rbd: get the object prefix for a v2 rbd image

The object prefix of an rbd format 2 image is fetched from the
server using a "get_object_prefix" method.

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index 061c624..64a4dd5 100644 (file)
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -66,7 +66,8 @@
 
 #define RBD_SNAP_HEAD_NAME     "-"
 
-#define        RBD_IMAGE_ID_LEN_MAX    64
+#define RBD_IMAGE_ID_LEN_MAX   64
+#define RBD_OBJ_PREFIX_LEN_MAX 64
 
 /*
  * An RBD device name will be "rbd#", where the "rbd" comes from
@@ -2168,6 +2169,43 @@ static int rbd_dev_v2_image_size(struct rbd_device *rbd_dev)
                                        &rbd_dev->header.image_size);
 }
 
+static int rbd_dev_v2_object_prefix(struct rbd_device *rbd_dev)
+{
+       void *reply_buf;
+       int ret;
+       void *p;
+
+       reply_buf = kzalloc(RBD_OBJ_PREFIX_LEN_MAX, GFP_KERNEL);
+       if (!reply_buf)
+               return -ENOMEM;
+
+       ret = rbd_req_sync_exec(rbd_dev, rbd_dev->header_name,
+                               "rbd", "get_object_prefix",
+                               NULL, 0,
+                               reply_buf, RBD_OBJ_PREFIX_LEN_MAX,
+                               CEPH_OSD_FLAG_READ, NULL);
+       dout("%s: rbd_req_sync_exec returned %d\n", __func__, ret);
+       if (ret < 0)
+               goto out;
+
+       p = reply_buf;
+       rbd_dev->header.object_prefix = ceph_extract_encoded_string(&p,
+                                               p + RBD_OBJ_PREFIX_LEN_MAX,
+                                               NULL, GFP_NOIO);
+
+       if (IS_ERR(rbd_dev->header.object_prefix)) {
+               ret = PTR_ERR(rbd_dev->header.object_prefix);
+               rbd_dev->header.object_prefix = NULL;
+       } else {
+               dout("  object_prefix = %s\n", rbd_dev->header.object_prefix);
+       }
+
+out:
+       kfree(reply_buf);
+
+       return ret;
+}
+
 /*
  * Scan the rbd device's current snapshot list and compare it to the
  * newly-received snapshot context.  Remove any existing snapshots
@@ -2695,6 +2733,12 @@ static int rbd_dev_v2_probe(struct rbd_device *rbd_dev)
        ret = rbd_dev_v2_image_size(rbd_dev);
        if (ret < 0)
                goto out_err;
+
+       /* Get the object prefix (a.k.a. block_name) for the image */
+
+       ret = rbd_dev_v2_object_prefix(rbd_dev);
+       if (ret < 0)
+               goto out_err;
        rbd_dev->image_format = 2;
 
        dout("discovered version 2 image, header name is %s\n",
@@ -2704,6 +2748,8 @@ static int rbd_dev_v2_probe(struct rbd_device *rbd_dev)
 out_err:
        kfree(rbd_dev->header_name);
        rbd_dev->header_name = NULL;
+       kfree(rbd_dev->header.object_prefix);
+       rbd_dev->header.object_prefix = NULL;
 
        return ret;
 }