From: Jan Kara Subject: Re: [PATCH 5/8] nowait aio: return on congested block device Date: Wed, 8 Mar 2017 16:28:06 +0100 Message-ID: <20170308152806.GA9288@quack2.suse.cz> References: <20170228233610.25456-1-rgoldwyn@suse.de> <20170228233610.25456-6-rgoldwyn@suse.de> <0d1ba678-69c0-16ce-6c3e-475cd8da203c@grimberg.me> <44cc02b1-f7ac-cbc6-6f09-726ae8225358@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Sagi Grimberg , jack@suse.com, hch@infradead.org, linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org, Goldwyn Rodrigues To: Goldwyn Rodrigues Return-path: Content-Disposition: inline In-Reply-To: <44cc02b1-f7ac-cbc6-6f09-726ae8225358@suse.de> Sender: linux-btrfs-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org On Wed 08-03-17 09:00:09, Goldwyn Rodrigues wrote: > > > On 03/08/2017 01:03 AM, Sagi Grimberg wrote: > > > >> - if (likely(blk_queue_enter(q, false) == 0)) { > >> + if (likely(blk_queue_enter(q, bio_flagged(bio, BIO_NOWAIT)) > >> == 0)) { > >> ret = q->make_request_fn(q, bio); > > > > I think that for ->make_request to not block we'd need to set > > BLK_MQ_REQ_NOWAIT in blk_mq_alloc_data to avoid blocking on a tag > > allocation. > > > > Something like the untested addition below: > > I did that in the first series, but there are too many reasons to block > in blk-mq [1]. I dropped blk-mq work in v2. > > [1] https://patchwork.kernel.org/patch/9571051/ Well, that's not really good. If we cannot support this for both blk-mq and legacy block layer the feature will not be usable. So please work on blk-mq support as well. Honza -- Jan Kara SUSE Labs, CR