switch do_brk() to get_unmapped_area()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

mm/mmap.c

@@ -1985,20 +1985,14 @@ unsigned long do_brk(unsigned long addr, unsigned long len)
 	if (!len)
 		return addr;
 
-	if ((addr + len) > TASK_SIZE || (addr + len) < addr)
-		return -EINVAL;
-
-	if (is_hugepage_only_range(mm, addr, len))
-		return -EINVAL;
-
 	error = security_file_mmap(NULL, 0, 0, 0, addr, 1);
 	if (error)
 		return error;
 
 	flags = VM_DATA_DEFAULT_FLAGS | VM_ACCOUNT | mm->def_flags;
 
-	error = arch_mmap_check(addr, len, flags);
-	if (error)
+	error = get_unmapped_area(NULL, addr, len, 0, MAP_FIXED);
+	if (error & ~PAGE_MASK)
 		return error;
 
 	/*