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_format.h b/fs/xfs/libxfs/xfs_format.h
index a0ae572..9590a06 100644
--- a/fs/xfs/libxfs/xfs_format.h
+++ b/fs/xfs/libxfs/xfs_format.h
@@ -100,7 +100,7 @@
xfs_rfsblock_t sb_dblocks; /* number of data blocks */
xfs_rfsblock_t sb_rblocks; /* number of realtime blocks */
xfs_rtblock_t sb_rextents; /* number of realtime extents */
- uuid_t sb_uuid; /* file system unique id */
+ uuid_t sb_uuid; /* user-visible file system unique id */
xfs_fsblock_t sb_logstart; /* starting block of log if internal */
xfs_ino_t sb_rootino; /* root inode number */
xfs_ino_t sb_rbmino; /* bitmap inode for realtime extents */
@@ -174,6 +174,7 @@
xfs_ino_t sb_pquotino; /* project quota inode */
xfs_lsn_t sb_lsn; /* last write sequence */
+ uuid_t sb_meta_uuid; /* metadata file system unique id */
/* must be padded to 64 bit alignment */
} xfs_sb_t;
@@ -190,7 +191,7 @@
__be64 sb_dblocks; /* number of data blocks */
__be64 sb_rblocks; /* number of realtime blocks */
__be64 sb_rextents; /* number of realtime extents */
- uuid_t sb_uuid; /* file system unique id */
+ uuid_t sb_uuid; /* user-visible file system unique id */
__be64 sb_logstart; /* starting block of log if internal */
__be64 sb_rootino; /* root inode number */
__be64 sb_rbmino; /* bitmap inode for realtime extents */
@@ -260,6 +261,7 @@
__be64 sb_pquotino; /* project quota inode */
__be64 sb_lsn; /* last write sequence */
+ uuid_t sb_meta_uuid; /* metadata file system unique id */
/* must be padded to 64 bit alignment */
} xfs_dsb_t;
@@ -458,9 +460,11 @@
#define XFS_SB_FEAT_INCOMPAT_FTYPE (1 << 0) /* filetype in dirent */
#define XFS_SB_FEAT_INCOMPAT_SPINODES (1 << 1) /* sparse inode chunks */
+#define XFS_SB_FEAT_INCOMPAT_META_UUID (1 << 2) /* metadata UUID */
#define XFS_SB_FEAT_INCOMPAT_ALL \
(XFS_SB_FEAT_INCOMPAT_FTYPE| \
- XFS_SB_FEAT_INCOMPAT_SPINODES)
+ XFS_SB_FEAT_INCOMPAT_SPINODES| \
+ XFS_SB_FEAT_INCOMPAT_META_UUID)
#define XFS_SB_FEAT_INCOMPAT_UNKNOWN ~XFS_SB_FEAT_INCOMPAT_ALL
static inline bool
@@ -515,6 +519,18 @@
}
/*
+ * XFS_SB_FEAT_INCOMPAT_META_UUID indicates that the metadata UUID
+ * is stored separately from the user-visible UUID; this allows the
+ * user-visible UUID to be changed on V5 filesystems which have a
+ * filesystem UUID stamped into every piece of metadata.
+ */
+static inline bool xfs_sb_version_hasmetauuid(struct xfs_sb *sbp)
+{
+ return (XFS_SB_VERSION_NUM(sbp) == XFS_SB_VERSION_5) &&
+ (sbp->sb_features_incompat & XFS_SB_FEAT_INCOMPAT_META_UUID);
+}
+
+/*
* end of superblock version macros
*/