FAILED: patch "[PATCH] ext4: don't set EXT4_GET_BLOCKS_CONVERT when splitting before" failed to apply to 6.18-stable tree

FAILED: patch "[PATCH] ext4: don't set EXT4_GET_BLOCKS_CONVERT when splitting before" failed to apply to 6.18-stable tree

[gregkh]

The patch below does not apply to the 6.18-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.18.y
git checkout FETCH_HEAD
git cherry-pick -x feaf2a80e78f89ee8a3464126077ba8683b62791
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026022418-mulberry-curliness-5860@gregkh' --subject-prefix 'PATCH 6.18.y' HEAD^..

Possible dependencies:



thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From feaf2a80e78f89ee8a3464126077ba8683b62791 Mon Sep 17 00:00:00 2001
From: Zhang Yi <yi.zhang@huawei.com>
Date: Sat, 29 Nov 2025 18:32:35 +0800
Subject: [PATCH] ext4: don't set EXT4_GET_BLOCKS_CONVERT when splitting before
 submitting I/O

When allocating blocks during within-EOF DIO and writeback with
dioread_nolock enabled, EXT4_GET_BLOCKS_PRE_IO was set to split an
existing large unwritten extent. However, EXT4_GET_BLOCKS_CONVERT was
set when calling ext4_split_convert_extents(), which may potentially
result in stale data issues.

Assume we have an unwritten extent, and then DIO writes the second half.

   [UUUUUUUUUUUUUUUU] on-disk extent        U: unwritten extent
   [UUUUUUUUUUUUUUUU] extent status tree
            |<-   ->| ----> dio write this range

First, ext4_iomap_alloc() call ext4_map_blocks() with
EXT4_GET_BLOCKS_PRE_IO, EXT4_GET_BLOCKS_UNWRIT_EXT and
EXT4_GET_BLOCKS_CREATE flags set. ext4_map_blocks() find this extent and
call ext4_split_convert_extents() with EXT4_GET_BLOCKS_CONVERT and the
above flags set.

Then, ext4_split_convert_extents() calls ext4_split_extent() with
EXT4_EXT_MAY_ZEROOUT, EXT4_EXT_MARK_UNWRIT2 and EXT4_EXT_DATA_VALID2
flags set, and it calls ext4_split_extent_at() to split the second half
with EXT4_EXT_DATA_VALID2, EXT4_EXT_MARK_UNWRIT1, EXT4_EXT_MAY_ZEROOUT
and EXT4_EXT_MARK_UNWRIT2 flags set. However, ext4_split_extent_at()
failed to insert extent since a temporary lack -ENOSPC. It zeroes out
the first half but convert the entire on-disk extent to written since
the EXT4_EXT_DATA_VALID2 flag set, but left the second half as unwritten
in the extent status tree.

   [0000000000SSSSSS]  data                S: stale data, 0: zeroed
   [WWWWWWWWWWWWWWWW]  on-disk extent      W: written extent
   [WWWWWWWWWWUUUUUU]  extent status tree

Finally, if the DIO failed to write data to the disk, the stale data in
the second half will be exposed once the cached extent entry is gone.

Fix this issue by not passing EXT4_GET_BLOCKS_CONVERT when splitting
an unwritten extent before submitting I/O, and make
ext4_split_convert_extents() to zero out the entire extent range
to zero for this case, and also mark the extent in the extent status
tree for consistency.

