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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


  reply	other threads:[~2011-02-14 14:23 UTC|newest]

Thread overview: 29+ 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
2011-02-15 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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