[S390] vmalloc: add vmalloc kernel parameter support

With the kernel parameter 'vmalloc=<size>' the size of the vmalloc area
can be specified. This can be used to increase or decrease the size of
the area. Works in the same way as on some other architectures.
This can be useful for features which make excessive use of vmalloc and
wouldn't work otherwise.
The default sizes remain unchanged: 96MB for 31 bit kernels and 1GB for
64 bit kernels.
Signed-off-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/include/asm/pgtable.h

@@ -112,12 +112,15 @@ extern char empty_zero_page[PAGE_SIZE];
  * effect, this also makes sure that 64 bit module code cannot be used
  * as system call address.
  */
+
+extern unsigned long VMALLOC_START;
+
 #ifndef __s390x__
-#define VMALLOC_START	0x78000000UL
+#define VMALLOC_SIZE	(96UL << 20)
 #define VMALLOC_END	0x7e000000UL
 #define VMEM_MAP_END	0x80000000UL
 #else /* __s390x__ */
-#define VMALLOC_START	0x3e000000000UL
+#define VMALLOC_SIZE	(1UL << 30)
 #define VMALLOC_END	0x3e040000000UL
 #define VMEM_MAP_END	0x40000000000UL
 #endif /* __s390x__ */

arch/s390/mm/pgtable.c

 /*
- *  arch/s390/mm/pgtable.c
- *
- *    Copyright IBM Corp. 2007
+ *    Copyright IBM Corp. 2007,2009
  *    Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>
  */
 
@@ -53,6 +51,18 @@ void clear_table_pgstes(unsigned long *table)
 
 #endif
 
+unsigned long VMALLOC_START = VMALLOC_END - VMALLOC_SIZE;
+EXPORT_SYMBOL(VMALLOC_START);
+
+static int __init parse_vmalloc(char *arg)
+{
+	if (!arg)
+		return -EINVAL;
+	VMALLOC_START = (VMALLOC_END - memparse(arg, &arg)) & PAGE_MASK;
+	return 0;
+}
+early_param("vmalloc", parse_vmalloc);
+
 unsigned long *crst_table_alloc(struct mm_struct *mm, int noexec)
 {
 	struct page *page = alloc_pages(GFP_KERNEL, ALLOC_ORDER);