[PATCH] f2fs: try grabbing node page lock aggressively in sync scenario

[Chao Yu]

In synchronous scenario, like in checkpoint(), we are going to flush
dirty node pages to device synchronously, we can easily failed
writebacking node page due to trylock_page() failure, especially in
condition of intensive lock competition, which can cause long latency
of checkpoint(). So let's use lock_page() in synchronous scenario to
avoid this issue.

Signed-off-by: Yunlei He <heyunlei@xxxxxxxxxx>
Signed-off-by: Chao Yu <yuchao0@xxxxxxxxxx>
---
 fs/f2fs/node.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
index eeee582cee32..237d19eb13b5 100644
--- a/fs/f2fs/node.c
+++ b/fs/f2fs/node.c
@@ -1651,7 +1651,9 @@ int f2fs_sync_node_pages(struct f2fs_sb_info *sbi,
 						!is_cold_node(page)))
 				continue;
 lock_node:
-			if (!trylock_page(page))
+			if (wbc->sync_mode == WB_SYNC_ALL)
+				lock_page(page);
+			else if (!trylock_page(page))
 				continue;
 
 			if (unlikely(page->mapping != NODE_MAPPING(sbi))) {
-- 
2.18.0.rc1