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=-7.9 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=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 BC517C433EF for ; Sat, 11 Sep 2021 10:42:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 90E1E611F2 for ; Sat, 11 Sep 2021 10:42:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235627AbhIKKnS (ORCPT ); Sat, 11 Sep 2021 06:43:18 -0400 Received: from mail.kernel.org ([198.145.29.99]:52658 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235443AbhIKKnR (ORCPT ); Sat, 11 Sep 2021 06:43:17 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 0A40360FDC; Sat, 11 Sep 2021 10:42:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1631356925; bh=N0wtIK96dx3XM0eOaHSs5E3Sn4Ns8OuBLM3E1H39muY=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=onyAAi7dUBGSiTnnPh8mufeQY8AAEFVpCA0jOYCXoMm7kumxMcywMfH7IaFy7q2UJ qPEI2Op+nqQ4/GG2zzIrR53BSu+hr8hem37s1baTQZpD/0OE7NHlt6/m2gUaAq00Cp oH9nRVaGC547VNNR93Ww1zWREdNsj7BCWyZMtS4AVAKTOADUHZxg1XRB2R0U1LRhcO xceqB6GzfRD5olyYpJAgj5vJR5Vkz1rULOSXrTNa7JTZvzcR+sMn2bwEEHhCTslFqu D00fslv/1muHou+eA/OGGS9m5sYcinfFSABIFTU0zuLhpf1Nk6HUk461rQdA2WVAdl Z73E+63cowxTQ== 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> <8f8e4695-4062-60c4-0f91-2a1f6a5b0a11@kernel.org> From: Chao Yu Message-ID: <3108fdfa-34c4-7e57-1674-c71ab08b4a1e@kernel.org> Date: Sat, 11 Sep 2021 18:42:01 +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 2021/9/10 23:24, Daeho Jeong wrote: > On Fri, Sep 10, 2021 at 7:34 AM Daeho Jeong wrote: >> >> On Thu, Sep 9, 2021 at 4:50 PM Chao Yu wrote: >>> >>> On 2021/9/8 2:12, Daeho Jeong wrote: >>>> On Fri, Sep 3, 2021 at 11:45 PM Chao Yu wrote: >>>>> >>>>> On 2021/9/4 12:40, Daeho Jeong wrote: >>>>>>> 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. >>>>>> >>>>>> First, sbi->fragment_remained_chunk should be seg->fragment_remained_chunk. >>>>> >>>>> Oh, correct. >>>>> >>>>>> I understand what you mean, so you mean we need to take the leftover >>>>>> "hole" size over to the next segment? >>>>>> In the example, the leftover hole size will be (384 - (512-384)). Do >>>>>> you want to take this over to the next segment? >>>>> >>>>> Yes, the left 256 block-sized hole should be created before next chunk >>>>> in next opened segment. >>>>> >>>> >>>> Chao, >>>> >>>> Do you have any decent idea to pass the left hole size to the next >>>> segment which will be allocated? >>> >>> Daeho, >>> >>> I guess we can record left hole size in seg->fragment_remained_hole. >>> >> >> I understand we need a new fragment_remained_hole variable in segment structure. >> But, I mean.. How can we pass over the left hole size from the >> previous segment to the next segment? >> > > I mean we don't know which segment will be the next segment, do we? Yeah, that's why I prefer to let __get_next_segno() return zero in fixed_block fragment mode, then log header may have chance to allocate hole in contiguous segments. Thanks, > >> Thanks, >> >>> Thanks, >>> >>>> >>>> Thanks, >>>> >>>>> Thanks, >>>>> >>>>>>