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[68.160.176.52]) by smtp.gmail.com with ESMTPSA id j13sm7195820qta.76.2022.01.11.08.15.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 11 Jan 2022 08:15:11 -0800 (PST) Date: Tue, 11 Jan 2022 11:15:09 -0500 From: Mike Snitzer To: Christoph Hellwig , Jens Axboe 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: linux-block@vger.kernel.org, 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 10.5.11.15 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 Tue, Jan 11 2022 at 3:34P -0500, Christoph Hellwig wrote: > On Tue, Dec 28, 2021 at 04:30:08PM -0500, Mike Snitzer wrote: > > Yeah, people use request-based for IO scheduling and more capable path > > selectors. Imposing bio-based would be a pretty jarring workaround for > > BLK_MQ_F_BLOCKING. request-based DM should properly support it. > > Given that nvme-tcp is the only blocking driver that has multipath > driver that driver explicitly does not intend to support dm-multipath > I'm absolutely against adding block layer cruft for this particular > use case. this diffstat amounts to what you call "cruft": block/blk-core.c | 2 +- block/blk-mq.c | 6 +++--- block/blk-mq.h | 2 +- block/blk-sysfs.c | 2 +- block/genhd.c | 5 +++-- drivers/md/dm-rq.c | 5 ++++- drivers/md/dm-rq.h | 3 ++- drivers/md/dm-table.c | 14 ++++++++++++++ drivers/md/dm.c | 5 +++-- drivers/md/dm.h | 1 + include/linux/blkdev.h | 5 +++-- include/linux/genhd.h | 12 ++++++++---- 12 files changed, 44 insertions(+), 18 deletions(-) > SCSI even has this: > > /* > * SCSI never enables blk-mq's BLK_MQ_F_BLOCKING flag so > * calling synchronize_rcu() once is enough. > */ > WARN_ON_ONCE(shost->tag_set.flags & BLK_MQ_F_BLOCKING); > Round and round we go.. Pretty tired of this. You are perfectly fine with incrementally compromising request-based DM's ability to evolve as block core does. Seriously, this patchset shouldn't warrant bickering: https://patchwork.kernel.org/project/dm-devel/list/?series=598823 Jens, this incremental weakening of what it is that DM is allowed to do is not something I can continue to work with (nor should Ming's or others' contributions be rejected for such reasons). This tribal war needs to stop. Mike -- dm-devel mailing list dm-devel@redhat.com https://listman.redhat.com/mailman/listinfo/dm-devel