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Re: [PATCH v5 08/10] xfs: add quota id filtering to eofblocks scan

To: Brian Foster <bfoster@xxxxxxxxxx>
Subject: Re: [PATCH v5 08/10] xfs: add quota id filtering to eofblocks scan
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Thu, 25 Oct 2012 06:41:24 +1100
Cc: xfs@xxxxxxxxxxx
In-reply-to: <508814F2.3060409@xxxxxxxxxx>
References: <1349446636-8611-1-git-send-email-bfoster@xxxxxxxxxx> <1349446636-8611-9-git-send-email-bfoster@xxxxxxxxxx> <20121023014222.GL4291@dastard> <508814F2.3060409@xxxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
On Wed, Oct 24, 2012 at 12:18:58PM -0400, Brian Foster wrote:
> On 10/22/2012 09:42 PM, Dave Chinner wrote:
> > On Fri, Oct 05, 2012 at 10:17:14AM -0400, Brian Foster wrote:
> >> Support quota ID filtering in the eofblocks scan. The caller must
> >> set the XFS_EOF_FLAGS_QUOTA flags bit, quota ID and quota type. The
> >> associated quota type must be enabled on the mounted filesystem.
> > 
> > I'm wondering if this even needs quota enabled to filter based on a
> > uid, gid, or prid?
> > 
> 
> Not really...
> 
> > The quota part of it seem irrelevant to the filtering that is being
> > executed - we are only matching against the inode uid/gid/prid, not
> > against dquots - and I can see situations where just being able to
> > filter on a given uid/gid might be useful in a multi-user
> > environment regardless of whether quotas are being used.
> > 
> 
> This is how my rfc version was implemented (with a comment to the same
> effect). I added the explicit checking in response to:
> 
> http://oss.sgi.com/archives/xfs/2012-09/msg00024.html

Ok, that was in the context of "we need to be specific about what
the ID is". Now the question is "is quota ID the right ID to use?".
Different question. ;)

> > Indeed, even testing is made much easier if we don't have to
> > juggle quota mount options to test the filtering....
> > 
> 
> I agree. I suppose the check can make a bit of sense if the current
> group/proj mode of the mount conflicts with the eofb request, but as
> you've outlined above, we're checking against the inode values so I
> don't think it introduces a functional problem.

Right, and if we even get the separate project quota inode patches
merged, then all three can be valid at once. Indeed, that makes me
ask the question - should we be able to filter on multiple IDs in a
single pass (e.g. walk Jim's files in the jasper project)?

Seeing as it is just a filter, enabling the above (even though it
would be rarely used) might make sense. i.e. separate field for each
id. It's not like we have to keep the size of the structure to a
minimum...

Cheers,

Dave.
> > Why do you need xfs_quota_type() here? why not just:
> > 
> >     switch (type) {
> >     case XQM_USRQUOTA:
> >             return ip->i_d.di_uid == eofb->eof_q_id;
> >     case XQM_GRPQUOTA:
> >             return ip->i_d.di_gid == eofb->eof_q_id;
> >     case XQM_PRJQUOTA:
> >             return xfs_get_projid(ip) == eofb->eof_q_id;
> >     default:
> >             break;
> >     }
> > 
> >     return 0;
> > 
> 
> Technically we don't really need xfs_quota_type(). I just thought it
> cleaner to use the same mapping we use throughout XFS (i.e., I don't see
> those definitions used elsewhere in XFS)...

XQM_* are the userspace XFS quota interface definitions. They are
what xfs_quota uses. They just so happen to be the same as the
generic quota definitions except the generic quotas don't define
project quota types (hence the need for mapping).  See
include/uapi/linux/dqblk_xfs.h.

I just figured that rather than mapping something unknown to
something known, just using something known in the first place is
much simpler...

Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx

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