Revert "x86/mm: Remove unused __set_memory_prot()"

This reverts commit 693bbf2 as kdump LUKS
support (CONFIG_CRASH_DM_CRYPT) depends on __set_memory_prot.

[[email protected]: x86 set_memory.h needs pgtable_types.h]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Coiby Xu <[email protected]>
Cc: Baoquan He <[email protected]>
Cc: "Daniel P. Berrange" <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Dave Young <[email protected]>
Cc: Jan Pazdziora <[email protected]>
Cc: Liu Pingfan <[email protected]>
Cc: Milan Broz <[email protected]>
Cc: Ondrej Kozina <[email protected]>
Cc: Vitaly Kuznetsov <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: coiby

arch/x86/include/asm/set_memory.h

@@ -4,6 +4,7 @@
 
 #include <asm/page.h>
 #include <asm-generic/set_memory.h>
+#include <asm/pgtable.h>
 
 #define set_memory_rox set_memory_rox
 int set_memory_rox(unsigned long addr, int numpages);
@@ -37,6 +38,7 @@ int set_memory_rox(unsigned long addr, int numpages);
  * The caller is required to take care of these.
  */
 
+int __set_memory_prot(unsigned long addr, int numpages, pgprot_t prot);
 int _set_memory_uc(unsigned long addr, int numpages);
 int _set_memory_wc(unsigned long addr, int numpages);
 int _set_memory_wt(unsigned long addr, int numpages);

arch/x86/mm/pat/set_memory.c

@@ -2148,6 +2148,19 @@ static inline int cpa_clear_pages_array(struct page **pages, int numpages,
 		CPA_PAGES_ARRAY, pages);
 }
 
+/*
+ * __set_memory_prot is an internal helper for callers that have been passed
+ * a pgprot_t value from upper layers and a reservation has already been taken.
+ * If you want to set the pgprot to a specific page protocol, use the
+ * set_memory_xx() functions.
+ */
+int __set_memory_prot(unsigned long addr, int numpages, pgprot_t prot)
+{
+	return change_page_attr_set_clr(&addr, numpages, prot,
+					__pgprot(~pgprot_val(prot)), 0, 0,
+					NULL);
+}
+
 int _set_memory_uc(unsigned long addr, int numpages)
 {
 	/*