At 03/23/2011 01:22 PM, KAMEZAWA Hiroyuki Write:
> On Wed, 23 Mar 2011 13:15:39 +0800
> Wen Congyang <wency@xxxxxxxxxxxxxx> wrote:
>
>> At 03/23/2011 12:39 PM, KAMEZAWA Hiroyuki Write:
>>> On Mon, 21 Mar 2011 16:05:19 +0800
>>> Wen Congyang <wency@xxxxxxxxxxxxxx> wrote:
>>>
>>>> At 03/16/2011 02:45 PM, KAMEZAWA Hiroyuki Write:
>>>>> >From ddcd9cb499dd73dfc91c9f2cc97c064d6dda17fc Mon Sep 17 00:00:00 2001
>>>>> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
>>>>> Date: Wed, 16 Mar 2011 14:05:21 +0900
>>>>> Subject: [PATCHv5 2/3] libvirt/qemu - support persistent modification of qemu disks
>>>>>
>>>>> support changes of disks by VIR_DOMAIN_DEVICE_MODIFY_CONFIG
>>>>> for qemu.
>>>>>
>>>>> Changelog v4->v5:
>>>>> - moved some functions to domain_conf.c
>>>>> - added virDomainDefAddImplicitControllers() for ide/scsi
>>>>> - report OOM.
>>>>> - clean up.
>>>>>
>>>>> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
>>>>> ---
>>>>> src/conf/domain_conf.c | 22 ++++++++++++++++++++++
>>>>> src/conf/domain_conf.h | 3 ++-
>>>>> src/libvirt_private.syms | 2 ++
>>>>> src/qemu/qemu_driver.c | 29 +++++++++++++++++++++++++++++
>>>>> 4 files changed, 55 insertions(+), 1 deletions(-)
>>>>>
>>>>> diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
>>>>> index 16e1291..1d39481 100644
>>>>> --- a/src/conf/domain_conf.c
>>>>> +++ b/src/conf/domain_conf.c
>>>>> @@ -4859,6 +4859,19 @@ virVirtualPortProfileFormat(virBufferPtr buf,
>>>>> virBufferVSprintf(buf, "%s</virtualport>\n", indent);
>>>>> }
>>>>>
>>>>> +int virDomainDiskIndexByName(virDomainDefPtr def, const char *name)
>>>>> +{
>>>>> + virDomainDiskDefPtr vdisk;
>>>>> + int i;
>>>>> +
>>>>> + for (i = 0; i < def->ndisks; i++) {
>>>>> + vdisk = def->disks[i];
>>>>> + if (STREQ(vdisk->dst, name))
>>>>> + return i;
>>>>> + }
>>>>> + return -1;
>>>>> +}
>>>>> +
>>>>> int virDomainDiskInsert(virDomainDefPtr def,
>>>>> virDomainDiskDefPtr disk)
>>>>> {
>>>>> @@ -4930,6 +4943,15 @@ void virDomainDiskRemove(virDomainDefPtr def, size_t i)
>>>>> }
>>>>> }
>>>>>
>>>>> +int virDomainDiskRemoveByName(virDomainDefPtr def, const char *name)
>>>>> +{
>>>>> + int i = virDomainDiskIndexByName(def, name);
>>>>> + if (i < 0)
>>>>> + return -1;
>>>>> + virDomainDiskRemove(def, i);
>>>>> + return 0;
>>>>> +}
>>>>> +
>>>>>
>>>>> int virDomainControllerInsert(virDomainDefPtr def,
>>>>> virDomainControllerDefPtr controller)
>>>>> diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h
>>>>> index 30aeccc..320ca13 100644
>>>>> --- a/src/conf/domain_conf.h
>>>>> +++ b/src/conf/domain_conf.h
>>>>> @@ -1261,7 +1261,7 @@ int virDomainCpuSetParse(const char **str,
>>>>> int maxcpu);
>>>>> char *virDomainCpuSetFormat(char *cpuset,
>>>>> int maxcpu);
>>>>> -
>>>>> +int virDomainDiskIndexByName(virDomainDefPtr def, const char *name);
>>>>> int virDomainDiskInsert(virDomainDefPtr def,
>>>>> virDomainDiskDefPtr disk);
>>>>> void virDomainDiskInsertPreAlloced(virDomainDefPtr def,
>>>>> @@ -1269,6 +1269,7 @@ void virDomainDiskInsertPreAlloced(virDomainDefPtr def,
>>>>> int virDomainDiskDefAssignAddress(virCapsPtr caps, virDomainDiskDefPtr def);
>>>>>
>>>>> void virDomainDiskRemove(virDomainDefPtr def, size_t i);
>>>>> +int virDomainDiskRemoveByName(virDomainDefPtr def, const char *name);
>>>>>
>>>>> int virDomainControllerInsert(virDomainDefPtr def,
>>>>> virDomainControllerDefPtr controller);
