Am 26.04.2021 um 19:18 hat Vladimir Sementsov-Ogievskiy geschrieben:
26.04.2021 19:26, Kevin Wolf wrote:
Am 17.03.2021 um 15:35 hat Vladimir Sementsov-Ogievskiy geschrieben:
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
block.c | 78 +++++++++++++++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 76 insertions(+), 2 deletions(-)
diff --git a/block.c b/block.c
index 11f7ad0818..2fca1f2ad5 100644
--- a/block.c
+++ b/block.c
@@ -2929,12 +2929,19 @@ static void bdrv_replace_child(BdrvChild *child,
BlockDriverState *new_bs)
}
}
+static void bdrv_child_free(void *opaque)
+{
+ BdrvChild *c = opaque;
+
+ g_free(c->name);
+ g_free(c);
+}
+
static void bdrv_remove_empty_child(BdrvChild *child)
{
assert(!child->bs);
QLIST_SAFE_REMOVE(child, next);
- g_free(child->name);
- g_free(child);
+ bdrv_child_free(child);
}
typedef struct BdrvAttachChildCommonState {
@@ -4956,6 +4963,73 @@ static bool should_update_child(BdrvChild *c,
BlockDriverState *to)
return ret;
}
+typedef struct BdrvRemoveFilterOrCowChild {
+ BdrvChild *child;
+ bool is_backing;
+} BdrvRemoveFilterOrCowChild;
+
+/* this doesn't restore original child bs, only the child itself */
Hm, this comment tells me that it's intentional, but why is it correct?
that's because bdrv_remove_filter_or_cow_child_abort() aborts only
part of bdrv_remove_filter_or_cow_child().
I see that it aborts only part of it, but why?
Normally, a function getting a Transaction object suggests to me that on
failure, all changes the function made will be reverted, not just parts
of the changes.
Look: bdrv_remove_filter_or_cow_child() firstly do
bdrv_replace_child_safe(child, NULL, tran);, so bs would be restored
by .abort() of bdrv_replace_child_safe() action.
Ah! So the reason is not that we don't want to restore child->bs, but
that bdrv_replace_child_safe() is already transactionable and will
automatically do this.
So, improved comment may look like:
This doesn't restore original child bs, only the child itself. The bs
would be restored by .abort() bdrv_replace_child_safe() subation of
bdrv_remove_filter_or_cow_child() action.
"subation" is a typo for "subaction"?
Maybe something like this:
We don't have to restore child->bs here to undo bdrv_replace_child()
because that function is already transactionable and will do so in
its own .abort() callback.
Probably it would be more correct to rename
BdrvRemoveFilterOrCowChild -> BdrvRemoveFilterOrCowChildNoBs
bdrv_remove_filter_or_cow_child_abort ->
bdrv_remove_filter_or_cow_child_no_bs_abort
bdrv_remove_filter_or_cow_child_commit ->
bdrv_remove_filter_or_cow_child_no_bs_commit
and assert on .abort() and .commit() that s->child->bs is NULL.
I wouldn't bother with that. It was just that the comment confused me
because it seemed to suggest that we actually don't want to restore
child->bs, when its real intention was to say that it's already restored
somewhere else.