linux-kernel - Re: error handling in sysfs, fill_read

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Date:	Tue, 2 Jan 2007 16:38:49 +0100
From:	Oliver Neukum <oliver@...kum.org>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	Oliver Neukum <oliver@...kum.name>, gregkh@...e.de,
	maneesh@...ibm.com, linux-kernel@...r.kernel.org
Subject: Re: error handling in sysfs, fill_read_buffer()

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@...kum.name>
> > --
> > 
> > --- 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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