Re: [PATCH] Separate FMODE_PREAD/FMODE_PWRITE into separate flags

[Andrew Morton <akpm@linux-foundation.org>]

On Wed, 4 Feb 2009 19:42:03 -0800 Andrew Morton <akpm@linux-foundation.org> wrote:

> And I updated seq_file-properly-cope-with-pread.patch thusly:
> 
> --- a/fs/seq_file.c~seq_file-properly-cope-with-pread-fix
> +++ a/fs/seq_file.c
> @@ -48,6 +48,16 @@ int seq_open(struct file *file, const st
>  	 */
>  	file->f_version = 0;
>  
> +	/*
> +	 * seq_files support lseek() and pread().  They do not implement
> +	 * write() at all, but we clear FMODE_PWRITE here for historical
> +	 * reasons.
> +	 *
> +	 * If a client of seq_files a) implements file.write() and b) wishes to
> +	 * support pwrite() then that client will need to implement its own
> +	 * file.open() which calls seq_open() and then sets FMODE_WRITE.
                                                                  ^P
> +	 */
> +	file->f_mode &= ~FMODE_PWRITE;
>  	return 0;
>  }
>  EXPORT_SYMBOL(seq_open);