block: Add blk_by_dev()

This finds a BlockBackend given the device model that is attached to it.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>

2 files changed, 20 insertions, 0 deletions

diff --git a/block/block-backend.c b/block/block-backend.c
index d1349d90e5..0bd19abdfb 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -560,6 +560,25 @@ void *blk_get_attached_dev(BlockBackend *blk)
 }
 
 /*
+ * Return the BlockBackend which has the device model @dev attached if it
+ * exists, else null.
+ *
+ * @dev must not be null.
+ */
+BlockBackend *blk_by_dev(void *dev)
+{
+    BlockBackend *blk = NULL;
+
+    assert(dev != NULL);
+    while ((blk = blk_all_next(blk)) != NULL) {
+        if (blk->dev == dev) {
+            return blk;
+        }
+    }
+    return NULL;
+}
+
+/*
  * Set @blk's device model callbacks to @ops.
  * @opaque is the opaque argument to pass to the callbacks.
  * This is for use by device models.
diff --git a/include/sysemu/block-backend.h b/include/sysemu/block-backend.h
index 4808a9621a..410eb68145 100644
--- a/include/sysemu/block-backend.h
+++ b/include/sysemu/block-backend.h
@@ -111,6 +111,7 @@ int blk_attach_dev(BlockBackend *blk, void *dev);
 void blk_attach_dev_nofail(BlockBackend *blk, void *dev);
 void blk_detach_dev(BlockBackend *blk, void *dev);
 void *blk_get_attached_dev(BlockBackend *blk);
+BlockBackend *blk_by_dev(void *dev);
 void blk_set_dev_ops(BlockBackend *blk, const BlockDevOps *ops, void *opaque);
 int blk_pread_unthrottled(BlockBackend *blk, int64_t offset, uint8_t *buf,
                           int count);