Metadump v2 is the new metadata dump format introduced in upstream
xfsprogs. This commit describes V2 format's ondisk structure.
Signed-off-by: Chandan Babu R <chandan.babu@xxxxxxxxxx>
---
.../metadump.asciidoc | 75 ++++++++++++++++++-
1 file changed, 74 insertions(+), 1 deletion(-)
diff --git a/design/XFS_Filesystem_Structure/metadump.asciidoc b/design/XFS_Filesystem_Structure/metadump.asciidoc
index 2f35b7e..782f194 100644
--- a/design/XFS_Filesystem_Structure/metadump.asciidoc
+++ b/design/XFS_Filesystem_Structure/metadump.asciidoc
@@ -13,7 +13,11 @@ must be the superblock from AG 0. If the metadump has more blocks than
can be pointed to by the +xfs_metablock.mb_daddr+ area, the sequence
of +xfs_metablock+ followed by metadata blocks is repeated.
-.Metadata Dump Format
+Two metadump file formats are supported: +V1+ and +V2+. In addition to
+the features supported by the +V1+ format, the +V2+ format supports
+dumping data from an external log device.
+
+== Metadata Dump v1 Format
[source, c]
----
@@ -62,6 +66,75 @@ An array of disk addresses. Each of the +mb_count+ blocks (of size +(1
<< mb_blocklog+) following the +xfs_metablock+ should be written back to
the address pointed to by the corresponding +mb_daddr+ entry.
+== Metadata Dump v2 Format
+
+A Metadump Dump in the V2 format begins with a header represented by
++struct xfs_metadump_header+.
+[source, c]
+----
+struct xfs_metadump_header {
+ __be32 xmh_magic;
+ __be32 xmh_version;
+ __be32 xmh_compat_flags;
+ __be32 xmh_incompat_flags;
+ __be64 xmh_reserved;
+} __packed;
+----
+*xmh_magic*::
+The magic number, ``XMD2'' (0x584D4432)
+
+*xmh_version*::
+The version number, i.e. 2.
+
+*xmh_compat flags*::
+Compat flags describing a metadata dump.
+
+[options="header"]
+|=====
+| Flag | Description
+| +XFS_MD2_COMPAT_OBFUSCATED+ |
+Directory entry and extended attribute names have been obscured and
+extended attribute values are zeroed to protect privacy.
+
+| +XFS_MD2_COMPAT_FULLBLOCKS+ |
+Full blocks have been dumped.
+
+| +XFS_MD2_COMPAT_DIRTYLOG+ |
+Log was dirty.
+
+| +XFS_MD2_COMPAT_EXTERNALLOG+ |
+Metadata dump contains contents from an external log.
+|=====
+
+*xmh_incompat_flags*::
+Incompat flags describing a metadata dump. At present, this field must
+be set to zero.
+
+*xmh_reserved*::
+Reserved. Should be zero.
+
+The header is followed by an alternating sequence of +struct
+xfs_meta_extent+ and the contents from the corresponding variable
+length extent.
+
+[source, c]
+----
+struct xfs_meta_extent {
+ __be64 xme_addr;
+ __be32 xme_len;
+} __packed;
+----
+*xme_addr*::
+
+
+The lowest 54 bits are used to store 512 byte disk addresses of a
+metadata extent . The next 2 bits are used for indicating the device.
+. 00 - Data device
+. 01 - External log
+
+*xme_len*::
+Length of the Metadata in units of 512 byte blocks.
+
== Dump Obfuscation
Unless explicitly disabled, the +xfs_metadump+ tool obfuscates empty block
--
2.39.1
