[Qemu-devel] [PATCH v2 2/3] qapi: implement block-dirty-bitmap-remove transaction action

[John Snow <jsnow@redhat.com>]

It is used to do transactional movement of the bitmap (which is
possible in conjunction with merge command). Transactional bitmap
movement is needed in scenarios with external snapshot, when we don't
want to leave copy of the bitmap in the base image.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: John Snow <jsnow@redhat.com>
---
 qapi/transaction.json          |  2 +
 include/block/dirty-bitmap.h   |  3 +-
 block.c                        |  2 +-
 block/dirty-bitmap.c           | 16 +++----
 blockdev.c                     | 79 +++++++++++++++++++++++++++++++---
 migration/block-dirty-bitmap.c |  2 +-
 6 files changed, 87 insertions(+), 17 deletions(-)

diff --git a/qapi/transaction.json b/qapi/transaction.json
index 95edb78227..da95b804aa 100644
--- a/qapi/transaction.json
+++ b/qapi/transaction.json
@@ -45,6 +45,7 @@
 #
 # - @abort: since 1.6
 # - @block-dirty-bitmap-add: since 2.5
+# - @block-dirty-bitmap-remove: since 4.1
 # - @block-dirty-bitmap-clear: since 2.5
 # - @block-dirty-bitmap-enable: since 4.0
 # - @block-dirty-bitmap-disable: since 4.0
@@ -61,6 +62,7 @@
   'data': {
        'abort': 'Abort',
        'block-dirty-bitmap-add': 'BlockDirtyBitmapAdd',
+       'block-dirty-bitmap-remove': 'BlockDirtyBitmap',
        'block-dirty-bitmap-clear': 'BlockDirtyBitmap',
        'block-dirty-bitmap-enable': 'BlockDirtyBitmap',
        'block-dirty-bitmap-disable': 'BlockDirtyBitmap',
diff --git a/include/block/dirty-bitmap.h b/include/block/dirty-bitmap.h
index 62682eb865..aa2737f41e 100644
--- a/include/block/dirty-bitmap.h
+++ b/include/block/dirty-bitmap.h
@@ -83,7 +83,8 @@ void bdrv_dirty_bitmap_set_inconsistent(BdrvDirtyBitmap *bitmap);
 void bdrv_dirty_bitmap_set_busy(BdrvDirtyBitmap *bitmap, bool busy);
 void bdrv_merge_dirty_bitmap(BdrvDirtyBitmap *dest, const BdrvDirtyBitmap *src,
                              HBitmap **backup, Error **errp);
-void bdrv_dirty_bitmap_set_migration(BdrvDirtyBitmap *bitmap, bool migration);
+void bdrv_dirty_bitmap_squelch_persistence(BdrvDirtyBitmap *bitmap,
+                                           bool squelch);
 
 /* Functions that require manual locking.  */
 void bdrv_dirty_bitmap_lock(BdrvDirtyBitmap *bitmap);
diff --git a/block.c b/block.c
index c139540f2b..b934c522eb 100644
--- a/block.c
+++ b/block.c
@@ -5316,7 +5316,7 @@ static void coroutine_fn bdrv_co_invalidate_cache(BlockDriverState *bs,
     for (bm = bdrv_dirty_bitmap_next(bs, NULL); bm;
          bm = bdrv_dirty_bitmap_next(bs, bm))
     {
-        bdrv_dirty_bitmap_set_migration(bm, false);
+        bdrv_dirty_bitmap_squelch_persistence(bm, false);
     }
 
     ret = refresh_total_sectors(bs, bs->total_sectors);
diff --git a/block/dirty-bitmap.c b/block/dirty-bitmap.c
index 95a9c2a5d8..8551f8219e 100644
--- a/block/dirty-bitmap.c
+++ b/block/dirty-bitmap.c
@@ -48,10 +48,9 @@ struct BdrvDirtyBitmap {
     bool inconsistent;          /* bitmap is persistent, but inconsistent.
                                    It cannot be used at all in any way, except
                                    a QMP user can remove it. */
-    bool migration;             /* Bitmap is selected for migration, it should
-                                   not be stored on the next inactivation
-                                   (persistent flag doesn't matter until next
-                                   invalidation).*/
+    bool squelch_persistence;   /* We are either migrating or deleting this
+                                 * bitmap; it should not be stored on the next
+                                 * inactivation. */
     QLIST_ENTRY(BdrvDirtyBitmap) list;
 };
 
