mm: arch: make get_gate_vma take an mm_struct instead of a task_struct

Morally, the presence of a gate vma is more an attribute of a particular mm than
a particular task.  Moreover, dropping the dependency on task_struct will help
make both existing and future operations on mm's more flexible and convenient.

Signed-off-by: Stephen Wilson <wilsons@start.ca>
Reviewed-by: Michel Lespinasse <walken@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/mm/mlock.c b/mm/mlock.c
index c3924c7f..2689a08c 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -237,7 +237,7 @@
 
 	if (!((vma->vm_flags & (VM_DONTEXPAND | VM_RESERVED)) ||
 			is_vm_hugetlb_page(vma) ||
-			vma == get_gate_vma(current))) {
+			vma == get_gate_vma(current->mm))) {
 
 		__mlock_vma_pages_range(vma, start, end, NULL);
 
@@ -332,7 +332,7 @@
 	int lock = newflags & VM_LOCKED;
 
 	if (newflags == vma->vm_flags || (vma->vm_flags & VM_SPECIAL) ||
-	    is_vm_hugetlb_page(vma) || vma == get_gate_vma(current))
+	    is_vm_hugetlb_page(vma) || vma == get_gate_vma(current->mm))
 		goto out;	/* don't set VM_LOCKED,  don't count */
 
 	pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);