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 E120FC77B7A for ; Tue, 23 May 2023 03:31:18 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 4AA89900003; Mon, 22 May 2023 23:31:18 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 456F5900002; Mon, 22 May 2023 23:31:18 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 34622900003; Mon, 22 May 2023 23:31:18 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 258AA900002 for ; Mon, 22 May 2023 23:31:18 -0400 (EDT) Received: from smtpin17.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id B466E120647 for ; Tue, 23 May 2023 03:31:17 +0000 (UTC) X-FDA: 80820094194.17.18BFE2D Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf17.hostedemail.com (Postfix) with ESMTP id 51BE340008 for ; Tue, 23 May 2023 03:31:14 +0000 (UTC) Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=HROkOeYJ; dmarc=none; spf=none (imf17.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1684812675; 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:dkim-signature; bh=/hND79jypjGMxrh+L0AHfmoXlB7jfnZF846f0hmvk3s=; b=MNh4O9P7jXzq58dGfi2R12l5yedrRmatjfgGvZqw0ZVnqq1euBjzXaTcymsNuL506ABj32 4/J5G+PgU91zHRaocuSE+nnrRoIylDQEDHuxI4HOfOGv1nxqTL3JhZYPzEXsSyqAVTaWkl dqhrKRM9YfZzF29k3PmDdUE78TVrTaE= ARC-Authentication-Results: i=1; imf17.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=HROkOeYJ; dmarc=none; spf=none (imf17.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1684812675; a=rsa-sha256; cv=none; b=NRVl5jozadpUYLRRKui6jiPLh/y4AfX1FCDpKRJsclKC6ECD5N0dqj6BiC5/FhON9rZRs4 6xwRthPQSQQwq8TJnjicjaR/3/Up2eh0+icbTU0oqnynqqAG0Vh/7LDK8CF2sSr3tHj7Hj J7A4yp/vSjq3tnYny5Q6SN/C8hAGDOE= DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=/hND79jypjGMxrh+L0AHfmoXlB7jfnZF846f0hmvk3s=; b=HROkOeYJgsW515w412weVmp0+i YEdCM3PRHJ8yLIzdBSb+Xne+pGdopXsi8JnT0CNNfg9oYv05lkYp5Nceqaag93z1O8A122qkxCVFv +izmJgPDGdRSRSfuroAjrwUvFuFU9Sr+1LDaSOnQuHT4rkaVFrGW9ZqvWG2nbNXKaUr5oZDVJK11I RyvLNOj1PcX4LwBEV/FegrIgbBdhvp7j2y31h8Wy7rSvHujrlGbNAYVSA0t7gLYx6nDhZYo2aTnwG 2e2CzusZB4FwcCAcoisC1TopNtNPBuTbaa+4Xz1KrGZTS3PUwYf30EPvOgjalWOatycvM59In4SD4 sazxHniQ==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1q1Ijb-009k51-9e; Tue, 23 May 2023 03:30:51 +0000 Date: Tue, 23 May 2023 04:30:51 +0100 From: Matthew Wilcox To: "Darrick J. Wong" Cc: Christoph Hellwig , Jens Axboe , Xiubo Li , Ilya Dryomov , Alexander Viro , Christian Brauner , Theodore Ts'o , Jaegeuk Kim , Chao Yu , Miklos Szeredi , Andreas Gruenbacher , Trond Myklebust , Anna Schumaker , Damien Le Moal , Andrew Morton , linux-block@vger.kernel.org, ceph-devel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, "open list:F2FS FILE SYSTEM" , cluster-devel@redhat.com, linux-xfs@vger.kernel.org, linux-nfs@vger.kernel.org, linux-mm@kvack.org, NeilBrown Subject: Re: [PATCH 08/13] iomap: assign current->backing_dev_info in iomap_file_buffered_write Message-ID: References: <20230519093521.133226-1-hch@lst.de> <20230519093521.133226-9-hch@lst.de> <20230523010627.GD11598@frogsfrogsfrogs> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230523010627.GD11598@frogsfrogsfrogs> X-Rspamd-Queue-Id: 51BE340008 X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: 9wzooioftw5j3i1icrowcu1r4td8higc X-HE-Tag: 1684812674-576919 X-HE-Meta: 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 /ZlwEgNn m/jmFrJ6Zm8Kr1oj3KY4NpX6AsSwdB53f2z5gsxn4/0buwfrAwjd48LxnsR+I8G1vDX0zKmviUT0bZRkSZFXyKN19ymbJkTHdgr0VKxTip2Z43iLl5UlC6iQcSpsPLVFxGEKNAMv/mDqKD0KWv92IVUqdaeDCGBl2FdK35HRgGHL9A2g4UWJPyrKABw== 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 22, 2023 at 06:06:27PM -0700, Darrick J. Wong wrote: > On Fri, May 19, 2023 at 11:35:16AM +0200, Christoph Hellwig wrote: > > Move the assignment to current->backing_dev_info from the callers into > > iomap_file_buffered_write to reduce boiler plate code and reduce the > > scope to just around the page dirtying loop. > > > > Note that zonefs was missing this assignment before. > > I'm still wondering (a) what the hell current->backing_dev_info is for, > and (b) if we need it around the iomap_unshare operation. > > $ git grep current..backing_dev_info [results show it only set, never used] > > AFAICT nobody uses it at all? Unless there's some bizarre user that > isn't extracting it from @current? > > Oh, hey, new question (c) isn't this set incorrectly for xfs realtime > files? Some git archaelogy ... This was first introduced in commit 2f45a06517a62 (in the linux-fullhistory tree) in 2002 by one Andrew Morton. At the time, it added this check to the page scanner: + if (page->pte.direct || + page->mapping->backing_dev_info == + current->backing_dev_info) { + wait_on_page_writeback(page); + } AFAICT (the code went through some metamorphoses in the intervening twenty years), the last use of it ended up in current_may_throttle(), and it was removed in March 2022 by Neil Brown in commit b9b1335e6403. Since then, there have been no users of task->backing_dev_info, and I'm pretty sure it can go away.