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* [PATCH 0/2] allow UUID changes on V5/CRC filesystems
@ 2015-05-08 20:40 Eric Sandeen
  2015-05-08 20:48 ` [PATCH 1/2] xfs: create new metadata UUID field and incompat flag Eric Sandeen
  2015-05-08 20:59 ` [PATCH 2/2] xfsprogs: Add new sb_meta_uuid field, and userspace tools to manipulate it Eric Sandeen
  0 siblings, 2 replies; 11+ messages in thread
From: Eric Sandeen @ 2015-05-08 20:40 UTC (permalink / raw)
  To: xfs-oss

Ok, here's the next round.  This has been through some degree of testing,
though I still probably owe some xfstests testcases.

Dave, in the end I went ahead and kept the sb_uuid name and meaning
in the same superblock location; this does mean we touch all verifiers
etc, but it makes for more consistency, IMHO.

Thanks,
-Eric

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^ permalink raw reply	[flat|nested] 11+ messages in thread

* [PATCH 1/2] xfs: create new metadata UUID field and incompat flag
  2015-05-08 20:40 [PATCH 0/2] allow UUID changes on V5/CRC filesystems Eric Sandeen
@ 2015-05-08 20:48 ` Eric Sandeen
  2015-05-11 16:14   ` Brian Foster
  2015-05-08 20:59 ` [PATCH 2/2] xfsprogs: Add new sb_meta_uuid field, and userspace tools to manipulate it Eric Sandeen
  1 sibling, 1 reply; 11+ messages in thread
From: Eric Sandeen @ 2015-05-08 20:48 UTC (permalink / raw)
  To: Eric Sandeen, xfs-oss

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 or clearing
of the incompat flag as appropriate, as the UUID gets written.

If the incompat flag is not set, copy the user-visible UUID into
into the meta_uuid slot in memory; this 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>
---

diff --git a/fs/xfs/libxfs/xfs_format.h b/fs/xfs/libxfs/xfs_format.h
index 4daaa66..88c38df 100644
--- a/fs/xfs/libxfs/xfs_format.h
+++ b/fs/xfs/libxfs/xfs_format.h
@@ -100,7 +100,7 @@ typedef struct xfs_sb {
 	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 @@ typedef struct xfs_sb {
 
 	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 @@ typedef struct xfs_dsb {
 	__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 @@ typedef struct xfs_dsb {
 
 	__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;
@@ -457,8 +459,10 @@ xfs_sb_has_ro_compat_feature(
 }
 
 #define XFS_SB_FEAT_INCOMPAT_FTYPE	(1 << 0)	/* filetype in dirent */
+#define XFS_SB_FEAT_INCOMPAT_META_UUID	(1 << 1)	/* metadata UUID */
 #define XFS_SB_FEAT_INCOMPAT_ALL \
-		(XFS_SB_FEAT_INCOMPAT_FTYPE)
+		(XFS_SB_FEAT_INCOMPAT_FTYPE | \
+		 XFS_SB_FEAT_INCOMPAT_META_UUID)
 
 #define XFS_SB_FEAT_INCOMPAT_UNKNOWN	~XFS_SB_FEAT_INCOMPAT_ALL
 static inline bool
@@ -507,6 +511,18 @@ static inline int xfs_sb_version_hasfinobt(xfs_sb_t *sbp)
 }
 
 /*
+ * 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 int xfs_sb_version_hasmetauuid(xfs_sb_t *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
  */
 
diff --git a/fs/xfs/libxfs/xfs_sb.c b/fs/xfs/libxfs/xfs_sb.c
index dc4bfc5..547230f 100644
--- a/fs/xfs/libxfs/xfs_sb.c
+++ b/fs/xfs/libxfs/xfs_sb.c
@@ -377,6 +377,13 @@ __xfs_sb_from_disk(
 	to->sb_pad = 0;
 	to->sb_pquotino = be64_to_cpu(from->sb_pquotino);
 	to->sb_lsn = be64_to_cpu(from->sb_lsn);
+	if (xfs_sb_version_hasmetauuid(to)) {
+		memcpy(&to->sb_meta_uuid, &from->sb_meta_uuid,
+					sizeof(to->sb_meta_uuid));
+	} else {
+		memcpy(&to->sb_meta_uuid, &from->sb_uuid,
+					sizeof(to->sb_meta_uuid));
+	}
 	/* Convert on-disk flags to in-memory flags? */
 	if (convert_xquota)
 		xfs_sb_quota_from_disk(to);
@@ -518,6 +525,10 @@ xfs_sb_to_disk(
 				cpu_to_be32(from->sb_features_log_incompat);
 		to->sb_pad = 0;
 		to->sb_lsn = cpu_to_be64(from->sb_lsn);
+		if (xfs_sb_version_hasmetauuid(from)) {
+			memcpy(&to->sb_meta_uuid, &from->sb_meta_uuid,
+						sizeof(to->sb_meta_uuid));
+		}
 	}
 }
 
diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c
index 516162b..27f76ca 100644
--- a/fs/xfs/libxfs/xfs_alloc.c
+++ b/fs/xfs/libxfs/xfs_alloc.c
@@ -450,7 +450,7 @@ xfs_agfl_verify(
 	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;
@@ -2203,7 +2203,7 @@ xfs_agf_verify(
 	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) &&
diff --git a/fs/xfs/libxfs/xfs_alloc_btree.c b/fs/xfs/libxfs/xfs_alloc_btree.c
index 59d521c..90de071 100644
--- a/fs/xfs/libxfs/xfs_alloc_btree.c
+++ b/fs/xfs/libxfs/xfs_alloc_btree.c
@@ -295,7 +295,7 @@ xfs_allocbt_verify(
 	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;
@@ -313,7 +313,7 @@ xfs_allocbt_verify(
 	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;
diff --git a/fs/xfs/libxfs/xfs_attr_leaf.c b/fs/xfs/libxfs/xfs_attr_leaf.c
index 04e79d5..6755762 100644
--- a/fs/xfs/libxfs/xfs_attr_leaf.c
+++ b/fs/xfs/libxfs/xfs_attr_leaf.c
@@ -262,7 +262,7 @@ xfs_attr3_leaf_verify(
 		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;
@@ -1056,7 +1056,7 @@ xfs_attr3_leaf_create(
 
 		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 {
diff --git a/fs/xfs/libxfs/xfs_attr_remote.c b/fs/xfs/libxfs/xfs_attr_remote.c
index 20de88d..eba0d1e 100644
--- a/fs/xfs/libxfs/xfs_attr_remote.c
+++ b/fs/xfs/libxfs/xfs_attr_remote.c
@@ -100,7 +100,7 @@ xfs_attr3_rmt_verify(
 		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;
@@ -217,7 +217,7 @@ xfs_attr3_rmt_hdr_set(
 	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);
 
diff --git a/fs/xfs/libxfs/xfs_bmap_btree.c b/fs/xfs/libxfs/xfs_bmap_btree.c
index 2c44c8e..6b0cf65 100644
--- a/fs/xfs/libxfs/xfs_bmap_btree.c
+++ b/fs/xfs/libxfs/xfs_bmap_btree.c
@@ -349,7 +349,8 @@ xfs_bmbt_to_bmdr(
 
 	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
@@ -647,7 +648,7 @@ xfs_bmbt_verify(
 	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;
diff --git a/fs/xfs/libxfs/xfs_btree.c b/fs/xfs/libxfs/xfs_btree.c
index c72283d..f7d7ee7 100644
--- a/fs/xfs/libxfs/xfs_btree.c
+++ b/fs/xfs/libxfs/xfs_btree.c
@@ -65,7 +65,8 @@ xfs_btree_check_lblock(
 
 	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);
 	}
@@ -115,7 +116,8 @@ xfs_btree_check_sblock(
 
 	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);
 	}
@@ -1000,7 +1002,7 @@ xfs_btree_init_block_int(
 		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;
 		}
@@ -1013,7 +1015,7 @@ xfs_btree_init_block_int(
 		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;
 		}
 	}
diff --git a/fs/xfs/libxfs/xfs_da_btree.c b/fs/xfs/libxfs/xfs_da_btree.c
index 2385f8c..e9f6709 100644
--- a/fs/xfs/libxfs/xfs_da_btree.c
+++ b/fs/xfs/libxfs/xfs_da_btree.c
@@ -146,7 +146,7 @@ xfs_da3_node_verify(
 		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;
@@ -324,7 +324,7 @@ xfs_da3_node_create(
 		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;
 	}
diff --git a/fs/xfs/libxfs/xfs_dir2_block.c b/fs/xfs/libxfs/xfs_dir2_block.c
index 9354e19..4778d1d 100644
--- a/fs/xfs/libxfs/xfs_dir2_block.c
+++ b/fs/xfs/libxfs/xfs_dir2_block.c
@@ -67,7 +67,7 @@ xfs_dir3_block_verify(
 	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;
@@ -157,7 +157,7 @@ xfs_dir3_block_init(
 		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;
 
 	}
diff --git a/fs/xfs/libxfs/xfs_dir2_data.c b/fs/xfs/libxfs/xfs_dir2_data.c
index de1ea16..6a57fdb 100644
--- a/fs/xfs/libxfs/xfs_dir2_data.c
+++ b/fs/xfs/libxfs/xfs_dir2_data.c
@@ -220,7 +220,7 @@ xfs_dir3_data_verify(
 	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;
@@ -604,7 +604,7 @@ xfs_dir3_data_init(
 		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);
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 @@ xfs_dir3_leaf_verify(
 
 		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 @@ xfs_dir3_leaf_init(
 					 : 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);
diff --git a/fs/xfs/libxfs/xfs_dir2_node.c b/fs/xfs/libxfs/xfs_dir2_node.c
index 41b80d3..527b733 100644
--- a/fs/xfs/libxfs/xfs_dir2_node.c
+++ b/fs/xfs/libxfs/xfs_dir2_node.c
@@ -93,7 +93,7 @@ xfs_dir3_free_verify(
 
 		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;
@@ -226,7 +226,7 @@ xfs_dir3_free_get_buf(
 
 		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);
diff --git a/fs/xfs/libxfs/xfs_dquot_buf.c b/fs/xfs/libxfs/xfs_dquot_buf.c
index 6fbf2d8..5331b7f 100644
--- a/fs/xfs/libxfs/xfs_dquot_buf.c
+++ b/fs/xfs/libxfs/xfs_dquot_buf.c
@@ -163,7 +163,7 @@ xfs_dqcheck(
 	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);
 	}
@@ -198,7 +198,7 @@ xfs_dquot_buf_verify_crc(
 		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;
diff --git a/fs/xfs/libxfs/xfs_ialloc.c b/fs/xfs/libxfs/xfs_ialloc.c
index 07349a1..d9b90c0 100644
--- a/fs/xfs/libxfs/xfs_ialloc.c
+++ b/fs/xfs/libxfs/xfs_ialloc.c
@@ -307,7 +307,8 @@ xfs_ialloc_inode_init(
 			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 */
@@ -2049,7 +2050,7 @@ xfs_agi_verify(
 	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.
diff --git a/fs/xfs/libxfs/xfs_ialloc_btree.c b/fs/xfs/libxfs/xfs_ialloc_btree.c
index 964c465..0fa2a27 100644
--- a/fs/xfs/libxfs/xfs_ialloc_btree.c
+++ b/fs/xfs/libxfs/xfs_ialloc_btree.c
@@ -230,7 +230,7 @@ xfs_inobt_verify(
 	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;
diff --git a/fs/xfs/libxfs/xfs_inode_buf.c b/fs/xfs/libxfs/xfs_inode_buf.c
index 002b6b3..0f9563e 100644
--- a/fs/xfs/libxfs/xfs_inode_buf.c
+++ b/fs/xfs/libxfs/xfs_inode_buf.c
@@ -306,7 +306,7 @@ xfs_dinode_verify(
 		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;
 }
@@ -368,7 +368,7 @@ xfs_iread(
 		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;
diff --git a/fs/xfs/libxfs/xfs_symlink_remote.c b/fs/xfs/libxfs/xfs_symlink_remote.c
index e7e26bd..8f8af05 100644
--- a/fs/xfs/libxfs/xfs_symlink_remote.c
+++ b/fs/xfs/libxfs/xfs_symlink_remote.c
@@ -63,7 +63,7 @@ xfs_symlink_hdr_set(
 	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;
@@ -107,7 +107,7 @@ xfs_symlink_verify(
 		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;
diff --git a/fs/xfs/xfs_dquot.c b/fs/xfs/xfs_dquot.c
index 02c01bb..e0c7e15 100644
--- a/fs/xfs/xfs_dquot.c
+++ b/fs/xfs/xfs_dquot.c
@@ -251,7 +251,7 @@ xfs_qm_init_dquot_blk(
 		d->dd_diskdq.d_id = cpu_to_be32(curid);
 		d->dd_diskdq.d_flags = type;
 		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);
 		}
diff --git a/fs/xfs/xfs_fsops.c b/fs/xfs/xfs_fsops.c
index cb7e8a2..9c892cd 100644
--- a/fs/xfs/xfs_fsops.c
+++ b/fs/xfs/xfs_fsops.c
@@ -248,7 +248,7 @@ xfs_growfs_data_private(
 		agf->agf_freeblks = cpu_to_be32(tmpsize);
 		agf->agf_longest = cpu_to_be32(tmpsize);
 		if (xfs_sb_version_hascrc(&mp->m_sb))
-			uuid_copy(&agf->agf_uuid, &mp->m_sb.sb_uuid);
+			uuid_copy(&agf->agf_uuid, &mp->m_sb.sb_meta_uuid);
 
 		error = xfs_bwrite(bp);
 		xfs_buf_relse(bp);
@@ -271,7 +271,7 @@ xfs_growfs_data_private(
 		if (xfs_sb_version_hascrc(&mp->m_sb)) {
 			agfl->agfl_magicnum = cpu_to_be32(XFS_AGFL_MAGIC);
 			agfl->agfl_seqno = cpu_to_be32(agno);
-			uuid_copy(&agfl->agfl_uuid, &mp->m_sb.sb_uuid);
+			uuid_copy(&agfl->agfl_uuid, &mp->m_sb.sb_meta_uuid);
 		}
 
 		agfl_bno = XFS_BUF_TO_AGFL_BNO(mp, bp);
@@ -307,7 +307,7 @@ xfs_growfs_data_private(
 		agi->agi_newino = cpu_to_be32(NULLAGINO);
 		agi->agi_dirino = cpu_to_be32(NULLAGINO);
 		if (xfs_sb_version_hascrc(&mp->m_sb))
-			uuid_copy(&agi->agi_uuid, &mp->m_sb.sb_uuid);
+			uuid_copy(&agi->agi_uuid, &mp->m_sb.sb_meta_uuid);
 		if (xfs_sb_version_hasfinobt(&mp->m_sb)) {
 			agi->agi_free_root = cpu_to_be32(XFS_FIBT_BLOCK(mp));
 			agi->agi_free_level = cpu_to_be32(1);
diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index d6ebc85..9a2ecb7 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -787,7 +787,7 @@ xfs_ialloc(
 
 	if (ip->i_d.di_version == 3) {
 		ASSERT(ip->i_d.di_ino == ino);
-		ASSERT(uuid_equal(&ip->i_d.di_uuid, &mp->m_sb.sb_uuid));
+		ASSERT(uuid_equal(&ip->i_d.di_uuid, &mp->m_sb.sb_meta_uuid));
 		ip->i_d.di_crc = 0;
 		ip->i_d.di_changecount = 1;
 		ip->i_d.di_lsn = 0;

_______________________________________________
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^ permalink raw reply related	[flat|nested] 11+ messages in thread

* [PATCH 2/2] xfsprogs: Add new sb_meta_uuid field, and userspace tools to manipulate it
  2015-05-08 20:40 [PATCH 0/2] allow UUID changes on V5/CRC filesystems Eric Sandeen
  2015-05-08 20:48 ` [PATCH 1/2] xfs: create new metadata UUID field and incompat flag Eric Sandeen
@ 2015-05-08 20:59 ` Eric Sandeen
  2015-05-08 21:14   ` Eric Sandeen
  2015-05-08 21:49   ` [PATCH 2/2 V2] " Eric Sandeen
  1 sibling, 2 replies; 11+ messages in thread
From: Eric Sandeen @ 2015-05-08 20:59 UTC (permalink / raw)
  To: Eric Sandeen, xfs-oss

This adds a new superblock field, sb_meta_uuid.  This allows us to
change the use-visible UUID on crc-enabled filesytems from userspace
if desired, by copying the existing UUID to the new location for
metadata comparisons.  If this is done, an incompat flag must be
set to prevent older filesystems from mounting the filesystem, but
the original UUID can be restored, and the incompat flag removed,
with a new xfs_db / xfs_admin UUID command, "restore."

