vmalloc: add @align to vm_area_register_early()

Impact: allow larger alignment for early vmalloc area allocation

Some early vmalloc users might want larger alignment, for example, for
custom large page mapping.  Add @align to vm_area_register_early().
While at it, drop docbook comment on non-existent @size.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>

arch/alpha/mm/init.c

@@ -200,7 +200,7 @@ callback_init(void * kernel_end)
 		/* register the vm area */
 		console_remap_vm.flags = VM_ALLOC;
 		console_remap_vm.size = nr_pages << PAGE_SHIFT;
-		vm_area_register_early(&console_remap_vm);
+		vm_area_register_early(&console_remap_vm, PAGE_SIZE);
 
 		vaddr = (unsigned long)consle_remap_vm.addr;
 

include/linux/vmalloc.h

@@ -109,6 +109,6 @@ extern long vwrite(char *buf, char *addr, unsigned long count);
  */
 extern rwlock_t vmlist_lock;
 extern struct vm_struct *vmlist;
-extern __init void vm_area_register_early(struct vm_struct *vm);
+extern __init void vm_area_register_early(struct vm_struct *vm, size_t align);
 
 #endif /* _LINUX_VMALLOC_H */

mm/percpu.c

@@ -860,7 +860,7 @@ size_t __init pcpu_setup_static(pcpu_populate_pte_fn_t populate_pte_fn,
 	/* init and register vm area */
 	static_vm.flags = VM_ALLOC;
 	static_vm.size = pcpu_chunk_size;
-	vm_area_register_early(&static_vm);
+	vm_area_register_early(&static_vm, PAGE_SIZE);
 
 	/* init static_chunk */
 	static_chunk = alloc_bootmem(pcpu_chunk_struct_size);

mm/vmalloc.c

@@ -995,7 +995,7 @@ EXPORT_SYMBOL(vm_map_ram);
 /**
  * vm_area_register_early - register vmap area early during boot
  * @vm: vm_struct to register
- * @size: size of area to register
+ * @align: requested alignment
  *
  * This function is used to register kernel vm area before
  * vmalloc_init() is called.  @vm->size and @vm->flags should contain
@@ -1004,12 +1004,15 @@ EXPORT_SYMBOL(vm_map_ram);
  *
  * DO NOT USE THIS FUNCTION UNLESS YOU KNOW WHAT YOU'RE DOING.
  */
-void __init vm_area_register_early(struct vm_struct *vm)
+void __init vm_area_register_early(struct vm_struct *vm, size_t align)
 {
 	static size_t vm_init_off __initdata;
+	unsigned long addr;
+
+	addr = ALIGN(VMALLOC_START + vm_init_off, align);
+	vm_init_off = PFN_ALIGN(addr + vm->size) - VMALLOC_START;
 
-	vm->addr = (void *)VMALLOC_START + vm_init_off;
-	vm_init_off = PFN_ALIGN(vm_init_off + vm->size);
+	vm->addr = (void *)addr;
 
 	vm->next = vmlist;
 	vmlist = vm;