block: allow customizing the granularity of the dirty bitmap

Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 10 insertions, 7 deletions

diff --git a/block.c b/block.c
index a27454453e..ba67c0def2 100644
--- a/block.c
+++ b/block.c
@@ -2833,6 +2833,8 @@ BlockInfo *bdrv_query_info(BlockDriverState *bs)
         info->has_dirty = true;
         info->dirty = g_malloc0(sizeof(*info->dirty));
         info->dirty->count = bdrv_get_dirty_count(bs) * BDRV_SECTOR_SIZE;
+        info->dirty->granularity =
+            ((int64_t) BDRV_SECTOR_SIZE << hbitmap_granularity(bs->dirty_bitmap));
     }
 
     if (bs->drv) {
@@ -4299,16 +4301,17 @@ bool bdrv_qiov_is_aligned(BlockDriverState *bs, QEMUIOVector *qiov)
     return true;
 }
 
-void bdrv_set_dirty_tracking(BlockDriverState *bs, int enable)
+void bdrv_set_dirty_tracking(BlockDriverState *bs, int granularity)
 {
     int64_t bitmap_size;
 
-    if (enable) {
-        if (!bs->dirty_bitmap) {
-            bitmap_size = (bdrv_getlength(bs) >> BDRV_SECTOR_BITS);
-            bs->dirty_bitmap = hbitmap_alloc(bitmap_size,
-                                             BDRV_LOG_SECTORS_PER_DIRTY_CHUNK);
-        }
+    assert((granularity & (granularity - 1)) == 0);
+
+    if (granularity) {
+        granularity >>= BDRV_SECTOR_BITS;
+        assert(!bs->dirty_bitmap);
+        bitmap_size = (bdrv_getlength(bs) >> BDRV_SECTOR_BITS);
+        bs->dirty_bitmap = hbitmap_alloc(bitmap_size, ffs(granularity) - 1);
     } else {
         if (bs->dirty_bitmap) {
             hbitmap_free(bs->dirty_bitmap);