libceph: add a compatibility check interface
An upcoming change implements semantic change that could lead to
a crash if an old version of the libceph kernel module is used with
a new version of the rbd kernel module.
In order to preclude that possibility, this adds a compatibilty
check interface. If this interface doesn't exist, the modules are
obviously not compatible. But if it does exist, this provides a way
of letting the caller know whether it will operate properly with
this libceph module.
Perhaps confusingly, it returns false right now. The semantic
change mentioned above will make it return true.
This resolves:
http://tracker.ceph.com/issues/3800
Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>
diff --git a/include/linux/ceph/libceph.h b/include/linux/ceph/libceph.h
index 084d3c6..c44275a 100644
--- a/include/linux/ceph/libceph.h
+++ b/include/linux/ceph/libceph.h
@@ -193,6 +193,8 @@
}
/* ceph_common.c */
+extern bool libceph_compatible(void *data);
+
extern const char *ceph_msg_type_name(int type);
extern int ceph_check_fsid(struct ceph_client *client, struct ceph_fsid *fsid);
extern struct kmem_cache *ceph_inode_cachep;