Re: [libvirt] PATCH: Support storage copy on write volumes

This is a follow up on Miloslav's proposal to add copy on write support to the storage APIs, changing the XML to that described here: http://www.redhat.com/archives/libvir-list/2009-January/msg00231.html In addition to the original QCOW/VMDK support, I have done an impl which can extract the backing store for LVM volumes

diff --git a/src/storage_backend.c b/src/storage_backend.c

@@ -235,38 +263,38 @@ virStorageBackendUpdateVolInfoFD(virConn continue; if (memcmp(buffer+disk_types[i].offset, &disk_types[i].magic, disk_types[i].length) == 0) { - vol->target.format = disk_types[i].part_table_type; + target->format = disk_types[i].part_table_type; break; } } } - vol->target.perms.mode = sb.st_mode; - vol->target.perms.uid = sb.st_uid; - vol->target.perms.gid = sb.st_gid; + target->perms.mode = sb.st_mode & (0x200-1);

+ target->perms.uid = sb.st_uid; + target->perms.gid = sb.st_gid;

diff --git a/src/storage_backend_fs.c b/src/storage_backend_fs.c

+static int +cowGetBackingStore(virConnectPtr conn, + char **res, + const unsigned char *buf, + size_t buf_size) +{ + size_t len; + + *res = NULL; + if (buf_size < 4+4+1024) + return BACKING_STORE_INVALID; + if (buf[4+4] == '\0') /* cow_header_v2.backing_file[0] */ + return BACKING_STORE_OK; + + len = 1024; + if (VIR_ALLOC_N(*res, len + 1) < 0) { + virStorageReportError(conn, VIR_ERR_NO_MEMORY, _("backing store path")); + return BACKING_STORE_ERROR; + } + memcpy(*res, buf + 4+4, len); /* cow_header_v2.backing_file */ + (*res)[len] = '\0'; + if (VIR_REALLOC_N(*res, strlen(*res) + 1) < 0) {

+ /* Ignore failure */ + } + return BACKING_STORE_OK; +}

@@ -846,17 +1081,36 @@ virStorageBackendFileSystemVolCreate(vir vol->target.format); return -1; } + if (vol->backingStore.path) { + if ((backingType = virStorageVolFormatFileSystemTypeToString(vol->backingStore.format)) == NULL) { + virStorageReportError(conn, VIR_ERR_INTERNAL_ERROR, + _("unknown storage vol backing store type %d"), + vol->backingStore.format); + return -1; + } + if (access(vol->backingStore.path, R_OK) != 0) { + virReportSystemError(conn, errno, + _("inaccessible backing store volume %s"), + vol->backingStore.path); + return -1; + } + } /* Size in KB */ snprintf(size, sizeof(size), "%llu", vol->capacity/1024); - imgargv[0] = QEMU_IMG; - imgargv[1] = "create"; - imgargv[2] = "-f"; - imgargv[3] = type; - imgargv[4] = vol->target.path; - imgargv[5] = size; - imgargv[6] = NULL; + i = 0; + imgargv[i++] = QEMU_IMG; + imgargv[i++] = "create"; + imgargv[i++] = "-f"; + imgargv[i++] = type; + if (vol->backingStore.path != NULL) { + imgargv[i++] = "-b"; + imgargv[i++] = vol->backingStore.path; + } + imgargv[i++] = vol->target.path; + imgargv[i++] = size; + imgargv[i++] = NULL;

diff --git a/src/storage_backend_iscsi.c b/src/storage_backend_iscsi.c --- a/src/storage_backend_iscsi.c +++ b/src/storage_backend_iscsi.c @@ -226,7 +226,11 @@ virStorageBackendISCSINewLun(virConnectP VIR_FREE(devpath); - if (virStorageBackendUpdateVolInfoFD(conn, vol, fd, 1) < 0) + if (virStorageBackendUpdateVolTargetInfoFD(conn, + &vol->target, + fd, + &vol->allocation, + &vol->capacity) < 0) goto cleanup; /* XXX use unique iSCSI id instead */ diff --git a/src/storage_backend_logical.c b/src/storage_backend_logical.c --- a/src/storage_backend_logical.c +++ b/src/storage_backend_logical.c @@ -116,8 +116,22 @@ virStorageBackendLogicalMakeVol(virConne strcat(vol->target.path, vol->name); } + if (groups[1] && !STREQ(groups[1], "")) { + if (VIR_ALLOC_N(vol->backingStore.path, strlen(pool->def->target.path) + + 1 + strlen(groups[1]) + 1) < 0) { + virStorageReportError(conn, VIR_ERR_NO_MEMORY, "%s", _("volume")); + return -1; + } + strcpy(vol->backingStore.path, pool->def->target.path); + strcat(vol->backingStore.path, "/"); + strcat(vol->backingStore.path, groups[1]);