block/backup: Add mirror sync mode 'bitmap'

We don't need or want a new sync mode for simple differences in
semantics.  Create a new mode simply named "BITMAP" that is designed to
make use of the new Bitmap Sync Mode field.

Because the only bitmap sync mode is 'on-success', this adds no new
functionality to the backup job (yet). The old incremental backup mode
is maintained as a syntactic sugar for sync=bitmap, mode=on-success.

Add all of the plumbing necessary to support this new instruction.

Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-id: 20190709232550.10724-6-jsnow@redhat.com
Signed-off-by: John Snow <jsnow@redhat.com>

block/backup.c

@@ -38,9 +38,9 @@ typedef struct CowRequest {
 typedef struct BackupBlockJob {
     BlockJob common;
     BlockBackend *target;
-    /* bitmap for sync=incremental */
     BdrvDirtyBitmap *sync_bitmap;
     MirrorSyncMode sync_mode;
+    BitmapSyncMode bitmap_mode;
     BlockdevOnError on_source_error;
     BlockdevOnError on_target_error;
     CoRwlock flush_rwlock;
@@ -461,7 +461,7 @@ static int coroutine_fn backup_run(Job *job, Error **errp)
 
     job_progress_set_remaining(job, s->len);
 
-    if (s->sync_mode == MIRROR_SYNC_MODE_INCREMENTAL) {
+    if (s->sync_mode == MIRROR_SYNC_MODE_BITMAP) {
         backup_incremental_init_copy_bitmap(s);
     } else {
         hbitmap_set(s->copy_bitmap, 0, s->len);
@@ -545,6 +545,7 @@ static int64_t backup_calculate_cluster_size(BlockDriverState *target,
 BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs,
                   BlockDriverState *target, int64_t speed,
                   MirrorSyncMode sync_mode, BdrvDirtyBitmap *sync_bitmap,
+                  BitmapSyncMode bitmap_mode,
                   bool compress,
                   BlockdevOnError on_source_error,
                   BlockdevOnError on_target_error,
@@ -592,10 +593,13 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs,
         return NULL;
     }
 
-    if (sync_mode == MIRROR_SYNC_MODE_INCREMENTAL) {
+    /* QMP interface should have handled translating this to bitmap mode */
+    assert(sync_mode != MIRROR_SYNC_MODE_INCREMENTAL);
+
+    if (sync_mode == MIRROR_SYNC_MODE_BITMAP) {
         if (!sync_bitmap) {
             error_setg(errp, "must provide a valid bitmap name for "
-                             "\"incremental\" sync mode");
+                       "'%s' sync mode", MirrorSyncMode_str(sync_mode));
             return NULL;
         }
 
@@ -605,8 +609,8 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs,
         }
     } else if (sync_bitmap) {
         error_setg(errp,
-                   "a sync_bitmap was provided to backup_run, "
-                   "but received an incompatible sync_mode (%s)",
+                   "a bitmap was given to backup_job_create, "
+                   "but it received an incompatible sync_mode (%s)",
                    MirrorSyncMode_str(sync_mode));
         return NULL;
     }
@@ -649,8 +653,8 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs,
     job->on_source_error = on_source_error;
     job->on_target_error = on_target_error;
     job->sync_mode = sync_mode;
-    job->sync_bitmap = sync_mode == MIRROR_SYNC_MODE_INCREMENTAL ?
-                       sync_bitmap : NULL;
+    job->sync_bitmap = sync_bitmap;
+    job->bitmap_mode = bitmap_mode;
     job->compress = compress;
 
     /* Detect image-fleecing (and similar) schemes */

block/mirror.c

@@ -1755,8 +1755,10 @@ void mirror_start(const char *job_id, BlockDriverState *bs,
     bool is_none_mode;
     BlockDriverState *base;
 
-    if (mode == MIRROR_SYNC_MODE_INCREMENTAL) {
-        error_setg(errp, "Sync mode 'incremental' not supported");
+    if ((mode == MIRROR_SYNC_MODE_INCREMENTAL) ||
+        (mode == MIRROR_SYNC_MODE_BITMAP)) {
+        error_setg(errp, "Sync mode '%s' not supported",
+                   MirrorSyncMode_str(mode));
         return;
     }
     is_none_mode = mode == MIRROR_SYNC_MODE_NONE;

block/replication.c

@@ -543,7 +543,7 @@ static void replication_start(ReplicationState *rs, ReplicationMode mode,
 
         s->backup_job = backup_job_create(
                                 NULL, s->secondary_disk->bs, s->hidden_disk->bs,
-                                0, MIRROR_SYNC_MODE_NONE, NULL, false,
+                                0, MIRROR_SYNC_MODE_NONE, NULL, 0, false,
                                 BLOCKDEV_ON_ERROR_REPORT,
                                 BLOCKDEV_ON_ERROR_REPORT, JOB_INTERNAL,
                                 backup_job_completed, bs, NULL, &local_err);

blockdev.c

@@ -3466,12 +3466,31 @@ static BlockJob *do_backup_common(BackupCommon *backup,
         return NULL;
     }
 
