12.07.2021 14:54, Lukas Straub wrote:
> Remove the workaround introduced in commit
> 6ecbc6c52672db5c13805735ca02784879ce8285
> "replication: Avoid blk_make_empty() on read-only child".
>
> It is not needed anymore since s->hidden_disk is guaranteed to be
> writable when secondary_do_checkpoint() runs. Because replication_start(),
> _do_checkpoint() and _stop() are only called by COLO migration code
> and COLO-migration activates all disks via bdrv_invalidate_cache_all()
> before it calls these functions.
In replication_child_perm()
we have
if ((bs->open_flags & (BDRV_O_INACTIVE | BDRV_O_RDWR)) == BDRV_O_RDWR) {
*nperm |= BLK_PERM_WRITE;
}
That's probably possible
1. configure a block graph like described in replicatio doc, but all disks opened read-only. so we don't have WRITE permission
2. start replication
3. crash on trying to make disk empty in do_checkpoint with no WRITE permission
Still, I think if it possible, we'll crash on first bdrv_make_empty of active disk, and that's preexisting.
So:
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
>
> Signed-off-by: Lukas Straub <lukasstraub2@web.de>
> ---
> block/replication.c | 12 +-----------
> 1 file changed, 1 insertion(+), 11 deletions(-)
>
> diff --git a/block/replication.c b/block/replication.c
> index 772bb63374..1e9dc4d309 100644
> --- a/block/replication.c
> +++ b/block/replication.c
> @@ -356,17 +356,7 @@ static void secondary_do_checkpoint(BlockDriverState *bs, Error **errp)
> return;
> }
>
> - BlockBackend *blk = blk_new(qemu_get_current_aio_context(),
> - BLK_PERM_WRITE, BLK_PERM_ALL);
> - blk_insert_bs(blk, s->hidden_disk->bs, &local_err);
> - if (local_err) {
> - error_propagate(errp, local_err);
> - blk_unref(blk);
> - return;
> - }
> -
> - ret = blk_make_empty(blk, errp);
> - blk_unref(blk);
> + ret = bdrv_make_empty(s->hidden_disk, errp);
> if (ret < 0) {
> return;
> }
> --
> 2.20.1
>
--
Best regards,
Vladimir