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mm/memory_hotplug.c: clean up node_states_check_changes_offline()
This patch, as the previous one, gets rid of the wrong if statements. While at it, I realized that the comments are sometimes very confusing, to say the least, and wrong. For example: ___ zone_last = ZONE_MOVABLE; /* * check whether node_states[N_HIGH_MEMORY] will be changed * If we try to offline the last present @nr_pages from the node, * we can determind we will need to clear the node from * node_states[N_HIGH_MEMORY]. */ 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; ___ In case the node gets empry, it must be removed from N_MEMORY. We already check N_HIGH_MEMORY a bit above within the CONFIG_HIGHMEM ifdef code. Not to say that status_change_nid is for N_MEMORY, and not for N_HIGH_MEMORY. So I re-wrote some of the comments to what I think is better. [osalvador@suse.de: address feedback from Pavel] Link: http://lkml.kernel.org/r/20180921132634.10103-5-osalvador@techadventures.net Link: http://lkml.kernel.org/r/20180919100819.25518-6-osalvador@techadventures.net Signed-off-by: Oscar Salvador <osalvador@suse.de> Reviewed-by: Pavel Tatashin <pavel.tatashin@microsoft.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Dan Williams <dan.j.williams@intel.com> Cc: David Hildenbrand <david@redhat.com> Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com> Cc: <yasu.isimatu@gmail.com> Cc: Mathieu Malaterre <malat@debian.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -1463,75 +1463,53 @@ static void node_states_check_changes_offline(unsigned long nr_pages,
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{
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struct pglist_data *pgdat = zone->zone_pgdat;
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unsigned long present_pages = 0;
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enum zone_type zt, zone_last = ZONE_NORMAL;
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enum zone_type zt;
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arg->status_change_nid = -1;
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arg->status_change_nid_normal = -1;
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arg->status_change_nid_high = -1;
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/*
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* If we have HIGHMEM or movable node, node_states[N_NORMAL_MEMORY]
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* contains nodes which have zones of 0...ZONE_NORMAL,
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* set zone_last to ZONE_NORMAL.
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*
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* If we don't have HIGHMEM nor movable node,
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* node_states[N_NORMAL_MEMORY] contains nodes which have zones of
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* 0...ZONE_MOVABLE, set zone_last to ZONE_MOVABLE.
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* Check whether node_states[N_NORMAL_MEMORY] will be changed.
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* If the memory to be offline is within the range
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* [0..ZONE_NORMAL], and it is the last present memory there,
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* the zones in that range will become empty after the offlining,
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* thus we can determine that we need to clear the node from
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* node_states[N_NORMAL_MEMORY].
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*/
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if (N_MEMORY == N_NORMAL_MEMORY)
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zone_last = ZONE_MOVABLE;
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/*
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* check whether node_states[N_NORMAL_MEMORY] will be changed.
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* If the memory to be offline is in a zone of 0...zone_last,
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* and it is the last present memory, 0...zone_last will
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* become empty after offline , thus we can determind we will
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* need to clear the node from node_states[N_NORMAL_MEMORY].
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*/
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for (zt = 0; zt <= zone_last; zt++)
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for (zt = 0; zt <= ZONE_NORMAL; zt++)
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present_pages += pgdat->node_zones[zt].present_pages;
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if (zone_idx(zone) <= zone_last && nr_pages >= present_pages)
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if (zone_idx(zone) <= ZONE_NORMAL && nr_pages >= present_pages)
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arg->status_change_nid_normal = zone_to_nid(zone);
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else
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arg->status_change_nid_normal = -1;
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#ifdef CONFIG_HIGHMEM
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/*
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* If we have movable node, node_states[N_HIGH_MEMORY]
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* contains nodes which have zones of 0...ZONE_HIGHMEM,
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* set zone_last to ZONE_HIGHMEM.
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*
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* If we don't have movable node, node_states[N_NORMAL_MEMORY]
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* contains nodes which have zones of 0...ZONE_MOVABLE,
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* set zone_last to ZONE_MOVABLE.
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* node_states[N_HIGH_MEMORY] contains nodes which
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* have normal memory or high memory.
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* Here we add the present_pages belonging to ZONE_HIGHMEM.
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* If the zone is within the range of [0..ZONE_HIGHMEM), and
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* we determine that the zones in that range become empty,
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* we need to clear the node for N_HIGH_MEMORY.
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*/
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zone_last = ZONE_HIGHMEM;
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if (N_MEMORY == N_HIGH_MEMORY)
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zone_last = ZONE_MOVABLE;
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for (; zt <= zone_last; zt++)
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present_pages += pgdat->node_zones[zt].present_pages;
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if (zone_idx(zone) <= zone_last && nr_pages >= present_pages)
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present_pages += pgdat->node_zones[ZONE_HIGHMEM].present_pages;
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if (zone_idx(zone) <= ZONE_HIGHMEM && nr_pages >= present_pages)
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arg->status_change_nid_high = zone_to_nid(zone);
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else
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arg->status_change_nid_high = -1;
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#else
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arg->status_change_nid_high = arg->status_change_nid_normal;
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#endif
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/*
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* node_states[N_HIGH_MEMORY] contains nodes which have 0...ZONE_MOVABLE
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* We have accounted the pages from [0..ZONE_NORMAL), and
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* in case of CONFIG_HIGHMEM the pages from ZONE_HIGHMEM
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* as well.
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* Here we count the possible pages from ZONE_MOVABLE.
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* If after having accounted all the pages, we see that the nr_pages
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* to be offlined is over or equal to the accounted pages,
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* we know that the node will become empty, and so, we can clear
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* it for N_MEMORY as well.
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*/
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zone_last = ZONE_MOVABLE;
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present_pages += pgdat->node_zones[ZONE_MOVABLE].present_pages;
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/*
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* check whether node_states[N_HIGH_MEMORY] will be changed
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* If we try to offline the last present @nr_pages from the node,
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* we can determind we will need to clear the node from
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* node_states[N_HIGH_MEMORY].
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*/
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for (; zt <= zone_last; zt++)
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present_pages += pgdat->node_zones[zt].present_pages;
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if (nr_pages >= present_pages)
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arg->status_change_nid = zone_to_nid(zone);
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else
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arg->status_change_nid = -1;
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}
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static void node_states_clear_node(int node, struct memory_notify *arg)
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