Re: [RFC 2/2] io_uring: acquire ctx->uring_lock before calling io_issue_sqe()

[Jens Axboe <axboe@kernel.dk>]

On 1/15/20 9:34 PM, Jens Axboe wrote:
> On 1/15/20 7:37 PM, Bijan Mottahedeh wrote:
>> io_issue_sqe() calls io_iopoll_req_issued() which manipulates poll_list,
>> so acquire ctx->uring_lock beforehand similar to other instances of
>> calling io_issue_sqe().
> 
> Is the below not enough?

This should be better, we have two that set ->in_async, and only one
doesn't hold the mutex.

If this works for you, can you resend patch 2 with that? Also add a:

Fixes: 8a4955ff1cca ("io_uring: sqthread should grab ctx->uring_lock for submissions")

to it as well. Thanks!

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 3130ed16456e..52e5764540e4 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -3286,10 +3286,19 @@ static int io_issue_sqe(struct io_kiocb *req, const struct io_uring_sqe *sqe,
 		return ret;
 
 	if (ctx->flags & IORING_SETUP_IOPOLL) {
+		const bool in_async = io_wq_current_is_worker();
+
 		if (req->result == -EAGAIN)
 			return -EAGAIN;
 
+		/* workqueue context doesn't hold uring_lock, grab it now */
+		if (in_async)
+			mutex_lock(&ctx->uring_lock);
+
 		io_iopoll_req_issued(req);
+
+		if (in_async)
+			mutex_unlock(&ctx->uring_lock);
 	}
 
 	return 0;

-- 
Jens Axboe