Re: [PATCH] xfs: Start using pquotaino from the superblock.

Dave Chinner
2013-07-13T02:17:54Z

On Fri, Jul 12, 2013 at 03:32:27PM -0500, Chandra Seetharaman wrote:
> On Fri, 2013-07-12 at 13:30 -0500, Ben Myers wrote:
> > Hey Chandra,
> >
> <snip>
>
> > > @@ -591,6 +599,19 @@ xfs_sb_quota_from_disk(struct xfs_sb *sbp)
> > > sbp->sb_qflags |= (sbp->sb_qflags & XFS_PQUOTA_ACCT) ?
> > > XFS_PQUOTA_CHKD : XFS_GQUOTA_CHKD;
> > > sbp->sb_qflags &= ~(XFS_OQUOTA_ENFD | XFS_OQUOTA_CHKD);
> > > +
> > > + if ((sbp->sb_qflags & XFS_PQUOTA_ACCT) &&
> > > + (sbp->sb_gquotino != NULLFSINO)) {
> >
> > If project quota accounting bit is set in the super block
> > and
> > the group quot ino is not nullfsino..
> >
> > That's weird. I would have expected to be able to assume that sb_gquotino is
> > not NULLFSINO if project quota accounting is on. Why was the check necessary?
>
> Thinking now, I should not have added the second part.
> (sbp->sb_qflags & XFS_PQUOTA_ACCT) should be sufficient.
>
> >
> > > + /*
> > > + * On disk superblock only has sb_gquotino, and incore
> > > + * superblock has both sb_gquotino and sb_pquotino.
> > > + * But, only one of them is supported at any point of time.
> > > + * So, if PQUOTA is set in disk superblock, copy over
> > > + * sb_gquotino to sb_pquotino.
> > > + */
> > > + sbp->sb_pquotino = sbp->sb_gquotino;
> > > + sbp->sb_gquotino = NULLFSINO;
> > > + }
> > > }
> > >
> > > void
> > >
> <snip>
>
> > > diff --git a/fs/xfs/xfs_qm.c b/fs/xfs/xfs_qm.c
> > > index d320794..1e2361d 100644
> > > --- a/fs/xfs/xfs_qm.c
> > > +++ b/fs/xfs/xfs_qm.c
> > > @@ -834,6 +834,36 @@ xfs_qm_qino_alloc(
> > > int error;
> > > int committed;
> > >
> > > + *ip = NULL;
> > > + /*
> > > + * With superblock that doesn't have separate pquotino, we
> > > + * share an inode between gquota and pquota. If the on-disk
> > > + * superblock has GQUOTA and the filesystem is now mounted
> > > + * with PQUOTA, just use sb_gquotino for sb_pquotino and
> > > + * vice-versa.
> > > + */
> > > + if (!xfs_sb_version_has_pquotino(&mp->m_sb) &&
> > > + (flags & (XFS_QMOPT_PQUOTA|XFS_QMOPT_GQUOTA))) {
> > > + xfs_ino_t ino = NULLFSINO;
> > > +
> > > + if ((flags & XFS_QMOPT_PQUOTA) &&
> > > + (mp->m_sb.sb_gquotino != NULLFSINO)) {
> > > + ino = mp->m_sb.sb_gquotino;
> > > + ASSERT(mp->m_sb.sb_pquotino == NULLFSINO);
> > > + } else if ((flags & XFS_QMOPT_GQUOTA) &&
> > > + (mp->m_sb.sb_pquotino != NULLFSINO)) {
> > > + ino = mp->m_sb.sb_pquotino;
> > > + ASSERT(mp->m_sb.sb_gquotino == NULLFSINO);
> > > + }
> > > + if (ino != NULLFSINO) {
> > > + error = xfs_iget(mp, NULL, ino, 0, 0, ip);
> > > + if (error)
> > > + return error;
> > > + mp->m_sb.sb_gquotino = NULLFSINO;
> > > + mp->m_sb.sb_pquotino = NULLFSINO;
> > > + }
> > > + }
> >
> > Looks like this is a new addition. I'm not completely clear on why you
> > needed to add it. Maybe if the user had switched from using project
> > quotas to group quotas there would be an old inode left out there from
> > the project quotas? Is that why you added this? If so, wouldn't you
>
> Yes. that is correct.
> > want to truncate the old contents away before using it?
>
> Yikes, now I realize it is needed. Was just maintaining the earlier
> behavior (reuse the inode and nothing more), and did not realize
> truncate was missing.

It's not needed - the current code doesn't do a truncation when
switching from group to project and vice versa. quotacheck already
handles it - it zeros the existing dquots in the quota file first
before recalculating everything, so there is no problems with
"stale" contents being used whent eh swap occurs.

Cheers,

Dave.
--
Dave Chinner
david@fromorbit.com