@@ -757,16 +756,17 @@ void bdrv_dirty_bitmap_set_inconsistent(BdrvDirtyBitmap *bitmap)
 }
 
 /* Called with BQL taken. */
-void bdrv_dirty_bitmap_set_migration(BdrvDirtyBitmap *bitmap, bool migration)
+void bdrv_dirty_bitmap_squelch_persistence(BdrvDirtyBitmap *bitmap,
+                                           bool squelch)
 {
     qemu_mutex_lock(bitmap->mutex);
-    bitmap->migration = migration;
+    bitmap->squelch_persistence = squelch;
     qemu_mutex_unlock(bitmap->mutex);
 }
 
 bool bdrv_dirty_bitmap_get_persistence(BdrvDirtyBitmap *bitmap)
 {
-    return bitmap->persistent && !bitmap->migration;
+    return bitmap->persistent && !bitmap->squelch_persistence;
 }
 
 bool bdrv_dirty_bitmap_inconsistent(const BdrvDirtyBitmap *bitmap)
@@ -778,7 +778,7 @@ bool bdrv_has_changed_persistent_bitmaps(BlockDriverState *bs)
 {
     BdrvDirtyBitmap *bm;
     QLIST_FOREACH(bm, &bs->dirty_bitmaps, list) {
-        if (bm->persistent && !bm->readonly && !bm->migration) {
+        if (bm->persistent && !bm->readonly && !bm->squelch_persistence) {
             return true;
         }
     }
diff --git a/blockdev.c b/blockdev.c
index 01248252ca..4143ab7bbb 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -2134,6 +2134,51 @@ static void block_dirty_bitmap_merge_prepare(BlkActionState *common,
                                                 errp);
 }
 
+static BdrvDirtyBitmap *do_block_dirty_bitmap_remove(
+        const char *node, const char *name, bool release,
+        BlockDriverState **bitmap_bs, Error **errp);
+
+static void block_dirty_bitmap_remove_prepare(BlkActionState *common,
+                                              Error **errp)
+{
+    BlockDirtyBitmap *action;
+    BlockDirtyBitmapState *state = DO_UPCAST(BlockDirtyBitmapState,
+                                             common, common);
+
+    if (action_check_completion_mode(common, errp) < 0) {
+        return;
+    }
+
+    action = common->action->u.block_dirty_bitmap_remove.data;
+
+    state->bitmap = do_block_dirty_bitmap_remove(action->node, action->name,
+                                                 false, &state->bs, errp);
+    if (state->bitmap) {
+        bdrv_dirty_bitmap_squelch_persistence(state->bitmap, true);
+        bdrv_dirty_bitmap_set_busy(state->bitmap, true);
+    }
+}
+
+static void block_dirty_bitmap_remove_abort(BlkActionState *common)
+{
+    BlockDirtyBitmapState *state = DO_UPCAST(BlockDirtyBitmapState,
+                                             common, common);
+
+    if (state->bitmap) {
+        bdrv_dirty_bitmap_squelch_persistence(state->bitmap, false);
+        bdrv_dirty_bitmap_set_busy(state->bitmap, false);
+    }
+}
+
+static void block_dirty_bitmap_remove_commit(BlkActionState *common)
+{
+    BlockDirtyBitmapState *state = DO_UPCAST(BlockDirtyBitmapState,
+                                             common, common);
+
+    bdrv_dirty_bitmap_set_busy(state->bitmap, false);
+    bdrv_release_dirty_bitmap(state->bs, state->bitmap);
+}
+
 static void abort_prepare(BlkActionState *common, Error **errp)
 {
     error_setg(errp, "Transaction aborted using Abort action");
@@ -2211,6 +2256,12 @@ static const BlkActionOps actions[] = {
         .commit = block_dirty_bitmap_free_backup,
         .abort = block_dirty_bitmap_restore,
     },
+    [TRANSACTION_ACTION_KIND_BLOCK_DIRTY_BITMAP_REMOVE] = {
+        .instance_size = sizeof(BlockDirtyBitmapState),
+        .prepare = block_dirty_bitmap_remove_prepare,
+        .commit = block_dirty_bitmap_remove_commit,
+        .abort = block_dirty_bitmap_remove_abort,
+    },
     /* Where are transactions for MIRROR, COMMIT and STREAM?
      * Although these blockjobs use transaction callbacks like the backup job,
      * these jobs do not necessarily adhere to transaction semantics.
@@ -2869,20 +2920,21 @@ void qmp_block_dirty_bitmap_add(const char *node, const char *name,
     bdrv_dirty_bitmap_set_persistence(bitmap, persistent);
 }
 