+    if (backup->sync == MIRROR_SYNC_MODE_INCREMENTAL) {
+        if (backup->has_bitmap_mode &&
+            backup->bitmap_mode != BITMAP_SYNC_MODE_ON_SUCCESS) {
+            error_setg(errp, "Bitmap sync mode must be '%s' "
+                       "when using sync mode '%s'",
+                       BitmapSyncMode_str(BITMAP_SYNC_MODE_ON_SUCCESS),
+                       MirrorSyncMode_str(backup->sync));
+            return NULL;
+        }
+        backup->has_bitmap_mode = true;
+        backup->sync = MIRROR_SYNC_MODE_BITMAP;
+        backup->bitmap_mode = BITMAP_SYNC_MODE_ON_SUCCESS;
+    }
+
     if (backup->has_bitmap) {
         bmap = bdrv_find_dirty_bitmap(bs, backup->bitmap);
         if (!bmap) {
             error_setg(errp, "Bitmap '%s' could not be found", backup->bitmap);
             return NULL;
         }
+        if (!backup->has_bitmap_mode) {
+            error_setg(errp, "Bitmap sync mode must be given "
+                       "when providing a bitmap");
+            return NULL;
+        }
         if (bdrv_dirty_bitmap_check(bmap, BDRV_BITMAP_DEFAULT, errp)) {
             return NULL;
         }
@@ -3485,8 +3504,10 @@ static BlockJob *do_backup_common(BackupCommon *backup,
     }
 
     job = backup_job_create(backup->job_id, bs, target_bs, backup->speed,
-                            backup->sync, bmap, backup->compress,
-                            backup->on_source_error, backup->on_target_error,
+                            backup->sync, bmap, backup->bitmap_mode,
+                            backup->compress,
+                            backup->on_source_error,
+                            backup->on_target_error,
                             job_flags, NULL, NULL, txn, errp);
     return job;
 }

include/block/block_int.h

@@ -1147,7 +1147,8 @@ void mirror_start(const char *job_id, BlockDriverState *bs,
  * @target: Block device to write to.
  * @speed: The maximum speed, in bytes per second, or 0 for unlimited.
  * @sync_mode: What parts of the disk image should be copied to the destination.
- * @sync_bitmap: The dirty bitmap if sync_mode is MIRROR_SYNC_MODE_INCREMENTAL.
+ * @sync_bitmap: The dirty bitmap if sync_mode is 'bitmap' or 'incremental'
+ * @bitmap_mode: The bitmap synchronization policy to use.
  * @on_source_error: The action to take upon error reading from the source.
  * @on_target_error: The action to take upon error writing to the target.
  * @creation_flags: Flags that control the behavior of the Job lifetime.
@@ -1163,6 +1164,7 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs,
                             BlockDriverState *target, int64_t speed,
                             MirrorSyncMode sync_mode,
                             BdrvDirtyBitmap *sync_bitmap,
+                            BitmapSyncMode bitmap_mode,
                             bool compress,
                             BlockdevOnError on_source_error,
                             BlockdevOnError on_target_error,

qapi/block-core.json

@@ -1127,12 +1127,15 @@
 #
 # @none: only copy data written from now on
 #
-# @incremental: only copy data described by the dirty bitmap. Since: 2.4
+# @incremental: only copy data described by the dirty bitmap. (since: 2.4)
+#
+# @bitmap: only copy data described by the dirty bitmap. (since: 4.2)
+#          Behavior on completion is determined by the BitmapSyncMode.
 #
 # Since: 1.3
 ##
 { 'enum': 'MirrorSyncMode',
-  'data': ['top', 'full', 'none', 'incremental'] }
+  'data': ['top', 'full', 'none', 'incremental', 'bitmap'] }
 
 ##
 # @BitmapSyncMode:
@@ -1343,9 +1346,14 @@
 # @speed: the maximum speed, in bytes per second. The default is 0,
 #         for unlimited.
 #
-# @bitmap: the name of dirty bitmap if sync is "incremental".
-#          Must be present if sync is "incremental", must NOT be present
-#          otherwise. (Since 2.4 (drive-backup), 3.1 (blockdev-backup))
+# @bitmap: the name of a dirty bitmap if sync is "bitmap" or "incremental".
+#          Must be present if sync is "bitmap" or "incremental".
+#          Must not be present otherwise.
+#          (Since 2.4 (drive-backup), 3.1 (blockdev-backup))
+#
+# @bitmap-mode: Specifies the type of data the bitmap should contain after
+#               the operation concludes. Must be present if sync is "bitmap".
+#               Must NOT be present otherwise. (Since 4.2)
 #
 # @compress: true to compress data, if the target format supports it.
 #            (default: false) (since 2.8)
@@ -1380,7 +1388,8 @@
 { 'struct': 'BackupCommon',
   'data': { '*job-id': 'str', 'device': 'str',
             'sync': 'MirrorSyncMode', '*speed': 'int',
-            '*bitmap': 'str', '*compress': 'bool',
+            '*bitmap': 'str', '*bitmap-mode': 'BitmapSyncMode',
+            '*compress': 'bool',
             '*on-source-error': 'BlockdevOnError',
             '*on-target-error': 'BlockdevOnError',
             '*auto-finalize': 'bool', '*auto-dismiss': 'bool' } }