From: Oscar Salvador Date: Fri, 26 Oct 2018 22:07:38 +0000 (-0700) Subject: mm/memory_hotplug.c: clean up node_states_check_changes_offline() X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=86b27beae59685a42f81bcda9d502b5aebddfab8;p=openwrt%2Fstaging%2Fblogic.git 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 Reviewed-by: Pavel Tatashin Cc: Michal Hocko Cc: Dan Williams Cc: David Hildenbrand Cc: Jonathan Cameron Cc: Cc: Mathieu Malaterre Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- 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)