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;
        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) &&
 
        case cpu_to_be32(XFS_ABTB_CRC_MAGIC):
                if (!xfs_sb_version_hascrc(&mp->m_sb))
                        return false;
-               if (!uuid_equal(&block->bb_u.s.bb_uuid, &mp->m_sb.sb_uuid))
+               if (!uuid_equal(&block->bb_u.s.bb_uuid, &mp->m_sb.sb_meta_uuid))
                        return false;
                if (block->bb_u.s.bb_blkno != cpu_to_be64(bp->b_bn))
                        return false;
        case cpu_to_be32(XFS_ABTC_CRC_MAGIC):
                if (!xfs_sb_version_hascrc(&mp->m_sb))
                        return false;
-               if (!uuid_equal(&block->bb_u.s.bb_uuid, &mp->m_sb.sb_uuid))
+               if (!uuid_equal(&block->bb_u.s.bb_uuid, &mp->m_sb.sb_meta_uuid))
                        return false;
                if (block->bb_u.s.bb_blkno != cpu_to_be64(bp->b_bn))
                        return false;
 
                if (ichdr.magic != XFS_ATTR3_LEAF_MAGIC)
                        return false;
 
-               if (!uuid_equal(&hdr3->info.uuid, &mp->m_sb.sb_uuid))
+               if (!uuid_equal(&hdr3->info.uuid, &mp->m_sb.sb_meta_uuid))
                        return false;
                if (be64_to_cpu(hdr3->info.blkno) != bp->b_bn)
                        return false;
 
                hdr3->blkno = cpu_to_be64(bp->b_bn);
                hdr3->owner = cpu_to_be64(dp->i_ino);
-               uuid_copy(&hdr3->uuid, &mp->m_sb.sb_uuid);
+               uuid_copy(&hdr3->uuid, &mp->m_sb.sb_meta_uuid);
 
                ichdr.freemap[0].base = sizeof(struct xfs_attr3_leaf_hdr);
        } else {
 
                return false;
        if (rmt->rm_magic != cpu_to_be32(XFS_ATTR3_RMT_MAGIC))
                return false;
-       if (!uuid_equal(&rmt->rm_uuid, &mp->m_sb.sb_uuid))
+       if (!uuid_equal(&rmt->rm_uuid, &mp->m_sb.sb_meta_uuid))
                return false;
        if (be64_to_cpu(rmt->rm_blkno) != bno)
                return false;
        rmt->rm_magic = cpu_to_be32(XFS_ATTR3_RMT_MAGIC);
        rmt->rm_offset = cpu_to_be32(offset);
        rmt->rm_bytes = cpu_to_be32(size);
-       uuid_copy(&rmt->rm_uuid, &mp->m_sb.sb_uuid);
+       uuid_copy(&rmt->rm_uuid, &mp->m_sb.sb_meta_uuid);
        rmt->rm_owner = cpu_to_be64(ino);
        rmt->rm_blkno = cpu_to_be64(bno);
 
 
 
        if (xfs_sb_version_hascrc(&mp->m_sb)) {
                ASSERT(rblock->bb_magic == cpu_to_be32(XFS_BMAP_CRC_MAGIC));
-               ASSERT(uuid_equal(&rblock->bb_u.l.bb_uuid, &mp->m_sb.sb_uuid));
+               ASSERT(uuid_equal(&rblock->bb_u.l.bb_uuid,
+                      &mp->m_sb.sb_meta_uuid));
                ASSERT(rblock->bb_u.l.bb_blkno ==
                       cpu_to_be64(XFS_BUF_DADDR_NULL));
        } else
        case cpu_to_be32(XFS_BMAP_CRC_MAGIC):
                if (!xfs_sb_version_hascrc(&mp->m_sb))
                        return false;
-               if (!uuid_equal(&block->bb_u.l.bb_uuid, &mp->m_sb.sb_uuid))
+               if (!uuid_equal(&block->bb_u.l.bb_uuid, &mp->m_sb.sb_meta_uuid))
                        return false;
                if (be64_to_cpu(block->bb_u.l.bb_blkno) != bp->b_bn)
                        return false;
 
