From 9f9f1acd713d69fae2af286fbeedc6c8963411c6 Mon Sep 17 00:00:00 2001 From: Konstantin Khlebnikov Date: Fri, 20 Jan 2012 14:34:24 -0800 Subject: mm: fix rss count leakage during migration Memory migration fills a pte with a migration entry and it doesn't update the rss counters. Then it replaces the migration entry with the new page (or the old one if migration failed). But between these two passes this pte can be unmaped, or a task can fork a child and it will get a copy of this migration entry. Nobody accounts for this in the rss counters. This patch properly adjust rss counters for migration entries in zap_pte_range() and copy_one_pte(). Thus we avoid extra atomic operations on the migration fast-path. Signed-off-by: Konstantin Khlebnikov Cc: Hugh Dickins Cc: KAMEZAWA Hiroyuki Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/memory.c | 37 ++++++++++++++++++++++++++++--------- 1 file changed, 28 insertions(+), 9 deletions(-) (limited to 'mm') diff --git a/mm/memory.c b/mm/memory.c index 5e30583c2605..fa2f04e0337c 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -878,15 +878,24 @@ copy_one_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm, } if (likely(!non_swap_entry(entry))) rss[MM_SWAPENTS]++; - else if (is_write_migration_entry(entry) && - is_cow_mapping(vm_flags)) { - /* - * COW mappings require pages in both parent - * and child to be set to read. - */ - make_migration_entry_read(&entry); - pte = swp_entry_to_pte(entry); - set_pte_at(src_mm, addr, src_pte, pte); + else if (is_migration_entry(entry)) { + page = migration_entry_to_page(entry); + + if (PageAnon(page)) + rss[MM_ANONPAGES]++; + else + rss[MM_FILEPAGES]++; + + if (is_write_migration_entry(entry) && + is_cow_mapping(vm_flags)) { + /* + * COW mappings require pages in both + * parent and child to be set to read. + */ + make_migration_entry_read(&entry); + pte = swp_entry_to_pte(entry); + set_pte_at(src_mm, addr, src_pte, pte); + } } } goto out_set_pte; @@ -1191,6 +1200,16 @@ again: if (!non_swap_entry(entry)) rss[MM_SWAPENTS]--; + else if (is_migration_entry(entry)) { + struct page *page; + + page = migration_entry_to_page(entry); + + if (PageAnon(page)) + rss[MM_ANONPAGES]--; + else + rss[MM_FILEPAGES]--; + } if (unlikely(!free_swap_and_cache(entry))) print_bad_pte(vma, addr, ptent, NULL); } -- cgit v1.2.2