From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from aserp1040.oracle.com ([141.146.126.69]:44341 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1031731Ab3HJCE7 (ORCPT ); Fri, 9 Aug 2013 22:04:59 -0400 Message-ID: <52059FC2.3080203@oracle.com> Date: Sat, 10 Aug 2013 10:04:50 +0800 From: anand jain MIME-Version: 1.0 To: Eric Sandeen CC: linux-btrfs@vger.kernel.org Subject: Re: [PATCH 2/2] btrfs: btrfs_rm_device() should zero mirror SB as well References: <1374773376-29853-1-git-send-email-anand.jain@oracle.com> <1374773376-29853-2-git-send-email-anand.jain@oracle.com> <5205556E.8030902@redhat.com> In-Reply-To: <5205556E.8030902@redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Sender: linux-btrfs-owner@vger.kernel.org List-ID: >> btrfs fi show >> Label: none uuid: e7aae9f0-1aa8-41f5-8fb6-d4d8f80cdb2c >> Total devices 1 FS bytes used 28.00KiB >> devid 2 size 2.00GiB used 0.00 path /dev/sdc <-- WRONG >> devid 1 size 2.00GiB used 20.00MiB path /dev/sdb > > Ok, now it's findable. Isn't that exactly how this should behave? > What is wrong about this? Total devices is still 1. >> mount /dev/sdc /btrfs >> btrfs fi show --kernel >> Label: none uuid: e7aae9f0-1aa8-41f5-8fb6-d4d8f80cdb2c mounted: /btrfs >> Group profile: metadata: single data: single >> Total devices 1 FS bytes used 28.00KiB >> devid 1 size 2.00GiB used 20.00MiB path /dev/sdb > > Oh good, you could bring it back after a potential administrative error, > using a recovery tool (btrfs-select-super)! Isn't that a good thing? Note, here btrfs fi show used the new option --kernel this does not show /dev/sdc though you use it mount. Its all messed up. If user wants to bring back the intentionally deleted disk, then they should rather call btrfs dev add, so that it will take care of integrating the disk back to the FS. recovery tools are for possible recovery from the corruption, delete is not a corruption. Thats an intentional step that user decided to take and the undo for it is 'dev add'. > IOWS: what does this change actually fix? Writes zeros to all copies of SB when disk is deleted (before we used to just zero only the first copy). In that way corruption is distinguished from the deleted disk in a fair calculations. Otherwise allowing these things would cost us in terms of support for the administrative error. Which we don't have to encourage. Thanks, Anand