From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.4 required=3.0 tests=DKIM_SIGNED, MAILING_LIST_MULTI,SPF_PASS,T_DKIM_INVALID,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A3B9CC433F4 for ; Sat, 1 Sep 2018 00:29:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 418E42083A for ; Sat, 1 Sep 2018 00:29:06 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Gx+AmDGB" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 418E42083A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727611AbeIAEjB (ORCPT ); Sat, 1 Sep 2018 00:39:01 -0400 Received: from mail-pl1-f196.google.com ([209.85.214.196]:36308 "EHLO mail-pl1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726430AbeIAEjB (ORCPT ); Sat, 1 Sep 2018 00:39:01 -0400 Received: by mail-pl1-f196.google.com with SMTP id e11-v6so6159259plb.3; Fri, 31 Aug 2018 17:29:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=StEz1mAJv0KzVZGP1EaarXGr3LePzazclN3Lxla0Mp0=; b=Gx+AmDGBv/s3qria3fxuFzM5YHMkloGdUQ+f0LNYy2qzNN30B5ctsJi/ZczOaKxzKp ol1RTToAh6Fj6/FRpNXItJchWh2ri4Ftfaqa40Rbk4yBilWli4TlVfNztJ9xCXSON6L+ c07PuyyoWxI5+MUUVc+AZ04hbwysuksBfIomrhqMhqHOEKHT6v5HSmGR7Ei9Td5ptZOU EgLPpQtHnNw2ubvxx5HOYe8yQ8LFsyn6A4K7fkISn5mwMaQ8sr94jEhPPUk8qOEXNNwQ iQd/kqmzja5JV3czwd08abHbjFXZgAz5cKOz572pe6TTJ9OX30XWZhB7p3PB+y6HLX2v /+5Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to:user-agent; bh=StEz1mAJv0KzVZGP1EaarXGr3LePzazclN3Lxla0Mp0=; b=F4Fawt6t4S5Hcg2uGesVnxZLHGUokkaK+HCXsyWhQHBAKJfHfV18ULmDo/ryNT4/ym cD3V+EEjz78K+nhCAW0jvpbB76AqWsd7Tv/LEXY9GMZSQRSHOf/TN4Frl15lDIs61H60 ieMNtlBHqGV0ks242Y3Cymw3/7SjuIC6DE+NMkEq2+O9I8t7+fna/qXWo6IvcvBdk9JZ QP+Dce7offnrvOLsNVK6FyifKM3DiXNmblevnnOR4aaoqg53AfRkSgfU5OZoFokpAh61 /SqlyR/ZWpqlCjefv2RRuluzsz+ODFPQ83bMiDQg/DYGO7aLjoPTTK4qPlz/XdSLJqqc vtpA== X-Gm-Message-State: APzg51AXmW7zHKSrvRbeF92YcyoOIS18PrLwtn5lsukn85fhpwWCtV0+ Jtfy3oQkS900VKATmpAPVcg= X-Google-Smtp-Source: ANB0VdbLIb0C2HbaG5MWlp4s6C3ZDQ+rotzNg0vO6wVhQEC5Aw+AwpT8eVXM7uRwWIAVE/hlLZezEw== X-Received: by 2002:a17:902:8b8b:: with SMTP id ay11-v6mr17533808plb.1.1535761743820; Fri, 31 Aug 2018 17:29:03 -0700 (PDT) Received: from localhost ([2620:10d:c090:180::1:a245]) by smtp.gmail.com with ESMTPSA id x4-v6sm14573522pfm.119.2018.08.31.17.29.02 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 31 Aug 2018 17:29:03 -0700 (PDT) Date: Fri, 31 Aug 2018 17:29:00 -0700 From: Tejun Heo To: Dennis Zhou Cc: Jens Axboe , Johannes Weiner , Josef Bacik , kernel-team@fb.com, linux-block@vger.kernel.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 12/15] blkcg: cleanup and make blk_get_rl use blkg_lookup_create Message-ID: <20180901002900.GJ1488037@devbig004.ftw2.facebook.com> References: <20180831015356.69796-1-dennisszhou@gmail.com> <20180831015356.69796-13-dennisszhou@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180831015356.69796-13-dennisszhou@gmail.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Aug 30, 2018 at 09:53:53PM -0400, Dennis Zhou wrote: > From: "Dennis Zhou (Facebook)" > > blk_get_rl is responsible for identifying which request_list a request > should be allocated to. Try get logic was added earlier, but > semantically the logic was not changed. > > This patch makes better use of the bio already having a reference to the > blkg in the hot path. The cold path uses a better fallback of > blkg_lookup_create rather than just blkg_lookup and then falling back to > the q->root_rl. If lookup_create fails with anything but -ENODEV, it > falls back to q->root_rl. > > A clarifying comment is added to explain why q->root_rl is used rather > than the root blkg's rl. > > Signed-off-by: Dennis Zhou Acked-by: Tejun Heo We're replicating that retry busy loop a lot. It'd be really great to factor that out and document what it's doing. Thanks. -- tejun