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

BugLink: https://bugs.launchpad.net/bugs/1987451
[ 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>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 0c5dcda0b62215cdbaf21010a9a2c4957e0b38da..9bff14c5e2b265cd56d590110666cd0e26534511 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -6866,7 +6866,7 @@ static void io_wq_submit_work(struct io_wq_work *work)
                         * forcing a sync submission from here, since we can't
                         * wait for request slots on the block side.
                         */
-                       if (ret != -EAGAIN)
+                       if (ret != -EAGAIN || !(req->ctx->flags & IORING_SETUP_IOPOLL))
                                break;
                        cond_resched();
                } while (1);