| .. 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. |
