[PATCH 0/2] Fix node meminfo corruption.

[PATCH 0/2] Fix node meminfo corruption.

[Tang Chen]

There are two problems when calculating node meminfo:

1. When hot-adding a node without onlining any page, MemTotal corrupted.

# hot-add node2 (memory not onlined)
# cat /sys/device/system/node/node2/meminfo
Node 2 MemTotal:       33554432 kB			/* corrupted */
Node 2 MemFree:               0 kB
Node 2 MemUsed:        33554432 kB
Node 2 Active:                0 kB
......


2. When onlining memory on node2, MemFree of node3 corrupted.

# for ((i = 2048; i < 2064; i++)); do echo online_movable > /sys/devices/system/node/node2/memory$i/state; done
# cat /sys/devices/system/node/node2/meminfo
Node 2 MemTotal:       33554432 kB
Node 2 MemFree:        33549092 kB
Node 2 MemUsed:            5340 kB
......
# cat /sys/devices/system/node/node3/meminfo
Node 3 MemTotal:              0 kB
Node 3 MemFree:               248 kB                    /* corrupted */
Node 3 MemUsed:               0 kB
......

This patch-set fixes them.

Tang Chen (2):
  mem-hotplug: Reset node managed pages when hot-adding a new pgdat.
  mem-hotplug: Fix wrong check for zone->pageset initialization in
    online_pages().

 include/linux/bootmem.h |  1 +
 include/linux/mm.h      |  1 +
 mm/bootmem.c            |  9 +++++----
 mm/memory_hotplug.c     | 15 ++++++++++++++-
 mm/nobootmem.c          |  8 +++++---
 mm/page_alloc.c         |  5 +++++
 6 files changed, 31 insertions(+), 8 deletions(-)

-- 
1.8.3.1

[PATCH 1/2] mem-hotplug: Reset node managed pages when hot-adding a new pgdat.

[Tang Chen]

In free_area_init_core(), zone->managed_pages is set to an approximate
value for lowmem, and will be adjusted when the bootmem allocator frees
pages into the buddy system. But free_area_init_core() is also called
by hotadd_new_pgdat() when hot-adding memory. As a result, zone->managed_pages
of the newly added node's pgdat is set to an approximate value in the
very beginning. Even if the memory on that node has node been onlined,
/sys/device/system/node/nodeXXX/meminfo has wrong value.

hot-add node2 (memory not onlined)
cat /sys/device/system/node/node2/meminfo
Node 2 MemTotal:       33554432 kB
Node 2 MemFree:               0 kB
Node 2 MemUsed:        33554432 kB
Node 2 Active:                0 kB

This patch fixes this problem by reset node managed pages to 0 after hot-adding
a new node.

1. Move reset_managed_pages_done from reset_node_managed_pages() to reset_all_zones_managed_pages()
2. Make reset_node_managed_pages() non-static
3. Call reset_node_managed_pages() in hotadd_new_pgdat() after pgdat is initialized

Signed-off-by: Tang Chen <tangchen@cn.fujitsu.com>
Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
---
 include/linux/bootmem.h | 1 +
 mm/bootmem.c            | 9 +++++----
 mm/memory_hotplug.c     | 9 +++++++++
 mm/nobootmem.c          | 8 +++++---
 4 files changed, 20 insertions(+), 7 deletions(-)

diff --git a/include/linux/bootmem.h b/include/linux/bootmem.h
index 4e2bd4c..0995c2d 100644
--- a/include/linux/bootmem.h
+++ b/include/linux/bootmem.h
@@ -46,6 +46,7 @@ extern unsigned long init_bootmem_node(pg_data_t *pgdat,
 extern unsigned long init_bootmem(unsigned long addr, unsigned long memend);
 
 extern unsigned long free_all_bootmem(void);
+extern void reset_node_managed_pages(pg_data_t *pgdat);
 extern void reset_all_zones_managed_pages(void);
 
 extern void free_bootmem_node(pg_data_t *pgdat,
diff --git a/mm/bootmem.c b/mm/bootmem.c
index 8a000ce..477be69 100644
--- a/mm/bootmem.c
+++ b/mm/bootmem.c
@@ -243,13 +243,10 @@ static unsigned long __init free_all_bootmem_core(bootmem_data_t *bdata)
 
 static int reset_managed_pages_done __initdata;
 
-static inline void __init reset_node_managed_pages(pg_data_t *pgdat)
+void reset_node_managed_pages(pg_data_t *pgdat)
 {
 	struct zone *z;
 
