[1/2] block: add functions to search BlockBackend by root BDS name

Commit Message

Anton Kuchin Jan. 28, 2019, 2:27 p.m. UTC

BlockBackend name is empty if it is added with '-blockdev' and '-device'
options or hotplugged with QMP but callers still expect backend to be
accesible by name for operations like commit or statistics access.
Intoduce blk_lookup function to search both by name and BDS-root node_name.

Signed-off-by: Anton Kuchin <[e-mail]>
---
 block/block-backend.c          | 29 +++++++++++++++++++++++++++++
 include/sysemu/block-backend.h |  7 +++++++
 2 files changed, 36 insertions(+)

Patch

diff --git a/block/block-backend.c b/block/block-backend.c
index 60d37a0c3d..86a492853c 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -684,6 +684,35 @@  static BlockBackend *bdrv_first_blk(BlockDriverState *bs)
     return NULL;
 }
 
+/*
+ * Return the BlockBackend that has attached BDS-tree root with
+ * node_name @node_name if it exists, else null.
+ * @node_name must not be null.
+ */
+static BlockBackend *blk_by_root_name(const char *node_name)
+{
+    BlockBackend *blk = NULL;
+
+    assert(node_name);
+    while ((blk = blk_all_next(blk)) != NULL) {
+        BlockDriverState *bs = blk_bs(blk);
+        if (bs && !strcmp(node_name, bs->node_name)) {
+            return blk;
+        }
+    }
+    return NULL;
+}
+
+BlockBackend *blk_lookup(const char *name)
+{
+    assert(name);
+    BlockBackend *blk = blk_by_name(name);
+    if (!blk) {
+        blk = blk_by_root_name(name);
+    }
+    return blk;
+}
+
 /*
  * Returns true if @bs has an associated BlockBackend.
  */
diff --git a/include/sysemu/block-backend.h b/include/sysemu/block-backend.h
index c96bcdee14..290b8f8fc9 100644
--- a/include/sysemu/block-backend.h
+++ b/include/sysemu/block-backend.h
@@ -85,6 +85,13 @@  void blk_unref(BlockBackend *blk);
 void blk_remove_all_bs(void);
 const char *blk_name(const BlockBackend *blk);
 BlockBackend *blk_by_name(const char *name);
+
+/*
+ * Search BlockBackend by name or root BlockDriverSate node_name.
+ * Hotplug BlockBackends have no name so need to also check BDS-tree roots
+ * @name must not be null.
+ */
+BlockBackend *blk_lookup(const char *name);
 BlockBackend *blk_next(BlockBackend *blk);
 BlockBackend *blk_all_next(BlockBackend *blk);
 bool monitor_add_blk(BlockBackend *blk, const char *name, Error **errp);