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

From: Daniel McNeil
Date: Fri Apr 01 2005 - 20:46:12 EST


On Fri, 2005-04-01 at 17:20, Andrew Morton wrote:
> Daniel McNeil <daniel@xxxxxxxx> 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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