From: Chao Yu <yuchao0@huawei.com>
Date: Mon, 21 Aug 2017 14:53:45 +0000 (+0800)
Subject: f2fs: fix out-of-order execution in f2fs_issue_flush
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=6f890df0a7efe3181aceb5d8bcd4af7deb2abce5;p=GitHub%2Fmoto-9609%2Fandroid_kernel_motorola_exynos9610.git

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>
---

diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index e3922f902c8c..be1c49b9402b 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) {