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Re: [libvirt] [PATCH] Introduce startupPolicy for chardev to make guest OS bootable when hardware failure happens in log disk



On 05/10/2013 06:10 PM, Seiji Aguchi wrote:
> Any comments?

Apologies that no one has spoken up yet, but this is on my list of
things to review.  I got waylaid by debugging two nasty races today, or
I would have had time to actually give comments; but come Monday, you
should have some better feedback.

> 
>> -----Original Message-----
>> From: Seiji Aguchi
>> Sent: Thursday, May 02, 2013 1:26 PM
>> To: libvir-list redhat com
>> Cc: dle-develop lists sourceforge net; Tomoki Sekiyama (tomoki sekiyama hds com)
>> Subject: [PATCH] Introduce startupPolicy for chardev to make guest OS bootable when hardware failure happens in log disk
>>
>> [Problem]
>> Currently, guest OS's messages can be logged to a local disk of host OS
>> by creating chadevs with options below.
>>   -chardev file,id=charserial0,path=<log file's path> -device isa-serial,chardev=chardevserial0,id=serial0
>>
>> When a hardware failure happens in the disk, qemu-kvm can't create the chardevs.
>> In this case, guest OS doesn't boot up.
>>
>> Actually, there are users who don't desire that guest OS goes down due to a hardware failure
>> of a log disk only.Therefore, qemu should offer some way to boot guest OS up even if the log
>> disk is broken.
>>
>> [Solution]
>> This patch supports startupPolicy for chardev.
>>
>> The starupPolicy is introduced just in case where chardev is "file"
>> because this patch aims for making guest OS boot up when a hardware failure happens.
>>
>> In other cases ,pty, dev, pipe and unix, it is not introduced
>> because they don't access to hardware.
>>
>> The policy works as follows.
>>   - If the value is "optional", guestOS boots up by dropping the chardev.
>>   - If other values are specified, guestOS fails to boot up. (the default)
>>
>> Description about original startupPolicy attribute:
>> http://libvirt.org/git/?p=libvirt.git;a=commitdiff;h=e5a84d74a2789a917bf394f15de9989ec48fded0
>>
>> Signed-off-by: Seiji Aguchi <seiji aguchi hds com>
>> ---
>>  docs/formatdomain.html.in     |    9 ++++++++-
>>  docs/schemas/domaincommon.rng |    3 +++
>>  src/conf/domain_conf.c        |    8 ++++++++
>>  src/conf/domain_conf.h        |    1 +
>>  src/qemu/qemu_process.c       |   25 ++++++++++++++++++++++++-
>>  tests/virt-aa-helper-test     |    3 +++
>>  6 files changed, 47 insertions(+), 2 deletions(-)
>>
>> diff --git a/docs/formatdomain.html.in b/docs/formatdomain.html.in
>> index f325c3c..1e1bf27 100644
>> --- a/docs/formatdomain.html.in
>> +++ b/docs/formatdomain.html.in
>> @@ -4044,13 +4044,20 @@ qemu-kvm -net nic,model=? /dev/null
>>      <p>
>>        A file is opened and all data sent to the character
>>        device is written to the file.
>> +      It is possible to define policy whether guestOS boots up
>> +      if the file is not accessible. This is done by a startupPolicy
>> +      attribute:
>> +      <ul>
>> +      <li>If the vaule is "optional", guestOS boots up by dropping the file.</li>
>> +      <li>If other values are specified, guestOS fails to boot up. (the default)</li>
>> +      </ul>
>>      </p>
>>
>>  <pre>
>>    ...
>>    &lt;devices&gt;
>>      &lt;serial type="file"&gt;
>> -      &lt;source path="/var/log/vm/vm-serial.log"/&gt;
>> +      &lt;source path="/var/log/vm/vm-serial.log" startupPolicy="optional"/&gt;
>>        &lt;target port="1"/&gt;
>>      &lt;/serial&gt;
>>    &lt;/devices&gt;
>> diff --git a/docs/schemas/domaincommon.rng b/docs/schemas/domaincommon.rng
>> index 10596dc..6fc0a3c 100644
>> --- a/docs/schemas/domaincommon.rng
>> +++ b/docs/schemas/domaincommon.rng
>> @@ -2706,6 +2706,9 @@
>>          </optional>
>>          <optional>
>>            <attribute name="path"/>
>> +            <optional>
>> +              <ref name='startupPolicy'/>
>> +            </optional>
>>          </optional>
>>          <optional>
>>            <attribute name="host"/>
>> diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
>> index a8b5dfd..6680f15 100644
>> --- a/src/conf/domain_conf.c
>> +++ b/src/conf/domain_conf.c
>> @@ -6467,6 +6467,7 @@ virDomainChrSourceDefParseXML(virDomainChrSourceDefPtr def,
