x86, mm: Separate x86_64 vmalloc_sync_all() into separate functions

No behavior change.

Move some of vmalloc_sync_all() code into a new function
sync_global_pgds() that will be useful for memory hotplug.

Signed-off-by: Haicheng Li <haicheng.li@linux.intel.com>
LKML-Reference: <4C6E4ECD.1090607@linux.intel.com>
Reviewed-by: Wu Fengguang <fengguang.wu@intel.com>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

arch/x86/mm/init_64.c

@@ -97,6 +97,36 @@ static int __init nonx32_setup(char *str)
 }
 __setup("noexec32=", nonx32_setup);
 
+/*
+ * When memory was added/removed make sure all the processes MM have
+ * suitable PGD entries in the local PGD level page.
+ */
+void sync_global_pgds(unsigned long start, unsigned long end)
+{
+       unsigned long address;
+
+       for (address = start; address <= end; address += PGDIR_SIZE) {
+	       const pgd_t *pgd_ref = pgd_offset_k(address);
+	       unsigned long flags;
+	       struct page *page;
+
+	       if (pgd_none(*pgd_ref))
+		       continue;
+
+	       spin_lock_irqsave(&pgd_lock, flags);
+	       list_for_each_entry(page, &pgd_list, lru) {
+		       pgd_t *pgd;
+		       pgd = (pgd_t *)page_address(page) + pgd_index(address);
+		       if (pgd_none(*pgd))
+			       set_pgd(pgd, *pgd_ref);
+		       else
+			       BUG_ON(pgd_page_vaddr(*pgd)
+					!= pgd_page_vaddr(*pgd_ref));
+	       }
+	       spin_unlock_irqrestore(&pgd_lock, flags);
+       }
+}
+
 /*
  * NOTE: This function is marked __ref because it calls __init function
  * (alloc_bootmem_pages). It's safe to do it ONLY when after_bootmem == 0.