Proposal/RFC: new metadata-specific UUID for V5 supers

Proposal/RFC: new metadata-specific UUID for V5 supers

[Eric Sandeen]

Wanted to float this & see what people think...

Today, it's impossible (FSVO impossible) to change a V5 filesystem's
UUID, because that UUID is stamped into every bit of metadata.  If
not impossible, it's unimplemented and any implementation would be
terribly inefficient.

With 20/20 hindsight, an sb_meta_uuid field, separate from the sb_uuid
field that is userspace-visible, would have avoided this problem.

We can certainly add it, but it'd need to be an incompat change, because
old kernels would see this as catastrophic mismatching of every bit
of metadata on a V5 superblock filesystem.

Other than that little problem (o_O) it'd be trivial to implement.

Thoughts?

Thanks,
-Eric

p.s. Thanks to Zach for making me think about this, but I'm not
blaming him for my decision to propose it.  ;)

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Re: Proposal/RFC: new metadata-specific UUID for V5 supers

[Dave Chinner]

On Mon, Apr 27, 2015 at 05:10:25PM -0500, Eric Sandeen wrote:
> Wanted to float this & see what people think...
> 
> Today, it's impossible (FSVO impossible) to change a V5 filesystem's
> UUID, because that UUID is stamped into every bit of metadata.  If
> not impossible, it's unimplemented and any implementation would be
> terribly inefficient.
> 
> With 20/20 hindsight, an sb_meta_uuid field, separate from the sb_uuid
> field that is userspace-visible, would have avoided this problem.

Actually, it was done like this intentionally.

AFAIA, the only time you need to change the UUID is if you are doing
clones or snapshots of the filesystem. If you are doing a clone,
then we are reading and writing every piece of metadata anyway, so
we /could/ add support for modifying the UUIDs to the cloning
program during the write. e.g. xfs_copy already does this UUID
modification for non-crc filesystems, so we could modify it to reuse
the db/metadump metadata walk to rewrite the UUIDs and recalculate
the CRCs once the copy has been done. That's the clone problem
solved.

If we have a snapshot, then changing the UUID means a COW of every
single metadata block as we change them, which will cause all sorts
of fragmentation and duplication problems in the underlying snapshot
device due to the random 4k distribution of the metadata throughout
the filesystem. So we take even more of a penalty there, as it also
affects runtime performance and space usage of the underlying
device. Hence I'm not sure we actually want to change behaviour
here.

> We can certainly add it, but it'd need to be an incompat change, because
> old kernels would see this as catastrophic mismatching of every bit
> of metadata on a V5 superblock filesystem.
> 
> Other than that little problem (o_O) it'd be trivial to implement.

So what you are proposing is a fixed UUID for metadata, and a
variable UUID for userspace presentation (i.e. blkid) and mount
checking? Doesn't that defeat the purpose of the UUID which is to
identify the filesystem the metadata originated from? i.e. don't we
still need to change the internal metadata UUID if we want to retain
the original purpose of the UUID stamping in the metadata?

> Thoughts?

Can you describe the motivation for needing to change UUIDs? i.e.
what's the use case that has brought this up? I'd like to know if
there is a problem other than writable snapshots being required to
be mounted "-o nouuid", which we already require for read-only
snapshots (i.e "-o ro,norecovery,nouuid")?

Cheers,

Dave.
-- 
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david@fromorbit.com

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Re: Proposal/RFC: new metadata-specific UUID for V5 supers

[Eric Sandeen]

On 4/27/15 6:37 PM, Dave Chinner wrote:
> On Mon, Apr 27, 2015 at 05:10:25PM -0500, Eric Sandeen wrote:
>> Wanted to float this & see what people think...
>>
>> Today, it's impossible (FSVO impossible) to change a V5 filesystem's
>> UUID, because that UUID is stamped into every bit of metadata.  If
>> not impossible, it's unimplemented and any implementation would be
>> terribly inefficient.
>>
>> With 20/20 hindsight, an sb_meta_uuid field, separate from the sb_uuid
>> field that is userspace-visible, would have avoided this problem.
> 
> Actually, it was done like this intentionally.
> 
> AFAIA, the only time you need to change the UUID is if you are doing
> clones or snapshots of the filesystem. If you are doing a clone,
> then we are reading and writing every piece of metadata anyway, so
> we /could/ add support for modifying the UUIDs to the cloning
> program during the write. e.g. xfs_copy already does this UUID
> modification for non-crc filesystems, so we could modify it to reuse
> the db/metadump metadata walk to rewrite the UUIDs and recalculate
> the CRCs once the copy has been done. That's the clone problem
> solved.

