io_uring: avoid io-wq -EAGAIN looping for !IOPOLL

[ Upstream commit e0deb6a025ae8c850dc8685be39fb27b06c88736 ]

If an opcode handler semi-reliably returns -EAGAIN, io_wq_submit_work()
might continue busily hammer the same handler over and over again, which
is not ideal. The -EAGAIN handling in question was put there only for
IOPOLL, so restrict it to IOPOLL mode only where there is no other
recourse than to retry as we cannot wait.

Fixes: def596e9557c9 ("io_uring: support for IO polling")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/f168b4f24181942f3614dd8ff648221736f572e6.1652433740.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index e0823f58f7959804ecde3eefdc450cf4476f6652..7272e410d24aa0aad644802b4a1bb2d32d6aaafb 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -7327,6 +7327,8 @@ fail:
                 * wait for request slots on the block side.
                 */
                if (!needs_poll) {
+                       if (!(req->ctx->flags & IORING_SETUP_IOPOLL))
+                               break;
                        cond_resched();
                        continue;
                }