-	if (reset_managed_pages_done)
-		return;
-
 	for (z = pgdat->node_zones; z < pgdat->node_zones + MAX_NR_ZONES; z++)
 		z->managed_pages = 0;
 }
@@ -258,8 +255,12 @@ void __init reset_all_zones_managed_pages(void)
 {
 	struct pglist_data *pgdat;
 
+	if (reset_managed_pages_done)
+		return;
+
 	for_each_online_pgdat(pgdat)
 		reset_node_managed_pages(pgdat);
+
 	reset_managed_pages_done = 1;
 }
 
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 29d8693..3ab01b2 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -31,6 +31,7 @@
 #include <linux/stop_machine.h>
 #include <linux/hugetlb.h>
 #include <linux/memblock.h>
+#include <linux/bootmem.h>
 
 #include <asm/tlbflush.h>
 
@@ -1096,6 +1097,14 @@ static pg_data_t __ref *hotadd_new_pgdat(int nid, u64 start)
 	build_all_zonelists(pgdat, NULL);
 	mutex_unlock(&zonelists_mutex);
 
+	/*
+	 *  zone->managed_pages is set to an approximate value in
+	 *  free_area_init_core(), which will cause
+	 *  /sys/device/system/node/nodeX/meminfo has wrong data.
+	 *  So reset it to 0 before any memory is onlined.
+	 */
+	reset_node_managed_pages(pgdat);
+
 	return pgdat;
 }
 
diff --git a/mm/nobootmem.c b/mm/nobootmem.c
index 7c7ab32..90b5046 100644
--- a/mm/nobootmem.c
+++ b/mm/nobootmem.c
@@ -145,12 +145,10 @@ static unsigned long __init free_low_memory_core_early(void)
 
 static int reset_managed_pages_done __initdata;
 
-static inline void __init reset_node_managed_pages(pg_data_t *pgdat)
+void reset_node_managed_pages(pg_data_t *pgdat)
 {
 	struct zone *z;
 
-	if (reset_managed_pages_done)
-		return;
 	for (z = pgdat->node_zones; z < pgdat->node_zones + MAX_NR_ZONES; z++)
 		z->managed_pages = 0;
 }
@@ -159,8 +157,12 @@ void __init reset_all_zones_managed_pages(void)
 {
 	struct pglist_data *pgdat;
 
+	if (reset_managed_pages_done)
+		return;
+
 	for_each_online_pgdat(pgdat)
 		reset_node_managed_pages(pgdat);
+
 	reset_managed_pages_done = 1;
 }
 
-- 
1.8.3.1

[PATCH 2/2] mem-hotplug: Fix wrong check for zone->pageset initialization in online_pages().

[Tang Chen]

When we are doing memory hot-add, the following functions are called:

add_memory()
|--> hotadd_new_pgdat()
     |--> free_area_init_node()
          |--> free_area_init_core()
               |--> zone->present_pages = realsize;           /* 1. zone is populated */
                    |--> zone_pcp_init()
                         |--> zone->pageset = &boot_pageset;  /* 2. zone->pageset is set to boot_pageset */

There are two problems here:
1. Zones could be populated before any memory is onlined.
2. All the zones on a newly added node have the same pageset pointing to boot_pageset.

The above two problems will result in the following problem:
When we online memory on one node, e.g node2, the following code is executed:

online_pages()
{
        ......
        if (!populated_zone(zone)) {
                need_zonelists_rebuild = 1;
                build_all_zonelists(NULL, zone);
        }
        ......
}

Because of problem 1, the zone has been populated, and the build_all_zonelists()
                      will never called. zone->pageset won't be updated.
Because of problem 2, All the zones on a newly added node have the same pageset
                      pointing to boot_pageset.
And as a result, when we online memory on node2, node3's meminfo will corrupt.
Pages on node2 may be freed to node3.

# for ((i = 2048; i < 2064; i++)); do echo online_movable > /sys/devices/system/node/node2/memory$i/state; done
# cat /sys/devices/system/node/node2/meminfo
Node 2 MemTotal:       33554432 kB
Node 2 MemFree:        33549092 kB
Node 2 MemUsed:            5340 kB
......
# cat /sys/devices/system/node/node3/meminfo
Node 3 MemTotal:              0 kB
Node 3 MemFree:               248 kB                    /* corrupted */
Node 3 MemUsed:               0 kB
......

We have to populate some zones before onlining memory, otherwise no memory could be onlined.
So when onlining pages, we should also check if zone->pageset is pointing to boot_pageset.