Much of this patch mirrors the kernel patch in simply renaming
the field used for metadata uuid comparison; other bits:

* Teach xfs_db to print the new meta_uuid field
* Allow xfs_db to generate a new UUID for CRC-enabled filesystems
* Allow xfs_db to revert to the original UUID and clear the flag
* Fix up xfs_copy to work with CRC-enabled filesystems
* Update the xfs_admin manpage to show the UUID "generate" command

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
---

I could break this into core libxfs & functional patches if you like;
in retrospect that's probably a good idea.

Right now xfs_db "uuid restore" squawks if called on a filesystem that
doesn't need it; perhaps that should be removed...

I'm not totally sold on the "restore" command name either; open to
suggestions.


diff --git a/include/xfs_sb.h b/include/xfs_sb.h
index 950d1ea..c27c294 100644
--- a/include/xfs_sb.h
+++ b/include/xfs_sb.h
@@ -107,7 +107,7 @@ typedef struct xfs_sb {
 	xfs_drfsbno_t	sb_dblocks;	/* number of data blocks */
 	xfs_drfsbno_t	sb_rblocks;	/* number of realtime blocks */
 	xfs_drtbno_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_dfsbno_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 */
@@ -178,6 +178,7 @@ typedef struct xfs_sb {
 
 	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;
@@ -194,7 +195,7 @@ typedef struct xfs_dsb {
 	__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 */
@@ -264,6 +265,7 @@ typedef struct xfs_dsb {
 
 	__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;
@@ -287,7 +289,7 @@ typedef enum {
 	XFS_SBS_FEATURES2, XFS_SBS_BAD_FEATURES2, XFS_SBS_FEATURES_COMPAT,
 	XFS_SBS_FEATURES_RO_COMPAT, XFS_SBS_FEATURES_INCOMPAT,
 	XFS_SBS_FEATURES_LOG_INCOMPAT, XFS_SBS_CRC, XFS_SBS_PAD,
-	XFS_SBS_PQUOTINO, XFS_SBS_LSN,
+	XFS_SBS_PQUOTINO, XFS_SBS_LSN, XFS_SBS_META_UUID,
 	XFS_SBS_FIELDCOUNT
 } xfs_sb_field_t;
 
@@ -319,6 +321,7 @@ typedef enum {
 #define XFS_SB_FEATURES_LOG_INCOMPAT XFS_SB_MVAL(FEATURES_LOG_INCOMPAT)
 #define XFS_SB_CRC		XFS_SB_MVAL(CRC)
 #define XFS_SB_PQUOTINO		XFS_SB_MVAL(PQUOTINO)
+#define	XFS_SB_META_UUID	XFS_SB_MVAL(META_UUID)
 #define	XFS_SB_NUM_BITS		((int)XFS_SBS_FIELDCOUNT)
 #define	XFS_SB_ALL_BITS		((1LL << XFS_SB_NUM_BITS) - 1)
 #define	XFS_SB_MOD_BITS		\
@@ -328,7 +331,7 @@ typedef enum {
 	 XFS_SB_ICOUNT | XFS_SB_IFREE | XFS_SB_FDBLOCKS | XFS_SB_FEATURES2 | \
 	 XFS_SB_BAD_FEATURES2 | XFS_SB_FEATURES_COMPAT | \
 	 XFS_SB_FEATURES_RO_COMPAT | XFS_SB_FEATURES_INCOMPAT | \
-	 XFS_SB_FEATURES_LOG_INCOMPAT | XFS_SB_PQUOTINO)
+	 XFS_SB_FEATURES_LOG_INCOMPAT | XFS_SB_PQUOTINO | XFS_SB_META_UUID)
 
 
 /*
@@ -600,8 +603,10 @@ xfs_sb_has_ro_compat_feature(
 }
 
 #define XFS_SB_FEAT_INCOMPAT_FTYPE	(1 << 0)	/* filetype in dirent */
+#define XFS_SB_FEAT_INCOMPAT_META_UUID (1 << 1)		/* metadata UUID */
 #define XFS_SB_FEAT_INCOMPAT_ALL \
-		(XFS_SB_FEAT_INCOMPAT_FTYPE)
+		(XFS_SB_FEAT_INCOMPAT_FTYPE | \
+		 XFS_SB_FEAT_INCOMPAT_META_UUID)
 
 #define XFS_SB_FEAT_INCOMPAT_UNKNOWN	~XFS_SB_FEAT_INCOMPAT_ALL
 static inline bool
@@ -650,6 +655,18 @@ static inline int xfs_sb_version_hasfinobt(xfs_sb_t *sbp)
 }
 
 /*
+ * 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 int xfs_sb_version_hasmetauuid(xfs_sb_t *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
  */
 
diff --git a/libxfs/xfs_sb.c b/libxfs/xfs_sb.c
index ea89367..c9ef019 100644
--- a/libxfs/xfs_sb.c
+++ b/libxfs/xfs_sb.c
@@ -81,6 +81,7 @@ static const struct {
 	{ offsetof(xfs_sb_t, sb_pad),		0 },
 	{ offsetof(xfs_sb_t, sb_pquotino),	0 },
 	{ offsetof(xfs_sb_t, sb_lsn),		0 },
+	{ offsetof(xfs_sb_t, sb_meta_uuid),		1 },
 	{ sizeof(xfs_sb_t),			0 }
 };
 
@@ -413,6 +414,13 @@ xfs_sb_from_disk(
 	to->sb_pad = 0;
 	to->sb_pquotino = be64_to_cpu(from->sb_pquotino);
 	to->sb_lsn = be64_to_cpu(from->sb_lsn);
+	if (xfs_sb_version_hasmetauuid(to)) {
+		memcpy(&to->sb_meta_uuid, &from->sb_meta_uuid,
+					sizeof(to->sb_meta_uuid));
+	} else {
+		memcpy(&to->sb_meta_uuid, &from->sb_uuid,
+					sizeof(to->sb_meta_uuid));
+	}
 }
 
 static inline void
@@ -490,6 +498,13 @@ xfs_sb_to_disk(
 	/* We should never write the crc here, it's updated in the IO path */
 	fields &= ~XFS_SB_CRC;
 
+	/*
+	 * If the metadata-specific UUID feature isn't set, it's only set
+	 * in memory; don't write it out.
+	 */
+	if (!xfs_sb_version_hasmetauuid(from))
+		fields &= ~XFS_SB_UUID;
+
 	xfs_sb_quota_to_disk(to, from, &fields);
 	while (fields) {
 		f = (xfs_sb_field_t)xfs_lowbit64((__uint64_t)fields);
diff --git a/copy/xfs_copy.c b/copy/xfs_copy.c
index 279527c..a58eee5 100644
--- a/copy/xfs_copy.c
+++ b/copy/xfs_copy.c
@@ -466,6 +466,34 @@ write_wbuf(void)
 	sighold(SIGCHLD);
 }
 
+void
+sb_update_uuid(
+	xfs_sb_t	*sb,
+	ag_header_t	*ag_hdr,
+	thread_args	*tcarg)
+{
+	/*
+	 * If this filesystem has CRCs, the original UUID is stamped into
+	 * all metadata.  We need to copy the original UUID into the meta_uuid
+	 * slot and set the incompat flag if that hasn't already been done.
+	 */
+	if (xfs_sb_version_hascrc(sb) && !xfs_sb_version_hasmetauuid(sb)) {
+		__be32 feat;
+
+		feat = be32_to_cpu(ag_hdr->xfs_sb->sb_features_incompat);
+		feat |= XFS_SB_FEAT_INCOMPAT_META_UUID;
+		ag_hdr->xfs_sb->sb_features_incompat = cpu_to_be32(feat);
+		platform_uuid_copy(&ag_hdr->xfs_sb->sb_meta_uuid,
+				   &ag_hdr->xfs_sb->sb_uuid);
+	}
+
+	platform_uuid_copy(&ag_hdr->xfs_sb->sb_uuid, &tcarg->uuid);
+
+	/* We changed the UUID, so update the superblock CRC if needed */
+	if (xfs_sb_version_hascrc(sb))
+		xfs_update_cksum((char *)&ag_hdr->xfs_sb, sb->sb_sectsize,
+							 XFS_SB_CRC_OFF);
+}
 
 int
 main(int argc, char **argv)
@@ -659,16 +687,6 @@ main(int argc, char **argv)
 	sb = &mbuf.m_sb;
 	libxfs_sb_from_disk(sb, XFS_BUF_TO_SBP(sbp));
 
-	/*
-	 * For now, V5 superblock filesystems are not supported without -d;
-	 * we do not have the infrastructure yet to fix CRCs when a new UUID
-	 * is generated.
-	 */
-	if (xfs_sb_version_hascrc(sb) && !duplicate) {
-		do_log(_("%s: Cannot yet copy V5 fs without '-d'\n"), progname);
-		exit(1);
-	}
-
 	mp = libxfs_mount(&mbuf, sb, xargs.ddev, xargs.logdev, xargs.rtdev, 0);
 	if (mp == NULL) {
 		do_log(_("%s: %s filesystem failed to initialize\n"
@@ -1127,8 +1145,7 @@ main(int argc, char **argv)
 			/* do each thread in turn, each has its own UUID */
 
 			for (j = 0, tcarg = targ; j < num_targets; j++)  {
-				platform_uuid_copy(&ag_hdr.xfs_sb->sb_uuid,
-							&tcarg->uuid);
+				sb_update_uuid(sb, &ag_hdr, tcarg);
 				do_write(tcarg);
 				tcarg++;
 			}
diff --git a/db/sb.c b/db/sb.c
index 23ec87c..6b5bab0 100644
--- a/db/sb.c
+++ b/db/sb.c
@@ -29,6 +29,8 @@
 #include "output.h"
 #include "init.h"
 
+#define uuid_equal(s,d)		(platform_uuid_compare((s),(d)) == 0)
+
 static int	sb_f(int argc, char **argv);
 static void     sb_help(void);
 static int	uuid_f(int argc, char **argv);
@@ -121,6 +123,7 @@ const field_t	sb_flds[] = {
 	{ "crc", FLDT_CRC, OI(OFF(crc)), C1, 0, TYP_NONE },
 	{ "pquotino", FLDT_INO, OI(OFF(pquotino)), C1, 0, TYP_INODE },
 	{ "lsn", FLDT_UINT64X, OI(OFF(lsn)), C1, 0, TYP_NONE },
+	{ "meta_uuid", FLDT_UUID, OI(OFF(meta_uuid)), C1, 0, TYP_NONE },
 	{ NULL }
 };
 
@@ -324,6 +327,7 @@ do_uuid(xfs_agnumber_t agno, uuid_t *uuid)
 {
 	xfs_sb_t	tsb;
 	static uuid_t	uu;
+	__int64_t	fields = XFS_SB_UUID;
 
 	if (!get_sb(agno, &tsb))
 		return NULL;
@@ -333,9 +337,38 @@ do_uuid(xfs_agnumber_t agno, uuid_t *uuid)
 		pop_cur();
 		return &uu;
 	}
+
 	/* set uuid */
+	if (!xfs_sb_version_hascrc(&tsb))
+		goto write;
+	/*
+	 * If we have CRCs, and this UUID differs from that stamped in the
+	 * metadata, set the incompat flag and copy the old one to the
+	 * metadata-specific location.
+	 *
+	 * If we are setting the user-visible UUID back to match the metadata
+	 * UUID, clear the metadata-specific location and the incompat flag.
+	 */
+	if (!xfs_sb_version_hasmetauuid(&tsb) &&
+	    !uuid_equal(uuid, &mp->m_sb.sb_meta_uuid)) {
+		mp->m_sb.sb_features_incompat |= XFS_SB_FEAT_INCOMPAT_META_UUID;
+		tsb.sb_features_incompat |= XFS_SB_FEAT_INCOMPAT_META_UUID;
+		memcpy(&tsb.sb_meta_uuid, &tsb.sb_uuid, sizeof(uuid_t));
+		fields |= XFS_SB_META_UUID | XFS_SB_FEATURES_INCOMPAT;
+	} else if (xfs_sb_version_hasmetauuid(&tsb) &&
+		   uuid_equal(uuid, &mp->m_sb.sb_meta_uuid)) {
+		memset(&tsb.sb_meta_uuid, 0, sizeof(uuid_t));
+		/* Write those zeros now; it's ignored once we clear the flag */
+		libxfs_sb_to_disk(iocur_top->data, &tsb, XFS_SB_META_UUID);
+		mp->m_sb.sb_features_incompat &=
+						~XFS_SB_FEAT_INCOMPAT_META_UUID;
+		tsb.sb_features_incompat &= ~XFS_SB_FEAT_INCOMPAT_META_UUID;
+		fields |= XFS_SB_FEATURES_INCOMPAT;
+	}
+
+write:
 	memcpy(&tsb.sb_uuid, uuid, sizeof(uuid_t));
-	libxfs_sb_to_disk(iocur_top->data, &tsb, XFS_SB_UUID);
+	libxfs_sb_to_disk(iocur_top->data, &tsb, fields);
 	write_cur();
 	return uuid;
 }
@@ -363,18 +396,6 @@ uuid_f(
 			return 0;
 		}
 
