block/mirror: Refresh stale bitmap iterator cache

If the drive's dirty bitmap is dirtied while the mirror operation is running, the cache of the iterator used by the mirror code may become stale and not contain all dirty bits. This only becomes an issue if we are looking for contiguously dirty chunks on the drive. In that case, we can easily detect the discrepancy and just refresh the iterator if one occurs. Signed-off-by: Max Reitz <[email protected]> Reviewed-by: Fam Zheng <[email protected]> Signed-off-by: Kevin Wolf <[email protected]>
sisnkemp · Apr 20, 2016 · f27a274 · f27a274
1 parent 9c83625
commit f27a274
Showing 1 changed file with 5 additions and 0 deletions.
diff --git a/block/mirror.c b/block/mirror.c
@@ -334,6 +334,11 @@ static uint64_t coroutine_fn mirror_iteration(MirrorBlockJob *s)
         }
 
         hbitmap_next = hbitmap_iter_next(&s->hbi);
+        if (hbitmap_next > next_sector || hbitmap_next < 0) {
+            /* The bitmap iterator's cache is stale, refresh it */
+            bdrv_set_dirty_iter(&s->hbi, next_sector);
+            hbitmap_next = hbitmap_iter_next(&s->hbi);
+        }
         assert(hbitmap_next == next_sector);
         nb_chunks++;
     }