f2fs: fix out-of-order execution in f2fs_issue_flush

PATCH New Chao Yu 1 participant 1 message Aug 21, 2017 F2FS file system

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Chao Yu

author maintainer

2017-08-21 14:53 UTC #0 lore raw

PATCH 1/1 f2fs: fix out-of-order execution in f2fs_issue_flush

From: Chao Yu <[email protected]>

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 <[email protected]>

---
 fs/f2fs/segment.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

fs/f2fs/segment.c +4 -1

index dd97d2f282a6..29de70b7a6c0 100644
@@ -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) {

Signature · 1 line

2.14.1.145.gb3622a4ee