-		/*
-		 * For now, changing the UUID of V5 superblock filesystems is
-		 * not supported; we do not have the infrastructure to fix all
-		 * other metadata when a new superblock UUID is generated.
-		 */
-		if (xfs_sb_version_hascrc(&mp->m_sb) &&
-		    strcasecmp(argv[1], "rewrite")) {
-			dbprintf(_("%s: only 'rewrite' supported on V5 fs\n"),
-				progname);
-			return 0;
-		}
-
 		if (!strcasecmp(argv[1], "generate")) {
 			platform_uuid_generate(&uu);
 		} else if (!strcasecmp(argv[1], "nil")) {
@@ -388,6 +409,16 @@ uuid_f(
 			memcpy(&uu, uup, sizeof(uuid_t));
 			platform_uuid_unparse(&uu, bp);
 			dbprintf(_("old UUID = %s\n"), bp);
+		} else if (!strcasecmp(argv[1], "restore")) {
+			xfs_sb_t	tsb;
+
+			if (!get_sb(0, &tsb))
+				return 0;
+			if (!xfs_sb_version_hasmetauuid(&tsb)) {
+				dbprintf(_("META_UUID not set"));
+				return 0;
+			}
+			memcpy(&uu, mp->m_sb.sb_meta_uuid, sizeof(uuid_t));
 		} else {
 			if (platform_uuid_parse(argv[1], &uu)) {
 				dbprintf(_("invalid UUID\n"));
@@ -658,6 +689,8 @@ version_string(
 		strcat(s, ",CRC");
 	if (xfs_sb_version_hasftype(sbp))
 		strcat(s, ",FTYPE");
+	if (xfs_sb_version_hasmetauuid(sbp))
+		strcat(s, ",META_UUID");
 	return s;
 }
 
diff --git a/libxfs/util.c b/libxfs/util.c
index 49eb76d..ea698c4 100644
--- a/libxfs/util.c
+++ b/libxfs/util.c
@@ -250,7 +250,7 @@ libxfs_ialloc(
 
 	if (ip->i_d.di_version == 3) {
 		ASSERT(ip->i_d.di_ino == ino);
-		ASSERT(uuid_equal(&ip->i_d.di_uuid, &mp->m_sb.sb_uuid));
+		ASSERT(uuid_equal(&ip->i_d.di_uuid, &mp->m_sb.sb_meta_uuid));
 		ip->i_d.di_crc = 0;
 		ip->i_d.di_changecount = 1;
 		ip->i_d.di_lsn = 0;
diff --git a/libxfs/xfs_alloc.c b/libxfs/xfs_alloc.c
index 6c82be0..06757c3 100644
--- a/libxfs/xfs_alloc.c
+++ b/libxfs/xfs_alloc.c
@@ -426,7 +426,7 @@ xfs_agfl_verify(
 	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;
@@ -2181,7 +2181,7 @@ xfs_agf_verify(
 	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) &&
diff --git a/libxfs/xfs_alloc_btree.c b/libxfs/xfs_alloc_btree.c
index 215be7e..cefa18b 100644
--- a/libxfs/xfs_alloc_btree.c
+++ b/libxfs/xfs_alloc_btree.c
@@ -279,7 +279,7 @@ xfs_allocbt_verify(
 	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;
@@ -297,7 +297,7 @@ xfs_allocbt_verify(
 	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;
diff --git a/libxfs/xfs_attr_leaf.c b/libxfs/xfs_attr_leaf.c
index f7f02ae..e9f96ec 100644
--- a/libxfs/xfs_attr_leaf.c
+++ b/libxfs/xfs_attr_leaf.c
@@ -161,7 +161,7 @@ xfs_attr3_leaf_verify(
 		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;
@@ -952,7 +952,7 @@ xfs_attr3_leaf_create(
 
 		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 {
diff --git a/libxfs/xfs_attr_remote.c b/libxfs/xfs_attr_remote.c
index 08b983b..62abaec 100644
--- a/libxfs/xfs_attr_remote.c
+++ b/libxfs/xfs_attr_remote.c
@@ -78,7 +78,7 @@ xfs_attr3_rmt_verify(
 		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;
@@ -194,7 +194,7 @@ xfs_attr3_rmt_hdr_set(
 	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);
 
diff --git a/libxfs/xfs_bmap_btree.c b/libxfs/xfs_bmap_btree.c
index a4bd69d..9913958 100644
--- a/libxfs/xfs_bmap_btree.c
+++ b/libxfs/xfs_bmap_btree.c
@@ -412,7 +412,8 @@ xfs_bmbt_to_bmdr(
 
 	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
@@ -712,7 +713,7 @@ xfs_bmbt_verify(
 	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;
diff --git a/libxfs/xfs_btree.c b/libxfs/xfs_btree.c
index cc823f5..a8436f5 100644
--- a/libxfs/xfs_btree.c
+++ b/libxfs/xfs_btree.c
@@ -50,7 +50,8 @@ xfs_btree_check_lblock(
 
 	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);
 	}
@@ -100,7 +101,8 @@ xfs_btree_check_sblock(
 
 	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);
 	}
@@ -992,7 +994,7 @@ xfs_btree_init_block_int(
 		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;
 		}
@@ -1005,7 +1007,7 @@ xfs_btree_init_block_int(
 		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;
 		}
 	}
diff --git a/libxfs/xfs_da_btree.c b/libxfs/xfs_da_btree.c
index b731b54..0323dc7 100644
--- a/libxfs/xfs_da_btree.c
+++ b/libxfs/xfs_da_btree.c
@@ -172,7 +172,7 @@ xfs_da3_node_verify(
 		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;
@@ -349,7 +349,7 @@ xfs_da3_node_create(
 		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;
 	}
diff --git a/libxfs/xfs_dir2_block.c b/libxfs/xfs_dir2_block.c
index cede01f..2a25059 100644
--- a/libxfs/xfs_dir2_block.c
+++ b/libxfs/xfs_dir2_block.c
@@ -51,7 +51,7 @@ xfs_dir3_block_verify(
 	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;
@@ -141,7 +141,7 @@ xfs_dir3_block_init(
 		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;
 
 	}
diff --git a/libxfs/xfs_dir2_data.c b/libxfs/xfs_dir2_data.c
index dc9df4d..4c79d7c 100644
--- a/libxfs/xfs_dir2_data.c
+++ b/libxfs/xfs_dir2_data.c
@@ -186,7 +186,7 @@ xfs_dir3_data_verify(
 	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;
@@ -573,7 +573,7 @@ xfs_dir3_data_init(
 		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);
diff --git a/libxfs/xfs_dir2_leaf.c b/libxfs/xfs_dir2_leaf.c
index 8e0cbc9..a918e15 100644
--- a/libxfs/xfs_dir2_leaf.c
+++ b/libxfs/xfs_dir2_leaf.c
@@ -186,7 +186,7 @@ xfs_dir3_leaf_verify(
 
 		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;
@@ -337,7 +337,7 @@ xfs_dir3_leaf_init(
 					 : 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);
diff --git a/libxfs/xfs_dir2_node.c b/libxfs/xfs_dir2_node.c
index 3737e4e..309e7ce 100644
--- a/libxfs/xfs_dir2_node.c
+++ b/libxfs/xfs_dir2_node.c
@@ -78,7 +78,7 @@ xfs_dir3_free_verify(
 
 		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;
@@ -257,7 +257,7 @@ xfs_dir3_free_get_buf(
 
 		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;
 	xfs_dir3_free_hdr_to_disk(bp->b_addr, &hdr);
diff --git a/libxfs/xfs_dquot_buf.c b/libxfs/xfs_dquot_buf.c
index e089ec8..f75bfe3 100644
--- a/libxfs/xfs_dquot_buf.c
+++ b/libxfs/xfs_dquot_buf.c
@@ -146,7 +146,7 @@ xfs_dqcheck(
 	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);
 	}
@@ -181,7 +181,7 @@ xfs_dquot_buf_verify_crc(
 		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;
diff --git a/libxfs/xfs_ialloc.c b/libxfs/xfs_ialloc.c
index b20a9ec..ae0804c 100644
--- a/libxfs/xfs_ialloc.c
+++ b/libxfs/xfs_ialloc.c
@@ -295,7 +295,8 @@ xfs_ialloc_inode_init(
 			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 */
@@ -1947,7 +1948,7 @@ xfs_agi_verify(
 	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.
diff --git a/libxfs/xfs_ialloc_btree.c b/libxfs/xfs_ialloc_btree.c
index c337389..320984f 100644
--- a/libxfs/xfs_ialloc_btree.c
+++ b/libxfs/xfs_ialloc_btree.c
@@ -214,7 +214,7 @@ xfs_inobt_verify(
 	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;
diff --git a/libxfs/xfs_inode_buf.c b/libxfs/xfs_inode_buf.c
index de16ed9..1c0047d 100644
--- a/libxfs/xfs_inode_buf.c
+++ b/libxfs/xfs_inode_buf.c
@@ -295,7 +295,7 @@ xfs_dinode_verify(
 		return false;
 	if (be64_to_cpu(dip->di_ino) != 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;
 }
diff --git a/libxfs/xfs_symlink_remote.c b/libxfs/xfs_symlink_remote.c
index ebf60ac..3f8374e 100644
--- a/libxfs/xfs_symlink_remote.c
+++ b/libxfs/xfs_symlink_remote.c
@@ -48,7 +48,7 @@ xfs_symlink_hdr_set(
 	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;
@@ -93,7 +93,7 @@ xfs_symlink_verify(
 		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;
diff --git a/libxlog/util.c b/libxlog/util.c
index 949b79d..652d391 100644
--- a/libxlog/util.c
+++ b/libxlog/util.c
@@ -28,8 +28,10 @@ header_check_uuid(xfs_mount_t *mp, xlog_rec_header_t *head)
 {
     char uu_log[64], uu_sb[64];
 
-    if (print_skip_uuid) return 0;
-    if (!platform_uuid_compare(&mp->m_sb.sb_uuid, &head->h_fs_uuid)) return 0;
+    if (print_skip_uuid)
+		return 0;
+    if (!platform_uuid_compare(&mp->m_sb.sb_uuid, &head->h_fs_uuid))
+		return 0;
 
     platform_uuid_unparse(&mp->m_sb.sb_uuid, uu_sb);
     platform_uuid_unparse(&head->h_fs_uuid, uu_log);
diff --git a/man/man8/xfs_admin.8 b/man/man8/xfs_admin.8
index b393d74..0600540 100644
--- a/man/man8/xfs_admin.8
+++ b/man/man8/xfs_admin.8
@@ -98,7 +98,12 @@ The
 .I uuid
 may also be
 .BR generate ,
-which will generate a new UUID for the filesystem.
+which will generate a new UUID for the filesystem.  Note that on CRC-enabled
+filesystems, this will set an incompatible flag such that older kernels will
+not be able to mount the filesystem.  To remove this incompatible flag, use
+.BR restore ,
+which will match the UUID to the metadata UUID and remove the incompatible
+feature flag.
 .TP
 .B \-V
 Prints the version number and exits.


diff --git a/man/man8/xfs_db.8 b/man/man8/xfs_db.8
index d527230..7c471aa 100644
--- a/man/man8/xfs_db.8
+++ b/man/man8/xfs_db.8
@@ -664,7 +664,7 @@ The possible data types are:
 .BR sb ", " symlink " and " text .
 See the TYPES section below for more information on these data types.
 .TP
-.BI "uuid [" uuid " | " generate " | " rewrite ]
+.BI "uuid [" uuid " | " generate " | " rewrite " | " restore ]
 Set the filesystem universally unique identifier (UUID).
 The filesystem UUID can be used by
 .BR mount (8)
@@ -675,7 +675,12 @@ can be set directly to the desired UUID, or it can
 be automatically generated using the
 .B generate
 option. These options will both write the UUID into every copy of the
-superblock in the filesystem.
+superblock in the filesystem.  On a CRC-enabled filesystem, this will
+set an incompatible superblock flag, and the filesystem will not be
+mountable with older kernels.  This can be reverted with the
+.B restore
+option, which will copy the original UUID back into place, and clear
+the incompatible flag.
 .B rewrite
 copies the current UUID from the primary superblock
 to all secondary copies of the superblock.

diff --git a/mkfs/xfs_mkfs.c b/mkfs/xfs_mkfs.c
index 5084d75..a75e90c 100644
--- a/mkfs/xfs_mkfs.c
+++ b/mkfs/xfs_mkfs.c
@@ -2755,7 +2755,8 @@ _("size %s specified for log subvolume is too large, maximum is %lld blocks\n"),
 		agf->agf_freeblks = cpu_to_be32(nbmblocks);
 		agf->agf_longest = cpu_to_be32(nbmblocks);
 		if (xfs_sb_version_hascrc(&mp->m_sb))
-			platform_uuid_copy(&agf->agf_uuid, &mp->m_sb.sb_uuid);
+			platform_uuid_copy(&agf->agf_uuid,
+					   &mp->m_sb.sb_meta_uuid);
 
 		if (loginternal && agno == logagno) {
 			be32_add_cpu(&agf->agf_freeblks, -logblocks);
@@ -2779,7 +2780,8 @@ _("size %s specified for log subvolume is too large, maximum is %lld blocks\n"),
 		if (xfs_sb_version_hascrc(&mp->m_sb)) {
 			agfl->agfl_magicnum = cpu_to_be32(XFS_AGFL_MAGIC);
 			agfl->agfl_seqno = cpu_to_be32(agno);
-			platform_uuid_copy(&agfl->agfl_uuid, &mp->m_sb.sb_uuid);
+			platform_uuid_copy(&agfl->agfl_uuid,
+					   &mp->m_sb.sb_meta_uuid);
 			for (bucket = 0; bucket < XFS_AGFL_SIZE(mp); bucket++)
 				agfl->agfl_bno[bucket] = cpu_to_be32(NULLAGBLOCK);
 		}
@@ -2810,7 +2812,8 @@ _("size %s specified for log subvolume is too large, maximum is %lld blocks\n"),
 		agi->agi_newino = cpu_to_be32(NULLAGINO);
 		agi->agi_dirino = cpu_to_be32(NULLAGINO);
 		if (xfs_sb_version_hascrc(&mp->m_sb))
-			platform_uuid_copy(&agi->agi_uuid, &mp->m_sb.sb_uuid);
+			platform_uuid_copy(&agi->agi_uuid,
+					   &mp->m_sb.sb_meta_uuid);
 		for (c = 0; c < XFS_AGI_UNLINKED_BUCKETS; c++)
 			agi->agi_unlinked[c] = cpu_to_be32(NULLAGINO);
 		libxfs_writebuf(buf, LIBXFS_EXIT_ON_FAILURE);
diff --git a/repair/agheader.c b/repair/agheader.c
index 5dbf992..5200ff0 100644
--- a/repair/agheader.c
+++ b/repair/agheader.c
@@ -112,7 +112,7 @@ verify_set_agf(xfs_mount_t *mp, xfs_agf_t *agf, xfs_agnumber_t i)
 	if (!xfs_sb_version_hascrc(&mp->m_sb))
 		return retval;
 
-	if (platform_uuid_compare(&agf->agf_uuid, &mp->m_sb.sb_uuid)) {
+	if (platform_uuid_compare(&agf->agf_uuid, &mp->m_sb.sb_meta_uuid)) {
 		char uu[64];
 
 		retval = XR_AG_AGF;
@@ -120,7 +120,8 @@ verify_set_agf(xfs_mount_t *mp, xfs_agf_t *agf, xfs_agnumber_t i)
 		do_warn(_("bad uuid %s for agf %d\n"), uu, i);
 
 		if (!no_modify)
-			platform_uuid_copy(&agf->agf_uuid, &mp->m_sb.sb_uuid);
+			platform_uuid_copy(&agf->agf_uuid,
+					   &mp->m_sb.sb_meta_uuid);
 	}
 	return retval;
 }
@@ -190,7 +191,7 @@ verify_set_agi(xfs_mount_t *mp, xfs_agi_t *agi, xfs_agnumber_t agno)
 	if (!xfs_sb_version_hascrc(&mp->m_sb))
 		return retval;
 
