[PATCH v4 01/10] netfs: Fix uninitialized return value in netfs_unbuffered_write()

[David Howells <dhowells@redhat.com>]

From: Karl Mehltretter <kmehltretter@gmail.com>

If preparation of the first subrequest fails,
netfs_unbuffered_write() exits its loop before ret is initialized. The
empty-iterator check can do the same.

For synchronous writes, netfs_unbuffered_write_iter_locked() may then
return an unrelated error instead of wreq->error. This is reachable
through CIFS if cifs_prepare_write() fails to reopen the file or obtain
credits.

Initialize ret to 0 so the caller returns wreq->error if no data was
written, or the number of bytes already written otherwise.

Found with Clang's -Wconditional-uninitialized.

Fixes: a0b4c7a49137e ("netfs: Fix unbuffered/DIO writes to dispatch subrequests in strict sequence")
Cc: stable@vger.kernel.org
Assisted-by: Claude:claude-fable-5
Signed-off-by: Karl Mehltretter <kmehltretter@gmail.com>
Signed-off-by: David Howells <dhowells@redhat.com>
---
 fs/netfs/direct_write.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/netfs/direct_write.c b/fs/netfs/direct_write.c
index c16fbad286a1..b04019097ab8 100644
--- a/fs/netfs/direct_write.c
+++ b/fs/netfs/direct_write.c
@@ -95,7 +95,7 @@ static int netfs_unbuffered_write(struct netfs_io_request *wreq)
 {
 	struct netfs_io_subrequest *subreq = NULL;
 	struct netfs_io_stream *stream = &wreq->io_streams[0];
-	int ret;
+	int ret = 0;
 
 	_enter("%llx", wreq->len);