[PATCH v2 00/10] xfs/iomap: fix non-atomic clone operation and don't update size when zeroing range post eof

[PATCH v2 00/10] xfs/iomap: fix non-atomic clone operation and don't update size when zeroing range post eof

[Zhang Yi]

From: Zhang Yi <yi.zhang@huawei.com>

Changes since v1:
 - Make xfs_bmapi_convert_delalloc() to allocate the target offset and
   drop the writeback helper xfs_convert_blocks().
 - Don't use xfs_iomap_write_direct() to convert delalloc blocks for
   zeroing posteof case, use xfs_bmapi_convert_delalloc() instead.
 - Fix two off-by-one issues when converting delalloc blocks.
 - Add a separate patch to drop the buffered write failure handle in
   zeroing and unsharing.
 - Add a comments do emphasize updating i_size should under folio lock.
 - Make iomap_write_end() to return a boolean, and do some cleanups in
   buffered write begin path.

This patch series fix a problem of exposing zeroed data on xfs since the
non-atomic clone operation. This problem was found while I was
developing ext4 buffered IO iomap conversion (ext4 is relying on this
fix [1]), the root cause of this problem and the discussion about the
solution please see [2]. After fix the problem, iomap_zero_range()
doesn't need to update i_size so that ext4 can use it to zero partial
block, e.g. truncate eof block [3].

[1] https://lore.kernel.org/linux-ext4/20240127015825.1608160-1-yi.zhang@huaweicloud.com/
[2] https://lore.kernel.org/linux-ext4/9b0040ef-3d9d-6246-4bdd-82b9a8f55fa2@huaweicloud.com/
[3] https://lore.kernel.org/linux-ext4/9c9f1831-a772-299b-072b-1c8116c3fb35@huaweicloud.com/

Thanks,
Yi.

Zhang Yi (10):
  xfs: match lock mode in xfs_buffered_write_iomap_begin()
  xfs: allow xfs_bmapi_convert_delalloc() to pass NULL seq
  xfs: make xfs_bmapi_convert_delalloc() to allocate the target offset
  xfs: drop xfs_convert_blocks()
  xfs: convert delayed extents to unwritten when zeroing post eof blocks
  iomap: drop the write failure handles when unsharing and zeroing
  iomap: don't increase i_size if it's not a write operation
  iomap: use a new variable to handle the written bytes in
    iomap_write_iter()
  iomap: make block_write_end() return a boolean
  iomap: do some small logical cleanup in buffered write

 fs/iomap/buffered-io.c   | 101 ++++++++++++++++++++++-----------------
 fs/xfs/libxfs/xfs_bmap.c |  40 ++++++++++++++--
 fs/xfs/xfs_aops.c        |  54 ++++++---------------
 fs/xfs/xfs_iomap.c       |  39 +++++++++++++--
 4 files changed, 142 insertions(+), 92 deletions(-)

-- 
2.39.2

[PATCH v2 01/10] xfs: match lock mode in xfs_buffered_write_iomap_begin()

[Zhang Yi]

From: Zhang Yi <yi.zhang@huawei.com>

Commit 1aa91d9c9933 ("xfs: Add async buffered write support") replace
xfs_ilock(XFS_ILOCK_EXCL) with xfs_ilock_for_iomap() when locking the
writing inode, and a new variable lockmode is used to indicate the lock
mode. Although the lockmode should always be XFS_ILOCK_EXCL, it's still
better to use this variable instead of useing XFS_ILOCK_EXCL directly
when unlocking the inode.

Fixes: 1aa91d9c9933 ("xfs: Add async buffered write support")
Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 fs/xfs/xfs_iomap.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index 18c8f168b153..ccf83e72d8ca 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -1149,13 +1149,13 @@ xfs_buffered_write_iomap_begin(
 	 * them out if the write happens to fail.
 	 */
 	seq = xfs_iomap_inode_sequence(ip, IOMAP_F_NEW);
-	xfs_iunlock(ip, XFS_ILOCK_EXCL);
+	xfs_iunlock(ip, lockmode);
 	trace_xfs_iomap_alloc(ip, offset, count, allocfork, &imap);
 	return xfs_bmbt_to_iomap(ip, iomap, &imap, flags, IOMAP_F_NEW, seq);
 
 found_imap:
 	seq = xfs_iomap_inode_sequence(ip, 0);
-	xfs_iunlock(ip, XFS_ILOCK_EXCL);
+	xfs_iunlock(ip, lockmode);
 	return xfs_bmbt_to_iomap(ip, iomap, &imap, flags, 0, seq);
 
