From 66f71da9dd38af17dc17209cdde7987d4679a699 Mon Sep 17 00:00:00 2001 From: Aaron Lu Date: Fri, 28 Dec 2018 00:34:39 -0800 Subject: mm/swap: use nr_node_ids for avail_lists in swap_info_struct Since a2468cc9bfdf ("swap: choose swap device according to numa node"), avail_lists field of swap_info_struct is changed to an array with MAX_NUMNODES elements. This made swap_info_struct size increased to 40KiB and needs an order-4 page to hold it. This is not optimal in that: 1 Most systems have way less than MAX_NUMNODES(1024) nodes so it is a waste of memory; 2 It could cause swapon failure if the swap device is swapped on after system has been running for a while, due to no order-4 page is available as pointed out by Vasily Averin. Solve the above two issues by using nr_node_ids(which is the actual possible node number the running system has) for avail_lists instead of MAX_NUMNODES. nr_node_ids is unknown at compile time so can't be directly used when declaring this array. What I did here is to declare avail_lists as zero element array and allocate space for it when allocating space for swap_info_struct. The reason why keep using array but not pointer is plist_for_each_entry needs the field to be part of the struct, so pointer will not work. This patch is on top of Vasily Averin's fix commit. I think the use of kvzalloc for swap_info_struct is still needed in case nr_node_ids is really big on some systems. Link: http://lkml.kernel.org/r/20181115083847.GA11129@intel.com Signed-off-by: Aaron Lu Reviewed-by: Andrew Morton Acked-by: Michal Hocko Cc: Vasily Averin Cc: Huang Ying Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/swapfile.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'mm/swapfile.c') diff --git a/mm/swapfile.c b/mm/swapfile.c index 8688ae65ef58..6e06821623f6 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -2812,8 +2812,9 @@ static struct swap_info_struct *alloc_swap_info(void) struct swap_info_struct *p; unsigned int type; int i; + int size = sizeof(*p) + nr_node_ids * sizeof(struct plist_node); - p = kvzalloc(sizeof(*p), GFP_KERNEL); + p = kvzalloc(size, GFP_KERNEL); if (!p) return ERR_PTR(-ENOMEM); -- cgit v1.2.3-59-g8ed1b