From patchwork Wed Nov 6 19:19:09 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Darrick J. Wong" X-Patchwork-Id: 13865340 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0B97320BB2D for ; Wed, 6 Nov 2024 19:19:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730920751; cv=none; b=Aj2J0wHhdL20QJyYnfmHMPzJjLqRoxKB6STKXyw5D4MgMJmPoxM129k9dEhQMX8LbZN9DMcLO00K5qFFkVC26LTDtDXH29jTL64jcMH/zhGv2zhEqo1XKw7T9LGlpVoMuw73SCFGCNZUqFG6rM4JUEqXLpE6zQq5/FbjWjKnCks= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730920751; c=relaxed/simple; bh=0TEuBroQb0AYJtk98GiasfrVtsc/5apa9k7zzEoXx8Q=; h=Date:Subject:From:To:Cc:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=UeCBnUIhgWeDHZfb9z9Lxy5zTqpviZ8NwRKJJqaP88ehaPdBw4d0AHMQd0brHI/Gli2pHYYPKV5Q4Yr69sROL44cf2MHzHhfiQlQD35yNDwZyq0Z+Odh8Ws0FH87tymJnQm/LRFeW5/mL3wMNbjJYnfU8MByaiA66yDvIW7nms4= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=m0DdyhBa; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="m0DdyhBa" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8827BC4CEC6; Wed, 6 Nov 2024 19:19:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1730920750; bh=0TEuBroQb0AYJtk98GiasfrVtsc/5apa9k7zzEoXx8Q=; h=Date:Subject:From:To:Cc:In-Reply-To:References:From; b=m0DdyhBal62t8jXnwPdXFniKTgDf7Fa2/mJJjDtVVjScikQaEYZhp/VlwJO2nQW90 nV3BErCgBRjuzGsPcZjTFRqDAWvIZ9lelCpFow0vmey0H4Yfsht4QRJ5ol8XYXnJ/n yTjivMGM4GCDyMAo0MRPlLKzwLOVbqraDOYV389SoeUPjIjMqz7s69M/ARkj6/+iou Mc5V2j+Xd/sHbZWZQJNsU+SbfxRa0AfMpc+wdKwnWa09sK/DcZt+PvYPEpaRMo1452 VoxoeiQQdOJ1Mej07Ct5Iqjn8nzYEfSDsEUwpWrWalJ++HbutNqR2tlLpUUPSGLCWZ H2R5FYvcn8Hkw== Date: Wed, 06 Nov 2024 11:19:09 -0800 Subject: [PATCH 2/4] design: document realtime groups From: "Darrick J. Wong" To: djwong@kernel.org Cc: linux-xfs@vger.kernel.org, hch@lst.de Message-ID: <173092059729.2883258.3327326591290447581.stgit@frogsfrogsfrogs> In-Reply-To: <173092059696.2883258.7093773656482973762.stgit@frogsfrogsfrogs> References: <173092059696.2883258.7093773656482973762.stgit@frogsfrogsfrogs> Precedence: bulk X-Mailing-List: linux-xfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 From: Darrick J. Wong Document the ondisk changes for realtime allocation groups. Signed-off-by: Darrick J. Wong --- .../allocation_groups.asciidoc | 31 ++ .../XFS_Filesystem_Structure/common_types.asciidoc | 4 .../internal_inodes.asciidoc | 2 design/XFS_Filesystem_Structure/magic.asciidoc | 3 .../XFS_Filesystem_Structure/ondisk_inode.asciidoc | 2 design/XFS_Filesystem_Structure/realtime.asciidoc | 344 ++++++++++++++++++++ 6 files changed, 385 insertions(+), 1 deletion(-) diff --git a/design/XFS_Filesystem_Structure/allocation_groups.asciidoc b/design/XFS_Filesystem_Structure/allocation_groups.asciidoc index 5d560073d146ff..9f92be49a7a095 100644 --- a/design/XFS_Filesystem_Structure/allocation_groups.asciidoc +++ b/design/XFS_Filesystem_Structure/allocation_groups.asciidoc @@ -106,6 +106,10 @@ struct xfs_sb xfs_lsn_t sb_lsn; uuid_t sb_meta_uuid; xfs_ino_t sb_metadirino; + xfs_rgnumber_t sb_rgcount; + xfs_rgblock_t sb_rgextents; + uint8_t sb_rgblklog; + uint8_t sb_pad[7]; }; ---- *sb_magicnum*:: @@ -413,6 +417,12 @@ to have a