Re: error handling in sysfs, fill_read_buffer()

[Alan Stern <stern@rowland.harvard.edu>]

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@neukum.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.

Alan Stern

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