rbd: dynamically allocate snapshot name

There is no need to impose a small limit the length of the snapshot
name recorded for an rbd image in a struct rbd_dev.  Remove the
limitation by allocating space for the snapshot name dynamically.

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 7d4735c..5c0f044 100644 (file)
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -172,7 +172,7 @@ struct rbd_device {
 
        /* protects updating the header */
        struct rw_semaphore     header_rwsem;
-       char                    snap_name[RBD_MAX_SNAP_NAME_LEN];
+       char                    *snap_name;
        u64                     snap_id;        /* current snapshot id */
        int read_only;
 
@@ -588,8 +588,6 @@ static int rbd_header_set_snap(struct rbd_device *dev, u64 *size)
        struct ceph_snap_context *snapc = header->snapc;
        int ret = -ENOENT;
 
-       BUILD_BUG_ON(sizeof (dev->snap_name) < sizeof (RBD_SNAP_HEAD_NAME));
-
        down_write(&dev->header_rwsem);
 
        if (!memcmp(dev->snap_name, RBD_SNAP_HEAD_NAME,
@@ -2390,16 +2388,22 @@ static int rbd_add_parse_args(struct rbd_device *rbd_dev,
        sprintf(rbd_dev->obj_md_name, "%s%s", rbd_dev->obj, RBD_SUFFIX);
 
        /*
-        * The snapshot name is optional, but it's an error if it's
-        * too long.  If no snapshot is supplied, fill in the default.
+        * The snapshot name is optional.  If none is is supplied,
+        * we use the default value.
         */
-       len = copy_token(&buf, rbd_dev->snap_name, sizeof (rbd_dev->snap_name));
-       if (!len)
+       rbd_dev->snap_name = dup_token(&buf, &len);
+       if (!rbd_dev->snap_name)
+               goto out_err;
+       if (!len) {
+               /* Replace the empty name with the default */
+               kfree(rbd_dev->snap_name);
+               rbd_dev->snap_name
+                       = kmalloc(sizeof (RBD_SNAP_HEAD_NAME), GFP_KERNEL);
+               if (!rbd_dev->snap_name)
+                       goto out_err;
+
                memcpy(rbd_dev->snap_name, RBD_SNAP_HEAD_NAME,
                        sizeof (RBD_SNAP_HEAD_NAME));
-       else if (len >= sizeof (rbd_dev->snap_name)) {
-               ret = -EINVAL;
-               goto out_err;
        }
 
        return 0;
@@ -2509,6 +2513,7 @@ err_out_client:
        rbd_put_client(rbd_dev);
 err_put_id:
        if (rbd_dev->pool_name) {
+               kfree(rbd_dev->snap_name);
                kfree(rbd_dev->obj_md_name);
                kfree(rbd_dev->obj);
                kfree(rbd_dev->pool_name);
@@ -2561,6 +2566,7 @@ static void rbd_dev_release(struct device *dev)
        unregister_blkdev(rbd_dev->major, rbd_dev->name);
 
        /* done with the id, and with the rbd_dev */
+       kfree(rbd_dev->snap_name);
        kfree(rbd_dev->obj_md_name);
        kfree(rbd_dev->pool_name);
        kfree(rbd_dev->obj);