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 --- fs/file_table.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) (limited to 'fs/file_table.c') diff --git a/fs/file_table.c b/fs/file_table.c index e49af4caf15d..b6e9587f05c7 100644 --- a/fs/file_table.c +++ b/fs/file_table.c @@ -380,10 +380,11 @@ void __init files_init(void) void __init files_maxfiles_init(void) { unsigned long n; - unsigned long memreserve = (totalram_pages - nr_free_pages()) * 3/2; + unsigned long nr_pages = totalram_pages; + unsigned long memreserve = (nr_pages - nr_free_pages()) * 3/2; - memreserve = min(memreserve, totalram_pages - 1); - n = ((totalram_pages - memreserve) * (PAGE_SIZE / 1024)) / 10; + memreserve = min(memreserve, nr_pages - 1); + n = ((nr_pages - memreserve) * (PAGE_SIZE / 1024)) / 10; files_stat.max_files = max_t(unsigned long, n, NR_FILE); } -- cgit v1.2.3-59-g8ed1b