Commit fbb8bb02 authored by Pavel Begunkov's avatar Pavel Begunkov Committed by Jens Axboe
Browse files

io_uring: remove ctx->refs pinning on enter 



io_uring_enter() takes ctx->refs, which was previously preventing racing
with register quiesce. However, as register now doesn't touch the refs,
we can freely kill extra ctx pinning and rely on the fact that we're
holding a file reference preventing the ring from being destroyed.

Signed-off-by: default avatarPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/a11c57ad33a1be53541fce90669c1b79cf4d8940.1656153286.git.asml.silence@gmail.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 3273c440

io_uring/io_uring.c

+4 −12
Original line number Diff line number Diff line
@@ -3049,14 +3049,10 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit, 
			return -EBADF;

		ret = -EOPNOTSUPP;

		if (unlikely(!io_is_uring_fops(f.file)))

			goto out_fput;

			goto out;

	}



	ret = -ENXIO;

	ctx = f.file->private_data;

	if (unlikely(!percpu_ref_tryget(&ctx->refs)))

		goto out_fput;



	ret = -EBADFD;

	if (unlikely(ctx->flags & IORING_SETUP_R_DISABLED))

		goto out;
@@ -3141,10 +3137,7 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit, 
					  &ctx->check_cq);

		}

	}



out:

	percpu_ref_put(&ctx->refs);

out_fput:

	fdput(f);

	return ret;

}
@@ -3730,11 +3723,10 @@ static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode, 
	int ret;



	/*

	 * We're inside the ring mutex, if the ref is already dying, then

	 * someone else killed the ctx or is already going through

	 * io_uring_register().

	 * We don't quiesce the refs for register anymore and so it can't be

	 * dying as we're holding a file ref here.

	 */

	if (percpu_ref_is_dying(&ctx->refs))

	if (WARN_ON_ONCE(percpu_ref_is_dying(&ctx->refs)))

		return -ENXIO;



	if (ctx->restricted) {