sysctl: Remember the ctl_table we passed to register_sysctl_paths

By doing this we allow users of register_sysctl_paths that build
and dynamically allocate their ctl_table to be simpler.  This allows
them to just remember the ctl_table_header returned from
register_sysctl_paths from which they can now find the
ctl_table array they need to free.
Signed-off-by: NEric W. Biederman <ebiederm@xmission.com>
Cc: Serge Hallyn <serue@us.ibm.com>
Cc: Daniel Lezcano <dlezcano@fr.ibm.com>
Cc: Cedric Le Goater <clg@fr.ibm.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/linux/sysctl.h

@@ -1057,6 +1057,7 @@ struct ctl_table_header
 	struct list_head ctl_entry;
 	int used;
 	struct completion *unregistering;
+	struct ctl_table *ctl_table_arg;
 };
 
 /* struct ctl_path describes where in the hierarchy a table is added */

kernel/sysctl.c

@@ -1669,6 +1669,7 @@ struct ctl_table_header *register_sysctl_paths(const struct ctl_path *path,
 		new += 2;
 	}
 	*prevp = table;
+	header->ctl_table_arg = table;
 
 	INIT_LIST_HEAD(&header->ctl_entry);
 	header->used = 0;