[PATCH 6.12.y 2/2] io_uring/rw: preserve partial result for iopoll

[Sasha Levin <sashal@kernel.org>]

From: Michael Wigham <michael@wigham.net>

[ Upstream commit c554246ff4c68abf71b61a89c6e39d3cf94f523e ]

A partial read will store the completed byte count in io->bytes_done.
The regular completion path applies io_fixup_rw_res() so that, when the
following operation reaches EOF, the number of bytes already read is
returned.

The iopoll completion path does not apply this fixup to the return value
and can return zero instead.

Use the fixup result when updating the CQE, and the raw result for the
reissue check.

Cc: stable@vger.kernel.org
Fixes: 4d9cb92ca41d ("io_uring/rw: fix short rw error handling")
Signed-off-by: Michael Wigham <michael@wigham.net>
Link: https://patch.msgid.link/20260613225240.34032-1-michael@wigham.net
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 io_uring/rw.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/io_uring/rw.c b/io_uring/rw.c
index 0afbb1ae76618f..a744cb5d235a6a 100644
--- a/io_uring/rw.c
+++ b/io_uring/rw.c
@@ -546,15 +546,15 @@ static void io_complete_rw_iopoll(struct kiocb *kiocb, long res)
 {
 	struct io_rw *rw = container_of(kiocb, struct io_rw, kiocb);
 	struct io_kiocb *req = cmd_to_io_kiocb(rw);
+	int final_res = io_fixup_rw_res(req, res);
 
 	if (kiocb->ki_flags & IOCB_WRITE)
 		io_req_end_write(req);
-	if (unlikely(res != req->cqe.res)) {
-		if (res == -EAGAIN && io_rw_should_reissue(req))
-			req->flags |= REQ_F_REISSUE | REQ_F_BL_NO_RECYCLE;
-		else
-			req->cqe.res = res;
-	}
+
+	if (res == -EAGAIN && io_rw_should_reissue(req))
+		req->flags |= REQ_F_REISSUE | REQ_F_BL_NO_RECYCLE;
+	else if (unlikely(final_res != req->cqe.res))
+		req->cqe.res = final_res;
 
 	/* order with io_iopoll_complete() checking ->iopoll_completed */
 	smp_store_release(&req->iopoll_completed, 1);
-- 
2.53.0