From ef893b5c84f3199d777e33966dc28839f71b1a5c Mon Sep 17 00:00:00 2001 From: Eric Blake Date: Tue, 12 May 2020 20:16:42 -0500 Subject: block: Make it easier to learn which BDS support bitmaps Upcoming patches will enhance bitmap support in qemu-img, but in doing so, it turns out to be nice to suppress output when persistent bitmaps make no sense (such as on a qcow2 v2 image). Add a hook to make this easier to query. This patch adds a new callback .bdrv_supports_persistent_dirty_bitmap, rather than trying to shoehorn the answer in via existing callbacks. In particular, while it might have been possible to overload .bdrv_co_can_store_new_dirty_bitmap to special-case a NULL input to answer whether any persistent bitmaps are supported, that is at odds with whether a particular bitmap can be stored (for example, even on an image that supports persistent bitmaps but has currently filled up the maximum number of bitmaps, attempts to store another one should fail); and the new functionality doesn't require coroutine safety. Similarly, we could have added one more piece of information to .bdrv_get_info, but then again, most callers to that function tend to already discard extraneous information, and making it a catch-all rather than a series of dedicated scalar queries hasn't really simplified life. In the future, when we improve the ability to look up bitmaps through a filter, we will probably also want to teach the block layer to automatically let filters pass this request on through. Signed-off-by: Eric Blake Message-Id: <20200513011648.166876-4-eblake@redhat.com> Reviewed-by: Vladimir Sementsov-Ogievskiy --- block/qcow2.h | 1 + 1 file changed, 1 insertion(+) (limited to 'block/qcow2.h') diff --git a/block/qcow2.h b/block/qcow2.h index 6a8b82e6cc..402e8acb1c 100644 --- a/block/qcow2.h +++ b/block/qcow2.h @@ -782,6 +782,7 @@ bool qcow2_co_can_store_new_dirty_bitmap(BlockDriverState *bs, int qcow2_co_remove_persistent_dirty_bitmap(BlockDriverState *bs, const char *name, Error **errp); +bool qcow2_supports_persistent_dirty_bitmap(BlockDriverState *bs); ssize_t coroutine_fn qcow2_co_compress(BlockDriverState *bs, void *dest, size_t dest_size, -- cgit v1.2.3