slightly higher level of redundancy over the shape of the inode btrees, and decreases the amount of time to compute the metadata B+tree preallocations at mount time. +| +XFS_SB_FEAT_RO_COMPAT_RTSB+ | +Realtime superblock. The first rt extent in rt group zero contains a superblock +header that can be used to identify the realtime device. See the section about +the xref:Realtime_Group_Superblocks[realtime group superblocks] for more +information. + |===== *sb_features_incompat*:: @@ -476,6 +486,10 @@ pointers] for more information. Metadata directory tree. See the section about the xref:Metadata_Directories[ metadata directory tree] for more information. +| +XFS_SB_FEAT_INCOMPAT_RTGROUPS+ | +Realtime allocation groups. See the section about the xref:Realtime_Groups[ +realtime groups] for more information. + |===== *sb_features_log_incompat*:: @@ -514,6 +528,23 @@ If the +XFS_SB_FEAT_RO_INCOMPAT_METADIR+ feature is set, this field points to the inode of the root directory of the metadata directory tree. This field is zero otherwise. +*sb_rgcount*:: +Count of realtime groups in the filesystem, if the ++XFS_SB_FEAT_INCOMPAT_RTGROUPS+ feature is enabled. + +*sb_rgextents*:: +Maximum number of realtime extents that can be contained within a realtime +group, if the +XFS_SB_FEAT_INCOMPAT_RTGROUPS+ feature is enabled. + +*sb_rgblklog*:: +If the +XFS_SB_FEAT_INCOMPAT_RTGROUPS+ feature is enabled, this is the log~2~ +value of +sb_rgextents+ * +sb_rextsize+ (rounded up). This value is used to +generate absolute block numbers defined in extent maps from the segmented ++xfs_rtblock_t+ values. + +*sb_pad[7]*:: +Zeroes, if the +XFS_SB_FEAT_INCOMPAT_RTGROUPS+ feature is enabled. + === xfs_db Superblock Example A filesystem is made on a single disk with the following command: diff --git a/design/XFS_Filesystem_Structure/common_types.asciidoc b/design/XFS_Filesystem_Structure/common_types.asciidoc index 51909be384e273..34cdfdaeccf848 100644 --- a/design/XFS_Filesystem_Structure/common_types.asciidoc +++ b/design/XFS_Filesystem_Structure/common_types.asciidoc @@ -43,7 +43,9 @@ Unsigned 64 bit raw filesystem block number. *xfs_rtblock_t*:: Unsigned 64 bit extent number in the xref:Real-time_Devices[real-time] -sub-volume. +sub-volume. If the +XFS_SB_FEAT_INCOMPAT_METADIR+ feature is enabled, these +values combine an xref:Realtime_Groups[rtgroup number] and block offset into +the realtime group. *xfs_fileoff_t*:: Unsigned 64 bit block offset into a file. diff --git a/design/XFS_Filesystem_Structure/internal_inodes.asciidoc b/design/XFS_Filesystem_Structure/internal_inodes.asciidoc index 68c86d30ff8206..5f4d62201cbd67 100644 --- a/design/XFS_Filesystem_Structure/internal_inodes.asciidoc +++ b/design/XFS_Filesystem_Structure/internal_inodes.asciidoc @@ -21,6 +21,8 @@ of those inodes have been deallocated and may be reused by future features. [options="header"] |===== | Metadata File | Location +| xref:Real-Time_Bitmap_Inode[Realtime Bitmap] | /rtgroups/*.bitmap +| xref:Real-Time_Summary_Inode[Realtime Summary] | /rtgroups/*.summary |===== Metadata files are flagged by the +XFS_DIFLAG2_METADATA+ flag in the diff --git a/design/XFS_Filesystem_Structure/magic.asciidoc b/design/XFS_Filesystem_Structure/magic.asciidoc index 60952aeb876ff5..5da29b9ef9f3a8 100644 --- a/design/XFS_Filesystem_Structure/magic.asciidoc +++ b/design/XFS_Filesystem_Structure/magic.asciidoc @@ -45,9 +45,12 @@ relevant chapters. Magic numbers tend to have consistent locations: | +XFS_ATTR3_LEAF_MAGIC+ | 0x3bee | | xref:Leaf_Attributes[Leaf Attribute], v5 only | +XFS_ATTR3_RMT_MAGIC+ | 0x5841524d | XARM | xref:Remote_Values[Remote Attribute Value], v5 only | +XFS_RMAP_CRC_MAGIC+ | 0x524d4233 | RMB3 | xref:Reverse_Mapping_Btree[Reverse Mapping B+tree], v5 only +| +XFS_RTBITMAP_MAGIC+ | 0x424D505A | BMPZ | xref:Real-Time_Bitmap_Inode[Real-Time Bitmap], metadir only +| +XFS_RTSUMMARY_MAGIC+ | 0x53554D59 | SUMY | xref:Real-Time_Summary_Inode[Real-Time Summary], metadir only | +XFS_RTRMAP_CRC_MAGIC+ | 0x4d415052 | MAPR | xref:Real_time_Reverse_Mapping_Btree[Real-Time Reverse Mapping B+tree], v5 only | +XFS_REFC_CRC_MAGIC+ | 0x52334643 | R3FC | xref:Reference_Count_Btree[Reference Count B+tree], v5 only | +XFS_MD_MAGIC+ | 0x5846534d | XFSM | xref:Metadata_Dumps[Metadata Dumps] +| +XFS_RTSB_MAGIC+ | 0x46726F67 | Frog | xref:Realtime_Groups[Realtime Groups] |===== The magic numbers for log items are at offset zero in each log item, but items diff --git a/design/XFS_Filesystem_Structure/ondisk_inode.asciidoc b/design/XFS_Filesystem_Structure/ondisk_inode.asciidoc index 02ec0d12bb57e5..e28929907147b7 100644 --- a/design/XFS_Filesystem_Structure/ondisk_inode.asciidoc +++ b/design/XFS_Filesystem_Structure/ondisk_inode.asciidoc @@ -199,6 +199,8 @@ directory tree. [source, c] ---- enum xfs_metafile_type { + XFS_METAFILE_RTBITMAP, + XFS_METAFILE_RTSUMMARY, }; ---- diff --git a/design/XFS_Filesystem_Structure/realtime.asciidoc b/design/XFS_Filesystem_Structure/realtime.asciidoc index 11426e8fdb632d..3a72eb5175ad89 100644 --- a/design/XFS_Filesystem_Structure/realtime.asciidoc +++ b/design/XFS_Filesystem_Structure/realtime.asciidoc @@ -31,6 +31,146 @@ and bits per byte. This value is stored in +sb_rbmblocks+. The nblocks and extent array for the inode should match this. Each real time block gets its own bit in the bitmap. +If the +XFS_SB_FEAT_INCOMPAT_METADIR+ feature is enabled, each block of the +realtime bitmap file has a header of the following format: + +[source, c] +---- +struct xfs_rtbuf_blkinfo { + __be32 rt_magic; + __be32 rt_crc; + __be64 rt_owner; + __be64 rt_blkno; + __be64 rt_lsn; + uuid_t rt_uuid; +}; +---- + +*rt_magic*:: +Specifies the magic number for the rtbitmap block: ``BMPZ'' (0x424D505A). + +*rt_crc*:: +Checksum of the block. + +*rt_owner*:: +Specifies the inode number for the file that owns this block. + +*rt_blkno*:: +Disk address of this block. + +*rt_lsn*:: +Log sequence number of the last write to this block. + +*rt_uuid*:: +The UUID of this block, which must match either +sb_uuid+ or +sb_meta_uuid+ +depending on which features are set. + +After the block header, the bitmap data are encoded as be32 word values. + +=== xfs_db rtbitmap Example + +This example shows a real-time bitmap file from a freshly populated