[libvirt] [PATCH v4 2/4] storage: report error rather than warning if backing files doesn't exist

[Guannan Ren]

On 07/15/2013 11:31 PM, Ján Tomko wrote:
> On 07/02/2013 11:35 AM, Guannan Ren wrote:
>> If one of backing files for disk source doesn't exist, the guest will not
>> be able to find and use the disk even though the disk still exists in
>> guest xml definition. So reporting an error make more sense.
>>
>> Adding virFileAccessibleAs() to check if the backing file described in
>> disk meta exist in real path. If not, report error. the uid and gid
>> arguments don't have so much meannings for F_OK, so give 0 for them.
>> ---
>>   src/util/virstoragefile.c | 23 +++++++++++++++--------
>>   tests/virstoragetest.c    | 16 ++++++++--------
>>   2 files changed, 23 insertions(+), 16 deletions(-)
>>
>> diff --git a/src/util/virstoragefile.c b/src/util/virstoragefile.c
>> index 27aa4fe..cb61e5b 100644
>> --- a/src/util/virstoragefile.c
>> +++ b/src/util/virstoragefile.c
>> @@ -870,14 +877,10 @@ virStorageFileGetMetadataInternal(const char *path,
>>                                          !!directory, backing,
>>                                          &meta->directory,
>>                                          &meta->backingStore) < 0) {
>> -                    /* the backing file is (currently) unavailable, treat this
>> -                     * file as standalone:
>> -                     * backingStoreRaw is kept to mark broken image chains */
>> -                    meta->backingStoreIsFile = false;
>> -                    backingFormat = VIR_STORAGE_FILE_NONE;
>> -                    VIR_WARN("Backing file '%s' of image '%s' is missing.",
>> -                             meta->backingStoreRaw, path);
>> -
>> +                    VIR_ERROR(_("Backing file '%s' of image '%s' is missing."),
>> +                              meta->backingStoreRaw, path);
>> +                    VIR_FREE(backing);
>> +                    goto cleanup;
>>                   }
>>               }
>>               VIR_FREE(backing);
> This change means you won't be able to start the pool if one of the files is
> missing a backing file. I've forwarded a patch [1] from/for [2] that ignores
> missing files on pool start and there is a bug [3] requesting that we ignore
> other files as well. I feel like this is going in the other direction.
>
> Wouldn't it be enough to check for them on domain start-up and leave the pool
> running even if one of those volumes doesn't have an existing backing file?
>
> Jan
>
> [1] https://www.redhat.com/archives/libvir-list/2013-July/msg00635.html
> [2] https://bugzilla.redhat.com/show_bug.cgi?id=977706
> [3] https://bugzilla.redhat.com/show_bug.cgi?id=710866

As what you pointed out is close to my issue, I chose to propose a patch 
on bug 977706 first
https://www.redhat.com/archives/libvir-list/2013-July/msg01026.html.

Guannan