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 X-Spam-Level: X-Spam-Status: No, score=-1.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FSL_HELO_FAKE,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7C039C2BB55 for ; Fri, 10 Apr 2020 23:11:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5058F2145D for ; Fri, 10 Apr 2020 23:11:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1586560305; bh=FfeNCoXmIijEfyR1pkNRajhg9ViX3TUxB3mbIz62Sms=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=bab7PaeFJdnbek5CMW3NPDIiN9V6wEvdadaAdUo6Af4tBQloALUKZgW8aD6I5HAhr bv/qe7hFrHL2GLEyzIoWyOPPQs397w2b2aQJasZPs+aEuVmMHahgLKYYA4AEBOGfdS N47HbP6UdPwVWqaEk5afKT3kdbx4wJz7D75PTOJM= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726652AbgDJXLm (ORCPT ); Fri, 10 Apr 2020 19:11:42 -0400 Received: from mail-pj1-f66.google.com ([209.85.216.66]:53525 "EHLO mail-pj1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726582AbgDJXLm (ORCPT ); Fri, 10 Apr 2020 19:11:42 -0400 Received: by mail-pj1-f66.google.com with SMTP id cl8so109435pjb.3; Fri, 10 Apr 2020 16:11:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=bQcdpto7s/yGk2w0OzvQ6UptVyKViN3oMFbbBVW84wQ=; b=q7YTOEbnyV60h/2JZUSD3yvsv3FfYyTmAHedS5dXvC6eEJqoWdAqQM8fRMbYNEb/DL TWa8f1bEPIXO2DpHtzWmZ1hQdADUheduicV44X6NhmrZnsTNDIZa9VTHkg2rqK9WXs9O CtfQg7RxKV1aU+9PajTKBmDFHloR88hUsjTCxairuAofrjSvkiIjlmrksHhAsr4eSull P/eN5aSURPoT5uOWbLvn9TO2HAsL3MlV2FT0WDF8H+ov5BHzMNCa3A04caDPl50c1Iqw Q60AlHo9v7XVZ5xht9Dtvdi6fj0cEQuu9XG4/VxucECmylB5pc3N/jO1PdzV7ryJfNk2 odzQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to; bh=bQcdpto7s/yGk2w0OzvQ6UptVyKViN3oMFbbBVW84wQ=; b=jFjuvyzg8iHEn0BzyXsyOcuMX+9/ulPTf8RuLKDgxteAeIWT3kPyc6Vvt8lhhKq4EM 5H22CXcPxBL5U5vXSljQ+6okr3V4GTlyg88ZPLWhTJKh/N3uLtJOrd8fd2Fs0wXy7l2a 14XQHNKslSG003xjm4riGXvGyoboJCUOplKBF1SYU3GBhw/tUb8I53U7R1lN5hyTS6sn vx39QM2Vi4+onOHVWFq7B7QG/eeksxGzne3KkQo/CwJgwHvnXbHyBhBNDct/qrhjWOhP f2psHDCGqcCdUU4OiTqtnGEmRUzFBcvBKAn5rO63gM0c2qM52nbhrps1ZfzAwQKHnMRU DjBw== X-Gm-Message-State: AGi0PubCEw3nWKBkKxeofpAlyUv341TQbMzuDHi9gRHEhFOwnwP9ERWb 9E5LgX7ZErVLKrbyhrn2Aj0= X-Google-Smtp-Source: APiQypIEPforRWpT0WXypxL4A3ey15BGc+kDge0iIn1cftbyny3ESjfu/Br0BZMCFGD2PtWlRrOKew== X-Received: by 2002:a17:902:b409:: with SMTP id x9mr6968379plr.125.1586560301031; Fri, 10 Apr 2020 16:11:41 -0700 (PDT) Received: from google.com ([2601:647:4001:3000::50e3]) by smtp.gmail.com with ESMTPSA id 15sm2629073pfu.186.2020.04.10.16.11.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 10 Apr 2020 16:11:39 -0700 (PDT) Date: Fri, 10 Apr 2020 16:11:36 -0700 From: Minchan Kim To: Sergey Senozhatsky Cc: Peter Zijlstra , Christoph Hellwig , Andrew Morton , "K. Y. Srinivasan" , Haiyang Zhang , Stephen Hemminger , Wei Liu , x86@kernel.org, David Airlie , Daniel Vetter , Laura Abbott , Sumit Semwal , Sakari Ailus , Nitin Gupta , Robin Murphy , Christophe Leroy , linuxppc-dev@lists.ozlabs.org, linux-hyperv@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, iommu@lists.linux-foundation.org, linux-arm-kernel@lists.infradead.org, linux-s390@vger.kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 10/28] mm: only allow page table mappings for built-in zsmalloc Message-ID: <20200410231136.GA101325@google.com> References: <20200408115926.1467567-1-hch@lst.de> <20200408115926.1467567-11-hch@lst.de> <20200409160826.GC247701@google.com> <20200409165030.GG20713@hirez.programming.kicks-ass.net> <20200409170813.GD247701@google.com> <20200410023845.GA2354@jagdpanzerIV.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200410023845.GA2354@jagdpanzerIV.localdomain> Sender: linux-hyperv-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-hyperv@vger.kernel.org Hi Sergey, On Fri, Apr 10, 2020 at 11:38:45AM +0900, Sergey Senozhatsky wrote: > On (20/04/09 10:08), Minchan Kim wrote: > > > > Even though I don't know how many usecase we have using zsmalloc as > > > > module(I heard only once by dumb reason), it could affect existing > > > > users. Thus, please include concrete explanation in the patch to > > > > justify when the complain occurs. > > > > > > The justification is 'we can unexport functions that have no sane reason > > > of being exported in the first place'. > > > > > > The Changelog pretty much says that. > > > > Okay, I hope there is no affected user since this patch. > > If there are someone, they need to provide sane reason why they want > > to have zsmalloc as module. > > I'm one of those who use zsmalloc as a module - mainly because I use zram > as a compressing general purpose block device, not as a swap device. > I create zram0, mkfs, mount, checkout and compile code, once done - > umount, rmmod. This reduces the number of writes to SSD. Some people use > tmpfs, but zram device(-s) can be much larger in size. That's a niche use > case and I'm not against the patch. It doesn't mean we couldn't use zsmalloc as module any longer. It means we couldn't use zsmalloc as module with pgtable mapping whcih was little bit faster on microbenchmark in some architecutre(However, I usually temped to remove it since it had several problems). However, we could still use zsmalloc as module as copy way instead of pgtable mapping. Thus, if someone really want to rollback the feature, they should provide reasonable reason why it doesn't work for them. "A little fast" wouldn't be enough to exports deep internal to the module. Thanks.