-void qmp_block_dirty_bitmap_remove(const char *node, const char *name,
-                                   Error **errp)
+static BdrvDirtyBitmap *do_block_dirty_bitmap_remove(
+        const char *node, const char *name, bool release,
+        BlockDriverState **bitmap_bs, Error **errp)
 {
     BlockDriverState *bs;
     BdrvDirtyBitmap *bitmap;
 
     bitmap = block_dirty_bitmap_lookup(node, name, &bs, errp);
     if (!bitmap || !bs) {
-        return;
+        return NULL;
     }
 
     if (bdrv_dirty_bitmap_check(bitmap, BDRV_BITMAP_BUSY | BDRV_BITMAP_RO,
                                 errp)) {
-        return;
+        return NULL;
     }
 
     if (bdrv_dirty_bitmap_get_persistence(bitmap)) {
@@ -2892,13 +2944,28 @@ void qmp_block_dirty_bitmap_remove(const char *node, const char *name,
         aio_context_acquire(aio_context);
         bdrv_remove_persistent_dirty_bitmap(bs, name, &local_err);
         aio_context_release(aio_context);
+
         if (local_err != NULL) {
             error_propagate(errp, local_err);
-            return;
+            return NULL;
         }
     }
 
-    bdrv_release_dirty_bitmap(bs, bitmap);
+    if (release) {
+        bdrv_release_dirty_bitmap(bs, bitmap);
+    }
+
+    if (bitmap_bs) {
+        *bitmap_bs = bs;
+    }
+
+    return bitmap;
+}
+
+void qmp_block_dirty_bitmap_remove(const char *node, const char *name,
+                                   Error **errp)
+{
+    do_block_dirty_bitmap_remove(node, name, true, NULL, errp);
 }
 
 /**
diff --git a/migration/block-dirty-bitmap.c b/migration/block-dirty-bitmap.c
index 4a896a09eb..c742b706a9 100644
--- a/migration/block-dirty-bitmap.c
+++ b/migration/block-dirty-bitmap.c
@@ -326,7 +326,7 @@ static int init_dirty_bitmap_migration(void)
 
     /* unset migration flags here, to not roll back it */
     QSIMPLEQ_FOREACH(dbms, &dirty_bitmap_mig_state.dbms_list, entry) {
-        bdrv_dirty_bitmap_set_migration(dbms->bitmap, true);
+        bdrv_dirty_bitmap_squelch_persistence(dbms->bitmap, true);
     }
 
     if (QSIMPLEQ_EMPTY(&dirty_bitmap_mig_state.dbms_list)) {
-- 
2.21.0