Re: [PATCH 01/28] ext4: xattr-in-inode support

[Tahsin Erdogan]

>> allowing the ext4/e2fsck to verify the correct inode is accessed.
>
> Can we store the checksum of the xattr value somewhere?  We already
> checksum the values if they're stored in the ibody or a single external
> block, and I'd hate to lose that protection.
>
> We could probably reuse one of the inode fields (i_version?) for this.
>
The crc32c value of the xattr data is currently stored in the xattr inode:

struct ext4_xattr_ea_info {
__le64 ref_count; /* number of xattr entry references */
__le32 hash; /* crc32c hash of xattr data */
__le32 reserved; /* reserved, must be 0 */
};

We could also save that value in the ext4_xattr_entry->e_value_offs
for stronger binding between parent and xattr inodes. That field is
currently set to 0 for xattr inode references.