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Diffstat (limited to 'src/ceph/doc/dev/mds_internals')
| -rw-r--r-- | src/ceph/doc/dev/mds_internals/data-structures.rst | 36 | ||||
| -rw-r--r-- | src/ceph/doc/dev/mds_internals/exports.rst | 76 | ||||
| -rw-r--r-- | src/ceph/doc/dev/mds_internals/index.rst | 10 |
3 files changed, 0 insertions, 122 deletions
diff --git a/src/ceph/doc/dev/mds_internals/data-structures.rst b/src/ceph/doc/dev/mds_internals/data-structures.rst deleted file mode 100644 index 1197b62..0000000 --- a/src/ceph/doc/dev/mds_internals/data-structures.rst +++ /dev/null @@ -1,36 +0,0 @@ -MDS internal data structures -============================== - -*CInode* - CInode contains the metadata of a file, there is one CInode for each file. - The CInode stores information like who owns the file, how big the file is. - -*CDentry* - CDentry is the glue that holds inodes and files together by relating inode to - file/directory names. A CDentry links to at most one CInode (it may not link - to any CInode). A CInode may be linked by multiple CDentries. - -*CDir* - CDir only exists for directory inode, it's used to link CDentries under the - directory. A CInode can have multiple CDir when the directory is fragmented. - -These data structures are linked together as:: - - CInode - CDir - | \ - | \ - | \ - CDentry CDentry - CInode CInode - CDir CDir - | | \ - | | \ - | | \ - CDentry CDentry CDentry - CInode CInode CInode - -As this doc is being written, size of CInode is about 1400 bytes, size of CDentry -is about 400 bytes, size of CDir is about 700 bytes. These data structures are -quite large. Please be careful if you want to add new fields to them. - diff --git a/src/ceph/doc/dev/mds_internals/exports.rst b/src/ceph/doc/dev/mds_internals/exports.rst deleted file mode 100644 index c5b0e39..0000000 --- a/src/ceph/doc/dev/mds_internals/exports.rst +++ /dev/null @@ -1,76 +0,0 @@ - -=============== -Subtree exports -=============== - -Normal Migration ----------------- - -The exporter begins by doing some checks in export_dir() to verify -that it is permissible to export the subtree at this time. In -particular, the cluster must not be degraded, the subtree root may not -be freezing or frozen (\ie already exporting, or nested beneath -something that is exporting), and the path must be pinned (\ie not -conflicted with a rename). If these conditions are met, the subtree -freeze is initiated, and the exporter is committed to the subtree -migration, barring an intervening failure of the importer or itself. - -The MExportDirDiscover serves simply to ensure that the base directory -being exported is open on the destination node. It is pinned by the -importer to prevent it from being trimmed. This occurs before the -exporter completes the freeze of the subtree to ensure that the -importer is able to replicate the necessary metadata. When the -exporter receives the MExportDirDiscoverAck, it allows the freeze to proceed. - -The MExportDirPrep message then follows to populate a spanning tree that -includes all dirs, inodes, and dentries necessary to reach any nested -exports within the exported region. This replicates metadata as well, -but it is pushed out by the exporter, avoiding deadlock with the -regular discover and replication process. The importer is responsible -for opening the bounding directories from any third parties before -acknowledging. This ensures that the importer has correct dir_auth -information about where authority is delegated for all points nested -within the subtree being migrated. While processing the MExportDirPrep, -the importer freezes the entire subtree region to prevent any new -replication or cache expiration. - -The warning stage occurs only if the base subtree directory is open by -nodes other than the importer and exporter. If so, then a -MExportDirNotify message informs any bystanders that the authority for -the region is temporarily ambiguous. In particular, bystanders who -are trimming items from their cache must send MCacheExpire messages to -both the old and new authorities. This is necessary to ensure that -the surviving authority reliably receives all expirations even if the -importer or exporter fails. While the subtree is frozen (on both the -importer and exporter), expirations will not be immediately processed; -instead, they will be queued until the region is unfrozen and it can -be determined that the node is or is not authoritative for the region. - -The MExportDir message sends the actual subtree metadata to the importer. -Upon receipt, the importer inserts the data into its cache, logs a -copy in the EImportStart, and replies with an MExportDirAck. The exporter -can now log an EExport, which ultimately specifies that -the export was a success. In the presence of failures, it is the -existence of the EExport that disambiguates authority during recovery. - -Once logged, the exporter will send an MExportDirNotify to any -bystanders, informing them that the authority is no longer ambiguous -and cache expirations should be sent only to the new authority (the -importer). Once these are acknowledged, implicitly flushing the -bystander to exporter message streams of any stray expiration notices, -the exporter unfreezes the subtree, cleans up its state, and sends a -final MExportDirFinish to the importer. Upon receipt, the importer logs -an EImportFinish(true), unfreezes its subtree, and cleans up its -state. - - -PARTIAL FAILURE RECOVERY - - - -RECOVERY FROM JOURNAL - - - - - diff --git a/src/ceph/doc/dev/mds_internals/index.rst b/src/ceph/doc/dev/mds_internals/index.rst deleted file mode 100644 index c8c82ad..0000000 --- a/src/ceph/doc/dev/mds_internals/index.rst +++ /dev/null @@ -1,10 +0,0 @@ -============================== -MDS developer documentation -============================== - -.. rubric:: Contents - -.. toctree:: - :glob: - - * |