filesystem: + +---- +xfs_db> path -m /rtgroups/3.bitmap +xfs_db> p +core.magic = 0x494e +core.mode = 0100000 +core.version = 3 +core.format = 2 (extents) +core.metatype = 5 (rtbitmap) +core.uid = 0 +core.gid = 0 +core.nlinkv2 = 1 +core.projid_lo = 3 +core.projid_hi = 0 +core.nextents = 1 +core.atime.sec = Tue Oct 15 16:04:02 2024 +core.atime.nsec = 769675000 +core.mtime.sec = Tue Oct 15 16:04:02 2024 +core.mtime.nsec = 769675000 +core.ctime.sec = Tue Oct 15 16:04:02 2024 +core.ctime.nsec = 769681000 +core.size = 135168 +core.nblocks = 33 +core.extsize = 0 +core.naextents = 0 +core.forkoff = 24 +core.aformat = 1 (local) +core.dmevmask = 0 +core.dmstate = 0 +core.newrtbm = 0 +core.prealloc = 0 +core.realtime = 0 +core.immutable = 1 +core.append = 0 +core.sync = 1 +core.noatime = 1 +core.nodump = 1 +core.rtinherit = 0 +core.projinherit = 0 +core.nosymlinks = 0 +core.extsz = 0 +core.extszinherit = 0 +core.nodefrag = 1 +core.filestream = 0 +core.gen = 2653591217 +next_unlinked = null +v3.crc = 0x34a17119 (correct) +v3.change_count = 3 +v3.lsn = 0 +v3.flags2 = 0x38 +v3.cowextsize = 0 +v3.crtime.sec = Tue Oct 15 16:04:02 2024 +v3.crtime.nsec = 769675000 +v3.inumber = 33685633 +v3.uuid = a6575f59-1514-445e-883e-211b2c5a0f05 +v3.reflink = 0 +v3.cowextsz = 0 +v3.dax = 0 +v3.bigtime = 1 +v3.nrext64 = 1 +v3.metadata = 1 +u3.bmx[0] = [startoff,startblock,blockcount,extentflag] +0:[0,4210712,33,0] +a.sfattr.hdr.totsize = 27 +a.sfattr.hdr.count = 1 +a.sfattr.list[0].namelen = 8 +a.sfattr.list[0].valuelen = 12 +a.sfattr.list[0].root = 0 +a.sfattr.list[0].secure = 0 +a.sfattr.list[0].parent = 1 +a.sfattr.list[0].name = "0.bitmap" +a.sfattr.list[0].parent_dir.inumber = 33685632 +a.sfattr.list[0].parent_dir.gen = 142228546 +xfs_db> dblock 0 +xfs_db> p +magicnum = 0x424d505a +crc = 0xc8b10abf (correct) +owner = 33685633 +bno = 20902080 +lsn = 0x100007696 +uuid = a6575f59-1514-445e-883e-211b2c5a0f05 +rtwords[0-1011] = 0:0 1:0 2:0 3:0 4:0 5:0 6:0 7:0 8:0 9:0 10:0 11:0 12:0 13:0 +14:0 15:0 16:0 17:0 18:0 19:0 20:0 21:0xfffff800 22:0xffffffff 23:0xffffffff +24:0xffffffff 25:0xffffffff 26:0xffffffff 27:0xffffffff 28:0xffffffff +29:0xffffffff 30:0xffffffff 31:0xffffffff 32:0xffffffff +... +979:0xffffffff 980:0xffffffff 981:0xffffffff 982:0xffffffff 983:0xffffffff +984:0xffffffff 985:0xffffffff 986:0xffffffff 987:0xffffffff 988:0xffffffff +989:0xffffffff 990:0xffffffff 991:0xffffffff 992:0xffffffff 993:0xffffffff +994:0xffffffff 995:0xffffffff 996:0xffffffff 997:0xffffffff 998:0xffffffff +999:0xffffffff 1000:0xffffffff 1001:0xffffffff 1002:0xffffffff 1003:0xffffffff +1004:0xffffffff 1005:0xffffffff 1006:0xffffffff 1007:0xffffffff 1008:0xffffffff +1009:0xffffffff 1010:0xffffffff 1011:0xffffffff +---- + +From this example, we can clearly see that this is a bitmap file in the +metadata directory tree, and that it is the bitmap file for rtgroup 3. When we +access the first block in the bitmap file, we can clearly see the new block +header and that the first 179 extents are allocated. The bitmap words were +excerpted for brevity. + [[Real-Time_Summary_Inode]] == Free Space Summary Inode @@ -47,4 +187,208 @@ This