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Re: [libvirt] [PATCH v3 RESEND 06/12] qemu_migration: Introduce qemuMigrationStartNBDServer()



On Mon, Feb 18, 2013 at 15:38:39 +0100, Michal Privoznik wrote:
> We need to start NBD server and feed it with all non-<shared/>,
> RW and source-full disks. Moreover, with new virPortAllocator we
> must ensure the borrowed port for NBD server will be returned if
> either migration completes or qemu process is teared down.
> ---
>  src/qemu/qemu_migration.c | 84 ++++++++++++++++++++++++++++++++++++++++++++++-
>  src/qemu/qemu_process.c   |  5 +++
>  2 files changed, 88 insertions(+), 1 deletion(-)
> 
> diff --git a/src/qemu/qemu_migration.c b/src/qemu/qemu_migration.c
> index 82c3f97..876e81b 100644
> --- a/src/qemu/qemu_migration.c
> +++ b/src/qemu/qemu_migration.c
...
> @@ -1097,6 +1098,80 @@ error:
>      return NULL;
>  }
>  
> +/**
> + * qemuMigrationStartNBDServer:
> + * @driver: qemu driver
> + * @vm: domain
> + *
> + * Starts NBD server. This is a newer method to copy
> + * storage during migration than using 'blk' and 'inc'
> + * arguments in 'migrate' monitor command.
> + * Error is reported here.
> + *
> + * Returns 0 on success, -1 otherwise.
> + */
> +static int
> +qemuMigrationStartNBDServer(virQEMUDriverPtr driver,
> +                            virDomainObjPtr vm)
> +{
> +    int ret = -1;
> +    qemuDomainObjPrivatePtr priv = vm->privateData;
> +    unsigned short port = 0;
> +    const char *listen = "0.0.0.0";

This doesn't compile:

    error: declaration of 'listen' shadows a global declaration

> +    char *diskAlias = NULL;
> +    size_t i;
> +
> +    for (i = 0; i < vm->def->ndisks; i++) {
> +        virDomainDiskDefPtr disk = vm->def->disks[i];
> +
> +        /* skip shared, RO and source-less disks */
> +        if (disk->shared || disk->readonly || !disk->src)
> +            continue;
> +
> +        VIR_FREE(diskAlias);
> +        if (virAsprintf(&diskAlias, "%s%s",
> +                        QEMU_DRIVE_HOST_PREFIX, disk->info.alias) < 0) {
> +            virReportOOMError();
> +            goto cleanup;
> +        }
> +
> +        if (qemuDomainObjEnterMonitorAsync(driver, vm,
> +                                           QEMU_ASYNC_JOB_MIGRATION_IN) < 0)
> +            goto cleanup;
> +
> +        if (!port) {
> +            if (virPortAllocatorAcquire(driver->remotePorts, &port) < 0)

qemuDomainObjExitMonitor() is missing here.

> +                goto cleanup;
> +
> +            if (qemuMonitorNBDServerStart(priv->mon, listen, port) < 0) {
> +                qemuDomainObjExitMonitor(driver, vm);
> +                virReportError(VIR_ERR_OPERATION_FAILED, "%s",
> +                               _("Unable to start nbd server"));

Do not overwrite useful errors from lower layers.

> +                goto cleanup;
> +            }
> +        }
> +
> +        if (qemuMonitorNBDServerAdd(priv->mon, diskAlias, true) < 0) {
> +            qemuDomainObjExitMonitor(driver, vm);
> +
> +            virReportError(VIR_ERR_OPERATION_FAILED,
> +                           _("Unable to add '%s' to NDB server"), diskAlias);

Do not overwrite useful errors from lower layers.

> +                goto cleanup;
> +            goto cleanup;
> +        }
> +        qemuDomainObjExitMonitor(driver, vm);
> +    }
> +
> +    priv->nbdPort = port;
> +    ret = 0;
> +
> +cleanup:
> +    VIR_FREE(diskAlias);
> +    if (ret < 0)
> +        virPortAllocatorRelease(driver->remotePorts, port);
> +    return ret;
> +}
> +
> +
>  /* Validate whether the domain is safe to migrate.  If vm is NULL,
>   * then this is being run in the v2 Prepare stage on the destination
>   * (where we only have the target xml); if vm is provided, then this
> @@ -1822,8 +1897,11 @@ done:
>          if (flags & VIR_MIGRATE_TUNNELLED)
>              VIR_DEBUG("NBD in tunnelled migration is currently not supported");
>          else {
> +            if (qemuMigrationStartNBDServer(driver, vm) < 0) {
> +                /* error already reported */
> +                goto endjob;
> +            }
>              cookieFlags |= QEMU_MIGRATION_COOKIE_NBD;
> -            priv->nbdPort = 0;
>          }
>      }
>  

As already mentioned in 2/12, we must not do this when source did not
ask for NBD.

...

Jirka


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