linux-kernel - Re: Crash when IO is being submitted and block size is changed

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Date:	Thu, 28 Jun 2012 11:44:03 -0400 (EDT)
From:	Mikulas Patocka <mpatocka@...hat.com>
To:	Jan Kara <jack@...e.cz>
cc:	Alexander Viro <viro@...iv.linux.org.uk>,
	Jens Axboe <axboe@...nel.dk>,
	"Alasdair G. Kergon" <agk@...hat.com>,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	dm-devel@...hat.com
Subject: Re: Crash when IO is being submitted and block size is changed



On Thu, 28 Jun 2012, Jan Kara wrote:

> > Do you have any other ideas what to do with it?
>   Yeah, it's nasty and neither solution looks particularly appealing. One
> idea that came to my mind is: I'm trying to solve some races between direct
> IO, buffered IO, hole punching etc. by a new mapping interval lock. I'm not
> sure if it will go anywhere yet but if it does, we can fix the above race
> by taking the mapping lock for the whole block device around setting block
> size thus effectivelly disallowing any IO to it.
> 
> 								Honza
> -- 
> Jan Kara <jack@...e.cz>
> SUSE Labs, CR

What races are you trying to solve? There used to be i_alloc_mem that 
prevented direct i/o while the file is being truncated, but it disappeared 
in recent kernels...

Mikulas
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