Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   Naohiro Aota <Naohiro.Aota@wdc.com>
To:     Josef Bacik <josef@toxicpanda.com>
CC:     "linux-btrfs@vger.kernel.org" <linux-btrfs@vger.kernel.org>,
        David Sterba <dsterba@suse.com>, Chris Mason <clm@fb.com>,
        Qu Wenruo <wqu@suse.com>, Nikolay Borisov <nborisov@suse.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Hannes Reinecke <hare@suse.com>,
        "linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
        Damien Le Moal <Damien.LeMoal@wdc.com>,
        =?iso-8859-1?Q?Matias_Bj=F8rling?= <mb@lightnvm.io>,
        Johannes Thumshirn <jthumshirn@suse.de>,
        Bart Van Assche <bvanassche@acm.org>
Subject: Re: [PATCH 08/19] btrfs: make unmirroed BGs readonly only if we have
 at least one writable BG
Thread-Topic: [PATCH 08/19] btrfs: make unmirroed BGs readonly only if we have
 at least one writable BG
Thread-Index: AQHVHTKH8wZ92WupxkqjiXGkYBnq9g==
Date:   Tue, 18 Jun 2019 07:42:46 +0000
Message-ID: <SN6PR04MB5231CACF687ED7001C73111A8CEA0@SN6PR04MB5231.namprd04.prod.outlook.com>
References: <20190607131025.31996-1-naohiro.aota@wdc.com>
 <20190607131025.31996-9-naohiro.aota@wdc.com>
 <20190613140921.a2kmty5p6lzqztej@MacBook-Pro-91.local>
Accept-Language: en-US
Content-Language: en-US
wdcipoutbound: EOP-TRUE
Content-Type: text/plain; charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
X-MS-Exchange-CrossTenant-Network-Message-Id: 69bd77c0-1694-4496-90b3-08d6f3c08e59
X-MS-Exchange-CrossTenant-originalarrivaltime: 18 Jun 2019 07:42:46.6129
 (UTC)
X-MS-Exchange-CrossTenant-fromentityheader: Hosted
X-MS-Exchange-CrossTenant-id: b61c8803-16f3-4c35-9b17-6f65f441df86
X-MS-Exchange-CrossTenant-mailboxtype: HOSTED
X-MS-Exchange-CrossTenant-userprincipalname: Naohiro.Aota1@wdc.com
X-MS-Exchange-Transport-CrossTenantHeadersStamped: SN6PR04MB5184
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On 2019/06/13 23:09, Josef Bacik wrote:=0A=
> On Fri, Jun 07, 2019 at 10:10:14PM +0900, Naohiro Aota wrote:=0A=
>> If the btrfs volume has mirrored block groups, it unconditionally makes=
=0A=
>> un-mirrored block groups read only. When we have mirrored block groups, =
but=0A=
>> don't have writable block groups, this will drop all writable block grou=
ps.=0A=
>> So, check if we have at least one writable mirrored block group before=
=0A=
>> setting un-mirrored block groups read only.=0A=
>>=0A=
> =0A=
> I don't understand why you want this.  Thanks,=0A=
> =0A=
> Josef=0A=
> =0A=
=0A=
This is necessary to handle e.g. btrfs/124 case.=0A=
=0A=
When we mount degraded RAID1 FS and write to it, and then=0A=
re-mount with full device, the write pointers of corresponding=0A=
zones of written BG differ.  The patch 07 mark such block group=0A=
as "wp_broken" and make it read only.  In this situation, we only=0A=
have read only RAID1 BGs because of "wp_broken" and un-mirrored BGs=0A=
are also marked read only, because we have RAID1 BGs.=0A=
As a result, all the BGs are now read only, so that we=0A=
cannot even start the rebalance to fix the situation.=0A=