Signed-off-by: Gu Zheng <guz.fnst@cn.fujitsu.com>
Signed-off-by: Tang Chen <tangchen@cn.fujitsu.com>
---
 include/linux/mm.h  | 1 +
 mm/memory_hotplug.c | 6 +++++-
 mm/page_alloc.c     | 5 +++++
 3 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 02d11ee..83e6505 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1732,6 +1732,7 @@ void warn_alloc_failed(gfp_t gfp_mask, int order, const char *fmt, ...);
 
 extern void setup_per_cpu_pageset(void);
 
+extern bool zone_pcp_initialized(struct zone *zone);
 extern void zone_pcp_update(struct zone *zone);
 extern void zone_pcp_reset(struct zone *zone);
 
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 3ab01b2..bc0de0f 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1013,9 +1013,13 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_typ
 	 * If this zone is not populated, then it is not in zonelist.
 	 * This means the page allocator ignores this zone.
 	 * So, zonelist must be updated after online.
+	 *
+	 * If this zone is populated, zone->pageset could be initialized
+	 * to boot_pageset for the first time a node is added. If so,
+	 * zone->pageset should be allocated.
 	 */
 	mutex_lock(&zonelists_mutex);
-	if (!populated_zone(zone)) {
+	if (!populated_zone(zone) || !zone_pcp_initialized(zone)) {
 		need_zonelists_rebuild = 1;
 		build_all_zonelists(NULL, zone);
 	}
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 736d8e1..4ff1540 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -6456,6 +6456,11 @@ void __meminit zone_pcp_update(struct zone *zone)
 }
 #endif
 
+bool zone_pcp_initialized(struct zone *zone)
+{
+	return (zone->pageset != &boot_pageset);
+}
+
 void zone_pcp_reset(struct zone *zone)
 {
 	unsigned long flags;
-- 
1.8.3.1

Re: [PATCH 0/2] Fix node meminfo corruption.

[Tang Chen]

Hi all,

I thinks these two problems are very important and should be merged ASAP.
Would you please help to have a look at it ?

Thanks.

On 10/31/2014 05:46 PM, Tang Chen wrote:
> There are two problems when calculating node meminfo:
>
> 1. When hot-adding a node without onlining any page, MemTotal corrupted.
>
> # hot-add node2 (memory not onlined)
> # cat /sys/device/system/node/node2/meminfo
> Node 2 MemTotal:       33554432 kB			/* corrupted */
> Node 2 MemFree:               0 kB
> Node 2 MemUsed:        33554432 kB
> Node 2 Active:                0 kB
> ......
>
>
> 2. When onlining memory on node2, MemFree of node3 corrupted.
>
> # for ((i = 2048; i < 2064; i++)); do echo online_movable > /sys/devices/system/node/node2/memory$i/state; done
> # cat /sys/devices/system/node/node2/meminfo
> Node 2 MemTotal:       33554432 kB
> Node 2 MemFree:        33549092 kB
> Node 2 MemUsed:            5340 kB
> ......
> # cat /sys/devices/system/node/node3/meminfo
> Node 3 MemTotal:              0 kB
> Node 3 MemFree:               248 kB                    /* corrupted */
> Node 3 MemUsed:               0 kB
> ......
>
> This patch-set fixes them.
>
> Tang Chen (2):
>    mem-hotplug: Reset node managed pages when hot-adding a new pgdat.
>    mem-hotplug: Fix wrong check for zone->pageset initialization in
>      online_pages().
>
>   include/linux/bootmem.h |  1 +
>   include/linux/mm.h      |  1 +
>   mm/bootmem.c            |  9 +++++----
>   mm/memory_hotplug.c     | 15 ++++++++++++++-
>   mm/nobootmem.c          |  8 +++++---
>   mm/page_alloc.c         |  5 +++++
>   6 files changed, 31 insertions(+), 8 deletions(-)
>

Re: [PATCH 1/2] mem-hotplug: Reset node managed pages when hot-adding a new pgdat.

