[PATCH] memory hotplug: fix early allocation handling

[Heiko Carstens <heiko.carstens@de.ibm.com>]

Trying to add memory via add_memory() from within an initcall function
results in

bootmem alloc of 163840 bytes failed!
Kernel panic - not syncing: Out of memory

This is caused by zone_wait_table_init() which uses system_state to
decide if it should use the bootmem allocator or not.
When initcalls are handled the system_state is still SYSTEM_BOOTING
but the bootmem allocator doesn't work anymore. So the allocation
will fail.

To fix this use slab_is_available() instead as indicator like we do
it everywhere else.

Cc: Andy Whitcroft <apw@shadowen.org>
Cc: Dave Hansen <haveblue@us.ibm.com>
Cc: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Yasunori Goto <y-goto@jp.fujitsu.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
---
 mm/page_alloc.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Index: linux-2.6/mm/page_alloc.c
===================================================================
--- linux-2.6.orig/mm/page_alloc.c
+++ linux-2.6/mm/page_alloc.c
@@ -2804,7 +2804,7 @@ int zone_wait_table_init(struct zone *zo
 	alloc_size = zone->wait_table_hash_nr_entries
 					* sizeof(wait_queue_head_t);
 
- 	if (system_state == SYSTEM_BOOTING) {
+ 	if (!slab_is_available()) {
 		zone->wait_table = (wait_queue_head_t *)
 			alloc_bootmem_node(pgdat, alloc_size);
 	} else {

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