Re: error handling in sysfs, fill_read_buffer()

From: Oliver Neukum
Date: Tue Jan 02 2007 - 10:39:07 EST


Am Dienstag, 2. Januar 2007 16:26 schrieb Alan Stern:
> On Tue, 2 Jan 2007, Oliver Neukum wrote:
>
> > Hi,
> >
> > if a driver returns an error in fill_read_buffer(), the buffer will be
> > marked as filled. Subsequent reads will return eof. But there is
> > no data because of an error, not because it has been read.
> > Not marking the buffer filled is the obvious fix.
> >
> > Regards
> > Oliver
> >
> > Signed-off-by: Oliver Neukum <oliver@xxxxxxxxxxx>
> > --
> >
> > --- a/fs/sysfs/file.c 2006-12-24 05:00:32.000000000 +0100
> > +++ b/fs/sysfs/file.c 2007-01-01 15:03:14.000000000 +0100
> > @@ -70,7 +70,8 @@
> > * Allocate @buffer->page, if it hasn't been already, then call the
> > * kobject's show() method to fill the buffer with this attribute's
> > * data.
> > - * This is called only once, on the file's first read.
> > + * This is called only once, on the file's first read unless an error
> > + * is returned.
> > */
>
> I don't think this matches what people expect of sysfs. If a show method
> fails then the assumption is that the file cannot be read at all, so
> there's no point in trying to call the method again.

This would make handling ENOMEM very hard.

Regards
Oliver
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