mirror of https://gitee.com/openkylin/linux.git
19 lines
979 B
ReStructuredText
19 lines
979 B
ReStructuredText
.. 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.
|