 
        if (xfs_sb_version_hascrc(&mp->m_sb)) {
                lblock_ok = lblock_ok &&
-                       uuid_equal(&block->bb_u.l.bb_uuid, &mp->m_sb.sb_uuid) &&
+                       uuid_equal(&block->bb_u.l.bb_uuid,
+                                  &mp->m_sb.sb_meta_uuid) &&
                        block->bb_u.l.bb_blkno == cpu_to_be64(
                                bp ? bp->b_bn : XFS_BUF_DADDR_NULL);
        }
 
        if (xfs_sb_version_hascrc(&mp->m_sb)) {
                sblock_ok = sblock_ok &&
-                       uuid_equal(&block->bb_u.s.bb_uuid, &mp->m_sb.sb_uuid) &&
+                       uuid_equal(&block->bb_u.s.bb_uuid,
+                                  &mp->m_sb.sb_meta_uuid) &&
                        block->bb_u.s.bb_blkno == cpu_to_be64(
                                bp ? bp->b_bn : XFS_BUF_DADDR_NULL);
        }
                if (flags & XFS_BTREE_CRC_BLOCKS) {
                        buf->bb_u.l.bb_blkno = cpu_to_be64(blkno);
                        buf->bb_u.l.bb_owner = cpu_to_be64(owner);
-                       uuid_copy(&buf->bb_u.l.bb_uuid, &mp->m_sb.sb_uuid);
+                       uuid_copy(&buf->bb_u.l.bb_uuid, &mp->m_sb.sb_meta_uuid);
                        buf->bb_u.l.bb_pad = 0;
                        buf->bb_u.l.bb_lsn = 0;
                }
                if (flags & XFS_BTREE_CRC_BLOCKS) {
                        buf->bb_u.s.bb_blkno = cpu_to_be64(blkno);
                        buf->bb_u.s.bb_owner = cpu_to_be32(__owner);
-                       uuid_copy(&buf->bb_u.s.bb_uuid, &mp->m_sb.sb_uuid);
+                       uuid_copy(&buf->bb_u.s.bb_uuid, &mp->m_sb.sb_meta_uuid);
                        buf->bb_u.s.bb_lsn = 0;
                }
        }
 
                if (ichdr.magic != XFS_DA3_NODE_MAGIC)
                        return false;
 
-               if (!uuid_equal(&hdr3->info.uuid, &mp->m_sb.sb_uuid))
+               if (!uuid_equal(&hdr3->info.uuid, &mp->m_sb.sb_meta_uuid))
                        return false;
                if (be64_to_cpu(hdr3->info.blkno) != bp->b_bn)
                        return false;
                ichdr.magic = XFS_DA3_NODE_MAGIC;
                hdr3->info.blkno = cpu_to_be64(bp->b_bn);
                hdr3->info.owner = cpu_to_be64(args->dp->i_ino);
-               uuid_copy(&hdr3->info.uuid, &mp->m_sb.sb_uuid);
+               uuid_copy(&hdr3->info.uuid, &mp->m_sb.sb_meta_uuid);
        } else {
                ichdr.magic = XFS_DA_NODE_MAGIC;
        }
 
        if (xfs_sb_version_hascrc(&mp->m_sb)) {
                if (hdr3->magic != cpu_to_be32(XFS_DIR3_BLOCK_MAGIC))
                        return false;
-               if (!uuid_equal(&hdr3->uuid, &mp->m_sb.sb_uuid))
+               if (!uuid_equal(&hdr3->uuid, &mp->m_sb.sb_meta_uuid))
                        return false;
                if (be64_to_cpu(hdr3->blkno) != bp->b_bn)
                        return false;
                hdr3->magic = cpu_to_be32(XFS_DIR3_BLOCK_MAGIC);
                hdr3->blkno = cpu_to_be64(bp->b_bn);
                hdr3->owner = cpu_to_be64(dp->i_ino);
-               uuid_copy(&hdr3->uuid, &mp->m_sb.sb_uuid);
+               uuid_copy(&hdr3->uuid, &mp->m_sb.sb_meta_uuid);
                return;
 
