io_uring: don't wait when under-submitting

[ Upstream commit 7c504e65206a4379ff38fe41d21b32b6c2c3e53e ]

There is no reliable way to submit and wait in a single syscall, as
io_submit_sqes() may under-consume sqes (in case of an early error).
Then it will wait for not-yet-submitted requests, deadlocking the user
in most cases.

Don't wait/poll if can't submit all sqes

Signed-off-by: Pavel Begunkov <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 a60c6315a348ab32c5288377ee93ed941dc2b76a..709671faaed629bcc2673d893168c8807c0bb4bd 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -3721,6 +3721,9 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit,
                mutex_lock(&ctx->uring_lock);
                submitted = io_ring_submit(ctx, to_submit);
                mutex_unlock(&ctx->uring_lock);
+
+               if (submitted != to_submit)
+                       goto out;
        }
        if (flags & IORING_ENTER_GETEVENTS) {
                unsigned nr_events = 0;
@@ -3734,6 +3737,7 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit,
                }
        }
 
+out:
        percpu_ref_put(&ctx->refs);
 out_fput:
        fdput(f);