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block: Handle permission errors in change_parent_backing_link()

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Instead of just trying to change parents by parent over to reference @to
instead of @from, and abort()ing whenever the permissions don't allow
this, do proper permission checking beforehand and pass any error to the
callers.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
This commit is contained in:
Kevin Wolf 2017-03-02 18:43:00 +01:00
parent 46181129ea
commit 234ac1a902
1 changed files with 44 additions and 6 deletions
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50
block.c
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@ -2933,21 +2933,53 @@ static bool should_update_child(BdrvChild *c, BlockDriverState *to)
}
static void change_parent_backing_link(BlockDriverState *from,
BlockDriverState *to)
BlockDriverState *to, Error **errp)
{
BdrvChild *c, *next;
GSList *list = NULL, *p;
uint64_t old_perm, old_shared;
uint64_t perm = 0, shared = BLK_PERM_ALL;
int ret;
/* Make sure that @from doesn't go away until we have successfully attached
* all of its parents to @to. */
bdrv_ref(from);
/* Put all parents into @list and calculate their cumulative permissions */
QLIST_FOREACH_SAFE(c, &from->parents, next_parent, next) {
if (!should_update_child(c, to)) {
continue;
}
list = g_slist_prepend(list, c);
perm |= c->perm;
shared &= c->shared_perm;
}
/* Check whether the required permissions can be granted on @to, ignoring
* all BdrvChild in @list so that they can't block themselves. */
ret = bdrv_check_update_perm(to, perm, shared, list, errp);
if (ret < 0) {
bdrv_abort_perm_update(to);
goto out;
}
/* Now actually perform the change. We performed the permission check for
* all elements of @list at once, so set the permissions all at once at the
* very end. */
for (p = list; p != NULL; p = p->next) {
c = p->data;
bdrv_ref(to);
/* FIXME Are we sure that bdrv_replace_child() can't run into
* &error_abort because of permissions? */
bdrv_replace_child(c, to, true);
bdrv_replace_child_noperm(c, to);
bdrv_unref(from);
}
bdrv_get_cumulative_perm(to, &old_perm, &old_shared);
bdrv_set_perm(to, old_perm | perm, old_shared | shared);
out:
g_slist_free(list);
bdrv_unref(from);
}
/*
@ -2980,7 +3012,12 @@ void bdrv_append(BlockDriverState *bs_new, BlockDriverState *bs_top,
goto out;
}
change_parent_backing_link(bs_top, bs_new);
change_parent_backing_link(bs_top, bs_new, &local_err);
if (local_err) {
error_propagate(errp, local_err);
bdrv_set_backing_hd(bs_new, NULL, &error_abort);
goto out;
}
/* bs_new is now referenced by its new parents, we don't need the
* additional reference any more. */
@ -2995,7 +3032,8 @@ void bdrv_replace_in_backing_chain(BlockDriverState *old, BlockDriverState *new)
bdrv_ref(old);
change_parent_backing_link(old, new);
/* FIXME Proper error handling */
change_parent_backing_link(old, new, &error_abort);
bdrv_unref(old);
}