[PATCH 1/2] io_uring/rw: fix link failure on successful pipe short reads

__io_read() treats a short read on pipes and sockets as success and
returns without filling the iov. However, __io_complete_rw_common()
compared the transfer length against the original iov size and set
REQ_F_FAIL when they did not match. That incorrectly failed linked
requests behind a successful head request, for example a nop after a
naturally disarmed link timeout.

Treat short reads and writes on non-regular files as success in
__io_complete_rw_common(), matching the issue path.

Signed-off-by: Yang Xiuwei <[email protected]>
---
 io_uring/rw.c | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/io_uring/rw.c b/io_uring/rw.c
index 0c4834645279..dd3f24b380b1 100644
--- a/io_uring/rw.c
+++ b/io_uring/rw.c
@@ -547,10 +547,23 @@ static void io_req_io_end(struct io_kiocb *req)
 	}
 }
 
+static bool need_complete_io(struct io_kiocb *req)
+{
+	return req->flags & REQ_F_ISREG ||
+		S_ISBLK(file_inode(req->file)->i_mode);
+}
+
 static void __io_complete_rw_common(struct io_kiocb *req, long res)
 {
 	if (res == req->cqe.res)
 		return;
+	/*
+	 * For non-regular files, __io_read()/__io_write() may return a short
+	 * transfer without looping to fill the iter. That is success, not a
+	 * failure to be propagated to linked requests.
+	 */
+	if (res > 0 && res < req->cqe.res && !need_complete_io(req))
+		return;
 	if ((res == -EOPNOTSUPP || res == -EAGAIN) && io_rw_should_reissue(req)) {
 		req->flags |= REQ_F_REISSUE | REQ_F_BL_NO_RECYCLE;
 	} else {
@@ -839,12 +852,6 @@ static inline int io_iter_do_read(struct io_rw *rw, struct iov_iter *iter)
 		return -EINVAL;
 }
 
-static bool need_complete_io(struct io_kiocb *req)
-{
-	return req->flags & REQ_F_ISREG ||
-		S_ISBLK(file_inode(req->file)->i_mode);
-}
-
 static int io_rw_init_file(struct io_kiocb *req, fmode_t mode, int rw_type)
 {
 	struct io_rw *rw = io_kiocb_to_cmd(req, struct io_rw);
-- 
2.25.1