Re: [PATCH 0/7 V3] quota: add new quotactl Q_GETNEXTQUOTA

Jan Kara
2016-01-25T15:07:05Z

On Fri 22-01-16 12:25:29, Eric Sandeen wrote:
> This adds a new quotactl, Q_GETNEXTQUOTA.
>
> Q_GETNEXTQUOTA is exactly like Q_GETQUOTA, except that it will
> return quota information for the id equal to or greater than
> the id requested. In other words, if the specified id has
> no quota, the command will return quota information for the
> next higher id which does have a quota set. If no higher id
> has an active quota, -ESRCH is returned.
>
> So if you ask for id X, you can get back quota for id X,
> id X+N, or -ESRCH if no higher id has a quota.
>
> This allows filesystems to do efficient iteration in kernelspace,
> much like extN filesystems do in userspace when asked to report
> all active quotas.
>
> Today, filesystems such as XFS require getpwent()-style iterations,
> and for systems which have i.e. LDAP backends, this can be very
> slow, or even impossible if iteration is not allowed in the
> configuration.
>
> Patches 1 and 4 are just small fixups that turned up along the way;
> 2 and 3 add the actual quota plumbing, and the rest are xfs-specific
> to allow xfs to support this new interface.
>
> For non-xfs quota, this does require a new structure which is
> able to pass back the discovered ID along with the quota info.
> For xfs-quota, the id is already present in the structure.
>
> V3:
> * Remove 32-bit compat stuff (i686/x86_64 at least works w/o it...)
> * Require CAP_SYS_ADMIN for these calls
> * Pass back found ID in &qid passed to ->get_nextdqblk, rather
> than modifying struct qc_dqblk
> * Munge that found ID back through user-namespace conversions
> before returning it in the user structure.

So I've taken patch 1/7 into my tree since that is completely independent.
Patches 2/7 and 3/7 look mostly good to me (except for that small omission
in 3/7) so I can take them to my tree as well. Once I'll finish testing
some UDF changes I have pending I'll push the tree to:

git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs.git for_next

and Dave can pull from there to have a basis for XFS patches. I want to
implement Q_GETNEXTQUOTA for VFS quota formats as well and those will go
through my tree so that's why I want the interface changes go via my tree.

Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR