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

Rusty Russell (rusty@rustcorp.com.au)
Mon, 19 Aug 2002 10:49:29 +1000


On Thu, 15 Aug 2002 17:31:36 -0400
Benjamin LaHaise <bcrl@redhat.com> 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
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