[Xishi Qiu]

On 2014/10/31 17:46, Tang Chen wrote:

> In free_area_init_core(), zone->managed_pages is set to an approximate
> value for lowmem, and will be adjusted when the bootmem allocator frees
> pages into the buddy system. But free_area_init_core() is also called
> by hotadd_new_pgdat() when hot-adding memory. As a result, zone->managed_pages
> of the newly added node's pgdat is set to an approximate value in the
> very beginning. Even if the memory on that node has node been onlined,
> /sys/device/system/node/nodeXXX/meminfo has wrong value.
> 
> hot-add node2 (memory not onlined)
> cat /sys/device/system/node/node2/meminfo
> Node 2 MemTotal:       33554432 kB
> Node 2 MemFree:               0 kB
> Node 2 MemUsed:        33554432 kB
> Node 2 Active:                0 kB
> 
> This patch fixes this problem by reset node managed pages to 0 after hot-adding
> a new node.
> 
> 1. Move reset_managed_pages_done from reset_node_managed_pages() to reset_all_zones_managed_pages()
> 2. Make reset_node_managed_pages() non-static
> 3. Call reset_node_managed_pages() in hotadd_new_pgdat() after pgdat is initialized
> 
> Signed-off-by: Tang Chen <tangchen@cn.fujitsu.com>
> Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
> ---
>  include/linux/bootmem.h | 1 +
>  mm/bootmem.c            | 9 +++++----
>  mm/memory_hotplug.c     | 9 +++++++++
>  mm/nobootmem.c          | 8 +++++---
>  4 files changed, 20 insertions(+), 7 deletions(-)
> 
> diff --git a/include/linux/bootmem.h b/include/linux/bootmem.h
> index 4e2bd4c..0995c2d 100644
> --- a/include/linux/bootmem.h
> +++ b/include/linux/bootmem.h
> @@ -46,6 +46,7 @@ extern unsigned long init_bootmem_node(pg_data_t *pgdat,
>  extern unsigned long init_bootmem(unsigned long addr, unsigned long memend);
>  
>  extern unsigned long free_all_bootmem(void);
> +extern void reset_node_managed_pages(pg_data_t *pgdat);
>  extern void reset_all_zones_managed_pages(void);
>  
>  extern void free_bootmem_node(pg_data_t *pgdat,
> diff --git a/mm/bootmem.c b/mm/bootmem.c
> index 8a000ce..477be69 100644
> --- a/mm/bootmem.c
> +++ b/mm/bootmem.c
> @@ -243,13 +243,10 @@ static unsigned long __init free_all_bootmem_core(bootmem_data_t *bdata)
>  
>  static int reset_managed_pages_done __initdata;
>  
> -static inline void __init reset_node_managed_pages(pg_data_t *pgdat)
> +void reset_node_managed_pages(pg_data_t *pgdat)
>  {
>  	struct zone *z;
>  
> -	if (reset_managed_pages_done)
> -		return;
> -
>  	for (z = pgdat->node_zones; z < pgdat->node_zones + MAX_NR_ZONES; z++)
>  		z->managed_pages = 0;
>  }
> @@ -258,8 +255,12 @@ void __init reset_all_zones_managed_pages(void)
>  {
>  	struct pglist_data *pgdat;
>  
> +	if (reset_managed_pages_done)
> +		return;
> +
>  	for_each_online_pgdat(pgdat)
>  		reset_node_managed_pages(pgdat);
> +
>  	reset_managed_pages_done = 1;
>  }
>  
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 29d8693..3ab01b2 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -31,6 +31,7 @@
>  #include <linux/stop_machine.h>
>  #include <linux/hugetlb.h>
>  #include <linux/memblock.h>
> +#include <linux/bootmem.h>
>  
>  #include <asm/tlbflush.h>
>  
> @@ -1096,6 +1097,14 @@ static pg_data_t __ref *hotadd_new_pgdat(int nid, u64 start)
>  	build_all_zonelists(pgdat, NULL);
>  	mutex_unlock(&zonelists_mutex);
>  
> +	/*
> +	 *  zone->managed_pages is set to an approximate value in
> +	 *  free_area_init_core(), which will cause
> +	 *  /sys/device/system/node/nodeX/meminfo has wrong data.
> +	 *  So reset it to 0 before any memory is onlined.
> +	 */
> +	reset_node_managed_pages(pgdat);
> +

I aggree with you, we should reset it before online pages.

