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=-5.3 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 6726DC63777 for ; Fri, 20 Nov 2020 09:16:09 +0000 (UTC) Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [63.128.21.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 91F5D2224C for ; Fri, 20 Nov 2020 09:16:08 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 91F5D2224C Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: mail.kernel.org; spf=tempfail smtp.mailfrom=dm-devel-bounces@redhat.com Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-518-fpHn6VgfPCGeHiRpNuvXUQ-1; Fri, 20 Nov 2020 04:16:05 -0500 X-MC-Unique: fpHn6VgfPCGeHiRpNuvXUQ-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 1E98F8797DA; Fri, 20 Nov 2020 09:16:00 +0000 (UTC) Received: from colo-mx.corp.redhat.com (colo-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.20]) by smtp.corp.redhat.com (Postfix) with ESMTPS id E6FF960BE2; Fri, 20 Nov 2020 09:15:59 +0000 (UTC) Received: from lists01.pubmisc.prod.ext.phx2.redhat.com (lists01.pubmisc.prod.ext.phx2.redhat.com [10.5.19.33]) by colo-mx.corp.redhat.com (Postfix) with ESMTP id 8164C180954D; Fri, 20 Nov 2020 09:15:59 +0000 (UTC) Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) by lists01.pubmisc.prod.ext.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id 0AK9FwAK021986 for ; Fri, 20 Nov 2020 04:15:58 -0500 Received: by smtp.corp.redhat.com (Postfix) id 0AB1C2166B2B; Fri, 20 Nov 2020 09:15:58 +0000 (UTC) Received: from mimecast-mx02.redhat.com (mimecast03.extmail.prod.ext.rdu2.redhat.com [10.11.55.19]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 05E202166B28 for ; Fri, 20 Nov 2020 09:15:55 +0000 (UTC) Received: from us-smtp-1.mimecast.com (us-smtp-2.mimecast.com [205.139.110.61]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-SHA384 (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id A9A24811E85 for ; Fri, 20 Nov 2020 09:15:55 +0000 (UTC) Received: from verein.lst.de (verein.lst.de [213.95.11.211]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-524-k73oXmuNMEqMq5Oq09A2Aw-1; Fri, 20 Nov 2020 04:15:51 -0500 X-MC-Unique: k73oXmuNMEqMq5Oq09A2Aw-1 Received: by verein.lst.de (Postfix, from userid 2407) id 8D37C67373; Fri, 20 Nov 2020 10:15:47 +0100 (CET) Date: Fri, 20 Nov 2020 10:15:46 +0100 From: Christoph Hellwig To: Jan Kara Message-ID: <20201120091546.GE21715@lst.de> References: <20201118084800.2339180-1-hch@lst.de> <20201118084800.2339180-16-hch@lst.de> <20201119143921.GX1981@quack2.suse.cz> MIME-Version: 1.0 In-Reply-To: <20201119143921.GX1981@quack2.suse.cz> User-Agent: Mutt/1.5.17 (2007-11-01) X-Mimecast-Impersonation-Protect: Policy=CLT - Impersonation Protection Definition; Similar Internal Domain=false; Similar Monitored External Domain=false; Custom External Domain=false; Mimecast External Domain=false; Newly Observed Domain=false; Internal User Name=false; Custom Display Name List=false; Reply-to Address Mismatch=false; Targeted Threat Dictionary=false; Mimecast Threat Dictionary=false; Custom Threat Dictionary=false X-Scanned-By: MIMEDefang 2.78 on 10.11.54.6 X-loop: dm-devel@redhat.com Cc: Jens Axboe , Mike Snitzer , Konrad Rzeszutek Wilk , Richard Weinberger , Josef Bacik , Coly Li , linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, dm-devel@redhat.com, linux-mtd@lists.infradead.org, linux-mm@kvack.org, Jan Kara , Tejun Heo , xen-devel@lists.xenproject.org, linux-bcache@vger.kernel.org, Christoph Hellwig Subject: Re: [dm-devel] [PATCH 15/20] block: merge struct block_device and struct hd_struct X-BeenThere: dm-devel@redhat.com X-Mailman-Version: 2.1.12 Precedence: junk List-Id: device-mapper development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=dm-devel-bounces@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Disposition: inline Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit On Thu, Nov 19, 2020 at 03:39:21PM +0100, Jan Kara wrote: > This patch is kind of difficult to review due to the size of mostly > mechanical changes mixed with not completely mechanical changes. Can we > perhaps split out the mechanical bits? E.g. the rq->part => rq->bdev > renaming is mechanical and notable part of the patch. Similarly the > part->foo => part->bd_foo bits... We'd end with really weird patches that way. Never mind that I'm not even sure how we could mechnically do the renaming. > > Also I'm kind of wondering: AFAIU the new lifetime rules, gendisk holds > bdev reference and bdev is created on gendisk allocation so bdev lifetime is > strictly larger