io_uring: synchronise IOPOLL on task_submit fail

io_req_task_submit() might be called for IOPOLL, do the fail path under
uring_lock to comply with IOPOLL synchronisation based solely on it.

Cc: stable@vger.kernel.org # 5.5+
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 ca46f314640b150e97d38301d89ada6183497cf7..5be33fd8b6bc625fc523479119acbd3e6f92d7b2 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2126,15 +2126,16 @@ static void io_req_task_cancel(struct callback_head *cb)
 static void __io_req_task_submit(struct io_kiocb *req)
 {
        struct io_ring_ctx *ctx = req->ctx;
+       bool fail;
 
-       if (!__io_sq_thread_acquire_mm(ctx) &&
-           !__io_sq_thread_acquire_files(ctx)) {
-               mutex_lock(&ctx->uring_lock);
+       fail = __io_sq_thread_acquire_mm(ctx) ||
+               __io_sq_thread_acquire_files(ctx);
+       mutex_lock(&ctx->uring_lock);
+       if (!fail)
                __io_queue_sqe(req, NULL);
-               mutex_unlock(&ctx->uring_lock);
-       } else {
+       else
                __io_req_task_cancel(req, -EFAULT);
-       }
+       mutex_unlock(&ctx->uring_lock);
 }
 
 static void io_req_task_submit(struct callback_head *cb)