Thanks,
Xishi Qiu

>  	return pgdat;
>  }
>  
> diff --git a/mm/nobootmem.c b/mm/nobootmem.c
> index 7c7ab32..90b5046 100644
> --- a/mm/nobootmem.c
> +++ b/mm/nobootmem.c
> @@ -145,12 +145,10 @@ static unsigned long __init free_low_memory_core_early(void)
>  
>  static int reset_managed_pages_done __initdata;
>  
> -static inline void __init reset_node_managed_pages(pg_data_t *pgdat)
> +void reset_node_managed_pages(pg_data_t *pgdat)
>  {
>  	struct zone *z;
>  
> -	if (reset_managed_pages_done)
> -		return;
>  	for (z = pgdat->node_zones; z < pgdat->node_zones + MAX_NR_ZONES; z++)
>  		z->managed_pages = 0;
>  }
> @@ -159,8 +157,12 @@ void __init reset_all_zones_managed_pages(void)
>  {
>  	struct pglist_data *pgdat;
>  
> +	if (reset_managed_pages_done)
> +		return;
> +
>  	for_each_online_pgdat(pgdat)
>  		reset_node_managed_pages(pgdat);
> +
>  	reset_managed_pages_done = 1;
>  }
>  

Re: [PATCH 2/2] mem-hotplug: Fix wrong check for zone->pageset initialization in online_pages().

[Yasuaki Ishimatsu]

(2014/10/31 18:46), Tang Chen wrote:
> When we are doing memory hot-add, the following functions are called:
> 
> add_memory()
> |--> hotadd_new_pgdat()
>       |--> free_area_init_node()
>            |--> free_area_init_core()
>                 |--> zone->present_pages = realsize;           /* 1. zone is populated */
>                      |--> zone_pcp_init()
>                           |--> zone->pageset = &boot_pageset;  /* 2. zone->pageset is set to boot_pageset */
> 
> There are two problems here:
> 1. Zones could be populated before any memory is onlined.
> 2. All the zones on a newly added node have the same pageset pointing to boot_pageset.
> 
> The above two problems will result in the following problem:
> When we online memory on one node, e.g node2, the following code is executed:
> 
> online_pages()
> {
>          ......
>          if (!populated_zone(zone)) {
>                  need_zonelists_rebuild = 1;
>                  build_all_zonelists(NULL, zone);
>          }
>          ......
> }
> 
> Because of problem 1, the zone has been populated, and the build_all_zonelists()
>                        will never called. zone->pageset won't be updated.
> Because of problem 2, All the zones on a newly added node have the same pageset
>                        pointing to boot_pageset.
> And as a result, when we online memory on node2, node3's meminfo will corrupt.
> Pages on node2 may be freed to node3.
> 
> # for ((i = 2048; i < 2064; i++)); do echo online_movable > /sys/devices/system/node/node2/memory$i/state; done
> # cat /sys/devices/system/node/node2/meminfo
> Node 2 MemTotal:       33554432 kB
> Node 2 MemFree:        33549092 kB
> Node 2 MemUsed:            5340 kB
> ......
> # cat /sys/devices/system/node/node3/meminfo
> Node 3 MemTotal:              0 kB
> Node 3 MemFree:               248 kB                    /* corrupted */
> Node 3 MemUsed:               0 kB
> ......
> 
> We have to populate some zones before onlining memory, otherwise no memory could be onlined.
> So when onlining pages, we should also check if zone->pageset is pointing to boot_pageset.
> 
> Signed-off-by: Gu Zheng <guz.fnst@cn.fujitsu.com>
> Signed-off-by: Tang Chen <tangchen@cn.fujitsu.com>
> ---
>   include/linux/mm.h  | 1 +
>   mm/memory_hotplug.c | 6 +++++-
>   mm/page_alloc.c     | 5 +++++
>   3 files changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 02d11ee..83e6505 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1732,6 +1732,7 @@ void warn_alloc_failed(gfp_t gfp_mask, int order, const char *fmt, ...);
>   
>   extern void setup_per_cpu_pageset(void);
>   
> +extern bool zone_pcp_initialized(struct zone *zone);
>   extern void zone_pcp_update(struct zone *zone);
>   extern void zone_pcp_reset(struct zone *zone);
>   
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 3ab01b2..bc0de0f 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1013,9 +1013,13 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_typ
>   	 * If this zone is not populated, then it is not in zonelist.
>   	 * This means the page allocator ignores this zone.
>   	 * So, zonelist must be updated after online.
> +	 *
> +	 * If this zone is populated, zone->pageset could be initialized
> +	 * to boot_pageset for the first time a node is added. If so,
> +	 * zone->pageset should be allocated.
>   	 */
>   	mutex_lock(&zonelists_mutex);
> -	if (!populated_zone(zone)) {

> +	if (!populated_zone(zone) || !zone_pcp_initialized(zone)) {
>   		need_zonelists_rebuild = 1;
>   		build_all_zonelists(NULL, zone);
>   	}

Why does zone->present_pages of the hot-added memroy have valid value?
In my understading, the present_pages is incremented/decremented by memory
online/offline. So when hot adding memory, the zone->present_pages of the
memory should be 0.

