io_uring: sqthread should grab ctx->uring_lock for submissions

axboe · axboe · commit 8a4955ff1cca · 2019-12-10T16:33:23.000-07:00
We use the mutex to guard against registered file updates, for instance.
Ensure we're safe in accessing that state against concurrent updates.

Signed-off-by: Jens Axboe &lt;axboe@kernel.dk&gt;
diff --git a/fs/io_uring.c b/fs/io_uring.c
@@ -2996,12 +2996,7 @@ static int io_issue_sqe(struct io_kiocb *req, struct io_kiocb **nxt,
 		if (req->result == -EAGAIN)
 			return -EAGAIN;
 
-		/* workqueue context doesn't hold uring_lock, grab it now */
-		if (req->in_async)
-			mutex_lock(&ctx->uring_lock);
 		io_iopoll_req_issued(req);
-		if (req->in_async)
-			mutex_unlock(&ctx->uring_lock);
 	}
 
 	return 0;
@@ -3655,7 +3650,9 @@ static int io_sq_thread(void *data)
 		}
 
 		to_submit = min(to_submit, ctx->sq_entries);
+		mutex_lock(&ctx->uring_lock);
 		ret = io_submit_sqes(ctx, to_submit, NULL, -1, &cur_mm, true);
+		mutex_unlock(&ctx->uring_lock);
 		if (ret > 0)
 			inflight += ret;
 	}

Original file line number	Diff line number	Diff line change
`@@ -2996,12 +2996,7 @@ static int io_issue_sqe(struct io_kiocb req, struct io_kiocb *nxt,`
`2996`	`2996`	`if (req->result == -EAGAIN)`
`2997`	`2997`	`return -EAGAIN;`
`2998`	`2998`
`2999`		`- /* workqueue context doesn't hold uring_lock, grab it now */`
`3000`		`- if (req->in_async)`
`3001`		`- mutex_lock(&ctx->uring_lock);`
`3002`	`2999`	`io_iopoll_req_issued(req);`
`3003`		`- if (req->in_async)`
`3004`		`- mutex_unlock(&ctx->uring_lock);`
`3005`	`3000`	`}`
`3006`	`3001`
`3007`	`3002`	`return 0;`
`@@ -3655,7 +3650,9 @@ static int io_sq_thread(void *data)`
`3655`	`3650`	`}`
`3656`	`3651`
`3657`	`3652`	`to_submit = min(to_submit, ctx->sq_entries);`
	`3653`	`+ mutex_lock(&ctx->uring_lock);`
`3658`	`3654`	`ret = io_submit_sqes(ctx, to_submit, NULL, -1, &cur_mm, true);`
	`3655`	`+ mutex_unlock(&ctx->uring_lock);`
`3659`	`3656`	`if (ret > 0)`
`3660`	`3657`	`inflight += ret;`
`3661`	`3658`	`}`