The patch titled
Subject: mem-hotplug: Fix wrong check for zone->pageset initialization in online_pages().
has been added to the -mm tree. Its filename is
mem-hotplug-fix-wrong-check-for-zone-pageset-initialization-in-online_pages.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mem-hotplug-fix-wrong-check-for-zone-pageset-initialization-in-online_pages.patch
echo and later at
echo http://ozlabs.org/~akpm/mmotm/broken-out/mem-hotplug-fix-wrong-check-for-zone-pageset-initialization-in-online_pages.patch
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------------------------------------------------------
From: Tang Chen <tangchen@xxxxxxxxxxxxxx>
Subject: mem-hotplug: Fix wrong check for zone->pageset initialization in online_pages().
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: Tang Chen <tangchen@xxxxxxxxxxxxxx>
Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki@xxxxxxxxxxxxxx>
Cc: Gu Zheng <guz.fnst@xxxxxxxxxxxxxx>
Cc: Santosh Shilimkar <santosh.shilimkar@xxxxxx>
Cc: Grygorii Strashko <grygorii.strashko@xxxxxx>
Cc: Yinghai Lu <yinghai@xxxxxxxxxx>
Cc: Wang Nan <wangnan0@xxxxxxxxxx>
Cc: Philipp Hachtmann <phacht@xxxxxxxxxxxxxxxxxx>
Cc: Xishi Qiu <qiuxishi@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/mm.h | 1 +
mm/memory_hotplug.c | 6 +++++-
mm/page_alloc.c | 5 +++++
3 files changed, 11 insertions(+), 1 deletion(-)
diff -puN include/linux/mm.h~mem-hotplug-fix-wrong-check-for-zone-pageset-initialization-in-online_pages include/linux/mm.h
--- a/include/linux/mm.h~mem-hotplug-fix-wrong-check-for-zone-pageset-initialization-in-online_pages
+++ a/include/linux/mm.h
@@ -1732,6 +1732,7 @@ void warn_alloc_failed(gfp_t gfp_mask, i
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 -puN mm/memory_hotplug.c~mem-hotplug-fix-wrong-check-for-zone-pageset-initialization-in-online_pages mm/memory_hotplug.c
--- a/mm/memory_hotplug.c~mem-hotplug-fix-wrong-check-for-zone-pageset-initialization-in-online_pages
+++ a/mm/memory_hotplug.c
@@ -1013,9 +1013,13 @@ int __ref online_pages(unsigned long pfn
* 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 -puN mm/page_alloc.c~mem-hotplug-fix-wrong-check-for-zone-pageset-initialization-in-online_pages mm/page_alloc.c
--- a/mm/page_alloc.c~mem-hotplug-fix-wrong-check-for-zone-pageset-initialization-in-online_pages
+++ a/mm/page_alloc.c
@@ -6453,6 +6453,11 @@ void __meminit zone_pcp_update(struct zo
}
#endif
+bool zone_pcp_initialized(struct zone *zone)
+{
+ return (zone->pageset != &boot_pageset);
+}
+
void zone_pcp_reset(struct zone *zone)
{
unsigned long flags;
_
Patches currently in -mm which might be from tangchen@xxxxxxxxxxxxxx are
mm-page_alloc-fix-incorrect-isolation-behavior-by-rechecking-migratetype.patch
mm-page_alloc-add-freepage-on-isolate-pageblock-to-correct-buddy-list.patch
mm-page_alloc-move-freepage-counting-logic-to-__free_one_page.patch
mm-page_alloc-restrict-max-order-of-merging-on-isolated-pageblock.patch
mem-hotplug-reset-node-managed-pages-when-hot-adding-a-new-pgdat.patch
mem-hotplug-fix-wrong-check-for-zone-pageset-initialization-in-online_pages.patch
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