qapi: add x-debug-query-block-graph

Add a new command, returning block nodes (and their users) graph.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-id: 20181221170909.25584-2-vsementsov@virtuozzo.com
Signed-off-by: Max Reitz <mreitz@redhat.com>

block.c

@@ -4119,6 +4119,154 @@ BlockDeviceInfoList *bdrv_named_nodes_list(Error **errp)
     return list;
 }
 
+#define QAPI_LIST_ADD(list, element) do { \
+    typeof(list) _tmp = g_new(typeof(*(list)), 1); \
+    _tmp->value = (element); \
+    _tmp->next = (list); \
+    (list) = _tmp; \
+} while (0)
+
+typedef struct XDbgBlockGraphConstructor {
+    XDbgBlockGraph *graph;
+    GHashTable *graph_nodes;
+} XDbgBlockGraphConstructor;
+
+static XDbgBlockGraphConstructor *xdbg_graph_new(void)
+{
+    XDbgBlockGraphConstructor *gr = g_new(XDbgBlockGraphConstructor, 1);
+
+    gr->graph = g_new0(XDbgBlockGraph, 1);
+    gr->graph_nodes = g_hash_table_new(NULL, NULL);
+
+    return gr;
+}
+
+static XDbgBlockGraph *xdbg_graph_finalize(XDbgBlockGraphConstructor *gr)
+{
+    XDbgBlockGraph *graph = gr->graph;
+
+    g_hash_table_destroy(gr->graph_nodes);
+    g_free(gr);
+
+    return graph;
+}
+
+static uintptr_t xdbg_graph_node_num(XDbgBlockGraphConstructor *gr, void *node)
+{
+    uintptr_t ret = (uintptr_t)g_hash_table_lookup(gr->graph_nodes, node);
+
+    if (ret != 0) {
+        return ret;
+    }
+
+    /*
+     * Start counting from 1, not 0, because 0 interferes with not-found (NULL)
+     * answer of g_hash_table_lookup.
+     */
+    ret = g_hash_table_size(gr->graph_nodes) + 1;
+    g_hash_table_insert(gr->graph_nodes, node, (void *)ret);
+
+    return ret;
+}
+
+static void xdbg_graph_add_node(XDbgBlockGraphConstructor *gr, void *node,
+                                XDbgBlockGraphNodeType type, const char *name)
+{
+    XDbgBlockGraphNode *n;
+
+    n = g_new0(XDbgBlockGraphNode, 1);
+
+    n->id = xdbg_graph_node_num(gr, node);
+    n->type = type;
+    n->name = g_strdup(name);
+
+    QAPI_LIST_ADD(gr->graph->nodes, n);
+}
+
+static void xdbg_graph_add_edge(XDbgBlockGraphConstructor *gr, void *parent,
+                                const BdrvChild *child)
+{
+    typedef struct {
+        unsigned int flag;
+        BlockPermission num;
+    } PermissionMap;
+
+    static const PermissionMap permissions[] = {
+        { BLK_PERM_CONSISTENT_READ, BLOCK_PERMISSION_CONSISTENT_READ },
+        { BLK_PERM_WRITE,           BLOCK_PERMISSION_WRITE },
+        { BLK_PERM_WRITE_UNCHANGED, BLOCK_PERMISSION_WRITE_UNCHANGED },
+        { BLK_PERM_RESIZE,          BLOCK_PERMISSION_RESIZE },
+        { BLK_PERM_GRAPH_MOD,       BLOCK_PERMISSION_GRAPH_MOD },
+        { 0, 0 }
+    };
+    const PermissionMap *p;
+    XDbgBlockGraphEdge *edge;
+
+    QEMU_BUILD_BUG_ON(1UL << (ARRAY_SIZE(permissions) - 1) != BLK_PERM_ALL + 1);
+
+    edge = g_new0(XDbgBlockGraphEdge, 1);
+
+    edge->parent = xdbg_graph_node_num(gr, parent);
+    edge->child = xdbg_graph_node_num(gr, child->bs);
+    edge->name = g_strdup(child->name);
+
+    for (p = permissions; p->flag; p++) {
+        if (p->flag & child->perm) {
+            QAPI_LIST_ADD(edge->perm, p->num);
+        }
+        if (p->flag & child->shared_perm) {
+            QAPI_LIST_ADD(edge->shared_perm, p->num);
+        }
+    }
+
+    QAPI_LIST_ADD(gr->graph->edges, edge);
+}
+
+
+XDbgBlockGraph *bdrv_get_xdbg_block_graph(Error **errp)
+{
+    BlockBackend *blk;
+    BlockJob *job;
+    BlockDriverState *bs;
+    BdrvChild *child;
+    XDbgBlockGraphConstructor *gr = xdbg_graph_new();
+
+    for (blk = blk_all_next(NULL); blk; blk = blk_all_next(blk)) {
+        char *allocated_name = NULL;
+        const char *name = blk_name(blk);
+
+        if (!*name) {
+            name = allocated_name = blk_get_attached_dev_id(blk);
+        }
+        xdbg_graph_add_node(gr, blk, X_DBG_BLOCK_GRAPH_NODE_TYPE_BLOCK_BACKEND,
+                           name);
+        g_free(allocated_name);
+        if (blk_root(blk)) {
+            xdbg_graph_add_edge(gr, blk, blk_root(blk));
+        }
+    }
+
+    for (job = block_job_next(NULL); job; job = block_job_next(job)) {
+        GSList *el;
+
+        xdbg_graph_add_node(gr, job, X_DBG_BLOCK_GRAPH_NODE_TYPE_BLOCK_JOB,
+                           job->job.id);
+        for (el = job->nodes; el; el = el->next) {
+            xdbg_graph_add_edge(gr, job, (BdrvChild *)el->data);
+        }
+    }
+
+    QTAILQ_FOREACH(bs, &graph_bdrv_states, node_list) {
+        xdbg_graph_add_node(gr, bs, X_DBG_BLOCK_GRAPH_NODE_TYPE_BLOCK_DRIVER,
+                           bs->node_name);
+        QLIST_FOREACH(child, &bs->children, next) {
+            xdbg_graph_add_edge(gr, bs, child);
+        }
+    }
+
+    return xdbg_graph_finalize(gr);
+}
+
 BlockDriverState *bdrv_lookup_bs(const char *device,
                                  const char *node_name,
                                  Error **errp)

