mem-hotplug: fix potential race while building zonelist for new populated zone
Add global mutex zonelists_mutex to fix the possible race:
CPU0 CPU1 CPU2
(1) zone->present_pages += online_pages;
(2) build_all_zonelists();
(3) alloc_page();
(4) free_page();
(5) build_all_zonelists();
(6) __build_all_zonelists();
(7) zone->pageset = alloc_percpu();
In step (3,4), zone->pageset still points to boot_pageset, so bad
things may happen if 2+ nodes are in this state. Even if only 1 node
is accessing the boot_pageset, (3) may still consume too much memory
to fail the memory allocations in step (7).
Besides, atomic operation ensures alloc_percpu() in step (7) will never fail
since there is a new fresh memory block added in step(6).
[haicheng.li@linux.intel.com: hold zonelists_mutex when build_all_zonelists]
Signed-off-by: Haicheng Li <haicheng.li@linux.intel.com>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Reviewed-by: Andi Kleen <andi.kleen@intel.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 3e8b3ba..124ad9d 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -357,8 +357,11 @@
return -ENOMEM;
}
- if (pgdat->node_zonelists->_zonerefs->zone == NULL)
+ if (pgdat->node_zonelists->_zonerefs->zone == NULL) {
+ mutex_lock(&zonelists_mutex);
build_all_zonelists(NULL);
+ mutex_unlock(&zonelists_mutex);
+ }
#endif
cpu_maps_update_begin();