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
......@@ -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);
......
......@@ -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();
......
......@@ -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) {
......
......@@ -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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