From: Goldwyn Rodrigues Subject: Re: [PATCH 5/8] nowait aio: return on congested block device Date: Wed, 8 Mar 2017 09:00:09 -0600 Message-ID: <44cc02b1-f7ac-cbc6-6f09-726ae8225358@suse.de> References: <20170228233610.25456-1-rgoldwyn@suse.de> <20170228233610.25456-6-rgoldwyn@suse.de> <0d1ba678-69c0-16ce-6c3e-475cd8da203c@grimberg.me> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Cc: 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: Sagi Grimberg , jack@suse.com Return-path: Received: from mx2.suse.de ([195.135.220.15]:43992 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751394AbdCHPEP (ORCPT ); Wed, 8 Mar 2017 10:04:15 -0500 In-Reply-To: <0d1ba678-69c0-16ce-6c3e-475cd8da203c@grimberg.me> Sender: linux-ext4-owner@vger.kernel.org List-ID: 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/ -- Goldwyn