Subject: Re: [PATCH] 2.6.10 -  direct-io async short read bug
From: Badari Pulavarty <pbadari@us.ibm.com>
To: Daniel McNeil <daniel@osdl.org>
Cc: Suparna Bhattacharya <suparna@in.ibm.com>, Andrew Morton <akpm@osdl.org>,
       =?ISO-8859-1?Q?S=E9bastien_Dugu=E9?= <sebastien.dugue@bull.net>,
       "linux-aio@kvack.org" <linux-aio@kvack.org>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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Date: 09 Mar 2005 07:58:51 -0800
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On Tue, 2005-03-08 at 17:44, Daniel McNeil wrote:
> On Tue, 2005-03-08 at 11:18, Badari Pulavarty wrote:
> > > Andrew, please don't apply the original patch. We shouldn't even attempt
> > > to submit IO beyond the filesize. We should truncate the IO request to
> > > filesize. I will send a patch today to fix this.
> > > 
> > 
> > Well, spoke too soon. This is an ugly corner case :( But I have
> > a ugly hack to fix it :)
> > 
> > Let me ask you a basic question: Do we support DIO reads on a file
> > which is not blocksize multiple in size ? (say 12K - 10 bytes) ?
> > 
> > What about the ones which are not 4K but 512 byte multiple ? (say 7K) ?
> > 
> > I need answer to those, to figure out how hard I should try to fix this.
> > 
> > Anyway, here is ugly version of the patch - which will limit the IO
> > size to filesize and uses lower blocksizes to read the file (since
> > the filesize is only 3K, it would go down to 512 byte blocksize).
> > 
> 
> BTW, I got a compile error because the 'iov' parameter is
> declared with 'const', so your patch is changing a read-only
> value.  :(
> 
> Daniel
> 

Told you, it was ugly and I noted in the comments too :)

BTW, I don't think that is the correct solution. I guess,
we need to do the IO beyond EOF and zero out the data.
And also, this can happen only if the EOF is in the middle
of the block - so its an issue only for the last block.

What do you think ?

Thanks,
Badari
> 

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