-	if (platform_uuid_compare(&agi->agi_uuid, &mp->m_sb.sb_uuid)) {
+	if (platform_uuid_compare(&agi->agi_uuid, &mp->m_sb.sb_meta_uuid)) {
 		char uu[64];
 
 		retval = XR_AG_AGI;
@@ -198,7 +199,8 @@ verify_set_agi(xfs_mount_t *mp, xfs_agi_t *agi, xfs_agnumber_t agno)
 		do_warn(_("bad uuid %s for agi %d\n"), uu, agno);
 
 		if (!no_modify)
-			platform_uuid_copy(&agi->agi_uuid, &mp->m_sb.sb_uuid);
+			platform_uuid_copy(&agi->agi_uuid,
+					   &mp->m_sb.sb_meta_uuid);
 	}
 
 	return retval;
@@ -245,7 +247,7 @@ compare_sb(xfs_mount_t *mp, xfs_sb_t *sb)
  * superblocks, not just the secondary superblocks.
  */
 static int
-secondary_sb_wack(
+secondary_sb_whack(
 	struct xfs_mount *mp,
 	struct xfs_buf	*sbuf,
 	struct xfs_sb	*sb,
@@ -267,7 +269,10 @@ secondary_sb_wack(
 	 *
 	 * size is the size of data which is valid for this sb.
 	 */
-	if (xfs_sb_version_hascrc(sb))
+	if (xfs_sb_version_hasmetauuid(sb))
+		size = offsetof(xfs_sb_t, sb_meta_uuid)
+			+ sizeof(sb->sb_meta_uuid);
+	else if (xfs_sb_version_hascrc(sb))
 		size = offsetof(xfs_sb_t, sb_lsn)
 			+ sizeof(sb->sb_lsn);
 	else if (xfs_sb_version_hasmorebits(sb))
@@ -526,7 +531,7 @@ verify_set_agheader(xfs_mount_t *mp, xfs_buf_t *sbuf, xfs_sb_t *sb,
 		rval |= XR_AG_SB;
 	}
 
-	rval |= secondary_sb_wack(mp, sbuf, sb, i);
+	rval |= secondary_sb_whack(mp, sbuf, sb, i);
 
 	rval |= verify_set_agf(mp, agf, i);
 	rval |= verify_set_agi(mp, agi, i);
diff --git a/repair/agheader.h b/repair/agheader.h
index b5c10ec..fa6fc26 100644
--- a/repair/agheader.h
+++ b/repair/agheader.h
@@ -24,7 +24,6 @@ typedef struct fs_geometry  {
 	xfs_drfsbno_t	sb_dblocks;	/* # data blocks */
 	xfs_drfsbno_t	sb_rblocks;	/* # realtime blocks */
 	xfs_drtbno_t	sb_rextents;	/* # realtime extents */
-	uuid_t		sb_uuid;	/* fs uuid */
 	xfs_dfsbno_t	sb_logstart;	/* starting log block # */
 	xfs_agblock_t	sb_rextsize;	/* realtime extent size (blocks )*/
 	xfs_agblock_t	sb_agblocks;	/* # of blocks per ag */
diff --git a/repair/dinode.c b/repair/dinode.c
index 035212c..5d22652 100644
--- a/repair/dinode.c
+++ b/repair/dinode.c
@@ -208,9 +208,9 @@ clear_dinode_core(struct xfs_mount *mp, xfs_dinode_t *dinoc, xfs_ino_t ino_num)
 		dinoc->di_ino = cpu_to_be64(ino_num);
 	}
 
-	if (platform_uuid_compare(&dinoc->di_uuid, &mp->m_sb.sb_uuid)) {
+	if (platform_uuid_compare(&dinoc->di_uuid, &mp->m_sb.sb_meta_uuid)) {
 		__dirty_no_modify_ret(dirty);
-		platform_uuid_copy(&dinoc->di_uuid, &mp->m_sb.sb_uuid);
+		platform_uuid_copy(&dinoc->di_uuid, &mp->m_sb.sb_meta_uuid);
 	}
 
 	for (i = 0; i < sizeof(dinoc->di_pad2)/sizeof(dinoc->di_pad2[0]); i++) {
@@ -2366,7 +2366,8 @@ _("inode identifier %llu mismatch on inode %" PRIu64 "\n"),
 				return 1;
 			goto clear_bad_out;
 		}
-		if (platform_uuid_compare(&dino->di_uuid, &mp->m_sb.sb_uuid)) {
+		if (platform_uuid_compare(&dino->di_uuid,
+					  &mp->m_sb.sb_meta_uuid)) {
 			if (!uncertain)
 				do_warn(
 			_("UUID mismatch on inode %" PRIu64 "\n"), lino);
diff --git a/repair/phase5.c b/repair/phase5.c
index 3a2cdbb..d6f2ead 100644
--- a/repair/phase5.c
+++ b/repair/phase5.c
@@ -1119,7 +1119,7 @@ build_agi(xfs_mount_t *mp, xfs_agnumber_t agno, bt_status_t *btree_curs,
 		agi->agi_unlinked[i] = cpu_to_be32(NULLAGINO);
 
 	if (xfs_sb_version_hascrc(&mp->m_sb))
-		platform_uuid_copy(&agi->agi_uuid, &mp->m_sb.sb_uuid);
+		platform_uuid_copy(&agi->agi_uuid, &mp->m_sb.sb_meta_uuid);
 
 	if (xfs_sb_version_hasfinobt(&mp->m_sb)) {
 		agi->agi_free_root = cpu_to_be32(finobt_curs->root);
@@ -1360,7 +1360,7 @@ build_agf_agfl(xfs_mount_t	*mp,
 #endif
 
 	if (xfs_sb_version_hascrc(&mp->m_sb))
-		platform_uuid_copy(&agf->agf_uuid, &mp->m_sb.sb_uuid);
+		platform_uuid_copy(&agf->agf_uuid, &mp->m_sb.sb_meta_uuid);
 
 	/* initialise the AGFL, then fill it if there are blocks left over. */
 	agfl_buf = libxfs_getbuf(mp->m_dev,
@@ -1374,7 +1374,7 @@ build_agf_agfl(xfs_mount_t	*mp,
 	if (xfs_sb_version_hascrc(&mp->m_sb)) {
 		agfl->agfl_magicnum = cpu_to_be32(XFS_AGFL_MAGIC);
 		agfl->agfl_seqno = cpu_to_be32(agno);
-		platform_uuid_copy(&agfl->agfl_uuid, &mp->m_sb.sb_uuid);
+		platform_uuid_copy(&agfl->agfl_uuid, &mp->m_sb.sb_meta_uuid);
 		for (i = 0; i < XFS_AGFL_SIZE(mp); i++)
 			agfl->agfl_bno[i] = cpu_to_be32(NULLAGBLOCK);
 	}
diff --git a/repair/phase6.c b/repair/phase6.c
index c09b394..96204b9 100644
--- a/repair/phase6.c
+++ b/repair/phase6.c
@@ -526,7 +526,7 @@ mk_rbmino(xfs_mount_t *mp)
 		ip->i_d.di_flags2 = 0;
 		ip->i_d.di_ino = mp->m_sb.sb_rbmino;
 		memset(&(ip->i_d.di_pad2[0]), 0, sizeof(ip->i_d.di_pad2));
-		platform_uuid_copy(&ip->i_d.di_uuid, &mp->m_sb.sb_uuid);
+		platform_uuid_copy(&ip->i_d.di_uuid, &mp->m_sb.sb_meta_uuid);
 		times |= XFS_ICHGTIME_CREATE;
 	}
 	libxfs_trans_ichgtime(tp, ip, times);
@@ -782,7 +782,7 @@ mk_rsumino(xfs_mount_t *mp)
 		ip->i_d.di_flags2 = 0;
 		ip->i_d.di_ino = mp->m_sb.sb_rsumino;
 		memset(&(ip->i_d.di_pad2[0]), 0, sizeof(ip->i_d.di_pad2));
-		platform_uuid_copy(&ip->i_d.di_uuid, &mp->m_sb.sb_uuid);
+		platform_uuid_copy(&ip->i_d.di_uuid, &mp->m_sb.sb_meta_uuid);
 		times |= XFS_ICHGTIME_CREATE;
 	}
 	libxfs_trans_ichgtime(tp, ip, times);
@@ -898,7 +898,7 @@ mk_root_dir(xfs_mount_t *mp)
 		ip->i_d.di_flags2 = 0;
 		ip->i_d.di_ino = mp->m_sb.sb_rootino;
 		memset(&(ip->i_d.di_pad2[0]), 0, sizeof(ip->i_d.di_pad2));
-		platform_uuid_copy(&ip->i_d.di_uuid, &mp->m_sb.sb_uuid);
+		platform_uuid_copy(&ip->i_d.di_uuid, &mp->m_sb.sb_meta_uuid);
 		times |= XFS_ICHGTIME_CREATE;
 	}
 	libxfs_trans_ichgtime(tp, ip, times);


_______________________________________________
xfs mailing list
xfs@oss.sgi.com
http://oss.sgi.com/mailman/listinfo/xfs

^ permalink raw reply related	[flat|nested] 11+ messages in thread

* Re: [PATCH 2/2] xfsprogs: Add new sb_meta_uuid field, and userspace tools to manipulate it
  2015-05-08 20:59 ` [PATCH 2/2] xfsprogs: Add new sb_meta_uuid field, and userspace tools to manipulate it Eric Sandeen
@ 2015-05-08 21:14   ` Eric Sandeen
  2015-05-08 21:49   ` [PATCH 2/2 V2] " Eric Sandeen
  1 sibling, 0 replies; 11+ messages in thread
From: Eric Sandeen @ 2015-05-08 21:14 UTC (permalink / raw)
  To: Eric Sandeen, xfs-oss

Of course, just ran into a problem w/ mkfs not initializing stuff right, not sure why the first 25 xfstests were happy.

Will send V2 for userspace, split into libxfs & tools updates, and that fix.

-Eric

_______________________________________________
xfs mailing list
xfs@oss.sgi.com
http://oss.sgi.com/mailman/listinfo/xfs

^ permalink raw reply	[flat|nested] 11+ messages in thread

* [PATCH 2/2 V2] xfsprogs: Add new sb_meta_uuid field, and userspace tools to manipulate it
  2015-05-08 20:59 ` [PATCH 2/2] xfsprogs: Add new sb_meta_uuid field, and userspace tools to manipulate it Eric Sandeen
  2015-05-08 21:14   ` Eric Sandeen
@ 2015-05-08 21:49   ` Eric Sandeen
  1 sibling, 0 replies; 11+ messages in thread
From: Eric Sandeen @ 2015-05-08 21:49 UTC (permalink / raw)
  To: Eric Sandeen, xfs-oss

This adds a new superblock field, sb_meta_uuid.  This allows us to
change the use-visible UUID on crc-enabled filesytems from userspace
if desired, by copying the existing UUID to the new location for
metadata comparisons.  If this is done, an incompat flag must be
set to prevent older filesystems from mounting the filesystem, but
the original UUID can be restored, and the incompat flag removed,
with a new xfs_db / xfs_admin UUID command, "restore."

Much of this patch mirrors the kernel patch in simply renaming
the field used for metadata uuid comparison; other bits:

* Teach xfs_db to print the new meta_uuid field
* Allow xfs_db to generate a new UUID for CRC-enabled filesystems
* Allow xfs_db to revert to the original UUID and clear the flag
* Fix up xfs_copy to work with CRC-enabled filesystems
* Update the xfs_admin manpage to show the UUID "generate" command

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
---

V2: initialize meta_uuid at mkfs time, libxfs expects this to be as
if read from disk w/o the META_UUID incompat flag, and copied to
the meta_uuid field.

Breaking it into libxfs & tools is actually more intricate than I thought,
so skipping it unless really desired.  ;)

Right now xfs_db "uuid restore" squawks if called on a filesystem that
doesn't need it; perhaps that should be removed...

I'm not totally sold on the "restore" command name either; open to
suggestions.

diff --git a/copy/xfs_copy.c b/copy/xfs_copy.c
index 279527c..a58eee5 100644
--- a/copy/xfs_copy.c
+++ b/copy/xfs_copy.c
@@ -466,6 +466,34 @@ write_wbuf(void)
 	sighold(SIGCHLD);
 }
 
+void
+sb_update_uuid(
+	xfs_sb_t	*sb,
+	ag_header_t	*ag_hdr,
+	thread_args	*tcarg)
+{
+	/*
+	 * If this filesystem has CRCs, the original UUID is stamped into
+	 * all metadata.  We need to copy the original UUID into the meta_uuid
+	 * slot and set the incompat flag if that hasn't already been done.
+	 */
+	if (xfs_sb_version_hascrc(sb) && !xfs_sb_version_hasmetauuid(sb)) {
+		__be32 feat;
+
+		feat = be32_to_cpu(ag_hdr->xfs_sb->sb_features_incompat);
+		feat |= XFS_SB_FEAT_INCOMPAT_META_UUID;
+		ag_hdr->xfs_sb->sb_features_incompat = cpu_to_be32(feat);
+		platform_uuid_copy(&ag_hdr->xfs_sb->sb_meta_uuid,
+				   &ag_hdr->xfs_sb->sb_uuid);
+	}
+
+	platform_uuid_copy(&ag_hdr->xfs_sb->sb_uuid, &tcarg->uuid);
+
+	/* We changed the UUID, so update the superblock CRC if needed */
+	if (xfs_sb_version_hascrc(sb))
+		xfs_update_cksum((char *)&ag_hdr->xfs_sb, sb->sb_sectsize,
+							 XFS_SB_CRC_OFF);
+}
 
 int
 main(int argc, char **argv)
@@ -659,16 +687,6 @@ main(int argc, char **argv)
 	sb = &mbuf.m_sb;
 	libxfs_sb_from_disk(sb, XFS_BUF_TO_SBP(sbp));
 
-	/*
-	 * For now, V5 superblock filesystems are not supported without -d;
-	 * we do not have the infrastructure yet to fix CRCs when a new UUID
-	 * is generated.
-	 */
-	if (xfs_sb_version_hascrc(sb) && !duplicate) {
-		do_log(_("%s: Cannot yet copy V5 fs without '-d'\n"), progname);
-		exit(1);
-	}
-
 	mp = libxfs_mount(&mbuf, sb, xargs.ddev, xargs.logdev, xargs.rtdev, 0);
 	if (mp == NULL) {
 		do_log(_("%s: %s filesystem failed to initialize\n"
@@ -1127,8 +1145,7 @@ main(int argc, char **argv)
 			/* do each thread in turn, each has its own UUID */
 
 			for (j = 0, tcarg = targ; j < num_targets; j++)  {
-				platform_uuid_copy(&ag_hdr.xfs_sb->sb_uuid,
-							&tcarg->uuid);
+				sb_update_uuid(sb, &ag_hdr, tcarg);
 				do_write(tcarg);
 				tcarg++;
 			}
diff --git a/db/sb.c b/db/sb.c
index 23ec87c..6b5bab0 100644
--- a/db/sb.c
+++ b/db/sb.c
@@ -29,6 +29,8 @@
 #include "output.h"
 #include "init.h"
 
+#define uuid_equal(s,d)		(platform_uuid_compare((s),(d)) == 0)
+
 static int	sb_f(int argc, char **argv);
 static void     sb_help(void);
 static int	uuid_f(int argc, char **argv);
@@ -121,6 +123,7 @@ const field_t	sb_flds[] = {
 	{ "crc", FLDT_CRC, OI(OFF(crc)), C1, 0, TYP_NONE },
 	{ "pquotino", FLDT_INO, OI(OFF(pquotino)), C1, 0, TYP_INODE },
 	{ "lsn", FLDT_UINT64X, OI(OFF(lsn)), C1, 0, TYP_NONE },
+	{ "meta_uuid", FLDT_UUID, OI(OFF(meta_uuid)), C1, 0, TYP_NONE },
 	{ NULL }
 };
 
