From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from verein.lst.de ([213.95.11.211]:38599 "EHLO newverein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726133AbeJRWo0 (ORCPT ); Thu, 18 Oct 2018 18:44:26 -0400 Date: Thu, 18 Oct 2018 16:43:06 +0200 From: Christoph Hellwig To: Jens Axboe Cc: Ming Lei , linux-block@vger.kernel.org, Vitaly Kuznetsov , Dave Chinner , Linux FS Devel , "Darrick J . Wong" , xfs@vger.kernel.org, Christoph Hellwig , Bart Van Assche , Matthew Wilcox Subject: Re: [PATCH 1/5] block: warn on un-aligned DMA IO buffer Message-ID: <20181018144306.GA27353@lst.de> References: <20181018131817.11813-1-ming.lei@redhat.com> <20181018131817.11813-2-ming.lei@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Thu, Oct 18, 2018 at 08:27:28AM -0600, Jens Axboe wrote: > On 10/18/18 7:18 AM, Ming Lei wrote: > > Now we only check if DMA IO buffer is aligned to queue_dma_alignment() > > for pass-through request, and it isn't done for normal IO request. > > > > Given the check has to be done on each bvec, it isn't efficient to add the > > check in generic_make_request_checks(). > > > > This patch addes one WARN in blk_queue_split() for capturing this issue. > > I don't want to do this, because then we are forever doomed to > have something that fully loops a bio at submission time. I > absolutely hate the splitting we have and the need for it, > hopefully it can go away for a subset of IOs at some point. It is just a WARN_ON - no one should rely on it, but it is a good debug aid.