f2fs: keep dirty inodes selectively for checkpoint

This is to avoid no free segment bug during checkpoint caused by a number of
dirty inodes.

The case was reported by Chao like this.
1. mount with lazytime option
2. fill 4k file until disk is full
3. sync filesystem
4. read all files in the image
5. umount

In this case, we actually don't need to flush dirty inode to inode page during
checkpoint.

Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/dir.c

@@ -313,7 +313,7 @@ void f2fs_set_link(struct inode *dir, struct f2fs_dir_entry *de,
 	set_page_dirty(page);
 
 	dir->i_mtime = dir->i_ctime = current_time(dir);
-	f2fs_mark_inode_dirty_sync(dir);
+	f2fs_mark_inode_dirty_sync(dir, false);
 	f2fs_put_page(page, 1);
 }
 
@@ -466,7 +466,7 @@ void update_parent_metadata(struct inode *dir, struct inode *inode,
 		clear_inode_flag(inode, FI_NEW_INODE);
 	}
 	dir->i_mtime = dir->i_ctime = current_time(dir);
-	f2fs_mark_inode_dirty_sync(dir);
+	f2fs_mark_inode_dirty_sync(dir, false);
 
 	if (F2FS_I(dir)->i_current_depth != current_depth)
 		f2fs_i_depth_write(dir, current_depth);
@@ -731,7 +731,7 @@ void f2fs_delete_entry(struct f2fs_dir_entry *dentry, struct page *page,
 	set_page_dirty(page);
 
 	dir->i_ctime = dir->i_mtime = current_time(dir);
-	f2fs_mark_inode_dirty_sync(dir);
+	f2fs_mark_inode_dirty_sync(dir, false);
 
 	if (inode)
 		f2fs_drop_nlink(dir, inode);