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_dir2_leaf.c b/fs/xfs/libxfs/xfs_dir2_leaf.c
index 1061199..f300240 100644
--- a/fs/xfs/libxfs/xfs_dir2_leaf.c
+++ b/fs/xfs/libxfs/xfs_dir2_leaf.c
@@ -160,7 +160,7 @@
if (leaf3->info.hdr.magic != cpu_to_be16(magic3))
return false;
- if (!uuid_equal(&leaf3->info.uuid, &mp->m_sb.sb_uuid))
+ if (!uuid_equal(&leaf3->info.uuid, &mp->m_sb.sb_meta_uuid))
return false;
if (be64_to_cpu(leaf3->info.blkno) != bp->b_bn)
return false;
@@ -310,7 +310,7 @@
: cpu_to_be16(XFS_DIR3_LEAFN_MAGIC);
leaf3->info.blkno = cpu_to_be64(bp->b_bn);
leaf3->info.owner = cpu_to_be64(owner);
- uuid_copy(&leaf3->info.uuid, &mp->m_sb.sb_uuid);
+ uuid_copy(&leaf3->info.uuid, &mp->m_sb.sb_meta_uuid);
} else {
memset(leaf, 0, sizeof(*leaf));
leaf->hdr.info.magic = cpu_to_be16(type);
