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 3B569C7EE23 for ; Tue, 30 May 2023 05:45:55 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 84FC2900002; Tue, 30 May 2023 01:45:54 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 7FF9E6B0074; Tue, 30 May 2023 01:45:54 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6EFCE900002; Tue, 30 May 2023 01:45:54 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id 5B70B6B0072 for ; Tue, 30 May 2023 01:45:54 -0400 (EDT) Received: from smtpin26.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 26E4AC0398 for ; Tue, 30 May 2023 05:45:54 +0000 (UTC) X-FDA: 80845835028.26.FF9516B Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by imf03.hostedemail.com (Postfix) with ESMTP id 37E092001A for ; Tue, 30 May 2023 05:45:51 +0000 (UTC) Authentication-Results: imf03.hostedemail.com; dkim=none; spf=none (imf03.hostedemail.com: domain of hch@lst.de has no SPF policy when checking 213.95.11.211) smtp.mailfrom=hch@lst.de; dmarc=none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1685425552; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=kc+25sageEIi1fuaWIIhmhBkICxNJyZwRC5X4cr8XSk=; b=dpYbkdiqC4uDZEX93CaEMNvJx23Uiyn/Y/wXduVJu9o6ZkYymrS/PpeUUms/M7P71+nPU8 VH5m5lPtVRRgL3DS5kmQNwytMLM/d4zDTXqEMrPRqcVCSDWA3Z85n/PtIA1Bm+EZ+8NbEQ wku80zvBIXTuzKeXm5/IwAEFb7NyKJs= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1685425552; a=rsa-sha256; cv=none; b=pVUriIktG8DSHTVmZRDtmwjzQYBvJ8ViS01qO63mN5Y4qhjMnSZMsesD8qxOSCiO0wWsML j7OZF6uqifWzuB/rJW9vkOv2qb6eSFItm1ZfqzO1ezHlAw63Vk27iKIyq2srrIMWpzORuN ibu+Di1pOOE7llReN+jiTvHDULSe3ME= ARC-Authentication-Results: i=1; imf03.hostedemail.com; dkim=none; spf=none (imf03.hostedemail.com: domain of hch@lst.de has no SPF policy when checking 213.95.11.211) smtp.mailfrom=hch@lst.de; dmarc=none Received: by verein.lst.de (Postfix, from userid 2407) id 9EA0568B05; Tue, 30 May 2023 07:45:47 +0200 (CEST) Date: Tue, 30 May 2023 07:45:47 +0200 From: Christoph Hellwig To: David Sterba Cc: Christoph Hellwig , Chris Mason , Josef Bacik , David Sterba , linux-btrfs@vger.kernel.org, Matthew Wilcox , linux-mm@kvack.org Subject: Re: [PATCH 08/16] btrfs: stop setting PageError in the data I/O path Message-ID: <20230530054547.GA5825@lst.de> References: <20230523081322.331337-1-hch@lst.de> <20230523081322.331337-9-hch@lst.de> <20230529175210.GL575@twin.jikos.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230529175210.GL575@twin.jikos.cz> User-Agent: Mutt/1.5.17 (2007-11-01) X-Stat-Signature: emxp8k1uobgnsa99p36ngmdpnyxejepj X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 37E092001A X-Rspam-User: X-HE-Tag: 1685425551-839686 X-HE-Meta: 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 LmEkXwSC IHbZEf5fYzS35xVQcQlfsnX5MIP145ZLn3B0cuQkb3xVCyXLJ3iy0C2uNw5/MshbfINBnOqRO0fIJMWMnxRPDJvFrIRJ/UPy97JyRuqH5ywLooRI= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, May 29, 2023 at 07:52:10PM +0200, David Sterba wrote: > On Tue, May 23, 2023 at 10:13:14AM +0200, Christoph Hellwig wrote: > > PageError is not used by the VFS/MM and deprecated. > > Is there some reference other than code? I remember LSF/MM talks about > writeback, reducing page flags but I can't find anything that would say > that PageError is not used anymore. For such core changes in the > neighboring subysystems I kind of rely on lwn.net, hearsay or accidental > notice on fsdevel. > > Removing the Error bit handling looks overall good but I'd also need to > refresh my understanding of the interactions with writeback. willy is the driving force behind the PageErro removal, so maybe he has a coherent writeup. But the basic idea is: - page flag space availability is limited, and killing any one we can easily is a good thing - PageError is not well defined and not part of any VM or VFS contract, so in addition to freeing up space it also generally tends to remove confusion.