[PATCH] Btrfs: zero unused bytes in inode item

[Li Zefan <lizefan@huawei.com>]

The otime field is not zeroed, so users will see random otime in an old
filesystem with a new kernel which has otime support in the future.

The reserved bytes are also not zeroed, and we'll have compatibility
issue if we make use of those bytes.

Signed-off-by: Li Zefan <lizefan@huawei.com>
---
 fs/btrfs/delayed-inode.c |    1 +
 fs/btrfs/inode.c         |    2 ++
 2 files changed, 3 insertions(+)

diff --git a/fs/btrfs/delayed-inode.c b/fs/btrfs/delayed-inode.c
index 21d91a8..335605c 100644
--- a/fs/btrfs/delayed-inode.c
+++ b/fs/btrfs/delayed-inode.c
@@ -62,6 +62,7 @@ static inline void btrfs_init_delayed_node(
 	INIT_LIST_HEAD(&delayed_node->n_list);
 	INIT_LIST_HEAD(&delayed_node->p_list);
 	delayed_node->bytes_reserved = 0;
+	memset(&delayed_node->inode_item, 0, sizeof(delayed_node->inode_item));
 }
 
 static inline int btrfs_is_continuous_delayed_item(
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index b189dd8..3a612f8 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -4688,6 +4688,8 @@ static struct inode *btrfs_new_inode(struct btrfs_trans_handle *trans,
 	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
 	inode_item = btrfs_item_ptr(path->nodes[0], path->slots[0],
 				  struct btrfs_inode_item);
+	memset_extent_buffer(path->nodes[0], 0, (unsigned long)inode_item,
+			     sizeof(*inode_item));
 	fill_inode_item(trans, path->nodes[0], inode_item, inode);
 
 	ref = btrfs_item_ptr(path->nodes[0], path->slots[0] + 1,
-- 
1.7.9.7