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Re: [PATCH] Add directsync cache mode support for disk driver

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On Fri, Sep 02, 2011 at 03:38:38PM +0800, Osier Yang wrote:
> Newer QEMU introduced cache=directsync for -drive, this patchset
> is to expose it in libvirt layer.
> 
>   * Introduced a new QEMU capability flag ($prefix_CACHE_DIRECTSYNC),
>     As even $prefix_CACHE_V2 is set, we can't known if directsync
>     is supported.
> ---
>  docs/formatdomain.html.in    |    2 +-
>  docs/schemas/domain.rng      |    1 +
>  src/conf/domain_conf.c       |    3 ++-
>  src/conf/domain_conf.h       |    1 +
>  src/qemu/qemu_capabilities.c |    6 +++++-
>  src/qemu/qemu_capabilities.h |    1 +
>  src/qemu/qemu_command.c      |   29 ++++++++++++++++++++++-------
>  tests/qemuargv2xmltest.c     |    1 +
>  tests/qemuxml2argvtest.c     |    3 +++
>  tools/virsh.pod              |    3 ++-
>  10 files changed, 39 insertions(+), 11 deletions(-)
> 
> diff --git a/docs/formatdomain.html.in b/docs/formatdomain.html.in
> index f46771d..6cb36d3 100644
> --- a/docs/formatdomain.html.in
> +++ b/docs/formatdomain.html.in
> @@ -976,7 +976,7 @@
>            <li>
>              The optional <code>cache</code> attribute controls the
>              cache mechanism, possible values are "default", "none",
> -            "writethrough" and "writeback".
> +            "writethrough", "writeback", and "directsync".
>              <span class="since">Since 0.6.0</span>
>            </li>
>            <li>
> diff --git a/docs/schemas/domain.rng b/docs/schemas/domain.rng
> index dd8c41a..e43b17d 100644
> --- a/docs/schemas/domain.rng
> +++ b/docs/schemas/domain.rng
> @@ -829,6 +829,7 @@
>          <value>none</value>
>          <value>writeback</value>
>          <value>writethrough</value>
> +        <value>directsync</value>
>        </choice>
>      </attribute>
>    </define>
> diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
> index 00212db..a2de8df 100644
> --- a/src/conf/domain_conf.c
> +++ b/src/conf/domain_conf.c
> @@ -160,7 +160,8 @@ VIR_ENUM_IMPL(virDomainDiskCache, VIR_DOMAIN_DISK_CACHE_LAST,
>                "default",
>                "none",
>                "writethrough",
> -              "writeback")
> +              "writeback",
> +              "directsync")
>  
>  VIR_ENUM_IMPL(virDomainDiskErrorPolicy, VIR_DOMAIN_DISK_ERROR_POLICY_LAST,
>                "default",
> diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h
> index 8382d28..0abb75e 100644
> --- a/src/conf/domain_conf.h
> +++ b/src/conf/domain_conf.h
> @@ -165,6 +165,7 @@ enum  virDomainDiskCache {
>      VIR_DOMAIN_DISK_CACHE_DISABLE,
>      VIR_DOMAIN_DISK_CACHE_WRITETHRU,
>      VIR_DOMAIN_DISK_CACHE_WRITEBACK,
> +    VIR_DOMAIN_DISK_CACHE_DIRECTSYNC,
>  
>      VIR_DOMAIN_DISK_CACHE_LAST
>  };
> diff --git a/src/qemu/qemu_capabilities.c b/src/qemu/qemu_capabilities.c
> index f665de4..631d683 100644
> --- a/src/qemu/qemu_capabilities.c
> +++ b/src/qemu/qemu_capabilities.c
> @@ -125,6 +125,7 @@ VIR_ENUM_IMPL(qemuCaps, QEMU_CAPS_LAST,
>                "sga",
>                "virtio-blk-pci.event_idx",
>                "virtio-net-pci.event_idx",
