It was already true in principle that a throttled BDS always has a BB
attached, except that the order of operations while attaching or
detaching a BDS to/from a BB wasn't careful enough.
This commit breaks graph manipulations while I/O throttling is enabled.
It would have been possible, but quite cumbersome, to keep things
working with some temporary hacks, so it's not worth the hassle. We'll
fix things again in a minute.
Signed-off-by: Kevin Wolf <kw...@redhat.com>
---
block.c | 14 ++++++++++++++
block/block-backend.c | 3 +++
blockdev.c | 4 ++--
tests/test-throttle.c | 11 ++++++++---
4 files changed, 27 insertions(+), 5 deletions(-)
diff --git a/block.c b/block.c
index c22cb3f..4f05586 100644
--- a/block.c
+++ b/block.c
@@ -2255,8 +2255,22 @@ static void swap_feature_fields(BlockDriverState *bs_top,
assert(!bs_new->throttle_state);
if (bs_top->throttle_state) {
assert(bs_top->io_limits_enabled);
+ /*
+ * FIXME Need to break I/O throttling with graph manipulations
+ * temporarily because of conflicting invariants (3. will go away when
+ * throttling is fully converted to work on BlockBackends):
+ *
+ * 1. Every BlockBackend has a single root BDS
+ * 2. I/O throttling functions require an attached BlockBackend
+ * 3. We need to first enable throttling on the new BDS and then
+ * disable it on the old one (because of throttle group refcounts)
+ */
+#if 0
bdrv_io_limits_enable(bs_new, throttle_group_get_name(bs_top));
bdrv_io_limits_disable(bs_top);
+#else
+ abort();
+#endif
}
}
diff --git a/block/block-backend.c b/block/block-backend.c
index a528674..df8f717 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -419,6 +419,9 @@ void blk_remove_bs(BlockBackend *blk)
notifier_list_notify(&blk->remove_bs_notifiers, blk);
blk_update_root_state(blk);
+ if (blk->root->bs->io_limits_enabled) {
+ bdrv_io_limits_disable(blk->root->bs);
+ }
blk->root->bs->blk = NULL;
bdrv_root_unref_child(blk->root);
diff --git a/blockdev.c b/blockdev.c
index 5a53f59..cac9afd 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -2568,8 +2568,6 @@ void qmp_blockdev_change_medium(const char *device, const
char *filename,
goto fail;
}
- blk_apply_root_state(blk, medium_bs);
-
bdrv_add_key(medium_bs, NULL, &err);
if (err) {
error_propagate(errp, err);
@@ -2594,6 +2592,8 @@ void qmp_blockdev_change_medium(const char *device, const
char *filename,
goto fail;
}
+ blk_apply_root_state(blk, medium_bs);
+
qmp_blockdev_close_tray(device, errp);
fail:
diff --git a/tests/test-throttle.c b/tests/test-throttle.c
index 59675fa..d0b3c86 100644
--- a/tests/test-throttle.c
+++ b/tests/test-throttle.c
@@ -573,11 +573,16 @@ static void test_accounting(void)
static void test_groups(void)
{
ThrottleConfig cfg1, cfg2;
+ BlockBackend *blk1, *blk2, *blk3;
BlockDriverState *bdrv1, *bdrv2, *bdrv3;
- bdrv1 = bdrv_new();
- bdrv2 = bdrv_new();
- bdrv3 = bdrv_new();
+ blk1 = blk_new_with_bs(&error_abort);
+ blk2 = blk_new_with_bs(&error_abort);
+ blk3 = blk_new_with_bs(&error_abort);
+
+ bdrv1 = blk_bs(blk1);
+ bdrv2 = blk_bs(blk2);
+ bdrv3 = blk_bs(blk3);
g_assert(bdrv1->throttle_state == NULL);
g_assert(bdrv2->throttle_state == NULL);
--
1.8.3.1