Thanks,
Yasuaki Ishimatsu


> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 736d8e1..4ff1540 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -6456,6 +6456,11 @@ void __meminit zone_pcp_update(struct zone *zone)
>   }
>   #endif
>   
> +bool zone_pcp_initialized(struct zone *zone)
> +{
> +	return (zone->pageset != &boot_pageset);
> +}
> +
>   void zone_pcp_reset(struct zone *zone)
>   {
>   	unsigned long flags;
> 

Re: [PATCH 2/2] mem-hotplug: Fix wrong check for zone->pageset initialization in online_pages().

[Tang Chen]

On 11/04/2014 04:10 PM, Yasuaki Ishimatsu wrote:
> (2014/10/31 18:46), Tang Chen wrote:
>> When we are doing memory hot-add, the following functions are called:
>>
>> add_memory()
>> |--> hotadd_new_pgdat()
>>       |--> free_area_init_node()
>>            |--> free_area_init_core()
>>                 |--> zone->present_pages = realsize;           /* 1. zone is populated */
>>                      |--> zone_pcp_init()
>>                           |--> zone->pageset = &boot_pageset;  /* 2. zone->pageset is set to boot_pageset */
>>
>> There are two problems here:
>> 1. Zones could be populated before any memory is onlined.
>> 2. All the zones on a newly added node have the same pageset pointing to boot_pageset.
>>
>> The above two problems will result in the following problem:
>> When we online memory on one node, e.g node2, the following code is executed:
>>
>> online_pages()
>> {
>>          ......
>>          if (!populated_zone(zone)) {
>>                  need_zonelists_rebuild = 1;
>>                  build_all_zonelists(NULL, zone);
>>          }
>>          ......
>> }
>>
>> Because of problem 1, the zone has been populated, and the build_all_zonelists()
>>                        will never called. zone->pageset won't be updated.
>> Because of problem 2, All the zones on a newly added node have the same pageset
>>                        pointing to boot_pageset.
>> And as a result, when we online memory on node2, node3's meminfo will corrupt.
>> Pages on node2 may be freed to node3.
>>
>> # for ((i = 2048; i < 2064; i++)); do echo online_movable > /sys/devices/system/node/node2/memory$i/state; done
>> # cat /sys/devices/system/node/node2/meminfo
>> Node 2 MemTotal:       33554432 kB
>> Node 2 MemFree:        33549092 kB
>> Node 2 MemUsed:            5340 kB
>> ......
>> # cat /sys/devices/system/node/node3/meminfo
>> Node 3 MemTotal:              0 kB
>> Node 3 MemFree:               248 kB                    /* corrupted */
>> Node 3 MemUsed:               0 kB
>> ......
>>
>> We have to populate some zones before onlining memory, otherwise no memory could be onlined.
>> So when onlining pages, we should also check if zone->pageset is pointing to boot_pageset.
>>
>> Signed-off-by: Gu Zheng <guz.fnst@cn.fujitsu.com>
>> Signed-off-by: Tang Chen <tangchen@cn.fujitsu.com>
>> ---
>>   include/linux/mm.h  | 1 +
>>   mm/memory_hotplug.c | 6 +++++-
>>   mm/page_alloc.c     | 5 +++++
>>   3 files changed, 11 insertions(+), 1 deletion(-)
>>
>> diff --git a/include/linux/mm.h b/include/linux/mm.h
>> index 02d11ee..83e6505 100644
>> --- a/include/linux/mm.h
>> +++ b/include/linux/mm.h
>> @@ -1732,6 +1732,7 @@ void warn_alloc_failed(gfp_t gfp_mask, int order, const char *fmt, ...);
>>   
>>   extern void setup_per_cpu_pageset(void);
>>   
>> +extern bool zone_pcp_initialized(struct zone *zone);
>>   extern void zone_pcp_update(struct zone *zone);
>>   extern void zone_pcp_reset(struct zone *zone);
>>   
>> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
>> index 3ab01b2..bc0de0f 100644
>> --- a/mm/memory_hotplug.c
>> +++ b/mm/memory_hotplug.c
>> @@ -1013,9 +1013,13 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_typ
>>   	 * If this zone is not populated, then it is not in zonelist.
>>   	 * This means the page allocator ignores this zone.
>>   	 * So, zonelist must be updated after online.
>> +	 *
>> +	 * If this zone is populated, zone->pageset could be initialized
>> +	 * to boot_pageset for the first time a node is added. If so,
>> +	 * zone->pageset should be allocated.
>>   	 */
>>   	mutex_lock(&zonelists_mutex);
>> -	if (!populated_zone(zone)) {
>> +	if (!populated_zone(zone) || !zone_pcp_initialized(zone)) {
>>   		need_zonelists_rebuild = 1;
>>   		build_all_zonelists(NULL, zone);
>>   	}
> Why does zone->present_pages of the hot-added memroy have valid value?
> In my understading, the present_pages is incremented/decremented by memory
> online/offline. So when hot adding memory, the zone->present_pages of the
> memory should be 0.

