From: Darrick J. Wong <djwong@xxxxxxxxxx> Document the ondisk format changes for metadata directories. Signed-off-by: Darrick J. Wong <djwong@xxxxxxxxxx> --- .../allocation_groups.asciidoc | 23 +++ .../internal_inodes.asciidoc | 142 ++++++++++++++++++++ .../XFS_Filesystem_Structure/ondisk_inode.asciidoc | 5 + 3 files changed, 165 insertions(+), 5 deletions(-) diff --git a/design/XFS_Filesystem_Structure/allocation_groups.asciidoc b/design/XFS_Filesystem_Structure/allocation_groups.asciidoc index 7b128838..c91a06bf 100644 --- a/design/XFS_Filesystem_Structure/allocation_groups.asciidoc +++ b/design/XFS_Filesystem_Structure/allocation_groups.asciidoc @@ -142,10 +142,13 @@ start of the first possible inode chunk in AG 0. This is 128 when using a 4KB block size. *sb_rbmino*:: -Bitmap inode for real-time extents. +Bitmap inode for real-time extents if the +XFS_SB_FEAT_INCOMPAT_METADIR+ +feature is not enabled. If the metadir feature is enabled, this field points +to the inode for the root of the metadata directory tree. *sb_rsumino*:: -Summary inode for real-time bitmap. +Summary inode for real-time bitmap if the +XFS_SB_FEAT_INCOMPAT_METADIR+ +feature is not enabled. *sb_rextsize*:: Realtime extent size in blocks. @@ -262,12 +265,16 @@ maintained in the first superblock. *sb_uquotino*:: Inode for user quotas. This and the following two quota fields only apply if +XFS_SB_VERSION_QUOTABIT+ flag is set in +sb_versionnum+. Refer to -xref:Quota_Inodes[quota inodes] for more information. +xref:Quota_Inodes[quota inodes] for more information. If the ++XFS_SB_FEAT_INCOMPAT_METADIR+ feature is enabled, the user quota file is found +through the metadata directory tree and this field must be zero. *sb_gquotino*:: Inode for group or project quotas. Group and project quotas cannot be used at the same time on v4 filesystems. On a v5 filesystem, this inode always stores -group quota information. +group quota information. If the +XFS_SB_FEAT_INCOMPAT_METADIR+ feature is +enabled, the group quota file is found through the metadata directory tree and +this field must be zero. *sb_qflags*:: Quota flags. It can be a combination of the following flags: @@ -458,6 +465,10 @@ xfs_repair before it can be mounted. Large file fork extent counts. This greatly expands the maximum number of space mappings allowed in data and extended attribute file forks. +| +XFS_SB_FEAT_INCOMPAT_METADIR+ | +Metadata directory tree. See the section about the xref:Metadata_Directories[ +metadata directory tree] for more information. + |===== *sb_features_log_incompat*:: @@ -488,7 +499,9 @@ Sparse inode alignment, in fsblocks. Each chunk of inodes referenced by a sparse inode B+tree record must be aligned to this block granularity. *sb_pquotino*:: -Project quota inode. +Project quota inode. If the +XFS_SB_FEAT_INCOMPAT_METADIR+ feature is enabled, +the project quota file is found through the metadata directory tree and this +field must be zero. *sb_lsn*:: Log sequence number of the last superblock update. diff --git a/design/XFS_Filesystem_Structure/internal_inodes.asciidoc b/design/XFS_Filesystem_Structure/internal_inodes.asciidoc index 84e4cb96..42020a5f 100644 --- a/design/XFS_Filesystem_Structure/internal_inodes.asciidoc +++ b/design/XFS_Filesystem_Structure/internal_inodes.asciidoc @@ -5,6 +5,148 @@ XFS allocates several inodes when a filesystem is created. These are internal and not accessible from the standard directory structure. These inodes are only accessible from the superblock. +[[Metadata_Directories]] +== Metadata Directory Tree + +If the +XFS_SB_FEAT_INCOMPAT_METADIR+ feature is enabled, the +sb_rbmino+ field +in the superblock points to the root of a directory tree containing metadata +files. This directory tree is completely internal to the filesystem and should +not be exposed to user programs. + +Certain types of filesystem metadata can be stored in regular (but hidden) +files. Prior to the metadata directory feature, the superblock contained +pointers to these files. + +When this feature is enabled, metadata files should be found by walking the +metadata directory tree. The superblock fields that formerly pointed to (some) +of those inodes