From c1e53a6988b9c83dd8bbc759414bc0f13ff1fe0c Mon Sep 17 00:00:00 2001
From: Pavel Begunkov <asml.silence@gmail.com>
Date: Mon, 4 Oct 2021 20:02:55 +0100
Subject: [PATCH] io_uring: optimise io_free_batch_list()
Git-commit: c1e53a6988b9c83dd8bbc759414bc0f13ff1fe0c
Patch-mainline: v5.16-rc1
References: bsc#1205205

Delay reading the next node in io_free_batch_list(), allows the compiler
to load the value a bit later improving register spilling in some cases.
With gcc 11.1 it helped to move @task_refs variable from the stack to a
register and optimises out a couple of per request instructions.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/cc9fdfb6f72a4e8bc9918a5e9f2d97869a263ae4.1633373302.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Gabriel Krisman Bertazi <krisman@suse.de>
---
 fs/io_uring.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index e404c98e846a..1b007f77fe52 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2280,9 +2280,10 @@ static void io_free_batch_list(struct io_ring_ctx *ctx,
 		struct io_kiocb *req = container_of(node, struct io_kiocb,
 						    comp_list);
 
-		node = req->comp_list.next;
-		if (!req_ref_put_and_test(req))
+		if (!req_ref_put_and_test(req)) {
+			node = req->comp_list.next;
 			continue;
+		}
 
 		io_queue_next(req);
 		io_dismantle_req(req);
@@ -2294,6 +2295,7 @@ static void io_free_batch_list(struct io_ring_ctx *ctx,
 			task_refs = 0;
 		}
 		task_refs++;
+		node = req->comp_list.next;
 		wq_stack_add_head(&req->comp_list, &ctx->submit_state.free_list);
 	} while (node);
 
-- 
2.35.3