From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 54EB4CA9EBC for ; Mon, 28 Oct 2019 09:59:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 297D3208C0 for ; Mon, 28 Oct 2019 09:59:41 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=yandex-team.ru header.i=@yandex-team.ru header.b="jUI0uMDZ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388108AbfJ1J7i (ORCPT ); Mon, 28 Oct 2019 05:59:38 -0400 Received: from forwardcorp1j.mail.yandex.net ([5.45.199.163]:58310 "EHLO forwardcorp1j.mail.yandex.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732833AbfJ1J7i (ORCPT ); Mon, 28 Oct 2019 05:59:38 -0400 Received: from mxbackcorp1o.mail.yandex.net (mxbackcorp1o.mail.yandex.net [IPv6:2a02:6b8:0:1a2d::301]) by forwardcorp1j.mail.yandex.net (Yandex) with ESMTP id 2EB892E14B4; Mon, 28 Oct 2019 12:59:36 +0300 (MSK) Received: from sas2-62907d92d1d8.qloud-c.yandex.net (sas2-62907d92d1d8.qloud-c.yandex.net [2a02:6b8:c08:b895:0:640:6290:7d92]) by mxbackcorp1o.mail.yandex.net (nwsmtp/Yandex) with ESMTP id 1MMz6MIGFv-xZl450v5; Mon, 28 Oct 2019 12:59:36 +0300 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yandex-team.ru; s=default; t=1572256776; bh=qKbZKUhxXAikWcE9+erLx+dDD7QZSmSl+7ceSjN66mg=; h=Message-ID:Date:To:From:Subject:Cc; b=jUI0uMDZxH7owFu2UKMQ7KRNEqVM5Fbnu6SXj3wPdJctmvDEmSPHmXmo6rltQ5bhe 694+7ixWanoElRRUS6lOxjlbB4kBGFgbbUylTyyYmSJ2L0Qk/29Wqo1A4QYeNHpyPk Zu7c2Lxu3D39+XN8kJyMx7YY88JeIlPMHJ3VhZak= Authentication-Results: mxbackcorp1o.mail.yandex.net; dkim=pass header.i=@yandex-team.ru Received: from dynamic-red.dhcp.yndx.net (dynamic-red.dhcp.yndx.net [2a02:6b8:0:40c:148a:8f3:5b61:9f4]) by sas2-62907d92d1d8.qloud-c.yandex.net (nwsmtp/Yandex) with ESMTPSA id brINrBKnHB-xZV0tdEe; Mon, 28 Oct 2019 12:59:35 +0300 (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client certificate not present) Subject: [PATCH] mm/filemap: do not allocate cache pages beyond end of file at read From: Konstantin Khlebnikov To: linux-mm@kvack.org, Andrew Morton , linux-kernel@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org, Linus Torvalds , Alexander Viro , Johannes Weiner Date: Mon, 28 Oct 2019 12:59:34 +0300 Message-ID: <157225677483.3442.4227193290486305330.stgit@buzz> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Page cache could contain pages beyond end of file during write or if read races with truncate. But generic_file_buffered_read() always allocates unneeded pages beyond eof if somebody reads here and one extra page at the end if file size is page-aligned. Function generic_file_buffered_read() calls page_cache_sync_readahead() if page not found in cache and then do another lookup. Readahead checks file size in __do_page_cache_readahead() before allocating pages. After that generic_file_buffered_read() falls back to slow path and allocates page for ->readpage() without checking file size. This patch checks file size before allocating page for ->readpage(). Signed-off-by: Konstantin Khlebnikov --- mm/filemap.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/mm/filemap.c b/mm/filemap.c index 85b7d087eb45..92abf5f348a9 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2225,6 +2225,10 @@ static ssize_t generic_file_buffered_read(struct kiocb *iocb, goto out; no_cached_page: + /* Do not allocate cache pages beyond end of file. */ + if (((loff_t)index << PAGE_SHIFT) >= i_size_read(inode)) + goto out; + /* * Ok, it wasn't cached, so we need to create a new * page..