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From: Tejun Heo <tj@kernel.org>
To: Milan Broz <mbroz@redhat.com>
Cc: Tao Ma <tm@tao.ma>,
	linux-kernel@vger.kernel.org, Jens Axboe <axboe@kernel.dk>,
	device-mapper development <dm-devel@redhat.com>,
	Neil Brown <neilb@suse.de>
Subject: Re: [PATCH][RFC] dm: Do not open log and cow device read-write for read-only mappings
Date: Mon, 14 Feb 2011 16:44:30 +0100	[thread overview]
Message-ID: <20110214154430.GR18742@htj.dyndns.org> (raw)
In-Reply-To: <4D593AD8.7070901@redhat.com>

Hello,

On Mon, Feb 14, 2011 at 03:23:20PM +0100, Milan Broz wrote:
> >> 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.

Yeap, it seems dm folks are gonna take care of dm part.

> Btw the same pattern is in MD code in lock_rdev() ...

Indeed, cc'ing Neil.  Hi, the whole thread can be read from the
following URL.

  http://thread.gmane.org/gmane.linux.kernel/1099399/focus=1099735

blkdev_get() now rejects rw open of devices which are marked
read-only.  I think the right thing to do would be opening the member
devices ro if the array is assembled for ro access (similar to Milan's
patch for dm).  How does that sound?

Thanks.

-- 
tejun

  reply	other threads:[~2011-02-14 15:44 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
2011-02-14 15:44                   ` Tejun Heo [this message]
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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