io_uring: refactor tctx task_work list splicing

We don't need a full copy of tctx->task_list in tctx_task_work(), but
only a first one, so just assign node directly.

Taking into account that task_works are run in a context of a task,
it's very unlikely to first see non-empty tctx->task_list and then
splice it empty, can only happen with task_work cancellations that is
not-normal slow path anyway. Hence, get rid of the check in the end,
it's there not for validity but "performance" purposes.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/d076c83fedb8253baf43acb23b8fafd7c5da1714.1623949695.git.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 49f0648..51db0d8 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1897,15 +1897,13 @@ static void tctx_task_work(struct callback_head *cb)
        clear_bit(0, &tctx->task_state);
 
        while (!wq_list_empty(&tctx->task_list)) {
-               struct io_wq_work_list list;
                struct io_wq_work_node *node;
 
                spin_lock_irq(&tctx->task_lock);
-               list = tctx->task_list;
+               node = tctx->task_list.first;
                INIT_WQ_LIST(&tctx->task_list);
                spin_unlock_irq(&tctx->task_lock);
 
-               node = list.first;
                while (node) {
                        struct io_wq_work_node *next = node->next;
                        struct io_kiocb *req = container_of(node, struct io_kiocb,
@@ -1919,9 +1917,6 @@ static void tctx_task_work(struct callback_head *cb)
                        req->task_work.func(&req->task_work);
                        node = next;
                }
-
-               if (!list.first)
-                       break;
                cond_resched();
        }