[PATCH 3/3] f2fs: update comments for explicit memory barrier

[Chao Yu]

Add more detailed comments for explicit memory barrier used by
f2fs, in order to enhance code readability.

Signed-off-by: Chao Yu <yuchao0@xxxxxxxxxx>
---
 fs/f2fs/checkpoint.c | 6 +++++-
 fs/f2fs/segment.c    | 6 +++++-
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
index 174a0819ad96..c75866cd72fa 100644
--- a/fs/f2fs/checkpoint.c
+++ b/fs/f2fs/checkpoint.c
@@ -1818,7 +1818,11 @@ int f2fs_issue_checkpoint(struct f2fs_sb_info *sbi)
 	llist_add(&req.llnode, &cprc->issue_list);
 	atomic_inc(&cprc->queued_ckpt);
 
-	/* update issue_list before we wake up issue_checkpoint thread */
+	/*
+	 * update issue_list before we wake up issue_checkpoint thread,
+	 * this smp_mb() pairs with another barrier in ___wait_event(),
+	 * see more details in comments of waitqueue_active().
+	 */
 	smp_mb();
 
 	if (waitqueue_active(&cprc->ckpt_wait_queue))
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 2190910c68b0..2d5a82c4ca15 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -663,7 +663,11 @@ int f2fs_issue_flush(struct f2fs_sb_info *sbi, nid_t ino)
 
 	llist_add(&cmd.llnode, &fcc->issue_list);
 
-	/* update issue_list before we wake up issue_flush thread */
+	/*
+	 * update issue_list before we wake up issue_flush thread, this
+	 * smp_mb() pairs with another barrier in ___wait_event(), see
+	 * more details in comments of waitqueue_active().
+	 */
 	smp_mb();
 
 	if (waitqueue_active(&fcc->flush_wait_queue))
-- 
2.29.2