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=-7.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 A9D9FC63777 for ; Thu, 3 Dec 2020 09:33:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5A84B217A0 for ; Thu, 3 Dec 2020 09:33:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728883AbgLCJdy (ORCPT ); Thu, 3 Dec 2020 04:33:54 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:20333 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728664AbgLCJdy (ORCPT ); Thu, 3 Dec 2020 04:33:54 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1606987947; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=Jmel3tjqsc7Vgh83Ue1t0WC/6y10c9bSGUCqUms/GTA=; b=fytLYeqFhBUljgJsUu+Llyir/MVEfsMjpaz01XOrLVxMYFds90+n7Ao+qF3eGqqXP3/0G9 jF/8aF5LbYR1xZ+afLEfFHXtWcnfxspNm0RpXvjP1QAVYxmgeC6xi1xdtW1WlDKkH0vEu5 hEEGHPzq5lrd8RCIa9O2AR6gj/0TJ0A= 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-337-oQcaGzWtP5-v7yXp30SHvg-1; Thu, 03 Dec 2020 04:32:25 -0500 X-MC-Unique: oQcaGzWtP5-v7yXp30SHvg-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 2D5D9185E497; Thu, 3 Dec 2020 09:32:24 +0000 (UTC) Received: from T590 (ovpn-13-173.pek2.redhat.com [10.72.13.173]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 627CB1899A; Thu, 3 Dec 2020 09:32:10 +0000 (UTC) Date: Thu, 3 Dec 2020 17:32:01 +0800 From: Ming Lei To: Christoph Hellwig Cc: Jens Axboe , Tejun Heo , Coly Li , Song Liu , dm-devel@redhat.com, linux-bcache@vger.kernel.org, linux-raid@vger.kernel.org, linux-s390@vger.kernel.org, linux-block@vger.kernel.org Subject: Re: [PATCH 3/9] block: store a block_device pointer in struct bio Message-ID: <20201203093201.GC633702@T590> References: <20201201165424.2030647-1-hch@lst.de> <20201201165424.2030647-4-hch@lst.de> <20201203063941.GA629758@T590> <20201203071055.GA633702@T590> <20201203082951.GA15581@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201203082951.GA15581@lst.de> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Precedence: bulk List-ID: X-Mailing-List: linux-raid@vger.kernel.org On Thu, Dec 03, 2020 at 09:29:51AM +0100, Christoph Hellwig wrote: > On Thu, Dec 03, 2020 at 03:10:55PM +0800, Ming Lei wrote: > > On Thu, Dec 03, 2020 at 02:40:04PM +0800, Ming Lei wrote: > > > On Tue, Dec 01, 2020 at 05:54:18PM +0100, Christoph Hellwig wrote: > > > > Replace the gendisk pointer in struct bio with a pointer to the newly > > > > improved struct block device. From that the gendisk can be trivially > > > > accessed with an extra indirection, but it also allows to directly > > > > look up all information related to partition remapping. > > > > > > The extra indirection is often done in fast path, so just wondering why > > > you don't consider to embed gendisk into block_device? Then the extra > > > indirection can be avoided. > > > > oops, that is only possible for disk, and indirection is still needed > > for partitions. > > I looked into that, but given that the block device is allocated as part > of the inode we'd need to tell ->alloc_inode if we want to allocate the > small inode without the gendisk, or the large one with it which doesn't > work with the current interface. I guess it could be done without fs code change, because now block device is always allocated by bdev_alloc() since 22ae8ce8b892("block: simplify bdev/disk lookup in blkdev_get"). And one manual inode allocation with a bit duplication from new_inode_pseudo() should be fine: allocate big inode for disk, and small for partition inode_init_always(sb, inode); if (inode) { spin_lock(&inode->i_lock); inode->i_state = 0; spin_unlock(&inode->i_lock); INIT_LIST_HEAD(&inode->i_sb_list); inode_sb_list_add(inode); } > Beause the hd_struct is gone we're > still not using more structures in the I/O path than we did before. Indeed, and block_device instance is often cached in IO path. thanks, Ming 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=-7.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 711B5C63777 for ; Thu, 3 Dec 2020 09:34:19 +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 B93EC2222E for ; Thu, 3 Dec 2020 09:34:18 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B93EC2222E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=tempfail smtp.mailfrom=dm-devel-bounces@redhat.