have been deallocated and may be reused by future features. + +.Metadata Directory Paths +[options="header"] +|===== +| Metadata File | Location +| User xref:Quota_Inodes[Quotas] | /quota/user +| Group Quotas | /quota/group +| Project Quotas | /quota/project +| xref:Real-Time_Bitmap_Inode[Realtime Bitmap] | /realtime/bitmap +| xref:Real-Time_Summary_Inode[Realtime Summary] | /realtime/summary +|===== + +Metadata files are flagged by the +XFS_DIFLAG2_METADATA+ flag in the ++di_flags2+ field. Metadata files must have their user, group, and project IDs +set to zero, and must be chmod 0000. + +=== Metadata Directory Example + +This example shows a metadta directory from a freshly formatted root +filesystem: + +---- +xfs_db> sb 0 +xfs_db> p +magicnum = 0x58465342 +blocksize = 4096 +dblocks = 2579968 +rblocks = 0 +rextents = 0 +uuid = 9b535856-7d4c-4c11-a059-42199f602b03 +logstart = 2097159 +rootino = 128 +metadirino = 129 +rextsize = 1 +agblocks = 644992 +agcount = 4 +rbmblocks = 0 +logblocks = 3693 +... +---- + +Notice how the listing no longer includes the realtime bitmap or summary +inodes, but does include the root of the metadata directory tree +(+metadirino+). + +---- +xfs_db> path -m / +xfs_db> ls +129 directory 0x0000002e 1 . +129 directory 0x0000172e 2 .. +130 directory 0xce7fe1eb 8 realtime +133 directory 0x1ebbfa66 5 quota +---- + +Here we use the +path+ and +ls+ commands to display the root directory of +the metadata directory. We can navigate the directory the old way, too: + +---- +xfs_db> p +core.magic = 0x494e +core.mode = 040000 +core.version = 3 +core.format = 1 (local) +core.nlinkv2 = 4 +core.onlink = 0 +core.projid_lo = 0 +core.projid_hi = 0 +core.uid = 0 +core.gid = 0 +... +v3.inumber = 129 +v3.uuid = 9b535856-7d4c-4c11-a059-42199f602b03 +v3.reflink = 0 +v3.cowextsz = 0 +v3.dax = 0 +v3.bigtime = 1 +v3.metadata = 1 +u3.sfdir3.hdr.count = 2 +u3.sfdir3.hdr.i8count = 0 +u3.sfdir3.hdr.parent.i4 = 129 +u3.sfdir3.list[0].namelen = 8 +u3.sfdir3.list[0].offset = 0x60 +u3.sfdir3.list[0].name = "realtime" +u3.sfdir3.list[0].inumber.i4 = 130 +u3.sfdir3.list[0].filetype = 2 +u3.sfdir3.list[1].namelen = 5 +u3.sfdir3.list[1].offset = 0x78 +u3.sfdir3.list[1].name = "quota" +u3.sfdir3.list[1].inumber.i4 = 133 +u3.sfdir3.list[1].filetype = 2 +---- + +The root of the metadata directory is a short format directory, and looks just +like any other directory. The only difference is that the metadata flag is +set, and the directory can only be viewed in the XFS debugger. + +---- +xfs_db> path -m /quota/user +xfs_db> dblock 0 +xfs_db> p +diskdq.magic = 0x4451 +diskdq.version = 0x1 +diskdq.type = 0x1 +diskdq.id = 0 +diskdq.blk_hardlimit = 0 +diskdq.blk_softlimit = 0 +diskdq.ino_hardlimit = 0 +diskdq.ino_softlimit = 0 +diskdq.bcount = 0 +diskdq.icount = 6 +diskdq.itimer = 0 +diskdq.btimer = 0 +diskdq.iwarns = 0 +diskdq.bwarns = 0 +diskdq.rtb_hardlimit = 0 +diskdq.rtb_softlimit = 0 +diskdq.rtbcount = 0 +diskdq.rtbtimer = 0 +diskdq.rtbwarns = 0 +crc = 0x7ada5c8b (correct) +lsn = 0 +uuid = 9b535856-7d4c-4c11-a059-42199f602b03 +---- + +Observe that we can use the xfs_db +path+ command to navigate the metadata +directory tree to the user quota file and display its contents. + [[Quota_Inodes]] == Quota Inodes diff --git a/design/XFS_Filesystem_Structure/ondisk_inode.asciidoc b/design/XFS_Filesystem_Structure/ondisk_inode.asciidoc index 34c06487..964a9611 100644 --- a/design/XFS_Filesystem_Structure/ondisk_inode.asciidoc +++ b/design/XFS_Filesystem_Structure/ondisk_inode.asciidoc @@ -383,6 +383,11 @@ will be copied to all newly created files and directories. Files with this flag set may have up to (2^48^ - 1) extents mapped to the data fork and up to (2^32^ - 1) extents mapped to the attribute fork. This flag requires the +XFS_SB_FEAT_INCOMPAT_NREXT64+ feature to be enabled. +| +XFS_DIFLAG2_METADATA+ | +This file contains filesystem metadata. This feature requires the ++XFS_SB_FEAT_INCOMPAT_METADIR+ feature to be enabled. Metadata files must have +their user, group, and project IDs set to zero, and the permissions bits of the +mode must be zero. Only directories and regular files can have this flag set. |===== *di_cowextsize*::