block/block-backend.c

@@ -2249,3 +2249,8 @@ int coroutine_fn blk_co_copy_range(BlockBackend *blk_in, int64_t off_in,
                               blk_out->root, off_out,
                               bytes, read_flags, write_flags);
 }
+
+const BdrvChild *blk_root(BlockBackend *blk)
+{
+    return blk->root;
+}

blockdev.c

@@ -3582,6 +3582,11 @@ BlockDeviceInfoList *qmp_query_named_block_nodes(Error **errp)
     return bdrv_named_nodes_list(errp);
 }
 
+XDbgBlockGraph *qmp_x_debug_query_block_graph(Error **errp)
+{
+    return bdrv_get_xdbg_block_graph(errp);
+}
+
 BlockJob *do_blockdev_backup(BlockdevBackup *backup, JobTxn *txn,
                              Error **errp)
 {

include/block/block.h

@@ -448,6 +448,7 @@ void bdrv_eject(BlockDriverState *bs, bool eject_flag);
 const char *bdrv_get_format_name(BlockDriverState *bs);
 BlockDriverState *bdrv_find_node(const char *node_name);
 BlockDeviceInfoList *bdrv_named_nodes_list(Error **errp);
+XDbgBlockGraph *bdrv_get_xdbg_block_graph(Error **errp);
 BlockDriverState *bdrv_lookup_bs(const char *device,
                                  const char *node_name,
                                  Error **errp);

include/sysemu/block-backend.h

@@ -237,4 +237,6 @@ int coroutine_fn blk_co_copy_range(BlockBackend *blk_in, int64_t off_in,
                                    int bytes, BdrvRequestFlags read_flags,
                                    BdrvRequestFlags write_flags);
 
