FAILED: patch "[PATCH] ext4: don't set EXT4_GET_BLOCKS_CONVERT when splitting before" failed to apply to 6.12-stable tree

PATCH New [email protected] 2 participants 4 messages Feb 24 – Feb 25

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lore

[email protected]

author maintainer

2026-02-24 21:43 UTC #0 lore raw

The patch below does not apply to the 6.12-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 <[email protected]>.

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-6.12.y
git checkout FETCH_HEAD
git cherry-pick -x feaf2a80e78f89ee8a3464126077ba8683b62791
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026022419-bonsai-gorged-49c6@gregkh' --subject-prefix 'PATCH 6.12.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 <[email protected]>
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 <[email protected]>

Reviewed-by Ojaswin Mujoo <[email protected]>

Reviewed-by Baokun Li <[email protected]>

Cc [email protected]

Message-ID: <[email protected]>

Signed-off-by Theodore Ts'o <[email protected]>

fs/ext4/extents.c +8 -4

index 1fee84ea20af..91b56de60c90 100644
@@ -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;
 		/*

Sasha Levin

maintainer

2026-02-25 01:58 UTC #1 lore raw

PATCH 1/3 ext4: correct the comments place for EXT4_EXT_MAY_ZEROOUT

From: Yang Erkun <[email protected]>

[ Upstream commit cc742fd1d184bb2a11bacf50587d2c85290622e4 ]

Move the comments just before we set EXT4_EXT_MAY_ZEROOUT in ext4_split_convert_extents.

Signed-off-by Yang Erkun <[email protected]>

Message-ID: <[email protected]>

Signed-off-by Theodore Ts'o <[email protected]>

Stable-dep-of: feaf2a80e78f ("ext4: don't set EXT4_GET_BLOCKS_CONVERT when splitting before submitting I/O")

Signed-off-by Sasha Levin <[email protected]>

---
 fs/ext4/extents.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

fs/ext4/extents.c +4 -4

index 2f9c3cd4f26cc..35c6511c4a753 100644
@@ -3719,10 +3719,6 @@ 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);

@@ -3733,6 +3729,10 @@ 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);

Signature · 1 line

2.51.0

Sasha Levin

maintainer

2026-02-25 01:58 UTC #2 lore raw

PATCH 2/3 ext4: subdivide EXT4_EXT_DATA_VALID1

From: Zhang Yi <[email protected]>

[ 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 <[email protected]>

Reviewed-by Ojaswin Mujoo <[email protected]>

Reviewed-by Baokun Li <[email protected]>

Cc [email protected]

Message-ID: <[email protected]>

Signed-off-by Theodore Ts'o <[email protected]>

Stable-dep-of: feaf2a80e78f ("ext4: don't set EXT4_GET_BLOCKS_CONVERT when splitting before submitting I/O")

Signed-off-by Sasha Levin <[email protected]>

---
 fs/ext4/extents.c | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

fs/ext4/extents.c +12 -6

index 35c6511c4a753..f960d06de7dce 100644
@@ -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)

@@ -3188,8 +3193,9 @@ 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);

@@ -3371,7 +3377,7 @@ 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))

@@ -3726,7 +3732,7 @@ 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) {
 		/*

Signature · 1 line

2.51.0

Sasha Levin

maintainer

2026-02-25 01:58 UTC #3 lore raw

PATCH 3/3 ext4: don't set EXT4_GET_BLOCKS_CONVERT when splitting before submitting I/O

In reply to Sasha Levin

From: Zhang Yi <[email protected]>

[ Upstream commit feaf2a80e78f89ee8a3464126077ba8683b62791 ]

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

   [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.

Fixes b8a8684502a0 ("ext4: Introduce FALLOC_FL_ZERO_RANGE flag for fallocate")

Signed-off-by Zhang Yi <[email protected]>

Reviewed-by Ojaswin Mujoo <[email protected]>

Reviewed-by Baokun Li <[email protected]>

Cc [email protected]

Message-ID: <[email protected]>

Signed-off-by Theodore Ts'o <[email protected]>

Signed-off-by Sasha Levin <[email protected]>

---
 fs/ext4/extents.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

fs/ext4/extents.c +8 -4

index f960d06de7dce..ec6c52b17abba 100644
@@ -3733,15 +3733,19 @@ 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,

@@ -3917,7 +3921,7 @@ 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;
 		/*

Signature · 1 line

2.51.0