linux-kernel - Re: [PATCH] ufs: Check if page has buffers before calling page

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Date:	Wed, 2 Feb 2011 07:23:47 +0300
From:	Evgeniy Dushistov <dushistov@...l.ru>
To:	Alessio Igor Bogani <abogani@...nel.org>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	Tim Bird <tim.bird@...sony.com>
Subject: Re: [PATCH] ufs: Check if page has buffers before calling
 page_buffers()

On Tue, Feb 01, 2011 at 10:23:38PM +0100, Alessio Igor Bogani wrote:
> In ufs_change_blocknr() we have called page_buffers() without checking if the
> page actually had pages attached to it and this could cause a BUG oops.
> 

This looks wrong for me. May be I missed something?
Put little more context here.
In ufs the tail of small files consists of fragments (usually 2K),
the rest of file consists of blocks (usually 16K=8 fragments).
When file is growing, and tail become too big (8 fragments)
we allocate one block and move content of 8 fragments to it.

So in our case we reach (during realocation) point when
!page_has_buffers(page) (how?) and in your patch you suggest
just ignore such buffer (in terms of ufs - fragments),
in other words silently corrupt user data.
May be there is better variant?

-- 
/Evgeniy

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