xfs: create new metadata UUID field and incompat flag
This adds a new superblock field, sb_meta_uuid. If set, along with
a new incompat flag, the code will use that field on a V5 filesystem
to compare to metadata UUIDs, which allows us to change the user-
visible UUID at will. Userspace handles the setting and clearing
of the incompat flag as appropriate, as the UUID gets changed; i.e.
setting the user-visible UUID back to the original UUID (as stored in
the new field) will remove the incompatible feature flag.
If the incompat flag is not set, this copies the user-visible UUID into
into the meta_uuid slot in memory when the superblock is read from disk;
the meta_uuid field is not written back to disk in this case.
The remainder of this patch simply switches verifiers, initializers,
etc to use the new sb_meta_uuid field.
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c
index f9e9ffe..b7fc17c 100644
--- a/fs/xfs/libxfs/xfs_alloc.c
+++ b/fs/xfs/libxfs/xfs_alloc.c
@@ -464,7 +464,7 @@
struct xfs_agfl *agfl = XFS_BUF_TO_AGFL(bp);
int i;
- if (!uuid_equal(&agfl->agfl_uuid, &mp->m_sb.sb_uuid))
+ if (!uuid_equal(&agfl->agfl_uuid, &mp->m_sb.sb_meta_uuid))
return false;
if (be32_to_cpu(agfl->agfl_magicnum) != XFS_AGFL_MAGIC)
return false;
@@ -2260,7 +2260,7 @@
struct xfs_agf *agf = XFS_BUF_TO_AGF(bp);
if (xfs_sb_version_hascrc(&mp->m_sb) &&
- !uuid_equal(&agf->agf_uuid, &mp->m_sb.sb_uuid))
+ !uuid_equal(&agf->agf_uuid, &mp->m_sb.sb_meta_uuid))
return false;
if (!(agf->agf_magicnum == cpu_to_be32(XFS_AGF_MAGIC) &&