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authorOscar Salvador2018-10-26 15:07:38 -0700
committerLinus Torvalds2018-10-26 16:26:33 -0700
commit86b27beae59685a42f81bcda9d502b5aebddfab8 (patch)
tree159912a77ae6415524c624b5e31e98a0e8ee9fe0
parent8efe33f40f3e69ac6069ed46666d2d527ddc2c04 (diff)
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>
-rw-r--r--mm/memory_hotplug.c80
1 files changed, 29 insertions, 51 deletions
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index eadd149eb7bc..7e6509a53d79 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1463,75 +1463,53 @@ static void node_states_check_changes_offline(unsigned long nr_pages,
{
struct pglist_data *pgdat = zone->zone_pgdat;
unsigned long present_pages = 0;
- enum zone_type zt, zone_last = ZONE_NORMAL;
+ enum zone_type zt;
- /*
- * If we have HIGHMEM or movable node, node_states[N_NORMAL_MEMORY]
- * contains nodes which have zones of 0...ZONE_NORMAL,
- * set zone_last to ZONE_NORMAL.
- *
- * If we don't have HIGHMEM nor movable node,
- * node_states[N_NORMAL_MEMORY] contains nodes which have zones of
- * 0...ZONE_MOVABLE, set zone_last to ZONE_MOVABLE.
- */
- if (N_MEMORY == N_NORMAL_MEMORY)
- zone_last = ZONE_MOVABLE;
+ arg->status_change_nid = -1;
+ arg->status_change_nid_normal = -1;
+ arg->status_change_nid_high = -1;
/*
- * check whether node_states[N_NORMAL_MEMORY] will be changed.
- * If the memory to be offline is in a zone of 0...zone_last,
- * and it is the last present memory, 0...zone_last will
- * become empty after offline , thus we can determind we will
- * need to clear the node from node_states[N_NORMAL_MEMORY].
+ * Check whether node_states[N_NORMAL_MEMORY] will be changed.
+ * If the memory to be offline is within the range
+ * [0..ZONE_NORMAL], and it is the last present memory there,
+ * the zones in that range will become empty after the offlining,
+ * thus we can determine that we need to clear the node from
+ * node_states[N_NORMAL_MEMORY].
*/
- for (zt = 0; zt <= zone_last; zt++)
+ for (zt = 0; zt <= ZONE_NORMAL; zt++)
present_pages += pgdat->node_zones[zt].present_pages;
- if (zone_idx(zone) <= zone_last && nr_pages >= present_pages)
+ if (zone_idx(zone) <= ZONE_NORMAL && nr_pages >= present_pages)
arg->status_change_nid_normal = zone_to_nid(zone);
- else
- arg->status_change_nid_normal = -1;
#ifdef CONFIG_HIGHMEM
/*
- * If we have movable node, node_states[N_HIGH_MEMORY]
- * contains nodes which have zones of 0...ZONE_HIGHMEM,
- * set zone_last to ZONE_HIGHMEM.
- *
- * If we don't have movable node, node_states[N_NORMAL_MEMORY]
- * contains nodes which have zones of 0...ZONE_MOVABLE,
- * set zone_last to ZONE_MOVABLE.
+ * node_states[N_HIGH_MEMORY] contains nodes which
+ * have normal memory or high memory.
+ * Here we add the present_pages belonging to ZONE_HIGHMEM.
+ * If the zone is within the range of [0..ZONE_HIGHMEM), and
+ * we determine that the zones in that range become empty,
+ * we need to clear the node for N_HIGH_MEMORY.
*/
- zone_last = ZONE_HIGHMEM;
- if (N_MEMORY == N_HIGH_MEMORY)
- zone_last = ZONE_MOVABLE;
-
- for (; zt <= zone_last; zt++)
- present_pages += pgdat->node_zones[zt].present_pages;
- if (zone_idx(zone) <= zone_last && nr_pages >= present_pages)
+ present_pages += pgdat->node_zones[ZONE_HIGHMEM].present_pages;
+ if (zone_idx(zone) <= ZONE_HIGHMEM && nr_pages >= present_pages)
arg->status_change_nid_high = zone_to_nid(zone);
- else
- arg->status_change_nid_high = -1;
-#else
- arg->status_change_nid_high = arg->status_change_nid_normal;
#endif
/*
- * node_states[N_HIGH_MEMORY] contains nodes which have 0...ZONE_MOVABLE
+ * We have accounted the pages from [0..ZONE_NORMAL), and
+ * in case of CONFIG_HIGHMEM the pages from ZONE_HIGHMEM
+ * as well.
+ * Here we count the possible pages from ZONE_MOVABLE.
+ * If after having accounted all the pages, we see that the nr_pages
+ * to be offlined is over or equal to the accounted pages,
+ * we know that the node will become empty, and so, we can clear
+ * it for N_MEMORY as well.
*/
- zone_last = ZONE_MOVABLE;
+ present_pages += pgdat->node_zones[ZONE_MOVABLE].present_pages;
- /*
- * 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;
}
static void node_states_clear_node(int node, struct memory_notify *arg)