The patch titled
mm/memory_hotplug.c:online_pages(): add memory-hotplug locking
has been added to the -mm tree. Its filename is
mm-memory_hotplugc-online_pages-add-memory-hotplug-locking.patch
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------------------------------------------------------
Subject: mm/memory_hotplug.c:online_pages(): add memory-hotplug locking
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
memory_hotplug_(un)lock() is used for add/remove/offline pages for
avoiding races with hibernation. But this should be held in
online_pages(), too. It seems asymmetric.
There are cases where one has to avoid a race with memory hotplug notifier
and his own local code, and hotplug v.s. hotplug. This will add a
generic solution for avoiding races. In other view, having lock here has
no big impacts. online pages is tend to be done by udev script at el
against each memory section one by one.
Then, it's better to have lock here, too.
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Reviewed-by: Christoph Lameter <cl@xxxxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Bart Van Assche <bvanassche@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/memory_hotplug.h | 6 ++++++
mm/memory_hotplug.c | 4 ++++
2 files changed, 10 insertions(+)
diff -puN include/linux/memory_hotplug.h~mm-memory_hotplugc-online_pages-add-memory-hotplug-locking include/linux/memory_hotplug.h
--- a/include/linux/memory_hotplug.h~mm-memory_hotplugc-online_pages-add-memory-hotplug-locking
+++ a/include/linux/memory_hotplug.h
@@ -165,6 +165,12 @@ extern void register_page_bootmem_info_n
extern void put_page_bootmem(struct page *page);
#endif
+/*
+ * Lock for memory hotplug guarantees 1) all callbacks for memory hotplug
+ * notifier will be called under this. 2) offline/online/add/remove memory
+ * will not run simultaneously.
+ */
+
void lock_memory_hotplug(void);
void unlock_memory_hotplug(void);
diff -puN mm/memory_hotplug.c~mm-memory_hotplugc-online_pages-add-memory-hotplug-locking mm/memory_hotplug.c
--- a/mm/memory_hotplug.c~mm-memory_hotplugc-online_pages-add-memory-hotplug-locking
+++ a/mm/memory_hotplug.c
@@ -409,6 +409,7 @@ int online_pages(unsigned long pfn, unsi
int ret;
struct memory_notify arg;
+ lock_memory_hotplug();
arg.start_pfn = pfn;
arg.nr_pages = nr_pages;
arg.status_change_nid = -1;
@@ -421,6 +422,7 @@ int online_pages(unsigned long pfn, unsi
ret = notifier_to_errno(ret);
if (ret) {
memory_notify(MEM_CANCEL_ONLINE, &arg);
+ unlock_memory_hotplug();
return ret;
}
/*
@@ -445,6 +447,7 @@ int online_pages(unsigned long pfn, unsi
printk(KERN_DEBUG "online_pages %lx at %lx failed\n",
nr_pages, pfn);
memory_notify(MEM_CANCEL_ONLINE, &arg);
+ unlock_memory_hotplug();
return ret;
}
@@ -467,6 +470,7 @@ int online_pages(unsigned long pfn, unsi
if (onlined_pages)
memory_notify(MEM_ONLINE, &arg);
+ unlock_memory_hotplug();
return 0;
}
_
Patches currently in -mm which might be from kamezawa.hiroyu@xxxxxxxxxxxxxx are
mm-vmstat-use-a-single-setter-function-and-callback-for-adjusting-percpu-thresholds.patch
mm-vmstat-use-a-single-setter-function-and-callback-for-adjusting-percpu-thresholds-update.patch
mm-vmstat-use-a-single-setter-function-and-callback-for-adjusting-percpu-thresholds-fix-set_pgdat_percpu_threshold-dont-use-for_each_online_cpu.patch
oom-allow-a-non-cap_sys_resource-proces-to-oom_score_adj-down.patch
mm-kswapd-stop-high-order-balancing-when-any-suitable-zone-is-balanced.patch
mm-kswapd-keep-kswapd-awake-for-high-order-allocations-until-a-percentage-of-the-node-is-balanced.patch
mm-kswapd-use-the-order-that-kswapd-was-reclaiming-at-for-sleeping_prematurely.patch
mm-kswapd-reset-kswapd_max_order-and-classzone_idx-after-reading.patch
mm-kswapd-treat-zone-all_unreclaimable-in-sleeping_prematurely-similar-to-balance_pgdat.patch
mm-kswapd-use-the-classzone-idx-that-kswapd-was-using-for-sleeping_prematurely.patch
mm-set-correct-numa_zonelist_order-string-when-configured-on-the-kernel-command-line.patch
thp-compound_trans_order-fix.patch
mm-migration-use-rcu_dereference_protected-when-dereferencing-the-radix-tree-slot-during-file-page-migration.patch
mm-memory_hotplugc-online_pages-add-memory-hotplug-locking.patch
memcg-add-page_cgroup-flags-for-dirty-page-tracking.patch
memcg-document-cgroup-dirty-memory-interfaces.patch
memcg-document-cgroup-dirty-memory-interfaces-fix.patch
memcg-create-extensible-page-stat-update-routines.patch
memcg-add-lock-to-synchronize-page-accounting-and-migration.patch
memcg-fix-unit-mismatch-in-memcg-oom-limit-calculation.patch
memcg-remove-unnecessary-return-from-void-returning-mem_cgroup_del_lru_list.patch
memcg-use-zalloc-rather-than-mallocmemset.patch
memcg-fix-memory-migration-of-shmem-swapcache.patch
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