Fair enough.

> If we have a snapshot, then changing the UUID means a COW of every
> single metadata block as we change them, which will cause all sorts
> of fragmentation and duplication problems in the underlying snapshot
> device due to the random 4k distribution of the metadata throughout
> the filesystem. So we take even more of a penalty there, as it also
> affects runtime performance and space usage of the underlying
> device. Hence I'm not sure we actually want to change behaviour
> here.

This I'm not following.  Changing UUID by rewriting every piece
would be painful in this case, yes.  I guess we're in violent agreement
on this part?  (that changing the UUID of a RW snapshot would be nuts).

>> We can certainly add it, but it'd need to be an incompat change, because
>> old kernels would see this as catastrophic mismatching of every bit
>> of metadata on a V5 superblock filesystem.
>>
>> Other than that little problem (o_O) it'd be trivial to implement.
> 
> So what you are proposing is a fixed UUID for metadata, and a
> variable UUID for userspace presentation (i.e. blkid) and mount
> checking? Doesn't that defeat the purpose of the UUID which is to
> identify the filesystem the metadata originated from? i.e. don't we
> still need to change the internal metadata UUID if we want to retain
> the original purpose of the UUID stamping in the metadata?

No, I don't think so.  sb_uuid could be changed just like it always ever
could, for any reason one might wish to change it; it'd be relatively
trivial. sb_meta_uuid would be set at mkfs time, and would never change;
it's the matching, immutable metadata consistency number.

sb_uuid is for external filesystem identification; sb_meta_uuid is for
internal consistency.

If we got a metadata uuid mismatch from xfs_repair, xfs_db (or xfs_admin)
could easily tell us what the sb_meta_uuid of any given filesystem might
be, and we wouldn't care about the external identifier UUID for this purpose.

>> Thoughts?
> 
> Can you describe the motivation for needing to change UUIDs? i.e.
> what's the use case that has brought this up? I'd like to know if
> there is a problem other than writable snapshots being required to
> be mounted "-o nouuid", which we already require for read-only
> snapshots (i.e "-o ro,norecovery,nouuid")?

Well, it's just the loss of ability to change UUID, which is something
People Used To Do(tm), and now can't.  It does come up.  Honestly if it
had been done from day 0, it'd be a no-brainer I think.  Doing it now,
with an incompat flag, might not be a reasonable tradeoff.

-Eric

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Re: Proposal/RFC: new metadata-specific UUID for V5 supers

[Dave Chinner]

