Am 27.11.2020 um 15:45 hat Vladimir Sementsov-Ogievskiy geschrieben:
> Split out no-perm part of bdrv_set_backing_hd() as a separate
> transaction action. Note the in case of existing BdrvChild we reuse it,
> not recreate, just to do less actions.
>
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com>
> /*
> * Sets the bs->backing link of a BDS. A new reference is created; callers
> * which don't need their own reference any more must call bdrv_unref().
> */
> -void bdrv_set_backing_hd(BlockDriverState *bs, BlockDriverState *backing_hd,
> - Error **errp)
> +static int bdrv_set_backing_noperm(BlockDriverState *bs,
> + BlockDriverState *backing_bs,
> + GSList **tran, Error **errp)
> {
> - bool update_inherits_from = bdrv_chain_contains(bs, backing_hd) &&
> - bdrv_inherits_from_recursive(backing_hd, bs);
> + int ret = 0;
> + bool update_inherits_from = bdrv_chain_contains(bs, backing_bs) &&
> + bdrv_inherits_from_recursive(backing_bs, bs);
> + GSList *attach_tran = NULL;
> + BdrvSetBackingNoPermState *s;
>
> if (bdrv_is_backing_chain_frozen(bs, child_bs(bs->backing), errp)) {
> - return;
> + return -EPERM;
> }
>
> - if (backing_hd) {
> - bdrv_ref(backing_hd);
> + if (bs->backing && backing_bs) {
> + bdrv_replace_child_safe(bs->backing, backing_bs, tran);
The old code with separate bdrv_unref_child() and then
bdrv_attach_child() tried to make the AioContests of bs and backing_bs
compatible by moving one of the nodes if necessary.
bdrv_replace_child_safe() doesn't seem to do that, but it only asserts
that both nodes are already in the same context.
I see that iotest 245 doesn't crash, which I think it should if this
were broken, but where does the switch happen now?
Kevin