> +              "cache-directsync",
>      );
>  
>  struct qemu_feature_flags {
> @@ -902,8 +903,11 @@ qemuCapsComputeCmdFlags(const char *help,
>      if (strstr(help, "-drive")) {
>          qemuCapsSet(flags, QEMU_CAPS_DRIVE);
>          if (strstr(help, "cache=") &&
> -            !strstr(help, "cache=on|off"))
> +            !strstr(help, "cache=on|off")) {
>              qemuCapsSet(flags, QEMU_CAPS_DRIVE_CACHE_V2);
> +            if (strstr(help, "directsync"))
> +                qemuCapsSet(flags, QEMU_CAPS_DRIVE_CACHE_DIRECTSYNC);
> +        }
>          if (strstr(help, "format="))
>              qemuCapsSet(flags, QEMU_CAPS_DRIVE_FORMAT);
>          if (strstr(help, "readonly="))
> diff --git a/src/qemu/qemu_capabilities.h b/src/qemu/qemu_capabilities.h
> index 13af0b9..c01d438 100644
> --- a/src/qemu/qemu_capabilities.h
> +++ b/src/qemu/qemu_capabilities.h
> @@ -100,6 +100,7 @@ enum qemuCapsFlags {
>      QEMU_CAPS_SGA               = 62, /* Serial Graphics Adapter */
>      QEMU_CAPS_VIRTIO_BLK_EVENT_IDX = 63, /* virtio-blk-pci.event_idx */
>      QEMU_CAPS_VIRTIO_NET_EVENT_IDX = 64, /* virtio-net-pci.event_idx */
> +    QEMU_CAPS_DRIVE_CACHE_DIRECTSYNC = 65, /* Is cache=directsync supported? */
>  
>      QEMU_CAPS_LAST,                   /* this must always be the last item */
>  };
> diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
> index 44a553b..fa52dc0 100644
> --- a/src/qemu/qemu_command.c
> +++ b/src/qemu/qemu_command.c
> @@ -64,14 +64,16 @@ VIR_ENUM_DECL(qemuDiskCacheV2)
>  VIR_ENUM_IMPL(qemuDiskCacheV1, VIR_DOMAIN_DISK_CACHE_LAST,
>                "default",
>                "off",
> -              "off", /* writethrough not supported, so for safety, disable */
> -              "on"); /* Old 'on' was equivalent to 'writeback' */
> +              "off",  /* writethrough not supported, so for safety, disable */
> +              "on",   /* Old 'on' was equivalent to 'writeback' */
> +              "off"); /* directsync not supported, for safety, disable */
>  
>  VIR_ENUM_IMPL(qemuDiskCacheV2, VIR_DOMAIN_DISK_CACHE_LAST,
>                "default",
>                "none",
>                "writethrough",
> -              "writeback");
> +              "writeback",
> +              "directsync");
>  
>  VIR_ENUM_DECL(qemuVideo)
>  
> @@ -1516,10 +1518,21 @@ qemuBuildDriveStr(virDomainDiskDefPtr disk,
>      }
>  
>      if (disk->cachemode) {
> -        const char *mode =
> -            qemuCapsGet(qemuCaps, QEMU_CAPS_DRIVE_CACHE_V2) ?
> -            qemuDiskCacheV2TypeToString(disk->cachemode) :
> -            qemuDiskCacheV1TypeToString(disk->cachemode);
> +        const char *mode = NULL;
> +
> +        if (qemuCapsGet(qemuCaps, QEMU_CAPS_DRIVE_CACHE_V2)) {
> +            mode = qemuDiskCacheV2TypeToString(disk->cachemode);
> +
> +            if (disk->cachemode == VIR_DOMAIN_DISK_CACHE_DIRECTSYNC &&
> +                !qemuCapsGet(qemuCaps, QEMU_CAPS_DRIVE_CACHE_DIRECTSYNC)) {
> +                qemuReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
> +                                _("disk cache mode 'directsync' is not "
> +                                  "supported by this QEMU"));
> +                goto error;
> +            }