than gendisk lifetime. But what now keeps bdev->bd_disk > reference safe in presence device hot unplug? In most cases we are still > protected by gendisk reference taken in __blkdev_get() but how about > disk->lookup_sem and disk->flags dereferences before we actually grab the > reference? Good question. I'll need to think about this a bit more. > Also I find it rather non-obvious (although elegant ;) that bdev->bd_device > rules the lifetime of gendisk. Can you perhaps explain this in the > changelog and probably also add somewhere to source a documentation about > the new lifetime rules? Yes. > > -struct hd_struct *__disk_get_part(struct gendisk *disk, int partno); > > +static inline struct block_device *__bdget_disk(struct gendisk *disk, > > + int partno) > > +{ > > + struct disk_part_tbl *ptbl = rcu_dereference(disk->part_tbl); > > + > > + if (unlikely(partno < 0 || partno >= ptbl->len)) > > + return NULL; > > + return rcu_dereference(ptbl->part[partno]); > > +} > > I understand this is lower-level counterpart of bdget_disk() but it is > confusing to me that this has 'bdget' in the name and returns no bdev > reference. Can we call it like __bdev_from_disk() or something like that? Sure. -- dm-devel mailing list dm-devel@redhat.com https://www.redhat.com/mailman/listinfo/dm-devel 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=-5.3 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 AA167C64E7C for ; Fri, 20 Nov 2020 09:16:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 74E8822264 for ; Fri, 20 Nov 2020 09:16:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727421AbgKTJPx (ORCPT ); Fri, 20 Nov 2020 04:15:53 -0500 Received: from verein.lst.de ([213.95.11.211]:42108 "EHLO verein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727354AbgKTJPw (ORCPT ); Fri, 20 Nov 2020 04:15:52 -0500 Received: by verein.lst.de (Postfix, from userid 2407) id 8D37C67373; Fri, 20 Nov 2020 10:15:47 +0100 (CET) Date: Fri, 20 Nov 2020 10:15:46 +0100 From: Christoph Hellwig To: Jan Kara Cc: Christoph Hellwig , Jens Axboe , Tejun Heo , Josef Bacik , Konrad Rzeszutek Wilk , Coly Li , Mike Snitzer , dm-devel@redhat.com, Richard Weinberger , Jan Kara , linux-block@vger.kernel.org, xen-devel@lists.xenproject.org, linux-bcache@vger.kernel.org, linux-mtd@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 15/20] block: merge struct block_device and struct hd_struct Message-ID: <20201120091546.GE21715@lst.de> References: <20201118084800.2339180-1-hch@lst.de> <20201118084800.2339180-16-hch@lst.de> <20201119143921.GX1981@quack2.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201119143921.GX1981@quack2.suse.cz> User-Agent: Mutt/1.5.17 (2007-11-01) Precedence: bulk List-ID: X-Mailing-List: linux-bcache@vger.kernel.org On Thu, Nov 19, 2020 at 03:39:21PM +0100, Jan Kara wrote: > This patch is kind of difficult to review due to the size of mostly > mechanical changes mixed with not completely mechanical changes. Can we > perhaps split out the mechanical bits? E.g. the rq->part => rq->bdev > renaming is mechanical and notable part of the patch. Similarly the > part->foo => part->bd_foo bits... We'd end with really weird patches that way. Never mind that I'm not even sure how we could mechnically do the renaming. > > Also I'm kind of wondering: AFAIU the new lifetime rules, gendisk holds > bdev reference and bdev is created on gendisk allocation so bdev lifetime is > strictly larger than gendisk lifetime. But what now keeps bdev->bd_disk > reference safe in presence device hot unplug? In most cases we are still > protected by gendisk reference taken in __blkdev_get() but how about > disk->lookup_sem and disk->flags dereferences before we actually grab the > reference? Good question. I'll need to think about this a bit more. > Also I find it rather non-obvious (although elegant ;) that bdev->bd_device > rules the lifetime of gendisk. Can you perhaps explain this in the > changelog and probably also add somewhere to source a documentation about > the new lifetime rules? Yes. > > -struct hd_struct *__disk_get_part(struct gendisk *disk, int partno); > > +static inline struct block_device *__bdget_disk(struct gendisk *disk, > > + int partno) > > +{ > > + struct disk_part_tbl *ptbl = rcu_dereference(disk->part_tbl); > > + > > + if (unlikely(partno < 0 || partno >= ptbl->len)) > > + return NULL; > > + return rcu_dereference(ptbl->part[partno]); > > +} > > I understand this is lower-level counterpart of bdget_disk() but it is > confusing to me that this has 'bdget' in the name and returns no bdev > reference. Can we call it like __bdev_from_disk() or something like that? Sure. 