>>>>> diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
>>>>> index c88d934..1761dfb 100644
>>>>> --- a/src/libvirt_private.syms
>>>>> +++ b/src/libvirt_private.syms
>>>>> @@ -243,11 +243,13 @@ virDomainDiskDefFree;
>>>>> virDomainDiskDeviceTypeToString;
>>>>> virDomainDiskErrorPolicyTypeFromString;
>>>>> virDomainDiskErrorPolicyTypeToString;
>>>>> +virDomainDiskIndexByName;
>>>>> virDomainDiskInsert;
>>>>> virDomainDiskInsertPreAlloced;
>>>>> virDomainDiskIoTypeFromString;
>>>>> virDomainDiskIoTypeToString;
>>>>> virDomainDiskRemove;
>>>>> +virDomainDiskRemoveByName;
>>>>> virDomainDiskTypeFromString;
>>>>> virDomainDiskTypeToString;
>>>>> virDomainFSDefFree;
>>>>> diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
>>>>> index dbd5bd3..d6d7ad0 100644
>>>>> --- a/src/qemu/qemu_driver.c
>>>>> +++ b/src/qemu/qemu_driver.c
>>>>> @@ -4137,8 +4137,27 @@ cleanup:
>>>>> static int qemuDomainAttachDevicePersistent(virDomainDefPtr vmdef,
>>>>> virDomainDeviceDefPtr newdev)
>>>>> {
>>>>> + virDomainDiskDefPtr disk;
>>>>>
>>>>> switch(newdev->type) {
>>>>> + case VIR_DOMAIN_DEVICE_DISK:
>>>>> + disk = newdev->data.disk;
>>>>> + if (virDomainDiskIndexByName(vmdef, disk->dst) >= 0) {
>>>>> + qemuReportError(VIR_ERR_INVALID_ARG,
>>>>> + _("target %s already exists."), disk->dst);
>>>>> + return -1;
>>>>> + }
>>>>> + if (virDomainDiskInsert(vmdef, disk)) {
>>>>> + virReportOOMError();
>>>>> + return -1;
>>>>> + }
>>>>> + if (disk->bus == VIR_DOMAIN_DISK_BUS_VIRTIO) {
>>>>> + if (qemuDomainAssignPCIAddresses(vmdef) < 0)
>>>>> + return -1;
>>>>> + } else if (virDomainDefAddImplicitControllers(vmdef) < 0)
>>>>> + return -1;
>>>>
>>>> When qemuDomainAssignPCIAddresses() or virDomainDefAddImplicitControllers() failed,
>>>> we should remove disk from vmdef, otherwise, it will cause libvirtd crashed.
>>>>
>>>
>>> By returning -1, the vmdef is not saved and no one will see this modified
>>> vmdef (because the task is inactive here.)
>>>
>>> Do I need to care ?
>>
>> Yes, you need to care it.
>> By returning -1, the vmdef is not saved to disk. But vmdef is hashed, and we may access
>> it again before libvirtd is restarted.
>> When stoping libvirtd, we will free vmdef, this will cause disk is double freed.
>>
>> Here is the steps to reproduce this program:
>> # cat device.xml
>> <disk type='file' device='disk'>
>> <driver name='qemu' type='qcow2'/>
>> <source file='/var/lib/libvirt/images/test3.img'/>
>> <target dev='vdb' bus='virtio'/>
>> <address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/>
>> </disk>
>> # virsh attach-device vm1 device.xml --persistent
>> error: Failed to attach device from device.xml
>> error: An error occurred, but the cause is unknown
>>
>> Now, run attach-device again or stop libvirtd. It will cause libvirtd crashed.
>>
> Hmm, ok. what I should to unahs and free vmdef ?
No, we hash vmdef if it is persistent.
We should do some cleanup when qemuDomainAssignPCIAddresses() or
virDomainDefAddImplicitControllers() failed. For example, calling
virDomainDiskRemove() to remove it.
Another way to solve this problem is: we only malloc the memory and do not insert
the disk to vmdef before calling qemuDomainAssignPCIAddresses() or
virDomainDefAddImplicitControllers(), and insert it when this function successed.
>
>
> Thanks,
> -Kame
>
>
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