On 05/26/2015 09:01 AM, Michal Privoznik wrote:
> When playing with disk migration lately, I've noticed this warning in
> domain logs:
>
> WARNING: Image format was not specified for
> 'nbd://masina:49153/drive-virtio-disk0' and probing guessed raw.
> Automatically detecting the format is dangerous for raw images,
> write operations on block 0 will be restricted.
> Specify the 'raw' format explicitly to remove the restrictions.
>
> So I started digging into qemu source code to see what has triggered
> the warning. I'd expect qemu to know formats of guest's disks since we
> tell them on command line. This lead me to qmp_drive_mirror() where
> the following can be found:
>
> if (!has_format) {
> format = mode == NEW_IMAGE_MODE_EXISTING ? NULL :
> bs->drv->format_name;
> }
>
> So, format is automatically initialized from the disk iff mode !=
> "existing". Unfortunately, in migration we are tied to use this mode
> (NBD doesn't support creating new images). Therefore the only way to
> avoid this warning is to pass format. The format that libvirt thinks
> should be in sync with qemu anyway.
>
> Signed-off-by: Michal Privoznik <mpriv...@redhat.com>
> ---
> src/qemu/qemu_migration.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/src/qemu/qemu_migration.c b/src/qemu/qemu_migration.c
> index 32c43f3..279b43f 100644
> --- a/src/qemu/qemu_migration.c
> +++ b/src/qemu/qemu_migration.c
> @@ -1943,6 +1943,7 @@ qemuMigrationDriveMirror(virQEMUDriverPtr driver,
> for (i = 0; i < vm->def->ndisks; i++) {
> virDomainDiskDefPtr disk = vm->def->disks[i];
> qemuDomainDiskPrivatePtr diskPriv = QEMU_DOMAIN_DISK_PRIVATE(disk);
> + const char *format;
format is not initialized here...
> int mon_ret;
>
> /* skip shared, RO and source-less disks */
> @@ -1950,6 +1951,9 @@ qemuMigrationDriveMirror(virQEMUDriverPtr driver,
> !virDomainDiskGetSource(disk))
> continue;
>
> + if (disk->src->format > 0)
> + format = virStorageFileFormatTypeToString(disk->src->format);
then only initialized if src->format > 0
Also this should be VIR_STORAGE_FILE_NONE instead of 0
> +
> VIR_FREE(diskAlias);
> VIR_FREE(nbd_dest);
> if ((virAsprintf(&diskAlias, "%s%s",
> @@ -1967,7 +1971,7 @@ qemuMigrationDriveMirror(virQEMUDriverPtr driver,
> }
>
> mon_ret = qemuMonitorDriveMirror(priv->mon, diskAlias, nbd_dest,
> - NULL, speed, 0, 0, mirror_flags);
> + format, speed, 0, 0, mirror_flags);
Then used here... My compiler balked...
Initializing to NULL worked...
ACK with that change.
John
>
> if (qemuDomainObjExitMonitor(driver, vm) < 0 || mon_ret < 0) {
> qemuBlockJobSyncEnd(driver, vm, disk, NULL);
>
--
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