linux-kernel - [PATCH 3/6] fuse: Wake up req->waitq of only not background requests in request

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Date:   Tue, 06 Nov 2018 12:30:44 +0300
From:   Kirill Tkhai <ktkhai@...tuozzo.com>
To:     miklos@...redi.hu, ktkhai@...tuozzo.com,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 3/6] fuse: Wake up req->waitq of only not background
 requests in request_end()

Currently, we wait on req->waitq in request_wait_answer()
function only, and it's never used for background requests.
Since wake_up() is not a light-weight macros, instead of this,
it unfolds in really called function, which makes locking
operations taking some cpu cycles, let's avoid its call
for the case we definitely know it's completely useless.

Signed-off-by: Kirill Tkhai <ktkhai@...tuozzo.com>
---
 fs/fuse/dev.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index 391498e680ec..739968ee8b0c 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -464,8 +464,11 @@ static void request_end(struct fuse_conn *fc, struct fuse_req *req)
 		fc->active_background--;
 		flush_bg_queue(fc);
 		spin_unlock(&fc->bg_lock);
+	} else {
+		/* Wake up waiter sleeping in request_wait_answer() */
+		wake_up(&req->waitq);
 	}
-	wake_up(&req->waitq);
+
 	if (req->end)
 		req->end(fc, req);
 put_request: