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=-16.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 3BD1DC43460 for ; Mon, 17 May 2021 06:44:36 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id CEA6861222 for ; Mon, 17 May 2021 06:44:35 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CEA6861222 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 6B3296B0036; Mon, 17 May 2021 02:44:35 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 689FA6B0070; Mon, 17 May 2021 02:44:35 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 52B5C6B0071; Mon, 17 May 2021 02:44:35 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0139.hostedemail.com [216.40.44.139]) by kanga.kvack.org (Postfix) with ESMTP id 21B646B0036 for ; Mon, 17 May 2021 02:44:35 -0400 (EDT) Received: from smtpin07.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id BEEC66D65 for ; Mon, 17 May 2021 06:44:34 +0000 (UTC) X-FDA: 78149784468.07.424D09F Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf25.hostedemail.com (Postfix) with ESMTP id 0D9F76000111 for ; Mon, 17 May 2021 06:44:31 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id 6480561241; Mon, 17 May 2021 06:44:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1621233873; bh=T9ZQTSZNUgScjjscUGeUbBchpa/DhX2GQEJ7bdtNzBA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ObtoQIRNWxRguTgHnVfCVu7AKOk3Iw7wF8fqwXQR/rPc0nGO5+s6yg3D0U2vm3aT7 XNy69ebRGLwVhrw9OWXJc0sPi4ha8KBWwsP8N1fFaZRMnjxf53cZ73/ij16KbQsw7l qZLKTKAD/Y2WbMMKFozt11phpM+mqIuImeNnmHBOt55cZXZ/9Ln9YjnZfxM0uI2IHE dpF29d0QZOKhpr05D/dOT1ho7DzutPkIeIrZw0sR6BleZy18PGvtN0RG57oGn8V+uR Pyn+1fmOk1a++kAEZEhqjiQGECWaRP/TYpyn+ShcWYJbNSGpgi59bEt9AD/EQ3j0cB RDY5jYDTRUnqQ== Date: Mon, 17 May 2021 09:44:21 +0300 From: Mike Rapoport To: David Hildenbrand Cc: linux-kernel@vger.kernel.org, Andrew Morton , "Michael S. Tsirkin" , Jason Wang , Alexey Dobriyan , "Matthew Wilcox (Oracle)" , Oscar Salvador , Michal Hocko , Roman Gushchin , Alex Shi , Steven Price , Mike Kravetz , Aili Yao , Jiri Bohac , "K. Y. Srinivasan" , Haiyang Zhang , Stephen Hemminger , Wei Liu , Naoya Horiguchi , linux-hyperv@vger.kernel.org, virtualization@lists.linux-foundation.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v2 6/6] fs/proc/kcore: use page_offline_(freeze|thaw) Message-ID: References: <20210514172247.176750-1-david@redhat.com> <20210514172247.176750-7-david@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210514172247.176750-7-david@redhat.com> Authentication-Results: imf25.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=ObtoQIRN; dmarc=pass (policy=none) header.from=kernel.org; spf=pass (imf25.hostedemail.com: domain of rppt@kernel.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=rppt@kernel.org X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 0D9F76000111 X-Stat-Signature: uybf4fg5knujmwi57eyp8pitjcszgmqi X-HE-Tag: 1621233871-664606 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 Fri, May 14, 2021 at 07:22:47PM +0200, David Hildenbrand wrote: > Let's properly synchronize with drivers that set PageOffline(). > Unfreeze/thaw every now and then, so drivers that want to set PageOffline() > can make progress. > > Signed-off-by: David Hildenbrand Acked-by: Mike Rapoport > --- > fs/proc/kcore.c | 13 +++++++++++++ > 1 file changed, 13 insertions(+) > > diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c > index 92ff1e4436cb..982e694aae77 100644 > --- a/fs/proc/kcore.c > +++ b/fs/proc/kcore.c > @@ -313,6 +313,7 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos) > { > char *buf = file->private_data; > size_t phdrs_offset, notes_offset, data_offset; > + size_t page_offline_frozen = 1; > size_t phdrs_len, notes_len; > struct kcore_list *m; > size_t tsz; > @@ -322,6 +323,11 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos) > int ret = 0; > > down_read(&kclist_lock); > + /* > + * Don't race against drivers that set PageOffline() and expect no > + * further page access. > + */ > + page_offline_freeze(); > > get_kcore_size(&nphdr, &phdrs_len, ¬es_len, &data_offset); > phdrs_offset = sizeof(struct elfhdr); > @@ -480,6 +486,12 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos) > } > } > > + if (page_offline_frozen++ % MAX_ORDER_NR_PAGES == 0) { > + page_offline_thaw(); > + cond_resched(); > + page_offline_freeze(); > + } > + > if (&m->list == &kclist_head) { > if (clear_user(buffer, tsz)) { > ret = -EFAULT; > @@ -565,6 +577,7 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos) > } > > out: > + page_offline_thaw(); > up_read(&kclist_lock); > if (ret) > return ret; > -- > 2.31.1 > -- Sincerely yours, Mike.