struct iomap_dio *dio, struct iomap *iomap)
+{
+ struct iov_iter *iter = dio->submit.iter;
+ size_t copied;
+
+ BUG_ON(pos + length > PAGE_SIZE - offset_in_page(iomap->inline_data));
+
+ if (dio->flags & IOMAP_DIO_WRITE) {
+ loff_t size = inode->i_size;
+
+ if (pos > size)
+ memset(iomap->inline_data + size, 0, pos - size);
+ copied = copy_from_iter(iomap->inline_data + pos, length, iter);
+ if (copied) {
+ if (pos + copied > size)
+ i_size_write(inode, pos + copied);
+ mark_inode_dirty(inode);
+ }
+ } else {
+ copied = copy_to_iter(iomap->inline_data + pos, length, iter);
+ }
+ dio->size += copied;
+ return copied;
+}
+
+static loff_t
+iomap_dio_actor(struct inode *inode, loff_t pos, loff_t length,
+ void *data, struct iomap *iomap)
+{
+ struct iomap_dio *dio = data;
+
+ switch (iomap->type) {
+ case IOMAP_HOLE:
+ if (WARN_ON_ONCE(dio->flags & IOMAP_DIO_WRITE))
+ return -EIO;
+ return iomap_dio_hole_actor(length, dio);
+ case IOMAP_UNWRITTEN:
+ if (!(dio->flags & IOMAP_DIO_WRITE))
+ return iomap_dio_hole_actor(length, dio);
+ return iomap_dio_bio_actor(inode, pos, length, dio, iomap);
+ case IOMAP_MAPPED:
+ return iomap_dio_bio_actor(inode, pos, length, dio, iomap);
+ case IOMAP_INLINE:
+ return iomap_dio_inline_actor(inode, pos, length, dio, iomap);
+ 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.
+ */
+ssize_t
+iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
+ const struct iomap_ops *ops, iomap_dio_end_io_t end_io)
+{
+ struct address_space *mapping = iocb->ki_filp->f_mapping;
+ struct inode *inode = file_inode(iocb->ki_filp);
+ size_t count = iov_iter_count(iter);
+ loff_t pos = iocb->ki_pos, start = pos;
+ loff_t end = iocb->ki_pos + count - 1, ret = 0;
+ unsigned int flags = IOMAP_DIRECT;
+ bool wait_for_completion = is_sync_kiocb(iocb);
+ struct blk_plug plug;
+ struct iomap_dio *dio;
+
+ lockdep_assert_held(&inode->i_rwsem);
+
+ if (!count)
+ return 0;
+
+ dio = kmalloc(sizeof(*dio), GFP_KERNEL);
+ if (!dio)
+ return -ENOMEM;
+
+ dio->iocb = iocb;
+ atomic_set(&dio->ref, 1);
+ dio->size = 0;
+ dio->i_size = i_size_read(inode);
+ dio->end_io = end_io;
+ dio->error = 0;
+ dio->flags = 0;
+
+ dio->submit.iter = iter;
+ dio->submit.waiter = current;
+ dio->submit.cookie = BLK_QC_T_NONE;
+ dio->submit.last_queue = NULL;
+
+ if (iov_iter_rw(iter) == READ) {
+ if (pos >= dio->i_size)
+ goto out_free_dio;
+
+ if (iter_is_iovec(iter) && iov_iter_rw(iter) == READ)
+ dio->flags |= IOMAP_DIO_DIRTY;
+ } else {
+ flags |= IOMAP_WRITE;
+ dio->flags |= IOMAP_DIO_WRITE;
+
+ /* for data sync or sync, we need sync completion processing */
+ if (iocb->ki_flags & IOCB_DSYNC)
+ dio->flags |= IOMAP_DIO_NEED_SYNC;
+
+ /*
+ * For datasync only writes, we optimistically try using FUA for
+ * this IO. 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_DSYNC | IOCB_SYNC)) == IOCB_DSYNC)
+ dio->flags |= IOMAP_DIO_WRITE_FUA;
+ }
+
+ if (iocb->ki_flags & IOCB_NOWAIT) {
+ if (filemap_range_has_page(mapping, start, end)) {
+ ret = -EAGAIN;
+ goto out_free_dio;
+ }
+ flags |= IOMAP_NOWAIT;
+ }
+
+ ret = filemap_write_and_wait_range(mapping, start, end);
+ if (ret)
+ goto out_free_dio;
+
+ /*
+ * Try to invalidate cache pages for the range we're direct
+ * writing. If this invalidation fails, tough, the write will
+ * still work, but racing two incompatible write paths is a
+ * pretty crazy thing to do, so we don't support it 100%.
