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[68.160.176.52]) by smtp.gmail.com with ESMTPSA id p9sm395169qtk.39.2022.01.19.13.03.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 19 Jan 2022 13:03:17 -0800 (PST) Date: Wed, 19 Jan 2022 16:03:16 -0500 From: Mike Snitzer To: Christoph Hellwig Message-ID: References: <20211221141459.1368176-1-ming.lei@redhat.com> MIME-Version: 1.0 In-Reply-To: X-Scanned-By: MIMEDefang 2.85 on 10.11.54.8 X-loop: dm-devel@redhat.com Cc: Jens Axboe , linux-block@vger.kernel.org, Jeff Moyer , dm-devel@redhat.com, Ming Lei Subject: Re: [dm-devel] [PATCH 0/3] blk-mq/dm-rq: support BLK_MQ_F_BLOCKING for dm-rq 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 10.5.11.14 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 Mon, Jan 17 2022 at 3:10P -0500, Christoph Hellwig wrote: > On Tue, Jan 11, 2022 at 01:23:53PM -0500, Jeff Moyer wrote: > > Maybe I have bad taste, but the patches didn't look like cruft to me. > > :) > > They do to me. The extend the corner case of request on request > stacking that already is a bit of mess even more by adding yet another > special case in the block layer. Ming's first patch: https://patchwork.kernel.org/project/dm-devel/patch/20211221141459.1368176-2-ming.lei@redhat.com/ is pure cleanup for the mess that went in this merge cycle. All that dm-rq context aside, Ming's 1st patch is the correct way to clean up the block core flags/state (internal vs external, etc). But the 2nd paragraph of that first patch's header should be moved to Ming's 2nd patch because it explains why DM needs the new blk_alloc_disk_srcu() interface, e.g.: "But dm queue is allocated before tagset is allocated" (so it confirms it best to explain that in 2nd patch). But really even Ming's 2nd patch: https://patchwork.kernel.org/project/dm-devel/patch/20211221141459.1368176-3-ming.lei@redhat.com/ should _not_ need to be debated like this. Fact is alloc_disk() has always mirrored blk_alloc_queue()'s args. So Ming's 2nd patch should be done anyway to expose meaningful control over request_queue allocation. If anything, the 2nd patch should just add the 'alloc_srcu' arg to blk_alloc_disk() and change all but NVMe callers to pass false. Put another way: when the 'node_id' arg was added to blk_alloc_queue() a new blk_alloc_disk_numa_node() wasn't added (despite most block drivers still only using NUMA_NO_NODE). This new 'alloc_srcu' flag is seen to be more niche, but it really should be no different on an interface symmetry and design level. > > I'm not sure why we'd prevent users from using dm-mpath on nvmeof. I > > think there's agreement that the nvme native multipath implementation is > > the preferred way (that's the default in rhel9, even), but I don't think > > that's a reason to nack this patch set. > > > > Or have I missed your point entirely? > > No you have not missed the point. nvme-multipath exists longer than > the nvme-tcp driver and is the only supported one for it upstream for > a good reason. If RedHat wants to do their own weirdo setups they can > patch their kernels, but please leave the upstrem code alone. Patch 3 can be left out if you'd like to force your world view on everyone... you've already "won", _pretty please_ stop being so punitive by blocking reasonable change. We really can get along if we're all willing to be intellectually honest. To restate: Ming's patches 1 and 2 really are not "cruft". They expose control over request_queue allocation that should be accessible by both blk_alloc_queue() and blk_alloc_disk(). Mike -- dm-devel mailing list dm-devel@redhat.com https://listman.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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8DEB7C433EF for ; Wed, 19 Jan 2022 21:03:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245634AbiASVDV (ORCPT ); Wed, 19 Jan 2022 16:03:21 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:22615 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S245242AbiASVDU (ORCPT ); Wed, 19 Jan 2022 16:03:20 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1642626200; 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=RclBE4j/l0I/3NwHx38MPLT8IFYI9e2HwkR+3iNqKtg=; b=MPPGG3xZWHn+gtMvCtIGWIu1Ho3MDpCUVJYRY6p73SpYtmTy8NuwxWO0+vF/mE6wUZnCut VKV+qLjpXhWayFcissGdopdCa54DJE4tIgg9JCuXnxQWz573j3O835qGcwkBcAT3ZsTwZl 6KkNLgmuklWph/cnwyQ3+TCyepvJTbs= Received: from mail-qv1-f70.google.com (mail-qv1-f70.google.com [209.85.219.