Fixes: b8a8684502a0 ("ext4: Introduce FALLOC_FL_ZERO_RANGE flag for fallocate")
Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
Reviewed-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Reviewed-by: Baokun Li <libaokun1@huawei.com>
Cc: stable@kernel.org
Message-ID: <20251129103247.686136-4-yi.zhang@huaweicloud.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 1fee84ea20af..91b56de60c90 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -3746,15 +3746,19 @@ static struct ext4_ext_path *ext4_split_convert_extents(handle_t *handle,
 	/* Convert to unwritten */
 	if (flags & EXT4_GET_BLOCKS_CONVERT_UNWRITTEN) {
 		split_flag |= EXT4_EXT_DATA_ENTIRE_VALID1;
-	/* Convert to initialized */
-	} else if (flags & EXT4_GET_BLOCKS_CONVERT) {
+	/* Split the existing unwritten extent */
+	} else if (flags & (EXT4_GET_BLOCKS_UNWRIT_EXT |
+			    EXT4_GET_BLOCKS_CONVERT)) {
 		/*
 		 * It is safe to convert extent to initialized via explicit
 		 * zeroout only if extent is fully inside i_size or new_size.
 		 */
 		split_flag |= ee_block + ee_len <= eof_block ?
 			      EXT4_EXT_MAY_ZEROOUT : 0;
-		split_flag |= (EXT4_EXT_MARK_UNWRIT2 | EXT4_EXT_DATA_VALID2);
+		split_flag |= EXT4_EXT_MARK_UNWRIT2;
+		/* Convert to initialized */
+		if (flags & EXT4_GET_BLOCKS_CONVERT)
+			split_flag |= EXT4_EXT_DATA_VALID2;
 	}
 	flags |= EXT4_GET_BLOCKS_SPLIT_NOMERGE;
 	return ext4_split_extent(handle, inode, path, map, split_flag, flags,
@@ -3930,7 +3934,7 @@ ext4_ext_handle_unwritten_extents(handle_t *handle, struct inode *inode,
 	/* get_block() before submitting IO, split the extent */
 	if (flags & EXT4_GET_BLOCKS_SPLIT_NOMERGE) {
 		path = ext4_split_convert_extents(handle, inode, map, path,
-				flags | EXT4_GET_BLOCKS_CONVERT, allocated);
+						  flags, allocated);
 		if (IS_ERR(path))
 			return path;
 		/*

[PATCH 6.18.y 1/3] ext4: correct the comments place for EXT4_EXT_MAY_ZEROOUT

[Sasha Levin]

From: Yang Erkun <yangerkun@huawei.com>

[ Upstream commit cc742fd1d184bb2a11bacf50587d2c85290622e4 ]

Move the comments just before we set EXT4_EXT_MAY_ZEROOUT in
ext4_split_convert_extents.

Signed-off-by: Yang Erkun <yangerkun@huawei.com>
Message-ID: <20251112084538.1658232-4-yangerkun@huawei.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Stable-dep-of: feaf2a80e78f ("ext4: don't set EXT4_GET_BLOCKS_CONVERT when splitting before submitting I/O")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/ext4/extents.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index ca5499e9412b0..bce4cd8851380 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -3721,10 +3721,6 @@ static struct ext4_ext_path *ext4_split_convert_extents(handle_t *handle,
 			>> inode->i_sb->s_blocksize_bits;
 	if (eof_block < map->m_lblk + map->m_len)
 		eof_block = map->m_lblk + map->m_len;
-	/*
-	 * It is safe to convert extent to initialized via explicit
-	 * zeroout only if extent is fully inside i_size or new_size.
-	 */
 	depth = ext_depth(inode);
 	ex = path[depth].p_ext;
 	ee_block = le32_to_cpu(ex->ee_block);
@@ -3735,6 +3731,10 @@ static struct ext4_ext_path *ext4_split_convert_extents(handle_t *handle,
 		split_flag |= EXT4_EXT_DATA_VALID1;
 	/* Convert to initialized */
 	} else if (flags & EXT4_GET_BLOCKS_CONVERT) {
+		/*
+		 * It is safe to convert extent to initialized via explicit
+		 * zeroout only if extent is fully inside i_size or new_size.
+		 */
 		split_flag |= ee_block + ee_len <= eof_block ?
 			      EXT4_EXT_MAY_ZEROOUT : 0;
 		split_flag |= (EXT4_EXT_MARK_UNWRIT2 | EXT4_EXT_DATA_VALID2);
-- 
2.51.0

[PATCH 6.18.y 2/3] ext4: subdivide EXT4_EXT_DATA_VALID1

[Sasha Levin]

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

[ Upstream commit 22784ca541c0f01c5ebad14e8228298dc0a390ed ]

When splitting an extent, if the EXT4_GET_BLOCKS_CONVERT flag is set and
it is necessary to split the target extent in the middle,
ext4_split_extent() first handles splitting the latter half of the
extent and passes the EXT4_EXT_DATA_VALID1 flag. This flag implies that
all blocks before the split point contain valid data; however, this
assumption is incorrect.

Therefore, subdivid EXT4_EXT_DATA_VALID1 into
EXT4_EXT_DATA_ENTIRE_VALID1 and EXT4_EXT_DATA_PARTIAL_VALID1, which
indicate that the first half of the extent is either entirely valid or
only partially valid, respectively. These two flags cannot be set
simultaneously.