+ */
+ ret = invalidate_inode_pages2_range(mapping,
+ start >> PAGE_SHIFT, end >> PAGE_SHIFT);
+ if (ret)
+ dio_warn_stale_pagecache(iocb->ki_filp);
+ ret = 0;
+
+ if (iov_iter_rw(iter) == WRITE && !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);
+ do {
+ ret = iomap_apply(inode, pos, count, flags, ops, dio,
+ iomap_dio_actor);
+ if (ret <= 0) {
+ /* magic error code to fall back to buffered I/O */
+ if (ret == -ENOTBLK) {
+ wait_for_completion = true;
+ ret = 0;
+ }
+ break;
+ }
+ pos += ret;
+
+ if (iov_iter_rw(iter) == READ && pos >= dio->i_size)
+ break;
+ } while ((count = iov_iter_count(iter)) > 0);
+ blk_finish_plug(&plug);
+
+ if (ret < 0)
+ iomap_dio_set_error(dio, ret);
+
+ /*
+ * If all the writes we issued were FUA, we don't need to flush the
+ * cache on IO completion. Clear the sync flag for this case.
+ */
+ if (dio->flags & IOMAP_DIO_WRITE_FUA)
+ dio->flags &= ~IOMAP_DIO_NEED_SYNC;
+
+ WRITE_ONCE(iocb->ki_cookie, dio->submit.cookie);
+ WRITE_ONCE(iocb->private, dio->submit.last_queue);
+
+ /*
+ * We are about to drop our additional submission reference, which
+ * might be the last reference to the dio. There are three 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)
+ return -EIOCBQUEUED;
+
+ for (;;) {
+ set_current_state(TASK_UNINTERRUPTIBLE);
+ if (!READ_ONCE(dio->submit.waiter))
+ break;
+
+ if (!(iocb->ki_flags & IOCB_HIPRI) ||
+ !dio->submit.last_queue ||
+ !blk_poll(dio->submit.last_queue,
+ dio->submit.cookie, true))
+ io_schedule();
+ }
+ __set_current_state(TASK_RUNNING);
+ }
+
+ return iomap_dio_complete(dio);
+
+out_free_dio:
+ kfree(dio);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(iomap_dio_rw);
diff --git a/include/linux/iomap.h b/include/linux/iomap.h
index 1df9ea187a9a..baa1e2d31f05 100644
--- a/include/linux/iomap.h
+++ b/include/linux/iomap.h
@@ -7,6 +7,7 @@
#include <linux/mm.h>
#include <linux/types.h>
#include <linux/mm_types.h>
+#include <linux/blkdev.h>

struct address_space;
struct fiemap_extent_info;
@@ -69,6 +70,12 @@ struct iomap {
const struct iomap_page_ops *page_ops;
};

+static inline sector_t
+iomap_sector(struct iomap *iomap, loff_t pos)
+{
+ return (iomap->addr + pos - iomap->offset) >> SECTOR_SHIFT;
+}
+
/*
* When a filesystem sets page_ops in an iomap mapping it returns, page_prepare
* and page_done will be called for each page written to. This only applies to