Re: [patch] v2.5.31 nfsctl.c stack usage reduction

[Rusty Russell]

On Thu, 15 Aug 2002 17:31:36 -0400
Benjamin LaHaise <[e-mail]> wrote:

> Heyo,
> 
> The patch below (which depends on the copy_from_user_kmalloc addition) 
> reduces the stack usage in nfsctl.c, which was allocating structures that 
> were 2KB or more on the stack.
> 
> 		-ben
> 
> :r ~/patches/v2.5/v2.5.31-stack-nfs.diff
> diff -urN foo-v2.5.31/fs/nfsd/nfsctl.c bar-v2.5.31/fs/nfsd/nfsctl.c
> --- foo-v2.5.31/fs/nfsd/nfsctl.c	Tue Jul 30 10:24:17 2002
> +++ bar-v2.5.31/fs/nfsd/nfsctl.c	Thu Aug 15 17:26:09 2002
> @@ -155,56 +155,47 @@
>   * payload - write methods
>   */
>  
> +/* Rather than duplicate this many times, just use a funky macro. */
> +#define WRITE_METHOD(type, fn)		\
> +	type *data;			\
> +	ssize_t ret;			\
> +	if (size < sizeof(*data))	\
> +		return -EINVAL;		\
> +	data = copy_from_user_kmalloc(buf, size);\
> +	if (IS_ERR(data))		\
> +		return PTR_ERR(data);	\
> +	ret = fn;			\
> +	kfree(data);			\
> +	return ret;
> +

One tiny request: make the macro an expression statement, and then use it
as "return WRITE_METHOD(xxx, yyy)".

Or even an inline function taking void * and a size.

Let's not encourage people to do returns in macros 8)

Thanks!
Rusty.
-- 
   there are those who do and those who hang on and you don't see too
   many doers quoting their contemporaries.  -- Larry McVoy