On 2024-03-14 19:48:26, Darrick J. Wong wrote:
> On Thu, Mar 14, 2024 at 06:07:02PM +0100, Andrey Albershteyn wrote:
> > There's an issue that if special files is created before quota
> > project is enabled, then it's not possible to link this file. This
> > works fine for normal files. This happens because xfs_quota skips
> > special files (no ioctls to set necessary flags). The check for
> > having the same project ID for source and destination then fails as
> > source file doesn't have any ID.
> >
> > mkfs.xfs -f /dev/sda
> > mount -o prjquota /dev/sda /mnt/test
> >
> > mkdir /mnt/test/foo
> > mkfifo /mnt/test/foo/fifo1
> >
> > xfs_quota -xc "project -sp /mnt/test/foo 9" /mnt/test
> > > Setting up project 9 (path /mnt/test/foo)...
> > > xfs_quota: skipping special file /mnt/test/foo/fifo1
> > > Processed 1 (/etc/projects and cmdline) paths for project 9 with recursion depth infinite (-1).
> >
> > ln /mnt/test/foo/fifo1 /mnt/test/foo/fifo1_link
> > > ln: failed to create hard link '/mnt/test/testdir/fifo1_link' => '/mnt/test/testdir/fifo1': Invalid cross-device link
>
> Aha. So hardlinking special files within a directory subtree that all
> have the same nonzero project quota ID fails if that special file
> happened to have been created before the subtree was assigned that pqid.
> And there's nothing we can do about that, because there's no way to call
> XFS_IOC_SETFSXATTR on a special file because opening those gets you a
> different inode from the special block/fifo/chardev filesystem...
>
> > mkfifo /mnt/test/foo/fifo2
> > ln /mnt/test/foo/fifo2 /mnt/test/foo/fifo2_link
> >
> > Fix this by allowing linking of special files to the project quota
> > if special files doesn't have any ID set (ID = 0).
>
> ...and that's the workaround for this situation. The project quota
> accounting here will be weird because there will be (more) files in a
> directory subtree than is reported by xfs_quota, but the subtree was
> already messed up in that manner.
>
> Question: Should we have a XFS_IOC_SETFSXATTRAT where we can pass in
> relative directory paths and actually query/update special files?
After some more thinking/looking into the code this is probably the
only way to make it work the same for special files. Also, I've
noticed that this workaround can be applied to xfs_rename then.
So, I will start with implementing XFS_IOC_SETFSXATTRAT
--
- Andrey
> > Signed-off-by: Andrey Albershteyn <aalbersh@xxxxxxxxxx>
>
> Reviewed-by: Darrick J. Wong <djwong@xxxxxxxxxx>
>
> --D
>
> > ---
> > fs/xfs/xfs_inode.c | 15 +++++++++++++--
> > 1 file changed, 13 insertions(+), 2 deletions(-)
> >
> > diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
> > index 1fd94958aa97..b7be19be0132 100644
> > --- a/fs/xfs/xfs_inode.c
> > +++ b/fs/xfs/xfs_inode.c
> > @@ -1240,8 +1240,19 @@ xfs_link(
> > */
> > if (unlikely((tdp->i_diflags & XFS_DIFLAG_PROJINHERIT) &&
> > tdp->i_projid != sip->i_projid)) {
> > - error = -EXDEV;
> > - goto error_return;
> > + /*
> > + * Project quota setup skips special files which can
> > + * leave inodes in a PROJINHERIT directory without a
> > + * project ID set. We need to allow links to be made
> > + * to these "project-less" inodes because userspace
> > + * expects them to succeed after project ID setup,
> > + * but everything else should be rejected.
> > + */
> > + if (!special_file(VFS_I(sip)->i_mode) ||
> > + sip->i_projid != 0) {
> > + error = -EXDEV;
> > + goto error_return;
> > + }
> > }
> >
> > if (!resblks) {
> > --
> > 2.42.0
> >
> >
>
