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Re: [Qemu-devel] [PATCH v3 04/10] block/dirty-bitmap: change semantics o
Re: [Qemu-devel] [PATCH v3 04/10] block/dirty-bitmap: change semantics of enabled predicate
Mon, 25 Feb 2019 07:39:55 +0000
23.02.2019 3:06, John Snow wrote:
> Currently, the enabled predicate means something like:
> "the QAPI status of the bitmap is ACTIVE."
> After this patch, it should mean exclusively:
> "This bitmap is recording guest writes, and is allowed to do so."
> In many places, this is how this predicate was already used.
> Internal usages of the bitmap QPI can call user_locked to find out if
> the bitmap is in use by an operation.
> To accommodate this, modify the create_successor routine to now
> explicitly disable the parent bitmap at creation time.
> 1. bdrv_dirty_bitmap_status suffers no change from the lack of
> 1:1 parity with the new predicates because of the order in which
> the predicates are checked. This is now only for compatibility.
> 2. bdrv_set_dirty() is unchanged: pre-patch, it was skipping bitmaps that were
> disabled or had a successor, while post-patch it is only skipping bitmaps
> that are disabled. To accommodate this, create_successor now ensures that
> any bitmap with a successor is explicitly disabled.
> 3. qcow2_store_persistent_dirty_bitmaps: No functional change. This function
> cares only about the literal enabled bit, and makes no effort to check if
> the bitmap is in-use or not. After this patch there are still no ways to
> produce an enabled bitmap with a successor.
> 4. block_dirty_bitmap_enable_prepare
> These functions care about the literal enabled bit,
> and already check user_locked separately.
> Signed-off-by: John Snow<address@hidden>
Reviewed-by: Vladimir Sementsov-Ogievskiy <address@hidden>
- [Qemu-devel] [PATCH v3 00/10] dirty-bitmaps: deprecate @status field, John Snow, 2019/02/22
- [Qemu-devel] [PATCH v3 02/10] block/dirty-bitmaps: rename frozen predicate helper, John Snow, 2019/02/22
- [Qemu-devel] [PATCH v3 01/10] block/dirty-bitmap: add recording and busy properties, John Snow, 2019/02/22
- [Qemu-devel] [PATCH v3 04/10] block/dirty-bitmap: change semantics of enabled predicate, John Snow, 2019/02/22
- [Qemu-devel] [PATCH v3 09/10] blockdev: remove unused paio parameter documentation, John Snow, 2019/02/22
- [Qemu-devel] [PATCH v3 06/10] block/dirty-bitmap: explicitly lock bitmaps with successors, John Snow, 2019/02/22
- [Qemu-devel] [PATCH v3 05/10] nbd: change error checking order for bitmaps, John Snow, 2019/02/22
- [Qemu-devel] [PATCH v3 10/10] iotests: add busy/recording bit test to 124, John Snow, 2019/02/22