On Fri, Jul 25, 2014 at 08:46:28AM +1000, Dave Chinner wrote:
> On Thu, Jul 24, 2014 at 10:23:00AM -0400, Brian Foster wrote:
> > The sparse chunk inode record format is backwards compatible with old
> > format inobt records as long as full chunks are allocated. The holemask
> > field uses higher order bytes of the freecount. While sparse chunks can
> > be enabled on previously unsupported fs, older kernel drivers cannot
> > parse sparse inode records.
> >
> > Set the feature incompatible bit once a sparse inode chunk is allocated
> > to prevent older XFS drivers from tripping over the new format.
> >
> > Signed-off-by: Brian Foster <bfoster@xxxxxxxxxx>
> > ---
> > fs/xfs/libxfs/xfs_ialloc.c | 33 +++++++++++++++++++++++++++++++++
> > 1 file changed, 33 insertions(+)
> >
> > diff --git a/fs/xfs/libxfs/xfs_ialloc.c b/fs/xfs/libxfs/xfs_ialloc.c
> > index 4226b1b..4dd45c2 100644
> > --- a/fs/xfs/libxfs/xfs_ialloc.c
> > +++ b/fs/xfs/libxfs/xfs_ialloc.c
> > @@ -407,6 +407,27 @@ error:
> > return error;
> > }
> >
> > +STATIC void
> > +xfs_sbversion_add_spinodes(
> > + struct xfs_trans *tp,
> > + struct xfs_mount *mp)
> > +{
> > + if (xfs_sb_has_incompat_log_feature(&mp->m_sb,
> > + XFS_SB_FEAT_INCOMPAT_SPINODES))
>
> wrong function. xfs_sb_has_incompat_feature().
>
Oops, right.
> > + return;
> > +
> > + spin_lock(&mp->m_sb_lock);
> > + if (xfs_sb_has_incompat_log_feature(&mp->m_sb,
> > + XFS_SB_FEAT_INCOMPAT_SPINODES)) {
> > + spin_unlock(&mp->m_sb_lock);
> > + return;
> > + }
> > +
> > + mp->m_sb.sb_features_incompat |= XFS_SB_FEAT_INCOMPAT_SPINODES;
> > + spin_unlock(&mp->m_sb_lock);
> > + xfs_mod_sb(tp, XFS_SB_FEATURES_INCOMPAT);
> > +}
> > +
> > /*
> > * Allocate new inodes in the allocation group specified by agbp.
> > * Return 0 for success, else error code.
> > @@ -631,6 +652,18 @@ xfs_ialloc_ag_alloc(
> > if (error)
> > return error;
> > }
> > +
> > + /*
> > + * Set an incompat feature bit as old drivers can't parse sparse
> > + * records. Pre-sparse inode chunk drivers will include the
> > + * holemask in the higher order freecount bits, resulting in a
> > + * bogus value.
> > + *
> > + * XXX: when is this bit removed?
> > + */
> > + if (xfs_inobt_issparse(&rec))
> > + xfs_sbversion_add_spinodes(tp, args.mp);
>
> I'd like to avoid this dynamic feature bit adding if possible. Do we
> really need it?
>
Nope. As discussed, I'll move to something purely manual for the next
iteration and we can move forward from there with regard to if/when to
set it by default.
Brian
> Cheers,
>
> Dave.
> --
> Dave Chinner
> david@xxxxxxxxxxxxx
>
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