linux-ext4 - [PATCH v1 5/5] ext4: Add a WARN_ON_ONCE for querying LAST_IN

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Message-ID: <ee6e82a224c50b432df9ce1ce3333c50182d8473.1747677758.git.ritesh.list@gmail.com>
Date: Mon, 19 May 2025 23:49:30 +0530
From: "Ritesh Harjani (IBM)" <ritesh.list@...il.com>
To: linux-ext4@...r.kernel.org
Cc: Theodore Ts'o <tytso@....edu>,
	Jan Kara <jack@...e.cz>,
	John Garry <john.g.garry@...cle.com>,
	djwong@...nel.org,
	Ojaswin Mujoo <ojaswin@...ux.ibm.com>,
	linux-fsdevel@...r.kernel.org,
	"Ritesh Harjani (IBM)" <ritesh.list@...il.com>
Subject: [PATCH v1 5/5] ext4: Add a WARN_ON_ONCE for querying LAST_IN_LEAF instead

We added the documentation in ext4_map_blocks() for usage of
EXT4_GET_BLOCKS_QUERY_LAST_IN_LEAF flag. But It's better to add
a WARN_ON_ONCE in case if anyone tries using this flag with CREATE to
avoid a random issue later. Since depth can change with CREATE and it
needs to be re-calculated before using it in there.

Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@...il.com>
---
 fs/ext4/extents.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 7683558381dc..ea5158703d2d 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -4444,9 +4444,11 @@ int ext4_ext_map_blocks(handle_t *handle, struct inode *inode,
 	 * need to re-calculate the depth as it might have changed due to block
 	 * allocation.
 	 */
-	if (flags & EXT4_GET_BLOCKS_QUERY_LAST_IN_LEAF)
+	if (flags & EXT4_GET_BLOCKS_QUERY_LAST_IN_LEAF) {
+		WARN_ON_ONCE(flags & EXT4_GET_BLOCKS_CREATE);
 		if (!err && ex && (ex == EXT_LAST_EXTENT(path[depth].p_hdr)))
 			map->m_flags |= EXT4_MAP_QUERY_LAST_IN_LEAF;
+	}
 
 	ext4_free_ext_path(path);
 
-- 
2.49.0