On Mon, Jan 25, 2010 at 04:15:03PM -0700, Andreas Dilger wrote:
> We have had something similar for Lustre patched into ext3/ext4 for a
> long time -"__iopen__/{inum}", which depends on a mount option "iopen"
> to allow this functionality, and "iopen_nopriv" to allow access to non-
> root users.
>
> The problem we had in the past is that this needed a bunch of changes in
> ext3/4 and the VFS in order to handle subtle races in the dcache. We're
> moving away from changing ext3/4 and changing the API to use export
> methods (i.e. ext4_get_dentry()) on each filesystem, which should
> simplify this a lot, though I'm not sure it will solve your scalability
> problem.
the get_dentry export operation is long gone. Take a look at
xfs_handle_to_dentry() and friends for a semi-sane (not the horribe
legacy ABI but the implementation) open by handle implementation using
the full exportfs infrastructure. It's still going to hit the dcache
locking quite hard, though.
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