io_uring: improve io_fail_links()

io_fail_links() is called with ->completion_lock held and for that
reason we'd want to keep it as small as we can. Instead of doing
__io_req_complete_post() for each linked request under the lock, fail
them in a task_work handler under ->uring_lock.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/a2f68708b970a21f4e84ddfa7b3abd67a8fffb27.1656153285.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/io_uring/timeout.c b/io_uring/timeout.c
index 4af074b..2f9e569 100644 (file)
--- a/io_uring/timeout.c
+++ b/io_uring/timeout.c
@@ -101,32 +101,44 @@ __cold void io_flush_timeouts(struct io_ring_ctx *ctx)
        spin_unlock_irq(&ctx->timeout_lock);
 }
 
-static void io_fail_links(struct io_kiocb *req)
-       __must_hold(&req->ctx->completion_lock)
+static void io_req_tw_fail_links(struct io_kiocb *link, bool *locked)
 {
-       struct io_kiocb *nxt, *link = req->link;
-       bool ignore_cqes = req->flags & REQ_F_SKIP_LINK_CQES;
-
-       req->link = NULL;
+       io_tw_lock(link->ctx, locked);
        while (link) {
+               struct io_kiocb *nxt = link->link;
                long res = -ECANCELED;
 
                if (link->flags & REQ_F_FAIL)
                        res = link->cqe.res;
-
-               nxt = link->link;
                link->link = NULL;
+               io_req_set_res(link, res, 0);
+               io_req_task_complete(link, locked);
+               link = nxt;
+       }
+}
 
-               trace_io_uring_fail_link(req, link);
+static void io_fail_links(struct io_kiocb *req)
+       __must_hold(&req->ctx->completion_lock)
+{
+       struct io_kiocb *link = req->link;
+       bool ignore_cqes = req->flags & REQ_F_SKIP_LINK_CQES;
+
+       if (!link)
+               return;
 
+       while (link) {
                if (ignore_cqes)
                        link->flags |= REQ_F_CQE_SKIP;
                else
                        link->flags &= ~REQ_F_CQE_SKIP;
-               io_req_set_res(link, res, 0);
-               __io_req_complete_post(link);
-               link = nxt;
+               trace_io_uring_fail_link(req, link);
+               link = link->link;
        }
+
+       link = req->link;
+       link->io_task_work.func = io_req_tw_fail_links;
+       io_req_task_work_add(link);
+       req->link = NULL;
 }
 
 static inline void io_remove_next_linked(struct io_kiocb *req)