On Mon, Apr 27, 2015 at 07:52:40PM -0500, Eric Sandeen wrote:
> On 4/27/15 6:37 PM, Dave Chinner wrote:
> > On Mon, Apr 27, 2015 at 05:10:25PM -0500, Eric Sandeen wrote:
> >> Wanted to float this & see what people think...
> >>
> >> Today, it's impossible (FSVO impossible) to change a V5 filesystem's
> >> UUID, because that UUID is stamped into every bit of metadata.  If
> >> not impossible, it's unimplemented and any implementation would be
> >> terribly inefficient.
> >>
> >> With 20/20 hindsight, an sb_meta_uuid field, separate from the sb_uuid
> >> field that is userspace-visible, would have avoided this problem.
> > 
> > Actually, it was done like this intentionally.
> > 
> > AFAIA, the only time you need to change the UUID is if you are doing
> > clones or snapshots of the filesystem. If you are doing a clone,
> > then we are reading and writing every piece of metadata anyway, so
> > we /could/ add support for modifying the UUIDs to the cloning
> > program during the write. e.g. xfs_copy already does this UUID
> > modification for non-crc filesystems, so we could modify it to reuse
> > the db/metadump metadata walk to rewrite the UUIDs and recalculate
> > the CRCs once the copy has been done. That's the clone problem
> > solved.
> 
> Fair enough.
> 
> > If we have a snapshot, then changing the UUID means a COW of every
> > single metadata block as we change them, which will cause all sorts
> > of fragmentation and duplication problems in the underlying snapshot
> > device due to the random 4k distribution of the metadata throughout
> > the filesystem. So we take even more of a penalty there, as it also
> > affects runtime performance and space usage of the underlying
> > device. Hence I'm not sure we actually want to change behaviour
> > here.
> 
> This I'm not following.  Changing UUID by rewriting every piece
> would be painful in this case, yes.  I guess we're in violent agreement
> on this part?  (that changing the UUID of a RW snapshot would be nuts).
> 
> >> We can certainly add it, but it'd need to be an incompat change, because
> >> old kernels would see this as catastrophic mismatching of every bit
> >> of metadata on a V5 superblock filesystem.
> >>
> >> Other than that little problem (o_O) it'd be trivial to implement.
> > 
> > So what you are proposing is a fixed UUID for metadata, and a
> > variable UUID for userspace presentation (i.e. blkid) and mount
> > checking? Doesn't that defeat the purpose of the UUID which is to
> > identify the filesystem the metadata originated from? i.e. don't we
> > still need to change the internal metadata UUID if we want to retain
> > the original purpose of the UUID stamping in the metadata?
> 
> No, I don't think so.  sb_uuid could be changed just like it always ever
> could, for any reason one might wish to change it; it'd be relatively
> trivial. sb_meta_uuid would be set at mkfs time, and would never change;
> it's the matching, immutable metadata consistency number.
> 
> sb_uuid is for external filesystem identification; sb_meta_uuid is for
> internal consistency.
> 
> If we got a metadata uuid mismatch from xfs_repair, xfs_db (or xfs_admin)
> could easily tell us what the sb_meta_uuid of any given filesystem might
> be, and we wouldn't care about the external identifier UUID for this purpose.

We already have a field for that - it's called the filesystem
label and the entire userspace infrastructure is already aware of
it. 

# blkid /dev/md0 /dev/sda1
/dev/md0: LABEL="root" UUID="91e3089c-f00f-4c56-ab5a-ea8f18b6c011" TYPE="xfs" 
/dev/sda1: LABEL="boot" UUID="509d4612-3bbc-4876-a6ac-1d5454ea074d" TYPE="ext2"
# $ ls -l /dev/disk/by-label
total 0
lrwxrwxrwx 1 root root 10 Mar 16 09:01 boot -> ../../sda1
lrwxrwxrwx 1 root root  9 Mar 16 09:01 root -> ../../md0
# man 5 fstab
.....
    Instead  of  giving  the  device  explicitly,  one  may indicate
    the (ext2 or xfs) filesystem that is to be mounted by its UUID
    or volume label (cf.  e2label(8) or xfs_admin(8)), writing
    LABEL=<label> or UUID=<uuid>, e.g., `LABEL=Boot'  or
    `UUID=3e6be9de-8139-11d1-9106-a43f08d823a6'.

> > what's the use case that has brought this up? I'd like to know if
> > there is a problem other than writable snapshots being required to
> > be mounted "-o nouuid", which we already require for read-only
> > snapshots (i.e "-o ro,norecovery,nouuid")?
> 
> Well, it's just the loss of ability to change UUID, which is something
> People Used To Do(tm), and now can't.  It does come up.  Honestly if it
> had been done from day 0, it'd be a no-brainer I think.  Doing it now,
> with an incompat flag, might not be a reasonable tradeoff.

I think that labels are a far better way of dealing with this
problem. Get rid of the UUID mount checking (and hence the nouuid
mount option), and tell people to use by-label instead of by-uuid to
identify their filesystems when doing clones and snapshots. Labels
make it much easier for humans to identify the filesystem than
UUIDs...

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

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Re: Proposal/RFC: new metadata-specific UUID for V5 supers

[Carlos E. R.]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256

On 2015-04-28 03:20, Dave Chinner wrote:

>> Well, it's just the loss of ability to change UUID, which is
>> something People Used To Do(tm), and now can't.  It does come up.
>> Honestly if it had been done from day 0, it'd be a no-brainer I
>> think.  Doing it now, with an incompat flag, might not be a
>> reasonable tradeoff.
> 
> I think that labels are a far better way of dealing with this 
> problem. Get rid of the UUID mount checking (and hence the nouuid 
> mount option), and tell people to use by-label instead of by-uuid
> to identify their filesystems when doing clones and snapshots.
> Labels make it much easier for humans to identify the filesystem
> than UUIDs...

