Add additional check that node parents do not interfere with each
other. This should not hurt existing callers and allows in further
patch use bdrv_refresh_perms() to update a subtree of changed
BdrvChild (check that change is correct).
New check will substitute bdrv_check_update_perm() in following
permissions refactoring, so keep error messages the same to avoid
unit test result changes.
Signed-off-by: Vladimir Sementsov-Ogievskiy
---
block.c | 63 -
1 file changed, 54 insertions(+), 9 deletions(-)
diff --git a/block.c b/block.c
index b951ecb5db..69db01c2ec 100644
--- a/block.c
+++ b/block.c
@@ -1992,6 +1992,57 @@ bool bdrv_is_writable(BlockDriverState *bs)
return bdrv_is_writable_after_reopen(bs, NULL);
}
+static char *bdrv_child_user_desc(BdrvChild *c)
+{
+if (c->klass->get_parent_desc) {
+return c->klass->get_parent_desc(c);
+}
+
+return g_strdup("another user");
+}
+
+static bool bdrv_a_allow_b(BdrvChild *a, BdrvChild *b, Error **errp)
+{
+g_autofree char *user = NULL;
+g_autofree char *perm_names = NULL;
+
+if ((b->perm & a->shared_perm) == b->perm) {
+return true;
+}
+
+perm_names = bdrv_perm_names(b->perm & ~a->shared_perm);
+user = bdrv_child_user_desc(a);
+error_setg(errp, "Conflicts with use by %s as '%s', which does not "
+ "allow '%s' on %s",
+ user, a->name, perm_names, bdrv_get_node_name(b->bs));
+
+return false;
+}
+
+static bool bdrv_parent_perms_conflict(BlockDriverState *bs, Error **errp)
+{
+BdrvChild *a, *b;
+
+/*
+ * During the loop we'll look at each pair twice. That's correct because
+ * bdrv_a_allow_b() is asymmetric and we should check each pair in both
+ * directions.
+ */
+QLIST_FOREACH(a, &bs->parents, next_parent) {
+QLIST_FOREACH(b, &bs->parents, next_parent) {
+if (a == b) {
+continue;
+}
+
+if (!bdrv_a_allow_b(a, b, errp)) {
+return true;
+}
+}
+}
+
+return false;
+}
+
static void bdrv_child_perm(BlockDriverState *bs, BlockDriverState *child_bs,
BdrvChild *c, BdrvChildRole role,
BlockReopenQueue *reopen_queue,
@@ -2169,15 +2220,6 @@ void bdrv_get_cumulative_perm(BlockDriverState *bs,
uint64_t *perm,
*shared_perm = cumulative_shared_perms;
}
-static char *bdrv_child_user_desc(BdrvChild *c)
-{
-if (c->klass->get_parent_desc) {
-return c->klass->get_parent_desc(c);
-}
-
-return g_strdup("another user");
-}
-
char *bdrv_perm_names(uint64_t perm)
{
struct perm_name {
@@ -2321,6 +2363,9 @@ static int bdrv_refresh_perms(BlockDriverState *bs, Error
**errp)
int ret;
uint64_t perm, shared_perm;
+if (bdrv_parent_perms_conflict(bs, errp)) {
+return -EPERM;
+}
bdrv_get_cumulative_perm(bs, &perm, &shared_perm);
ret = bdrv_check_perm(bs, NULL, perm, shared_perm, NULL, errp);
if (ret < 0) {
--
2.29.2
