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block: Manipulate children list in .attach/.detach 

The children list is specific to BDS parents.  We should not modify it
in the general children modification code, but let BDS parents deal with
it in their .attach() and .detach() methods.

This also has the advantage that a BdrvChild is removed from the
children list before its .bs pointer can become NULL.  BDS parents
generally assume that their children's .bs pointer is never NULL, so
this is actually a bug fix.

Signed-off-by: Hanna Reitz <hreitz@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20211111120829.81329-3-hreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20211115145409.176785-3-kwolf@redhat.com>
Signed-off-by: Hanna Reitz <hreitz@redhat.com>
This commit is contained in:
Hanna Reitz 2021-11-15 15:53:58 +01:00
parent 8d3dd037d9
commit a225369bce
1 changed files with 5 additions and 9 deletions
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14
block.c
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@ -1387,6 +1387,8 @@ static void bdrv_child_cb_attach(BdrvChild *child)
{
BlockDriverState *bs = child->opaque;
QLIST_INSERT_HEAD(&bs->children, child, next);
if (child->role & BDRV_CHILD_COW) {
bdrv_backing_attach(child);
}
@ -1403,6 +1405,8 @@ static void bdrv_child_cb_detach(BdrvChild *child)
}
bdrv_unapply_subtree_drain(child, bs);
QLIST_REMOVE(child, next);
}
static int bdrv_child_cb_update_filename(BdrvChild *c, BlockDriverState *base,
@ -2747,7 +2751,7 @@ static void bdrv_child_free(void *opaque)
static void bdrv_remove_empty_child(BdrvChild *child)
{
assert(!child->bs);
QLIST_SAFE_REMOVE(child, next);
assert(!child->next.le_prev); /* not in children list */
bdrv_child_free(child);
}
@ -2913,12 +2917,6 @@ static int bdrv_attach_child_noperm(BlockDriverState *parent_bs,
return ret;
}
QLIST_INSERT_HEAD(&parent_bs->children, *child, next);
/*
* child is removed in bdrv_attach_child_common_abort(), so don't care to
* abort this change separately.
*/
return 0;
}
@ -4851,7 +4849,6 @@ static void bdrv_remove_filter_or_cow_child_abort(void *opaque)
BdrvRemoveFilterOrCowChild *s = opaque;
BlockDriverState *parent_bs = s->child->opaque;
QLIST_INSERT_HEAD(&parent_bs->children, s->child, next);
if (s->is_backing) {
parent_bs->backing = s->child;
} else {
@ -4906,7 +4903,6 @@ static void bdrv_remove_file_or_backing_child(BlockDriverState *bs,
};
tran_add(tran, &bdrv_remove_filter_or_cow_child_drv, s);
QLIST_SAFE_REMOVE(child, next);
if (s->is_backing) {
bs->backing = NULL;
} else {