Al Viro <viro@xxxxxxxxxxxxxxxxxx> writes: > On Tue, Feb 16, 2010 at 01:52:43PM +0300, Dmitry Monakhov wrote: >> Initially i've posted RFC patch-set which add subtree support for ext4. >> http://marc.info/?l=linux-ext4&m=126563931215496&w=2 >> But in fact this is rather generic feature which may be implemented >> in vfs layer similar to namespace or security feature. >> >> 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 assumptions: >> * Each inode has subtree id (this id is stored inside inode). >> * Subtree id is inherent from parent directory if corresponding flag is set >> * Inode can not belongs to different subtrees >> >> i've ommit subtree_type feature in order to simplify brief explanation. >> >> Subtree with id == 0 has special meaning. It may contains roots of >> other subtrees (this feature is used for cross subtree renames) >> This feature has much in common with XFS project_id. > > Um. Just how is it different from having normal subtrees mounted separately? > And what's the ID for? For example for quota needs. With subtree support we can account some subtree in to corresponding quota_subtree id. > > We already can mount arbitrary subtrees of directory tree from given fs, > as many times as we want and in as many places as we like. With each > mountpoint acting as barrier to link() and rename(). -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
