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Re: [Qemu-devel] [PATCH 3/3] block: remove legacy I/O throttling
From: |
Kevin Wolf |
Subject: |
Re: [Qemu-devel] [PATCH 3/3] block: remove legacy I/O throttling |
Date: |
Wed, 2 Aug 2017 12:33:19 +0200 |
User-agent: |
Mutt/1.8.3 (2017-05-23) |
Am 02.08.2017 um 12:07 hat Stefan Hajnoczi geschrieben:
> On Tue, Aug 01, 2017 at 04:49:07PM +0300, Manos Pitsidianakis wrote:
> > diff --git a/block.c b/block.c
> > index 9ebdba28b0..c6aad25286 100644
> > --- a/block.c
> > +++ b/block.c
> > @@ -1975,6 +1975,7 @@ BdrvChild *bdrv_root_attach_child(BlockDriverState
> > *child_bs,
> > child = g_new(BdrvChild, 1);
> > *child = (BdrvChild) {
> > .bs = NULL,
> > + .parent_bs = NULL,
> > .name = g_strdup(child_name),
> > .role = child_role,
> > .perm = perm,
> > @@ -2009,6 +2010,7 @@ BdrvChild *bdrv_attach_child(BlockDriverState
> > *parent_bs,
> > if (child == NULL) {
> > return NULL;
> > }
> > + child->parent_bs = parent_bs;
> >
> > QLIST_INSERT_HEAD(&parent_bs->children, child, next);
> > return child;
> > @@ -3729,6 +3731,12 @@ const char *bdrv_get_parent_name(const
> > BlockDriverState *bs)
> > return name;
> > }
> > }
> > + if (c->parent_bs && c->parent_bs->implicit) {
> > + name = bdrv_get_parent_name(c->parent_bs);
> > + if (name && *name) {
> > + return name;
> > + }
> > + }
> > }
> >
> > return NULL;
>
> This should be a separate patch.
>
> Who updates parent_bs if the parent is changed (e.g.
> bdrv_replace_node())?
>
> We already have bs->parents. Why is BdrvChild->parent_bs needed?
I haven't look at the whole patch yet, but BdrvChild->parent_bs is a
thing that intentionally doesn't exist. A node simply has no business
knowing its parents - which may or may not be BlockDriverStates (the
obvious example where they aren't BDSes are BlockBackends, but block
jobs own some BdrvChild objects, too).
Usually the replacement is a BdrvChildRole callback.
Kevin
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