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@xxxxxxxxxxxxxx>
Signed-off-by: Tang Chen <tangchen@xxxxxxxxxxxxxx>
---
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
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