[PATCH 3/9] rbd: get the object prefix for a v2 rbd image

[Alex Elder <elder@xxxxxxxxxxx>]

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@xxxxxxxxxxx>
---
 drivers/block/rbd.c |   47 ++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 46 insertions(+), 1 deletion(-)

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index 24d12e3..36e848a 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
@@ -2163,6 +2164,42 @@ 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
@@ -2690,6 +2727,12 @@ 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",
@@ -2699,6 +2742,8 @@ 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;
 }
-- 
1.7.9.5

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