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=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 6BEDCCA9EC5 for ; Wed, 30 Oct 2019 17:47:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3892C208E3 for ; Wed, 30 Oct 2019 17:47:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1572457638; bh=sjprPqg2PbaiKLXjdDkpF8WMp02FewdHM7IhqCH/KBY=; h=Date:From:To:Subject:References:In-Reply-To:List-ID:From; b=P2bXM1fu/C+YcxeJvC0ZxZC+1Nv4nP4J9BPoqOsk75iGFdui7Uo+h4JqCJJsNOjAv m57rfEaSKf95GQFQEu4sCy1p2O/Lbtoj3K1FLWxoI1ijAn/nv/uJin/ObIYTv+PXa7 r6P3wzxWHdqsrjVNTdI1QiGLEwpTmvjT3NQMJoaA= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727427AbfJ3RrR (ORCPT ); Wed, 30 Oct 2019 13:47:17 -0400 Received: from mail.kernel.org ([198.145.29.99]:37612 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726664AbfJ3RrQ (ORCPT ); Wed, 30 Oct 2019 13:47:16 -0400 Received: from localhost (unknown [104.132.0.81]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 9DB3820659; Wed, 30 Oct 2019 17:47:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1572457635; bh=sjprPqg2PbaiKLXjdDkpF8WMp02FewdHM7IhqCH/KBY=; h=Date:From:To:Subject:References:In-Reply-To:From; b=qvf5Q3NhTT110wh2br44Y/15LJDDHIw6tTyaIc8WfsAp9TgtRSJZq1Mq29zfD47I5 Bgnzk6Iyez0hE4pGF4Iy/UfvI8iffKZxEG3+J1wiKpGuajR11oficmHqOe2eYmZDjH GA2kpzpig2Q225fjWLu+HBSsUUk0UnkPOJfub28Y= Date: Wed, 30 Oct 2019 10:47:14 -0700 From: Jaegeuk Kim To: Chao Yu , linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net Subject: Re: [PATCH 2/2] f2fs: support data compression Message-ID: <20191030174714.GA36729@jaegeuk-macbookpro.roam.corp.google.com> References: <20191022171602.93637-1-jaegeuk@kernel.org> <20191022171602.93637-2-jaegeuk@kernel.org> <20191027225006.GA321938@sol.localdomain> <20191030025512.GA4791@sol.localdomain> <97c33fa1-15af-b319-29a1-22f254a26c0a@huawei.com> <20191030165056.GA693@sol.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191030165056.GA693@sol.localdomain> User-Agent: Mutt/1.8.2 (2017-04-18) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/30, Eric Biggers wrote: > On Wed, Oct 30, 2019 at 04:43:52PM +0800, Chao Yu wrote: > > On 2019/10/30 10:55, Eric Biggers wrote: > > > On Tue, Oct 29, 2019 at 04:33:36PM +0800, Chao Yu wrote: > > >> On 2019/10/28 6:50, Eric Biggers wrote: > > >>>> +bool f2fs_is_compressed_page(struct page *page) > > >>>> +{ > > >>>> + if (!page_private(page)) > > >>>> + return false; > > >>>> + if (IS_ATOMIC_WRITTEN_PAGE(page) || IS_DUMMY_WRITTEN_PAGE(page)) > > >>>> + return false; > > >>>> + return *((u32 *)page_private(page)) == F2FS_COMPRESSED_PAGE_MAGIC; > > >>>> +} > > >>> > > >>> This code implies that there can be multiple page private structures each of > > >>> which has a different magic number. But I only see F2FS_COMPRESSED_PAGE_MAGIC. > > >>> Where in the code is the other one(s)? > > >> > > >> I'm not sure I understood you correctly, did you mean it needs to introduce > > >> f2fs_is_atomic_written_page() and f2fs_is_dummy_written_page() like > > >> f2fs_is_compressed_page()? > > >> > > > > > > No, I'm asking what is the case where the line > > > > > > *((u32 *)page_private(page)) == F2FS_COMPRESSED_PAGE_MAGIC > > > > > > returns false? > > > > Should be this? > > > > if (!page_private(page)) > > return false; > > f2fs_bug_on(*((u32 *)page_private(page)) != F2FS_COMPRESSED_PAGE_MAGIC) > > return true; > > Yes, that makes more sense, unless there are other cases. > > > > > > > > >>> > > >>>> + > > >>>> +static void f2fs_set_compressed_page(struct page *page, > > >>>> + struct inode *inode, pgoff_t index, void *data, refcount_t *r) > > >>>> +{ > > >>>> + SetPagePrivate(page); > > >>>> + set_page_private(page, (unsigned long)data); > > >>>> + > > >>>> + /* i_crypto_info and iv index */ > > >>>> + page->index = index; > > >>>> + page->mapping = inode->i_mapping; > > >>>> + if (r) > > >>>> + refcount_inc(r); > > >>>> +} > > >>> > > >>> It isn't really appropriate to create fake pagecache pages like this. Did you > > >>> consider changing f2fs to use fscrypt_decrypt_block_inplace() instead? > > >> > > >> We need to store i_crypto_info and iv index somewhere, in order to pass them to > > >> fscrypt_decrypt_block_inplace(), where did you suggest to store them? > > >> > > > > > > The same place where the pages are stored. > > > > Still we need allocate space for those fields, any strong reason to do so? > > > > page->mapping set implies that the page is a pagecache page. Faking it could > cause problems with code elsewhere. I've checked it with minchan, and it seems to be fine that filesystem uses this page internally only, not in pagecache. > > > > > > >>>> + > > >>>> +void f2fs_destroy_compress_ctx(struct compress_ctx *cc) > > >>>> +{ > > >>>> + kvfree(cc->rpages); > > >>>> +} > > >>> > > >>> The memory is allocated with kzalloc(), so why is it freed with kvfree() and not > > >>> just kfree()? > > >> > > >> It was allocated by f2fs_*alloc() which will fallback to kvmalloc() once > > >> kmalloc() failed. > > > > > > This seems to be a bug in f2fs_kmalloc() -- it inappropriately falls back to > > > kvmalloc(). As per its name, it should only use kmalloc(). f2fs_kvmalloc() > > > already exists, so it can be used when the fallback is wanted. > > > > We can introduce f2fs_memalloc() to wrap f2fs_kmalloc() and f2fs_kvmalloc() as > > below: > > > > f2fs_memalloc() > > { > > mem = f2fs_kmalloc(); > > if (mem) > > return mem; > > return f2fs_kvmalloc(); > > } > > > > It can be used in specified place where we really need it, like the place > > descirbied in 5222595d093e ("f2fs: use kvmalloc, if kmalloc is failed") in where > > we introduced original logic. > > No, just use kvmalloc(). The whole point of kvmalloc() is that it tries > kmalloc() and then falls back to vmalloc() if it fails. > > - Eric