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=-0.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no 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 2D42DC3A589 for ; Thu, 15 Aug 2019 19:08:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 00DEC2084D for ; Thu, 15 Aug 2019 19:08:49 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=android.com header.i=@android.com header.b="Jut1zz1y" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731261AbfHOTIt (ORCPT ); Thu, 15 Aug 2019 15:08:49 -0400 Received: from mail-lf1-f65.google.com ([209.85.167.65]:46542 "EHLO mail-lf1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729084AbfHOTIt (ORCPT ); Thu, 15 Aug 2019 15:08:49 -0400 Received: by mail-lf1-f65.google.com with SMTP id n19so2334953lfe.13 for ; Thu, 15 Aug 2019 12:08:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=android.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=WtoUQYFY0uJJ3wOUCkGhLyCOVfAV5E4kawG+f5hhH90=; b=Jut1zz1ynCHITNpZDyG7heTK6Oosdj3wHGtuk4iLdGlssew6Ncow55oVkSL3D0XCHQ QfC/wG6bIEvbC/Ig/BH5Qad/zewyYYD8MyjXYqDA9Q61BJqL8/viXT2Ux7XegrQxbceb ttOmE+FpoKCUbpe9133QnM0k4r11hbWd+wUjoFzmpe5gyjdo6yJpVl6LvUJM91Foem89 2QBvNnE4D7b4jzkJJZJabtRZtK7yA3FKZ560skQDXrFddcT4A0jzPtmCDDgdh9AZSV/U XdVAnY/Lc0FlNxFrAEmXU1ZrpUOcdpXqiwr4KiwdJiVJk4ynZQkWcG65tEnyLP/qrqYz No7g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=WtoUQYFY0uJJ3wOUCkGhLyCOVfAV5E4kawG+f5hhH90=; b=hBrZdrTzo8BddHEymN0jOdhu4nRIMePA02czgFYzDJ6A+M7SO4qPCOOYn68uKCo7B8 pTxXFlUIA/tVAkVKSihKAfQFrcj0NVQCfjdB9z1r1ZNSkkOAP1md1EHeUWNf0MN21Zdk BbadGzCQ8f6o7wZ8IrHVA2wo5+DyebgZMXkXpi9vrOVpNLyQg82HjTSZBlT+AzN7UcSd MXJOOihOW3NDI8RG8vWczfMmqlPz2Hpg7i0JE9gcO4iG3zFIAcXtcEt1SUYY/v8Rl55c EwYNmvwbp8UiKn9Cp/64KlpnU+g6JqdhrKsc7BjELoZf7hZHUJWYXlzTLvNuR52hDHW6 zWCQ== X-Gm-Message-State: APjAAAXQ/qVXOqpdAQKWINj11q9UyVe8acOOniH71zUU8/MJk+Yp6Ii2 Cfti1S6i2LFW06ZT24mGyQlZBiv7yTuAsqM4VHLM2Q== X-Google-Smtp-Source: APXvYqwsZVdr/o1b7op1uwOOb4KPrSFVcPJXTgPSI/9f3jGISy0c+hLJ/pF5DDu2LIuUDxp6R+/7CZLmBMIWn8EY1HE= X-Received: by 2002:ac2:4ac4:: with SMTP id m4mr3109014lfp.172.1565896127099; Thu, 15 Aug 2019 12:08:47 -0700 (PDT) MIME-Version: 1.0 References: <20190814103244.92518-1-maco@android.com> <20190814113348.GA525@ming.t460p> <20190814114646.GA14561@ming.t460p> In-Reply-To: From: Martijn Coenen Date: Thu, 15 Aug 2019 21:08:36 +0200 Message-ID: Subject: Re: [PATCH] RFC: loop: Avoid calling blk_mq_freeze_queue() when possible. To: Ming Lei Cc: Ming Lei , Jens Axboe , linux-block , LKML , Greg KH , kernel-team@android.com, Narayan Kamath , Dario Freni , Nikita Ioffe , Jiyong Park , Martijn Coenen Content-Type: text/plain; charset="UTF-8" Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Thu, Aug 15, 2019 at 6:34 PM Ming Lei wrote: > If nothing will change, why does the userspace bother to send > SET_STATUS? We don't change transfer, but we do change the offset and sizelimit. In our specific case, we know there won't be any I/O from userspace at this point; so from that point of view the freeze wouldn't be necessary. But I'm not sure how we can make loop aware of that in a safe way. Ideally we'd just have a way of completely configuring a loop device before starting the block request queue, but that seems like a pretty big change. Martijn > > > Thanks, > Ming Lei