mm: convert vma_lookup() to use mtree_load()

Unlike the rbtree, the Maple Tree will return a NULL if there's nothing at
a particular address.

Since the previous commit dropped the vmacache, it is now possible to
consult the tree directly.

Link: https://lkml.kernel.org/r/20220906194824.2110408-27-Liam.Howlett@oracle.comSigned-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Tested-by: Yu Zhao <yuzhao@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: SeongJae Park <sj@kernel.org>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/linux/mm.h

@@ -2795,12 +2795,7 @@ struct vm_area_struct *find_vma_intersection(struct mm_struct *mm,
 static inline
 struct vm_area_struct *vma_lookup(struct mm_struct *mm, unsigned long addr)
 {
-	struct vm_area_struct *vma = find_vma(mm, addr);
-
-	if (vma && addr < vma->vm_start)
-		vma = NULL;
-
-	return vma;
+	return mtree_load(&mm->mm_mt, addr);
 }
 
 static inline unsigned long vm_start_gap(struct vm_area_struct *vma)