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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id E7521C43334 for ; Thu, 2 Jun 2022 18:22:52 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 845406B0073; Thu, 2 Jun 2022 14:22:52 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 7F02A6B0080; Thu, 2 Jun 2022 14:22:52 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 704B46B0081; Thu, 2 Jun 2022 14:22:52 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id 615076B0073 for ; Thu, 2 Jun 2022 14:22:52 -0400 (EDT) Received: from smtpin07.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay12.hostedemail.com (Postfix) with ESMTP id 3AFCB121344 for ; Thu, 2 Jun 2022 18:22:52 +0000 (UTC) X-FDA: 79534116984.07.6250C93 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by imf26.hostedemail.com (Postfix) with ESMTP id 3AA2014005B for ; Thu, 2 Jun 2022 18:22:47 +0000 (UTC) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 868DE616BF; Thu, 2 Jun 2022 18:22:50 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 821D8C385A5; Thu, 2 Jun 2022 18:22:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1654194169; bh=yLIgRtsAt61/ViRtkwjVef0xtUPPspKdkzpb2tdOEVs=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=GjA7Ik2eCW0cWALGPFnWPlXPFx2lTWwc2ejH6HhltRQRy/wxigYzjNTQ7orB7IlJn cC/CKCQeYm0lujlBzZ+B3gOsq3LxzRAdFVp1JIaOuDyxoOVErbfy5HM3sQkv6FIn/d gUm7PXybxWns81FWxECQjAL/Fpr9rVJ9C87hWvJ4= Date: Thu, 2 Jun 2022 11:22:48 -0700 From: Andrew Morton To: Yu Kuai Cc: , , , , , , Subject: Re: [PATCH -next] mm/filemap: fix that first page is not mark accessed in filemap_read() Message-Id: <20220602112248.1e3cd871a87fe9df1ca13f08@linux-foundation.org> In-Reply-To: <20220602082129.2805890-1-yukuai3@huawei.com> References: <20220602082129.2805890-1-yukuai3@huawei.com> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 3AA2014005B X-Stat-Signature: qd4aff1n3n9755skmq93wwge5n6gghg4 X-Rspam-User: Authentication-Results: imf26.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=GjA7Ik2e; spf=pass (imf26.hostedemail.com: domain of akpm@linux-foundation.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org; dmarc=none X-HE-Tag: 1654194167-482366 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, 2 Jun 2022 16:21:29 +0800 Yu Kuai wrote: > In filemap_read(), 'ra->prev_pos' is set to 'iocb->ki_pos + copied', > while it should be 'iocb->ki_ops'. For consequence, > folio_mark_accessed() will not be called for 'fbatch.folios[0]' since > 'iocb->ki_pos' is always equal to 'ra->prev_pos'. > > ... > > --- a/mm/filemap.c > +++ b/mm/filemap.c > @@ -2728,10 +2728,11 @@ ssize_t filemap_read(struct kiocb *iocb, struct iov_iter *iter, > flush_dcache_folio(folio); > > copied = copy_folio_to_iter(folio, offset, bytes, iter); > - > - already_read += copied; > - iocb->ki_pos += copied; > - ra->prev_pos = iocb->ki_pos; > + if (copied) { > + ra->prev_pos = iocb->ki_pos; > + already_read += copied; > + iocb->ki_pos += copied; > + } > > if (copied < bytes) { > error = -EFAULT; It seems tidier, but does it matter? If copied==0 we're going to break out and return -EFAULT anyway?