Re: [PATCH 1/3] memory_hotplug: fix stale node_states[N_NORMAL_MEMORY]
From: KOSAKI Motohiro <hidden>
Date: 2012-09-27 22:03:37
Also in:
lkml
(9/27/12 2:47 AM), Lai Jiangshan wrote:
Currently memory_hotplug only manages the node_states[N_HIGH_MEMORY], it forgets to manage node_states[N_NORMAL_MEMORY]. it causes node_states[N_NORMAL_MEMORY] becomes stale.
What's mean 'stale'? I guess : Currently memory_hotplug doesn't turn on/off node_states[N_NORMAL_MEMORY] and : then it will be invalid if the platform has highmem. Luckily, almost memory : hotplug aware platform don't have highmem, but are not all. right? I supporse this patch only meaningful on ARM platform practically.
We add check_nodemasks_changes_online() and check_nodemasks_changes_offline() to detect whether node_states[N_HIGH_MEMORY] and node_states[N_NORMAL_MEMORY] are changed while hotpluging.
Also add @status_change_nid_normal to struct memory_notify, thus the memory hotplug callbacks know whether the node_states[N_NORMAL_MEMORY] are changed.
status_change_nid_normal is very ugly to me. When status_change_nid and status_change_nid_normal has positive value, they are always the same. nid and flags value are more natual to me.
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Signed-off-by: Lai Jiangshan <redacted> --- Documentation/memory-hotplug.txt | 5 ++- include/linux/memory.h | 1 + mm/memory_hotplug.c | 94 +++++++++++++++++++++++++++++++------ 3 files changed, 83 insertions(+), 17 deletions(-)diff --git a/Documentation/memory-hotplug.txt b/Documentation/memory-hotplug.txt index 6d0c251..6e6cbc7 100644 --- a/Documentation/memory-hotplug.txt +++ b/Documentation/memory-hotplug.txt@@ -377,15 +377,18 @@ The third argument is passed by pointer of struct memory_notify. struct memory_notify { unsigned long start_pfn; unsigned long nr_pages; + int status_change_nid_normal; int status_change_nid; } start_pfn is start_pfn of online/offline memory. nr_pages is # of pages of online/offline memory. +status_change_nid_normal is set node id when N_NORMAL_MEMORY of nodemask +is (will be) set/clear, if this is -1, then nodemask status is not changed. status_change_nid is set node id when N_HIGH_MEMORY of nodemask is (will be) set/clear. It means a new(memoryless) node gets new memory by online and a node loses all memory. If this is -1, then nodemask status is not changed. -If status_changed_nid >= 0, callback should create/discard structures for the +If status_changed_nid* >= 0, callback should create/discard structures for the node if necessary. --------------diff --git a/include/linux/memory.h b/include/linux/memory.h index ff9a9f8..a09216d 100644 --- a/include/linux/memory.h +++ b/include/linux/memory.h@@ -53,6 +53,7 @@ int arch_get_memory_phys_device(unsigned long start_pfn); struct memory_notify { unsigned long start_pfn; unsigned long nr_pages; + int status_change_nid_normal; int status_change_nid; };diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index 6a5b90d..b62d429b 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c@@ -460,6 +460,34 @@ static int online_pages_range(unsigned long start_pfn, unsigned long nr_pages, return 0; } +static void check_nodemasks_changes_online(unsigned long nr_pages, + struct zone *zone, struct memory_notify *arg) +{ + int nid = zone_to_nid(zone); + enum zone_type zone_last = ZONE_NORMAL; + + if (N_HIGH_MEMORY == N_NORMAL_MEMORY) + zone_last = ZONE_MOVABLE;
This is very strange (or ugly) code. ZONE_MOVABLE don't depend on high mem.
+ + if (zone_idx(zone) <= zone_last && !node_state(nid, N_NORMAL_MEMORY)) + arg->status_change_nid_normal = nid; + else + arg->status_change_nid_normal = -1;
Wrong. The onlined node may only have high mem zone. IOW, think fake numa case etc.
+ + if (!node_state(nid, N_HIGH_MEMORY)) + arg->status_change_nid = nid; + else + arg->status_change_nid = -1; +} + +static void set_nodemasks(int node, struct memory_notify *arg)
Too ugly. just remove this and use node_set_state() directly.
