From: Milan Broz <mbroz@redhat.com>
To: Tejun Heo <tj@kernel.org>
Cc: Tao Ma <tm@tao.ma>,
linux-kernel@vger.kernel.org, Jens Axboe <axboe@kernel.dk>,
device-mapper development <dm-devel@redhat.com>
Subject: Re: [PATCH][RFC] dm: Do not open log and cow device read-write for read-only mappings
Date: Mon, 14 Feb 2011 15:23:20 +0100 [thread overview]
Message-ID: <4D593AD8.7070901@redhat.com> (raw)
In-Reply-To: <20110214140940.GM18742@htj.dyndns.org>
On 02/14/2011 03:09 PM, Tejun Heo wrote:
> On Mon, Feb 14, 2011 at 02:14:57PM +0100, Milan Broz wrote:
>>> But it doesn't fix the read-only snapshot issue and I guess there will be
>>> the same problem with read-only MD code too.
>>> (so the 2) issue here https://lkml.org/lkml/2011/2/12/209).
>
> So, the problem is caused by dm opening members rw even for ro
> devices, right?
The patch uncover these shortcomings in code.
(Unfortunately quite late in RC...)
>> I am not sure if this is complete fix... note that:
>> - what happens during mirror resync and read-only log?
>> - for COW, it there situation we need to update header in read-oly mode? (invalidated snap?)
>
> But if the underlying device is marked ro, dm shouldn't update it at
> all. The device should be opened ro and ro policy should be enforced.
Sure. So we need to check these situations I described.
Btw the same pattern is in MD code in lock_rdev() ...
Milan
next prev parent reply other threads:[~2011-02-14 14:23 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-02-13 2:02 block device read-only handling regression in 2.6.38-rc4 (bisected) Milan Broz
2011-02-13 10:58 ` [PATCH] loop: clear read-only flag in loop_clr_fd Tao Ma
2011-02-13 14:11 ` Milan Broz
2011-02-13 15:05 ` Tao Ma
2011-02-13 16:44 ` Milan Broz
2011-02-14 10:30 ` Tejun Heo
2011-02-14 11:47 ` Milan Broz
2011-02-14 13:14 ` [PATCH][RFC] dm: Do not open log and cow device read-write for read-only mappings Milan Broz
2011-02-14 14:09 ` Tejun Heo
2011-02-14 14:23 ` Milan Broz [this message]
2011-02-14 15:44 ` Tejun Heo
2011-02-14 23:15 ` NeilBrown
2011-02-15 2:03 ` [dm-devel] " Alasdair G Kergon
2011-02-15 12:17 ` Milan Broz
2011-02-15 12:46 ` Alasdair G Kergon
2011-02-15 15:20 ` Tejun Heo
2011-02-15 15:46 ` Alasdair G Kergon
2011-02-15 15:50 ` Tejun Heo
2011-02-15 16:05 ` Milan Broz
2011-02-15 16:12 ` Tejun Heo
2011-02-15 16:36 ` Milan Broz
2011-02-15 16:41 ` Tejun Heo
2011-02-15 16:56 ` Alasdair G Kergon
2011-02-16 8:46 ` Tejun Heo
2011-02-16 8:46 ` Tejun Heo
2011-02-15 16:58 ` Milan Broz
2011-02-16 8:39 ` Tejun Heo
2011-02-15 15:16 ` [PATCH] Return EROFS if read-only detected on block device Milan Broz
2011-02-14 14:39 ` [dm-devel] [PATCH][RFC] dm: Do not open log and cow device read-write for read-only mappings Alasdair G Kergon
2011-02-14 14:07 ` [PATCH] loop: clear read-only flag in loop_clr_fd Tejun Heo
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