@@ -324,6 +327,7 @@ do_uuid(xfs_agnumber_t agno, uuid_t *uuid)
 {
 	xfs_sb_t	tsb;
 	static uuid_t	uu;
+	__int64_t	fields = XFS_SB_UUID;
 
 	if (!get_sb(agno, &tsb))
 		return NULL;
@@ -333,9 +337,38 @@ do_uuid(xfs_agnumber_t agno, uuid_t *uuid)
 		pop_cur();
 		return &uu;
 	}
+
 	/* set uuid */
+	if (!xfs_sb_version_hascrc(&tsb))
+		goto write;
+	/*
+	 * If we have CRCs, and this UUID differs from that stamped in the
+	 * metadata, set the incompat flag and copy the old one to the
+	 * metadata-specific location.
+	 *
+	 * If we are setting the user-visible UUID back to match the metadata
+	 * UUID, clear the metadata-specific location and the incompat flag.
+	 */
+	if (!xfs_sb_version_hasmetauuid(&tsb) &&
+	    !uuid_equal(uuid, &mp->m_sb.sb_meta_uuid)) {
+		mp->m_sb.sb_features_incompat |= XFS_SB_FEAT_INCOMPAT_META_UUID;
+		tsb.sb_features_incompat |= XFS_SB_FEAT_INCOMPAT_META_UUID;
+		memcpy(&tsb.sb_meta_uuid, &tsb.sb_uuid, sizeof(uuid_t));
+		fields |= XFS_SB_META_UUID | XFS_SB_FEATURES_INCOMPAT;
+	} else if (xfs_sb_version_hasmetauuid(&tsb) &&
+		   uuid_equal(uuid, &mp->m_sb.sb_meta_uuid)) {
+		memset(&tsb.sb_meta_uuid, 0, sizeof(uuid_t));
+		/* Write those zeros now; it's ignored once we clear the flag */
+		libxfs_sb_to_disk(iocur_top->data, &tsb, XFS_SB_META_UUID);
+		mp->m_sb.sb_features_incompat &=
+						~XFS_SB_FEAT_INCOMPAT_META_UUID;
+		tsb.sb_features_incompat &= ~XFS_SB_FEAT_INCOMPAT_META_UUID;
+		fields |= XFS_SB_FEATURES_INCOMPAT;
+	}
+
+write:
 	memcpy(&tsb.sb_uuid, uuid, sizeof(uuid_t));
-	libxfs_sb_to_disk(iocur_top->data, &tsb, XFS_SB_UUID);
+	libxfs_sb_to_disk(iocur_top->data, &tsb, fields);
 	write_cur();
 	return uuid;
 }
@@ -363,18 +396,6 @@ uuid_f(
 			return 0;
 		}
 
-		/*
-		 * For now, changing the UUID of V5 superblock filesystems is
-		 * not supported; we do not have the infrastructure to fix all
-		 * other metadata when a new superblock UUID is generated.
-		 */
-		if (xfs_sb_version_hascrc(&mp->m_sb) &&
-		    strcasecmp(argv[1], "rewrite")) {
-			dbprintf(_("%s: only 'rewrite' supported on V5 fs\n"),
-				progname);
-			return 0;
-		}
-
 		if (!strcasecmp(argv[1], "generate")) {
 			platform_uuid_generate(&uu);
 		} else if (!strcasecmp(argv[1], "nil")) {
@@ -388,6 +409,16 @@ uuid_f(
 			memcpy(&uu, uup, sizeof(uuid_t));
 			platform_uuid_unparse(&uu, bp);
 			dbprintf(_("old UUID = %s\n"), bp);
+		} else if (!strcasecmp(argv[1], "restore")) {
+			xfs_sb_t	tsb;
+
+			if (!get_sb(0, &tsb))
+				return 0;
+			if (!xfs_sb_version_hasmetauuid(&tsb)) {
+				dbprintf(_("META_UUID not set"));
+				return 0;
+			}
+			memcpy(&uu, mp->m_sb.sb_meta_uuid, sizeof(uuid_t));
 		} else {
 			if (platform_uuid_parse(argv[1], &uu)) {
 				dbprintf(_("invalid UUID\n"));
@@ -658,6 +689,8 @@ version_string(
 		strcat(s, ",CRC");
 	if (xfs_sb_version_hasftype(sbp))
 		strcat(s, ",FTYPE");
+	if (xfs_sb_version_hasmetauuid(sbp))
+		strcat(s, ",META_UUID");
 	return s;
 }
 
diff --git a/libxfs/xfs_sb.c b/libxfs/xfs_sb.c
index c9ef019..ea30857 100644
--- a/libxfs/xfs_sb.c
+++ b/libxfs/xfs_sb.c
@@ -503,7 +503,7 @@ xfs_sb_to_disk(
 	 * in memory; don't write it out.
 	 */
 	if (!xfs_sb_version_hasmetauuid(from))
-		fields &= ~XFS_SB_UUID;
+		fields &= ~XFS_SB_META_UUID;
 
 	xfs_sb_quota_to_disk(to, from, &fields);
 	while (fields) {
diff --git a/libxlog/util.c b/libxlog/util.c
index 949b79d..652d391 100644
--- a/libxlog/util.c
+++ b/libxlog/util.c
@@ -28,8 +28,10 @@ header_check_uuid(xfs_mount_t *mp, xlog_rec_header_t *head)
 {
     char uu_log[64], uu_sb[64];
 
-    if (print_skip_uuid) return 0;
-    if (!platform_uuid_compare(&mp->m_sb.sb_uuid, &head->h_fs_uuid)) return 0;
+    if (print_skip_uuid)
+		return 0;
+    if (!platform_uuid_compare(&mp->m_sb.sb_uuid, &head->h_fs_uuid))
+		return 0;
 
     platform_uuid_unparse(&mp->m_sb.sb_uuid, uu_sb);
     platform_uuid_unparse(&head->h_fs_uuid, uu_log);
diff --git a/man/man8/xfs_admin.8 b/man/man8/xfs_admin.8
index b393d74..0600540 100644
--- a/man/man8/xfs_admin.8
+++ b/man/man8/xfs_admin.8
@@ -98,7 +98,12 @@ The
 .I uuid
 may also be
 .BR generate ,
-which will generate a new UUID for the filesystem.
+which will generate a new UUID for the filesystem.  Note that on CRC-enabled
+filesystems, this will set an incompatible flag such that older kernels will
+not be able to mount the filesystem.  To remove this incompatible flag, use
+.BR restore ,
+which will match the UUID to the metadata UUID and remove the incompatible
+feature flag.
 .TP
 .B \-V
 Prints the version number and exits.
diff --git a/man/man8/xfs_db.8 b/man/man8/xfs_db.8
index d527230..7c471aa 100644
--- a/man/man8/xfs_db.8
+++ b/man/man8/xfs_db.8
@@ -664,7 +664,7 @@ The possible data types are:
 .BR sb ", " symlink " and " text .
 See the TYPES section below for more information on these data types.
 .TP
-.BI "uuid [" uuid " | " generate " | " rewrite ]
+.BI "uuid [" uuid " | " generate " | " rewrite " | " restore ]
 Set the filesystem universally unique identifier (UUID).
 The filesystem UUID can be used by
 .BR mount (8)
@@ -675,7 +675,12 @@ can be set directly to the desired UUID, or it can
 be automatically generated using the
 .B generate
 option. These options will both write the UUID into every copy of the
-superblock in the filesystem.
+superblock in the filesystem.  On a CRC-enabled filesystem, this will
+set an incompatible superblock flag, and the filesystem will not be
+mountable with older kernels.  This can be reverted with the
+.B restore
+option, which will copy the original UUID back into place, and clear
+the incompatible flag.
 .B rewrite
 copies the current UUID from the primary superblock
 to all secondary copies of the superblock.
diff --git a/mkfs/xfs_mkfs.c b/mkfs/xfs_mkfs.c
index 5084d75..eb8b74d 100644
--- a/mkfs/xfs_mkfs.c
+++ b/mkfs/xfs_mkfs.c
@@ -2598,6 +2598,8 @@ _("size %s specified for log subvolume is too large, maximum is %lld blocks\n"),
 	sbp->sb_rextents = rtextents;
 	platform_uuid_generate(&uuid);
 	platform_uuid_copy(&sbp->sb_uuid, &uuid);
+	/* Only in memory; libxfs expects this */
+	platform_uuid_copy(&sbp->sb_meta_uuid, &uuid);
 	sbp->sb_logstart = logstart;
 	sbp->sb_rootino = sbp->sb_rbmino = sbp->sb_rsumino = NULLFSINO;
 	sbp->sb_rextsize = rtextblocks;
diff --git a/repair/agheader.c b/repair/agheader.c
index 5dbf992..5200ff0 100644
--- a/repair/agheader.c
+++ b/repair/agheader.c
@@ -112,7 +112,7 @@ verify_set_agf(xfs_mount_t *mp, xfs_agf_t *agf, xfs_agnumber_t i)
 	if (!xfs_sb_version_hascrc(&mp->m_sb))
 		return retval;
 
-	if (platform_uuid_compare(&agf->agf_uuid, &mp->m_sb.sb_uuid)) {
+	if (platform_uuid_compare(&agf->agf_uuid, &mp->m_sb.sb_meta_uuid)) {
 		char uu[64];
 
 		retval = XR_AG_AGF;
@@ -120,7 +120,8 @@ verify_set_agf(xfs_mount_t *mp, xfs_agf_t *agf, xfs_agnumber_t i)
 		do_warn(_("bad uuid %s for agf %d\n"), uu, i);
 
 		if (!no_modify)
-			platform_uuid_copy(&agf->agf_uuid, &mp->m_sb.sb_uuid);
+			platform_uuid_copy(&agf->agf_uuid,
+					   &mp->m_sb.sb_meta_uuid);
 	}
 	return retval;
 }
@@ -190,7 +191,7 @@ verify_set_agi(xfs_mount_t *mp, xfs_agi_t *agi, xfs_agnumber_t agno)
 	if (!xfs_sb_version_hascrc(&mp->m_sb))
 		return retval;
 
-	if (platform_uuid_compare(&agi->agi_uuid, &mp->m_sb.sb_uuid)) {
+	if (platform_uuid_compare(&agi->agi_uuid, &mp->m_sb.sb_meta_uuid)) {
 		char uu[64];
 
 		retval = XR_AG_AGI;
@@ -198,7 +199,8 @@ verify_set_agi(xfs_mount_t *mp, xfs_agi_t *agi, xfs_agnumber_t agno)
 		do_warn(_("bad uuid %s for agi %d\n"), uu, agno);
 
 		if (!no_modify)
-			platform_uuid_copy(&agi->agi_uuid, &mp->m_sb.sb_uuid);
+			platform_uuid_copy(&agi->agi_uuid,
+					   &mp->m_sb.sb_meta_uuid);
 	}
 
 	return retval;
@@ -245,7 +247,7 @@ compare_sb(xfs_mount_t *mp, xfs_sb_t *sb)
  * superblocks, not just the secondary superblocks.
  */
 static int
-secondary_sb_wack(
+secondary_sb_whack(
 	struct xfs_mount *mp,
 	struct xfs_buf	*sbuf,
 	struct xfs_sb	*sb,
@@ -267,7 +269,10 @@ secondary_sb_wack(
 	 *
 	 * size is the size of data which is valid for this sb.
 	 */
-	if (xfs_sb_version_hascrc(sb))
+	if (xfs_sb_version_hasmetauuid(sb))
+		size = offsetof(xfs_sb_t, sb_meta_uuid)
+			+ sizeof(sb->sb_meta_uuid);
+	else if (xfs_sb_version_hascrc(sb))
 		size = offsetof(xfs_sb_t, sb_lsn)
 			+ sizeof(sb->sb_lsn);
 	else if (xfs_sb_version_hasmorebits(sb))
@@ -526,7 +531,7 @@ verify_set_agheader(xfs_mount_t *mp, xfs_buf_t *sbuf, xfs_sb_t *sb,
 		rval |= XR_AG_SB;
 	}
 
-	rval |= secondary_sb_wack(mp, sbuf, sb, i);
+	rval |= secondary_sb_whack(mp, sbuf, sb, i);
 
 	rval |= verify_set_agf(mp, agf, i);
 	rval |= verify_set_agi(mp, agi, i);
diff --git a/repair/agheader.h b/repair/agheader.h
index b5c10ec..fa6fc26 100644
--- a/repair/agheader.h
+++ b/repair/agheader.h
@@ -24,7 +24,6 @@ typedef struct fs_geometry  {
 	xfs_drfsbno_t	sb_dblocks;	/* # data blocks */
 	xfs_drfsbno_t	sb_rblocks;	/* # realtime blocks */
 	xfs_drtbno_t	sb_rextents;	/* # realtime extents */
-	uuid_t		sb_uuid;	/* fs uuid */
 	xfs_dfsbno_t	sb_logstart;	/* starting log block # */
 	xfs_agblock_t	sb_rextsize;	/* realtime extent size (blocks )*/
 	xfs_agblock_t	sb_agblocks;	/* # of blocks per ag */
diff --git a/repair/dinode.c b/repair/dinode.c
index 035212c..5d22652 100644
--- a/repair/dinode.c
+++ b/repair/dinode.c
@@ -208,9 +208,9 @@ clear_dinode_core(struct xfs_mount *mp, xfs_dinode_t *dinoc, xfs_ino_t ino_num)
 		dinoc->di_ino = cpu_to_be64(ino_num);
 	}
 
-	if (platform_uuid_compare(&dinoc->di_uuid, &mp->m_sb.sb_uuid)) {
+	if (platform_uuid_compare(&dinoc->di_uuid, &mp->m_sb.sb_meta_uuid)) {
 		__dirty_no_modify_ret(dirty);
-		platform_uuid_copy(&dinoc->di_uuid, &mp->m_sb.sb_uuid);
+		platform_uuid_copy(&dinoc->di_uuid, &mp->m_sb.sb_meta_uuid);
 	}
 
 	for (i = 0; i < sizeof(dinoc->di_pad2)/sizeof(dinoc->di_pad2[0]); i++) {
@@ -2366,7 +2366,8 @@ _("inode identifier %llu mismatch on inode %" PRIu64 "\n"),
 				return 1;
 			goto clear_bad_out;
 		}
-		if (platform_uuid_compare(&dino->di_uuid, &mp->m_sb.sb_uuid)) {
+		if (platform_uuid_compare(&dino->di_uuid,
+					  &mp->m_sb.sb_meta_uuid)) {
 			if (!uncertain)
 				do_warn(
 			_("UUID mismatch on inode %" PRIu64 "\n"), lino);
diff --git a/repair/phase5.c b/repair/phase5.c
index 3a2cdbb..d6f2ead 100644
--- a/repair/phase5.c
+++ b/repair/phase5.c
@@ -1119,7 +1119,7 @@ build_agi(xfs_mount_t *mp, xfs_agnumber_t agno, bt_status_t *btree_curs,
 		agi->agi_unlinked[i] = cpu_to_be32(NULLAGINO);
 
 	if (xfs_sb_version_hascrc(&mp->m_sb))
-		platform_uuid_copy(&agi->agi_uuid, &mp->m_sb.sb_uuid);
+		platform_uuid_copy(&agi->agi_uuid, &mp->m_sb.sb_meta_uuid);
 
 	if (xfs_sb_version_hasfinobt(&mp->m_sb)) {
 		agi->agi_free_root = cpu_to_be32(finobt_curs->root);
@@ -1360,7 +1360,7 @@ build_agf_agfl(xfs_mount_t	*mp,
 #endif
 
 	if (xfs_sb_version_hascrc(&mp->m_sb))
-		platform_uuid_copy(&agf->agf_uuid, &mp->m_sb.sb_uuid);
+		platform_uuid_copy(&agf->agf_uuid, &mp->m_sb.sb_meta_uuid);
 
