From 6f890df0a7efe3181aceb5d8bcd4af7deb2abce5 Mon Sep 17 00:00:00 2001
From: Chao Yu <yuchao0@huawei.com>
Date: Mon, 21 Aug 2017 22:53:45 +0800
Subject: [PATCH] f2fs: fix out-of-order execution in f2fs_issue_flush
In f2fs_issue_flush, due to out-of-order execution of CPU, wake_up can
be called before we insert issue_list, result in long latency of
wait_for_completion. Fix this by adding smp_mb() to force the order of
related codes.
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
---
fs/f2fs/segment.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index e3922f902c8c4..be1c49b9402bb 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -549,7 +549,10 @@ int f2fs_issue_flush(struct f2fs_sb_info *sbi)
atomic_inc(&fcc->issing_flush);
llist_add(&cmd.llnode, &fcc->issue_list);
- if (!fcc->dispatch_list)
+ /* update issue_list before we wake up issue_flush thread */
+ smp_mb();
+
+ if (waitqueue_active(&fcc->flush_wait_queue))
wake_up(&fcc->flush_wait_queue);
if (fcc->f2fs_issue_flush) {
--
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