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 BB79BC7EE23 for ; Tue, 30 May 2023 23:54:52 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 13961900002; Tue, 30 May 2023 19:54:52 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 0EA3A6B0074; Tue, 30 May 2023 19:54:52 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id EF3AC900002; Tue, 30 May 2023 19:54:51 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id DF9D96B0072 for ; Tue, 30 May 2023 19:54:51 -0400 (EDT) Received: from smtpin17.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id AE01FAE358 for ; Tue, 30 May 2023 23:54:51 +0000 (UTC) X-FDA: 80848579182.17.AFF1569 Received: from mail-qt1-f173.google.com (mail-qt1-f173.google.com [209.85.160.173]) by imf23.hostedemail.com (Postfix) with ESMTP id B26FA14001F for ; Tue, 30 May 2023 23:54:49 +0000 (UTC) Authentication-Results: imf23.hostedemail.com; dkim=pass header.d=cmpxchg-org.20221208.gappssmtp.com header.s=20221208 header.b=P4EcgYkC; dmarc=pass (policy=none) header.from=cmpxchg.org; spf=pass (imf23.hostedemail.com: domain of hannes@cmpxchg.org designates 209.85.160.173 as permitted sender) smtp.mailfrom=hannes@cmpxchg.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1685490889; a=rsa-sha256; cv=none; b=mvGYkfC+dDcGbjQQ3BRak8F9WKDMxNGprEbA+lHMJ7Tmb5iJp71MnfQqZRJ0xEApS/FvYn vG4Hv4jeKffDbcBzZOlB5eW13P9Vwj9U5wjHrLybnX4z5QvR8I3EhWWReizO3tebIFM3d+ NhrANG+e8UWv0tegdGhgib8qgUA8vQk= ARC-Authentication-Results: i=1; imf23.hostedemail.com; dkim=pass header.d=cmpxchg-org.20221208.gappssmtp.com header.s=20221208 header.b=P4EcgYkC; dmarc=pass (policy=none) header.from=cmpxchg.org; spf=pass (imf23.hostedemail.com: domain of hannes@cmpxchg.org designates 209.85.160.173 as permitted sender) smtp.mailfrom=hannes@cmpxchg.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1685490889; 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=egonHliL0X+PhNSvnZlUOZqOsOTQyugVPFh8DdfCZ20=; b=1lfCRvZ6uFnXDEV4YhFBWHlegFx48vSjKu6AEAqtiTJByV4JoZgtabvfOxDDh+6yJq03fO BqFWEaUmQce/DyTkapUfm6ZyEKPdBQeSTJ96atjbDXfzfAgVs/7af8NDBGXRPGRX3D1Uk1 1PfMgQYWhOQMoRFUcbxtbwm2U5iZcsE= Received: by mail-qt1-f173.google.com with SMTP id d75a77b69052e-3f6b24467deso27601941cf.1 for ; Tue, 30 May 2023 16:54:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cmpxchg-org.20221208.gappssmtp.com; s=20221208; t=1685490889; x=1688082889; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=egonHliL0X+PhNSvnZlUOZqOsOTQyugVPFh8DdfCZ20=; b=P4EcgYkCe3WPJDm6MXwEAxb4UbGk2nUKlRxx2Ey9gdMpYWDKI4iaSshcyPgqBLFlZZ YBcMPOvEEPwoCk20+ZTWluhBnn+mLQ37bYJbkhBVMRuOnCutXR/UsnQ92jAIfB14kFCI Q5Uh+VFAAYXsAXZaGXgTEB8UWEn8cla5NP1UzH0QFed+3e73Doz0E1bxcuEaN3zajiDS foX5baIQpGNJLosCWT/k+Tp6b+OVYrhiSHK+7/8FQELWMrOtwIAKMFk6RxX14H2gpL9X a1mNnivdxrbtAPD+yHlbpdJF6SBpNelg+i2oqPC1Bkn5byS+Yf2pxiikKKqNbaOqpV7g yzXQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1685490889; x=1688082889; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=egonHliL0X+PhNSvnZlUOZqOsOTQyugVPFh8DdfCZ20=; b=mCB7KcQ7kRuV8dJ1ca9b+N/gaWIyFvLDiuJJJuxnwW8NeCHBm3Nae00YwngcqzpUV5 iopUXK8xES5kXOlRslQn31+Ut/e1BMjjHXbdlplSXc5yrupP4LYnrx7an/cPI4xu0Ut9 47fXvWOGNGIbr1rsSsNUD6BzmGK2f6wAUBSS9QkTc/RbxG21u0dRXo0slZEBajIXROnG 9x6VK+jFvTnZOD77vowhHyaaUucnY2Z3ZoTYLVPZoKk7dpXCvJbVNJIumnPMCtXThQXJ 8cq7xgz7qeJUq4nvdr6rjWop7GWgVjqNnH3Ho9sQAYJBdzGPwuKcmlxe4lIW7VMw064G 0mKQ== X-Gm-Message-State: AC+VfDwFLLgEpJg1EAhq1rLo9PISDnl8YsCfzTz069vdZP0oq+dSVRUl N/xaRuMOCyT02ERF9INsRnc8OA== X-Google-Smtp-Source: ACHHUZ49fFO7aKT0uDHqtFxnSbOV7EgxqJVMEueZvO1Uex0RJBiEL6n+MBPNRpenvsjbBwecqZI9lA== X-Received: by 2002:a05:622a:199b:b0:3f6:ba82:f24d with SMTP id u27-20020a05622a199b00b003f6ba82f24dmr3841966qtc.31.1685490888795; Tue, 30 May 2023 16:54:48 -0700 (PDT) Received: from localhost ([2620:10d:c091:400::5:8bb6]) by smtp.gmail.com with ESMTPSA id k3-20020ac84783000000b003f7fd3ce69fsm5167965qtq.59.2023.05.30.16.54.