        }
 
        if (xfs_sb_version_hascrc(&mp->m_sb)) {
                if (hdr3->magic != cpu_to_be32(XFS_DIR3_DATA_MAGIC))
                        return false;
-               if (!uuid_equal(&hdr3->uuid, &mp->m_sb.sb_uuid))
+               if (!uuid_equal(&hdr3->uuid, &mp->m_sb.sb_meta_uuid))
                        return false;
                if (be64_to_cpu(hdr3->blkno) != bp->b_bn)
                        return false;
                hdr3->magic = cpu_to_be32(XFS_DIR3_DATA_MAGIC);
                hdr3->blkno = cpu_to_be64(bp->b_bn);
                hdr3->owner = cpu_to_be64(dp->i_ino);
-               uuid_copy(&hdr3->uuid, &mp->m_sb.sb_uuid);
+               uuid_copy(&hdr3->uuid, &mp->m_sb.sb_meta_uuid);
 
        } else
                hdr->magic = cpu_to_be32(XFS_DIR2_DATA_MAGIC);
 
 
                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;
                                         : 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);
 
 
                if (hdr3->magic != cpu_to_be32(XFS_DIR3_FREE_MAGIC))
                        return false;
-               if (!uuid_equal(&hdr3->uuid, &mp->m_sb.sb_uuid))
+               if (!uuid_equal(&hdr3->uuid, &mp->m_sb.sb_meta_uuid))
                        return false;
                if (be64_to_cpu(hdr3->blkno) != bp->b_bn)
                        return false;
 
                hdr3->hdr.blkno = cpu_to_be64(bp->b_bn);
                hdr3->hdr.owner = cpu_to_be64(dp->i_ino);
-               uuid_copy(&hdr3->hdr.uuid, &mp->m_sb.sb_uuid);
+               uuid_copy(&hdr3->hdr.uuid, &mp->m_sb.sb_meta_uuid);
        } else
                hdr.magic = XFS_DIR2_FREE_MAGIC;
        dp->d_ops->free_hdr_to_disk(bp->b_addr, &hdr);
 
        d->dd_diskdq.d_id = cpu_to_be32(id);
 
        if (xfs_sb_version_hascrc(&mp->m_sb)) {
-               uuid_copy(&d->dd_uuid, &mp->m_sb.sb_uuid);
+               uuid_copy(&d->dd_uuid, &mp->m_sb.sb_meta_uuid);
                xfs_update_cksum((char *)d, sizeof(struct xfs_dqblk),
                                 XFS_DQUOT_CRC_OFF);
        }
                if (!xfs_verify_cksum((char *)d, sizeof(struct xfs_dqblk),
                                 XFS_DQUOT_CRC_OFF))
                        return false;
-               if (!uuid_equal(&d->dd_uuid, &mp->m_sb.sb_uuid))
+               if (!uuid_equal(&d->dd_uuid, &mp->m_sb.sb_meta_uuid))
                        return false;
        }
        return true;
 
        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 */
 
        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;
        __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 */
 
        __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;
 
 #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
                xfs_sb_has_incompat_feature(sbp, XFS_SB_FEAT_INCOMPAT_SPINODES);
 }
 
+/*
+ * 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
  */
 
                        if (version == 3) {
                                free->di_ino = cpu_to_be64(ino);
                                ino++;
-                               uuid_copy(&free->di_uuid, &mp->m_sb.sb_uuid);
+                               uuid_copy(&free->di_uuid,
+                                         &mp->m_sb.sb_meta_uuid);
                                xfs_dinode_calc_crc(mp, free);
                        } else if (tp) {
                                /* just log the inode core */
        struct xfs_agi  *agi = XFS_BUF_TO_AGI(bp);
 
        if (xfs_sb_version_hascrc(&mp->m_sb) &&
-           !uuid_equal(&agi->agi_uuid, &mp->m_sb.sb_uuid))
+           !uuid_equal(&agi->agi_uuid, &mp->m_sb.sb_meta_uuid))
                        return false;
        /*
         * Validate the magic number of the agi block.
 