> +        } else {
> +            mode = qemuDiskCacheV1TypeToString(disk->cachemode);
> +        }
>  
>          virBufferAsprintf(&opt, ",cache=%s", mode);
>      } else if (disk->shared && !disk->readonly) {
> @@ -5211,6 +5224,8 @@ qemuParseCommandLineDisk(virCapsPtr caps,
>                  def->cachemode = VIR_DOMAIN_DISK_CACHE_WRITEBACK;
>              else if (STREQ(values[i], "writethrough"))
>                  def->cachemode = VIR_DOMAIN_DISK_CACHE_WRITETHRU;
> +            else if (STREQ(values[i], "directsync"))
> +                def->cachemode = VIR_DOMAIN_DISK_CACHE_DIRECTSYNC;
>          } else if (STREQ(keywords[i], "werror") ||
>                     STREQ(keywords[i], "rerror")) {
>              if (STREQ(values[i], "stop"))
> diff --git a/tests/qemuargv2xmltest.c b/tests/qemuargv2xmltest.c
> index c2b6cf2..91f15af 100644
> --- a/tests/qemuargv2xmltest.c
> +++ b/tests/qemuargv2xmltest.c
> @@ -168,6 +168,7 @@ mymain(void)
>      DO_TEST("disk-drive-cache-v2-wt");
>      DO_TEST("disk-drive-cache-v2-wb");
>      DO_TEST("disk-drive-cache-v2-none");
> +    DO_TEST("disk-drive-cache-directsync");
>      DO_TEST("disk-drive-network-nbd");
>      DO_TEST("disk-drive-network-rbd");
>      DO_TEST("disk-drive-network-sheepdog");
> diff --git a/tests/qemuxml2argvtest.c b/tests/qemuxml2argvtest.c
> index 6e8da5e..b009bf3 100644
> --- a/tests/qemuxml2argvtest.c
> +++ b/tests/qemuxml2argvtest.c
> @@ -338,6 +338,9 @@ mymain(void)
>              QEMU_CAPS_DRIVE, QEMU_CAPS_DRIVE_CACHE_V2, QEMU_CAPS_DRIVE_FORMAT);
>      DO_TEST("disk-drive-cache-v2-none", false,
>              QEMU_CAPS_DRIVE, QEMU_CAPS_DRIVE_CACHE_V2, QEMU_CAPS_DRIVE_FORMAT);
> +    DO_TEST("disk-drive-cache-directsync", false,
> +            QEMU_CAPS_DRIVE, QEMU_CAPS_DRIVE_CACHE_V2,
> +            QEMU_CAPS_DRIVE_CACHE_DIRECTSYNC, QEMU_CAPS_DRIVE_FORMAT);
>      DO_TEST("disk-drive-network-nbd", false,
>              QEMU_CAPS_DRIVE, QEMU_CAPS_DRIVE_FORMAT);
>      DO_TEST("disk-drive-network-rbd", false,
> diff --git a/tools/virsh.pod b/tools/virsh.pod
> index b90c26e..5ac2c5c 100644
> --- a/tools/virsh.pod
> +++ b/tools/virsh.pod
> @@ -1099,7 +1099,8 @@ floppy device; consider using B<update-device> for this usage instead.
>  I<mode> can specify the two specific mode I<readonly> or I<shareable>.
>  I<persistent> indicates the changes will affect the next boot of the domain.
>  I<sourcetype> can indicate the type of source (block|file)
> -I<cache> can be one of "default", "none", "writethrough" or "writeback".
> +I<cache> can be one of "default", "none", "writethrough", "writeback", or
> +"directsync".
>  I<serial> is the serial of disk device. I<shareable> indicates the disk device
>  is shareable between domains.
>  I<address> is the address of disk device in the form of pci:domain.bus.slot.function,

  ACK, though I would prefer if docs/formatdomain.html.in was expanded
  to explain the semantic of that new flag !

Daniel

-- 
Daniel Veillard      | libxml Gnome XML XSLT toolkit  http://xmlsoft.org/
daniel@xxxxxxxxxxxx  | Rpmfind RPM search engine http://rpmfind.net/
http://veillard.com/ | virtualization library  http://libvirt.org/

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