io_uring: avoid taking ctx refs for task-cancel

Don't bother to take a ctx->refs for io_req_task_cancel() because it
take uring_lock before putting a request, and the context is promised to
stay alive until unlock happens.

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 bd14327..db0c4b2 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1985,10 +1985,10 @@ static void io_req_task_cancel(struct callback_head *cb)
        struct io_kiocb *req = container_of(cb, struct io_kiocb, task_work);
        struct io_ring_ctx *ctx = req->ctx;
 
+       /* ctx is guaranteed to stay alive while we hold uring_lock */
        mutex_lock(&ctx->uring_lock);
        __io_req_task_cancel(req, req->result);
        mutex_unlock(&ctx->uring_lock);
-       percpu_ref_put(&ctx->refs);
 }
 
 static void __io_req_task_submit(struct io_kiocb *req)
@@ -2019,14 +2019,12 @@ static void io_req_task_queue(struct io_kiocb *req)
        ret = io_req_task_work_add(req);
        if (unlikely(ret)) {
                req->result = -ECANCELED;
-               percpu_ref_get(&req->ctx->refs);
                io_req_task_work_add_fallback(req, io_req_task_cancel);
        }
 }
 
 static void io_req_task_queue_fail(struct io_kiocb *req, int ret)
 {
-       percpu_ref_get(&req->ctx->refs);
        req->result = ret;
        req->task_work.func = io_req_task_cancel;