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- .. SPDX-License-Identifier: GPL-2.0
- Large Extended Attribute Values
- -------------------------------
- To enable ext4 to store extended attribute values that do not fit in the
- inode or in the single extended attribute block attached to an inode,
- the EA\_INODE feature allows us to store the value in the data blocks of
- a regular file inode. This “EA inode” is linked only from the extended
- attribute name index and must not appear in a directory entry. The
- inode's i\_atime field is used to store a checksum of the xattr value;
- and i\_ctime/i\_version store a 64-bit reference count, which enables
- sharing of large xattr values between multiple owning inodes. For
- backward compatibility with older versions of this feature, the
- i\_mtime/i\_generation *may* store a back-reference to the inode number
- and i\_generation of the **one** owning inode (in cases where the EA
- inode is not referenced by multiple inodes) to verify that the EA inode
- is the correct one being accessed.
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