From: Pavel Begunkov <asml.silence@gmail.com>
Date: Wed, 18 Dec 2019 16:53:45 +0000 (+0300)
Subject: io_uring: don't wait when under-submitting
X-Git-Tag: v5.4.11~58
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=002352747481b28287e0285fe95b31206391460c;p=thirdparty%2Fkernel%2Fstable.git

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 a60c6315a348a..709671faaed62 100644
--- 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);