[PATCH 10/11] block/copy-before-write: add cbw_snapshot_discard()

[Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>]

To be used soon.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 block/copy-before-write.h |  1 +
 block/copy-before-write.c | 11 +++++++++++
 2 files changed, 12 insertions(+)

diff --git a/block/copy-before-write.h b/block/copy-before-write.h
index a7e286620c..5809ffc7d0 100644
--- a/block/copy-before-write.h
+++ b/block/copy-before-write.h
@@ -40,5 +40,6 @@ void bdrv_cbw_drop(BlockDriverState *bs);
 int cbw_snapshot_read_lock(BlockDriverState *bs, int64_t offset,
                            int64_t bytes, const BlockReq **req, int64_t *pnum);
 void cbw_snapshot_read_unlock(BlockDriverState *bs, const BlockReq *req);
+void cbw_snapshot_discard(BlockDriverState *bs, int64_t offset, int64_t bytes);
 
 #endif /* COPY_BEFORE_WRITE_H */
diff --git a/block/copy-before-write.c b/block/copy-before-write.c
index a96131358e..a9fc8e34e9 100644
--- a/block/copy-before-write.c
+++ b/block/copy-before-write.c
@@ -103,6 +103,17 @@ void cbw_snapshot_read_unlock(BlockDriverState *bs, const BlockReq *req)
     drop_read_req(s, (BlockReq *)req);
 }
 
+void cbw_snapshot_discard(BlockDriverState *bs, int64_t offset, int64_t bytes)
+{
+    BDRVCopyBeforeWriteState *s = bs->opaque;
+
+    WITH_QEMU_LOCK_GUARD(&s->lock) {
+        bdrv_reset_dirty_bitmap(s->access_bitmap, offset, bytes);
+    }
+
+    block_copy_reset(s->bcs, offset, bytes);
+}
+
 static coroutine_fn int cbw_co_preadv(
         BlockDriverState *bs, uint64_t offset, uint64_t bytes,
         QEMUIOVector *qiov, int flags)
-- 
2.29.2