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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id D51EDC433FE for ; Fri, 28 Jan 2022 09:38:10 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 188C16B0071; Fri, 28 Jan 2022 04:38:10 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 1399D6B0072; Fri, 28 Jan 2022 04:38:10 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0003D6B0073; Fri, 28 Jan 2022 04:38:09 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0160.hostedemail.com [216.40.44.160]) by kanga.kvack.org (Postfix) with ESMTP id E25CB6B0071 for ; Fri, 28 Jan 2022 04:38:09 -0500 (EST) Received: from smtpin19.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 9E898181CAEE1 for ; Fri, 28 Jan 2022 09:38:09 +0000 (UTC) X-FDA: 79079194698.19.8AA1A8F Received: from mail-vs1-f52.google.com (mail-vs1-f52.google.com [209.85.217.52]) by imf17.hostedemail.com (Postfix) with ESMTP id 5828540066 for ; Fri, 28 Jan 2022 09:38:08 +0000 (UTC) Received: by mail-vs1-f52.google.com with SMTP id l14so2279038vsm.3 for ; Fri, 28 Jan 2022 01:38:07 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=szeredi.hu; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=E/VIyc5JpK2Sy5loT9a2HcHWg2TrorJJxRaogeKP25w=; b=EibPllimp8WZIwxJdUGUIFAlIuZdyznPvrXJ7caP5EDkiBNUVM4ihiUoIfNxC6TVSx YE207qfvpl7N/VHWz1SefuMcAFD5mqGieRSegzXNyYGWfyIdkPkwWByrIvqWimbKQ8Un /lbUGxvPlDX06Jf/32nPUu5Q90vZSrQ0/ovfo= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=E/VIyc5JpK2Sy5loT9a2HcHWg2TrorJJxRaogeKP25w=; b=WmFAEySHPUtzD5bsYSU4+jKKtsoY86woCDdHHzZuU/OXEiASMavYvfNnYIzOc5E+eG VU2YIjLmnQ2iYe1nSW75iQmcQLz7hbPqgeHnZnRoidbOKMZ+0zWxYGiL6RbJkloNCVzp D0jD/W8csjX0VhWv7w9xrJYUczpmAoP998y/TsXjL8Ls+WxAyoHEJROm8IyDQ1KHSLld g2sSAbxKnGW4POljgUXNMYb6efGJ5NyXR1rtaBOahZttsmXnPu7rYo09SrB8hRP4E4fQ HITyLAgbX13XluZSwB264KNcPY7kPyFxD8NlF7ZIpPqQSz86HY+DgRtsHOMzleA8xaJu /LQA== X-Gm-Message-State: AOAM532B0dDbb1ak4eNoRtPnTYV43GCJCUilwn/9vVQu+0xn9ghsORIm cmLXGi/cfDyNoeTgGmbfWtmFUYaGvDZ22yn2JC0/Kg== X-Google-Smtp-Source: ABdhPJwGf3F8vVWMx/hAPOM/tzuC6mlnTkkNvV3zFtYKADK7sTRpnxjvKNE9DMzHauL+NEVwnl4j38I6/K9jRDhQk7E= X-Received: by 2002:a67:c390:: with SMTP id s16mr3769368vsj.61.1643362687362; Fri, 28 Jan 2022 01:38:07 -0800 (PST) MIME-Version: 1.0 References: <164325106958.29787.4865219843242892726.stgit@noble.brown> <164325158954.29787.7856652136298668100.stgit@noble.brown> In-Reply-To: <164325158954.29787.7856652136298668100.stgit@noble.brown> From: Miklos Szeredi Date: Fri, 28 Jan 2022 10:37:56 +0100 Message-ID: Subject: Re: [PATCH 1/9] Remove inode_congested() To: NeilBrown Cc: Andrew Morton , Jaegeuk Kim , Chao Yu , Jeff Layton , Ilya Dryomov , Trond Myklebust , Anna Schumaker , Ryusuke Konishi , "Darrick J. Wong" , Philipp Reisner , Lars Ellenberg , Paolo Valente , Jens Axboe , linux-mm , linux-nilfs@vger.kernel.org, Linux NFS list , linux-fsdevel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, Ext4 , ceph-devel@vger.kernel.org, drbd-dev@lists.linbit.com, linux-kernel@vger.kernel.org, linux-block@vger.kernel.org Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 5828540066 X-Stat-Signature: d347czazdzrgjibnmr9s9phkmof64te1 X-Rspam-User: nil Authentication-Results: imf17.hostedemail.com; dkim=none ("invalid DKIM record") header.d=szeredi.hu header.s=google header.b=EibPllim; spf=pass (imf17.hostedemail.com: domain of miklos@szeredi.hu designates 209.85.217.52 as permitted sender) smtp.mailfrom=miklos@szeredi.hu; dmarc=none X-HE-Tag: 1643362688-42200 X-Bogosity: Ham, tests=bogofilter, spamicity=0.002518, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, 27 Jan 2022 at 03:47, NeilBrown wrote: > > inode_congested() reports if the backing-device for the inode is > congested. Few bdi report congestion any more, only ceph, fuse, and > nfs. Having support just for those is unlikely to be useful. > > The places which test inode_congested() or it variants like > inode_write_congested(), avoid initiating IO if congestion is present. > We now have to rely on other places in the stack to back off, or abort > requests - we already do for everything except these 3 filesystems. > > So remove inode_congested() and related functions, and remove the call > sites, assuming that inode_congested() always returns 'false'. Looks to me this is going to "break" fuse; e.g. readahead path will go ahead and try to submit more requests, even if the queue is getting congested. In this case the readahead submission will eventually block, which is counterproductive. I think we should *first* make sure all call sites are substituted with appropriate mechanisms in the affected filesystems and as a last step remove the superfluous bdi congestion mechanism. You are saying that all fs except these three already have such mechanisms in place, right? Can you elaborate on that? Thanks, Miklos