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 D0B88C3DA70 for ; Tue, 30 Jul 2024 15:54:26 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 664A66B0096; Tue, 30 Jul 2024 11:54:26 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 614F26B0098; Tue, 30 Jul 2024 11:54:26 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 5034F6B0099; Tue, 30 Jul 2024 11:54:26 -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 3367A6B0096 for ; Tue, 30 Jul 2024 11:54:26 -0400 (EDT) Received: from smtpin08.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id 6DC77403E3 for ; Tue, 30 Jul 2024 15:54:25 +0000 (UTC) X-FDA: 82396866090.08.3158A0C Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf16.hostedemail.com (Postfix) with ESMTP id 196FC180021 for ; Tue, 30 Jul 2024 15:54:22 +0000 (UTC) Authentication-Results: imf16.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=SSpK+W1k; spf=none (imf16.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org; dmarc=none ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1722354836; a=rsa-sha256; cv=none; b=zCf6Yauj/eUInXYFQ1kHxfEpspqv+ndTgZ+M9WpC6+UYDftEJrFUxuTZfWtQ8NN7fZ9vPn hlgpvyp0pGiVurNSGzkzdTRyakOMqPAx6A9urGzuvTPv4RyiRIIXJmq10ovnVW1rg2z4S6 xaLquCJwUp/3H3F5ZemYbBgm2gsacQU= ARC-Authentication-Results: i=1; imf16.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=SSpK+W1k; spf=none (imf16.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org; dmarc=none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1722354836; 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=6MXNumiKKmCQgh40ekmql/XajsTgk+xubikZMvobTSk=; b=OHkOhrknw5DySLEpc4wI7ce1wekLEiJ0ITtjOgCa4icy2vDLtoKbX6Jl8wB4yn88O9eK4N 2yWLxIE+LYB2KPqrju7vK+iDfIs7j19i7a4kCN5Ijdt6dSETEKBo96TtMNg/TsAqGWPvYF F5lpKtOwLop0EVSYiIu5ezSBrYerLZk= 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=6MXNumiKKmCQgh40ekmql/XajsTgk+xubikZMvobTSk=; b=SSpK+W1kp26+xjQWTTmaM5ZjCe 2XK+V9aC4beetwb6xvFEEtZM0tauZM5ADdlXygFQZYfY1sOVipzzth/ZEc5rMgn9g2gdx7K2PX4ZD 02XPutJJJFy3ehJQehM8oID2qMExXoI2bAN3xv/oazWG5i/jIAwnJjIfn9mFm7hzZcEk0xrLb9cnj 9RbYHYeYjw/GXs6q6v5Oansql87rCbU2OeqCa/Wj/6cu9tdFyhqgCseznNhe8ybtmWftvIyttUVF7 guJoQ5U6hGUmnfBws2Rw7OTuzPSr2N8gcX3iJQYJBWZXk2XQdstPHKE3oHPWK4dPb4D0gjKgHhkC9 HadHxXCw==; Received: from willy by casper.infradead.org with local (Exim 4.97.1 #2 (Red Hat Linux)) id 1sYpB5-0000000ErhA-2ZyA; Tue, 30 Jul 2024 15:54:19 +0000 Date: Tue, 30 Jul 2024 16:54:19 +0100 From: Matthew Wilcox To: Qu Wenruo Cc: Linux Memory Management List , linux-fsdevel@vger.kernel.org, "linux-btrfs@vger.kernel.org" Subject: Re: Forcing vmscan to drop more (related) pages? Message-ID: References: <7e68a0b2-0bee-4562-a29f-4dd7d8713cd9@gmx.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <7e68a0b2-0bee-4562-a29f-4dd7d8713cd9@gmx.com> X-Stat-Signature: t1cix4ex9gyqwzx9f77waj34rnaa19xd X-Rspamd-Queue-Id: 196FC180021 X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1722354862-271306 X-HE-Meta: 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 nkcgvnDK ti5yQn1TGAE++X62vqrP9S+SsBDTcE79enWmVKS2Vw/fuAt1O2Jfi6heJ3QlSwK71vUzRcg1u2C8YwWBFVipglX98wEEAuodJ6LDmDJ6ePIFPsqjRaUO869ID2vltBmoG3sr34xXxfy4Ye+zGYeUrFvexleqkgxGU7Y0ETU9bNgm6HIypJQTLF8D92fbvqrtCV9LMwc1oJslgs81JIUC3Z9s6sT4JdOD6MJneFsT6amt3rudlOlMHQmz2sYdsx4pOluPC 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: List-Subscribe: List-Unsubscribe: On Tue, Jul 30, 2024 at 03:35:31PM +0930, Qu Wenruo wrote: > Hi, > > With recent btrfs attempt to utilize larger folios (for its metadata), I > am hitting a case like this: > > - Btrfs allocated an order 2 folio for metadata X > > - Btrfs tries to add the order 2 folio at filepos X > Then filemap_add_folio() returns -EEXIST for filepos X. > > - Btrfs tries to grab the existing metadata > Then filemap_lock_folio() returns -ENOENT for filepos X. > > The above case can have two causes: > > a) The folio at filepos X is released between add and lock > This is pretty rare, but still possible > > b) Some folios exist at range [X+4K, X+16K) > In my observation, this is way more common than case a). > > Case b) can be caused by the following situation: > > - There is an extent buffer at filepos X > And it is consisted of 4 order 0 folios. > > - vmscan wants to free folio at filepos X > It calls into the btrfs callback, btree_release_folio(). > And btrfs did all the checks, release the metadata. > > Now all the 4 folios at file pos [X, X+16K) have their private > flags cleared. > > - vmscan freed folio at filepos X > However the remaining 3 folios X+4K, X+8K, X+12K are still attached > to the filemap, and in theory we should free all 4 folios in one go. > > And later cause the conflicts with the larger folio we want to insert. > > I'm wondering if there is anyway to make sure we can release all > involved folios in one go? > I guess it will need a new callback, and return a list of folios to be > released? I feel like we're missing a few pieces of this puzzle: - Why did btrfs decide to create four order-0 folios in the first place? - Why isn't there an EEXIST fallback from order-2 to order-1 to order-0 folios? But there's no need for a new API. You can remove folios from the page cache whenever you like. See delete_from_page_cache_batch() as an example.