hbitmap: add next_zero function

The function searches for next zero bit.
Also add interface for BdrvDirtyBitmap and unit test.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Message-id: 20171012135313.227864-2-vsementsov@virtuozzo.com
Signed-off-by: Jeff Cody <jcody@redhat.com>

block/dirty-bitmap.c

@@ -715,3 +715,8 @@ char *bdrv_dirty_bitmap_sha256(const BdrvDirtyBitmap *bitmap, Error **errp)
 {
     return hbitmap_sha256(bitmap->bitmap, errp);
 }
+
+int64_t bdrv_dirty_bitmap_next_zero(BdrvDirtyBitmap *bitmap, uint64_t offset)
+{
+    return hbitmap_next_zero(bitmap->bitmap, offset);
+}

include/block/dirty-bitmap.h

@@ -91,5 +91,6 @@ bool bdrv_has_changed_persistent_bitmaps(BlockDriverState *bs);
 BdrvDirtyBitmap *bdrv_dirty_bitmap_next(BlockDriverState *bs,
                                         BdrvDirtyBitmap *bitmap);
 char *bdrv_dirty_bitmap_sha256(const BdrvDirtyBitmap *bitmap, Error **errp);
+int64_t bdrv_dirty_bitmap_next_zero(BdrvDirtyBitmap *bitmap, uint64_t start);
 
 #endif

include/qemu/hbitmap.h

@@ -292,6 +292,14 @@ void hbitmap_iter_init(HBitmapIter *hbi, const HBitmap *hb, uint64_t first);
  */
 unsigned long hbitmap_iter_skip_words(HBitmapIter *hbi);
 
+/* hbitmap_next_zero:
+ * @hb: The HBitmap to operate on
+ * @start: The bit to start from.
+ *
+ * Find next not dirty bit.
+ */
+int64_t hbitmap_next_zero(const HBitmap *hb, uint64_t start);
+
 /* hbitmap_create_meta:
  * Create a "meta" hbitmap to track dirtiness of the bits in this HBitmap.
  * The caller owns the created bitmap and must call hbitmap_free_meta(hb) to

tests/test-hbitmap.c

@@ -925,6 +925,61 @@ static void test_hbitmap_iter_and_reset(TestHBitmapData *data,
     hbitmap_iter_next(&hbi);
 }
 
+static void test_hbitmap_next_zero_check(TestHBitmapData *data, int64_t start)
+{
+    int64_t ret1 = hbitmap_next_zero(data->hb, start);
+    int64_t ret2 = start;
+    for ( ; ret2 < data->size && hbitmap_get(data->hb, ret2); ret2++) {
+        ;
+    }
+    if (ret2 == data->size) {
+        ret2 = -1;
+    }
+
+    g_assert_cmpint(ret1, ==, ret2);
+}
+
+static void test_hbitmap_next_zero_do(TestHBitmapData *data, int granularity)
+{
+    hbitmap_test_init(data, L3, granularity);
+    test_hbitmap_next_zero_check(data, 0);
+    test_hbitmap_next_zero_check(data, L3 - 1);
+
+    hbitmap_set(data->hb, L2, 1);
+    test_hbitmap_next_zero_check(data, 0);
+    test_hbitmap_next_zero_check(data, L2 - 1);
+    test_hbitmap_next_zero_check(data, L2);
+    test_hbitmap_next_zero_check(data, L2 + 1);
+
+    hbitmap_set(data->hb, L2 + 5, L1);
+    test_hbitmap_next_zero_check(data, 0);
+    test_hbitmap_next_zero_check(data, L2 + 1);
+    test_hbitmap_next_zero_check(data, L2 + 2);
+    test_hbitmap_next_zero_check(data, L2 + 5);
+    test_hbitmap_next_zero_check(data, L2 + L1 - 1);
+    test_hbitmap_next_zero_check(data, L2 + L1);
+
+    hbitmap_set(data->hb, L2 * 2, L3 - L2 * 2);
+    test_hbitmap_next_zero_check(data, L2 * 2 - L1);
+    test_hbitmap_next_zero_check(data, L2 * 2 - 2);
+    test_hbitmap_next_zero_check(data, L2 * 2 - 1);
+    test_hbitmap_next_zero_check(data, L2 * 2);
+    test_hbitmap_next_zero_check(data, L3 - 1);
+
+    hbitmap_set(data->hb, 0, L3);
+    test_hbitmap_next_zero_check(data, 0);
+}
+
+static void test_hbitmap_next_zero_0(TestHBitmapData *data, const void *unused)
+{
+    test_hbitmap_next_zero_do(data, 0);
+}
+
+static void test_hbitmap_next_zero_4(TestHBitmapData *data, const void *unused)
+{
+    test_hbitmap_next_zero_do(data, 4);
+}
+
 int main(int argc, char **argv)
 {
     g_test_init(&argc, &argv, NULL);
@@ -985,6 +1040,12 @@ int main(int argc, char **argv)
 
     hbitmap_test_add("/hbitmap/iter/iter_and_reset",
                      test_hbitmap_iter_and_reset);
+
+    hbitmap_test_add("/hbitmap/next_zero/next_zero_0",
+                     test_hbitmap_next_zero_0);
+    hbitmap_test_add("/hbitmap/next_zero/next_zero_4",
+                     test_hbitmap_next_zero_4);
+
     g_test_run();
 
     return 0;

util/hbitmap.c

@@ -188,6 +188,45 @@ void hbitmap_iter_init(HBitmapIter *hbi, const HBitmap *hb, uint64_t first)
     }
 }
 
+int64_t hbitmap_next_zero(const HBitmap *hb, uint64_t start)
+{
+    size_t pos = (start >> hb->granularity) >> BITS_PER_LEVEL;
+    unsigned long *last_lev = hb->levels[HBITMAP_LEVELS - 1];
+    uint64_t sz = hb->sizes[HBITMAP_LEVELS - 1];
+    unsigned long cur = last_lev[pos];
+    unsigned start_bit_offset =
+            (start >> hb->granularity) & (BITS_PER_LONG - 1);
+    int64_t res;
+
+    cur |= (1UL << start_bit_offset) - 1;
+    assert((start >> hb->granularity) < hb->size);
+
+    if (cur == (unsigned long)-1) {
+        do {
+            pos++;
+        } while (pos < sz && last_lev[pos] == (unsigned long)-1);
+
+        if (pos >= sz) {
+            return -1;
+        }
+
+        cur = last_lev[pos];
+    }
+
+    res = (pos << BITS_PER_LEVEL) + ctol(cur);
+    if (res >= hb->size) {
+        return -1;
+    }
+
+    res = res << hb->granularity;
+    if (res < start) {
+        assert(((start - res) >> hb->granularity) == 0);
+        return start;
+    }
+
+    return res;
+}
+
 bool hbitmap_empty(const HBitmap *hb)
 {
     return hb->count == 0;