From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoph Hellwig <hch@infradead.org>
Subject: Re: [PATCH] procfs: stop using vmtruncate
Date: Tue, 21 Jun 2011 03:43:38 -0400
Message-ID: <20110621074338.GA26156@infradead.org>
References: <20110620224727.GA22187@infradead.org>
 <20110621020526.GY11521@ZenIV.linux.org.uk>
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Cc: linux-fsdevel@vger.kernel.org
To: Al Viro <viro@ZenIV.linux.org.uk>
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On Tue, Jun 21, 2011 at 03:05:26AM +0100, Al Viro wrote:
> On Mon, Jun 20, 2011 at 06:47:27PM -0400, Christoph Hellwig wrote:
> > Procfs doens't have any ->truncate instances, so all vmtruncate calls can
> > be replaced with truncate_setsize, given that we've just done the
> > inode_newsize_ok check as part of inode_change_ok just before.
> 
> What files on procfs allow meaningful truncate anyway?  I agree that
> vmtruncate() there is bogus, but AFAICT we have the following picture:
> 	* there are files with non-zero i_size (/proc/kcore and
> /proc/bus/pci/*/*); for any of those ATTR_SIZE should fail and I don't
> think it should fail silently.
> 	* the rest has size 0 and for those ATTR_SIZE to non-0 length
> should definitely fail with an error.

True.  We probably should simply refuse any ATTR_SIZE calls.