[PATCH 6.6.y] dax: fix wrong error code returned from dax_dedupe_file_range_compare()

[Sasha Levin <sashal@kernel.org>]

From: Jianyun Gao <jianyungao89@gmail.com>

[ Upstream commit 9b036546a02c6c9a5133f9c1e93503896595c6ba ]

When dax_range_compare_iter() returns a negative error code (e.g. -EIO),
dax_dedupe_file_range_compare() incorrectly returns 'ret' which holds the
positive return value from iomap_iter() indicating more iterations remain.
This positive value leaks to the caller, where vfs_dedupe_file_range()
interprets it as success (bytes_deduped = len), causing userspace to
incorrectly believe deduplication completed.

Return 'status' instead to propagate the actual error code.

Fixes: 0e79e3736d54 ("fsdax: dedupe: iter two files at the same time")
Cc: stable@vger.kernel.org
Signed-off-by: Jianyun Gao <jianyungao89@gmail.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Link: https://patch.msgid.link/20261015143426.17620-1-jianyungao89@gmail.com
Signed-off-by: Alison Schofield <alison.schofield@intel.com>
[ sashal: adapted status references to the existing compared variable and processed iterator fields ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/dax.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/dax.c b/fs/dax.c
index 94d552a2e6097..bcb93c105bb44 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -2067,7 +2067,7 @@ int dax_dedupe_file_range_compare(struct inode *src, loff_t srcoff,
 		compared = dax_range_compare_iter(&src_iter, &dst_iter,
 				min(src_iter.len, dst_iter.len), same);
 		if (compared < 0)
-			return ret;
+			return compared;
 		src_iter.processed = dst_iter.processed = compared;
 	}
 	return ret;
-- 
2.53.0