mm/vma: make is_vma_temporary_stack() available for general use

Currently the declaration and definition for is_vma_temporary_stack() are
scattered.  Lets make is_vma_temporary_stack() helper available for
general use and also drop the declaration from (include/linux/huge_mm.h)
which is no longer required.  While at this, rename this as
vma_is_temporary_stack() in line with existing helpers.  This should not
cause any functional change.

Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1582782965-3274-4-git-send-email-anshuman.khandual@arm.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/huge_mm.h

@@ -87,8 +87,6 @@ extern struct kobj_attribute shmem_enabled_attr;
 #define HPAGE_PUD_SIZE	((1UL) << HPAGE_PUD_SHIFT)
 #define HPAGE_PUD_MASK	(~(HPAGE_PUD_SIZE - 1))
 
-extern bool is_vma_temporary_stack(struct vm_area_struct *vma);
-
 extern unsigned long transparent_hugepage_flags;
 
 /*
@@ -100,7 +98,7 @@ static inline bool __transparent_hugepage_enabled(struct vm_area_struct *vma)
 	if (vma->vm_flags & VM_NOHUGEPAGE)
 		return false;
 
-	if (is_vma_temporary_stack(vma))
+	if (vma_is_temporary_stack(vma))
 		return false;
 
 	if (test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags))

include/linux/mm.h

@@ -544,6 +544,20 @@ static inline bool vma_is_anonymous(struct vm_area_struct *vma)
 	return !vma->vm_ops;
 }
 
+static inline bool vma_is_temporary_stack(struct vm_area_struct *vma)
+{
+	int maybe_stack = vma->vm_flags & (VM_GROWSDOWN | VM_GROWSUP);
+
+	if (!maybe_stack)
+		return false;
+
+	if ((vma->vm_flags & VM_STACK_INCOMPLETE_SETUP) ==
+						VM_STACK_INCOMPLETE_SETUP)
+		return true;
+
+	return false;
+}
+
 static inline bool vma_is_foreign(struct vm_area_struct *vma)
 {
 	if (!current->mm)

mm/khugepaged.c

@@ -421,7 +421,7 @@ static bool hugepage_vma_check(struct vm_area_struct *vma,
 	}
 	if (!vma->anon_vma || vma->vm_ops)
 		return false;
-	if (is_vma_temporary_stack(vma))
+	if (vma_is_temporary_stack(vma))
 		return false;
 	return !(vm_flags & VM_NO_KHUGEPAGED);
 }

mm/mremap.c

@@ -133,7 +133,7 @@ static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd,
 	 * such races:
 	 *
 	 * - During exec() shift_arg_pages(), we use a specially tagged vma
-	 *   which rmap call sites look for using is_vma_temporary_stack().
+	 *   which rmap call sites look for using vma_is_temporary_stack().
 	 *
 	 * - During mremap(), new_vma is often known to be placed after vma
 	 *   in rmap traversal order. This ensures rmap will always observe

mm/rmap.c

@@ -1699,23 +1699,9 @@ discard:
 	return ret;
 }
 
-bool is_vma_temporary_stack(struct vm_area_struct *vma)
-{
-	int maybe_stack = vma->vm_flags & (VM_GROWSDOWN | VM_GROWSUP);
-
-	if (!maybe_stack)
-		return false;
-
-	if ((vma->vm_flags & VM_STACK_INCOMPLETE_SETUP) ==
-						VM_STACK_INCOMPLETE_SETUP)
-		return true;
-
-	return false;
-}
-
 static bool invalid_migration_vma(struct vm_area_struct *vma, void *arg)
 {
-	return is_vma_temporary_stack(vma);
+	return vma_is_temporary_stack(vma);
 }
 
 static int page_mapcount_is_zero(struct page *page)