From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from aserp1040.oracle.com ([141.146.126.69]:21001 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752583AbbITFiH (ORCPT ); Sun, 20 Sep 2015 01:38:07 -0400 Message-ID: <55FE462D.2010503@oracle.com> Date: Sun, 20 Sep 2015 13:37:49 +0800 From: Anand Jain MIME-Version: 1.0 To: Qu Wenruo , Qu Wenruo , linux-btrfs@vger.kernel.org Subject: Re: [PATCH 2/2] btrfs: Remove unneeded missing device number check References: <1442375031-18212-1-git-send-email-quwenruo@cn.fujitsu.com> <1442375031-18212-2-git-send-email-quwenruo@cn.fujitsu.com> <55FA8B31.9080604@oracle.com> <55FA8F8B.6060903@gmx.com> <55FB6D31.9030504@oracle.com> <55FB71A8.3000004@cn.fujitsu.com> <55FBB2F7.4040402@oracle.com> <55FDFE46.40600@gmx.com> In-Reply-To: <55FDFE46.40600@gmx.com> Content-Type: text/plain; charset=utf-8; format=flowed Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 09/20/2015 08:31 AM, Qu Wenruo wrote: > > > 在 2015年09月18日 14:45, Anand Jain 写道: >> >> Hi Qu, >> >> Thanks for the comments on patch [1]. >> >>> For example, if one use single metadata for 2 disks, >> > and each disk has one metadata chunk on it. >> >> how that can be achieved ? > By this, I mean, the metadata profile is SINGLE, > and there is 2 metadata chunks. > > One on disk1 and one on disk2. > > As btrfs chunk allocate will always use device by avaiable space order, > it should be quite easy to archieve that situation. > > In that case, any missing device will be a disaster, in this case the read chunk would anyway fail, right ? and that will lead to mount fail. Thanks, Anand > and it's better not > to allow RW mount. > > Thanks, > Qu >> >>> One device got missing later. >> >> it would surely depend on which one of the device ? (initial only >> devid 1 mountable, with other missing) >> >> >> Thanks, Anand >> >>> Then your patch will allow the fs to be mounted as rw, even some tree >>> block can be in the missing device. >>> For RO case, it won't be too dangerous, but if we mounted it as RW, who >>> knows what will happen. >>> (Normal tree COW thing should fail before real write, but I'm not sure >>> about other RW operation like scrub/replace/balance and others) >>> >>> And I think that's the original design concept behind the old missing >>> device number check, and it's not a bad idea to follow it anyway. >>> >>> For the patch size, I find a good idea to handle it, and should make the >>> patch(set) size below 200 lines. >>> >>> Further more, it's even possible to make btrfs change mount option to >>> degraded for runtime device missing. >>> >>> Thanks, >>> Qu >>>> >>>> I tried to break both the approaches (this patch set and [1]) but I >>>> wasn't successful. sorry if I am missing something. >>>> >>>> Thanks, Anand >>>> >>>> [1] [PATCH 23/23] Btrfs: allow -o rw,degraded for single group profile >> >> >> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html