mm: improve readability of transparent_hugepage_enabled()

Turn the macro into a static inline and rewrite the condition checks for
better readability in preparation for adding another condition.

[ross.zwisler@linux.intel.com: fix logic to make conversion equivalent]
[akpm@linux-foundation.org: resolve vs mm-make-pr_set_thp_disable-immediately-active.patch]
[akpm@linux-foundation.org: include coredump.h for MMF_DISABLE_THP]
Link: http://lkml.kernel.org/r/149739530612.20686.14760671150202647861.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Acked-by: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/huge_mm.h

@@ -1,6 +1,8 @@
 #ifndef _LINUX_HUGE_MM_H
 #define _LINUX_HUGE_MM_H
 
+#include <linux/sched/coredump.h>
+
 extern int do_huge_pmd_anonymous_page(struct vm_fault *vmf);
 extern int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
 			 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
@@ -85,15 +87,29 @@ extern struct kobj_attribute shmem_enabled_attr;
 
 extern bool is_vma_temporary_stack(struct vm_area_struct *vma);
 
-#define transparent_hugepage_enabled(__vma)				\
-	((transparent_hugepage_flags &					\
-	  (1<<TRANSPARENT_HUGEPAGE_FLAG) ||				\
-	  (transparent_hugepage_flags &					\
-	   (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG) &&			\
-	   ((__vma)->vm_flags & VM_HUGEPAGE))) &&			\
-	 !((__vma)->vm_flags & VM_NOHUGEPAGE) &&			\
-	 !test_bit(MMF_DISABLE_THP, &(__vma)->vm_mm->flags) &&		\
-	 !is_vma_temporary_stack(__vma))
+extern unsigned long transparent_hugepage_flags;
+
+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))
+		return false;
+
+	if (test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags))
+		return false;
+
+	if (transparent_hugepage_flags & (1 << TRANSPARENT_HUGEPAGE_FLAG))
+		return true;
+
+	if (transparent_hugepage_flags &
+				(1 << TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG))
+		return !!(vma->vm_flags & VM_HUGEPAGE);
+
+	return false;
+}
+
 #define transparent_hugepage_use_zero_page()				\
 	(transparent_hugepage_flags &					\
 	 (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG))
@@ -105,8 +121,6 @@ extern bool is_vma_temporary_stack(struct vm_area_struct *vma);
 #define transparent_hugepage_debug_cow() 0
 #endif /* CONFIG_DEBUG_VM */
 
-extern unsigned long transparent_hugepage_flags;
-
 extern unsigned long thp_get_unmapped_area(struct file *filp,
 		unsigned long addr, unsigned long len, unsigned long pgoff,
 		unsigned long flags);
@@ -225,7 +239,10 @@ void mm_put_huge_zero_page(struct mm_struct *mm);
 
 #define hpage_nr_pages(x) 1
 
-#define transparent_hugepage_enabled(__vma) 0
+static inline bool transparent_hugepage_enabled(struct vm_area_struct *vma)
+{
+	return false;
+}
 
 static inline void prep_transhuge_page(struct page *page) {}