mm: cleanup count_mthp_stat() definition

Patch series "Shmem mTHP controls and stats improvements", v3.

This is a small series to tidy up the way the shmem controls and stats are
exposed.  These patches were previously part of the series at [2], but I
decided to split them out since they can go in independently.


This patch (of 2):

Let's move count_mthp_stat() so that it's always defined, even when THP is
disabled.  Previously uses of the function in files such as shmem.c, which
are compiled even when THP is disabled, required ugly THP ifdeferry.  With
this cleanup, we can remove those ifdefs and the function resolves to a
nop when THP is disabled.

I shortly plan to call count_mthp_stat() from more THP-invariant source
files.

Link: https://lkml.kernel.org/r/20240808111849.651867-1-ryan.roberts@arm.com
Link: https://lkml.kernel.org/r/20240808111849.651867-2-ryan.roberts@arm.com
Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
Acked-by: Barry Song <baohua@kernel.org>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Lance Yang <ioworker0@gmail.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Gavin Shan <gshan@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/linux/huge_mm.h

@@ -114,6 +114,41 @@ extern struct kobj_attribute thpsize_shmem_enabled_attr;
 #define HPAGE_PUD_MASK	(~(HPAGE_PUD_SIZE - 1))
 #define HPAGE_PUD_SIZE	((1UL) << HPAGE_PUD_SHIFT)
 
+enum mthp_stat_item {
+	MTHP_STAT_ANON_FAULT_ALLOC,
+	MTHP_STAT_ANON_FAULT_FALLBACK,
+	MTHP_STAT_ANON_FAULT_FALLBACK_CHARGE,
+	MTHP_STAT_SWPOUT,
+	MTHP_STAT_SWPOUT_FALLBACK,
+	MTHP_STAT_SHMEM_ALLOC,
+	MTHP_STAT_SHMEM_FALLBACK,
+	MTHP_STAT_SHMEM_FALLBACK_CHARGE,
+	MTHP_STAT_SPLIT,
+	MTHP_STAT_SPLIT_FAILED,
+	MTHP_STAT_SPLIT_DEFERRED,
+	__MTHP_STAT_COUNT
+};
+
+#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && defined(CONFIG_SYSFS)
+struct mthp_stat {
+	unsigned long stats[ilog2(MAX_PTRS_PER_PTE) + 1][__MTHP_STAT_COUNT];
+};
+
+DECLARE_PER_CPU(struct mthp_stat, mthp_stats);
+
+static inline void count_mthp_stat(int order, enum mthp_stat_item item)
+{
+	if (order <= 0 || order > PMD_ORDER)
+		return;
+
+	this_cpu_inc(mthp_stats.stats[order][item]);
+}
+#else
+static inline void count_mthp_stat(int order, enum mthp_stat_item item)
+{
+}
+#endif
+
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 
 extern unsigned long transparent_hugepage_flags;
@@ -269,41 +304,6 @@ struct thpsize {
 
 #define to_thpsize(kobj) container_of(kobj, struct thpsize, kobj)
 
-enum mthp_stat_item {
-	MTHP_STAT_ANON_FAULT_ALLOC,
-	MTHP_STAT_ANON_FAULT_FALLBACK,
-	MTHP_STAT_ANON_FAULT_FALLBACK_CHARGE,
-	MTHP_STAT_SWPOUT,
-	MTHP_STAT_SWPOUT_FALLBACK,
-	MTHP_STAT_SHMEM_ALLOC,
-	MTHP_STAT_SHMEM_FALLBACK,
-	MTHP_STAT_SHMEM_FALLBACK_CHARGE,
-	MTHP_STAT_SPLIT,
-	MTHP_STAT_SPLIT_FAILED,
-	MTHP_STAT_SPLIT_DEFERRED,
-	__MTHP_STAT_COUNT
-};
-
-struct mthp_stat {
-	unsigned long stats[ilog2(MAX_PTRS_PER_PTE) + 1][__MTHP_STAT_COUNT];
-};
-
-#ifdef CONFIG_SYSFS
-DECLARE_PER_CPU(struct mthp_stat, mthp_stats);
-
-static inline void count_mthp_stat(int order, enum mthp_stat_item item)
-{
-	if (order <= 0 || order > PMD_ORDER)
-		return;
-
-	this_cpu_inc(mthp_stats.stats[order][item]);
-}
-#else
-static inline void count_mthp_stat(int order, enum mthp_stat_item item)
-{
-}
-#endif
-
 #define transparent_hugepage_use_zero_page()				\
 	(transparent_hugepage_flags &					\
 	 (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG))

mm/memory.c

@@ -4595,9 +4595,7 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf)
 
 	folio_ref_add(folio, nr_pages - 1);
 	add_mm_counter(vma->vm_mm, MM_ANONPAGES, nr_pages);
-#ifdef CONFIG_TRANSPARENT_HUGEPAGE
 	count_mthp_stat(folio_order(folio), MTHP_STAT_ANON_FAULT_ALLOC);
-#endif
 	folio_add_new_anon_rmap(folio, vma, addr, RMAP_EXCLUSIVE);
 	folio_add_lru_vma(folio, vma);
 setpte:

mm/shmem.c

@@ -1808,9 +1808,7 @@ static struct folio *shmem_alloc_and_add_folio(struct vm_fault *vmf,
 
 			if (pages == HPAGE_PMD_NR)
 				count_vm_event(THP_FILE_FALLBACK);
-#ifdef CONFIG_TRANSPARENT_HUGEPAGE
 			count_mthp_stat(order, MTHP_STAT_SHMEM_FALLBACK);
-#endif
 			order = next_order(&suitable_orders, order);
 		}
 	} else {
@@ -1835,10 +1833,8 @@ static struct folio *shmem_alloc_and_add_folio(struct vm_fault *vmf,
 				count_vm_event(THP_FILE_FALLBACK);
 				count_vm_event(THP_FILE_FALLBACK_CHARGE);
 			}
-#ifdef CONFIG_TRANSPARENT_HUGEPAGE
 			count_mthp_stat(folio_order(folio), MTHP_STAT_SHMEM_FALLBACK);
 			count_mthp_stat(folio_order(folio), MTHP_STAT_SHMEM_FALLBACK_CHARGE);
-#endif
 		}
 		goto unlock;
 	}
@@ -2332,9 +2328,7 @@ static int shmem_get_folio_gfp(struct inode *inode, pgoff_t index,
 		if (!IS_ERR(folio)) {
 			if (folio_test_pmd_mappable(folio))
 				count_vm_event(THP_FILE_ALLOC);
-#ifdef CONFIG_TRANSPARENT_HUGEPAGE
 			count_mthp_stat(folio_order(folio), MTHP_STAT_SHMEM_ALLOC);
-#endif
 			goto alloced;
 		}
 		if (PTR_ERR(folio) == -EEXIST)