f2fs: fix lost xattrs of directories

This patch enhances the xattr consistency of dirs from suddern power-cuts.

Possible scenario would be:
1. dir->setxattr used by per-file encryption
2. file->setxattr goes into inline_xattr
3. file->fsync

In that case, we should do checkpoint for #1.
Otherwise we'd lose dir's key information for the file given #2.

Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/checkpoint.c

@@ -1152,6 +1152,7 @@ static int do_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc)
 
 	clear_prefree_segments(sbi, cpc);
 	clear_sbi_flag(sbi, SBI_IS_DIRTY);
+	clear_sbi_flag(sbi, SBI_NEED_CP);
 
 	return 0;
 }