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 6E591C433EF for ; Tue, 5 Jul 2022 21:18:28 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id B38936B0071; Tue, 5 Jul 2022 17:18:27 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id AE6276B0073; Tue, 5 Jul 2022 17:18:27 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 961BB8E0001; Tue, 5 Jul 2022 17:18:27 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id 86F1C6B0071 for ; Tue, 5 Jul 2022 17:18:27 -0400 (EDT) Received: from smtpin14.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay11.hostedemail.com (Postfix) with ESMTP id 5A17480937 for ; Tue, 5 Jul 2022 21:18:27 +0000 (UTC) X-FDA: 79654309854.14.A03759A Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by imf11.hostedemail.com (Postfix) with ESMTP id 410D740045 for ; Tue, 5 Jul 2022 21:18:23 +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 ams.source.kernel.org (Postfix) with ESMTPS id AD23BB816B8; Tue, 5 Jul 2022 21:18:21 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0628BC341C7; Tue, 5 Jul 2022 21:18:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1657055900; bh=fVMogeJmga7ig2AqAptnQCM6iwfe/+yH29ZcV4O2RYQ=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=QWun8u4MHhoyUSkwZohNmRQwRv7GVlpNYY4UFDCOICjc5tU5TthBsgHZagQmAbVD1 wiE67Q6NMkkaAqzWiUVvGH7ntoTYz1e7WXwoh+M8lHBN8tf/6A+o2eUAi6Cb/J8oDT YHuoio/B5MHzUnlBSZWENzYaWv+N3wQDwVEJ1Atc= Date: Tue, 5 Jul 2022 14:18:19 -0700 From: Andrew Morton To: Muchun Song Cc: willy@infradead.org, jgg@ziepe.ca, jhubbard@nvidia.com, william.kucharski@oracle.com, dan.j.williams@intel.com, jack@suse.cz, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, nvdimm@lists.linux.dev, stable@vger.kernel.org Subject: Re: [PATCH v2] mm: fix missing wake-up event for FSDAX pages Message-Id: <20220705141819.804eb972d43be3434dc70192@linux-foundation.org> In-Reply-To: <20220705123532.283-1-songmuchun@bytedance.com> References: <20220705123532.283-1-songmuchun@bytedance.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 ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1657055903; a=rsa-sha256; cv=none; b=F6GUzaVhRcTpaoUN/ykDDQbg5qfJbRQGIKpyH3K3YIcUkhF7v6lJgGNOgcJiJKmJEeAuzz ddu/vO6F8iRO/Q0hycLhGuoZ3EzwdBrYgqs/jkEEgf+L/GS1yPpzR3/IvpioG0sMNIWDmN OMFzFXAqgQ6hPWL9vjj267HZxzanVdE= ARC-Authentication-Results: i=1; imf11.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=QWun8u4M; dmarc=none; spf=pass (imf11.hostedemail.com: domain of akpm@linux-foundation.org designates 145.40.68.75 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1657055903; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=p1AwLjsCNnrDKgNnXDIqAp5PVMyYDDoAMzJxplJP94Q=; b=l5pYOzInMxs+36abg2YX1IRSXkUsqjZADtW57Y9aSwIeNgrTz7ZirVjfFDkfztq8emaX0+ L6Uf7TkJXRsOhmOWwvwKsW300EpkhEvoJkb+GOVBJeHVddvAbUJ9kKs54BBQNd78kH9XDm 6qUIj3dDSaCv6LSJQsenzEChWzrVH0c= X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 410D740045 Authentication-Results: imf11.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=QWun8u4M; dmarc=none; spf=pass (imf11.hostedemail.com: domain of akpm@linux-foundation.org designates 145.40.68.75 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org X-Stat-Signature: ygwfc3kntnk1m3fa8sdmoikuo7xpggwc X-HE-Tag: 1657055903-56516 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 Tue, 5 Jul 2022 20:35:32 +0800 Muchun Song wrote: > FSDAX page refcounts are 1-based, rather than 0-based: if refcount is > 1, then the page is freed. The FSDAX pages can be pinned through GUP, > then they will be unpinned via unpin_user_page() using a folio variant > to put the page, however, folio variants did not consider this special > case, the result will be to miss a wakeup event (like the user of > __fuse_dax_break_layouts()). Since FSDAX pages are only possible get > by GUP users, so fix GUP instead of folio_put() to lower overhead. > What are the user visible runtime effects of this bug?