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