[Qemu-block] [PATCH v2 1/8] block: Add blk_name_taken()

[Max Reitz]

There may be BlockBackends which are not returned by blk_by_name(), but
do exist and have a name. blk_name_taken() allows testing whether a
specific name is in use already, independent of whether the BlockBackend
with that name is accessible through blk_by_name().

Signed-off-by: Max Reitz <address@hidden>
Reviewed-by: Eric Blake <address@hidden>
---
 block.c                        |  4 ++--
 block/block-backend.c          | 19 ++++++++++++++++++-
 include/sysemu/block-backend.h |  1 +
 3 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/block.c b/block.c
index e3d5aea..faad9fb 100644
--- a/block.c
+++ b/block.c
@@ -777,8 +777,8 @@ static void bdrv_assign_node_name(BlockDriverState *bs,
         return;
     }
 
-    /* takes care of avoiding namespaces collisions */
-    if (blk_by_name(node_name)) {
+    /* takes care of avoiding namespace collisions */
+    if (blk_name_taken(node_name)) {
         error_setg(errp, "node-name=%s is conflicting with a device id",
                    node_name);
         goto out;
diff --git a/block/block-backend.c b/block/block-backend.c
index 7373093..7128adc 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -86,7 +86,7 @@ BlockBackend *blk_new(const char *name, Error **errp)
         error_setg(errp, "Invalid device name");
         return NULL;
     }
-    if (blk_by_name(name)) {
+    if (blk_name_taken(name)) {
         error_setg(errp, "Device with id '%s' already exists", name);
         return NULL;
     }
@@ -279,6 +279,23 @@ BlockBackend *blk_by_name(const char *name)
 }
 
 /*
+ * This function should be used to check whether a certain BlockBackend name is
+ * already taken; blk_by_name() will only search in the list of monitor-owned
+ * BlockBackends which is not necessarily complete.
+ */
+bool blk_name_taken(const char *name)
+{
+    BlockBackend *blk;
+
+    QTAILQ_FOREACH(blk, &blk_backends, link) {
+        if (!strcmp(name, blk->name)) {
+            return true;
+        }
+    }
+    return false;
+}
+
+/*
  * Return the BlockDriverState attached to @blk if any, else null.
  */
 BlockDriverState *blk_bs(BlockBackend *blk)
diff --git a/include/sysemu/block-backend.h b/include/sysemu/block-backend.h
index 9fb3e54..0593231 100644
--- a/include/sysemu/block-backend.h
+++ b/include/sysemu/block-backend.h
@@ -71,6 +71,7 @@ void blk_unref(BlockBackend *blk);
 void blk_remove_all_bs(void);
 const char *blk_name(BlockBackend *blk);
 BlockBackend *blk_by_name(const char *name);
+bool blk_name_taken(const char *name);
 BlockBackend *blk_next(BlockBackend *blk);
 
 BlockDriverState *blk_bs(BlockBackend *blk);
-- 
2.6.2