io_uring: optimise batch completion

First, convert rest of iopoll bits to single linked lists, and also
replace per-request list_add_tail() with splicing a part of slist.

With that, use io_free_batch_list() to put/free requests. The main
advantage of it is that it's now the only user of struct req_batch and
friends, and so they can be inlined. The main overhead there was
per-request call to not-inlined io_req_free_batch(), which is expensive
enough.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/b37fc6d5954b241e025eead7ab92c6f44a42f229.1632516769.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 fb122c2..91077b5 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2421,35 +2421,13 @@ static inline bool io_run_task_work(void)
        return false;
 }
 
-/*
- * Find and free completed poll iocbs
- */
-static void io_iopoll_complete(struct io_ring_ctx *ctx, struct list_head *done)
-{
-       struct req_batch rb;
-       struct io_kiocb *req;
-
-       io_init_req_batch(&rb);
-       while (!list_empty(done)) {
-               req = list_first_entry(done, struct io_kiocb, inflight_entry);
-               list_del(&req->inflight_entry);
-
-               if (req_ref_put_and_test(req))
-                       io_req_free_batch(&rb, req, &ctx->submit_state);
-       }
-
-       io_commit_cqring(ctx);
-       io_cqring_ev_posted_iopoll(ctx);
-       io_req_free_batch_finish(ctx, &rb);
-}
-
 static int io_do_iopoll(struct io_ring_ctx *ctx, bool force_nonspin)
 {
        struct io_wq_work_node *pos, *start, *prev;
        unsigned int poll_flags = BLK_POLL_NOSLEEP;
+       struct io_wq_work_list list;
        DEFINE_IO_COMP_BATCH(iob);
        int nr_events = 0;
-       LIST_HEAD(done);
 
        /*
         * Only spin for completions if we don't have multiple devices hanging
@@ -2496,15 +2474,19 @@ static int io_do_iopoll(struct io_ring_ctx *ctx, bool force_nonspin)
                if (!smp_load_acquire(&req->iopoll_completed))
                        break;
                __io_cqring_fill_event(ctx, req->user_data, req->result,
-                                      io_put_rw_kbuf(req));
-
-               list_add_tail(&req->inflight_entry, &done);
+                                       io_put_rw_kbuf(req));
                nr_events++;
        }
 
+       if (unlikely(!nr_events))
+               return 0;
+
+       io_commit_cqring(ctx);
+       io_cqring_ev_posted_iopoll(ctx);
+       list.first = start ? start->next : ctx->iopoll_list.first;
+       list.last = prev;
        wq_list_cut(&ctx->iopoll_list, prev, start);
-       if (nr_events)
-               io_iopoll_complete(ctx, &done);
+       io_free_batch_list(ctx, &list);
        return nr_events;
 }