05.02.2021 19:26, Kevin Wolf wrote:
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?
Hmm. Seems on path "if (bs->backing && backing_bs) {" we really miss aio
context handling. Probably 245 doesn't check this branch? Or if leaves different aio contexts in one
subtree..
--
Best regards,
Vladimir
