[S390] dynamic page tables.

Add support for different number of page table levels dependent
on the highest address used for a process. This will cause a 31 bit
process to use a two level page table instead of the four level page
table that is the default after the pud has been introduced. Likewise
a normal 64 bit process will use three levels instead of four. Only
if a process runs out of the 4 tera bytes which can be addressed with
a three level page table the fourth level is dynamically added. Then
the process can use up to 8 peta byte.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 65 insertions, 0 deletions

diff --git a/arch/s390/mm/mmap.c b/arch/s390/mm/mmap.c
index 356257c171de..5932a824547a 100644
--- a/arch/s390/mm/mmap.c
+++ b/arch/s390/mm/mmap.c
@@ -27,6 +27,7 @@
 #include <linux/personality.h>
 #include <linux/mm.h>
 #include <linux/module.h>
+#include <asm/pgalloc.h>
 
 /*
  * Top of mmap area (just below the process stack).
@@ -62,6 +63,8 @@ static inline int mmap_is_legacy(void)
             current->signal->rlim[RLIMIT_STACK].rlim_cur == RLIM_INFINITY;
 }
 
+#ifndef CONFIG_64BIT
+
 /*
  * This function, called very early during the creation of a new
  * process VM image, sets up which VM layout function to use:
@@ -84,3 +87,65 @@ void arch_pick_mmap_layout(struct mm_struct *mm)
 }
 EXPORT_SYMBOL_GPL(arch_pick_mmap_layout);
 
+#else
+
+static unsigned long
+s390_get_unmapped_area(struct file *filp, unsigned long addr,
+                unsigned long len, unsigned long pgoff, unsigned long flags)
+{
+        struct mm_struct *mm = current->mm;
+        int rc;
+
+        addr = arch_get_unmapped_area(filp, addr, len, pgoff, flags);
+        if (addr & ~PAGE_MASK)
+                return addr;
+        if (unlikely(mm->context.asce_limit < addr + len)) {
+                rc = crst_table_upgrade(mm, addr + len);
+                if (rc)
+                        return (unsigned long) rc;
+        }
+        return addr;
+}
+
+static unsigned long
+s390_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
+                          const unsigned long len, const unsigned long pgoff,
+                          const unsigned long flags)
+{
+        struct mm_struct *mm = current->mm;
+        unsigned long addr = addr0;
+        int rc;
+
+        addr = arch_get_unmapped_area_topdown(filp, addr, len, pgoff, flags);
+        if (addr & ~PAGE_MASK)
+                return addr;
+        if (unlikely(mm->context.asce_limit < addr + len)) {
+                rc = crst_table_upgrade(mm, addr + len);
+                if (rc)
+                        return (unsigned long) rc;
+        }
+        return addr;
+}
+/*
+ * This function, called very early during the creation of a new
+ * process VM image, sets up which VM layout function to use:
+ */
+void arch_pick_mmap_layout(struct mm_struct *mm)
+{
+        /*
+         * Fall back to the standard layout if the personality
+         * bit is set, or if the expected stack growth is unlimited:
+         */
+        if (mmap_is_legacy()) {
+                mm->mmap_base = TASK_UNMAPPED_BASE;
+                mm->get_unmapped_area = s390_get_unmapped_area;
+                mm->unmap_area = arch_unmap_area;
+        } else {
+                mm->mmap_base = mmap_base();
+                mm->get_unmapped_area = s390_get_unmapped_area_topdown;
+                mm->unmap_area = arch_unmap_area_topdown;
+        }
+}
+EXPORT_SYMBOL_GPL(arch_pick_mmap_layout);
+
+#endif