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=-2.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, 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 084D9C48BE5 for ; Wed, 16 Jun 2021 17:36:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DE2D561055 for ; Wed, 16 Jun 2021 17:36:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230503AbhFPRiw (ORCPT ); Wed, 16 Jun 2021 13:38:52 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39302 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230291AbhFPRiv (ORCPT ); Wed, 16 Jun 2021 13:38:51 -0400 Received: from mail-ot1-x336.google.com (mail-ot1-x336.google.com [IPv6:2607:f8b0:4864:20::336]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9159BC061574 for ; Wed, 16 Jun 2021 10:36:44 -0700 (PDT) Received: by mail-ot1-x336.google.com with SMTP id w22-20020a0568304116b02904060c6415c7so3335131ott.1 for ; Wed, 16 Jun 2021 10:36:44 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:from:date:message-id:subject:to:cc; bh=WF2UEjVKOhuXNDjWMiYeFCQnPAAsctBC2eC+oTid+aY=; b=rhmTfw2fLsGLrlAFs/zO+R8OIYb1+Tio9MkfOH5Z3MOuIn3/ijZYkYAzd0YD8Cnuna QKvA9A7+J88jbNV/yHvOv9CyYVtu8e97wRn2ZSg2IVwfiqIFNkZti/Y1ORNJ0nkV0nUW /+zjbwDoUqRsVJLTCnRXnc8g6p5Lrf4CA7k77dlnz29HK4yCegZSvWhkVe67XLryAoH2 elrJshr/CqhD71Pij3tgg1ykVk8vAZ4JQjYRNEcIU6KCPd/5yB7MgHStfeP5M2qp+CFV j9ujLRzSC8a/sSozqH71Vy+zQlKY7sFVE1ADNhEbmO1tCtSabdkeuc60yzRzcEP5gkAT Hh1w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:from:date:message-id:subject:to:cc; bh=WF2UEjVKOhuXNDjWMiYeFCQnPAAsctBC2eC+oTid+aY=; b=Om0tBwgAvuUnyAlhPoIpiP+kfR5U5qnUqnIKhIYPhNz/W3rRU56uRgpFUlguV5P1gh sv6o4MZ+x9052LgUSza4awLtqa9U1EcZKHPcjAD2j9UDQ8iivTTOGxvL9hFHE+aqQqth p1THctuo+WSN69qsDh98z57QOF6sNQqOeC0t2vxd1Lsv2pJaxe8Pwb1tFzMztjyRumJl bvFVx4mlwhh4bbQWSuIMnE4fBXC+arCIlim7ApPDKx3yl5TTRU3VJoI7nfuL9868LCl+ TYYyMWZup1nsesiefoL/eDVzVolgz1f+ZEqu7BW2R5gN/UWHiirWnfdxNegipNcHScjP rjxQ== X-Gm-Message-State: AOAM533LO5nRK/xLpkyheduFGHW2hVaBo6jvxPEbwUeTpIYQV9dBXPzG Xsd6gM39YZrMM1mCRsLR9Vp3x7IPPAgvrJmnieQjc7/Kiz0= X-Google-Smtp-Source: ABdhPJz9Yys5cMMWHNQNmV/uQqZEoUISylrc8NRpD72j8aUj+PD/eKnfvWhP0sqT9SS1v+Vx4MYu18OFxMaS7C4zAvw= X-Received: by 2002:a05:6830:1f0a:: with SMTP id u10mr878018otg.181.1623865003470; Wed, 16 Jun 2021 10:36:43 -0700 (PDT) MIME-Version: 1.0 From: Omar Kilani Date: Wed, 16 Jun 2021 10:36:32 -0700 Message-ID: Subject: blk-wbt / wbt_rqw_done logic? To: linux-block@vger.kernel.org Cc: Jens Axboe Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Hi Jens, While looking into a deadlock that Jan has fixed: https://lore.kernel.org/linux-block/CA+8F9hggf7jOcGRxvBoa8FYxQs8ZV+XueVAd9BodpQQP_+8Pdw@mail.gmail.com/T/ I noticed this line of code in blk-wbt.c (L164): - if (!inflight || diff >= rwb->wb_background / 2) And based on the preceding logic calculating `limit` and the comment in the "no wakeup" check above which references "normal limit" and decides based on `limit`, it's not clear why `rwb->wb_background` is used here as there's no comment. Should this be: + if (!inflight || diff >= limit / 2) I traced the history of the line back to 4.20rc but it hasn't changed since being added. Thanks! Regards, Omar