Re: [RFC PATCH 1/3] Implement generic freeze feature

From: Christoph Hellwig
Date: Mon Apr 28 2008 - 09:04:28 EST


On Mon, Apr 28, 2008 at 09:59:55PM +0900, Takashi Sato wrote:
>> I think the protection against double freezes would be better done by
>> using a trylock on bd_mount_sem.
>
> bd_mount_sem can protect against only freezes and cannot protect against
> unfreezes. If multiple unfreezes run in parallel, the multiple up() for
> bd_mount_sem might occur incorrectly.

Indeed. The bit flag would fix that because unfreeze could then check
for the bit beeing set first. So that's probably the easiest way to go.

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