mm/memory_hotplug.c: move register_memory_resource out of the lock_memory_hotplug

We don't need to do register_memory_resource() under
lock_memory_hotplug() since it has its own lock and doesn't make any
callbacks.

Also register_memory_resource return NULL on failure so we don't have
anything to cleanup at this point.

The reason for this rfc is I was doing some experiments with hotplugging
of memory on some of our larger systems.  While it seems to work, it can
be quite slow.  With some preliminary digging I found that
lock_memory_hotplug is clearly ripe for breakup.

It could be broken up per nid or something but it also covers the
online_page_callback.  The online_page_callback shouldn't be very hard
to break out.

Also there is the issue of various structures(wmarks come to mind) that
are only updated under the lock_memory_hotplug that would need to be
dealt with.

Cc: Tang Chen <tangchen@cn.fujitsu.com>
Cc: Wen Congyang <wency@cn.fujitsu.com>
Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Cc: Hedi <hedi@sgi.com>
Cc: Mike Travis <travis@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index a512a47241a4e19cde1819c124c03a9091bb604e..a650db29606fe73171df9d7c5326da56bbec500b 100644 (file)
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1107,17 +1107,18 @@ int __ref add_memory(int nid, u64 start, u64 size)
        if (ret)
                return ret;
 
-       lock_memory_hotplug();
-
        res = register_memory_resource(start, size);
        ret = -EEXIST;
        if (!res)
-               goto out;
+               return ret;
 
        {       /* Stupid hack to suppress address-never-null warning */
                void *p = NODE_DATA(nid);
                new_pgdat = !p;
        }
+
+       lock_memory_hotplug();
+
        new_node = !node_online(nid);
        if (new_node) {
                pgdat = hotadd_new_pgdat(nid, start);