io_uring: don't wait when under-submitting

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>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 1d4e733..81e7fe6 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -5135,6 +5135,9 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit,
                submitted = io_submit_sqes(ctx, to_submit, f.file, fd,
                                           &cur_mm, false);
                mutex_unlock(&ctx->uring_lock);
+
+               if (submitted != to_submit)
+                       goto out;
        }
        if (flags & IORING_ENTER_GETEVENTS) {
                unsigned nr_events = 0;
@@ -5148,6 +5151,7 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit,
                }
        }
 
+out:
        percpu_ref_put(&ctx->refs);
 out_fput:
        fdput(f);