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Re: [libvirt] [PATCHv5 2/3] libvirt/qemu - support persistent modification of qemu disks



On Wed, 23 Mar 2011 13:15:39 +0800
Wen Congyang <wency cn fujitsu com> wrote:

> At 03/23/2011 12:39 PM, KAMEZAWA Hiroyuki Write:
> > On Mon, 21 Mar 2011 16:05:19 +0800
> > Wen Congyang <wency cn fujitsu com> 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 jp fujitsu com>
> >>> 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 jp fujitsu com>
> >>> ---
> >>>  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 ?


Thanks,
-Kame


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