From 3d6357de8aa09e1966770dc1171c72679946464f Mon Sep 17 00:00:00 2001 From: Arun KS Date: Fri, 28 Dec 2018 00:34:20 -0800 Subject: mm: reference totalram_pages and managed_pages once per function Patch series "mm: convert totalram_pages, totalhigh_pages and managed pages to atomic", v5. This series converts totalram_pages, totalhigh_pages and zone->managed_pages to atomic variables. totalram_pages, zone->managed_pages and totalhigh_pages updates are protected by managed_page_count_lock, but readers never care about it. Convert these variables to atomic to avoid readers potentially seeing a store tear. Main motivation was that managed_page_count_lock handling was complicating things. It was discussed in length here, https://lore.kernel.org/patchwork/patch/995739/#1181785 It seemes better to remove the lock and convert variables to atomic. With the change, preventing poteintial store-to-read tearing comes as a bonus. This patch (of 4): This is in preparation to a later patch which converts totalram_pages and zone->managed_pages to atomic variables. Please note that re-reading the value might lead to a different value and as such it could lead to unexpected behavior. There are no known bugs as a result of the current code but it is better to prevent from them in principle. Link: http://lkml.kernel.org/r/1542090790-21750-2-git-send-email-arunks@codeaurora.org Signed-off-by: Arun KS Reviewed-by: Konstantin Khlebnikov Reviewed-by: David Hildenbrand Acked-by: Michal Hocko Acked-by: Vlastimil Babka Reviewed-by: Pavel Tatashin Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- net/netfilter/nf_conntrack_core.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) (limited to 'net/netfilter/nf_conntrack_core.c') diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c index e87c21e47efe..5eb990830348 100644 --- a/net/netfilter/nf_conntrack_core.c +++ b/net/netfilter/nf_conntrack_core.c @@ -2248,6 +2248,7 @@ static __always_inline unsigned int total_extension_size(void) int nf_conntrack_init_start(void) { + unsigned long nr_pages = totalram_pages; int max_factor = 8; int ret = -ENOMEM; int i; @@ -2267,11 +2268,11 @@ int nf_conntrack_init_start(void) * >= 4GB machines have 65536 buckets. */ nf_conntrack_htable_size - = (((totalram_pages << PAGE_SHIFT) / 16384) + = (((nr_pages << PAGE_SHIFT) / 16384) / sizeof(struct hlist_head)); - if (totalram_pages > (4 * (1024 * 1024 * 1024 / PAGE_SIZE))) + if (nr_pages > (4 * (1024 * 1024 * 1024 / PAGE_SIZE))) nf_conntrack_htable_size = 65536; - else if (totalram_pages > (1024 * 1024 * 1024 / PAGE_SIZE)) + else if (nr_pages > (1024 * 1024 * 1024 / PAGE_SIZE)) nf_conntrack_htable_size = 16384; if (nf_conntrack_htable_size < 32) nf_conntrack_htable_size = 32; -- cgit v1.2.3-59-g8ed1b