Since Ceph version Infernalis (9.2.0) the new fast-diff mechanism of RBD allows for querying actual volume usage. Prior to this version there was no easy and fast way to query how much allocation a RBD volume had inside a Ceph cluster. To use the fast-diff feature it needs to be enabled per RBD image and is only supported by Ceph cluster running version Infernalis (9.2.0) or newer. Without the fast-diff feature enabled libvirt will report an allocation identical to the image capacity. This is how libvirt behaves currently. 'virsh vol-info rbd/image2' might output for example: Name: image2 Type: network Capacity: 1,00 GiB Allocation: 124,00 MiB Newly created volumes will have the fast-diff feature enabled if the backing Ceph cluster supports it. Signed-off-by: Wido den Hollander <wido(a)widodh.nl&gt; --- src/storage/storage_backend_rbd.c | 48 +++++++++++++++++++++++++++++++++++---- 1 file changed, 44 insertions(+), 4 deletions(-) diff --git a/src/storage/storage_backend_rbd.c b/src/storage/storage_backend_rbd.c index 5d73370..cdcfa48 100644 --- a/src/storage/storage_backend_rbd.c +++ b/src/storage/storage_backend_rbd.c @@ -279,6 +279,20 @@ virStorageBackendRBDCloseRADOSConn(virStorageBackendRBDStatePtr ptr) return ret; } +#if LIBRBD_VERSION_CODE > 265 +static int +virStorageBackendRBDRefreshVolInfoCb(uint64_t offset ATTRIBUTE_UNUSED, + size_t len, + int exists, + void *arg) { + uint64_t *used_size = (uint64_t *)(arg); + if (exists) + (*used_size) += len; + + return 0; +} +#endif + static int volStorageBackendRBDRefreshVolInfo(virStorageVolDefPtr vol, virStoragePoolObjPtr pool, @@ -288,6 +302,8 @@ volStorageBackendRBDRefreshVolInfo(virStorageVolDefPtr vol, int r = 0; rbd_image_t image = NULL; rbd_image_info_t info; + uint64_t features ATTRIBUTE_UNUSED; + uint64_t used_size ATTRIBUTE_UNUSED = 0; if ((r = rbd_open_read_only(ptr->ioctx, vol->name, &image, NULL)) < 0) { ret = -r; @@ -303,15 +319,39 @@ volStorageBackendRBDRefreshVolInfo(virStorageVolDefPtr vol, goto cleanup; } - VIR_DEBUG("Refreshed RBD image %s/%s (size: %zu obj_size: %zu num_objs: %zu)", - pool->def->source.name, vol->name, info.size, info.obj_size, - info.num_objs); - vol->target.capacity = info.size; vol->target.allocation = info.obj_size * info.num_objs; vol->type = VIR_STORAGE_VOL_NETWORK; vol->target.format = VIR_STORAGE_FILE_RAW; +#if LIBRBD_VERSION_CODE > 265 + if ((r = rbd_get_features(image, &features)) < 0) { + virReportSystemError(-r, _("failed to get flags of RBD image '%s'"), + vol->name); + goto cleanup; + } + + if (features & RBD_FEATURE_FAST_DIFF) { + VIR_DEBUG("RBD image %s/%s has fast-diff enabled. Querying allocation", + pool->def->source.name, vol->name); + + if ((r = rbd_diff_iterate2(image, NULL, 0, info.size, 0, 1, + &virStorageBackendRBDRefreshVolInfoCb, + &used_size)) < 0) { + virReportSystemError(-r, _("failed to iterate RBD image '%s'"), + vol->name); + goto cleanup; + } + + vol->target.allocation = used_size; + } +#endif + + VIR_DEBUG("Refreshed RBD image %s/%s (capacity: %llu allocation: %llu " + "obj_size: %zu num_objs: %zu)", + pool->def->source.name, vol->name, vol->target.capacity, + vol->target.allocation, info.obj_size, info.num_objs); + VIR_FREE(vol->target.path); if (virAsprintf(&vol->target.path, "%s/%s", pool->def->source.name, -- 1.9.1