 found_cow:
@@ -1165,17 +1165,17 @@ xfs_buffered_write_iomap_begin(
 		if (error)
 			goto out_unlock;
 		seq = xfs_iomap_inode_sequence(ip, IOMAP_F_SHARED);
-		xfs_iunlock(ip, XFS_ILOCK_EXCL);
+		xfs_iunlock(ip, lockmode);
 		return xfs_bmbt_to_iomap(ip, iomap, &cmap, flags,
 					 IOMAP_F_SHARED, seq);
 	}
 
 	xfs_trim_extent(&cmap, offset_fsb, imap.br_startoff - offset_fsb);
-	xfs_iunlock(ip, XFS_ILOCK_EXCL);
+	xfs_iunlock(ip, lockmode);
 	return xfs_bmbt_to_iomap(ip, iomap, &cmap, flags, 0, seq);
 
 out_unlock:
-	xfs_iunlock(ip, XFS_ILOCK_EXCL);
+	xfs_iunlock(ip, lockmode);
 	return error;
 }
 
-- 
2.39.2

[PATCH v2 02/10] xfs: allow xfs_bmapi_convert_delalloc() to pass NULL seq

[Zhang Yi]

From: Zhang Yi <yi.zhang@huawei.com>

xfs_bmapi_convert_delalloc() always pass out ifp->if_seq now, make it
support not passing out this value if caller doesn't care about it.

Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
---
 fs/xfs/libxfs/xfs_bmap.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
index f362345467fa..07dc35de8ce5 100644
--- a/fs/xfs/libxfs/xfs_bmap.c
+++ b/fs/xfs/libxfs/xfs_bmap.c
@@ -4574,7 +4574,8 @@ xfs_bmapi_convert_delalloc(
 	if (!isnullstartblock(bma.got.br_startblock)) {
 		xfs_bmbt_to_iomap(ip, iomap, &bma.got, 0, flags,
 				xfs_iomap_inode_sequence(ip, flags));
-		*seq = READ_ONCE(ifp->if_seq);
+		if (seq)
+			*seq = READ_ONCE(ifp->if_seq);
 		goto out_trans_cancel;
 	}
 
@@ -4623,7 +4624,8 @@ xfs_bmapi_convert_delalloc(
 	ASSERT(!isnullstartblock(bma.got.br_startblock));
 	xfs_bmbt_to_iomap(ip, iomap, &bma.got, 0, flags,
 				xfs_iomap_inode_sequence(ip, flags));
-	*seq = READ_ONCE(ifp->if_seq);
+	if (seq)
+		*seq = READ_ONCE(ifp->if_seq);
 
 	if (whichfork == XFS_COW_FORK)
 		xfs_refcount_alloc_cow_extent(tp, bma.blkno, bma.length);
-- 
2.39.2

[PATCH v2 03/10] xfs: make xfs_bmapi_convert_delalloc() to allocate the target offset

[Zhang Yi]

From: Zhang Yi <yi.zhang@huawei.com>

Since xfs_bmapi_convert_delalloc() only attempts to allocate the entire
delalloc extent and require multiple invocations to allocate the target
offset. So xfs_convert_blocks() add a loop to do this job and we call it
in the write back path, but xfs_convert_blocks() isn't a common helper.
Let's do it in xfs_bmapi_convert_delalloc(), preparing for the post EOF
delalloc blocks converting in the buffered write begin path.

Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
---
 fs/xfs/libxfs/xfs_bmap.c | 34 ++++++++++++++++++++++++++++++++--
 fs/xfs/xfs_aops.c        | 15 +--------------
 2 files changed, 33 insertions(+), 16 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
index 07dc35de8ce5..042e8d3ab0ba 100644
--- a/fs/xfs/libxfs/xfs_bmap.c
+++ b/fs/xfs/libxfs/xfs_bmap.c
@@ -4516,8 +4516,8 @@ xfs_bmapi_write(
  * invocations to allocate the target offset if a large enough physical extent
  * is not available.
  */
-int
-xfs_bmapi_convert_delalloc(
+static int
+__xfs_bmapi_convert_delalloc(
 	struct xfs_inode	*ip,
 	int			whichfork,
 	xfs_off_t		offset,
@@ -4648,6 +4648,36 @@ xfs_bmapi_convert_delalloc(
 	return error;
 }
 