>>      char *path = NULL;
>>      char *mode = NULL;
>>      char *protocol = NULL;
>> +    char *startupPolicy = NULL;
>>      int remaining = 0;
>>
>>      while (cur != NULL) {
>> @@ -6487,6 +6488,9 @@ virDomainChrSourceDefParseXML(virDomainChrSourceDefPtr def,
>>                           !(flags & VIR_DOMAIN_XML_INACTIVE)))
>>                          path = virXMLPropString(cur, "path");
>>
>> +                    if (startupPolicy == NULL &&
>> +                        def->type == VIR_DOMAIN_CHR_TYPE_FILE)
>> +                        startupPolicy = virXMLPropString(cur, "startupPolicy");
>>                      break;
>>
>>                  case VIR_DOMAIN_CHR_TYPE_UDP:
>> @@ -6559,6 +6563,10 @@ virDomainChrSourceDefParseXML(virDomainChrSourceDefPtr def,
>>
>>          def->data.file.path = path;
>>          path = NULL;
>> +
>> +        def->data.file.startupPolicy =
>> +            virDomainStartupPolicyTypeFromString(startupPolicy);
>> +        startupPolicy = NULL;
>>          break;
>>
>>      case VIR_DOMAIN_CHR_TYPE_STDIO:
>> diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h
>> index 3a0f23a..e709951 100644
>> --- a/src/conf/domain_conf.h
>> +++ b/src/conf/domain_conf.h
>> @@ -1052,6 +1052,7 @@ struct _virDomainChrSourceDef {
>>          /* no <source> for null, vc, stdio */
>>          struct {
>>              char *path;
>> +            int startupPolicy; /* enum virDomainStartupPolicy */
>>          } file; /* pty, file, pipe, or device */
>>          struct {
>>              char *host;
>> diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
>> index e75c8c9..6e2f78e 100644
>> --- a/src/qemu/qemu_process.c
>> +++ b/src/qemu/qemu_process.c
>> @@ -2442,7 +2442,30 @@ qemuProcessPrepareChardevDevice(virDomainDefPtr def ATTRIBUTE_UNUSED,
>>          virReportSystemError(errno,
>>                               _("Unable to pre-create chardev file '%s'"),
>>                               dev->source.data.file.path);
>> -        return -1;
>> +        if (dev->source.data.file.startupPolicy !=
>> +            VIR_DOMAIN_STARTUP_POLICY_OPTIONAL) {
>> +            return -1;
>> +        }
>> +        VIR_FREE(dev->source.data.file.path);
>> +        /*
>> +         *  Change a destination to /dev/null to boot guest OS up
>> +         *  even if a log disk is broken.
>> +         */
>> +        VIR_WARN("Switch the destination to /dev/null");
>> +        dev->source.data.file.path = strdup("/dev/null");
>> +
>> +        if (!(dev->source.data.file.path)) {
>> +            virReportOOMError();
>> +            return -1;
>> +        }
>> +
>> +        if ((fd = open(dev->source.data.file.path,
>> +                       O_CREAT | O_APPEND, S_IRUSR|S_IWUSR)) < 0) {
>> +            virReportSystemError(errno,
>> +                                 _("Unable to pre-create chardev file '%s'"),
>> +                                 dev->source.data.file.path);
>> +            return -1;
>> +        }
>>      }
>>
>>      VIR_FORCE_CLOSE(fd);
>> diff --git a/tests/virt-aa-helper-test b/tests/virt-aa-helper-test
>> index af91c61..7172fd6 100755
>> --- a/tests/virt-aa-helper-test
>> +++ b/tests/virt-aa-helper-test
>> @@ -255,6 +255,9 @@ testme "0" "disk (empty cdrom)" "-r -u $valid_uuid" "$test_xml"
>>  sed -e "s,###UUID###,$uuid,g" -e "s,###DISK###,$disk1,g" -e "s,</devices>,<serial type='file'><source
>> path='$tmpdir/serial.log'/><target port='0'/></serial></devices>,g" "$template_xml" > "$test_xml"
>>  testme "0" "serial" "-r -u $valid_uuid" "$test_xml"
>>
>> +sed -e "s,###UUID###,$uuid,g" -e "s,###DISK###,$disk1,g" -e "s,</devices>,<serial type='file'><source path='$tmpdir/serial.log'
>> startupPolicy='optional'/><target port='0'/></serial></devices>,g" "$template_xml" > "$test_xml"
>> +testme "0" "serial" "-r -u $valid_uuid" "$test_xml"
>> +
>>  sed -e "s,###UUID###,$uuid,g" -e "s,###DISK###,$disk1,g" -e "s,</devices>,<serial type='pty'><target
>> port='0'/></serial></devices>,g" "$template_xml" > "$test_xml"
>>  testme "0" "serial (pty)" "-r -u $valid_uuid" "$test_xml"
>>
>> --
>> 1.7.1
> 
> 
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> 
> 

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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