data structure is not particularly space efficient, however it is a very fast way to provide the same data as the two free space B+trees for regular files since the space is preallocated and metadata maintenance is minimal. +If the +XFS_SB_FEAT_INCOMPAT_METADIR+ feature is enabled, each block of the +realtime summary file has the same header as rtbitmap file blocks. However, +the magic number will be ``SUMY'' (0x53554D59). After the block header, the +summary counts are encoded as be32 integers. + +=== xfs_db rtsummary Example + +This example shows a real-time summary file from a freshly populated filesystem: + +---- +xfs_db> path -m /rtgroups/3.summary +xfs_db> p +core.magic = 0x494e +core.mode = 0100000 +core.version = 3 +core.format = 2 (extents) +core.metatype = 6 (rtsummary) +core.uid = 0 +core.gid = 0 +core.nlinkv2 = 1 +core.projid_lo = 3 +core.projid_hi = 0 +core.nextents = 1 +core.atime.sec = Tue Oct 15 16:04:02 2024 +core.atime.nsec = 769694000 +core.mtime.sec = Tue Oct 15 16:04:02 2024 +core.mtime.nsec = 769694000 +core.ctime.sec = Tue Oct 15 16:04:02 2024 +core.ctime.nsec = 769699000 +core.size = 4096 +core.nblocks = 1 +core.extsize = 0 +core.naextents = 0 +core.forkoff = 24 +core.aformat = 1 (local) +core.dmevmask = 0 +core.dmstate = 0 +core.newrtbm = 0 +core.prealloc = 0 +core.realtime = 0 +core.immutable = 1 +core.append = 0 +core.sync = 1 +core.noatime = 1 +core.nodump = 1 +core.rtinherit = 0 +core.projinherit = 0 +core.nosymlinks = 0 +core.extsz = 0 +core.extszinherit = 0 +core.nodefrag = 1 +core.filestream = 0 +core.gen = 519466891 +next_unlinked = null +v3.crc = 0x54fc58d0 (correct) +v3.change_count = 3 +v3.lsn = 0 +v3.flags2 = 0x38 +v3.cowextsize = 0 +v3.crtime.sec = Tue Oct 15 16:04:02 2024 +v3.crtime.nsec = 769694000 +v3.inumber = 33685634 +v3.uuid = a6575f59-1514-445e-883e-211b2c5a0f05 +v3.reflink = 0 +v3.cowextsz = 0 +v3.dax = 0 +v3.bigtime = 1 +v3.nrext64 = 1 +v3.metadata = 1 +u3.bmx[0] = [startoff,startblock,blockcount,extentflag] +0:[0,4210703,1,0] +a.sfattr.hdr.totsize = 28 +a.sfattr.hdr.count = 1 +a.sfattr.list[0].namelen = 9 +a.sfattr.list[0].valuelen = 12 +a.sfattr.list[0].root = 0 +a.sfattr.list[0].secure = 0 +a.sfattr.list[0].parent = 1 +a.sfattr.list[0].name = "0.summary" +a.sfattr.list[0].parent_dir.inumber = 33685632 +a.sfattr.list[0].parent_dir.gen = 142228546 +xfs_db> dblock 0 +xfs_db> p +magicnum = 0x53554d59 +crc = 0x473340a8 (correct) +owner = 33685634 +bno = 20902008 +lsn = 0x100007696 +uuid = a6575f59-1514-445e-883e-211b2c5a0f05 +suminfo[0-1011] = 0:0 1:0 2:0 3:0 4:0 5:0 6:0 7:0 8:0 9:0 10:0 11:0 12:0 13:0 +14:0 15:0 16:0 17:0 18:0 19:0 20:0 21:0 22:0 23:0 24:0 25:0 26:0 27:0 28:0 29:0 +30:0 31:0 32:0 +... +618:0 619:0 620:0 621:0 622:0 623:0 624:0 625:0 626:0 627:1 628:0 629:0 630:0 +... +979:0 980:0 981:0 982:0 983:0 984:0 985:0 986:0 987:0 988:0 989:0 990:0 991:0 +992:0 993:0 994:0 995:0 996:0 997:0 998:0 999:0 1000:0 1001:0 1002:0 1003:0 +1004:0 1005:0 1006:0 1007:0 1008:0 1009:0 1010:0 1011:0 +---- + +From this example, we can clearly see that this is a summary file in the +metadata directory tree, and that it is the summary file for rtgroup 