On 12/05/2015 13:48, Fam Zheng wrote:
> Unsetting dirty globally with discard is not very correct. The discard may
> zero
> out sectors (depending on can_write_zeroes_with_unmap), we should replicate
> this change to destinition side to make sure that the guest sees the same
> data.
>
> Calling bdrv_reset_dirty also troubles mirror job because the hbitmap iterator
> doesn't expect unsetting of bits after current position.
>
> So let's do it the opposite way which fixes both problems: set the dirty bits
> if we are to discard it.
>
> Reported-by: wangxiaol...@ucloud.cn
> Signed-off-by: Fam Zheng <f...@redhat.com>
Reviewed-by: Paolo Bonzini <pbonz...@redhat.com>
> ---
> block/io.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/block/io.c b/block/io.c
> index 1ce62c4..809688b 100644
> --- a/block/io.c
> +++ b/block/io.c
> @@ -2343,8 +2343,6 @@ int coroutine_fn bdrv_co_discard(BlockDriverState *bs,
> int64_t sector_num,
> return -EROFS;
> }
>
> - bdrv_reset_dirty(bs, sector_num, nb_sectors);
> -
> /* Do nothing if disabled. */
> if (!(bs->open_flags & BDRV_O_UNMAP)) {
> return 0;
> @@ -2354,6 +2352,8 @@ int coroutine_fn bdrv_co_discard(BlockDriverState *bs,
> int64_t sector_num,
> return 0;
> }
>
> + bdrv_set_dirty(bs, sector_num, nb_sectors);
> +
> max_discard = MIN_NON_ZERO(bs->bl.max_discard, BDRV_REQUEST_MAX_SECTORS);
> while (nb_sectors > 0) {
> int ret;
>