 	/* initialise the AGFL, then fill it if there are blocks left over. */
 	agfl_buf = libxfs_getbuf(mp->m_dev,
@@ -1374,7 +1374,7 @@ build_agf_agfl(xfs_mount_t	*mp,
 	if (xfs_sb_version_hascrc(&mp->m_sb)) {
 		agfl->agfl_magicnum = cpu_to_be32(XFS_AGFL_MAGIC);
 		agfl->agfl_seqno = cpu_to_be32(agno);
-		platform_uuid_copy(&agfl->agfl_uuid, &mp->m_sb.sb_uuid);
+		platform_uuid_copy(&agfl->agfl_uuid, &mp->m_sb.sb_meta_uuid);
 		for (i = 0; i < XFS_AGFL_SIZE(mp); i++)
 			agfl->agfl_bno[i] = cpu_to_be32(NULLAGBLOCK);
 	}
diff --git a/repair/phase6.c b/repair/phase6.c
index c09b394..96204b9 100644
--- a/repair/phase6.c
+++ b/repair/phase6.c
@@ -526,7 +526,7 @@ mk_rbmino(xfs_mount_t *mp)
 		ip->i_d.di_flags2 = 0;
 		ip->i_d.di_ino = mp->m_sb.sb_rbmino;
 		memset(&(ip->i_d.di_pad2[0]), 0, sizeof(ip->i_d.di_pad2));
-		platform_uuid_copy(&ip->i_d.di_uuid, &mp->m_sb.sb_uuid);
+		platform_uuid_copy(&ip->i_d.di_uuid, &mp->m_sb.sb_meta_uuid);
 		times |= XFS_ICHGTIME_CREATE;
 	}
 	libxfs_trans_ichgtime(tp, ip, times);
@@ -782,7 +782,7 @@ mk_rsumino(xfs_mount_t *mp)
 		ip->i_d.di_flags2 = 0;
 		ip->i_d.di_ino = mp->m_sb.sb_rsumino;
 		memset(&(ip->i_d.di_pad2[0]), 0, sizeof(ip->i_d.di_pad2));
-		platform_uuid_copy(&ip->i_d.di_uuid, &mp->m_sb.sb_uuid);
+		platform_uuid_copy(&ip->i_d.di_uuid, &mp->m_sb.sb_meta_uuid);
 		times |= XFS_ICHGTIME_CREATE;
 	}
 	libxfs_trans_ichgtime(tp, ip, times);
@@ -898,7 +898,7 @@ mk_root_dir(xfs_mount_t *mp)
 		ip->i_d.di_flags2 = 0;
 		ip->i_d.di_ino = mp->m_sb.sb_rootino;
 		memset(&(ip->i_d.di_pad2[0]), 0, sizeof(ip->i_d.di_pad2));
-		platform_uuid_copy(&ip->i_d.di_uuid, &mp->m_sb.sb_uuid);
+		platform_uuid_copy(&ip->i_d.di_uuid, &mp->m_sb.sb_meta_uuid);
 		times |= XFS_ICHGTIME_CREATE;
 	}
 	libxfs_trans_ichgtime(tp, ip, times);


diff --git a/include/xfs_sb.h b/include/xfs_sb.h
index 950d1ea..c27c294 100644
--- a/include/xfs_sb.h
+++ b/include/xfs_sb.h
@@ -107,7 +107,7 @@ typedef struct xfs_sb {
 	xfs_drfsbno_t	sb_dblocks;	/* number of data blocks */
 	xfs_drfsbno_t	sb_rblocks;	/* number of realtime blocks */
 	xfs_drtbno_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_dfsbno_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 */
@@ -178,6 +178,7 @@ typedef struct xfs_sb {
 
 	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;
@@ -194,7 +195,7 @@ typedef struct xfs_dsb {
 	__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 */
@@ -264,6 +265,7 @@ typedef struct xfs_dsb {
 
 	__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;
@@ -287,7 +289,7 @@ typedef enum {
 	XFS_SBS_FEATURES2, XFS_SBS_BAD_FEATURES2, XFS_SBS_FEATURES_COMPAT,
 	XFS_SBS_FEATURES_RO_COMPAT, XFS_SBS_FEATURES_INCOMPAT,
 	XFS_SBS_FEATURES_LOG_INCOMPAT, XFS_SBS_CRC, XFS_SBS_PAD,
-	XFS_SBS_PQUOTINO, XFS_SBS_LSN,
+	XFS_SBS_PQUOTINO, XFS_SBS_LSN, XFS_SBS_META_UUID,
 	XFS_SBS_FIELDCOUNT
 } xfs_sb_field_t;
 
@@ -319,6 +321,7 @@ typedef enum {
 #define XFS_SB_FEATURES_LOG_INCOMPAT XFS_SB_MVAL(FEATURES_LOG_INCOMPAT)
 #define XFS_SB_CRC		XFS_SB_MVAL(CRC)
 #define XFS_SB_PQUOTINO		XFS_SB_MVAL(PQUOTINO)
+#define	XFS_SB_META_UUID	XFS_SB_MVAL(META_UUID)
 #define	XFS_SB_NUM_BITS		((int)XFS_SBS_FIELDCOUNT)
 #define	XFS_SB_ALL_BITS		((1LL << XFS_SB_NUM_BITS) - 1)
 #define	XFS_SB_MOD_BITS		\
@@ -328,7 +331,7 @@ typedef enum {
 	 XFS_SB_ICOUNT | XFS_SB_IFREE | XFS_SB_FDBLOCKS | XFS_SB_FEATURES2 | \
 	 XFS_SB_BAD_FEATURES2 | XFS_SB_FEATURES_COMPAT | \
 	 XFS_SB_FEATURES_RO_COMPAT | XFS_SB_FEATURES_INCOMPAT | \
-	 XFS_SB_FEATURES_LOG_INCOMPAT | XFS_SB_PQUOTINO)
+	 XFS_SB_FEATURES_LOG_INCOMPAT | XFS_SB_PQUOTINO | XFS_SB_META_UUID)
 
 
 /*
@@ -600,8 +603,10 @@ xfs_sb_has_ro_compat_feature(
 }
 
 #define XFS_SB_FEAT_INCOMPAT_FTYPE	(1 << 0)	/* filetype in dirent */
+#define XFS_SB_FEAT_INCOMPAT_META_UUID (1 << 1)		/* metadata UUID */
 #define XFS_SB_FEAT_INCOMPAT_ALL \
-		(XFS_SB_FEAT_INCOMPAT_FTYPE)
+		(XFS_SB_FEAT_INCOMPAT_FTYPE | \
+		 XFS_SB_FEAT_INCOMPAT_META_UUID)
 
 #define XFS_SB_FEAT_INCOMPAT_UNKNOWN	~XFS_SB_FEAT_INCOMPAT_ALL
 static inline bool
@@ -650,6 +655,18 @@ static inline int xfs_sb_version_hasfinobt(xfs_sb_t *sbp)
 }
 
 /*
+ * 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 int xfs_sb_version_hasmetauuid(xfs_sb_t *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
  */
 
diff --git a/libxfs/util.c b/libxfs/util.c
index 49eb76d..ea698c4 100644
--- a/libxfs/util.c
+++ b/libxfs/util.c
@@ -250,7 +250,7 @@ libxfs_ialloc(
 
 	if (ip->i_d.di_version == 3) {
 		ASSERT(ip->i_d.di_ino == ino);
-		ASSERT(uuid_equal(&ip->i_d.di_uuid, &mp->m_sb.sb_uuid));
+		ASSERT(uuid_equal(&ip->i_d.di_uuid, &mp->m_sb.sb_meta_uuid));
 		ip->i_d.di_crc = 0;
 		ip->i_d.di_changecount = 1;
 		ip->i_d.di_lsn = 0;
diff --git a/libxfs/xfs_alloc.c b/libxfs/xfs_alloc.c
index 6c82be0..06757c3 100644
--- a/libxfs/xfs_alloc.c
+++ b/libxfs/xfs_alloc.c
@@ -426,7 +426,7 @@ xfs_agfl_verify(
 	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;
@@ -2181,7 +2181,7 @@ xfs_agf_verify(
 	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) &&
diff --git a/libxfs/xfs_alloc_btree.c b/libxfs/xfs_alloc_btree.c
index 215be7e..cefa18b 100644
--- a/libxfs/xfs_alloc_btree.c
+++ b/libxfs/xfs_alloc_btree.c
@@ -279,7 +279,7 @@ xfs_allocbt_verify(
 	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;
@@ -297,7 +297,7 @@ xfs_allocbt_verify(
 	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;
diff --git a/libxfs/xfs_attr_leaf.c b/libxfs/xfs_attr_leaf.c
index f7f02ae..e9f96ec 100644
--- a/libxfs/xfs_attr_leaf.c
+++ b/libxfs/xfs_attr_leaf.c
@@ -161,7 +161,7 @@ xfs_attr3_leaf_verify(
 		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;
@@ -952,7 +952,7 @@ xfs_attr3_leaf_create(
 
 		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 {
diff --git a/libxfs/xfs_attr_remote.c b/libxfs/xfs_attr_remote.c
index 08b983b..62abaec 100644
--- a/libxfs/xfs_attr_remote.c
+++ b/libxfs/xfs_attr_remote.c
@@ -78,7 +78,7 @@ xfs_attr3_rmt_verify(
 		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;
@@ -194,7 +194,7 @@ xfs_attr3_rmt_hdr_set(
 	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);
 
diff --git a/libxfs/xfs_bmap_btree.c b/libxfs/xfs_bmap_btree.c
index a4bd69d..9913958 100644
--- a/libxfs/xfs_bmap_btree.c
+++ b/libxfs/xfs_bmap_btree.c
@@ -412,7 +412,8 @@ xfs_bmbt_to_bmdr(
 
 	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
@@ -712,7 +713,7 @@ xfs_bmbt_verify(
 	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;
diff --git a/libxfs/xfs_btree.c b/libxfs/xfs_btree.c
index cc823f5..a8436f5 100644
--- a/libxfs/xfs_btree.c
+++ b/libxfs/xfs_btree.c
@@ -50,7 +50,8 @@ xfs_btree_check_lblock(
 
 	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);
 	}
@@ -100,7 +101,8 @@ xfs_btree_check_sblock(
 
 	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);
 	}
@@ -992,7 +994,7 @@ xfs_btree_init_block_int(
 		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;
 		}
@@ -1005,7 +1007,7 @@ xfs_btree_init_block_int(
 		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;
 		}
 	}
diff --git a/libxfs/xfs_da_btree.c b/libxfs/xfs_da_btree.c
index b731b54..0323dc7 100644
--- a/libxfs/xfs_da_btree.c
+++ b/libxfs/xfs_da_btree.c
@@ -172,7 +172,7 @@ xfs_da3_node_verify(
 		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;
@@ -349,7 +349,7 @@ xfs_da3_node_create(
 		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;
 	}
diff --git a/libxfs/xfs_dir2_block.c b/libxfs/xfs_dir2_block.c
index cede01f..2a25059 100644
--- a/libxfs/xfs_dir2_block.c
+++ b/libxfs/xfs_dir2_block.c
@@ -51,7 +51,7 @@ xfs_dir3_block_verify(
 	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;
@@ -141,7 +141,7 @@ xfs_dir3_block_init(
 		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;
 
 	}
diff --git a/libxfs/xfs_dir2_data.c b/libxfs/xfs_dir2_data.c
index dc9df4d..4c79d7c 100644
--- a/libxfs/xfs_dir2_data.c
+++ b/libxfs/xfs_dir2_data.c
@@ -186,7 +186,7 @@ xfs_dir3_data_verify(
 	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;
@@ -573,7 +573,7 @@ xfs_dir3_data_init(
 		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);
diff --git a/libxfs/xfs_dir2_leaf.c b/libxfs/xfs_dir2_leaf.c
index 8e0cbc9..a918e15 100644
--- a/libxfs/xfs_dir2_leaf.c
+++ b/libxfs/xfs_dir2_leaf.c
@@ -186,7 +186,7 @@ xfs_dir3_leaf_verify(
 
 		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;
@@ -337,7 +337,7 @@ xfs_dir3_leaf_init(
 					 : 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);
diff --git a/libxfs/xfs_dir2_node.c b/libxfs/xfs_dir2_node.c
index 3737e4e..309e7ce 100644
--- a/libxfs/xfs_dir2_node.c
+++ b/libxfs/xfs_dir2_node.c
@@ -78,7 +78,7 @@ xfs_dir3_free_verify(
 
 		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;
@@ -257,7 +257,7 @@ xfs_dir3_free_get_buf(
 
 		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;
 	xfs_dir3_free_hdr_to_disk(bp->b_addr, &hdr);
diff --git a/libxfs/xfs_dquot_buf.c b/libxfs/xfs_dquot_buf.c
index e089ec8..f75bfe3 100644
--- a/libxfs/xfs_dquot_buf.c
+++ b/libxfs/xfs_dquot_buf.c
@@ -146,7 +146,7 @@ xfs_dqcheck(
 	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);
 	}
@@ -181,7 +181,7 @@ xfs_dquot_buf_verify_crc(
 		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;
diff --git a/libxfs/xfs_ialloc.c b/libxfs/xfs_ialloc.c
index b20a9ec..ae0804c 100644
--- a/libxfs/xfs_ialloc.c
+++ b/libxfs/xfs_ialloc.c
@@ -295,7 +295,8 @@ xfs_ialloc_inode_init(
 			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 */
@@ -1947,7 +1948,7 @@ xfs_agi_verify(
 	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.
diff --git a/libxfs/xfs_ialloc_btree.c b/libxfs/xfs_ialloc_btree.c
index c337389..320984f 100644
--- a/libxfs/xfs_ialloc_btree.c
+++ b/libxfs/xfs_ialloc_btree.c
@@ -214,7 +214,7 @@ xfs_inobt_verify(
 	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;
diff --git a/libxfs/xfs_inode_buf.c b/libxfs/xfs_inode_buf.c
index de16ed9..1c0047d 100644
--- a/libxfs/xfs_inode_buf.c
+++ b/libxfs/xfs_inode_buf.c
@@ -295,7 +295,7 @@ xfs_dinode_verify(
 		return false;
 	if (be64_to_cpu(dip->di_ino) != 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;
 }
diff --git a/libxfs/xfs_sb.c b/libxfs/xfs_sb.c
index ea89367..c9ef019 100644
--- a/libxfs/xfs_sb.c
+++ b/libxfs/xfs_sb.c
@@ -81,6 +81,7 @@ static const struct {
 	{ offsetof(xfs_sb_t, sb_pad),		0 },
 	{ offsetof(xfs_sb_t, sb_pquotino),	0 },
 	{ offsetof(xfs_sb_t, sb_lsn),		0 },
+	{ offsetof(xfs_sb_t, sb_meta_uuid),		1 },
 	{ sizeof(xfs_sb_t),			0 }
 };
 