        case cpu_to_be32(XFS_FIBT_CRC_MAGIC):
                if (!xfs_sb_version_hascrc(&mp->m_sb))
                        return false;
-               if (!uuid_equal(&block->bb_u.s.bb_uuid, &mp->m_sb.sb_uuid))
+               if (!uuid_equal(&block->bb_u.s.bb_uuid, &mp->m_sb.sb_meta_uuid))
                        return false;
                if (block->bb_u.s.bb_blkno != cpu_to_be64(bp->b_bn))
                        return false;
 
                return false;
        if (be64_to_cpu(dip->di_ino) != ip->i_ino)
                return false;
-       if (!uuid_equal(&dip->di_uuid, &mp->m_sb.sb_uuid))
+       if (!uuid_equal(&dip->di_uuid, &mp->m_sb.sb_meta_uuid))
                return false;
        return true;
 }
                if (xfs_sb_version_hascrc(&mp->m_sb)) {
                        ip->i_d.di_version = 3;
                        ip->i_d.di_ino = ip->i_ino;
-                       uuid_copy(&ip->i_d.di_uuid, &mp->m_sb.sb_uuid);
+                       uuid_copy(&ip->i_d.di_uuid, &mp->m_sb.sb_meta_uuid);
                } else
                        ip->i_d.di_version = 2;
                return 0;
 
        to->sb_spino_align = be32_to_cpu(from->sb_spino_align);
        to->sb_pquotino = be64_to_cpu(from->sb_pquotino);
        to->sb_lsn = be64_to_cpu(from->sb_lsn);
+       /*
+        * sb_meta_uuid is only on disk if it differs from sb_uuid and the
+        * feature flag is set; if not set we keep it only in memory.
+        */
+       if (xfs_sb_version_hasmetauuid(to))
+               uuid_copy(&to->sb_meta_uuid, &from->sb_meta_uuid);
+       else
+               uuid_copy(&to->sb_meta_uuid, &from->sb_uuid);
        /* Convert on-disk flags to in-memory flags? */
        if (convert_xquota)
                xfs_sb_quota_from_disk(to);
                                cpu_to_be32(from->sb_features_log_incompat);
                to->sb_spino_align = cpu_to_be32(from->sb_spino_align);
                to->sb_lsn = cpu_to_be64(from->sb_lsn);
+               if (xfs_sb_version_hasmetauuid(from))
+                       uuid_copy(&to->sb_meta_uuid, &from->sb_meta_uuid);
        }
 }
 
 
        dsl->sl_magic = cpu_to_be32(XFS_SYMLINK_MAGIC);
        dsl->sl_offset = cpu_to_be32(offset);
        dsl->sl_bytes = cpu_to_be32(size);
-       uuid_copy(&dsl->sl_uuid, &mp->m_sb.sb_uuid);
+       uuid_copy(&dsl->sl_uuid, &mp->m_sb.sb_meta_uuid);
        dsl->sl_owner = cpu_to_be64(ino);
        dsl->sl_blkno = cpu_to_be64(bp->b_bn);
        bp->b_ops = &xfs_symlink_buf_ops;
                return false;
        if (dsl->sl_magic != cpu_to_be32(XFS_SYMLINK_MAGIC))
                return false;
-       if (!uuid_equal(&dsl->sl_uuid, &mp->m_sb.sb_uuid))
+       if (!uuid_equal(&dsl->sl_uuid, &mp->m_sb.sb_meta_uuid))
                return false;
        if (bp->b_bn != be64_to_cpu(dsl->sl_blkno))
                return false;