[libvirt] [PATCH] storage: only run safezero if allocation is > 0

[John Ferlan]

On 08/24/2015 05:44 AM, Martin Kletzander wrote:
> On Sun, Aug 23, 2015 at 10:14:29PM +0200, Guido Günther wrote:
>> While a zero allocation in safezero should be fine it isn't when we use
>> posix_fallocate which returns EINVAL on a zero allocation.
>>
>> While we could skip the zero allocation in safezero_posix_fallocate it's
>> an optimization to do it for all allocations.
>>
>> This fixes vm installation via virtinst for me which otherwise aborts
>> like:
>>
>>   Starting install...
>>   Retrieving file linux...               | 5.9 MB     00:01 ...
>>   Retrieving file initrd.gz...           |  29 MB     00:07 ...
>>   ERROR    Couldn't create storage volume 'virtinst-linux.sBgds4':
>> 'cannot fill file '/var/lib/libvirt/boot/virtinst-linux.sBgds4':
>> Invalid argument'
>> ---
>> No idea while this didn't show up earlier though.
>>
> 
> ACK, that was probably caused due to previous unclean installation.
> 

I tripped across this recently too, but had nothing to do with
installations - rather the bug I'm looking at is dealing with creating a
volume in an NFS pool. I think the "root cause" is commit id 'e30297b09'.

In my bz, the input vol.xml has:

    <capacity>4048576000</capacity>
    <allocation>0</allocation>

which in the code prior to commit e30297b09 would have left remain = 0
and regardless if need_alloc was true and avoided the safezero.

I have to assume your situation was similar.

John


>> src/storage/storage_backend.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/src/storage/storage_backend.c
>> b/src/storage/storage_backend.c
>> index db49739..0418473 100644
>> --- a/src/storage/storage_backend.c
>> +++ b/src/storage/storage_backend.c
>> @@ -455,7 +455,7 @@ createRawFile(int fd, virStorageVolDefPtr vol,
>>         pos = inputvol->target.capacity - remain;
>>     }
>>
>> -    if (need_alloc) {
>> +    if (need_alloc && (vol->target.allocation - pos > 0)) {
>>         if (safezero(fd, pos, vol->target.allocation - pos) < 0) {
>>             ret = -errno;
>>             virReportSystemError(errno, _("cannot fill file '%s'"),
>> -- 
>> 2.1.4
>>
>> -- 
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> 
> 
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