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Diffstat (limited to 'Documentation/filesystems/ext4/eainode.rst')
| -rw-r--r-- | Documentation/filesystems/ext4/eainode.rst | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/Documentation/filesystems/ext4/eainode.rst b/Documentation/filesystems/ext4/eainode.rst new file mode 100644 index 000000000000..ecc0d01a0a72 --- /dev/null +++ b/Documentation/filesystems/ext4/eainode.rst @@ -0,0 +1,18 @@ +.. 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. |