linux-kernel - Re: [RFC] Reverting "bd_mount_mutex" to "bd_mount

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Message-ID: <20060927135705.GA30311@elte.hu>
Date:	Wed, 27 Sep 2006 15:57:05 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Srinivasa Ds <srinivasa@...ibm.com>
Cc:	dm-devel@...hat.com, linux-lvm@...hat.com,
	linux-kernel@...r.kernel.org, agk@...hat.com
Subject: Re: [RFC] Reverting "bd_mount_mutex" to "bd_mount_sem"


* Srinivasa Ds <srinivasa@...ibm.com> wrote:

>   On debugging I found out that,"dmsetup suspend <device name>" calls 
> "freeze_bdev()",which locks "bd_mount_mutex" to make sure that no new 
> mounts happen on bdev until thaw_bdev() is called.
>   This "thaw_bdev()" is getting called when we resume the device 
> through "dmsetup resume <device-name>".
>   Hence we have 2 processes,one of which locks 
> "bd_mount_mutex"(dmsetup suspend) and Another(dmsetup resume) unlocks 
> it.

hm, to me this seems quite a fragile construct - even if the 
mutex-debugging warning is worked around by reverting to a semaphore.

	Ingo
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