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Re: [Qemu-devel] [PATCH v3] block: mirror - fix full sync mode when targ
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH v3] block: mirror - fix full sync mode when target does not support zero init |
Date: |
Thu, 1 Oct 2015 15:35:15 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.2.0 |
On 01/10/2015 15:14, Jeff Cody wrote:
> 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 <address@hidden>
> ---
> 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,
>
Unnecessary last hunk, but the patch is good anyway.
Reviewed-by: Paolo Bonzini <address@hidden>