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

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

[Benjamin LaHaise]

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;
+
 static ssize_t write_svc(struct file *file, const char *buf, size_t size)
 {
-	struct nfsctl_svc data;
-	if (size < sizeof(data))
-		return -EINVAL;
-	if (copy_from_user(&data, buf, size))
-		return -EFAULT;
-	return nfsd_svc(data.svc_port, data.svc_nthreads);
+	WRITE_METHOD(struct nfsctl_svc,
+		     nfsd_svc(data->svc_port, data->svc_nthreads));
 }
 
 static ssize_t write_add(struct file *file, const char *buf, size_t size)
 {
-	struct nfsctl_client data;
-	if (size < sizeof(data))
-		return -EINVAL;
-	if (copy_from_user(&data, buf, size))
-		return -EFAULT;
-	return exp_addclient(&data);
+	WRITE_METHOD(struct nfsctl_client, exp_addclient(data));
 }
 
 static ssize_t write_del(struct file *file, const char *buf, size_t size)
 {
-	struct nfsctl_client data;
-	if (size < sizeof(data))
-		return -EINVAL;
-	if (copy_from_user(&data, buf, size))
-		return -EFAULT;
-	return exp_delclient(&data);
+	WRITE_METHOD(struct nfsctl_client, exp_delclient(data));
 }
 
 static ssize_t write_export(struct file *file, const char *buf, size_t size)
 {
-	struct nfsctl_export data;
-	if (size < sizeof(data))
-		return -EINVAL;
-	if (copy_from_user(&data, buf, size))
-		return -EFAULT;
-	return exp_export(&data);
+	WRITE_METHOD(struct nfsctl_export, exp_export(data));
 }
 
 static ssize_t write_unexport(struct file *file, const char *buf, size_t size)
 {
-	struct nfsctl_export data;
-	if (size < sizeof(data))
-		return -EINVAL;
-	if (copy_from_user(&data, buf, size))
-		return -EFAULT;
-	return exp_unexport(&data);
+	WRITE_METHOD(struct nfsctl_export, exp_unexport(data));
 }
 
+#undef WRITE_METHOD
+
 static ssize_t write_getfs(struct file *file, const char *buf, size_t size)
 {
 	struct nfsctl_fsparm data;

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

[Rusty Russell]

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