@@ -413,6 +414,13 @@ xfs_sb_from_disk(
 	to->sb_pad = 0;
 	to->sb_pquotino = be64_to_cpu(from->sb_pquotino);
 	to->sb_lsn = be64_to_cpu(from->sb_lsn);
+	if (xfs_sb_version_hasmetauuid(to)) {
+		memcpy(&to->sb_meta_uuid, &from->sb_meta_uuid,
+					sizeof(to->sb_meta_uuid));
+	} else {
+		memcpy(&to->sb_meta_uuid, &from->sb_uuid,
+					sizeof(to->sb_meta_uuid));
+	}
 }
 
 static inline void
@@ -490,6 +498,13 @@ xfs_sb_to_disk(
 	/* We should never write the crc here, it's updated in the IO path */
 	fields &= ~XFS_SB_CRC;
 
+	/*
+	 * If the metadata-specific UUID feature isn't set, it's only set
+	 * in memory; don't write it out.
+	 */
+	if (!xfs_sb_version_hasmetauuid(from))
+		fields &= ~XFS_SB_UUID;
+
 	xfs_sb_quota_to_disk(to, from, &fields);
 	while (fields) {
 		f = (xfs_sb_field_t)xfs_lowbit64((__uint64_t)fields);
diff --git a/libxfs/xfs_symlink_remote.c b/libxfs/xfs_symlink_remote.c
index ebf60ac..3f8374e 100644
--- a/libxfs/xfs_symlink_remote.c
+++ b/libxfs/xfs_symlink_remote.c
@@ -48,7 +48,7 @@ xfs_symlink_hdr_set(
 	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;
@@ -93,7 +93,7 @@ xfs_symlink_verify(
 		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;


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^ permalink raw reply related	[flat|nested] 11+ messages in thread

* Re: [PATCH 1/2] xfs: create new metadata UUID field and incompat flag
  2015-05-08 20:48 ` [PATCH 1/2] xfs: create new metadata UUID field and incompat flag Eric Sandeen
@ 2015-05-11 16:14   ` Brian Foster
  2015-05-11 16:52     ` Eric Sandeen
  0 siblings, 1 reply; 11+ messages in thread
From: Brian Foster @ 2015-05-11 16:14 UTC (permalink / raw)
  To: Eric Sandeen; +Cc: Eric Sandeen, xfs-oss

On Fri, May 08, 2015 at 03:48:16PM -0500, Eric Sandeen wrote:
> 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 or clearing
> of the incompat flag as appropriate, as the UUID gets written.
> 
> If the incompat flag is not set, copy the user-visible UUID into
> into the meta_uuid slot in memory; this 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>
> ---

This all looks fine to me. The only thing that confuses me is why we
continue to use sb_uuid for the log. Eric points out on irc that we
can't modify the uuid when the log is dirty, so we can't actually break
anything in this manner. In other words, we effectively already handle a
modified uuid with respect to the log.

That said, it seems inconsistent to me to create a metadata uuid field
and not use it for all metadata. My expectation from such a change is to
see sb_uuid now used only for user facing bits (e.g., mount and get geo
related) and sb_meta_uuid used everywhere else. Instead, we use sb_uuid
for the user facing bits, sb_meta_uuid for the internal bits that can't
handle a uuid change and sb_uuid for the internal bits that can.

I suppose I could be convinced otherwise if there's context I'm missing,
but otherwise this seems a bit confusing to me...

Brian

> 
> diff --git a/fs/xfs/libxfs/xfs_format.h b/fs/xfs/libxfs/xfs_format.h
> index 4daaa66..88c38df 100644
> --- a/fs/xfs/libxfs/xfs_format.h
> +++ b/fs/xfs/libxfs/xfs_format.h
> @@ -100,7 +100,7 @@ typedef struct xfs_sb {
>  	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 @@ typedef struct xfs_sb {
>  
>  	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 @@ typedef struct xfs_dsb {
>  	__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 @@ typedef struct xfs_dsb {
>  
>  	__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;
> @@ -457,8 +459,10 @@ xfs_sb_has_ro_compat_feature(
>  }
>  
>  #define XFS_SB_FEAT_INCOMPAT_FTYPE	(1 << 0)	/* filetype in dirent */
> +#define XFS_SB_FEAT_INCOMPAT_META_UUID	(1 << 1)	/* metadata UUID */
>  #define XFS_SB_FEAT_INCOMPAT_ALL \
> -		(XFS_SB_FEAT_INCOMPAT_FTYPE)
> +		(XFS_SB_FEAT_INCOMPAT_FTYPE | \
> +		 XFS_SB_FEAT_INCOMPAT_META_UUID)
>  
>  #define XFS_SB_FEAT_INCOMPAT_UNKNOWN	~XFS_SB_FEAT_INCOMPAT_ALL
>  static inline bool
> @@ -507,6 +511,18 @@ static inline int xfs_sb_version_hasfinobt(xfs_sb_t *sbp)
>  }
>  
>  /*
> + * 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 int xfs_sb_version_hasmetauuid(xfs_sb_t *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
>   */
>  
> diff --git a/fs/xfs/libxfs/xfs_sb.c b/fs/xfs/libxfs/xfs_sb.c
> index dc4bfc5..547230f 100644
> --- a/fs/xfs/libxfs/xfs_sb.c
> +++ b/fs/xfs/libxfs/xfs_sb.c
> @@ -377,6 +377,13 @@ __xfs_sb_from_disk(
>  	to->sb_pad = 0;
>  	to->sb_pquotino = be64_to_cpu(from->sb_pquotino);
>  	to->sb_lsn = be64_to_cpu(from->sb_lsn);
> +	if (xfs_sb_version_hasmetauuid(to)) {
> +		memcpy(&to->sb_meta_uuid, &from->sb_meta_uuid,
> +					sizeof(to->sb_meta_uuid));
> +	} else {
> +		memcpy(&to->sb_meta_uuid, &from->sb_uuid,
> +					sizeof(to->sb_meta_uuid));
> +	}
>  	/* Convert on-disk flags to in-memory flags? */
>  	if (convert_xquota)
>  		xfs_sb_quota_from_disk(to);
> @@ -518,6 +525,10 @@ xfs_sb_to_disk(
>  				cpu_to_be32(from->sb_features_log_incompat);
>  		to->sb_pad = 0;
>  		to->sb_lsn = cpu_to_be64(from->sb_lsn);
> +		if (xfs_sb_version_hasmetauuid(from)) {
> +			memcpy(&to->sb_meta_uuid, &from->sb_meta_uuid,
> +						sizeof(to->sb_meta_uuid));
> +		}
>  	}
>  }
>  
> diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c
> index 516162b..27f76ca 100644
> --- a/fs/xfs/libxfs/xfs_alloc.c
> +++ b/fs/xfs/libxfs/xfs_alloc.c
> @@ -450,7 +450,7 @@ xfs_agfl_verify(
>  	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;
> @@ -2203,7 +2203,7 @@ xfs_agf_verify(
>  	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) &&
> diff --git a/fs/xfs/libxfs/xfs_alloc_btree.c b/fs/xfs/libxfs/xfs_alloc_btree.c
> index 59d521c..90de071 100644
> --- a/fs/xfs/libxfs/xfs_alloc_btree.c
> +++ b/fs/xfs/libxfs/xfs_alloc_btree.c
> @@ -295,7 +295,7 @@ xfs_allocbt_verify(
>  	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;
> @@ -313,7 +313,7 @@ xfs_allocbt_verify(
>  	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;
> diff --git a/fs/xfs/libxfs/xfs_attr_leaf.c b/fs/xfs/libxfs/xfs_attr_leaf.c
> index 04e79d5..6755762 100644
> --- a/fs/xfs/libxfs/xfs_attr_leaf.c
> +++ b/fs/xfs/libxfs/xfs_attr_leaf.c
> @@ -262,7 +262,7 @@ xfs_attr3_leaf_verify(
>  		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;
> @@ -1056,7 +1056,7 @@ xfs_attr3_leaf_create(
>  
>  		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 {
> diff --git a/fs/xfs/libxfs/xfs_attr_remote.c b/fs/xfs/libxfs/xfs_attr_remote.c
> index 20de88d..eba0d1e 100644
> --- a/fs/xfs/libxfs/xfs_attr_remote.c
> +++ b/fs/xfs/libxfs/xfs_attr_remote.c
> @@ -100,7 +100,7 @@ xfs_attr3_rmt_verify(
>  		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;
> @@ -217,7 +217,7 @@ xfs_attr3_rmt_hdr_set(
>  	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);
>  
> diff --git a/fs/xfs/libxfs/xfs_bmap_btree.c b/fs/xfs/libxfs/xfs_bmap_btree.c
> index 2c44c8e..6b0cf65 100644
> --- a/fs/xfs/libxfs/xfs_bmap_btree.c
> +++ b/fs/xfs/libxfs/xfs_bmap_btree.c
> @@ -349,7 +349,8 @@ xfs_bmbt_to_bmdr(
>  
>  	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
> @@ -647,7 +648,7 @@ xfs_bmbt_verify(
>  	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;
> diff --git a/fs/xfs/libxfs/xfs_btree.c b/fs/xfs/libxfs/xfs_btree.c
> index c72283d..f7d7ee7 100644
> --- a/fs/xfs/libxfs/xfs_btree.c
> +++ b/fs/xfs/libxfs/xfs_btree.c
> @@ -65,7 +65,8 @@ xfs_btree_check_lblock(
>  
>  	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);
>  	}
> @@ -115,7 +116,8 @@ xfs_btree_check_sblock(
>  
>  	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);
>  	}
> @@ -1000,7 +1002,7 @@ xfs_btree_init_block_int(
>  		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;
>  		}
> @@ -1013,7 +1015,7 @@ xfs_btree_init_block_int(
>  		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;
>  		}
>  	}
> diff --git a/fs/xfs/libxfs/xfs_da_btree.c b/fs/xfs/libxfs/xfs_da_btree.c
> index 2385f8c..e9f6709 100644
> --- a/fs/xfs/libxfs/xfs_da_btree.c
> +++ b/fs/xfs/libxfs/xfs_da_btree.c
> @@ -146,7 +146,7 @@ xfs_da3_node_verify(
>  		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;
> @@ -324,7 +324,7 @@ xfs_da3_node_create(
>  		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;
>  	}
> diff --git a/fs/xfs/libxfs/xfs_dir2_block.c b/fs/xfs/libxfs/xfs_dir2_block.c
> index 9354e19..4778d1d 100644
> --- a/fs/xfs/libxfs/xfs_dir2_block.c
> +++ b/fs/xfs/libxfs/xfs_dir2_block.c
> @@ -67,7 +67,7 @@ xfs_dir3_block_verify(
>  	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;
> @@ -157,7 +157,7 @@ xfs_dir3_block_init(
>  		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;
>  
>  	}
> diff --git a/fs/xfs/libxfs/xfs_dir2_data.c b/fs/xfs/libxfs/xfs_dir2_data.c
> index de1ea16..6a57fdb 100644
> --- a/fs/xfs/libxfs/xfs_dir2_data.c
> +++ b/fs/xfs/libxfs/xfs_dir2_data.c
> @@ -220,7 +220,7 @@ xfs_dir3_data_verify(
>  	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;
> @@ -604,7 +604,7 @@ xfs_dir3_data_init(
>  		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);
> 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 @@ xfs_dir3_leaf_verify(
>  
>  		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 @@ xfs_dir3_leaf_init(
>  					 : 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);
> diff --git a/fs/xfs/libxfs/xfs_dir2_node.c b/fs/xfs/libxfs/xfs_dir2_node.c
> index 41b80d3..527b733 100644
> --- a/fs/xfs/libxfs/xfs_dir2_node.c
> +++ b/fs/xfs/libxfs/xfs_dir2_node.c
> @@ -93,7 +93,7 @@ xfs_dir3_free_verify(
>  
>  		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;
> @@ -226,7 +226,7 @@ xfs_dir3_free_get_buf(
>  
>  		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);
> diff --git a/fs/xfs/libxfs/xfs_dquot_buf.c b/fs/xfs/libxfs/xfs_dquot_buf.c
> index 6fbf2d8..5331b7f 100644
> --- a/fs/xfs/libxfs/xfs_dquot_buf.c
> +++ b/fs/xfs/libxfs/xfs_dquot_buf.c
> @@ -163,7 +163,7 @@ xfs_dqcheck(
>  	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);
>  	}
> @@ -198,7 +198,7 @@ xfs_dquot_buf_verify_crc(
>  		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;
> diff --git a/fs/xfs/libxfs/xfs_ialloc.c b/fs/xfs/libxfs/xfs_ialloc.c
> index 07349a1..d9b90c0 100644
> --- a/fs/xfs/libxfs/xfs_ialloc.c
> +++ b/fs/xfs/libxfs/xfs_ialloc.c
> @@ -307,7 +307,8 @@ xfs_ialloc_inode_init(
>  			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 */
> @@ -2049,7 +2050,7 @@ xfs_agi_verify(
>  	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.
> diff --git a/fs/xfs/libxfs/xfs_ialloc_btree.c b/fs/xfs/libxfs/xfs_ialloc_btree.c
> index 964c465..0fa2a27 100644
> --- a/fs/xfs/libxfs/xfs_ialloc_btree.c
> +++ b/fs/xfs/libxfs/xfs_ialloc_btree.c
> @@ -230,7 +230,7 @@ xfs_inobt_verify(
>  	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;
> diff --git a/fs/xfs/libxfs/xfs_inode_buf.c b/fs/xfs/libxfs/xfs_inode_buf.c
> index 002b6b3..0f9563e 100644
> --- a/fs/xfs/libxfs/xfs_inode_buf.c
> +++ b/fs/xfs/libxfs/xfs_inode_buf.c
> @@ -306,7 +306,7 @@ xfs_dinode_verify(
>  		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;
>  }
> @@ -368,7 +368,7 @@ xfs_iread(
>  		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;
> diff --git a/fs/xfs/libxfs/xfs_symlink_remote.c b/fs/xfs/libxfs/xfs_symlink_remote.c
> index e7e26bd..8f8af05 100644
> --- a/fs/xfs/libxfs/xfs_symlink_remote.c
> +++ b/fs/xfs/libxfs/xfs_symlink_remote.c
> @@ -63,7 +63,7 @@ xfs_symlink_hdr_set(
>  	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;
> @@ -107,7 +107,7 @@ xfs_symlink_verify(
>  		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;
> diff --git a/fs/xfs/xfs_dquot.c b/fs/xfs/xfs_dquot.c
> index 02c01bb..e0c7e15 100644
> --- a/fs/xfs/xfs_dquot.c
> +++ b/fs/xfs/xfs_dquot.c
> @@ -251,7 +251,7 @@ xfs_qm_init_dquot_blk(
>  		d->dd_diskdq.d_id = cpu_to_be32(curid);
>  		d->dd_diskdq.d_flags = type;
>  		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);
>  		}
> diff --git a/fs/xfs/xfs_fsops.c b/fs/xfs/xfs_fsops.c
> index cb7e8a2..9c892cd 100644
> --- a/fs/xfs/xfs_fsops.c
> +++ b/fs/xfs/xfs_fsops.c
> @@ -248,7 +248,7 @@ xfs_growfs_data_private(
>  		agf->agf_freeblks = cpu_to_be32(tmpsize);
>  		agf->agf_longest = cpu_to_be32(tmpsize);
>  		if (xfs_sb_version_hascrc(&mp->m_sb))
> -			uuid_copy(&agf->agf_uuid, &mp->m_sb.sb_uuid);
> +			uuid_copy(&agf->agf_uuid, &mp->m_sb.sb_meta_uuid);
>  
>  		error = xfs_bwrite(bp);
>  		xfs_buf_relse(bp);
> @@ -271,7 +271,7 @@ xfs_growfs_data_private(
>  		if (xfs_sb_version_hascrc(&mp->m_sb)) {
>  			agfl->agfl_magicnum = cpu_to_be32(XFS_AGFL_MAGIC);
>  			agfl->agfl_seqno = cpu_to_be32(agno);
> -			uuid_copy(&agfl->agfl_uuid, &mp->m_sb.sb_uuid);
> +			uuid_copy(&agfl->agfl_uuid, &mp->m_sb.sb_meta_uuid);
>  		}
>  
>  		agfl_bno = XFS_BUF_TO_AGFL_BNO(mp, bp);
> @@ -307,7 +307,7 @@ xfs_growfs_data_private(
>  		agi->agi_newino = cpu_to_be32(NULLAGINO);
>  		agi->agi_dirino = cpu_to_be32(NULLAGINO);
>  		if (xfs_sb_version_hascrc(&mp->m_sb))
> -			uuid_copy(&agi->agi_uuid, &mp->m_sb.sb_uuid);
> +			uuid_copy(&agi->agi_uuid, &mp->m_sb.sb_meta_uuid);
>  		if (xfs_sb_version_hasfinobt(&mp->m_sb)) {
>  			agi->agi_free_root = cpu_to_be32(XFS_FIBT_BLOCK(mp));
>  			agi->agi_free_level = cpu_to_be32(1);
> diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
> index d6ebc85..9a2ecb7 100644
> --- a/fs/xfs/xfs_inode.c
> +++ b/fs/xfs/xfs_inode.c
> @@ -787,7 +787,7 @@ xfs_ialloc(
>  
>  	if (ip->i_d.di_version == 3) {
>  		ASSERT(ip->i_d.di_ino == ino);
> -		ASSERT(uuid_equal(&ip->i_d.di_uuid, &mp->m_sb.sb_uuid));
> +		ASSERT(uuid_equal(&ip->i_d.di_uuid, &mp->m_sb.sb_meta_uuid));
>  		ip->i_d.di_crc = 0;
>  		ip->i_d.di_changecount = 1;
>  		ip->i_d.di_lsn = 0;
> 
> _______________________________________________
> xfs mailing list
> xfs@oss.sgi.com
> http://oss.sgi.com/mailman/listinfo/xfs

