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Date: Tue, 15 Aug 2017 12:50:05 +0100
From: Stefan Hajnoczi <stefanha@gmail.com>
Message-ID: <20170815115005.GA21670@stefanha-x1.localdomain>
References: <20170815040454.4223-1-famz@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH for-2.10 3/4] block-backend: Defer
 shared_perm tightening migration completion
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To: Fam Zheng <famz@redhat.com>
Cc: qemu-devel@nongnu.org, Kevin Wolf <kwolf@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>, qemu-block@nongnu.org, Max Reitz <mreitz@redhat.com>


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On Tue, Aug 15, 2017 at 12:04:53PM +0800, Fam Zheng wrote:
> @@ -147,6 +166,24 @@ static void blk_root_activate(BdrvChild *child, Erro=
r **errp)
> =20
>      blk->disable_perm =3D false;
> =20
> +    blk_set_perm(blk, blk->perm, BLK_PERM_ALL, &local_err);
> +    if (local_err) {
> +        error_propagate(errp, local_err);
> +        blk->disable_perm =3D true;
> +        return;
> +    }
> +
> +    if (runstate_check(RUN_STATE_INMIGRATE)) {
> +        /* Activation can happen when migration process is still active,=
 for
> +         * example when nbd_server_add is called during non-shared stora=
ge
> +         * migration. Defer the shared_perm update to migration completi=
on. */
> +        if (!blk->vmsh) {
> +            blk->vmsh =3D qemu_add_vm_change_state_handler(blk_vm_state_=
changed,
> +                                                         blk);

Please add a qemu_del_vm_change_state_handler() call to cover the case
where the BB is deleted before the migration state changes.

This is necessary to prevent a memory leak and a crash when the change
state handler is invoked.

Stefan

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