| Message ID | 20231108083228.1278837-3-chandan.babu@oracle.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | xfsdocs: Describe Metadump V2's ondisk format structure | expand |
On Wed, Nov 08, 2023 at 02:02:28PM +0530, Chandan Babu R wrote: > 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@oracle.com> This is consistent with the C structures in the metadump2 patchset, so Reviewed-by: Darrick J. Wong <djwong@kernel.org> (But I'll wait until cem merges that patchset before taking this.) ((Assuming I'm still xfs-docs maintainer :P)) (((Ok I declare I still am))) --D > --- > .../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..7ce993c 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 > +capturing 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 metadata blocks have been dumped. Without this flag, unused areas > +of metadata blocks are zeroed. > + > +| +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 lower 54 bits are used to store the disk address of a metadata dump > +extent. The next 2 bits are used for indicating the device. > +. 00 - Data device > +. 01 - External log > + > +*xme_len*:: > +Length of the metadata dump extent in units of 512 byte blocks. > + > == Dump Obfuscation > > Unless explicitly disabled, the +xfs_metadump+ tool obfuscates empty block > -- > 2.39.1 >
diff --git a/design/XFS_Filesystem_Structure/metadump.asciidoc b/design/XFS_Filesystem_Structure/metadump.asciidoc index 2f35b7e..7ce993c 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 +capturing 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 metadata blocks have been dumped. Without this flag, unused areas +of metadata blocks are zeroed. + +| +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 lower 54 bits are used to store the disk address of a metadata dump +extent. The next 2 bits are used for indicating the device. +. 00 - Data device +. 01 - External log + +*xme_len*:: +Length of the metadata dump extent in units of 512 byte blocks. + == Dump Obfuscation Unless explicitly disabled, the +xfs_metadump+ tool obfuscates empty block
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@oracle.com> --- .../metadump.asciidoc | 75 ++++++++++++++++++- 1 file changed, 74 insertions(+), 1 deletion(-)