Re: [libvirt] [PATCH 6/7] storage:dir: adapts .refreshVol .refreshPool for ploop volumes

On Wed, Apr 06, 2016 at 11:18:22AM +0300, Olga Krishtal wrote: > On 05/04/16 18:01, Ján Tomko wrote: >> On Mon, Mar 14, 2016 at 07:00:39PM +0300, Olga Krishtal wrote: >>> Refreshes meta-information such as allocation, capacity, format, etc. >>> Ploop volumes differ from other volume types. Path to volume is the path >>> to directory with image file root.hds and DiskDescriptor.xml. >>> https://openvz.org/Ploop/format >>> Due to this fact, operations of opening the volume have to be done once >>> again. get the information. >>> >>> To decide whether the given volume is ploops one, it is necessary to check >>> the presence of root.hds and DiskDescriptor.xml files in volumes' directory. >>> Only in this case the volume can be manipulated as the ploops one. >>> Such strategy helps us to resolve problems that might occure, when we >>> upload some other volume type from ploop source. >>> >>> Signed-off-by: Olga Krishtal <okrishtal(a)virtuozzo.com&gt; >>> --- >>> src/storage/storage_backend.c | 62 ++++++++++++++++++++++++++++++++++++-- >>> src/storage/storage_backend.h | 5 ++++ >>> src/storage/storage_backend_fs.c | 64 +++++++++++++++++++++++++++++++++++++--- >>> src/util/virstoragefile.c | 7 +++-- >>> 4 files changed, 129 insertions(+), 9 deletions(-) >>> >>> @@ -69,6 +109,7 @@ virStorageBackendProbeTarget(virStorageSourcePtr target, >>> int fd = -1; >>> int ret = -1; >>> int rc; >>> + int format = VIR_STORAGE_FILE_AUTO; >>> virStorageSourcePtr meta = NULL; >>> struct stat sb; >>> >>> @@ -84,14 +125,26 @@ virStorageBackendProbeTarget(virStorageSourcePtr target, >>> goto cleanup; >>> >>> if (S_ISDIR(sb.st_mode)) { >>> - target->format = VIR_STORAGE_FILE_DIR; >>> - ret = 0; >>> - goto cleanup; >>> + if (virStorageBackendIsPloopDir(target->path)) { >>> + if (virStorageBackendRedoPloopUpdate(target, &sb, &fd, >>> + VIR_STORAGE_VOL_FS_PROBE_FLAGS) >>> + < 0) >>> + goto cleanup; >>> + /* Refresh information stored in DiskDescriptor.xml according >>> + * to ploop image file content.*/ >>> + if (virStorageBackendPloopRestoreDesc(target->path) < 0) >>> + goto cleanup; >> Probing a volume should not change its contents - libvirt should only >> refresh this XML when it changed the volume. >> >> The rest looks good to me. >> >> Jan > The thing is that if we changed the size, the content of root.hds and > had left the old DiskDeskriptor.xml - it becomes impossible to operate. > I mean that DiskDescriptor.xml stores this info - size, Celinders, > Sectors, and what is more important - all information about snapshot. > In the situation when we have uploaded previously snapshoted volume - > the content of volume and DiskDescriptor will be inconsistent. > And work upon such volume will be impossible. > But if you have any idea, where such refresh of DiskDescriptor.xml could > be done - I will be glad to know. DiskDeskriptor should be changed at the same time as root.hds - if libvirt does the resize/content change, it should refresh the XML as part of the API that changes the volume. Libvirt's pool refresh or vol refresh should only update libvirtd's in-memory metadata to match the on-disk state.

If the on-disk state was left inconsistent by some other application, it's a problem of that application. I don't think libvirt should be working around that. Jan