This patch does not use EXT4_EXT_DATA_PARTIAL_VALID1, it only replaces
EXT4_EXT_DATA_VALID1 with EXT4_EXT_DATA_ENTIRE_VALID1 at the location
where it is set, no logical changes.

Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
Reviewed-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Reviewed-by: Baokun Li <libaokun1@huawei.com>
Cc: stable@kernel.org
Message-ID: <20251129103247.686136-2-yi.zhang@huaweicloud.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Stable-dep-of: feaf2a80e78f ("ext4: don't set EXT4_GET_BLOCKS_CONVERT when splitting before submitting I/O")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/ext4/extents.c | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index bce4cd8851380..5ce147bf48162 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -43,8 +43,13 @@
 #define EXT4_EXT_MARK_UNWRIT1	0x2  /* mark first half unwritten */
 #define EXT4_EXT_MARK_UNWRIT2	0x4  /* mark second half unwritten */
 
-#define EXT4_EXT_DATA_VALID1	0x8  /* first half contains valid data */
-#define EXT4_EXT_DATA_VALID2	0x10 /* second half contains valid data */
+/* first half contains valid data */
+#define EXT4_EXT_DATA_ENTIRE_VALID1	0x8   /* has entirely valid data */
+#define EXT4_EXT_DATA_PARTIAL_VALID1	0x10  /* has partially valid data */
+#define EXT4_EXT_DATA_VALID1		(EXT4_EXT_DATA_ENTIRE_VALID1 | \
+					 EXT4_EXT_DATA_PARTIAL_VALID1)
+
+#define EXT4_EXT_DATA_VALID2	0x20 /* second half contains valid data */
 
 static __le32 ext4_extent_block_csum(struct inode *inode,
 				     struct ext4_extent_header *eh)
@@ -3190,8 +3195,9 @@ static struct ext4_ext_path *ext4_split_extent_at(handle_t *handle,
 	unsigned int ee_len, depth;
 	int err = 0;
 
-	BUG_ON((split_flag & (EXT4_EXT_DATA_VALID1 | EXT4_EXT_DATA_VALID2)) ==
-	       (EXT4_EXT_DATA_VALID1 | EXT4_EXT_DATA_VALID2));
+	BUG_ON((split_flag & EXT4_EXT_DATA_VALID1) == EXT4_EXT_DATA_VALID1);
+	BUG_ON((split_flag & EXT4_EXT_DATA_VALID1) &&
+	       (split_flag & EXT4_EXT_DATA_VALID2));
 
 	ext_debug(inode, "logical block %llu\n", (unsigned long long)split);
 
@@ -3373,7 +3379,7 @@ static struct ext4_ext_path *ext4_split_extent(handle_t *handle,
 			split_flag1 |= EXT4_EXT_MARK_UNWRIT1 |
 				       EXT4_EXT_MARK_UNWRIT2;
 		if (split_flag & EXT4_EXT_DATA_VALID2)
-			split_flag1 |= EXT4_EXT_DATA_VALID1;
+			split_flag1 |= EXT4_EXT_DATA_ENTIRE_VALID1;
 		path = ext4_split_extent_at(handle, inode, path,
 				map->m_lblk + map->m_len, split_flag1, flags1);
 		if (IS_ERR(path))
@@ -3728,7 +3734,7 @@ static struct ext4_ext_path *ext4_split_convert_extents(handle_t *handle,
 
 	/* Convert to unwritten */
 	if (flags & EXT4_GET_BLOCKS_CONVERT_UNWRITTEN) {
-		split_flag |= EXT4_EXT_DATA_VALID1;
+		split_flag |= EXT4_EXT_DATA_ENTIRE_VALID1;
 	/* Convert to initialized */
 	} else if (flags & EXT4_GET_BLOCKS_CONVERT) {
 		/*
-- 
2.51.0

[PATCH 6.18.y 3/3] ext4: don't set EXT4_GET_BLOCKS_CONVERT when splitting before submitting I/O

[Sasha Levin]

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

[ Upstream commit feaf2a80e78f89ee8a3464126077ba8683b62791 ]

When allocating blocks during within-EOF DIO and writeback with
dioread_nolock enabled, EXT4_GET_BLOCKS_PRE_IO was set to split an
existing large unwritten extent. However, EXT4_GET_BLOCKS_CONVERT was
set when calling ext4_split_convert_extents(), which may potentially
result in stale data issues.

Assume we have an unwritten extent, and then DIO writes the second half.

