f2fs: pin files do not require sbi->writepages lock for ordering

For pinned files, the file mapping is already established before
writing, and since the writes are in IPU, there is no need to acquire
the sbi->writepages lock to guarantee write ordering.

Signed-off-by: Yongpeng Yang <yangyongpeng@xiaomi.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

Author: Yongpeng Yang

fs/f2fs/data.c

@@ -3477,6 +3477,8 @@ static inline bool __should_serialize_io(struct inode *inode,
 	if (IS_NOQUOTA(inode))
 		return false;
 
+	if (f2fs_is_pinned_file(inode))
+		return false;
 	if (f2fs_need_compress_data(inode))
 		return true;
 	if (wbc->sync_mode != WB_SYNC_ALL)