[RFC PATCH v2 27/30] mm: thp: make PUD THP size public.

[Zi Yan <zi.yan@sent.com>]

From: Zi Yan <ziy@nvidia.com>

User can access the PUD THP size via
`cat /sys/kernel/mm/transparent_hugepage/hpage_pud_size`. This is
similar to make PMD THP size public.

Signed-off-by: Zi Yan <ziy@nvidia.com>
---
 Documentation/admin-guide/mm/transhuge.rst |  1 +
 mm/huge_memory.c                           | 13 +++++++++++++
 2 files changed, 14 insertions(+)

diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst
index b2acd0d395ca..11b173c2650e 100644
--- a/Documentation/admin-guide/mm/transhuge.rst
+++ b/Documentation/admin-guide/mm/transhuge.rst
@@ -159,6 +159,7 @@ Some userspace (such as a test program, or an optimized memory allocation
 library) may want to know the size (in bytes) of a transparent hugepage::
 
 	cat /sys/kernel/mm/transparent_hugepage/hpage_pmd_size
+	cat /sys/kernel/mm/transparent_hugepage/hpage_pud_size
 
 khugepaged will be automatically started when
 transparent_hugepage/enabled is set to "always" or "madvise, and it'll
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 1965753b31a2..20ecffc27396 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -340,12 +340,25 @@ static ssize_t hpage_pmd_size_show(struct kobject *kobj,
 static struct kobj_attribute hpage_pmd_size_attr =
 	__ATTR_RO(hpage_pmd_size);
 
+#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
+static ssize_t hpage_pud_size_show(struct kobject *kobj,
+		struct kobj_attribute *attr, char *buf)
+{
+	return sprintf(buf, "%lu\n", HPAGE_PUD_SIZE);
+}
+static struct kobj_attribute hpage_pud_size_attr =
+	__ATTR_RO(hpage_pud_size);
+#endif
+
 static struct attribute *hugepage_attr[] = {
 	&enabled_attr.attr,
 	&enabled_pud_thp_attr.attr,
 	&defrag_attr.attr,
 	&use_zero_page_attr.attr,
 	&hpage_pmd_size_attr.attr,
+#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
+	&hpage_pud_size_attr.attr,
+#endif
 #ifdef CONFIG_SHMEM
 	&shmem_enabled_attr.attr,
 #endif
-- 
2.28.0