On 02/06/2013 08:52 AM, Michal Privoznik wrote:
> This function does the source part of NBD magic. It
> invokes drive-mirror on each non shared and RW disk with
> a source and wait till the mirroring process completes.
> When it does we can proceed with migration.
>
> Currently, an active waiting is done: every 500ms libvirt
> asks qemu if block-job is finished or not. However, once
> the job finishes, qemu doesn't report its progress so we
> can only assume if the job finished successfully or not.
> The better solution would be to listen to the event which
> is sent as soon as the job finishes. The event does
> contain the result of job.
> ---
> src/qemu/qemu_migration.c | 190 +++++++++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 189 insertions(+), 1 deletion(-)
>
> diff --git a/src/qemu/qemu_migration.c b/src/qemu/qemu_migration.c
> index 16840b2..defad6b 100644
> --- a/src/qemu/qemu_migration.c
> +++ b/src/qemu/qemu_migration.c
> @@ -1165,6 +1165,188 @@ cleanup:
> return ret;
> }
>
> +/**
> + * qemuMigrationDiskMirror:
> + * @driver: qemu driver
> + * @vm: domain
> + * @mig: migration cookie
> + * @host: where are we migrating to
> + * @speed: how much should the copying be limited
> + * @migrate_flags: migrate monitor command flags
> + *
> + * Run drive-mirror to feed NBD server running on dst and
> + * wait till the process completes. On success, update
> + * @migrate_flags so we don't tell 'migrate' command to
> + * do the very same operation.
> + *
> + * Returns 0 on success (@migrate_flags updated),
> + * -1 otherwise.
> + */
> +static int
> +qemuMigrationDriveMirror(virQEMUDriverPtr driver,
> + virDomainObjPtr vm,
> + qemuMigrationCookiePtr mig,
> + const char *host,
> + unsigned long speed,
> + unsigned int *migrate_flags)
> +{
> + qemuDomainObjPrivatePtr priv = vm->privateData;
> + int ret = -1;
> + int mon_ret;
> + int port;
> + ssize_t i;
Isn't this really just a loop counter?
> + char *diskAlias = NULL;
> + char *nbd_dest = NULL;
> + unsigned int mirror_flags = VIR_DOMAIN_BLOCK_REBASE_REUSE_EXT;
> + virErrorPtr err = NULL;
> +
> + if (!(*migrate_flags & (QEMU_MONITOR_MIGRATE_NON_SHARED_DISK |
> + QEMU_MONITOR_MIGRATE_NON_SHARED_INC)))
> + return 0;
> +
> + if (!mig->nbd) {
> + /* Destination doesn't support NBD server.
> + * Fall back to previous implementation.
> + * XXX Or should we report an error here? */
> + VIR_DEBUG("Destination doesn't support NBD server "
> + "Falling back to previous implementation.");
> + ret = 0;
> + goto cleanup;
> + }
> +
> + /* steal NBD port and thus prevent it's propagation back to destination */
> + port = mig->nbd->port;
> + mig->nbd->port = 0;
> +
> + if (*migrate_flags & QEMU_MONITOR_MIGRATE_NON_SHARED_INC)
> + mirror_flags |= VIR_DOMAIN_BLOCK_REBASE_SHALLOW;
> +
> + for (i = 0; i < vm->def->ndisks; i++) {
> + virDomainDiskDefPtr disk = vm->def->disks[i];
> + virDomainBlockJobInfo info;
> +
> + /* skip shared, RO and source-less disks */
> + if (disk->shared || disk->readonly || !disk->src)
> + continue;
> +
> + VIR_FREE(diskAlias);
> + VIR_FREE(nbd_dest);
> + if ((virAsprintf(&diskAlias, "%s%s",
> + QEMU_DRIVE_HOST_PREFIX, disk->info.alias) < 0) ||
> + (virAsprintf(&nbd_dest, "nbd:%s:%u:exportname=%s",
> + host, port, diskAlias) < 0)) {
> + virReportOOMError();
> + goto error;
> + }
> +
> + if (qemuDomainObjEnterMonitorAsync(driver, vm,
> + QEMU_ASYNC_JOB_MIGRATION_OUT) < 0)
> + goto error;
> + mon_ret = qemuMonitorDriveMirror(priv->mon, diskAlias, nbd_dest,
> + NULL, speed, mirror_flags);
> + qemuDomainObjExitMonitorWithDriver(driver, vm);
> +
> + if (mon_ret < 0)
> + goto error;
> +
> + /* wait for completion */
> + while (true) {
> + /* Poll every 500ms for progress & to allow cancellation */
> + struct timespec ts = { .tv_sec = 0, .tv_nsec = 500 * 1000 * 1000ull };
> +
> + memset(&info, 0, sizeof(info));
> +
> + if (qemuDomainObjEnterMonitorAsync(driver, vm,
> + QEMU_ASYNC_JOB_MIGRATION_OUT) < 0)
> + goto error;