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 30 May 2023 16:54:48 -0700 (PDT) Date: Tue, 30 May 2023 19:54:47 -0400 From: Johannes Weiner To: Yosry Ahmed Cc: Konrad Rzeszutek Wilk , Andrew Morton , Seth Jennings , Dan Streetman , Vitaly Wool , Nhat Pham , Domenico Cerasuolo , Yu Zhao , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: zswap: support exclusive loads Message-ID: <20230530235447.GB102494@cmpxchg.org> References: <20230530210251.493194-1-yosryahmed@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230530210251.493194-1-yosryahmed@google.com> X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: B26FA14001F X-Stat-Signature: f85obzqjb1eicg6r64h7h6x56xzwmwdy X-HE-Tag: 1685490889-661202 X-HE-Meta: U2FsdGVkX19aq60v4d2xMGypSCEdDz1+JJ5Aw0vMTdpiCy33+z2+VUWP5eXeDqIyFE4H/JzGk/IDYDbfPfYv5KrbarZ4as4ZKkNAsNZY5/XwXnzeT1ug33U16wk/dyxqYRpPGdEMNjDHjhtIj//JoLo2OMAp2z+cmVoqqSROrJztfvPRnKKYjTpyVdOPiqwbkSdjl06cW/uMk30ZwFPrIHtPzOXFXBKSb6bDbGd9DIuFwSx4IPXMvLlIl0YrXcPoALAm/zKyPh7yz89c2SBO9y1xF8KmHiWEDnEqcBPGWR5LgYO16rW7PSfJOB+/DKnO1C5rD5arjzpqScz8goRBfTr7g+8qmVzuKiH9unT6MvYVWQwzTq4nidI1q0URzFfxCNZixEV1YKEmm5X+O57RLbe7AUjCYpna920CFD2Y64hArNxRYR0H/5NKvEXU3oGncuzNoH6zma4noTRA2olciG1dqZxpmVakjSSJjGKGGP9TIbMoneZLoVHdsuSpsF/SMxtYaWtJRYQcvrVfvrgwStgKCvxY6N79OOjGM58eGjUHRWRApyb7rYnt/TljoKsfotLcGyWclK9yBKShtS2LEEHL05xbHfFtSDFAImHC5Kcjt+1X/fSDTCWt4j90UtiZDccrNWQUmHucWQEUvAZwP8Ry1jx+Dr5rOTRAn/3b3KeD+vO2mIFsz3QbCikdE7DMPHsCse6EXJPH8RKxw0YQ3oymvw6kqgR5tSDl/3BbSNWD4HWuNRto3t+YtvDmgaMVc0j9qI82ZkEForAB1O/47EvoO68RQwn6Mn+4Vctv0rP3zqZr3/Xw7tGxW1AdzkJLmX/8B/gncD7p+FTf8TyyI5rfCf3JlN/sZRSW0b0a5FxPaqab0Qj7hBHbwgzptsg4WJVy00GWjNkv07/fH8MRbKRqc2aFtDpw64zNAG/tevsH2yi61QbXhSFaObZgCIoRftzQJFZYJwrjp6tmIrW nksqkhbS 2XlW/UcMYzycqLtvon55Zhr5MOdCcG4Kd4kHLeFHDDExrRohOQhnw6fGZaYRvc1obM1ni4jqTegnNeo6UB/Fgdxy0bQ2J7pr0toDQdGhMBKH90jqAhoLNU0yoE7gg49L5tH3dom4A0yvQnJ+BLHDfG9/uGZBuvm3SeYnlZjMi7bEHYJaj/6raoGeMAW52xO1j2JfMbfz7Y2GBaEqU7qUCPGBUgMbeyGJqNPdO27gSHcho06v9B93ozjHcwEZtCDBlszg3hw+fLnETOjRkfq5MqbCkuE7TBWr75c27+o1bt37iO6iT/c7pURkWv7RquHvrejHtrc/uplvgHFqw1gLZrD1+0HQ51s0wQvrXq4cOtrbYa27ROyR0ta85S/tLswATXXfQgmOASSBjIVgXHuliZ3vYgbSWLsgw+LYQZvmiLVT6QNE= 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 Tue, May 30, 2023 at 09:02:51PM +0000, Yosry Ahmed wrote: > @@ -216,8 +216,13 @@ int __frontswap_load(struct page *page) > > /* Try loading from each implementation, until one succeeds. */ > ret = frontswap_ops->load(type, offset, page); > - if (ret == 0) > + if (ret == 0) { > inc_frontswap_loads(); > + if (frontswap_ops->exclusive_loads) { > + SetPageDirty(page); > + __frontswap_clear(sis, offset); > + } Somewhat tangential, but is there still a point to the frontswap layer? It seems usecases other than zswap have never materialized, at least not in tree. Life would be a lot easier if we were to just hardcode the zswap callbacks in the swap functions. It's not the patch's fault, but it highlights the boiler plate the indirection causes. ->load() already has the page and could just dirty it directly. Instead now both layers have to handle invalidation, which is a vector for bugs. Can somebody think of reasons to keep it? If not, I'd take a stab at removing it.