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Re: [libvirt] [PATCH 5/5] qemu: hook: Provide hook when restoring a domain save image



On Wed, Sep 17, 2014 at 17:18:39 +0200, Peter Krempa wrote:
> ---
>  docs/hooks.html.in     | 11 ++++++++
>  src/qemu/qemu_driver.c | 69 +++++++++++++++++++++++++++++++++++++++++++++-----
>  src/util/virhook.c     |  3 ++-
>  src/util/virhook.h     |  1 +
>  4 files changed, 76 insertions(+), 8 deletions(-)
> 
> diff --git a/docs/hooks.html.in b/docs/hooks.html.in
> index 07b9d49..265dbb7 100644
> --- a/docs/hooks.html.in
> +++ b/docs/hooks.html.in
> @@ -177,6 +177,17 @@
>          script returns failure or the output XML is not valid, incoming
>          migration will be canceled. This hook may be used, e.g., to change
>          location of disk images for incoming domains.</li>
> +      <li><span class="since">Since 1.2.9</span>, the qemu hook script is
> +        also called when restoring a saved image either via the API or
> +        automatically when restoring a managed save machine. It is called
> +        as: <pre>/etc/libvirt/hooks/qemu guest_name restore begin -</pre>
> +        with domain XML sent to standard input of the script. In this case,
> +        the script acts as a filter and is supposed to modify the domain
> +        XML and print it out on its standard output. Empty output is
> +        identical to copying the input XML without changing it. In case the
> +        script returns failure or the output XML is not valid, restore of the
> +        image will be aborted. This hook may be used, e.g., to change
> +        location of disk images for incoming domains.</li>

Copy&paste? "incoming domains" does not make a lot of sense in case of
restore :-)

>        <li><span class="since">Since 0.9.13</span>, the qemu hook script
>          is also called when the libvirtd daemon restarts and reconnects
>          to previously running QEMU processes. If the script fails, the
> diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
> index 1d82e93..2dd2e48 100644
> --- a/src/qemu/qemu_driver.c
> +++ b/src/qemu/qemu_driver.c
> @@ -5636,20 +5636,23 @@ qemuDomainRestoreFlags(virConnectPtr conn,
>                         unsigned int flags)
>  {
>      virQEMUDriverPtr driver = conn->privateData;
> +    qemuDomainObjPrivatePtr priv = NULL;
>      virDomainDefPtr def = NULL;
> -    virDomainDefPtr newdef = NULL;
>      virDomainObjPtr vm = NULL;
> +    char *xml = NULL;
> +    char *xmlout = NULL;
>      int fd = -1;
>      int ret = -1;
>      virQEMUSaveHeader header;
>      virFileWrapperFdPtr wrapperFd = NULL;
> +    bool hook_taint = false;
> 
>      virCheckFlags(VIR_DOMAIN_SAVE_BYPASS_CACHE |
>                    VIR_DOMAIN_SAVE_RUNNING |
>                    VIR_DOMAIN_SAVE_PAUSED, -1);
> 
> 
> -    fd = qemuDomainSaveImageOpen(driver, path, &def, &header, NULL,
> +    fd = qemuDomainSaveImageOpen(driver, path, &def, &header, &xml,
>                                   (flags & VIR_DOMAIN_SAVE_BYPASS_CACHE) != 0,
>                                   &wrapperFd, false, false);
>      if (fd < 0)
> @@ -5658,12 +5661,29 @@ qemuDomainRestoreFlags(virConnectPtr conn,
>      if (virDomainRestoreFlagsEnsureACL(conn, def) < 0)
>          goto cleanup;
> 
> -    if (dxml) {
> -        if (!(newdef = qemuDomainSaveImageUpdateDef(driver, def, dxml)))
> +    if (virHookPresent(VIR_HOOK_DRIVER_QEMU)) {
> +        int hookret;
> +
> +        if ((hookret = virHookCall(VIR_HOOK_DRIVER_QEMU, def->name,
> +                                   VIR_HOOK_QEMU_OP_RESTORE,
> +                                   VIR_HOOK_SUBOP_BEGIN,
> +                                   NULL,
> +                                   dxml ? dxml : xml,
> +                                   &xmlout)) < 0)
>              goto cleanup;
> 
> -        virDomainDefFree(def);
> -        def = newdef;
> +        if (hookret == 0 && xmlout) {
> +            virDomainDefPtr tmp;
> +
> +            VIR_DEBUG("Using hook-filtered domain XML: %s", xmlout);
> +
> +            if (!(tmp = qemuDomainSaveImageUpdateDef(driver, def, xmlout)))
> +                goto cleanup;
> +
> +            virDomainDefFree(def);
> +            def = tmp;
> +            hook_taint = true;
> +        }

I think you wanted to write this in a bit different way... This way dxml
is ignored when the hook is not present.

>      }
> 
>      if (!(vm = virDomainObjListAdd(driver->domains, def,
...

Jirka


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