+/*
+ * Pass in a dellalloc extent and convert it to real extents, return the real
+ * extent that maps offset_fsb in iomap.
+ */
+int
+xfs_bmapi_convert_delalloc(
+	struct xfs_inode	*ip,
+	int			whichfork,
+	loff_t			offset,
+	struct iomap		*iomap,
+	unsigned int		*seq)
+{
+	int			error;
+
+	/*
+	 * Attempt to allocate whatever delalloc extent currently backs offset
+	 * and put the result into iomap.  Allocate in a loop because it may
+	 * take several attempts to allocate real blocks for a contiguous
+	 * delalloc extent if free space is sufficiently fragmented.
+	 */
+	do {
+		error = __xfs_bmapi_convert_delalloc(ip, whichfork, offset,
+					iomap, seq);
+		if (error)
+			return error;
+	} while (iomap->offset + iomap->length <= offset);
+
+	return 0;
+}
+
 int
 xfs_bmapi_remap(
 	struct xfs_trans	*tp,
diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
index 813f85156b0c..376ec0993943 100644
--- a/fs/xfs/xfs_aops.c
+++ b/fs/xfs/xfs_aops.c
@@ -248,7 +248,6 @@ xfs_convert_blocks(
 	int			whichfork,
 	loff_t			offset)
 {
-	int			error;
 	unsigned		*seq;
 
 	if (whichfork == XFS_COW_FORK)
@@ -256,20 +255,8 @@ xfs_convert_blocks(
 	else
 		seq = &XFS_WPC(wpc)->data_seq;
 
-	/*
-	 * Attempt to allocate whatever delalloc extent currently backs offset
-	 * and put the result into wpc->iomap.  Allocate in a loop because it
-	 * may take several attempts to allocate real blocks for a contiguous
-	 * delalloc extent if free space is sufficiently fragmented.
-	 */
-	do {
-		error = xfs_bmapi_convert_delalloc(ip, whichfork, offset,
+	return xfs_bmapi_convert_delalloc(ip, whichfork, offset,
 				&wpc->iomap, seq);
-		if (error)
-			return error;
-	} while (wpc->iomap.offset + wpc->iomap.length <= offset);
-
-	return 0;
 }
 
 static int
-- 
2.39.2

[PATCH v2 04/10] xfs: drop xfs_convert_blocks()

[Zhang Yi]

From: Zhang Yi <yi.zhang@huawei.com>

Since xfs_bmapi_convert_delalloc() can make sure converting the target
offset, it's time to drop xfs_convert_blocks().

Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
---
 fs/xfs/xfs_aops.c | 41 ++++++++++++++---------------------------
 1 file changed, 14 insertions(+), 27 deletions(-)

diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
index 376ec0993943..6479e0dac69d 100644
--- a/fs/xfs/xfs_aops.c
+++ b/fs/xfs/xfs_aops.c
@@ -233,32 +233,6 @@ xfs_imap_valid(
 	return true;
 }
 
-/*
- * Pass in a dellalloc extent and convert it to real extents, return the real
- * extent that maps offset_fsb in wpc->iomap.
- *
- * The current page is held locked so nothing could have removed the block
- * backing offset_fsb, although it could have moved from the COW to the data
- * fork by another thread.
- */
-static int
-xfs_convert_blocks(
-	struct iomap_writepage_ctx *wpc,
-	struct xfs_inode	*ip,
-	int			whichfork,
-	loff_t			offset)
-{
-	unsigned		*seq;
-
-	if (whichfork == XFS_COW_FORK)
-		seq = &XFS_WPC(wpc)->cow_seq;
-	else
-		seq = &XFS_WPC(wpc)->data_seq;
-
-	return xfs_bmapi_convert_delalloc(ip, whichfork, offset,
-				&wpc->iomap, seq);
-}
-
 static int
 xfs_map_blocks(
 	struct iomap_writepage_ctx *wpc,
@@ -276,6 +250,7 @@ xfs_map_blocks(
 	struct xfs_iext_cursor	icur;
 	int			retries = 0;
 	int			error = 0;
+	unsigned int		*seq;
 
 	if (xfs_is_shutdown(mp))
 		return -EIO;
@@ -373,7 +348,19 @@ xfs_map_blocks(
 	trace_xfs_map_blocks_found(ip, offset, count, whichfork, &imap);
 	return 0;
 allocate_blocks:
-	error = xfs_convert_blocks(wpc, ip, whichfork, offset);
+	/*
+	 * Convert a dellalloc extent to a real one. The current page is held
+	 * locked so nothing could have removed the block backing offset_fsb,
+	 * although it could have moved from the COW to the data fork by another
+	 * thread.
+	 */
+	if (whichfork == XFS_COW_FORK)
+		seq = &XFS_WPC(wpc)->cow_seq;
+	else
+		seq = &XFS_WPC(wpc)->data_seq;
+
+	error = xfs_bmapi_convert_delalloc(ip, whichfork, offset,
+				&wpc->iomap, seq);
 	if (error) {
 		/*
 		 * If we failed to find the extent in the COW fork we might have
-- 
2.39.2

[PATCH v2 05/10] xfs: convert delayed extents to unwritten when zeroing post eof blocks

[Zhang Yi]

From: Zhang Yi <yi.zhang@huawei.com>

Current clone operation could be non-atomic if the destination of a file
is beyond EOF, user could get a file with corrupted (zeroed) data on
crash.