As a plain user, I can say that I have needed to mount both the
filesystem and its backup image, but Linux refused on the basis of the
id being the same. Of course, all identifiers are the same, label and
uuid.

- -- 
Cheers / Saludos,

		Carlos E. R.

  (from 13.1 x86_64 "Bottle" (Minas Tirith))
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Re: Proposal/RFC: new metadata-specific UUID for V5 supers

[Dave Chinner]

On Tue, Apr 28, 2015 at 03:35:54AM +0200, Carlos E. R. wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA256
> 
> On 2015-04-28 03:20, Dave Chinner wrote:
> 
> >> Well, it's just the loss of ability to change UUID, which is
> >> something People Used To Do(tm), and now can't.  It does come up.
> >> Honestly if it had been done from day 0, it'd be a no-brainer I
> >> think.  Doing it now, with an incompat flag, might not be a
> >> reasonable tradeoff.
> > 
> > I think that labels are a far better way of dealing with this 
> > problem. Get rid of the UUID mount checking (and hence the nouuid 
> > mount option), and tell people to use by-label instead of by-uuid
> > to identify their filesystems when doing clones and snapshots.
> > Labels make it much easier for humans to identify the filesystem
> > than UUIDs...
> 
> As a plain user, I can say that I have needed to mount both the
> filesystem and its backup image, but Linux refused on the basis of the
> id being the same. Of course, all identifiers are the same, label and
> uuid.

Yes, that's the XFS UUID mount checking refusing to mount without the
"nouuid" mount option because of the duplicate UUID. XFS doesn't care
about whether there are duplicate labels or not, so removing the
UUID checking would solve your problem.

Cheers,

Dave.
-- 
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Re: Proposal/RFC: new metadata-specific UUID for V5 supers

[Eric Sandeen]

On 4/27/15 8:20 PM, Dave Chinner wrote:

> I think that labels are a far better way of dealing with this
> problem. Get rid of the UUID mount checking (and hence the nouuid
> mount option), and tell people to use by-label instead of by-uuid to
> identify their filesystems when doing clones and snapshots. Labels
> make it much easier for humans to identify the filesystem than
> UUIDs...

I suppose so.  Withdrawn.  ;)

-Eric

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Re: Proposal/RFC: new metadata-specific UUID for V5 supers

[Eric Sandeen]

On 4/27/15 9:06 PM, Eric Sandeen wrote:
> On 4/27/15 8:20 PM, Dave Chinner wrote:
> 
>> I think that labels are a far better way of dealing with this
>> problem. Get rid of the UUID mount checking (and hence the nouuid
>> mount option), and tell people to use by-label instead of by-uuid to
>> identify their filesystems when doing clones and snapshots. Labels
>> make it much easier for humans to identify the filesystem than
>> UUIDs...
> 
> I suppose so.  Withdrawn.  ;)

One more thought.  ;)

It'd be quite possible to keep defaults compatible with old kernels,
and only set the new feature if/when a user requests a UUID change.

If UUID changes are rare, it'll rarely matter; if they are required,
it'll be possible.  I might send a patch just to make the discussion
a bit more concrete.

Thanks,
-Eric

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Re: Proposal/RFC: new metadata-specific UUID for V5 supers

[Dave Chinner]

On Wed, Apr 29, 2015 at 01:38:53PM -0500, Eric Sandeen wrote:
> On 4/27/15 9:06 PM, Eric Sandeen wrote:
> > On 4/27/15 8:20 PM, Dave Chinner wrote:
> > 
> >> I think that labels are a far better way of dealing with this
> >> problem. Get rid of the UUID mount checking (and hence the nouuid
> >> mount option), and tell people to use by-label instead of by-uuid to
> >> identify their filesystems when doing clones and snapshots. Labels
> >> make it much easier for humans to identify the filesystem than
> >> UUIDs...
> > 
> > I suppose so.  Withdrawn.  ;)
> 
> One more thought.  ;)
> 
> It'd be quite possible to keep defaults compatible with old kernels,
> and only set the new feature if/when a user requests a UUID change.
> 
> If UUID changes are rare, it'll rarely matter; if they are required,
> it'll be possible.  I might send a patch just to make the discussion
> a bit more concrete.

