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=-8.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 77CF2C433F5 for ; Sat, 4 Sep 2021 03:33:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 49B3A61054 for ; Sat, 4 Sep 2021 03:33:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233878AbhIDDeW (ORCPT ); Fri, 3 Sep 2021 23:34:22 -0400 Received: from mail.kernel.org ([198.145.29.99]:54782 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229596AbhIDDeT (ORCPT ); Fri, 3 Sep 2021 23:34:19 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id C813F6069E; Sat, 4 Sep 2021 03:33:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1630726398; bh=vDInDMJ4sMJnmqblJcXU0QqfdBm47jpBvsDvYyfEXBk=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=iraM5xTi9QjL341eo2RxFLV1aclSle5NhZTFsRGheHHVdZTduYXKuNdSs93EzOCVq 6o6+FQAhLcCmT3W0T8wEK22PEIG7H86pLQ40MeFVSBw9J4Z5FGZ4xhz1B96WQPzce3 5E2vDC0cVURUDAICMhdjbW0HBHLDiTu/f141xsy+q2kBL9cDHr+A8zZ64+gX1BYHye IMUPst2ejWYNR+S/B15UyKj/Qa8LhwCHXK9b9gsVfK6+ZpvqhSEMtHzxvusaldthus QsP7gybXytaFUFA7Yj42bC2O+uh1Ok9vWcctFh3+R+N2uc0t7i/iL8sfjaRdkPVBc2 z4ZPFGIU9cNCg== Subject: Re: [f2fs-dev] [PATCH v4] f2fs: introduce fragment allocation mode mount option To: Daeho Jeong Cc: linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, kernel-team@android.com, Daeho Jeong References: <20210902172404.3517626-1-daeho43@gmail.com> <9ab17089-accc-c3a3-a5dc-007fc4eeaa20@kernel.org> From: Chao Yu Message-ID: <8f8e4695-4062-60c4-0f91-2a1f6a5b0a11@kernel.org> Date: Sat, 4 Sep 2021 11:33:20 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021/9/4 4:33, Daeho Jeong wrote: >> if (f2fs_need_seq_seg(sbi)) >> return 0; >> >> static inline bool f2fs_need_seq_seg(struct f2fs_sb_info *sbi) >> { >> return F2FS_OPTION(sbi).fs_mode == FS_MODE_FRAGMENT_FIXED_BLK; >> } >> > > Do you need this in select_policy(), either? IMO, for this mode, I prefer to disable background GC and just use newly written userdata to fragment image, so I think it's fine to keep it as it is here. > Like, > if (f2fs_need_rand_seg(sbi)) > p->offset = prandom_u32() % (MAIN_SECS(sbi) * > sbi->segs_per_sec); > else if (f2fs_need_seq_seg(sbi)) > p->offset = 0; > >> One more concern... we'd better to save fragment_remained_hole as well >> as fragment_remained_chunk, otherwise, if fragment_chunk_size + >> fragment_hole_size > 512, fragment hole will be truncated to 512 - >> fragment_chunk_size due to we won't create hole with enough size as >> seg->next_blkoff has crossed end of current segment. >> > > Sorry, I don't get it. You mean making fragment_remained_hole as a > global variable? As a per curseg field. > Maybe, we run into the same race condition issue you told before for > fragment_remained_chunk. > Could you clarify this more? e.g. F2FS_OPTION(sbi).fs_mode = FS_MODE_FRAGMENT_FIXED_BLK fragment_chunk_size = 384 fragment_hole_size = 384 When creating hole: - f2fs_allocate_data_block - __refresh_next_blkoff chunk locates in [0, 383] of current segment seg->next_blkoff = 384 sbi->fragment_remained_chunk = 0 then we will reset sbi->fragment_remained_chunk to 384 and move seg->next_blkoff forward to 768 (384 + 384) - __has_curseg_space() returns false - allocate_segment() allocates new current segment So, for such case that hole may cross two segments, hole size may be truncated to left size of previous segment. Thanks, > > Thanks, >