The problem is about to pre-alloctions. If you write some data into a
file [A, B) (the position letters are increased one by one), and xfs
could pre-allocate some blocks, then we get a delayed extent [A, D).
Then the writeback path allocate blocks and convert this delayed extent
[A, C) since lack of enough contiguous physical blocks, so the extent
[C, D) is still delayed. After that, both the in-memory and the on-disk
file size are B. If we clone file range into [E, F) from another file,
xfs_reflink_zero_posteof() would call iomap_zero_range() to zero out the
range [B, E) beyond EOF and flush range. Since [C, D) is still a delayed
extent, it will be zeroed and the file's in-memory && on-disk size will
be updated to D after flushing and before doing the clone operation.
This is wrong, because user can user can see the size change and read
zeros in the middle of the clone operation.

We need to keep the in-memory and on-disk size before the clone
operation starts, so instead of writing zeroes through the page cache
for delayed ranges beyond EOF, we convert these ranges to unwritten and
invalidating any cached data over that range beyond EOF.

Suggested-by: Dave Chinner <david@fromorbit.com>
Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
---
 fs/xfs/xfs_iomap.c | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index ccf83e72d8ca..1a6d05830433 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -1035,6 +1035,24 @@ xfs_buffered_write_iomap_begin(
 	}
 
 	if (imap.br_startoff <= offset_fsb) {
+		/*
+		 * For zeroing out delayed allocation extent, we trim it if
+		 * it's partial beyonds EOF block, or convert it to unwritten
+		 * extent if it's all beyonds EOF block.
+		 */
+		if ((flags & IOMAP_ZERO) &&
+		    isnullstartblock(imap.br_startblock)) {
+			xfs_fileoff_t eof_fsb = XFS_B_TO_FSB(mp, XFS_ISIZE(ip));
+
+			if (offset_fsb >= eof_fsb)
+				goto convert_delay;
+			if (end_fsb > eof_fsb) {
+				end_fsb = eof_fsb;
+				xfs_trim_extent(&imap, offset_fsb,
+						end_fsb - offset_fsb);
+			}
+		}
+
 		/*
 		 * For reflink files we may need a delalloc reservation when
 		 * overwriting shared extents.   This includes zeroing of
@@ -1158,6 +1176,17 @@ xfs_buffered_write_iomap_begin(
 	xfs_iunlock(ip, lockmode);
 	return xfs_bmbt_to_iomap(ip, iomap, &imap, flags, 0, seq);
 
+convert_delay:
+	xfs_iunlock(ip, lockmode);
+	truncate_pagecache(inode, offset);
+	error = xfs_bmapi_convert_delalloc(ip, XFS_DATA_FORK, offset,
+					iomap, NULL);
+	if (error)
+		return error;
+
+	trace_xfs_iomap_alloc(ip, offset, count, XFS_DATA_FORK, &imap);
+	return 0;
+
 found_cow:
 	seq = xfs_iomap_inode_sequence(ip, 0);
 	if (imap.br_startoff <= offset_fsb) {
-- 
2.39.2

[PATCH v2 06/10] iomap: drop the write failure handles when unsharing and zeroing

[Zhang Yi]

From: Zhang Yi <yi.zhang@huawei.com>

Unsharing and zeroing can only happen within EOF, so there is never a
need to perform posteof pagecache truncation if write begin fails, also
partial write could never theoretically happened from iomap_write_end(),
so remove both of them.

Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
---
 fs/iomap/buffered-io.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 093c4515b22a..7e32a204650b 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -786,7 +786,6 @@ static int iomap_write_begin(struct iomap_iter *iter, loff_t pos,
 
 out_unlock:
 	__iomap_put_folio(iter, pos, 0, folio);
-	iomap_write_failed(iter->inode, pos, len);
 
 	return status;
 }
@@ -863,8 +862,6 @@ static size_t iomap_write_end(struct iomap_iter *iter, loff_t pos, size_t len,
 
 	if (old_size < pos)
 		pagecache_isize_extended(iter->inode, old_size, pos);
-	if (ret < len)
-		iomap_write_failed(iter->inode, pos + ret, len - ret);
 	return ret;
 }
 