3. When +we access the first block in the summary file, we can clearly see the new block +header and the nonzero counter for the one large free extent in this group. +The summary counts were excerpted for brevity. + +[[Realtime_Groups]] +== Realtime Groups + +To reduce metadata contention for space allocation and remapping activities +being applied to realtime files, the realtime volume can be split into +allocation groups, just like the data volume. The free space information is +still contained in a single file that applies to the entire volume. + +Each realtime allocation group can contain up to (2^31^ - 1) filesystem blocks, +regardless of the underlying realtime extent size. + +Each realtime group has the following characteristics: + + * Group 0 has a super block describing overall filesystem info + * Free space bitmap + * Summary of free space + +The free space metadata are the same as described in the previous sections, +except that their scope covers only a single rtgroup. The other structures are +expanded upon in the following sections. + +[[Realtime_Group_Superblocks]] +=== Superblocks + +The first block of each realtime group contains a superblock. These fields +must match their counterparts in the filesystem superblock on the data device. + +[source, c] +---- +struct xfs_rtsb { + __be32 rsb_magicnum; + __le32 rsb_crc; + + __be32 rsb_pad; + unsigned char rsb_fname[XFSLABEL_MAX]; + + uuid_t rsb_uuid; + uuid_t rsb_meta_uuid; + + /* must be padded to 64 bit alignment */ +}; +---- + +*rsb_magicnum*:: +Identifies the filesystem. Its value is +XFS_RTSB_MAGIC+ ``Frog'' (0x46726F67). + +*rsb_crc*:: +Superblock checksum. + +*rsb_pad*:: +Must be zero. + +*rsb_fname[12]*:: +Name for the filesystem. This matches +sb_fname+ in the primary superblock. + +*rsb_uuid*:: +UUID (Universally Unique ID) for the filesystem. This matches +sb_uuid+ in the +primary superblock. + +*rsb_meta_uuid*:: +Metadata UUID for the filesystem. This matches +sb_meta_uuid+ in the primary +superblock. + +==== xfs_db rtgroup Superblock Example + +A filesystem is made on a multidisk filesystem with the following command: + +---- +# mkfs.xfs -r rtgroups=1,rgcount=4,rtdev=/dev/sdb /dev/sda -f +meta-data=/dev/sda isize=512 agcount=4, agsize=1298176 blks + = sectsz=512 attr=2, projid32bit=1 + = crc=1 finobt=1, sparse=1, rmapbt=1 + = reflink=1 bigtime=1 inobtcount=1 nrext64=1 + = metadir=1 +data = bsize=4096 blocks=5192704, imaxpct=25 + = sunit=0 swidth=0 blks +naming =version 2 bsize=4096 ascii-ci=0, ftype=1 +log =internal log bsize=4096 blocks=16384, version=2 + = sectsz=512 sunit=0 blks, lazy-count=1 +realtime =/dev/sdb extsz=4096 blocks=5192704, rtextents=5192704 + = rgcount=5 rgsize=1048576 extents +---- + +And in xfs_db, inspecting the realtime group superblock and then the regular +superblock: + +---- +# xfs_db -R /dev/sdb /dev/sda +xfs_db> rtsb +xfs_db> print +magicnum = 0x46726f67 +crc = 0x759a62d4 (correct) +pad = 0 +fname = "\000\000\000\000\000\000\000\000\000\000\000\000" +uuid = 7e55b909-8728-4d69-a1fa-891427314eea +meta_uuid = 7e55b909-8728-4d69-a1fa-891427314eea +---- + include::rtrmapbt.asciidoc[]