On Thu, 20 Jan 2011 13:38:18 +0800 Shaohua Li [off-list ref] wrote:

quoted

ext2, minix and probably others create an address_space for each
directory.  Heaven knows what xfs does (for example).

yes, this is for one directiory, but the all files's metadata are in
block_dev address_space.
I thought you mean there are several block_dev address_space like
address_space in some filesystems, which doesn't fit well in my
implementation. for ext like filesystem, there is only one
address_space. for filesystems with several address_space, my proposal
is map them to a virtual big address_space in the new ioctls.

ext2 and minixfs (and I think sysv and ufs) have a separate
address_space for each directory.  I don't see how those can be
represented with a single "virtual big address_space" - we also need
identifiers in there so each directory's address_space can be created
and appropriately populated.