@@ -912,8 +909,10 @@ static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
 		}
 
 		status = iomap_write_begin(iter, pos, bytes, &folio);
-		if (unlikely(status))
+		if (unlikely(status)) {
+			iomap_write_failed(iter->inode, pos, bytes);
 			break;
+		}
 		if (iter->iomap.flags & IOMAP_F_STALE)
 			break;
 
@@ -927,6 +926,9 @@ static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
 		copied = copy_folio_from_iter_atomic(folio, offset, bytes, i);
 		status = iomap_write_end(iter, pos, bytes, copied, folio);
 
+		if (status < bytes)
+			iomap_write_failed(iter->inode, pos + status,
+					   bytes - status);
 		if (unlikely(copied != status))
 			iov_iter_revert(i, copied - status);
 
-- 
2.39.2

[PATCH v2 07/10] iomap: don't increase i_size if it's not a write operation

[Zhang Yi]

From: Zhang Yi <yi.zhang@huawei.com>

Increase i_size in iomap_zero_range() and iomap_unshare_iter() is not
needed, the caller should handle it. Especially, when truncate partial
block, we should not increase i_size beyond the new EOF here. It doesn't
affect xfs and gfs2 now because they set the new file size after zero
out, it doesn't matter that a transient increase in i_size, but it will
affect ext4 because it set file size before truncate. So move the i_size
updating logic to iomap_write_iter().

Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
---
 fs/iomap/buffered-io.c | 50 +++++++++++++++++++++---------------------
 1 file changed, 25 insertions(+), 25 deletions(-)

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 7e32a204650b..e9112dc78d15 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -837,32 +837,13 @@ static size_t iomap_write_end(struct iomap_iter *iter, loff_t pos, size_t len,
 		size_t copied, struct folio *folio)
 {
 	const struct iomap *srcmap = iomap_iter_srcmap(iter);
-	loff_t old_size = iter->inode->i_size;
-	size_t ret;
-
-	if (srcmap->type == IOMAP_INLINE) {
-		ret = iomap_write_end_inline(iter, folio, pos, copied);
-	} else if (srcmap->flags & IOMAP_F_BUFFER_HEAD) {
-		ret = block_write_end(NULL, iter->inode->i_mapping, pos, len,
-				copied, &folio->page, NULL);
-	} else {
-		ret = __iomap_write_end(iter->inode, pos, len, copied, folio);
-	}
-
-	/*
-	 * Update the in-memory inode size after copying the data into the page
-	 * cache.  It's up to the file system to write the updated size to disk,
-	 * preferably after I/O completion so that no stale data is exposed.
-	 */
-	if (pos + ret > old_size) {
-		i_size_write(iter->inode, pos + ret);
-		iter->iomap.flags |= IOMAP_F_SIZE_CHANGED;
-	}
-	__iomap_put_folio(iter, pos, ret, folio);
 
-	if (old_size < pos)
-		pagecache_isize_extended(iter->inode, old_size, pos);
-	return ret;
+	if (srcmap->type == IOMAP_INLINE)
+		return iomap_write_end_inline(iter, folio, pos, copied);
+	if (srcmap->flags & IOMAP_F_BUFFER_HEAD)
+		return block_write_end(NULL, iter->inode->i_mapping, pos, len,
+				       copied, &folio->page, NULL);
+	return __iomap_write_end(iter->inode, pos, len, copied, folio);
 }
 
 static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
@@ -877,6 +858,7 @@ static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
 
 	do {
 		struct folio *folio;
+		loff_t old_size;
 		size_t offset;		/* Offset into folio */
 		size_t bytes;		/* Bytes to write to folio */
 		size_t copied;		/* Bytes copied from user */
@@ -926,6 +908,22 @@ static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
 		copied = copy_folio_from_iter_atomic(folio, offset, bytes, i);
 		status = iomap_write_end(iter, pos, bytes, copied, folio);
 
+		/*
+		 * Update the in-memory inode size after copying the data into
+		 * the page cache.  It's up to the file system to write the
+		 * updated size to disk, preferably after I/O completion so that
+		 * no stale data is exposed.  Only once that's done can we
+		 * unlock and release the folio.
+		 */
+		old_size = iter->inode->i_size;
+		if (pos + status > old_size) {
+			i_size_write(iter->inode, pos + status);
+			iter->iomap.flags |= IOMAP_F_SIZE_CHANGED;
+		}
+		__iomap_put_folio(iter, pos, status, folio);
+
+		if (old_size < pos)
+			pagecache_isize_extended(iter->inode, old_size, pos);
 		if (status < bytes)
 			iomap_write_failed(iter->inode, pos + status,
 					   bytes - status);
@@ -1298,6 +1296,7 @@ static loff_t iomap_unshare_iter(struct iomap_iter *iter)
 			bytes = folio_size(folio) - offset;
 
 		bytes = iomap_write_end(iter, pos, bytes, bytes, folio);
+		__iomap_put_folio(iter, pos, bytes, folio);
 		if (WARN_ON_ONCE(bytes == 0))
 			return -EIO;
 
