During mirror, if the target device does not support zero init, a mirror may result in a corrupted image for sync="full" mode.
This is due to how the initial dirty bitmap is set up prior to copying data - we did not mark sectors as dirty that are unallocated. This means those unallocated sectors are skipped over on the target, and for a device without zero init, invalid data may reside in those holes. If both of the following conditions are true, then we will explicitly mark all sectors as dirty: 1.) sync = "full" 2.) bdrv_has_zero_init(target) == false If the target does support zero init, but a target image is passed in with data already present (i.e. an "existing" image), it is assumed the data present in the existing image is valid data for those sectors. Signed-off-by: Jeff Cody <jc...@redhat.com> --- block/mirror.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/block/mirror.c b/block/mirror.c index a258926..ce367e0 100644 --- a/block/mirror.c +++ b/block/mirror.c @@ -455,6 +455,8 @@ static void coroutine_fn mirror_run(void *opaque) if (!s->is_none_mode) { /* First part, loop on the sectors and initialize the dirty bitmap. */ BlockDriverState *base = s->base; + bool mark_all_dirty = s->base == NULL && !bdrv_has_zero_init(s->target); + for (sector_num = 0; sector_num < end; ) { /* Just to make sure we are not exceeding int limit. */ int nb_sectors = MIN(INT_MAX >> BDRV_SECTOR_BITS, @@ -477,7 +479,7 @@ static void coroutine_fn mirror_run(void *opaque) } assert(n > 0); - if (ret == 1) { + if (ret == 1 || mark_all_dirty) { bdrv_set_dirty_bitmap(s->dirty_bitmap, sector_num, n); } sector_num += n; @@ -767,8 +769,8 @@ void mirror_start(BlockDriverState *bs, BlockDriverState *target, base = mode == MIRROR_SYNC_MODE_TOP ? bs->backing_hd : NULL; mirror_start_job(bs, target, replaces, speed, granularity, buf_size, - on_source_error, on_target_error, unmap, cb, opaque, errp, - &mirror_job_driver, is_none_mode, base); + on_source_error, on_target_error, unmap, + cb, opaque, errp, &mirror_job_driver, is_none_mode, base); } void commit_active_start(BlockDriverState *bs, BlockDriverState *base, -- 1.9.3