From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965168AbcJXP1a (ORCPT ); Mon, 24 Oct 2016 11:27:30 -0400 Received: from mail-wm0-f67.google.com ([74.125.82.67]:34306 "EHLO mail-wm0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S938455AbcJXP10 (ORCPT ); Mon, 24 Oct 2016 11:27:26 -0400 From: Michal Hocko To: Johannes Weiner Cc: Stable tree , , LKML , Andrew Morton , Miklos Szeredi , Linus Torvalds , Michal Hocko Subject: [Stable 4.4 - NEEDS REVIEW - 3/3] mm: filemap: fix mapping->nrpages double accounting in fuse Date: Mon, 24 Oct 2016 17:26:05 +0200 Message-Id: <20161024152605.11707-4-mhocko@kernel.org> X-Mailer: git-send-email 2.9.3 In-Reply-To: <20161024152605.11707-1-mhocko@kernel.org> References: <20161024152605.11707-1-mhocko@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 c9c19c12f61d..8675ce8a8f87 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -578,7 +578,6 @@ 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