[PATCH] ext4: return 0 instead of stale ret in ext4_iomap_writepages()

[Zhang Yi]

From: Zhang Yi <yi.zhang@xxxxxxxxxx>

smatch reports a "missing error code" warning:

  fs/ext4/inode.c:4518 ext4_iomap_writepages() warn: missing error code? 'ret'

The 'ret' variable has already been consumed by the ext4_emergency_state()
check at the beginning of the function, so its value is always zero at this
point.  Returning it is equivalent to returning 0, but it is misleading
because it looks like an error code is being propagated.

This branch handles the race with ext4_change_inode_journal_flag(), which
flushes the dirty data and drops the page cache before switching the inode
to the buffer_head path, so there is genuinely nothing to write back here.
Return 0 explicitly to make the intent clear.

Fixes: bdcbb0f19e92 ("ext4: partially enable iomap for the buffered I/O path of regular files")
Reported-by: kernel test robot <lkp@xxxxxxxxx>
Reported-by: Dan Carpenter <error27@xxxxxxxxx>
Closes: https://lore.kernel.org/r/202610160314.PLMEXaOJ-lkp@xxxxxxxxx/
Signed-off-by: Zhang Yi <yi.zhang@xxxxxxxxxx>
---
 fs/ext4/inode.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 1853fbdc2a5af..fb0fdfc43566b 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4515,7 +4515,7 @@ static int ext4_iomap_writepages(struct address_space *mapping,
 	 */
 	if (!ext4_inode_buffered_iomap(inode)) {
 		ext4_writepages_up_read(sb, alloc_ctx);
-		return ret;
+		return 0;
 	}
 
 	trace_ext4_writepages(inode, wbc);
-- 
2.52.0