mm/mmap: drop arch_filter_pgprot()

There are no platforms left which subscribe ARCH_HAS_FILTER_PGPROT.  Hence
drop generic arch_filter_pgprot() and also config ARCH_HAS_FILTER_PGPROT.

Link: https://lkml.kernel.org/r/20220414062125.609297-7-anshuman.khandual@arm.com
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Khalid Aziz <khalid.aziz@oracle.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/Kconfig

@@ -762,9 +762,6 @@ config ARCH_HAS_CURRENT_STACK_POINTER
 	  register alias named "current_stack_pointer", this config can be
 	  selected.
 
-config ARCH_HAS_FILTER_PGPROT
-	bool
-
 config ARCH_HAS_VM_GET_PAGE_PROT
 	bool
 

mm/mmap.c

@@ -121,20 +121,11 @@ pgprot_t protection_map[16] __ro_after_init = {
 };
 
 #ifndef CONFIG_ARCH_HAS_VM_GET_PAGE_PROT
-#ifndef CONFIG_ARCH_HAS_FILTER_PGPROT
-static inline pgprot_t arch_filter_pgprot(pgprot_t prot)
-{
-	return prot;
-}
-#endif
-
 pgprot_t vm_get_page_prot(unsigned long vm_flags)
 {
-	pgprot_t ret = __pgprot(pgprot_val(protection_map[vm_flags &
-				(VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)]) |
+	return __pgprot(pgprot_val(protection_map[vm_flags &
+			(VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)]) |
 			pgprot_val(arch_vm_get_page_prot(vm_flags)));
-
-	return arch_filter_pgprot(ret);
 }
 EXPORT_SYMBOL(vm_get_page_prot);
 #endif	/* CONFIG_ARCH_HAS_VM_GET_PAGE_PROT */