[PATCH 1/4] 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 b4d581aa5ee1a..6b2f1b07f41e6 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