Commit 107cfb72 authored May 22, 2020 by Vladimir Sementsov-Ogievskiy Committed by Eric Blake May 28, 2020

migration: fix bitmaps pre-blockdev migration with mirror job

Important thing for bitmap migration is to select destination block
node to obtain the migrated bitmap.

Prepatch, on source we use bdrv_get_device_or_node_name() to identify
the node, and on target we do bdrv_lookup_bs.
bdrv_get_device_or_node_name() returns blk name only for direct
children of blk. So, bitmaps of direct children of blks are migrated by
blk name and others - by node name.

Old libvirt is unprepared to bitmap migration by node-name,
node-names are mostly auto-generated. So actually only migration by blk
name works for it.

Newer libvirt will use new interface (which will be added soon) to
specify node-mapping for bitmaps migration explicitly. Still, let's
improve the current behavior a bit.

Now, consider classic libvirt migrations assisted by mirror block job:
mirror block job inserts filter, so our source is not a direct child of
blk, and bitmaps are migrated by node-names. And this just doesn't work
with auto-generated node names.

Let's fix it by using blk-name even if some implicit filters are
inserted.

Note2: we, of course, can't skip filters and use blk name to migrate
bitmaps in filtered node by blk name for this blk if these filters have
named bitmaps which should be migrated.

Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1652424


Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20200521220648.3255-4-vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[eblake: comment typo fix, shorter subject line]
Signed-off-by: Eric Blake <eblake@redhat.com>

parent 7ae89a0d

migration/block-dirty-bitmap.c

+44 −1

Original line number	Diff line number	Diff line
		@@ -319,14 +319,54 @@ static int init_dirty_bitmap_migration(void)
		{
		BlockDriverState *bs;
		DirtyBitmapMigBitmapState *dbms;
		GHashTable *handled_by_blk = g_hash_table_new(NULL, NULL);
		BlockBackend *blk;

		dirty_bitmap_mig_state.bulk_completed = false;
		dirty_bitmap_mig_state.prev_bs = NULL;
		dirty_bitmap_mig_state.prev_bitmap = NULL;
		dirty_bitmap_mig_state.no_bitmaps = false;

		/*
		* Use blockdevice name for direct (or filtered) children of named block
		* backends.
		*/
		for (blk = blk_next(NULL); blk; blk = blk_next(blk)) {
		const char *name = blk_name(blk);

		if (!name \|\| strcmp(name, "") == 0) {
		continue;
		}

		bs = blk_bs(blk);

		/* Skip filters without bitmaps */
		while (bs && bs->drv && bs->drv->is_filter &&
		!bdrv_has_named_bitmaps(bs))
		{
		if (bs->backing) {
		bs = bs->backing->bs;
		} else if (bs->file) {
		bs = bs->file->bs;
		} else {
		bs = NULL;
		}
		}

		if (bs && bs->drv && !bs->drv->is_filter) {
		if (add_bitmaps_to_list(bs, name)) {
		goto fail;
		}
		g_hash_table_add(handled_by_blk, bs);
		}
		}

		for (bs = bdrv_next_all_states(NULL); bs; bs = bdrv_next_all_states(bs)) {
		if (add_bitmaps_to_list(bs, bdrv_get_device_or_node_name(bs))) {
		if (g_hash_table_contains(handled_by_blk, bs)) {
		continue;
		}

		if (add_bitmaps_to_list(bs, bdrv_get_node_name(bs))) {
		goto fail;
		}
		}
		@@ -340,9 +380,12 @@ static int init_dirty_bitmap_migration(void)
		dirty_bitmap_mig_state.no_bitmaps = true;
		}

		g_hash_table_destroy(handled_by_blk);

		return 0;

		fail:
		g_hash_table_destroy(handled_by_blk);
		dirty_bitmap_mig_cleanup();

		return -1;