eainode.rst 979 B

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