   [UUUUUUUUUUUUUUUU] on-disk extent        U: unwritten extent
   [UUUUUUUUUUUUUUUU] extent status tree
            |<-   ->| ----> dio write this range

First, ext4_iomap_alloc() call ext4_map_blocks() with
EXT4_GET_BLOCKS_PRE_IO, EXT4_GET_BLOCKS_UNWRIT_EXT and
EXT4_GET_BLOCKS_CREATE flags set. ext4_map_blocks() find this extent and
call ext4_split_convert_extents() with EXT4_GET_BLOCKS_CONVERT and the
above flags set.

Then, ext4_split_convert_extents() calls ext4_split_extent() with
EXT4_EXT_MAY_ZEROOUT, EXT4_EXT_MARK_UNWRIT2 and EXT4_EXT_DATA_VALID2
flags set, and it calls ext4_split_extent_at() to split the second half
with EXT4_EXT_DATA_VALID2, EXT4_EXT_MARK_UNWRIT1, EXT4_EXT_MAY_ZEROOUT
and EXT4_EXT_MARK_UNWRIT2 flags set. However, ext4_split_extent_at()
failed to insert extent since a temporary lack -ENOSPC. It zeroes out
the first half but convert the entire on-disk extent to written since
the EXT4_EXT_DATA_VALID2 flag set, but left the second half as unwritten
in the extent status tree.

   [0000000000SSSSSS]  data                S: stale data, 0: zeroed
   [WWWWWWWWWWWWWWWW]  on-disk extent      W: written extent
   [WWWWWWWWWWUUUUUU]  extent status tree

Finally, if the DIO failed to write data to the disk, the stale data in
the second half will be exposed once the cached extent entry is gone.

Fix this issue by not passing EXT4_GET_BLOCKS_CONVERT when splitting
an unwritten extent before submitting I/O, and make
ext4_split_convert_extents() to zero out the entire extent range
to zero for this case, and also mark the extent in the extent status
tree for consistency.

Fixes: b8a8684502a0 ("ext4: Introduce FALLOC_FL_ZERO_RANGE flag for fallocate")
Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
Reviewed-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Reviewed-by: Baokun Li <libaokun1@huawei.com>
Cc: stable@kernel.org
Message-ID: <20251129103247.686136-4-yi.zhang@huaweicloud.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/ext4/extents.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 5ce147bf48162..d24e02b59ceec 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -3735,15 +3735,19 @@ static struct ext4_ext_path *ext4_split_convert_extents(handle_t *handle,
 	/* Convert to unwritten */
 	if (flags & EXT4_GET_BLOCKS_CONVERT_UNWRITTEN) {
 		split_flag |= EXT4_EXT_DATA_ENTIRE_VALID1;
-	/* Convert to initialized */
-	} else if (flags & EXT4_GET_BLOCKS_CONVERT) {
+	/* Split the existing unwritten extent */
+	} else if (flags & (EXT4_GET_BLOCKS_UNWRIT_EXT |
+			    EXT4_GET_BLOCKS_CONVERT)) {
 		/*
 		 * It is safe to convert extent to initialized via explicit
 		 * zeroout only if extent is fully inside i_size or new_size.
 		 */
 		split_flag |= ee_block + ee_len <= eof_block ?
 			      EXT4_EXT_MAY_ZEROOUT : 0;
-		split_flag |= (EXT4_EXT_MARK_UNWRIT2 | EXT4_EXT_DATA_VALID2);
+		split_flag |= EXT4_EXT_MARK_UNWRIT2;
+		/* Convert to initialized */
+		if (flags & EXT4_GET_BLOCKS_CONVERT)
+			split_flag |= EXT4_EXT_DATA_VALID2;
 	}
 	flags |= EXT4_GET_BLOCKS_PRE_IO;
 	return ext4_split_extent(handle, inode, path, map, split_flag, flags,
@@ -3919,7 +3923,7 @@ ext4_ext_handle_unwritten_extents(handle_t *handle, struct inode *inode,
 	/* get_block() before submitting IO, split the extent */
 	if (flags & EXT4_GET_BLOCKS_PRE_IO) {
 		path = ext4_split_convert_extents(handle, inode, map, path,
-				flags | EXT4_GET_BLOCKS_CONVERT, allocated);
+						  flags, allocated);
 		if (IS_ERR(path))
 			return path;
 		/*
-- 
2.51.0