@@ -241,13 +241,26 @@ static void test_parallel_exclusive_write(void)
bdrv_unref(top);
}
-static void write_to_file_perms(BlockDriverState *bs, BdrvChild *c,
- BdrvChildRole role,
- BlockReopenQueue *reopen_queue,
- uint64_t perm, uint64_t shared,
- uint64_t *nperm, uint64_t *nshared)
+/*
+ * write-to-selected node may have several DATA children, one of them may be
+ * "selected". Exclusive write permission is taken on selected child.
+ *
+ * We don't realize write handler itself, as we need only to test how permission
+ * update works.
+ */
+typedef struct BDRVWriteToSelectedState {
+ BdrvChild *selected;
+} BDRVWriteToSelectedState;
+
+static void write_to_selected_perms(BlockDriverState *bs, BdrvChild *c,
+ BdrvChildRole role,
+ BlockReopenQueue *reopen_queue,
+ uint64_t perm, uint64_t shared,
+ uint64_t *nperm, uint64_t *nshared)
{
- if (bs->file && c == bs->file) {
+ BDRVWriteToSelectedState *s = bs->opaque;
+
+ if (s->selected && c == s->selected) {
*nperm = BLK_PERM_WRITE;
*nshared = BLK_PERM_ALL & ~BLK_PERM_WRITE;
} else {
@@ -256,9 +269,10 @@ static void write_to_file_perms(BlockDriverState *bs, BdrvChild *c,
}
}
-static BlockDriver bdrv_write_to_file = {
- .format_name = "tricky-perm",
- .bdrv_child_perm = write_to_file_perms,
+static BlockDriver bdrv_write_to_selected = {
+ .format_name = "write-to-selected",
+ .instance_size = sizeof(BDRVWriteToSelectedState),
+ .bdrv_child_perm = write_to_selected_perms,
};
@@ -266,15 +280,18 @@ static BlockDriver bdrv_write_to_file = {
* The following test shows that topological-sort order is required for
* permission update, simple DFS is not enough.
*
- * Consider the block driver which has two filter children: one active
- * with exclusive write access and one inactive with no specific
- * permissions.
+ * Consider the block driver (write-to-selected) which has two children: one is
+ * selected so we have exclusive write access to it and for the other one we
+ * don't need any specific permissions.
*
* And, these two children has a common base child, like this:
+ * (additional "top" on top is used in test just because the only public
+ * function to update permission should get a specific child to update.
+ * Making bdrv_refresh_perms() public just for this test isn't worth it)
*
- * ┌─────┐ ┌──────┐
- * │ fl2 │ ◀── │ top │
- * └─────┘ └──────┘
+ * ┌─────┐ ┌───────────────────┐ ┌─────┐
+ * │ fl2 │ ◀── │ write-to-selected │ ◀── │ top │
+ * └─────┘ └───────────────────┘ └─────┘
* │ │
* │ │ w
* │ ▼
@@ -290,14 +307,14 @@ static BlockDriver bdrv_write_to_file = {
*
* So, exclusive write is propagated.
*
- * Assume, we want to make fl2 active instead of fl1.
- * So, we set some option for top driver and do permission update.
+ * Assume, we want to select fl2 instead of fl1.
+ * So, we set some option for write-to-selected driver and do permission update.
*
* With simple DFS, if permission update goes first through
- * top->fl1->base branch it will succeed: it firstly drop exclusive write
- * permissions and than apply them for another BdrvChildren.
- * But if permission update goes first through top->fl2->base branch it
- * will fail, as when we try to update fl2->base child, old not yet
+ * write-to-selected -> fl1 -> base branch it will succeed: it firstly drop
+ * exclusive write permissions and than apply them for another BdrvChildren.
+ * But if permission update goes first through write-to-selected -> fl2 -> base
+ * branch it will fail, as when we try to update fl2->base child, old not yet
* updated fl1->base child will be in conflict.
*
* With topological-sort order we always update parents before children, so fl1
@@ -306,9 +323,10 @@ static BlockDriver bdrv_write_to_file = {
static void test_parallel_perm_update(void)
{
BlockDriverState *top = no_perm_node("top");
- BlockDriverState *tricky =
- bdrv_new_open_driver(&bdrv_write_to_file, "tricky", BDRV_O_RDWR,
+ BlockDriverState *ws =
+ bdrv_new_open_driver(&bdrv_write_to_selected, "ws", BDRV_O_RDWR,
&error_abort);
+ BDRVWriteToSelectedState *s = ws->opaque;
BlockDriverState *base = no_perm_node("base");
BlockDriverState *fl1 = pass_through_node("fl1");
BlockDriverState *fl2 = pass_through_node("fl2");
@@ -320,33 +338,33 @@ static void test_parallel_perm_update(void)
*/
bdrv_ref(base);
- bdrv_attach_child(top, tricky, "file", &child_of_bds, BDRV_CHILD_DATA,
+ bdrv_attach_child(top, ws, "file", &child_of_bds, BDRV_CHILD_DATA,
&error_abort);
- c_fl1 = bdrv_attach_child(tricky, fl1, "first", &child_of_bds,
- BDRV_CHILD_FILTERED, &error_abort);
- c_fl2 = bdrv_attach_child(tricky, fl2, "second", &child_of_bds,
- BDRV_CHILD_FILTERED, &error_abort);
+ c_fl1 = bdrv_attach_child(ws, fl1, "first", &child_of_bds,
+ BDRV_CHILD_DATA, &error_abort);
+ c_fl2 = bdrv_attach_child(ws, fl2, "second", &child_of_bds,
+ BDRV_CHILD_DATA, &error_abort);
bdrv_attach_child(fl1, base, "backing", &child_of_bds, BDRV_CHILD_FILTERED,
&error_abort);
bdrv_attach_child(fl2, base, "backing", &child_of_bds, BDRV_CHILD_FILTERED,
&error_abort);
/* Select fl1 as first child to be active */
- tricky->file = c_fl1;
+ s->selected = c_fl1;
bdrv_child_refresh_perms(top, top->children.lh_first, &error_abort);
assert(c_fl1->perm & BLK_PERM_WRITE);
assert(!(c_fl2->perm & BLK_PERM_WRITE));
/* Now, try to switch active child and update permissions */
- tricky->file = c_fl2;
+ s->selected = c_fl2;
bdrv_child_refresh_perms(top, top->children.lh_first, &error_abort);
assert(c_fl2->perm & BLK_PERM_WRITE);
assert(!(c_fl1->perm & BLK_PERM_WRITE));
/* Switch once more, to not care about real child order in the list */
- tricky->file = c_fl1;
+ s->selected = c_fl1;
bdrv_child_refresh_perms(top, top->children.lh_first, &error_abort);
assert(c_fl1->perm & BLK_PERM_WRITE);