From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Mon, 5 Dec 2016 05:05:17 -0800 From: Christoph Hellwig To: Jens Axboe Cc: axboe@kernel.dk, linux-block@vger.kernel.org, paolo.valente@linaro.org Subject: Re: [PATCH 1/7] block: use legacy path for flush requests for MQ with a scheduler Message-ID: <20161205130517.GA7100@infradead.org> References: <1480734921-23701-1-git-send-email-axboe@fb.com> <1480734921-23701-2-git-send-email-axboe@fb.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <1480734921-23701-2-git-send-email-axboe@fb.com> List-ID: On Fri, Dec 02, 2016 at 08:15:15PM -0700, Jens Axboe wrote: > No functional changes with this patch, it's just in preparation for > supporting legacy schedulers on blk-mq. Ewww. I think without refactoring to clear what 'use_mq_path' means here and better naming this is a total non-started. Even with that we'll now have yet another code path to worry about. Is there any chance to instead consolidate into a single path? > struct request *blk_get_request(struct request_queue *q, int rw, gfp_t gfp_mask) > { > - if (q->mq_ops) > + if (blk_use_mq_path(q)) > return blk_mq_alloc_request(q, rw, > (gfp_mask & __GFP_DIRECT_RECLAIM) ? > 0 : BLK_MQ_REQ_NOWAIT); So now with blk-mq and an elevator set we go into blk_old_get_request, hich will simply allocate new requests. How does this not break every existing driver?