From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: John Snow <jsnow@redhat.com>
Date: Mon, 6 Apr 2020 12:17:04 +0200
Subject: [PATCH] drive-mirror: add support for conditional and always bitmap
 sync modes
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Teach mirror two new tricks for using bitmaps:

Always: no matter what, we synchronize the copy_bitmap back to the
sync_bitmap. In effect, this allows us resume a failed mirror at a later
date.

Conditional: On success only, we sync the bitmap. This is akin to
incremental backup modes; we can use this bitmap to later refresh a
successfully created mirror.

Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
---
 block/mirror.c | 24 ++++++++++++++++++------
 1 file changed, 18 insertions(+), 6 deletions(-)

diff --git a/block/mirror.c b/block/mirror.c
index 9099c75992..e2ff42067b 100644
--- a/block/mirror.c
+++ b/block/mirror.c
@@ -680,8 +680,6 @@ static int mirror_exit_common(Job *job)
         bdrv_unfreeze_backing_chain(mirror_top_bs, target_bs);
     }
 
-    bdrv_release_dirty_bitmap(s->dirty_bitmap);
-
     /* Make sure that the source BDS doesn't go away during bdrv_replace_node,
      * before we can call bdrv_drained_end */
     bdrv_ref(src);
@@ -782,6 +780,18 @@ static int mirror_exit_common(Job *job)
     block_job_remove_all_bdrv(bjob);
     bdrv_replace_node(mirror_top_bs, mirror_top_bs->backing->bs, &error_abort);
 
+    if (s->sync_bitmap) {
+        if (s->bitmap_mode == BITMAP_SYNC_MODE_ALWAYS ||
+            (s->bitmap_mode == BITMAP_SYNC_MODE_ON_SUCCESS &&
+             job->ret == 0 && ret == 0)) {
+            /* Success; synchronize copy back to sync. */
+            bdrv_clear_dirty_bitmap(s->sync_bitmap, NULL);
+            bdrv_merge_dirty_bitmap(s->sync_bitmap, s->dirty_bitmap,
+                                    NULL, &error_abort);
+        }
+    }
+    bdrv_release_dirty_bitmap(s->dirty_bitmap);
+
     bs_opaque->job = NULL;
 
     bdrv_drained_end(src);
@@ -1688,10 +1698,6 @@ static BlockJob *mirror_start_job(
                        " sync mode",
                        MirrorSyncMode_str(sync_mode));
             return NULL;
-        } else if (bitmap_mode != BITMAP_SYNC_MODE_NEVER) {
-            error_setg(errp,
-                       "Bitmap Sync Mode '%s' is not supported by Mirror",
-                       BitmapSyncMode_str(bitmap_mode));
         }
     } else if (bitmap) {
         error_setg(errp,
@@ -1708,6 +1714,12 @@ static BlockJob *mirror_start_job(
             return NULL;
         }
         granularity = bdrv_dirty_bitmap_granularity(bitmap);
+
+        if (bitmap_mode != BITMAP_SYNC_MODE_NEVER) {
+            if (bdrv_dirty_bitmap_check(bitmap, BDRV_BITMAP_DEFAULT, errp)) {
+                return NULL;
+            }
+        }
     } else if (granularity == 0) {
         granularity = bdrv_get_default_bitmap_granularity(target);
     }