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+{ + if (arg->status_change_nid_normal >= 0) + node_set_state(node, N_NORMAL_MEMORY); + + node_set_state(node, N_HIGH_MEMORY); +} + int __ref online_pages(unsigned long pfn, unsigned long nr_pages) {@@ -471,13 +499,18 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages) struct memory_notify arg; lock_memory_hotplug(); + /* + * This doesn't need a lock to do pfn_to_page(). + * The section can't be removed here because of the + * memory_block->state_mutex. + */
Please explain the intention of this comment. We think lock_memory_hotplug() close a race against memory offline directly.
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+ zone = page_zone(pfn_to_page(pfn)); + arg.start_pfn = pfn; arg.nr_pages = nr_pages; - arg.status_change_nid = -1; + check_nodemasks_changes_online(nr_pages, zone, &arg); nid = page_to_nid(pfn_to_page(pfn)); - if (node_present_pages(nid) == 0) - arg.status_change_nid = nid; ret = memory_notify(MEM_GOING_ONLINE, &arg); ret = notifier_to_errno(ret);@@ -487,12 +520,6 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages) return ret; } /* - * This doesn't need a lock to do pfn_to_page(). - * The section can't be removed here because of the - * memory_block->state_mutex. - */ - zone = page_zone(pfn_to_page(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.@@ -517,7 +544,7 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages) zone->present_pages += onlined_pages; zone->zone_pgdat->node_present_pages += onlined_pages; if (onlined_pages) { - node_set_state(zone_to_nid(zone), N_HIGH_MEMORY); + set_nodemasks(zone_to_nid(zone), &arg); if (need_zonelists_rebuild) build_all_zonelists(NULL, zone); else@@ -870,6 +897,44 @@ check_pages_isolated(unsigned long start_pfn, unsigned long end_pfn) return offlined; } +static void check_nodemasks_changes_offline(unsigned long nr_pages, + struct zone *zone, struct memory_notify *arg) +{
This should remove ugly memory_notify argument and should be fold check_nodemasks_changes_online().
+ struct pglist_data *pgdat = zone->zone_pgdat; + unsigned long present_pages = 0; + enum zone_type zt, zone_last = ZONE_NORMAL; + + if (N_HIGH_MEMORY == N_NORMAL_MEMORY) + zone_last = ZONE_MOVABLE; + + for (zt = 0; zt <= zone_last; zt++) + present_pages += pgdat->node_zones[zt].present_pages; + if (zone_idx(zone) <= zone_last && nr_pages >= present_pages) + arg->status_change_nid_normal = zone_to_nid(zone); + else + arg->status_change_nid_normal = -1;
Wrong. Think, a zone has both normal and highmem zone and when admin only remove highmem area. you should check pfn too.
+
+ zone_last = ZONE_MOVABLE;
+ for (; zt <= zone_last; zt++)
+ present_pages += pgdat->node_zones[zt].present_pages;
+ if (nr_pages >= present_pages)
+ arg->status_change_nid = zone_to_nid(zone);
+ else
+ arg->status_change_nid = -1;
+}
+
+static void clear_nodemasks(int node, struct memory_notify *arg)
+{
+ if (arg->status_change_nid_normal >= 0)
+ node_clear_state(node, N_NORMAL_MEMORY);
+
+ if (N_HIGH_MEMORY == N_NORMAL_MEMORY)
+ return;You should use #ifdef. otherwise we face unreachable statement warning.
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+ + if (arg->status_change_nid >= 0) + node_clear_state(node, N_HIGH_MEMORY); +} + static int __ref offline_pages(unsigned long start_pfn, unsigned long end_pfn, unsigned long timeout) {@@ -903,9 +968,7 @@ static int __ref offline_pages(unsigned long start_pfn, arg.start_pfn = start_pfn; arg.nr_pages = nr_pages; - arg.status_change_nid = -1; - if (nr_pages >= node_present_pages(node)) - arg.status_change_nid = node; + check_nodemasks_changes_offline(nr_pages, zone, &arg); ret = memory_notify(MEM_GOING_OFFLINE, &arg); ret = notifier_to_errno(ret);@@ -973,10 +1036,9 @@ repeat: if (!populated_zone(zone)) zone_pcp_reset(zone); - if (!node_present_pages(node)) { - node_clear_state(node, N_HIGH_MEMORY); + clear_nodemasks(node, &arg); + if (arg.status_change_nid >= 0) kswapd_stop(node); - } vm_total_pages = nr_free_pagecache_pages(); writeback_set_ratelimit();
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