Re: [PATCH 1/3] xfs: fix quota accounting when a mount is idmapped

From: Christian Brauner <christian.brauner@ubuntu.com>
To: "Darrick J. Wong" <djwong@kernel.org>
Cc: linux-xfs@vger.kernel.org, hch@lst.de, dchinner@redhat.com
Subject: Re: [PATCH 1/3] xfs: fix quota accounting when a mount is idmapped
Date: Wed, 3 Mar 2021 19:09:57 +0000	[thread overview]
Message-ID: <20210303190957.7kabt57lvc432j6x@wittgenstein> (raw)
In-Reply-To: <20210303183352.GT7269@magnolia>

On Wed, Mar 03, 2021 at 10:33:52AM -0800, Darrick J. Wong wrote:
> On Wed, Mar 03, 2021 at 02:44:01PM +0000, Christian Brauner wrote:
> > On Tue, Mar 02, 2021 at 02:28:22PM -0800, Darrick J. Wong wrote:
> > > From: Darrick J. Wong <djwong@kernel.org>
> > > 
> > > Nowadays, we indirectly use the idmap-aware helper functions in the VFS
> > > to set the initial uid and gid of a file being created.  Unfortunately,
> > > we didn't convert the quota code, which means we attach the wrong dquots
> > > to files created on an idmapped mount.
> > > 
> > > Fixes: f736d93d76d3 ("xfs: support idmapped mounts")
> > > Signed-off-by: Darrick J. Wong <djwong@kernel.org>
> > > ---
> > 
> > This looks good but it misses one change, I think. The
> > xfs_ioctl_setattr() needs to take the mapping into account as well:
> > 
> > diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
> > index 99dfe89a8d08..067366bf9a59 100644
> > --- a/fs/xfs/xfs_ioctl.c
> > +++ b/fs/xfs/xfs_ioctl.c
> > @@ -1460,8 +1460,8 @@ xfs_ioctl_setattr(
> >          * because the i_*dquot fields will get updated anyway.
> >          */
> >         if (XFS_IS_QUOTA_ON(mp)) {
> > -               error = xfs_qm_vop_dqalloc(ip, VFS_I(ip)->i_uid,
> > -                               VFS_I(ip)->i_gid, fa->fsx_projid,
> > +               error = xfs_qm_vop_dqalloc(ip, i_uid_into_mnt(mnt_userns, VFS_I(ip)),
> > +                               i_gid_into_mnt(mnt_userns, VFS_I(ip)), fa->fsx_projid,
> >                                 XFS_QMOPT_PQUOTA, NULL, NULL, &pdqp);
> 
> The uid/gid parameters here don't matter because the "XFS_QMOPT_PQUOTA"
> flag by itself here means that _dqalloc only looks at the project id
> argument.

Ah, thanks! (Maybe a comment would be good or just idmaped them anyway.)

Thanks!
Christian