Re: [PATCH] Direct IO async short read bug followup

[Daniel McNeil <daniel@osdl.org>]

On Fri, 2005-04-01 at 17:20, Andrew Morton wrote:
> Daniel McNeil <daniel@osdl.org> wrote:
> >
> > I updated the patch to add an i_size element to the dio structure and
> >  sample i_size during i/o submission.  When i/o completes the result can
> >  be truncated to match the file size without using i_size_read(), thus
> >  the aio result now matches the number of bytes read to the end of file.
> > 
> 
> Can you provide the analysis of the bug, please?

The direct i/o code is mapping the read request to the file system
block.  If the file size was not on a block boundary, the result
would show the the read reading past EOF.  This was only happening
for the AIO case.  The non-AIO case truncates the result to match
file size (in direct_io_worker).  This patch does the same thing
for the AIO case, it truncates the result to match the file size
if the read reads past EOF.
> 
> > 
> >  Daniel
> > 
> >  --- linux-2.6.11.orig/fs/direct-io.c	2005-04-01 15:33:11.000000000 -0800
> >  +++ linux-2.6.11/fs/direct-io.c	2005-03-31 16:59:15.000000000 -0800
> >  @@ -66,6 +66,7 @@ struct dio {
> >   	struct bio *bio;		/* bio under assembly */
> >   	struct inode *inode;
> >   	int rw;
> >  +	ssize_t i_size;			/* i_size when submitted */
> 
> I'll change this to loff_t, OK?
> -

Yes.

Daniel

-
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