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=-5.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 3AFE5C5519F for ; Fri, 20 Nov 2020 09:16:24 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id B731A2236F for ; Fri, 20 Nov 2020 09:16:23 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="CApx9UNQ" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B731A2236F Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-mtd-bounces+linux-mtd=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=K4ZzS5ASwRxv3LDACwFhMYNgisSgM32ARd4B+AY7ptg=; b=CApx9UNQbhMsvpUGmCcWqi3q/ /eN7D09EkwpSDL6WA0XKrbPdCeGER/lyKz5Oom4MREnU63/yTayUsOZI1zyPma3KXNUiSQVcrbtSP p9P8sFDNwCYYsp4DAP3mHXu0Kiz0Pw3DIzKhmfY+EhRnxXssht9mI6UU8GdXzJxLIZi/Zfd/u4wXT tpUg3+yrS85FaRReGhRqcrT424dAxqKhSuIANeNDgEXa2kDz9Ol8ZyQYjKy7abIcXNaRdY2Hb/wLz /4keQdT/Zx+PT366LUK16jZmHCwfk/NRMg7b2F4mhnhHuc5sVb/ERjJ7D/Te62Ariwe8ABa1qPvE8 Du7yVS5Pw==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kg2WH-00064c-OU; Fri, 20 Nov 2020 09:15:53 +0000 Received: from verein.lst.de ([213.95.11.211]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1kg2WF-000636-Aq for linux-mtd@lists.infradead.org; Fri, 20 Nov 2020 09:15:52 +0000 Received: by verein.lst.de (Postfix, from userid 2407) id 8D37C67373; Fri, 20 Nov 2020 10:15:47 +0100 (CET) Date: Fri, 20 Nov 2020 10:15:46 +0100 From: Christoph Hellwig To: Jan Kara Subject: Re: [PATCH 15/20] block: merge struct block_device and struct hd_struct Message-ID: <20201120091546.GE21715@lst.de> References: <20201118084800.2339180-1-hch@lst.de> <20201118084800.2339180-16-hch@lst.de> <20201119143921.GX1981@quack2.suse.cz> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20201119143921.GX1981@quack2.suse.cz> User-Agent: Mutt/1.5.17 (2007-11-01) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201120_041551_540324_BC56EDA6 X-CRM114-Status: GOOD ( 19.38 ) X-BeenThere: linux-mtd@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Jens Axboe , Mike Snitzer , Konrad Rzeszutek Wilk , Richard Weinberger , Josef Bacik , Coly Li , linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, dm-devel@redhat.com, linux-mtd@lists.infradead.org, linux-mm@kvack.org, Jan Kara , Tejun Heo , xen-devel@lists.xenproject.org, linux-bcache@vger.kernel.org, Christoph Hellwig Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-mtd" Errors-To: linux-mtd-bounces+linux-mtd=archiver.kernel.org@lists.infradead.org On Thu, Nov 19, 2020 at 03:39:21PM +0100, Jan Kara wrote: > This patch is kind of difficult to review due to the size of mostly > mechanical changes mixed with not completely mechanical changes. Can we > perhaps split out the mechanical bits? E.g. the rq->part => rq->bdev > renaming is mechanical and notable part of the patch. Similarly the > part->foo => part->bd_foo bits... We'd end with really weird patches that way. Never mind that I'm not even sure how we could mechnically do the renaming. > > Also I'm kind of wondering: AFAIU the new lifetime rules, gendisk holds > bdev reference and bdev is created on gendisk allocation so bdev lifetime is > strictly larger than gendisk lifetime. But what now keeps bdev->bd_disk > reference safe in presence device hot unplug? In most cases we are still > protected by gendisk reference taken in __blkdev_get() but how about > disk->lookup_sem and disk->flags dereferences before we actually grab the > reference? Good question. I'll need to think about this a bit more. > Also I find it rather non-obvious (although elegant ;) that bdev->bd_device > rules the lifetime of gendisk. Can you perhaps explain this in the > changelog and probably also add somewhere to source a documentation about > the new lifetime rules? Yes. > > -struct hd_struct *__disk_get_part(struct gendisk *disk, int partno); > > +static inline struct block_device *__bdget_disk(struct gendisk *disk, > > + int partno) > > +{ > > + struct disk_part_tbl *ptbl = rcu_dereference(disk->part_tbl); > > + > > + if (unlikely(partno < 0 || partno >= ptbl->len)) > > + return NULL; > > + return rcu_dereference(ptbl->part[partno]); > > +} > > I understand this is lower-level counterpart of bdget_disk() but it is > confusing to me that this has 'bdget' in the name and returns no bdev > reference. Can we call it like __bdev_from_disk() or something like that? Sure. ______________________________________________________ Linux MTD discussion mailing list http://lists.infradead.org/mailman/listinfo/linux-mtd/