[Pkg-libvirt-maintainers] Bug#883208: Bug#883208: libvirt0 version 3.0.0-4+deb9u1 fails to migrate qemu guests that use disks with cache='directsync'

[Guido Günther]

Hi,
On Thu, Nov 30, 2017 at 06:16:15PM +0100, Carsten Burkhardt wrote:
> Package: libvirt0
> Version: 3.0.0-4+deb9u1
> 
> libvirt0 version 3.0.0-4+deb9u1 fails to migrate qemu guests that use disks with cache='directsync'
> 
> Directsync is necessary for us to maintain drbd data integrity. However, libvirt in the stable debian release prevents us from using that cache mode for live migration.
> 
> This has been fixed in the git version:
> 
> https://github.com/libvirt/libvirt/commit/fed9cc85eaff6f75e3d232e350d78a53f314815f#diff-6ec6f76d45ea0e7e9e53e36eac65a923
> 
> Here is my attempt at backporting that change:
> 
> 
> --- qemu_migration.c.orig    2017-11-30 15:58:34.143882478 +0100
> +++ qemu_migration.c    2017-11-30 16:26:27.801361294 +0100
> @@ -2377,7 +2377,8 @@
>          /* Our code elsewhere guarantees shared disks are either readonly (in
>           * which case cache mode doesn't matter) or used with cache=none */
>          if (qemuMigrateDisk(disk, nmigrate_disks, migrate_disks) &&
> -            disk->cachemode != VIR_DOMAIN_DISK_CACHE_DISABLE) {
> +            disk->cachemode != VIR_DOMAIN_DISK_CACHE_DISABLE &&
> +            disk->cachemode != VIR_DOMAIN_DISK_CACHE_DIRECTSYNC) {
>              int rc;
> 
>              if (virDomainDiskGetType(disk) == VIR_STORAGE_TYPE_FILE) {
> @@ -2396,7 +2397,7 @@
> 
>              virReportError(VIR_ERR_MIGRATE_UNSAFE, "%s",
>                             _("Migration may lead to data corruption if disks"
> -                             " use cache != none"));
> +                             " use cache != none or cache != directsync"));
>              return false;
>          }
>      }

I've cherry-picked the patch form upstream. Please test the packages at:

     https://people.debian.org/~agx/libvirt/

Cheers,
 -- Guido
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