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

[Olga Krishtal]

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 at virtuozzo.com>
>> ---
>>   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.