Yes, we have precedence for doing things like that - v2 inodes,
attr2, etc. See what you come up with ;)

Cheers,

Dave.
-- 
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[PATCH RFC 1/2] xfs: add sb_meta_uuid field to superblock

[Eric Sandeen]

This patch creates a new, separate sb_meta_uuid field in the
superblock, which is used for comparison with all on-disk metadata.
It is separate from the main sb uuid which is user-visible, and
(with this patch, eventually) changeable.

This introduces an incompat feature; if the two UUIDs differ, we
must know to look to the meta_uuid for comparisons.  Older kernels
won't know to do this.

The bulk of this patch is simply changing sb_uuid to sb_meta_uuid
in all the verifiers etc.

If the new incompat flag isn't set, then we simply copy sb_uuid
into sb_meta_uuid when read from disk, and proceed as usual.

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

(for RFC purposes only, has only had smoke testing so far)

 libxfs/xfs_alloc.c          |    4 ++--
 libxfs/xfs_alloc_btree.c    |    4 ++--
 libxfs/xfs_attr_leaf.c      |    4 ++--
 libxfs/xfs_attr_remote.c    |    4 ++--
 libxfs/xfs_bmap_btree.c     |    4 ++--
 libxfs/xfs_btree.c          |    8 ++++----
 libxfs/xfs_da_btree.c       |    4 ++--
 libxfs/xfs_dir2_block.c     |    4 ++--
 libxfs/xfs_dir2_data.c      |    4 ++--
 libxfs/xfs_dir2_leaf.c      |    4 ++--
 libxfs/xfs_dir2_node.c      |    4 ++--
 libxfs/xfs_dquot_buf.c      |    4 ++--
 libxfs/xfs_format.h         |   18 ++++++++++++++----
 libxfs/xfs_ialloc.c         |    4 ++--
 libxfs/xfs_ialloc_btree.c   |    2 +-
 libxfs/xfs_inode_buf.c      |    4 ++--
 libxfs/xfs_sb.c             |    9 +++++++++
 libxfs/xfs_symlink_remote.c |    4 ++--
 xfs_dquot.c                 |    2 +-
 xfs_fsops.c                 |    6 +++---
 xfs_inode.c                 |    2 +-
 21 files changed, 61 insertions(+), 42 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_format.h b/fs/xfs/libxfs/xfs_format.h
index 8eb7189..5b90d7c 100644
--- a/fs/xfs/libxfs/xfs_format.h
+++ b/fs/xfs/libxfs/xfs_format.h
@@ -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 unique id */
 
 	/* must be padded to 64 bit alignment */
 } xfs_sb_t;
@@ -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 unique id */
 
 	/* must be padded to 64 bit alignment */
 } xfs_dsb_t;
@@ -283,7 +285,7 @@ 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;
 
@@ -315,6 +317,7 @@ 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		\
@@ -324,7 +327,7 @@ typedef enum {
 	 XFS_SB_ICOUNT | XFS_SB_IFREE | XFS_SB_FDBLOCKS | XFS_SB_FEATURES2 | \
 	 XFS_SB_FEATURES_COMPAT | XFS_SB_FEATURES_RO_COMPAT | \
 	 XFS_SB_FEATURES_INCOMPAT | XFS_SB_FEATURES_LOG_INCOMPAT | \
-	 XFS_SB_PQUOTINO)
+	 XFS_SB_PQUOTINO, XFS_SBS_META_UUID)
 
 
 /*
@@ -496,7 +499,7 @@ static inline void xfs_sb_version_addprojid32bit(struct xfs_sb *sbp)
  * can't be replayed on older kernels. The fields are set when the filesystem is
  * mounted, and a clean unmount clears the fields.
  */
-#define XFS_SB_FEAT_COMPAT_ALL 0
+#define XFS_SB_FEAT_COMPAT_ALL 		0
 #define XFS_SB_FEAT_COMPAT_UNKNOWN	~XFS_SB_FEAT_COMPAT_ALL
 static inline bool
 xfs_sb_has_compat_feature(
@@ -519,8 +522,10 @@ 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
@@ -568,6 +573,11 @@ static inline int xfs_sb_version_hasfinobt(xfs_sb_t *sbp)
 		(sbp->sb_features_ro_compat & XFS_SB_FEAT_RO_COMPAT_FINOBT);
 }
 
