Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758516AbcJYHwQ (ORCPT ); Tue, 25 Oct 2016 03:52:16 -0400 Received: from mail-pf0-f194.google.com ([209.85.192.194]:35954 "EHLO mail-pf0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758469AbcJYHwN (ORCPT ); Tue, 25 Oct 2016 03:52:13 -0400 From: Michal Hocko To: Stable tree Cc: Johannes Weiner , , LKML , Andrew Morton , Miklos Szeredi , Linus Torvalds , Michal Hocko Subject: [PATCH stable 4.4 3/4] mm: filemap: fix mapping->nrpages double accounting in fuse Date: Tue, 25 Oct 2016 09:51:47 +0200 Message-Id: <20161025075148.31661-4-mhocko@kernel.org> X-Mailer: git-send-email 2.9.3 In-Reply-To: <20161025075148.31661-1-mhocko@kernel.org> References: <20161025075148.31661-1-mhocko@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1776 Lines: 43 From: Johannes Weiner Commit 3ddf40e8c31964b744ff10abb48c8e36a83ec6e7 upstream. Commit 22f2ac51b6d6 ("mm: workingset: fix crash in shadow node shrinker caused by replace_page_cache_page()") switched replace_page_cache() from raw radix tree operations to page_cache_tree_insert() but didn't take into account that the latter function, unlike the raw radix tree op, handles mapping->nrpages. As a result, that counter is bumped for each page replacement rather than balanced out even. The mapping->nrpages counter is used to skip needless radix tree walks when invalidating, truncating, syncing inodes without pages, as well as statistics for userspace. Since the error is positive, we'll do more page cache tree walks than necessary; we won't miss a necessary one. And we'll report more buffer pages to userspace than there are. The error is limited to fuse inodes. Fixes: 22f2ac51b6d6 ("mm: workingset: fix crash in shadow node shrinker caused by replace_page_cache_page()") Signed-off-by: Johannes Weiner Cc: Andrew Morton Cc: Miklos Szeredi Cc: stable@vger.kernel.org Signed-off-by: Linus Torvalds Signed-off-by: Michal Hocko --- mm/filemap.c | 1 - 1 file changed, 1 deletion(-) diff --git a/mm/filemap.c b/mm/filemap.c index 7ad648c9780c..c588d1222b2a 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -590,7 +590,6 @@ int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask) __delete_from_page_cache(old, NULL, memcg); error = page_cache_tree_insert(mapping, new, NULL); BUG_ON(error); - mapping->nrpages++; /* * hugetlb pages do not participate in page cache accounting. -- 2.9.3