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1606988057; h=from:from:sender: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:list-id:list-help: list-unsubscribe:list-subscribe:list-post; bh=U8UAaDSqvfPJXWjSC/bDjni56aVSyi6hoq8l4Vs4ZxI=; b=UIJ2n6xeQCPJg6sOTGmJASEqJkJz0p+abDAQcw6gjMMTdL/j9fxOd68QiLoje6r1oBISev fzrEKx+APH+SMqqJhEJTBeUwkoQNOq19kCziH5otm8fXoJbDmsj2+javhfMWh9biWQnram WRo7WJ1/lKjDxF8yVqorq0ZeqLpubkQ= 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-550-0pfEtzScPiyGwX3cHQVyKA-1; Thu, 03 Dec 2020 04:34:15 -0500 X-MC-Unique: 0pfEtzScPiyGwX3cHQVyKA-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 78B49107464E; Thu, 3 Dec 2020 09:34:10 +0000 (UTC) Received: from colo-mx.corp.redhat.com (colo-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.21]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 973FA5D6AC; Thu, 3 Dec 2020 09:34:09 +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 A5B0E5002C; Thu, 3 Dec 2020 09:34:07 +0000 (UTC) Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) by lists01.pubmisc.prod.ext.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id 0B39WObs015365 for ; Thu, 3 Dec 2020 04:32:24 -0500 Received: by smtp.corp.redhat.com (Postfix) id 2A8FE13470; Thu, 3 Dec 2020 09:32:24 +0000 (UTC) Received: from T590 (ovpn-13-173.pek2.redhat.com [10.72.13.173]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 627CB1899A; Thu, 3 Dec 2020 09:32:10 +0000 (UTC) Date: Thu, 3 Dec 2020 17:32:01 +0800 From: Ming Lei To: Christoph Hellwig Message-ID: <20201203093201.GC633702@T590> References: <20201201165424.2030647-1-hch@lst.de> <20201201165424.2030647-4-hch@lst.de> <20201203063941.GA629758@T590> <20201203071055.GA633702@T590> <20201203082951.GA15581@lst.de> MIME-Version: 1.0 In-Reply-To: <20201203082951.GA15581@lst.de> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-loop: dm-devel@redhat.com Cc: Jens Axboe , linux-s390@vger.kernel.org, linux-bcache@vger.kernel.org, Coly Li , linux-raid@vger.kernel.org, Song Liu , dm-devel@redhat.com, linux-block@vger.kernel.org, Tejun Heo Subject: Re: [dm-devel] [PATCH 3/9] block: store a block_device pointer in struct bio 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 10.5.11.15 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, Dec 03, 2020 at 09:29:51AM +0100, Christoph Hellwig wrote: > On Thu, Dec 03, 2020 at 03:10:55PM +0800, Ming Lei wrote: > > On Thu, Dec 03, 2020 at 02:40:04PM +0800, Ming Lei wrote: > > > On Tue, Dec 01, 2020 at 05:54:18PM +0100, Christoph Hellwig wrote: > > > > Replace the gendisk pointer in struct bio with a pointer to the newly > > > > improved struct block device. From that the gendisk can be trivially > > > > accessed with an extra indirection, but it also allows to directly > > > > look up all information related to partition remapping. > > > > > > The extra indirection is often done in fast path, so just wondering why > > > you don't consider to embed gendisk into block_device? Then the extra > > > indirection can be avoided. > > > > oops, that is only possible for disk, and indirection is still needed > > for partitions. > > I looked into that, but given that the block device is allocated as part > of the inode we'd need to tell ->alloc_inode if we want to allocate the > small inode without the gendisk, or the large one with it which doesn't > work with the current interface. I guess it could be done without fs code change, because now block device is always allocated by bdev_alloc() since 22ae8ce8b892("block: simplify bdev/disk lookup in blkdev_get"). And one manual inode allocation with a bit duplication from new_inode_pseudo() should be fine: allocate big inode for disk, and small for partition inode_init_always(sb, inode); if (inode) { spin_lock(&inode->i_lock); inode->i_state = 0; spin_unlock(&inode->i_lock); INIT_LIST_HEAD(&inode->i_sb_list); inode_sb_list_add(inode); } > Beause the hd_struct is gone we're > still not using more structures in the I/O path than we did before. Indeed, and block_device instance is often cached in IO path. thanks, Ming -- dm-devel mailing list dm-devel@redhat.com https://www.redhat.com/mailman/listinfo/dm-devel