On 2010-02-08, at 06:28, Dmitry Monakhov wrote:
A subtree of a directory tree T is a tree consisting of a directory
(the subtree root) in T and all of its descendants in T.
Subtree feature allows to create an isolated (from user point of
view)
trees.
Subtree assumptions:
(1) Each inode has subtree id. This id is persistently stored inside
inode (xattr, usually inside ibody)
(2) Subtree id is inherent from parent directory
(3) Inode can not belongs to different subtree
Otherwise changes in one subtree result in changes in other
subtree
which contradict to isolation criteria.
This feature is similar to project-id in XFS. One may assign some
id to
a subtree. Each entry from the subtree may be accounted in directory
subtree quota. Will appear in later patches.
* Disk layout
Subtree id is stored on disk inside xattr usually inside ibody.
Xattr is used only as a data storage, It has not user visiable xattr
interface.
Presumably this would need e2fsck support, in order to ensure that
inodes in a given directory have the same subtree ID as the parent
directory.
Also, how are the subtree IDs generated, to ensure that they are
unique between subtrees?
Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.
--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
