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=-1.0 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS 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 6D9A7C4360F for ; Mon, 11 Mar 2019 05:19:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 330C3206DF for ; Mon, 11 Mar 2019 05:19:35 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=colorremedies-com.20150623.gappssmtp.com header.i=@colorremedies-com.20150623.gappssmtp.com header.b="xDzYX1OP" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725891AbfCKFTd (ORCPT ); Mon, 11 Mar 2019 01:19:33 -0400 Received: from mail-lj1-f177.google.com ([209.85.208.177]:39022 "EHLO mail-lj1-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725850AbfCKFTd (ORCPT ); Mon, 11 Mar 2019 01:19:33 -0400 Received: by mail-lj1-f177.google.com with SMTP id g80so2836968ljg.6 for ; Sun, 10 Mar 2019 22:19:31 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=colorremedies-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=d6r7v+rdVa9HC+A+Zd/v/QQ/GJ/P/innmsfdz83fGjQ=; b=xDzYX1OPdgT1lcEyQaG/U/na7v8Jt5d/4GIUla03Shsn7ZY+yRijp6YfWGdkLxhzm5 vdNt0CT/HWjBIJbfzsVMXsIexYtlUHO8zAWod03DAKvcZ0AzVfSTaOXY7MICAPRM5EmA RSKXGgCJ+0HyGwwsW4QWM9hWvbvT41fQrwhwJM2gLFau3ayjmTE3PWQhYmsUB5czguMk pKV3dfKPAxSo/F70Z7Dy61Qmvl24n9kEyrjerOqOP1xl6X+M0aJReX+JbPfkVwxamMay o8mVZsKKznoQvsUseeZy14AuIjdnDvQQGh2HtG/gN996g+z1xept2MIlbgY41w8x9kNI hEhw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=d6r7v+rdVa9HC+A+Zd/v/QQ/GJ/P/innmsfdz83fGjQ=; b=b0YW31GL0sSNCq7cLm/4ai1PXJjIVfN80Y2ajinlMmnHbK2oQApvZvXsttqAndfSzv IFk4R6pKWPg6MtXuArcgBOEswNcGlbvCen1/tT8hslUBBydCyxK9O0H2XrAxoBBF+p14 EiEwQPuVRHwbqj/ZhXDBE+55rmzu2XlSYZtT+jphZCge2JDryEsiic/00rhrtqpg1TO6 IISjIvWz5zf7FMjvj1NK4Id2U8hxjk6Rdnq1ghLMUMvpfA1s49u2WnfBU9aRe/7yIuwE bHunBCHzcCQElSZvJ8Vmat4ZvDhSSd3hlVlMbGBiJo8MHy+0tp3duLqDC5ZzQYf1BYq8 k3Tg== X-Gm-Message-State: APjAAAUa7pkVzGOAmLQV4AAJQ0yhwEvmmjq0U7URFpahXbxJ3z54Q09J yMlrXrWYc6EbHB1SgYP7m5DwkEnGZ8zQ0S32dDWw2JGiL+o= X-Google-Smtp-Source: APXvYqxQ5Y7fN4fHm36n+mOEaKs/VLaRhlHYGnQvv/rKrznehctsl5uxXwTxHiavnoJHyfCqBEKQaGXB9jJ85a00qt8= X-Received: by 2002:a2e:8701:: with SMTP id m1mr15263664lji.132.1552281570829; Sun, 10 Mar 2019 22:19:30 -0700 (PDT) MIME-Version: 1.0 References: <2621cc31-0d74-f514-fae4-fea35e34fae3@gmx.com> In-Reply-To: <2621cc31-0d74-f514-fae4-fea35e34fae3@gmx.com> From: Chris Murphy Date: Sun, 10 Mar 2019 23:19:19 -0600 Message-ID: Subject: Re: confusing behavior when supers mismatch To: Qu Wenruo Cc: Btrfs BTRFS Content-Type: text/plain; charset="UTF-8" Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Sun, Mar 10, 2019 at 10:58 PM Qu Wenruo wrote: > > Normally 'btrfs rescue super' should be enough for accidentally wiped btrfs. > > If not, then we should fix it of course. Looks like a bug then. $ sudo mkfs.btrfs /dev/mapper/vg-f30test btrfs-progs v4.20.2 See http://btrfs.wiki.kernel.org for more information. Label: (null) UUID: e819e675-a697-45f8-8351-d109d5b95514 Node size: 16384 Sector size: 4096 Filesystem size: 100.00GiB Block group profiles: Data: single 8.00MiB Metadata: DUP 1.00GiB System: DUP 8.00MiB SSD detected: no Incompat features: extref, skinny-metadata Number of devices: 1 Devices: ID SIZE PATH 1 100.00GiB /dev/mapper/vg-f30test $ sudo mount /dev/mapper/vg-f30test /mnt/test $ sudo umount /mnt/test $ sudo wipefs -a /dev/mapper/vg-f30test /dev/mapper/vg-f30test: 8 bytes were erased at offset 0x00010040 (btrfs): 5f 42 48 52 66 53 5f 4d $ sudo btrfs rescue super -v /dev/mapper/vg-f30test No valid Btrfs found on /dev/mapper/vg-f30test Usage or syntax errors $ echo "_BHRfS_M" | sudo dd bs=1 count=8 of=/dev/mapper/vg-f30test seek=$((64*1024+64)) 8+0 records in 8+0 records out 8 bytes copied, 0.00523996 s, 1.5 kB/s $ sudo btrfs rescue super -v /dev/mapper/vg-f30test All Devices: Device: id = 1, name = /dev/mapper/vg-f30test Before Recovering: [All good supers]: device name = /dev/mapper/vg-f30test superblock bytenr = 65536 device name = /dev/mapper/vg-f30test superblock bytenr = 67108864 [All bad supers]: All supers are valid, no need to recover $ -- Chris Murphy