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From: Tejun Heo <tj@kernel.org>
To: Milan Broz <mbroz@redhat.com>
Cc: Alasdair G Kergon <agk@redhat.com>,
	device-mapper development <dm-devel@redhat.com>,
	Jens Axboe <axboe@kernel.dk>, Tao Ma <tm@tao.ma>,
	linux-kernel@vger.kernel.org
Subject: Re: [dm-devel] [PATCH][RFC] dm: Do not open log and cow device read-write for read-only mappings
Date: Tue, 15 Feb 2011 17:41:28 +0100	[thread overview]
Message-ID: <20110215164128.GQ3160@htj.dyndns.org> (raw)
In-Reply-To: <4D5AAB8F.50901@redhat.com>

Hello,

On Tue, Feb 15, 2011 at 05:36:31PM +0100, Milan Broz wrote:
> Well, I am also not sure about that.
> 
> But the problem is that read-write open fails now while it worked before.
> (TBH I have no idea when that EROFS fallback worked - because the code
> opened device RW, issued EROGET ioctl and set read-only... for years.)
> 
> Anyway I think EROFS is used on block devices, just grep kernel source.

Ah, okay, so the fallback was there just in case.  It didn't really
trigger and right it wouldn't have triggered until now, so your
assertion about how many programs would break is kinda bogus.  You
just have single isolated case which hasn't been excercised till now.
There may as well be code pieces which check against EACCES or what
not.

That said, maybe -EROFS is the better fit.  I really have no idea.
Maybe we should just revert and leave rw accesses to ro block devices
alone.  Jens, what do you think?

Thanks.

-- 
tejun

  reply	other threads:[~2011-02-15 16:41 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
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 [this message]
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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