Before zone->managed_pages was introduced, zone->present_pages had been
abused.
It had two meaning:
1. pages existing in the zone
2. pages managed by buddy system in the zone

So, zone->managed_pages was introduced. Now, it looks like:
1. zone->present_pages is the pages existing in the zone
2. zone->managed_pages is the pages managed by buddy system

So when hot adding memory, the zone->present_pages should not be 0.
zone->managed_pages should be 0. And here, since zone->managed_pages
is updated in online_pages_range() callback, I think we should remove
zone->present_pages and node_present_pages updates from online_pages().


Furthermore, since we can online pages or online_movable pages,
zones in a node could be changed. So we should update zone->present_pages
when pfn is moved left or right.

Thanks.

>
> Thanks,
> Yasuaki Ishimatsu
>
>
>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>> index 736d8e1..4ff1540 100644
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -6456,6 +6456,11 @@ void __meminit zone_pcp_update(struct zone *zone)
>>   }
>>   #endif
>>   
>> +bool zone_pcp_initialized(struct zone *zone)
>> +{
>> +	return (zone->pageset != &boot_pageset);
>> +}
>> +
>>   void zone_pcp_reset(struct zone *zone)
>>   {
>>   	unsigned long flags;
>>
>
> .
>

Re: [PATCH 2/2] mem-hotplug: Fix wrong check for zone->pageset initialization in online_pages().

[Kamezawa Hiroyuki]

(2014/10/31 18:46), Tang Chen wrote:
> When we are doing memory hot-add, the following functions are called:
> 
> add_memory()
> |--> hotadd_new_pgdat()
>       |--> free_area_init_node()
>            |--> free_area_init_core()
>                 |--> zone->present_pages = realsize;           /* 1. zone is populated */
>                      |--> zone_pcp_init()
>                           |--> zone->pageset = &boot_pageset;  /* 2. zone->pageset is set to boot_pageset */
> 
> There are two problems here:
> 1. Zones could be populated before any memory is onlined.
> 2. All the zones on a newly added node have the same pageset pointing to boot_pageset.
> 
> The above two problems will result in the following problem:
> When we online memory on one node, e.g node2, the following code is executed:
> 
> online_pages()
> {
>          ......
>          if (!populated_zone(zone)) {
>                  need_zonelists_rebuild = 1;
>                  build_all_zonelists(NULL, zone);
>          }
>          ......
> }
> 
> Because of problem 1, the zone has been populated, and the build_all_zonelists()
>                        will never called. zone->pageset won't be updated.
> Because of problem 2, All the zones on a newly added node have the same pageset
>                        pointing to boot_pageset.
> And as a result, when we online memory on node2, node3's meminfo will corrupt.
> Pages on node2 may be freed to node3.
> 
> # for ((i = 2048; i < 2064; i++)); do echo online_movable > /sys/devices/system/node/node2/memory$i/state; done
> # cat /sys/devices/system/node/node2/meminfo
> Node 2 MemTotal:       33554432 kB
> Node 2 MemFree:        33549092 kB
> Node 2 MemUsed:            5340 kB
> ......
> # cat /sys/devices/system/node/node3/meminfo
> Node 3 MemTotal:              0 kB
> Node 3 MemFree:               248 kB                    /* corrupted */
> Node 3 MemUsed:               0 kB
> ......
> 
> We have to populate some zones before onlining memory, otherwise no memory could be onlined.
> So when onlining pages, we should also check if zone->pageset is pointing to boot_pageset.
> 
> Signed-off-by: Gu Zheng <guz.fnst@cn.fujitsu.com>
> Signed-off-by: Tang Chen <tangchen@cn.fujitsu.com>
> ---
>   include/linux/mm.h  | 1 +
>   mm/memory_hotplug.c | 6 +++++-
>   mm/page_alloc.c     | 5 +++++
>   3 files changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 02d11ee..83e6505 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1732,6 +1732,7 @@ void warn_alloc_failed(gfp_t gfp_mask, int order, const char *fmt, ...);
>   
>   extern void setup_per_cpu_pageset(void);
>   
> +extern bool zone_pcp_initialized(struct zone *zone);
>   extern void zone_pcp_update(struct zone *zone);
>   extern void zone_pcp_reset(struct zone *zone);
>   
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 3ab01b2..bc0de0f 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1013,9 +1013,13 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_typ
>   	 * If this zone is not populated, then it is not in zonelist.
>   	 * This means the page allocator ignores this zone.
>   	 * So, zonelist must be updated after online.
> +	 *
> +	 * If this zone is populated, zone->pageset could be initialized
> +	 * to boot_pageset for the first time a node is added. If so,
> +	 * zone->pageset should be allocated.
>   	 */
>   	mutex_lock(&zonelists_mutex);
> -	if (!populated_zone(zone)) {
> +	if (!populated_zone(zone) || !zone_pcp_initialized(zone)) {

