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.