mm: Introduce arch_calc_vm_flag_bits()

Similarly to arch_calc_vm_prot_bits(), introduce a dummy
arch_calc_vm_flag_bits() invoked from calc_vm_flag_bits(). This macro
can be overridden by architectures to insert specific VM_* flags derived
from the mmap() MAP_* flags.
Signed-off-by: Kevin Brodsky <Kevin.Brodsky@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>

include/linux/mman.h

@@ -78,13 +78,18 @@ static inline void vm_unacct_memory(long pages)
 }
 
 /*
- * Allow architectures to handle additional protection bits
+ * Allow architectures to handle additional protection and flag bits. The
+ * overriding macros must be defined in the arch-specific asm/mman.h file.
  */
 
 #ifndef arch_calc_vm_prot_bits
 #define arch_calc_vm_prot_bits(prot, pkey) 0
 #endif
 
+#ifndef arch_calc_vm_flag_bits
+#define arch_calc_vm_flag_bits(flags) 0
+#endif
+
 #ifndef arch_vm_get_page_prot
 #define arch_vm_get_page_prot(vm_flags) __pgprot(0)
 #endif
@@ -135,7 +140,8 @@ calc_vm_flag_bits(unsigned long flags)
 	return _calc_vm_trans(flags, MAP_GROWSDOWN,  VM_GROWSDOWN ) |
 	       _calc_vm_trans(flags, MAP_DENYWRITE,  VM_DENYWRITE ) |
 	       _calc_vm_trans(flags, MAP_LOCKED,     VM_LOCKED    ) |
-	       _calc_vm_trans(flags, MAP_SYNC,	     VM_SYNC      );
+	       _calc_vm_trans(flags, MAP_SYNC,	     VM_SYNC      ) |
+	       arch_calc_vm_flag_bits(flags);
 }
 
 unsigned long vm_commit_limit(void);