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-618-2sjSrKZsOIWFyMoHV88rGw-1; Wed, 19 Jan 2022 16:03:18 -0500 X-MC-Unique: 2sjSrKZsOIWFyMoHV88rGw-1 Received: by mail-qv1-f70.google.com with SMTP id kk29-20020a056214509d00b0041c9228d334so3954917qvb.23 for ; Wed, 19 Jan 2022 13:03:18 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=RclBE4j/l0I/3NwHx38MPLT8IFYI9e2HwkR+3iNqKtg=; b=SU3AXazY91p9tClVBKaLINrz9nGXH1t7qQ08cGPC50dGs6KGm5IqqFNMpn542IhdKS WU4dip/LlNs50xnibcL8t503G+JRHhiBczpkx6TjJ7EY5UQ59gzMDsZRPoyB3VTnpYpY QtlkLtjN7scMShjz6202m2XE+Yy9XnM43VAvQLES6kEWLhgC5+yAfiXUVcc3jhY9M3MT b6Pk2ZRyWWGIjYvIYQgrnYuGDeBphNKMmAlJgrI2Oc9EwbjR5uSowOPXeaUFii89ufcN jbFCHhTXSSNsrHWWh6huCjxWzJ/apog50WTubZrrBFZCqZQTJIeF81G8V0IU4Uw+ph6g ouFA== X-Gm-Message-State: AOAM533DDpQNM7rmsf3zP/b4YuzvUMN5osx6yZOR5JHv1FJFpEk+Lexj +eciosav52Lq7zBjqNGqNJsIE4BGqy4fPcSHUtybrPmo7+RvbTlvaIxYbJlCOttUNBm3dLbHiAk Hp/BE6/ceoIcpcvH8Junl2Q== X-Received: by 2002:a37:44cd:: with SMTP id r196mr22696145qka.90.1642626198298; Wed, 19 Jan 2022 13:03:18 -0800 (PST) X-Google-Smtp-Source: ABdhPJzMQlq2CHwYQqUY+ubV1rButdo/mjYgi37vO2ELr0QtyVP0CLAc4/4GF1GPZIaw1sTQfZZXNQ== X-Received: by 2002:a37:44cd:: with SMTP id r196mr22696123qka.90.1642626198034; Wed, 19 Jan 2022 13:03:18 -0800 (PST) Received: from localhost (pool-68-160-176-52.bstnma.fios.verizon.net. [68.160.176.52]) by smtp.gmail.com with ESMTPSA id p9sm395169qtk.39.2022.01.19.13.03.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 19 Jan 2022 13:03:17 -0800 (PST) Date: Wed, 19 Jan 2022 16:03:16 -0500 From: Mike Snitzer To: Christoph Hellwig Cc: Jeff Moyer , Jens Axboe , linux-block@vger.kernel.org, dm-devel@redhat.com, Ming Lei Subject: Re: [PATCH 0/3] blk-mq/dm-rq: support BLK_MQ_F_BLOCKING for dm-rq Message-ID: References: <20211221141459.1368176-1-ming.lei@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Mon, Jan 17 2022 at 3:10P -0500, Christoph Hellwig wrote: > On Tue, Jan 11, 2022 at 01:23:53PM -0500, Jeff Moyer wrote: > > Maybe I have bad taste, but the patches didn't look like cruft to me. > > :) > > They do to me. The extend the corner case of request on request > stacking that already is a bit of mess even more by adding yet another > special case in the block layer. Ming's first patch: https://patchwork.kernel.org/project/dm-devel/patch/20211221141459.1368176-2-ming.lei@redhat.com/ is pure cleanup for the mess that went in this merge cycle. All that dm-rq context aside, Ming's 1st patch is the correct way to clean up the block core flags/state (internal vs external, etc). But the 2nd paragraph of that first patch's header should be moved to Ming's 2nd patch because it explains why DM needs the new blk_alloc_disk_srcu() interface, e.g.: "But dm queue is allocated before tagset is allocated" (so it confirms it best to explain that in 2nd patch). But really even Ming's 2nd patch: https://patchwork.kernel.org/project/dm-devel/patch/20211221141459.1368176-3-ming.lei@redhat.com/ should _not_ need to be debated like this. Fact is alloc_disk() has always mirrored blk_alloc_queue()'s args. So Ming's 2nd patch should be done anyway to expose meaningful control over request_queue allocation. If anything, the 2nd patch should just add the 'alloc_srcu' arg to blk_alloc_disk() and change all but NVMe callers to pass false. Put another way: when the 'node_id' arg was added to blk_alloc_queue() a new blk_alloc_disk_numa_node() wasn't added (despite most block drivers still only using NUMA_NO_NODE). This new 'alloc_srcu' flag is seen to be more niche, but it really should be no different on an interface symmetry and design level. > > I'm not sure why we'd prevent users from using dm-mpath on nvmeof. I > > think there's agreement that the nvme native multipath implementation is > > the preferred way (that's the default in rhel9, even), but I don't think > > that's a reason to nack this patch set. > > > > Or have I missed your point entirely? > > No you have not missed the point. nvme-multipath exists longer than > the nvme-tcp driver and is the only supported one for it upstream for > a good reason. If RedHat wants to do their own weirdo setups they can > patch their kernels, but please leave the upstrem code alone. Patch 3 can be left out if you'd like to force your world view on everyone... you've already "won", _pretty please_ stop being so punitive by blocking reasonable change. We really can get along if we're all willing to be intellectually honest. To restate: Ming's patches 1 and 2 really are not "cruft". They expose control over request_queue allocation that should be accessible by both blk_alloc_queue() and blk_alloc_disk(). Mike