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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, 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 BF429C433DF for ; Mon, 1 Jun 2020 20:35:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9EA07206E2 for ; Mon, 1 Jun 2020 20:35:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728182AbgFAUft (ORCPT ); Mon, 1 Jun 2020 16:35:49 -0400 Received: from syrinx.knorrie.org ([82.94.188.77]:47152 "EHLO syrinx.knorrie.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727875AbgFAUfr (ORCPT ); Mon, 1 Jun 2020 16:35:47 -0400 Received: from [IPv6:2a02:a213:2b80:f000::12] (unknown [IPv6:2a02:a213:2b80:f000::12]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by syrinx.knorrie.org (Postfix) with ESMTPSA id E18F46092DF71; Mon, 1 Jun 2020 22:35:44 +0200 (CEST) Subject: Re: space_cache=v1 and v2 at the time time? To: dsterba@suse.cz, Chris Murphy , Btrfs BTRFS References: <20200601175252.GC18421@twin.jikos.cz> From: Hans van Kranenburg Autocrypt: addr=hans@knorrie.org; keydata= mQINBFo2pooBEADwTBe/lrCa78zuhVkmpvuN+pXPWHkYs0LuAgJrOsOKhxLkYXn6Pn7e3xm+ ySfxwtFmqLUMPWujQYF0r5C6DteypL7XvkPP+FPVlQnDIifyEoKq8JZRPsAFt1S87QThYPC3 mjfluLUKVBP21H3ZFUGjcf+hnJSN9d9MuSQmAvtJiLbRTo5DTZZvO/SuQlmafaEQteaOswme DKRcIYj7+FokaW9n90P8agvPZJn50MCKy1D2QZwvw0g2ZMR8yUdtsX6fHTe7Ym+tHIYM3Tsg 2KKgt17NTxIqyttcAIaVRs4+dnQ23J98iFmVHyT+X2Jou+KpHuULES8562QltmkchA7YxZpT mLMZ6TPit+sIocvxFE5dGiT1FMpjM5mOVCNOP+KOup/N7jobCG15haKWtu9k0kPz+trT3NOn gZXecYzBmasSJro60O4bwBayG9ILHNn+v/ZLg/jv33X2MV7oYXf+ustwjXnYUqVmjZkdI/pt 30lcNUxCANvTF861OgvZUR4WoMNK4krXtodBoEImjmT385LATGFt9HnXd1rQ4QzqyMPBk84j roX5NpOzNZrNJiUxj+aUQZcINtbpmvskGpJX0RsfhOh2fxfQ39ZP/0a2C59gBQuVCH6C5qsY rc1qTIpGdPYT+J1S2rY88AvPpr2JHZbiVqeB3jIlwVSmkYeB/QARAQABtCZIYW5zIHZhbiBL cmFuZW5idXJnIDxoYW5zQGtub3JyaWUub3JnPokCTgQTAQoAOBYhBOJv1o/B6NS2GUVGTueB 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Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org Hi, On 6/1/20 7:52 PM, David Sterba wrote: > On Thu, May 28, 2020 at 11:04:07PM +0200, Hans van Kranenburg wrote: >> Hi, >> >> On 5/27/20 4:12 AM, Chris Murphy wrote: >>> What are the implications of not clearing v1 before enabling v2? >>> >>> From btrfs insp dump-t, I still see the v1 bitmaps present: >>> >>> root tree >>> leaf 6468501504 items 42 free space 9246 generation 22 owner ROOT_TREE >>> leaf 6468501504 flags 0x1(WRITTEN) backref revision 1 >>> ... >>> item 30 key (FREE_SPACE UNTYPED 22020096) itemoff 11145 itemsize 41 >>> location key (256 INODE_ITEM 0) >>> cache generation 17 entries 0 bitmaps 0 >>> item 31 key (FREE_SPACE UNTYPED 1095761920) itemoff 11104 itemsize 41 >>> location key (257 INODE_ITEM 0) >>> cache generation 17 entries 0 bitmaps 0 >>> ... >>> >>> >>> And later the free space tree: >>> >>> free space tree key (FREE_SPACE_TREE ROOT_ITEM 0) >>> leaf 6471073792 items 39 free space 15196 generation 22 owner FREE_SPACE_TREE >>> leaf 6471073792 flags 0x1(WRITTEN) backref revision 1 >>> fs uuid 3c464210-08c7-4cf0-b175-e4b781ebea19 >>> chunk uuid f1d18732-7c3d-401c-8637-e7d4d9c7a0b8 >>> item 0 key (1048576 FREE_SPACE_INFO 4194304) itemoff 16275 itemsize 8 >>> free space info extent count 2 flags 0 >>> item 1 key (1048576 FREE_SPACE_EXTENT 16384) itemoff 16275 itemsize 0 >>> free space extent >>> item 2 key (1081344 FREE_SPACE_EXTENT 4161536) itemoff 16275 itemsize 0 >>> free space extent >>> ... >>> >>> I was surprised there's no warning when I use space_cache=v2 without >>> first clearing v1. >> >> It's just sitting there, occupying some space, doing nothing. > > Hm that's not ideal, right? There's support in btrfs check, > "btrfs check --clear-space-cache v1", but it needs unmounted filesystem. > I don't remember if that was discussed when v2 was introduced, but it > seems strange. As we want to make v2 default soon, the conversion should > work without such surprises. I guess the most straightforward thing to do would be to execute a copy of this remove space cache v1 code before creating the v2 tree when mounting first time with v2 enabled. K