Re: [libvirt] [PATCH v2 2/6] block/dirty-bitmaps: rename frozen predicate helper
On 2/18/19 8:57 AM, Vladimir Sementsov-Ogievskiy wrote:
14.02.2019 2:23, John Snow wrote:
> "Frozen" was a good description a long time ago, but it isn't adequate
now.
> Rename the frozen predicate to has_successor to make the semantics of the
> predicate more clear to outside callers.
>
> In the process, remove some calls to frozen() that no longer semantically
> make sense. For enabled and disabled in particular, it's actually okay for
> the internals to do this but only forbidden for users to invoke them, and
I'm a bit lost in this paragraph.. to this - what?, to invoke them - whom?
I think, it would be simpler for me to read patch itself :)
Touched this up. I meant enable and disable, not enabled and disabled.
> all of the QMP entry uses already check against qmp_locked.
>
> Several other assertions really want to check that the bitmap isn't in-use
> by another operation -- use the qmp_locked function for this instead, which
> presently also checks for has_successor.
hm, you mean user_locked, not qmp_locked.
Yes.
[...]
> /**
> * Create a successor bitmap destined to replace this bitmap after an operation.
> - * Requires that the bitmap is not frozen and has no successor.
> + * Requires that the bitmap is not locked and has no successor.
I think, user_locked, to not interfere with bitmaps mutex. And you use user_locked in
other comments in this patch.
You're right. It gets changed again later, but I didn't make this easy
to read.
> * Called with BQL taken.
> */
> int bdrv_dirty_bitmap_create_successor(BlockDriverState *bs,
> @@ -244,12 +244,16 @@ int bdrv_dirty_bitmap_create_successor(BlockDriverState *bs,
> uint64_t granularity;
> BdrvDirtyBitmap *child;
>
> - if (bdrv_dirty_bitmap_frozen(bitmap)) {
> - error_setg(errp, "Cannot create a successor for a bitmap that is
"
> - "currently frozen");
> + if (bdrv_dirty_bitmap_user_locked(bitmap)) {
> + error_setg(errp, "Cannot create a successor for a bitmap that is in-use
"
> + "by an operation");
> + return -1;
> + }
> + if (bdrv_dirty_bitmap_has_successor(bitmap)) {
> + error_setg(errp, "Cannot create a successor for a bitmap that already
"
> + "has one");
Amm, dead code? _user_locked() implies no successor, so we instead can keep an
assertion..
It gets changed later in the series, but I didn't do a great job of
explaining that in advance. I'll amend the commit message to explain
what I'm trying to do.
I tried to hint at this with: "which presently also checks for
has_successor" as an admission that it was redundant, but I need to call
it out in stronger language.