1.. SPDX-License-Identifier: GPL-2.0
2
3Large Extended Attribute Values
4-------------------------------
5
6To enable ext4 to store extended attribute values that do not fit in the
7inode or in the single extended attribute block attached to an inode,
8the EA_INODE feature allows us to store the value in the data blocks of
9a regular file inode. This ���EA inode��� is linked only from the extended
10attribute name index and must not appear in a directory entry. The
11inode's i_atime field is used to store a checksum of the xattr value;
12and i_ctime/i_version store a 64-bit reference count, which enables
13sharing of large xattr values between multiple owning inodes. For
14backward compatibility with older versions of this feature, the
15i_mtime/i_generation *may* store a back-reference to the inode number
16and i_generation of the **one** owning inode (in cases where the EA
17inode is not referenced by multiple inodes) to verify that the EA inode
18is the correct one being accessed.
19