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    SubjectRe: [V4 PATCH 02/26] memory_hotplug: fix missing nodemask management
    At 09/10/2012 04:58 PM, Lai Jiangshan Wrote:
    > Currently memory_hotplug only manages the node_states[N_HIGH_MEMORY],
    > it forgot to manage node_states[N_NORMAL_MEMORY]. fix it.
    >
    > Add check_nodemasks_changes_online() and check_nodemasks_changes_offline
    > to detect do node_states[N_HIGH_MEMORY] and node_states[N_NORMAL_MEMORY]
    > are changed while hotplug.
    >
    > 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.
    >
    > Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
    > ---
    > 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 1ac7f6e..6b9202b 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 3ad25f9..8c3bcf6 100644
    > --- a/mm/memory_hotplug.c
    > +++ b/mm/memory_hotplug.c
    > @@ -456,6 +456,34 @@ 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;
    > +
    > + 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;
    > +
    > + 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)
    > +{
    > + 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)
    > {
    > @@ -467,13 +495,18 @@ 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.
    > + */

    If we hotremove memory, we remove the section without memory_block->state_mutex,
    it is fixed by the following patch:
    https://lkml.org/lkml/2012/9/5/162

    Thanks
    Wen Congyang

    > + 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);
    > @@ -483,12 +516,6 @@ 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.
    > @@ -513,7 +540,7 @@ 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
    > @@ -866,6 +893,44 @@ 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)
    > +{
    > + 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;
    > +
    > + 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;
    > +
    > + 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)
    > {
    > @@ -899,9 +964,7 @@ 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);
    > @@ -969,10 +1032,9 @@ 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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