> + if (priv->job.asyncAbort) {
> + /* explicitly do this *after* we entered the monitor,
> + * as this is a critical section so we are guaranteed
> + * priv->job.asyncAbort will not change */
> + qemuDomainObjExitMonitorWithDriver(driver, vm);
> + virReportError(VIR_ERR_OPERATION_ABORTED, _("%s: %s"),
> + qemuDomainAsyncJobTypeToString(priv->job.asyncJob),
> + _("canceled by client"));
> + goto error;
> + }
> + mon_ret = qemuMonitorBlockJob(priv->mon, diskAlias, NULL, 0,
> + &info, BLOCK_JOB_INFO, true);
> + qemuDomainObjExitMonitorWithDriver(driver, vm);
> +
> + if (mon_ret < 0) {
> + /* If there's not any job running on a block device,
> + * qemu won't report anything, so it is not fatal
> + * if we fail to query status as job may have finished
> + * while we were sleeping. */
> + virReportError(VIR_ERR_OPERATION_FAILED,
> + _("Unable to query drive-mirror job status. "
> + "Stop polling on '%s' cur:%llu end:%llu"),
> + diskAlias, info.cur, info.end);
> + goto error;
> + }
> +
> + if (info.cur == info.end) {
> + VIR_DEBUG("Drive mirroring of '%s' completed", diskAlias);
> + break;
> + }
> +
> + /* XXX Frankly speaking, we should listen to the events,
> + * instead of doing this. But this works for now and we
> + * are doing something similar in migration itself anyway */
> +
> + virObjectUnlock(vm);
> + qemuDriverUnlock(driver);
> +
> + nanosleep(&ts, NULL);
> +
> + qemuDriverLock(driver);
> + virObjectLock(vm);
> + }
> + }
> +
> + /* Okay, copied. Modify migrate_flags */
> + *migrate_flags &= ~(QEMU_MONITOR_MIGRATE_NON_SHARED_DISK |
> + QEMU_MONITOR_MIGRATE_NON_SHARED_INC);
> + ret = 0;
> +
> +cleanup:
> + VIR_FREE(diskAlias);
> + VIR_FREE(nbd_dest);
> + return ret;
> +
> +error:
> + /* don't overwrite any errors */
> + err = virSaveLastError();
> + /* cancel any outstanding jobs */
> + for (; i >= 0; i--) {
You could enter this loop without actually having started a job for the
current "i" value. Also, it seems to me from reading the code that the
processing is start a job, wait for completion... start a job, wait for
completion. Thus is going backwards here necessary? IOW - wouldn't you
only need to cancel the "current" job? There's a number of reasons to
get to error a couple which could be because of some other failure, such
as priv->job.asyncAbort and "(mon_ret < 0)" when there's job a job running.
> + virDomainDiskDefPtr disk = vm->def->disks[i];
> +
> + /* skip shared, RO 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 error;
This could be one nasty loop
> + }
> + if (qemuDomainObjEnterMonitorAsync(driver, vm,
> + QEMU_ASYNC_JOB_MIGRATION_OUT) == 0) {
> + if (qemuMonitorBlockJob(priv->mon, diskAlias, NULL, 0,
> + NULL, BLOCK_JOB_ABORT, true) < 0) {
> + VIR_WARN("Unable to cancel block-job on '%s'", diskAlias);
> + }
> + qemuDomainObjExitMonitorWithDriver(driver, vm);
> + } else {
> + VIR_WARN("Unable to enter monitor. No block job cancelled");
> + }
> + }
> + if (err)
> + virSetError(err);
> + virFreeError(err);
> + goto cleanup;
> +}
>
> /* 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
> @@ -2429,6 +2611,13 @@ qemuMigrationRun(virQEMUDriverPtr driver,
> if (qemuDomainMigrateGraphicsRelocate(driver, vm, mig) < 0)
> VIR_WARN("unable to provide data for graphics client relocation");
>
> + /* this will update migrate_flags on success */
> + if (qemuMigrationDriveMirror(driver, vm, mig, spec->dest.host.name,
> + migrate_speed, &migrate_flags) < 0) {
> + /* error reported by helper func */
> + goto cleanup;
> + }
> +
> /* Before EnterMonitor, since qemuMigrationSetOffline already does that */
> if (!(flags & VIR_MIGRATE_LIVE) &&
> virDomainObjGetState(vm, NULL) == VIR_DOMAIN_RUNNING) {
> @@ -2456,7 +2645,6 @@ qemuMigrationRun(virQEMUDriverPtr driver,
> goto cleanup;
> }
>
> -
> /* connect to the destination qemu if needed */
> if (spec->destType == MIGRATION_DEST_CONNECT_HOST &&
> qemuMigrationConnect(driver, vm, spec) < 0) {
>
--
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