Commit 4eaf3f64 authored by Haicheng Li's avatar Haicheng Li Committed by Linus Torvalds
Browse files

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: default avatarHaicheng Li <haicheng.li@linux.intel.com>
Signed-off-by: default avatarWu Fengguang <fengguang.wu@intel.com>
Reviewed-by: default avatarAndi 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 1f522509

include/linux/mmzone.h

+1 −0
Original line number Diff line number Diff line
@@ -650,6 +650,7 @@ typedef struct pglist_data { 


#include <linux/memory_hotplug.h>



extern struct mutex zonelists_mutex;

void get_zone_counts(unsigned long *active, unsigned long *inactive,

			unsigned long *free);

void build_all_zonelists(void *data);

kernel/cpu.c

+4 −1
Original line number Diff line number Diff line
@@ -357,8 +357,11 @@ int __cpuinit cpu_up(unsigned int cpu) 
		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();

mm/memory_hotplug.c

+3 −8
Original line number Diff line number Diff line
@@ -389,11 +389,6 @@ int online_pages(unsigned long pfn, unsigned long nr_pages) 
	int nid;

	int ret;

	struct memory_notify arg;

	/*

	 * mutex to protect zone->pageset when it's still shared

	 * in onlined_pages()

	 */

	static DEFINE_MUTEX(zone_pageset_mutex);



	arg.start_pfn = pfn;

	arg.nr_pages = nr_pages;
@@ -420,14 +415,14 @@ int online_pages(unsigned long pfn, unsigned long nr_pages) 
	 * This means the page allocator ignores this zone.

	 * So, zonelist must be updated after online.

	 */

	mutex_lock(&zone_pageset_mutex);

	mutex_lock(&zonelists_mutex);

	if (!populated_zone(zone))

		need_zonelists_rebuild = 1;



	ret = walk_system_ram_range(pfn, nr_pages, &onlined_pages,

		online_pages_range);

	if (ret) {

		mutex_unlock(&zone_pageset_mutex);

		mutex_unlock(&zonelists_mutex);

		printk(KERN_DEBUG "online_pages %lx at %lx failed\n",

			nr_pages, pfn);

		memory_notify(MEM_CANCEL_ONLINE, &arg);
@@ -441,7 +436,7 @@ int online_pages(unsigned long pfn, unsigned long nr_pages) 
	else

		zone_pcp_update(zone);



	mutex_unlock(&zone_pageset_mutex);

	mutex_unlock(&zonelists_mutex);

	setup_per_zone_wmarks();

	calculate_zone_inactive_ratio(zone);

	if (onlined_pages) {

mm/page_alloc.c

+14 −1
Original line number Diff line number Diff line
@@ -2571,8 +2571,11 @@ int numa_zonelist_order_handler(ctl_table *table, int write, 
			strncpy((char*)table->data, saved_string,

				NUMA_ZONELIST_ORDER_LEN);

			user_zonelist_order = oldval;

		} else if (oldval != user_zonelist_order)

		} else if (oldval != user_zonelist_order) {

			mutex_lock(&zonelists_mutex);

			build_all_zonelists(NULL);

			mutex_unlock(&zonelists_mutex);

		}

	}

out:

	mutex_unlock(&zl_order_mutex);
@@ -2924,6 +2927,12 @@ static void setup_pageset(struct per_cpu_pageset *p, unsigned long batch); 
static DEFINE_PER_CPU(struct per_cpu_pageset, boot_pageset);

static void setup_zone_pageset(struct zone *zone);



/*

 * Global mutex to protect against size modification of zonelists

 * as well as to serialize pageset setup for the new populated zone.

 */

DEFINE_MUTEX(zonelists_mutex);



/* return values int ....just for stop_machine() */

static __init_refok int __build_all_zonelists(void *data)

{
@@ -2967,6 +2976,10 @@ static __init_refok int __build_all_zonelists(void *data) 
	return 0;

}



/*

 * Called with zonelists_mutex held always

 * unless system_state == SYSTEM_BOOTING.

 */

void build_all_zonelists(void *data)

{

	set_zonelist_order();

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