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^ permalink raw reply	[flat|nested] 11+ messages in thread

* Re: [PATCH 1/2] xfs: create new metadata UUID field and incompat flag
  2015-05-11 16:14   ` Brian Foster
@ 2015-05-11 16:52     ` Eric Sandeen
  2015-05-11 21:49       ` Dave Chinner
  0 siblings, 1 reply; 11+ messages in thread
From: Eric Sandeen @ 2015-05-11 16:52 UTC (permalink / raw)
  To: Brian Foster; +Cc: Eric Sandeen, xfs-oss

On 5/11/15 11:14 AM, Brian Foster wrote:
> On Fri, May 08, 2015 at 03:48:16PM -0500, Eric Sandeen wrote:
>> > 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 or clearing
>> > of the incompat flag as appropriate, as the UUID gets written.
>> > 
>> > If the incompat flag is not set, copy the user-visible UUID into
>> > into the meta_uuid slot in memory; this 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>
>> > ---
> This all looks fine to me. The only thing that confuses me is why we
> continue to use sb_uuid for the log. Eric points out on irc that we
> can't modify the uuid when the log is dirty, so we can't actually break
> anything in this manner. In other words, we effectively already handle a
> modified uuid with respect to the log.
> 
> That said, it seems inconsistent to me to create a metadata uuid field
> and not use it for all metadata. My expectation from such a change is to
> see sb_uuid now used only for user facing bits (e.g., mount and get geo
> related) and sb_meta_uuid used everywhere else. Instead, we use sb_uuid
> for the user facing bits, sb_meta_uuid for the internal bits that can't
> handle a uuid change and sb_uuid for the internal bits that can.
> 
> I suppose I could be convinced otherwise if there's context I'm missing,
> but otherwise this seems a bit confusing to me...
> 
> Brian

Yeah, I'm sympathetic to that argument.  I can look into using sb_meta_uuid
for the log too, if the incompat flag is set.

I had skipped it just because that use of the UUID predated the CRC changes.

-Eric

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xfs mailing list
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http://oss.sgi.com/mailman/listinfo/xfs

^ permalink raw reply	[flat|nested] 11+ messages in thread

* Re: [PATCH 1/2] xfs: create new metadata UUID field and incompat flag
  2015-05-11 16:52     ` Eric Sandeen
@ 2015-05-11 21:49       ` Dave Chinner
  2015-05-11 23:50         ` Eric Sandeen
  2015-05-12 11:11         ` Brian Foster
  0 siblings, 2 replies; 11+ messages in thread
From: Dave Chinner @ 2015-05-11 21:49 UTC (permalink / raw)
  To: Eric Sandeen; +Cc: Eric Sandeen, Brian Foster, xfs-oss

On Mon, May 11, 2015 at 11:52:52AM -0500, Eric Sandeen wrote:
> On 5/11/15 11:14 AM, Brian Foster wrote:
> > On Fri, May 08, 2015 at 03:48:16PM -0500, Eric Sandeen wrote:
> >> > 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 or clearing
> >> > of the incompat flag as appropriate, as the UUID gets written.
> >> > 
> >> > If the incompat flag is not set, copy the user-visible UUID into
> >> > into the meta_uuid slot in memory; this 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>
> >> > ---
> > This all looks fine to me. The only thing that confuses me is why we
> > continue to use sb_uuid for the log. Eric points out on irc that we
> > can't modify the uuid when the log is dirty, so we can't actually break
> > anything in this manner. In other words, we effectively already handle a
> > modified uuid with respect to the log.
> > 
> > That said, it seems inconsistent to me to create a metadata uuid field
> > and not use it for all metadata. My expectation from such a change is to
> > see sb_uuid now used only for user facing bits (e.g., mount and get geo
> > related) and sb_meta_uuid used everywhere else. Instead, we use sb_uuid
> > for the user facing bits, sb_meta_uuid for the internal bits that can't
> > handle a uuid change and sb_uuid for the internal bits that can.
> > 
> > I suppose I could be convinced otherwise if there's context I'm missing,
> > but otherwise this seems a bit confusing to me...
> > 
> > Brian
> 
> Yeah, I'm sympathetic to that argument.  I can look into using sb_meta_uuid
> for the log too, if the incompat flag is set.

The log uuid is user facing, like the superblock uuid. i.e. there
are tools that identify external log devices by checking that the
uuid in the log matches the user facing uuid in the superblock.
Hence the log uuid needs to use the uuid that is reported to
userspace.

> I had skipped it just because that use of the UUID predated the CRC changes.

Changing the uuid results in the log being zeroed, so the uuid in
the log can be changed without issue, even if we are using CRCs.

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

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http://oss.sgi.com/mailman/listinfo/xfs

^ permalink raw reply	[flat|nested] 11+ messages in thread

* Re: [PATCH 1/2] xfs: create new metadata UUID field and incompat flag
  2015-05-11 21:49       ` Dave Chinner
@ 2015-05-11 23:50         ` Eric Sandeen
  2015-05-12  1:58           ` Dave Chinner
  2015-05-12 11:11         ` Brian Foster
  1 sibling, 1 reply; 11+ messages in thread
From: Eric Sandeen @ 2015-05-11 23:50 UTC (permalink / raw)
  To: Dave Chinner; +Cc: Eric Sandeen, Brian Foster, xfs-oss

On 5/11/15 4:49 PM, Dave Chinner wrote:
> On Mon, May 11, 2015 at 11:52:52AM -0500, Eric Sandeen wrote:
>> On 5/11/15 11:14 AM, Brian Foster wrote:
>>> On Fri, May 08, 2015 at 03:48:16PM -0500, Eric Sandeen wrote:
>>>>> 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 or clearing
>>>>> of the incompat flag as appropriate, as the UUID gets written.
>>>>>
>>>>> If the incompat flag is not set, copy the user-visible UUID into
>>>>> into the meta_uuid slot in memory; this 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>
>>>>> ---
>>> This all looks fine to me. The only thing that confuses me is why we
>>> continue to use sb_uuid for the log. Eric points out on irc that we
>>> can't modify the uuid when the log is dirty, so we can't actually break
>>> anything in this manner. In other words, we effectively already handle a
>>> modified uuid with respect to the log.
>>>
>>> That said, it seems inconsistent to me to create a metadata uuid field
>>> and not use it for all metadata. My expectation from such a change is to
>>> see sb_uuid now used only for user facing bits (e.g., mount and get geo
>>> related) and sb_meta_uuid used everywhere else. Instead, we use sb_uuid
>>> for the user facing bits, sb_meta_uuid for the internal bits that can't
>>> handle a uuid change and sb_uuid for the internal bits that can.
>>>
>>> I suppose I could be convinced otherwise if there's context I'm missing,
>>> but otherwise this seems a bit confusing to me...
>>>
>>> Brian
>>
>> Yeah, I'm sympathetic to that argument.  I can look into using sb_meta_uuid
>> for the log too, if the incompat flag is set.
> 
> The log uuid is user facing, like the superblock uuid. i.e. there
> are tools that identify external log devices by checking that the
> uuid in the log matches the user facing uuid in the superblock.
> Hence the log uuid needs to use the uuid that is reported to
> userspace.


None that are external to xfsprogs, I think, are there? (1) - but still.
I'm happy to leave it as it is ... I don't think it really matters either way.

-Eric

(1) at one point I wanted to teach blkid to find an external log by UUID,
but there is no "log superblock" so I gave up on that idea.

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^ permalink raw reply	[flat|nested] 11+ messages in thread

* Re: [PATCH 1/2] xfs: create new metadata UUID field and incompat flag
  2015-05-11 23:50         ` Eric Sandeen
@ 2015-05-12  1:58           ` Dave Chinner
  0 siblings, 0 replies; 11+ messages in thread
From: Dave Chinner @ 2015-05-12  1:58 UTC (permalink / raw)
  To: Eric Sandeen; +Cc: Eric Sandeen, Brian Foster, xfs-oss

On Mon, May 11, 2015 at 06:50:00PM -0500, Eric Sandeen wrote:
> On 5/11/15 4:49 PM, Dave Chinner wrote:
> > On Mon, May 11, 2015 at 11:52:52AM -0500, Eric Sandeen wrote:
> >> On 5/11/15 11:14 AM, Brian Foster wrote:
> >>> On Fri, May 08, 2015 at 03:48:16PM -0500, Eric Sandeen wrote:
> >>> I suppose I could be convinced otherwise if there's context I'm missing,
> >>> but otherwise this seems a bit confusing to me...
> >>>
> >>> Brian
> >>
> >> Yeah, I'm sympathetic to that argument.  I can look into using sb_meta_uuid
> >> for the log too, if the incompat flag is set.
> > 
> > The log uuid is user facing, like the superblock uuid. i.e. there
> > are tools that identify external log devices by checking that the
> > uuid in the log matches the user facing uuid in the superblock.
> > Hence the log uuid needs to use the uuid that is reported to
> > userspace.
> 
> 
> None that are external to xfsprogs, I think, are there? (1) - but still.
> I'm happy to leave it as it is ... I don't think it really matters either way.
> 
> -Eric
> 
> (1) at one point I wanted to teach blkid to find an external log by UUID,
> but there is no "log superblock" so I gave up on that idea.

Well, we don't know, really, do we? It's best to play it safe and
keep it the same as the user visible filesytem uuid, as that is
what is currently expected by anything poking at block dev UUIDs...

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

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^ permalink raw reply	[flat|nested] 11+ messages in thread

* Re: [PATCH 1/2] xfs: create new metadata UUID field and incompat flag
  2015-05-11 21:49       ` Dave Chinner
  2015-05-11 23:50         ` Eric Sandeen
@ 2015-05-12 11:11         ` Brian Foster
  1 sibling, 0 replies; 11+ messages in thread
From: Brian Foster @ 2015-05-12 11:11 UTC (permalink / raw)
  To: Dave Chinner; +Cc: Eric Sandeen, Eric Sandeen, xfs-oss

On Tue, May 12, 2015 at 07:49:02AM +1000, Dave Chinner wrote:
> On Mon, May 11, 2015 at 11:52:52AM -0500, Eric Sandeen wrote:
> > On 5/11/15 11:14 AM, Brian Foster wrote:
> > > On Fri, May 08, 2015 at 03:48:16PM -0500, Eric Sandeen wrote:
> > >> > 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 or clearing
> > >> > of the incompat flag as appropriate, as the UUID gets written.
> > >> > 
> > >> > If the incompat flag is not set, copy the user-visible UUID into
> > >> > into the meta_uuid slot in memory; this 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>
> > >> > ---
> > > This all looks fine to me. The only thing that confuses me is why we
> > > continue to use sb_uuid for the log. Eric points out on irc that we
> > > can't modify the uuid when the log is dirty, so we can't actually break
> > > anything in this manner. In other words, we effectively already handle a
> > > modified uuid with respect to the log.
> > > 
> > > That said, it seems inconsistent to me to create a metadata uuid field
> > > and not use it for all metadata. My expectation from such a change is to
> > > see sb_uuid now used only for user facing bits (e.g., mount and get geo
> > > related) and sb_meta_uuid used everywhere else. Instead, we use sb_uuid
> > > for the user facing bits, sb_meta_uuid for the internal bits that can't
> > > handle a uuid change and sb_uuid for the internal bits that can.
> > > 
> > > I suppose I could be convinced otherwise if there's context I'm missing,
> > > but otherwise this seems a bit confusing to me...
> > > 
> > > Brian
> > 
> > Yeah, I'm sympathetic to that argument.  I can look into using sb_meta_uuid
> > for the log too, if the incompat flag is set.
> 
> The log uuid is user facing, like the superblock uuid. i.e. there
> are tools that identify external log devices by checking that the
> uuid in the log matches the user facing uuid in the superblock.
> Hence the log uuid needs to use the uuid that is reported to
> userspace.
> 

Ok, sounds good. Thanks for the explanation.

Brian

> > I had skipped it just because that use of the UUID predated the CRC changes.
> 
> Changing the uuid results in the log being zeroed, so the uuid in
> the log can be changed without issue, even if we are using CRCs.
> 
> Cheers,
> 
> Dave.
> -- 
> Dave Chinner
> david@fromorbit.com
> 
> _______________________________________________
> xfs mailing list
> xfs@oss.sgi.com
> http://oss.sgi.com/mailman/listinfo/xfs

_______________________________________________
xfs mailing list
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^ permalink raw reply	[flat|nested] 11+ messages in thread

end of thread, other threads:[~2015-05-12 11:11 UTC | newest]

Thread overview: 11+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2015-05-08 20:40 [PATCH 0/2] allow UUID changes on V5/CRC filesystems Eric Sandeen
2015-05-08 20:48 ` [PATCH 1/2] xfs: create new metadata UUID field and incompat flag Eric Sandeen
2015-05-11 16:14   ` Brian Foster
2015-05-11 16:52     ` Eric Sandeen
2015-05-11 21:49       ` Dave Chinner
2015-05-11 23:50         ` Eric Sandeen
2015-05-12  1:58           ` Dave Chinner
2015-05-12 11:11         ` Brian Foster
2015-05-08 20:59 ` [PATCH 2/2] xfsprogs: Add new sb_meta_uuid field, and userspace tools to manipulate it Eric Sandeen
2015-05-08 21:14   ` Eric Sandeen
2015-05-08 21:49   ` [PATCH 2/2 V2] " Eric Sandeen

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