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[PATCH v5 08/45] block/snapshot: stress that we fallback to primary chil
From: |
Vladimir Sementsov-Ogievskiy |
Subject: |
[PATCH v5 08/45] block/snapshot: stress that we fallback to primary child |
Date: |
Thu, 31 Mar 2022 00:28:25 +0300 |
Actually what we chose is a primary child. Let's stress it in the code.
We are going to drop indirect pointer logic here in future. Actually
this commit simplifies the future work: we drop use of indirection in
the assertion now.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@openvz.org>
---
block/snapshot.c | 30 ++++++++++--------------------
1 file changed, 10 insertions(+), 20 deletions(-)
diff --git a/block/snapshot.c b/block/snapshot.c
index d6f53c3065..f4ec4f9ef3 100644
--- a/block/snapshot.c
+++ b/block/snapshot.c
@@ -161,21 +161,14 @@ bool bdrv_snapshot_find_by_id_and_name(BlockDriverState
*bs,
static BdrvChild **bdrv_snapshot_fallback_ptr(BlockDriverState *bs)
{
BdrvChild **fallback;
- BdrvChild *child;
+ BdrvChild *child = bdrv_primary_child(bs);
- /*
- * The only BdrvChild pointers that are safe to modify (and which
- * we can thus return a reference to) are bs->file and
- * bs->backing.
- */
- fallback = &bs->file;
- if (!*fallback && bs->drv && bs->drv->is_filter) {
- fallback = &bs->backing;
- }
-
- if (!*fallback) {
+ /* We allow fallback only to primary child */
+ if (!child) {
return NULL;
}
+ fallback = (child == bs->file ? &bs->file : &bs->backing);
+ assert(*fallback == child);
/*
* Check that there are no other children that would need to be
@@ -309,15 +302,12 @@ int bdrv_snapshot_goto(BlockDriverState *bs,
}
/*
- * fallback_ptr is &bs->file or &bs->backing. *fallback_ptr
- * was closed above and set to NULL, but the .bdrv_open() call
- * has opened it again, because we set the respective option
- * (with the qdict_put_str() call above).
- * Assert that .bdrv_open() has attached some child on
- * *fallback_ptr, and that it has attached the one we wanted
- * it to (i.e., fallback_bs).
+ * fallback was a primary child. It was closed above and set to NULL,
+ * but the .bdrv_open() call has opened it again, because we set the
+ * respective option (with the qdict_put_str() call above).
+ * Assert that .bdrv_open() has attached some BDS as primary child.
*/
- assert(*fallback_ptr && fallback_bs == (*fallback_ptr)->bs);
+ assert(bdrv_primary_bs(bs) == fallback_bs);
bdrv_unref(fallback_bs);
return ret;
}
--
2.35.1
- [PATCH v5 00/45] Transactional block-graph modifying API, Vladimir Sementsov-Ogievskiy, 2022/03/30
- [PATCH v5 01/45] block: BlockDriver: add .filtered_child_is_backing field, Vladimir Sementsov-Ogievskiy, 2022/03/30
- [PATCH v5 07/45] block: document connection between child roles and bs->backing/bs->file, Vladimir Sementsov-Ogievskiy, 2022/03/30
- [PATCH v5 20/45] block: make permission update functions public, Vladimir Sementsov-Ogievskiy, 2022/03/30
- [PATCH v5 31/45] qapi: block: add blockdev-add transaction action, Vladimir Sementsov-Ogievskiy, 2022/03/30
- [PATCH v5 37/45] qapi: add x-blockdev-replace command, Vladimir Sementsov-Ogievskiy, 2022/03/30
- [PATCH v5 02/45] block: introduce bdrv_open_file_child() helper, Vladimir Sementsov-Ogievskiy, 2022/03/30
- [PATCH v5 04/45] test-bdrv-graph-mod: update test_parallel_perm_update test case, Vladimir Sementsov-Ogievskiy, 2022/03/30
- [PATCH v5 05/45] tests-bdrv-drain: bdrv_replace_test driver: declare supports_backing, Vladimir Sementsov-Ogievskiy, 2022/03/30
- [PATCH v5 08/45] block/snapshot: stress that we fallback to primary child,
Vladimir Sementsov-Ogievskiy <=
- [PATCH v5 14/45] block/snapshot: drop indirection around bdrv_snapshot_fallback_ptr, Vladimir Sementsov-Ogievskiy, 2022/03/30
- [PATCH v5 17/45] block: drop bdrv_remove_filter_or_cow_child, Vladimir Sementsov-Ogievskiy, 2022/03/30
- [PATCH v5 28/45] qapi: block: add blockdev-del transaction action, Vladimir Sementsov-Ogievskiy, 2022/03/30
- [PATCH v5 35/45] block: make bdrv_find_child() function public, Vladimir Sementsov-Ogievskiy, 2022/03/30
- [PATCH v5 09/45] Revert "block: Let replace_child_noperm free children", Vladimir Sementsov-Ogievskiy, 2022/03/30
- [PATCH v5 10/45] Revert "block: Let replace_child_tran keep indirect pointer", Vladimir Sementsov-Ogievskiy, 2022/03/30
- [PATCH v5 13/45] block: Manipulate bs->file / bs->backing pointers in .attach/.detach, Vladimir Sementsov-Ogievskiy, 2022/03/30
- [PATCH v5 38/45] qapi: add x-blockdev-replace transaction action, Vladimir Sementsov-Ogievskiy, 2022/03/30
- [PATCH v5 41/45] iotests.py: introduce VM.assert_edges_list() method, Vladimir Sementsov-Ogievskiy, 2022/03/30
- [PATCH v5 40/45] iotests.py: qemu_img_create: use imgfmt by default, Vladimir Sementsov-Ogievskiy, 2022/03/30