@@ -1362,6 +1361,7 @@ static loff_t iomap_zero_iter(struct iomap_iter *iter, bool *did_zero)
 		folio_mark_accessed(folio);
 
 		bytes = iomap_write_end(iter, pos, bytes, bytes, folio);
+		__iomap_put_folio(iter, pos, bytes, folio);
 		if (WARN_ON_ONCE(bytes == 0))
 			return -EIO;
 
-- 
2.39.2

[PATCH v2 08/10] iomap: use a new variable to handle the written bytes in iomap_write_iter()

[Zhang Yi]

From: Zhang Yi <yi.zhang@huawei.com>

In iomap_write_iter(), the status variable used to receive the return
value from iomap_write_end() is confusing, replace it with a new written
variable to represent the written bytes in each cycle, no logic changes.

Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
---
 fs/iomap/buffered-io.c | 33 +++++++++++++++++----------------
 1 file changed, 17 insertions(+), 16 deletions(-)

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index e9112dc78d15..291648c61a32 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -851,7 +851,7 @@ static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
 	loff_t length = iomap_length(iter);
 	size_t chunk = PAGE_SIZE << MAX_PAGECACHE_ORDER;
 	loff_t pos = iter->pos;
-	ssize_t written = 0;
+	ssize_t total_written = 0;
 	long status = 0;
 	struct address_space *mapping = iter->inode->i_mapping;
 	unsigned int bdp_flags = (iter->flags & IOMAP_NOWAIT) ? BDP_ASYNC : 0;
@@ -862,6 +862,7 @@ static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
 		size_t offset;		/* Offset into folio */
 		size_t bytes;		/* Bytes to write to folio */
 		size_t copied;		/* Bytes copied from user */
+		size_t written;		/* Bytes have been written */
 
 		bytes = iov_iter_count(i);
 retry:
@@ -906,7 +907,7 @@ static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
 			flush_dcache_folio(folio);
 
 		copied = copy_folio_from_iter_atomic(folio, offset, bytes, i);
-		status = iomap_write_end(iter, pos, bytes, copied, folio);
+		written = iomap_write_end(iter, pos, bytes, copied, folio);
 
 		/*
 		 * Update the in-memory inode size after copying the data into
@@ -916,22 +917,22 @@ static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
 		 * unlock and release the folio.
 		 */
 		old_size = iter->inode->i_size;
-		if (pos + status > old_size) {
-			i_size_write(iter->inode, pos + status);
+		if (pos + written > old_size) {
+			i_size_write(iter->inode, pos + written);
 			iter->iomap.flags |= IOMAP_F_SIZE_CHANGED;
 		}
-		__iomap_put_folio(iter, pos, status, folio);
+		__iomap_put_folio(iter, pos, written, folio);
 
 		if (old_size < pos)
 			pagecache_isize_extended(iter->inode, old_size, pos);
-		if (status < bytes)
-			iomap_write_failed(iter->inode, pos + status,
-					   bytes - status);
-		if (unlikely(copied != status))
-			iov_iter_revert(i, copied - status);
+		if (written < bytes)
+			iomap_write_failed(iter->inode, pos + written,
+					   bytes - written);
+		if (unlikely(copied != written))
+			iov_iter_revert(i, copied - written);
 
 		cond_resched();
-		if (unlikely(status == 0)) {
+		if (unlikely(written == 0)) {
 			/*
 			 * A short copy made iomap_write_end() reject the
 			 * thing entirely.  Might be memory poisoning
@@ -945,17 +946,17 @@ static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
 				goto retry;
 			}
 		} else {
-			pos += status;
-			written += status;
-			length -= status;
+			pos += written;
+			total_written += written;
+			length -= written;
 		}
 	} while (iov_iter_count(i) && length);
 
 	if (status == -EAGAIN) {
-		iov_iter_revert(i, written);
+		iov_iter_revert(i, total_written);
 		return -EAGAIN;
 	}
-	return written ? written : status;
+	return total_written ? total_written : status;
 }
 
 ssize_t
-- 
2.39.2

[PATCH v2 09/10] iomap: make block_write_end() return a boolean

[Zhang Yi]

From: Zhang Yi <yi.zhang@huawei.com>

For now, we can make sure iomap_write_end() always return 0 or copied
bytes, so instead of return written bytes, convert to return a boolean
to indicate the copied bytes have been written to the pagecache.

Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
---
 fs/iomap/buffered-io.c | 50 +++++++++++++++++++++++++++---------------
 1 file changed, 32 insertions(+), 18 deletions(-)

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 291648c61a32..004673ea8bc1 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -790,7 +790,7 @@ static int iomap_write_begin(struct iomap_iter *iter, loff_t pos,
 	return status;
 }
 
-static size_t __iomap_write_end(struct inode *inode, loff_t pos, size_t len,
+static bool __iomap_write_end(struct inode *inode, loff_t pos, size_t len,
 		size_t copied, struct folio *folio)
 {
 	flush_dcache_folio(folio);
@@ -807,14 +807,14 @@ static size_t __iomap_write_end(struct inode *inode, loff_t pos, size_t len,
 	 * redo the whole thing.
 	 */
 	if (unlikely(copied < len && !folio_test_uptodate(folio)))
-		return 0;
+		return false;
 	iomap_set_range_uptodate(folio, offset_in_folio(folio, pos), len);
 	iomap_set_range_dirty(folio, offset_in_folio(folio, pos), copied);
 	filemap_dirty_folio(inode->i_mapping, folio);
-	return copied;
+	return true;
 }
 
-static size_t iomap_write_end_inline(const struct iomap_iter *iter,
+static void iomap_write_end_inline(const struct iomap_iter *iter,
 		struct folio *folio, loff_t pos, size_t copied)
 {
 	const struct iomap *iomap = &iter->iomap;
@@ -829,21 +829,32 @@ static size_t iomap_write_end_inline(const struct iomap_iter *iter,
 	kunmap_local(addr);
 
 	mark_inode_dirty(iter->inode);
-	return copied;
 }
 
-/* Returns the number of bytes copied.  May be 0.  Cannot be an errno. */
-static size_t iomap_write_end(struct iomap_iter *iter, loff_t pos, size_t len,
+/*
+ * Returns true if all copied bytes have been written to the pagecache,
+ * otherwise return false.
+ */
+static bool iomap_write_end(struct iomap_iter *iter, loff_t pos, size_t len,
 		size_t copied, struct folio *folio)
 {
 	const struct iomap *srcmap = iomap_iter_srcmap(iter);
+	bool ret = true;
 
-	if (srcmap->type == IOMAP_INLINE)
-		return iomap_write_end_inline(iter, folio, pos, copied);
-	if (srcmap->flags & IOMAP_F_BUFFER_HEAD)
-		return block_write_end(NULL, iter->inode->i_mapping, pos, len,
-				       copied, &folio->page, NULL);
-	return __iomap_write_end(iter->inode, pos, len, copied, folio);
+	if (srcmap->type == IOMAP_INLINE) {
+		iomap_write_end_inline(iter, folio, pos, copied);
+	} else if (srcmap->flags & IOMAP_F_BUFFER_HEAD) {
+		size_t bh_written;
+
+		bh_written = block_write_end(NULL, iter->inode->i_mapping, pos,
+					len, copied, &folio->page, NULL);
+		WARN_ON_ONCE(bh_written != copied && bh_written != 0);
+		ret = bh_written == copied;
+	} else {
+		ret = __iomap_write_end(iter->inode, pos, len, copied, folio);
+	}
+
+	return ret;
 }
 
 static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
@@ -907,7 +918,8 @@ static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
 			flush_dcache_folio(folio);
 
 		copied = copy_folio_from_iter_atomic(folio, offset, bytes, i);
-		written = iomap_write_end(iter, pos, bytes, copied, folio);
+		written = iomap_write_end(iter, pos, bytes, copied, folio) ?
+			  copied : 0;
 
 		/*
 		 * Update the in-memory inode size after copying the data into
@@ -1285,6 +1297,7 @@ static loff_t iomap_unshare_iter(struct iomap_iter *iter)
 		int status;
 		size_t offset;
 		size_t bytes = min_t(u64, SIZE_MAX, length);
+		bool ret;
 
 		status = iomap_write_begin(iter, pos, bytes, &folio);
 		if (unlikely(status))
@@ -1296,9 +1309,9 @@ static loff_t iomap_unshare_iter(struct iomap_iter *iter)
 		if (bytes > folio_size(folio) - offset)
 			bytes = folio_size(folio) - offset;
 
