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=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no 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 CCC3AC07E9B for ; Mon, 19 Jul 2021 15:17:52 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 479D761264 for ; Mon, 19 Jul 2021 15:17:50 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 479D761264 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id BB9478D00F4; Mon, 19 Jul 2021 11:17:50 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id B68998D00EC; Mon, 19 Jul 2021 11:17:50 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A096A8D00F4; Mon, 19 Jul 2021 11:17:50 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0077.hostedemail.com [216.40.44.77]) by kanga.kvack.org (Postfix) with ESMTP id 779308D00EC for ; Mon, 19 Jul 2021 11:17:50 -0400 (EDT) Received: from smtpin28.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 15380231C3 for ; Mon, 19 Jul 2021 15:17:49 +0000 (UTC) X-FDA: 78379692258.28.08AAB45 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by imf27.hostedemail.com (Postfix) with ESMTP id 6803870009CC for ; Mon, 19 Jul 2021 15:17:48 +0000 (UTC) Received: by verein.lst.de (Postfix, from userid 2407) id E6FF767373; Mon, 19 Jul 2021 17:17:44 +0200 (CEST) Date: Mon, 19 Jul 2021 17:17:44 +0200 From: Christoph Hellwig To: Shiyang Ruan Cc: linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org, nvdimm@lists.linux.dev, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, dm-devel@redhat.com, darrick.wong@oracle.com, dan.j.williams@intel.com, david@fromorbit.com, hch@lst.de, agk@redhat.com, snitzer@redhat.com, rgoldwyn@suse.de Subject: Re: [PATCH v5 2/9] dax: Introduce holder for dax_device Message-ID: <20210719151744.GA22718@lst.de> References: <20210628000218.387833-1-ruansy.fnst@fujitsu.com> <20210628000218.387833-3-ruansy.fnst@fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210628000218.387833-3-ruansy.fnst@fujitsu.com> User-Agent: Mutt/1.5.17 (2007-11-01) Authentication-Results: imf27.hostedemail.com; dkim=none; dmarc=none; spf=none (imf27.hostedemail.com: domain of hch@lst.de has no SPF policy when checking 213.95.11.211) smtp.mailfrom=hch@lst.de X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 6803870009CC X-Stat-Signature: qt7rgd5yabi1gpqxxtz4i4mzhjej9q86 X-HE-Tag: 1626707868-302645 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 Mon, Jun 28, 2021 at 08:02:11AM +0800, Shiyang Ruan wrote: > +int dax_holder_notify_failure(struct dax_device *dax_dev, loff_t offset, > + size_t size, void *data) > +{ > + int rc = -ENXIO; > + if (!dax_dev) > + return rc; > + > + if (dax_dev->holder_data) { > + rc = dax_dev->holder_ops->notify_failure(dax_dev, offset, > + size, data); > + if (rc == -ENODEV) > + rc = -ENXIO; > + } else > + rc = -EOPNOTSUPP; The style looks a little odd. Why not: if (!dax_dev) return -ENXIO if (!dax_dev->holder_data) return -EOPNOTSUPP; return dax_dev->holder_ops->notify_failure(dax_dev, offset, size, data); and let everyone deal with the same errno codes? Also why do we even need the dax_dev NULL check? > +void dax_set_holder(struct dax_device *dax_dev, void *holder, > + const struct dax_holder_operations *ops) > +{ > + if (!dax_dev) > + return; I don't think we really need that check here. > +void *dax_get_holder(struct dax_device *dax_dev) > +{ > + void *holder_data; > + > + if (!dax_dev) > + return NULL; Same here. > + > + down_read(&dax_dev->holder_rwsem); > + holder_data = dax_dev->holder_data; > + up_read(&dax_dev->holder_rwsem); > + > + return holder_data; That lock won't protect anything. I think we simply must have synchronization to prevent unregistration while the ->notify_failure call is in progress.