+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 b0a5fe9..6135440 100644
--- a/fs/xfs/libxfs/xfs_sb.c
+++ b/fs/xfs/libxfs/xfs_sb.c
@@ -385,6 +385,13 @@ __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);
@@ -526,6 +533,8 @@ 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);
+		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 a6fbf44..96b1b52 100644
--- a/fs/xfs/libxfs/xfs_alloc.c
+++ b/fs/xfs/libxfs/xfs_alloc.c
@@ -445,7 +445,7 @@ 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;
@@ -2197,7 +2197,7 @@ 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 15105db..d678495 100644
--- a/fs/xfs/libxfs/xfs_attr_leaf.c
+++ b/fs/xfs/libxfs/xfs_attr_leaf.c
@@ -186,7 +186,7 @@ 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;
@@ -979,7 +979,7 @@ 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..a1838dc 100644
--- a/fs/xfs/libxfs/xfs_bmap_btree.c
+++ b/fs/xfs/libxfs/xfs_bmap_btree.c
@@ -349,7 +349,7 @@ 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 +647,7 @@ 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 81cad43..59eecbf 100644
--- a/fs/xfs/libxfs/xfs_btree.c
+++ b/fs/xfs/libxfs/xfs_btree.c
@@ -65,7 +65,7 @@ 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 +115,7 @@ 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 +1000,7 @@ 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 +1013,7 @@ 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 9cb0115..112f3e9 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 5ff31be..7cdf69c 100644
--- a/fs/xfs/libxfs/xfs_dir2_data.c
+++ b/fs/xfs/libxfs/xfs_dir2_data.c
@@ -219,7 +219,7 @@ 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;
@@ -603,7 +603,7 @@ 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 116ef1d..a1c7ff0 100644
--- a/fs/xfs/libxfs/xfs_ialloc.c
+++ b/fs/xfs/libxfs/xfs_ialloc.c
@@ -307,7 +307,7 @@ 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 */
@@ -2047,7 +2047,7 @@ 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_sb.c b/fs/xfs/libxfs/xfs_sb.c
index b0a5fe9..6135440 100644
--- a/fs/xfs/libxfs/xfs_sb.c
+++ b/fs/xfs/libxfs/xfs_sb.c
@@ -385,6 +385,13 @@ __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);
@@ -526,6 +533,8 @@ 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);
+		memcpy(&to->sb_meta_uuid, &from->sb_meta_uuid,
+						sizeof(to->sb_meta_uuid));
 	}
 }
 
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 74efe5b..32a27d4 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 daafa1f..af8a12d 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -734,7 +734,7 @@ 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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Re: [PATCH RFC 1/2] xfs: add sb_meta_uuid field to superblock

[Eric Sandeen]

hohum, having done all that, it now occurs to me that perhaps
a simpler approach would be to add an sb_user_uuid in this same slot.

We could then set that to anything we want, with no other code changes,
and "all" we'd need is a blkid update to look there to see if it's set,
and some minor work in xfs_db to allow us to set it.  o_O

-Eric

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[PATCH RFC 2/2] xfsprogs: add support for sb_meta_uuid

[Eric Sandeen]

This adds userspace support for the new sb_meta_uuid field,
allowing us to change the user-visible UUID if needed.

If xfs_db changes the uuid, and we have CRCs (and hence metadata
UUID checking), and we don't have the incompatible meta_uuid
feature set, it will copy the primary uuid to the meta uuid and
set the incompat flag, then change the primary uuid as requested.

The bulk of the patch is simply changing comparisons from sb_uuid
to sb_meta_uuid.  If the feature isn't set, we populate the latter
with the former when reading the superblock from disk.

xfs_copy support is still missing.

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

(for RFC purposes only, has only had smoke testing so far)

