[PATCH v12 02/14] block: add insert/remove node functions

From: Andrey Shinkevich via <qemu-devel@nongnu.org>
To: qemu-block@nongnu.org
Cc: qemu-devel@nongnu.org, fam@euphon.net, stefanha@redhat.com,
	kwolf@redhat.com, mreitz@redhat.com, armbru@redhat.com,
	jsnow@redhat.com, eblake@redhat.com, den@openvz.org,
	vsementsov@virtuozzo.com, andrey.shinkevich@virtuozzo.com
Subject: [PATCH v12 02/14] block: add insert/remove node functions
Date: Thu, 22 Oct 2020 21:13:31 +0300	[thread overview]
Message-ID: <1603390423-980205-3-git-send-email-andrey.shinkevich@virtuozzo.com> (raw)
In-Reply-To: <1603390423-980205-1-git-send-email-andrey.shinkevich@virtuozzo.com>

Provide API for a node insertion to and removal from a backing chain.

Suggested-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
---
 block.c               | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
 include/block/block.h |  3 +++
 2 files changed, 52 insertions(+)

diff --git a/block.c b/block.c
index 430edf7..502b483 100644
--- a/block.c
+++ b/block.c
@@ -4670,6 +4670,55 @@ static void bdrv_delete(BlockDriverState *bs)
     g_free(bs);
 }
 
+BlockDriverState *bdrv_insert_node(BlockDriverState *bs, QDict *node_options,
+                                   int flags, Error **errp)
+{
+    BlockDriverState *new_node_bs;
+    Error *local_err = NULL;
+
+    new_node_bs =  bdrv_open(NULL, NULL, node_options, flags, errp);
+    if (new_node_bs == NULL) {
+        error_prepend(errp, "Could not create node: ");
+        return NULL;
+    }
+
+    bdrv_drained_begin(bs);
+    bdrv_replace_node(bs, new_node_bs, &local_err);
+    bdrv_drained_end(bs);
+
+    if (local_err) {
+        bdrv_unref(new_node_bs);
+        error_propagate(errp, local_err);
+        return NULL;
+    }
+
+    return new_node_bs;
+}
+
+void bdrv_remove_node(BlockDriverState *bs)
+{
+    BdrvChild *child;
+    BlockDriverState *inferior_bs;
+
+    child = bdrv_filter_or_cow_child(bs);
+    if (!child) {
+        return;
+    }
+    inferior_bs = child->bs;
+
+    /* Retain the BDS until we complete the graph change. */
+    bdrv_ref(inferior_bs);
+    /* Hold a guest back from writing while permissions are being reset. */
+    bdrv_drained_begin(inferior_bs);
+    /* Refresh permissions before the graph change. */
+    bdrv_child_refresh_perms(bs, child, &error_abort);
+    bdrv_replace_node(bs, inferior_bs, &error_abort);
+
+    bdrv_drained_end(inferior_bs);
+    bdrv_unref(inferior_bs);
+    bdrv_unref(bs);
+}
+
 /*
  * Run consistency checks on an image
  *
diff --git a/include/block/block.h b/include/block/block.h
index d16c401..ae7612f 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -350,6 +350,9 @@ void bdrv_append(BlockDriverState *bs_new, BlockDriverState *bs_top,
                  Error **errp);
 void bdrv_replace_node(BlockDriverState *from, BlockDriverState *to,
                        Error **errp);
+BlockDriverState *bdrv_insert_node(BlockDriverState *bs, QDict *node_options,
+                                   int flags, Error **errp);
+void bdrv_remove_node(BlockDriverState *bs);
 
 int bdrv_parse_aio(const char *mode, int *flags);
 int bdrv_parse_cache_mode(const char *mode, int *flags, bool *writethrough);
-- 
1.8.3.1


