[Qemu-block] [PATCH 3/5] backup: init copy_bitmap from sync_bitmap for incremental

[Vladimir Sementsov-Ogievskiy]

We should not copy non-dirty clusters in write notifiers. So,
initialize copy_bitmap from sync_bitmap.

Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
---
 block/backup.c | 45 ++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 44 insertions(+), 1 deletion(-)

diff --git a/block/backup.c b/block/backup.c
index 08efec639f..07f4ae846b 100644
--- a/block/backup.c
+++ b/block/backup.c
@@ -422,6 +422,43 @@ out:
     return ret;
 }
 
+/* init copy_bitmap from sync_bitmap */
+static void backup_incremental_init_copy_bitmap(BackupBlockJob *job)
+{
+    BdrvDirtyBitmapIter *dbi;
+    int64_t offset;
+    int64_t end = DIV_ROUND_UP(bdrv_dirty_bitmap_size(job->sync_bitmap),
+                               job->cluster_size);
+
+    dbi = bdrv_dirty_iter_new(job->sync_bitmap);
+    while ((offset = bdrv_dirty_iter_next(dbi)) != -1) {
+        int64_t cluster = offset / job->cluster_size;
+        int64_t next_cluster;
+
+        offset += bdrv_dirty_bitmap_granularity(job->sync_bitmap);
+        if (offset >= bdrv_dirty_bitmap_size(job->sync_bitmap)) {
+            hbitmap_set(job->copy_bitmap, cluster, end - cluster);
+            break;
+        }
+
+        offset = bdrv_dirty_bitmap_next_zero(job->sync_bitmap, offset);
+        if (offset == -1) {
+            hbitmap_set(job->copy_bitmap, cluster, end - cluster);
+            break;
+        }
+
+        next_cluster = DIV_ROUND_UP(offset, job->cluster_size);
+        hbitmap_set(job->copy_bitmap, cluster, next_cluster - cluster);
+        if (next_cluster >= end) {
+            break;
+        }
+
+        bdrv_set_dirty_iter(dbi, next_cluster * job->cluster_size);
+    }
+
+    bdrv_dirty_iter_free(dbi);
+}
+
 static void coroutine_fn backup_run(void *opaque)
 {
     BackupBlockJob *job = opaque;
@@ -435,20 +472,26 @@ static void coroutine_fn backup_run(void *opaque)
 
     nb_clusters = DIV_ROUND_UP(job->common.len, job->cluster_size);
     job->copy_bitmap = hbitmap_alloc(nb_clusters, 0);
-    hbitmap_set(job->copy_bitmap, 0, nb_clusters);
 
     job->before_write.notify = backup_before_write_notify;
     bdrv_add_before_write_notifier(bs, &job->before_write);
 
     if (job->sync_mode == MIRROR_SYNC_MODE_NONE) {
+        /* Here we set all bits in job->copy_bitmap to allow copying clusters
+         * which are going to be changed (none-mode semantics). It doesn't mean
+         * that we want to copy _all_ clusters.
+         */
+        hbitmap_set(job->copy_bitmap, 0, nb_clusters);
         while (!block_job_is_cancelled(&job->common)) {
             /* Yield until the job is cancelled.  We just let our before_write
              * notify callback service CoW requests. */
             block_job_yield(&job->common);
         }
     } else if (job->sync_mode == MIRROR_SYNC_MODE_INCREMENTAL) {
+        backup_incremental_init_copy_bitmap(job);
         ret = backup_run_incremental(job);
     } else {
+        hbitmap_set(job->copy_bitmap, 0, nb_clusters);
         /* Both FULL and TOP SYNC_MODE's require copying.. */
         for (offset = 0; offset < job->common.len;
              offset += job->cluster_size) {
-- 
2.11.1