2002-08-15 21:27:42

by Benjamin LaHaise

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

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;

2002-08-19 03:11:53

by Rusty Russell

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

On Thu, 15 Aug 2002 17:31:36 -0400
Benjamin LaHaise <[email protected]> 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