-		bytes = iomap_write_end(iter, pos, bytes, bytes, folio);
+		ret = iomap_write_end(iter, pos, bytes, bytes, folio);
 		__iomap_put_folio(iter, pos, bytes, folio);
-		if (WARN_ON_ONCE(bytes == 0))
+		if (WARN_ON_ONCE(!ret))
 			return -EIO;
 
 		cond_resched();
@@ -1347,6 +1360,7 @@ static loff_t iomap_zero_iter(struct iomap_iter *iter, bool *did_zero)
 		int status;
 		size_t offset;
 		size_t bytes = min_t(u64, SIZE_MAX, length);
+		bool ret;
 
 		status = iomap_write_begin(iter, pos, bytes, &folio);
 		if (status)
@@ -1361,9 +1375,9 @@ static loff_t iomap_zero_iter(struct iomap_iter *iter, bool *did_zero)
 		folio_zero_range(folio, offset, bytes);
 		folio_mark_accessed(folio);
 
-		bytes = iomap_write_end(iter, pos, bytes, bytes, folio);
+		ret = iomap_write_end(iter, pos, bytes, bytes, folio);
 		__iomap_put_folio(iter, pos, bytes, folio);
-		if (WARN_ON_ONCE(bytes == 0))
+		if (WARN_ON_ONCE(!ret))
 			return -EIO;
 
 		pos += bytes;
-- 
2.39.2

[PATCH v2 10/10] iomap: do some small logical cleanup in buffered write

[Zhang Yi]

From: Zhang Yi <yi.zhang@huawei.com>

Since iomap_write_end() can never return a partial write length, the
comperation between written, copied and bytes becomes useless, just
merge them with the unwritten branch.

Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
---
 fs/iomap/buffered-io.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 004673ea8bc1..f2fb89056259 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -937,11 +937,6 @@ static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
 
 		if (old_size < pos)
 			pagecache_isize_extended(iter->inode, old_size, pos);
-		if (written < bytes)
-			iomap_write_failed(iter->inode, pos + written,
-					   bytes - written);
-		if (unlikely(copied != written))
-			iov_iter_revert(i, copied - written);
 
 		cond_resched();
 		if (unlikely(written == 0)) {
@@ -951,6 +946,9 @@ static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
 			 * halfway through, might be a race with munmap,
 			 * might be severe memory pressure.
 			 */
+			iomap_write_failed(iter->inode, pos, bytes);
+			iov_iter_revert(i, copied);
+
 			if (chunk > PAGE_SIZE)
 				chunk /= 2;
 			if (copied) {
-- 
2.39.2

Re: [PATCH v2 02/10] xfs: allow xfs_bmapi_convert_delalloc() to pass NULL seq

[Christoph Hellwig]

The patch looks good to me:

Reviewed-by: Christoph Hellwig <hch@lst.de>

But maybe I'd reword the commit message a bit, i.e.:

xfs: make the seq argument to xfs_bmapi_convert_delalloc optional

Allow callers to pass a NULLL seq argument if they don't care about
the fork sequence number.

Re: [PATCH v2 03/10] xfs: make xfs_bmapi_convert_delalloc() to allocate the target offset

[Christoph Hellwig]

Looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH v2 04/10] xfs: drop xfs_convert_blocks()

[Christoph Hellwig]

Maybe just fold this into the previous patch?

Otherwise this looks good to me.

Re: [PATCH v2 05/10] xfs: convert delayed extents to unwritten when zeroing post eof blocks

[Christoph Hellwig]

Looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH v2 06/10] iomap: drop the write failure handles when unsharing and zeroing

[Christoph Hellwig]

Looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH v2 07/10] iomap: don't increase i_size if it's not a write operation

[Christoph Hellwig]

Looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH v2 08/10] iomap: use a new variable to handle the written bytes in iomap_write_iter()

[Christoph Hellwig]

Looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH v2 09/10] iomap: make block_write_end() return a boolean

[Christoph Hellwig]

Looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH v2 10/10] iomap: do some small logical cleanup in buffered write

[Christoph Hellwig]

Looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH v2 02/10] xfs: allow xfs_bmapi_convert_delalloc() to pass NULL seq

[Zhang Yi]

On 2024/3/18 9:28, Christoph Hellwig wrote:
> The patch looks good to me:
> 
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> 
> But maybe I'd reword the commit message a bit, i.e.:
> 
> xfs: make the seq argument to xfs_bmapi_convert_delalloc optional
> 
> Allow callers to pass a NULLL seq argument if they don't care about
> the fork sequence number.
> 

Okay, that's clearer.

Thanks,
Yi.

Re: [PATCH v2 04/10] xfs: drop xfs_convert_blocks()

[Zhang Yi]

On 2024/3/18 9:33, Christoph Hellwig wrote:
> Maybe just fold this into the previous patch?
> 
> Otherwise this looks good to me.
> 
Okay, it's fine by me to fold them

Thanks,
Yi.