Re: [libvirt] [PATCH 2/2] storage: btrfs subvolumes for directory pools

This commit adds support for btrfs subvolumes as directory volumes. The directory storage pool can be used to manage btrfs subvolumes on an existing btrfs filesystem. The driver can create new blank subvolumes and snapshots of existing subvolumes as well as delete existing subvolumes. The subvolumes created are automatically made visible on the host side and can be attached to domains using the <filesystem> tags as defined in 'format domain' documentation. Subvolumes do not implement quotas at the moment because the current (btrfs-progs-0.20.rc1.20130501git7854c8b-4.fc20.x86_64) support for quota management in btrfs-progs is lacking the necessary features, for example it's not possible to see the quota assigned to a certain subvolume and usage information is only updated on syncfs(2). Quota support will be implemented once the tools gain the necessary features. Signed-off-by: Oskari Saarenmaa <os(a)ohmu.fi&gt; --- configure.ac | 25 ++- docs/schemas/storagevol.rng | 1 + docs/storage.html.in | 30 ++- libvirt.spec.in | 4 + src/conf/storage_conf.c | 3 + src/conf/storage_conf.h | 1 + src/storage/storage_backend.c | 15 +- src/storage/storage_backend_fs.c | 222 ++++++++++++++++++++-- src/util/virstoragefile.c | 4 +- src/util/virstoragefile.h | 1 + tests/storagevolxml2xmlin/vol-btrfs-snapshot.xml | 13 ++ tests/storagevolxml2xmlin/vol-btrfs.xml | 9 + tests/storagevolxml2xmlout/vol-btrfs-snapshot.xml | 26 +++ tests/storagevolxml2xmlout/vol-btrfs.xml | 17 ++ tests/storagevolxml2xmltest.c | 2 + 15 files changed, 343 insertions(+), 30 deletions(-) create mode 100644 tests/storagevolxml2xmlin/vol-btrfs-snapshot.xml create mode 100644 tests/storagevolxml2xmlin/vol-btrfs.xml create mode 100644 tests/storagevolxml2xmlout/vol-btrfs-snapshot.xml create mode 100644 tests/storagevolxml2xmlout/vol-btrfs.xml

@@ -866,6 +901,23 @@ virStorageBackendFileSystemRefresh(virConnectPtr conn ATTRIBUTE_UNUSED, goto cleanup; } +#if WITH_STORAGE_BTRFS + /* check for subvolumes */ + if (vol->target.format == VIR_STORAGE_FILE_DIR && + fstype != NULL && STREQ(fstype, "btrfs")) {

+ int vars[] = {2}; + const char *regexes[] = {"^\\s*([A-Za-z ]+):\\s*(.+)\\s*$"}; + virCommandPtr cmd = virCommandNewArgList( + "btrfs", "subvolume", "show", vol->target.path, NULL); + if (cmd == NULL) + goto cleanup; + virStorageBackendRunProgRegex(NULL, cmd, 1, regexes, vars, + btrfsVolInfo, vol, NULL); + if (vol->backingStore.format == VIR_STORAGE_FILE_VOLUME) + missing_subvolume_info ++; + } +#endif +

+static int createVolumeDir(virConnectPtr conn ATTRIBUTE_UNUSED, + virStoragePoolObjPtr pool ATTRIBUTE_UNUSED, + virStorageVolDefPtr vol, + virStorageVolDefPtr inputvol, + unsigned int flags) +{ + int ret = -1; + char *vol_dir_name = NULL; + char *fstype = NULL; + virCommandPtr cmd = NULL; + struct stat st; + + virCheckFlags(0, -1); + + if (inputvol) { + virReportError(VIR_ERR_INTERNAL_ERROR, "%s", + _("cannot copy from volume to a subvolume")); + return -1; + } + + if ((vol_dir_name = mdir_name(vol->target.path)) == NULL) + goto cleanup; + + fstype = virFileFsType(vol_dir_name); + if (fstype == NULL) { + virReportSystemError(errno, + _("cannot get filesystem type for %s"), + vol->target.path); + goto cleanup; + } +#if WITH_STORAGE_BTRFS + else if (STREQ(fstype, "btrfs")) { + cmd = virCommandNew("btrfs"); + if (!cmd) + goto cleanup; + + if (vol->backingStore.path == NULL) { + virCommandAddArgList(cmd, "subvolume", "create", vol->target.path, NULL); + } else { + int accessRetCode = -1; + + accessRetCode = access(vol->backingStore.path, R_OK | X_OK);

+ if (accessRetCode != 0) { + virReportSystemError(errno, + _("inaccessible backing store volume %s"), + vol->backingStore.path); + goto cleanup; + } + + virCommandAddArgList(cmd, "subvolume", "snapshot", vol->backingStore.path, + vol->target.path, NULL); + } + if (virCommandRun(cmd, NULL) < 0) + goto cleanup; + } +#endif + else { + virReportError(VIR_ERR_CONFIG_UNSUPPORTED, + _("subvolumes are not supported in %s"), + fstype); + goto cleanup; + } + + if (stat(vol->target.path, &st) < 0) { + virReportSystemError(errno, + _("failed to create %s"), vol->target.path); + goto cleanup; + } + ret = 0; + +cleanup: + VIR_FREE(vol_dir_name); + VIR_FREE(fstype); + virCommandFree(cmd); + return ret; +} +