 db/sb.c                     |   27 ++++++++++++++-------------
 include/xfs_sb.h            |   17 ++++++++++++++---
 libxfs/util.c               |    2 +-
 libxfs/xfs_alloc.c          |    4 ++--
 libxfs/xfs_alloc_btree.c    |    4 ++--
 libxfs/xfs_attr_leaf.c      |    4 ++--
 libxfs/xfs_attr_remote.c    |    4 ++--
 libxfs/xfs_bmap_btree.c     |    4 ++--
 libxfs/xfs_btree.c          |    8 ++++----
 libxfs/xfs_da_btree.c       |    4 ++--
 libxfs/xfs_dir2_block.c     |    4 ++--
 libxfs/xfs_dir2_data.c      |    4 ++--
 libxfs/xfs_dir2_leaf.c      |    4 ++--
 libxfs/xfs_dir2_node.c      |    4 ++--
 libxfs/xfs_dquot_buf.c      |    4 ++--
 libxfs/xfs_ialloc.c         |    4 ++--
 libxfs/xfs_ialloc_btree.c   |    2 +-
 libxfs/xfs_inode_buf.c      |    2 +-
 libxfs/xfs_sb.c             |    9 +++++++++
 libxfs/xfs_symlink_remote.c |    4 ++--
 repair/agheader.c           |   13 ++++++++-----
 repair/dinode.c             |    6 +++---
 repair/phase5.c             |    6 +++---
 repair/phase6.c             |    6 +++---
 24 files changed, 87 insertions(+), 63 deletions(-)

diff --git a/db/sb.c b/db/sb.c
index 23ec87c..42e34f9 100644
--- a/db/sb.c
+++ b/db/sb.c
@@ -121,6 +121,7 @@ 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 +325,7 @@ 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 +335,16 @@ do_uuid(xfs_agnumber_t agno, uuid_t *uuid)
 		pop_cur();
 		return &uu;
 	}
+	if (xfs_sb_version_hascrc(&tsb) &&
+	    !xfs_sb_version_hasmetauuid(&tsb)) {
+		memcpy(&tsb.sb_meta_uuid, &tsb.sb_uuid, sizeof(uuid_t));
+		tsb.sb_features_incompat |= XFS_SB_FEAT_INCOMPAT_META_UUID;
+		mp->m_sb.sb_features_incompat |= XFS_SB_FEAT_INCOMPAT_META_UUID;
+		fields |= XFS_SB_META_UUID | XFS_SB_FEATURES_INCOMPAT;
+	}
 	/* set uuid */
 	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 +372,6 @@ 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")) {
@@ -658,6 +655,10 @@ version_string(
 		strcat(s, ",CRC");
 	if (xfs_sb_version_hasftype(sbp))
 		strcat(s, ",FTYPE");
+	if (xfs_sb_version_hasfinobt(sbp))
+		strcat(s, ",FINOBT");
+	if (xfs_sb_version_hasmetauuid(sbp))
+		strcat(s, ",META_UUID");
 	return s;
 }
 
diff --git a/include/xfs_sb.h b/include/xfs_sb.h
index 950d1ea..41b54ce 100644
--- a/include/xfs_sb.h
+++ b/include/xfs_sb.h
@@ -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 unique id */
 
 	/* must be padded to 64 bit alignment */
 } xfs_sb_t;
@@ -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 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
@@ -649,6 +654,12 @@ static inline int xfs_sb_version_hasfinobt(xfs_sb_t *sbp)
 		(sbp->sb_features_ro_compat & XFS_SB_FEAT_RO_COMPAT_FINOBT);
 }
 
+static inline int xfs_sb_version_hasmetauuid(xfs_sb_t *sbp)
+{
+	return (XFS_SB_VERSION_NUM(sbp) == XFS_SB_VERSION_5) &&
+		xfs_sb_has_incompat_feature(sbp, 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..96d20c1 100644
--- a/libxfs/xfs_bmap_btree.c
+++ b/libxfs/xfs_bmap_btree.c
@@ -412,7 +412,7 @@ 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 +712,7 @@ 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..d3df341 100644
--- a/libxfs/xfs_btree.c
+++ b/libxfs/xfs_btree.c
@@ -50,7 +50,7 @@ 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 +100,7 @@ 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 +992,7 @@ 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 +1005,7 @@ 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..da09ae7 100644
--- a/libxfs/xfs_ialloc.c
+++ b/libxfs/xfs_ialloc.c
@@ -295,7 +295,7 @@ 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 +1947,7 @@ 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..22404e6 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 +414,14 @@ 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
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/repair/agheader.c b/repair/agheader.c
index 5dbf992..2f307e7 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 +120,7 @@ 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 +190,7 @@ 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 +198,7 @@ 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;
@@ -267,7 +267,10 @@ 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))
diff --git a/repair/dinode.c b/repair/dinode.c
index 035212c..83804ce 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 +2366,7 @@ _("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);


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