From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f72.google.com (mail-wm0-f72.google.com [74.125.82.72]) by kanga.kvack.org (Postfix) with ESMTP id 1AC9A6B0292 for ; Thu, 1 Jun 2017 05:33:17 -0400 (EDT) Received: by mail-wm0-f72.google.com with SMTP id 139so8672981wmf.5 for ; Thu, 01 Jun 2017 02:33:17 -0700 (PDT) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id f7si33444172wmh.64.2017.06.01.02.33.15 for (version=TLS1 cipher=AES128-SHA bits=128/128); Thu, 01 Jun 2017 02:33:15 -0700 (PDT) From: Jan Kara Subject: [PATCH 05/35] mm: Fix THP handling in invalidate_mapping_pages() Date: Thu, 1 Jun 2017 11:32:15 +0200 Message-Id: <20170601093245.29238-6-jack@suse.cz> In-Reply-To: <20170601093245.29238-1-jack@suse.cz> References: <20170601093245.29238-1-jack@suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: linux-mm@kvack.org Cc: Hugh Dickins , David Howells , linux-afs@lists.infradead.org, Ryusuke Konishi , linux-nilfs@vger.kernel.org, Bob Peterson , cluster-devel@redhat.com, Jaegeuk Kim , linux-f2fs-devel@lists.sourceforge.net, tytso@mit.edu, linux-ext4@vger.kernel.org, Ilya Dryomov , "Yan, Zheng" , ceph-devel@vger.kernel.org, linux-btrfs@vger.kernel.org, David Sterba , "Darrick J . Wong" , linux-xfs@vger.kernel.org, Nadia Yvette Chambers , Jan Kara The condition checking for THP straddling end of invalidated range is wrong - it checks 'index' against 'end' but 'index' has been already advanced to point to the end of THP and thus the condition can never be true. As a result THP straddling 'end' has been fully invalidated. Given the nature of invalidate_mapping_pages(), this could be only performance issue. In fact, we are lucky the condition is wrong because if it was ever true, we'd leave locked page behind. Fix the condition checking for THP straddling 'end' and also properly unlock the page. Also update the comment before the condition to explain why we decide not to invalidate the page as it was not clear to me and I had to ask Kirill. Signed-off-by: Jan Kara --- mm/truncate.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/mm/truncate.c b/mm/truncate.c index 6479ed2afc53..2330223841fb 100644 --- a/mm/truncate.c +++ b/mm/truncate.c @@ -530,9 +530,15 @@ unsigned long invalidate_mapping_pages(struct address_space *mapping, } else if (PageTransHuge(page)) { index += HPAGE_PMD_NR - 1; i += HPAGE_PMD_NR - 1; - /* 'end' is in the middle of THP */ - if (index == round_down(end, HPAGE_PMD_NR)) + /* + * 'end' is in the middle of THP. Don't + * invalidate the page as the part outside of + * 'end' could be still useful. + */ + if (index > end) { + unlock_page(page); continue; + } } ret = invalidate_inode_page(page); -- 2.12.3 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org