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>

1 files changed, 47 insertions, 1 deletions

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index 061c62496fea..64a4dd5f6f2b 100644
--- 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;
 }