Please don't add another strange meanings to zone's pcplist.

If you say zone->present_pages doesn't mean zone has pages in buddy list any more,
please rewrite all parts using zone->present_pages including populated_zone().
I think there are several parts calculates parameters based on present_pages.

I myself doesn't welcome having both of compliated "managed pages" and "present pages"...

How about adding 

static inline int managed_zone(struct zone *zone)
{
	return (!!zone->managed_pages);
}

for this bug fix ?

Other parts, using present_pages, should be considered well.

Thanks,
-Kame

Thanks,
-Kame


>   		need_zonelists_rebuild = 1;
>   		build_all_zonelists(NULL, zone);
>   	}
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 736d8e1..4ff1540 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -6456,6 +6456,11 @@ void __meminit zone_pcp_update(struct zone *zone)
>   }
>   #endif
>   
> +bool zone_pcp_initialized(struct zone *zone)
> +{
> +	return (zone->pageset != &boot_pageset);
> +}
> +
>   void zone_pcp_reset(struct zone *zone)
>   {
>   	unsigned long flags;
> 

Re: [PATCH 2/2] mem-hotplug: Fix wrong check for zone->pageset initialization in online_pages().

[Tang Chen]

On 11/05/2014 09:01 AM, Kamezawa Hiroyuki wrote:
> ......
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 3ab01b2..bc0de0f 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1013,9 +1013,13 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_typ
>   	 * If this zone is not populated, then it is not in zonelist.
>   	 * This means the page allocator ignores this zone.
>   	 * So, zonelist must be updated after online.
> +	 *
> +	 * If this zone is populated, zone->pageset could be initialized
> +	 * to boot_pageset for the first time a node is added. If so,
> +	 * zone->pageset should be allocated.
>   	 */
>   	mutex_lock(&zonelists_mutex);
> -	if (!populated_zone(zone)) {
> +	if (!populated_zone(zone) || !zone_pcp_initialized(zone)) {
> Please don't add another strange meanings to zone's pcplist.
>
> If you say zone->present_pages doesn't mean zone has pages in buddy list any more,
> please rewrite all parts using zone->present_pages including populated_zone().

Adding Liu Jiang...

I think zone->managed_pages was introduced by Liu Jiang in the following
patch:

>From 9feedc9d831e18ae6d0d15aa562e5e46ba53647b Mon Sep 17 00:00:00 2001
From: Jiang Liu <liuj97@gmail.com>
Date: Wed, 12 Dec 2012 13:52:12 -0800
Subject: [PATCH 1/1] mm: introduce new field "managed_pages" to struct zone

Before this patch, zone->present_pages meant "amount of memory
(excluding holes)",
not the zone has pages in buddy system.

So I think zone->present_pages keeps its meaning as before. But it may
be abused
somewhere else, such as here.

> I think there are several parts calculates parameters based on present_pages.
>
> I myself doesn't welcome having both of compliated "managed pages" and "present pages"...
>
> How about adding 
>
> static inline int managed_zone(struct zone *zone)
> {
> 	return (!!zone->managed_pages);
> }
>
> for this bug fix ?

Yes, adding this function could fix this problem.

And by the way, we have the following code in onine_pages():

zone->present_pages += onlined_pages;

pgdat_resize_lock(zone->zone_pgdat, &flags);
zone->zone_pgdat->node_present_pages += onlined_pages;
pgdat_resize_unlock(zone->zone_pgdat, &flags);

We should do this when the zone size is changed, not where it is now.
Will send patches for this soon.

Thanks.

>
> Other parts, using present_pages, should be considered well.
>
>