[libvirt] [PATCH] qemuDomainRemoveMemoryDevice: unlink() memory backing file

[Michal Privoznik]

On 01/11/2018 01:36 PM, Peter Krempa wrote:
> On Thu, Jan 11, 2018 at 13:24:57 +0100, Michal Privoznik wrote:
>> https://bugzilla.redhat.com/show_bug.cgi?id=1461214
>>
>> Since fec8f9c49af we try to use predictable file names for
>> 'memory-backend-file' objects. But that made us provide full path
>> to qemu when hot plugging the object while previously we provided
>> merely a directory. But this makes qemu behave differently. If
>> qemu sees a path terminated with a directory it calls mkstemp()
>> and unlinks the file immediately. But if it sees full path it
>> just calls open(path, O_CREAT ..); and never unlinks the file.
>> Therefore it's up to libvirt to unlink the file and not leave it
>> behind.
>>
>> Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
>> ---
>>
>> Zack, can you please check if this patch is suitable for your use cases?
>>
>>  src/qemu/qemu_hotplug.c |  3 +++
>>  src/qemu/qemu_process.c | 26 ++++++++++++++++++++++++++
>>  src/qemu/qemu_process.h |  4 ++++
>>  3 files changed, 33 insertions(+)
>>
>> diff --git a/src/qemu/qemu_hotplug.c b/src/qemu/qemu_hotplug.c
>> index 6dc16a105..f26e2ca60 100644
>> --- a/src/qemu/qemu_hotplug.c
>> +++ b/src/qemu/qemu_hotplug.c
>> @@ -3894,6 +3894,9 @@ qemuDomainRemoveMemoryDevice(virQEMUDriverPtr driver,
>>      if (qemuDomainNamespaceTeardownMemory(vm, mem) <  0)
>>          VIR_WARN("Unable to remove memory device from /dev");
>>  
>> +    if (qemuProcessDestroyMemoryBackingPath(driver, vm, mem) < 0)
>> +        VIR_WARN("Unable to destroy memory backing path");
>> +
>>      virDomainMemoryDefFree(mem);
> 
> This will not call the function when we shut down qemu. Is the full
> directory removed in that case?
> 

Yes, from qemuProcessStop() we call qemuProcessBuildDestroyMemoryPaths()
which in turn calls virFileDeleteTree() over all domain specific
hugepages paths and memoryBacking ones.

Michal