[Qemu-devel] [PATCH 5/5] backup: use copy_bitmap in incremental backup

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

We can use copy_bitmap instead of sync_bitmap. copy_bitmap is
initialized from sync_bitmap and it is more informative: we will not try
to process data, that is already in progress (by write notifier).

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 block/backup.c | 55 +++++++++++++++++--------------------------------------
 1 file changed, 17 insertions(+), 38 deletions(-)

diff --git a/block/backup.c b/block/backup.c
index 52df7bb19e..c933cfafc3 100644
--- a/block/backup.c
+++ b/block/backup.c
@@ -362,49 +362,28 @@ static bool coroutine_fn yield_and_check(BackupBlockJob *job)
 
 static int coroutine_fn backup_run_incremental(BackupBlockJob *job)
 {
+    int ret;
     bool error_is_read;
-    int ret = 0;
-    int clusters_per_iter;
-    uint32_t granularity;
-    int64_t offset;
     int64_t cluster;
-    int64_t end;
-    BdrvDirtyBitmapIter *dbi;
-
-    granularity = bdrv_dirty_bitmap_granularity(job->sync_bitmap);
-    clusters_per_iter = MAX((granularity / job->cluster_size), 1);
-    dbi = bdrv_dirty_iter_new(job->sync_bitmap);
-
-    /* Find the next dirty sector(s) */
-    while ((offset = bdrv_dirty_iter_next(dbi)) >= 0) {
-        cluster = offset / job->cluster_size;
-
-        for (end = cluster + clusters_per_iter; cluster < end; cluster++) {
-            do {
-                if (yield_and_check(job)) {
-                    goto out;
-                }
-                ret = backup_do_cow(job, cluster * job->cluster_size,
-                                    job->cluster_size, &error_is_read,
-                                    false);
-                if ((ret < 0) &&
-                    backup_error_action(job, error_is_read, -ret) ==
-                    BLOCK_ERROR_ACTION_REPORT) {
-                    goto out;
-                }
-            } while (ret < 0);
-        }
+    HBitmapIter hbi;
 
-        /* If the bitmap granularity is smaller than the backup granularity,
-         * we need to advance the iterator pointer to the next cluster. */
-        if (granularity < job->cluster_size) {
-            bdrv_set_dirty_iter(dbi, cluster * job->cluster_size);
-        }
+    hbitmap_iter_init(&hbi, job->copy_bitmap, 0);
+    while ((cluster = hbitmap_iter_next(&hbi)) != -1) {
+        do {
+            if (yield_and_check(job)) {
+                return 0;
+            }
+            ret = backup_do_cow(job, cluster * job->cluster_size,
+                                job->cluster_size, &error_is_read, false);
+            if (ret < 0 && backup_error_action(job, error_is_read, -ret) ==
+                           BLOCK_ERROR_ACTION_REPORT)
+            {
+                return ret;
+            }
+        } while (ret < 0);
     }
 
-out:
-    bdrv_dirty_iter_free(dbi);
-    return ret;
+    return 0;
 }
 
 /* init copy_bitmap from sync_bitmap */
-- 
2.11.1