+const BdrvChild *blk_root(BlockBackend *blk);
+
 #endif

qapi/block-core.json

@@ -1665,6 +1665,114 @@
 ##
 { 'command': 'query-named-block-nodes', 'returns': [ 'BlockDeviceInfo' ] }
 
+##
+# @XDbgBlockGraphNodeType:
+#
+# @block-backend: corresponds to BlockBackend
+#
+# @block-job: corresonds to BlockJob
+#
+# @block-driver: corresponds to BlockDriverState
+#
+# Since: 4.0
+##
+{ 'enum': 'XDbgBlockGraphNodeType',
+  'data': [ 'block-backend', 'block-job', 'block-driver' ] }
+
+##
+# @XDbgBlockGraphNode:
+#
+# @id: Block graph node identifier. This @id is generated only for
+#      x-debug-query-block-graph and does not relate to any other identifiers in
+#      Qemu.
+#
+# @type: Type of graph node. Can be one of block-backend, block-job or
+#        block-driver-state.
+#
+# @name: Human readable name of the node. Corresponds to node-name for
+#        block-driver-state nodes; is not guaranteed to be unique in the whole
+#        graph (with block-jobs and block-backends).
+#
+# Since: 4.0
+##
+{ 'struct': 'XDbgBlockGraphNode',
+  'data': { 'id': 'uint64', 'type': 'XDbgBlockGraphNodeType', 'name': 'str' } }
+
+##
+# @BlockPermission:
+#
+# Enum of base block permissions.
+#
+# @consistent-read: A user that has the "permission" of consistent reads is
+#                   guaranteed that their view of the contents of the block
+#                   device is complete and self-consistent, representing the
+#                   contents of a disk at a specific point.
+#                   For most block devices (including their backing files) this
+#                   is true, but the property cannot be maintained in a few
+#                   situations like for intermediate nodes of a commit block
+#                   job.
+#
+# @write: This permission is required to change the visible disk contents.
+#
+# @write-unchanged: This permission (which is weaker than BLK_PERM_WRITE) is
+#                   both enough and required for writes to the block node when
+#                   the caller promises that the visible disk content doesn't
+#                   change.
+#                   As the BLK_PERM_WRITE permission is strictly stronger,
+#                   either is sufficient to perform an unchanging write.
+#
+# @resize: This permission is required to change the size of a block node.
+#
+# @graph-mod: This permission is required to change the node that this
+#             BdrvChild points to.
+#
+# Since: 4.0
+##
+  { 'enum': 'BlockPermission',
+    'data': [ 'consistent-read', 'write', 'write-unchanged', 'resize',
+              'graph-mod' ] }
+##
+# @XDbgBlockGraphEdge:
+#
+# Block Graph edge description for x-debug-query-block-graph.
+#
+# @parent: parent id
+#
+# @child: child id
+#
+# @name: name of the relation (examples are 'file' and 'backing')
+#
+# @perm: granted permissions for the parent operating on the child
+#
+# @shared-perm: permissions that can still be granted to other users of the
+#               child while it is still attached to this parent
+#
+# Since: 4.0
+##
+{ 'struct': 'XDbgBlockGraphEdge',
+  'data': { 'parent': 'uint64', 'child': 'uint64',
+            'name': 'str', 'perm': [ 'BlockPermission' ],
+            'shared-perm': [ 'BlockPermission' ] } }
+
+##
+# @XDbgBlockGraph:
+#
+# Block Graph - list of nodes and list of edges.
+#
+# Since: 4.0
+##
+{ 'struct': 'XDbgBlockGraph',
+  'data': { 'nodes': ['XDbgBlockGraphNode'], 'edges': ['XDbgBlockGraphEdge'] } }
+
+##
+# @x-debug-query-block-graph:
+#
+# Get the block graph.
+#
+# Since: 4.0
+##
+{ 'command': 'x-debug-query-block-graph', 'returns': 'XDbgBlockGraph' }
+
 ##
 # @drive-mirror:
 #