[v2,04/19] block/copy-before-write: add bitmap open parameter

Commit Message

Vladimir Sementsov-Ogievskiy Aug. 27, 2021, 6:17 p.m. UTC

This brings "incremental" mode to copy-before-write filter: user can
specify bitmap so that filter will copy only "dirty" areas.

Signed-off-by: Vladimir Sementsov-Ogievskiy <[e-mail]>
---
 qapi/block-core.json      | 10 +++++++++-
 block/copy-before-write.c | 30 +++++++++++++++++++++++++++++-
 2 files changed, 38 insertions(+), 2 deletions(-)

Patch

diff --git a/qapi/block-core.json b/qapi/block-core.json
index 6764d8b84f..c42d23752d 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -4063,11 +4063,19 @@ 
 #
 # @target: The target for copy-before-write operations.
 #
+# @bitmap: If specified, copy-before-write filter will do
+#          copy-before-write operations only for dirty regions of the
+#          bitmap. Bitmap size must be equal to length of file and
+#          target child of the filter. Note also, that bitmap is used
+#          only to initialize internal bitmap of the process, so further
+#          modifications (or removing) of specified bitmap doesn't
+#          influence the filter.
+#
 # Since: 6.2
 ##
 { 'struct': 'BlockdevOptionsCbw',
   'base': 'BlockdevOptionsGenericFormat',
-  'data': { 'target': 'BlockdevRef' } }
+  'data': { 'target': 'BlockdevRef', '*bitmap': 'BlockDirtyBitmap' } }
 
 ##
 # @BlockdevOptions:
diff --git a/block/copy-before-write.c b/block/copy-before-write.c
index d31ca61111..e3456ad6aa 100644
--- a/block/copy-before-write.c
+++ b/block/copy-before-write.c
@@ -148,6 +148,7 @@  static int cbw_open(BlockDriverState *bs, QDict *options, int flags,
                     Error **errp)
 {
     BDRVCopyBeforeWriteState *s = bs->opaque;
+    BdrvDirtyBitmap *bitmap = NULL;
 
     bs->file = bdrv_open_child(NULL, options, "file", bs, &child_of_bds,
                                BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY,
@@ -162,6 +163,33 @@  static int cbw_open(BlockDriverState *bs, QDict *options, int flags,
         return -EINVAL;
     }
 
+    if (qdict_haskey(options, "bitmap.node") ||
+        qdict_haskey(options, "bitmap.name"))
+    {
+        const char *bitmap_node, *bitmap_name;
+
+        if (!qdict_haskey(options, "bitmap.node")) {
+            error_setg(errp, "bitmap.node is not specified");
+            return -EINVAL;
+        }
+
+        if (!qdict_haskey(options, "bitmap.name")) {
+            error_setg(errp, "bitmap.name is not specified");
+            return -EINVAL;
+        }
+
+        bitmap_node = qdict_get_str(options, "bitmap.node");
+        bitmap_name = qdict_get_str(options, "bitmap.name");
+        qdict_del(options, "bitmap.node");
+        qdict_del(options, "bitmap.name");
+
+        bitmap = block_dirty_bitmap_lookup(bitmap_node, bitmap_name, NULL,
+                                           errp);
+        if (!bitmap) {
+            return -EINVAL;
+        }
+    }
+
     bs->total_sectors = bs->file->bs->total_sectors;
     bs->supported_write_flags = BDRV_REQ_WRITE_UNCHANGED |
             (BDRV_REQ_FUA & bs->file->bs->supported_write_flags);
@@ -169,7 +197,7 @@  static int cbw_open(BlockDriverState *bs, QDict *options, int flags,
             ((BDRV_REQ_FUA | BDRV_REQ_MAY_UNMAP | BDRV_REQ_NO_FALLBACK) &
              bs->file->bs->supported_zero_flags);
 
-    s->bcs = block_copy_state_new(bs->file, s->target, NULL, errp);
+    s->bcs = block_copy_state_new(bs->file, s->target, bitmap, errp);
     if (!s->bcs) {
         error_prepend(errp, "Cannot create block-copy-state: ");
         return -EINVAL;