From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>

Add APIs that allow reading and writing of

/sys/kernel/mm/hugepages/hugepages-NkB/nr_hugepages

to detect and change the amount of HugeTLB pages of different sizes.

Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
---
 .../testing/selftests/mm/hugepage_settings.c  | 25 +++++++++++++++++++
 .../testing/selftests/mm/hugepage_settings.h  | 23 +++++++++++++++++
 2 files changed, 48 insertions(+)

diff --git a/tools/testing/selftests/mm/hugepage_settings.c b/tools/testing/selftests/mm/hugepage_settings.c
index 8f563315b1fc..5961229b9931 100644
--- a/tools/testing/selftests/mm/hugepage_settings.c
+++ b/tools/testing/selftests/mm/hugepage_settings.c
@@ -464,3 +464,28 @@ unsigned long get_free_hugepages(void)
 	fclose(f);
 	return fhp;
 }
+
+static void hugetlb_sysfs_path(char *buf, size_t buflen,
+			       unsigned long size, const char *attr)
+{
+	snprintf(buf, buflen, "/sys/kernel/mm/hugepages/hugepages-%lukB/%s",
+		 size / 1024, attr);
+}
+
+unsigned long hugetlb_nr_pages(unsigned long size)
+{
+	char path[PATH_MAX];
+
+	hugetlb_sysfs_path(path, sizeof(path), size, "nr_hugepages");
+
+	return read_num(path);
+}
+
+void hugetlb_set_nr_pages(unsigned long size, unsigned long nr)
+{
+	char path[PATH_MAX];
+
+	hugetlb_sysfs_path(path, sizeof(path), size, "nr_hugepages");
+
+	write_num(path, nr);
+}
diff --git a/tools/testing/selftests/mm/hugepage_settings.h b/tools/testing/selftests/mm/hugepage_settings.h
index 9357d07e6c1b..d6f41a45e8ee 100644
--- a/tools/testing/selftests/mm/hugepage_settings.h
+++ b/tools/testing/selftests/mm/hugepage_settings.h
@@ -94,4 +94,27 @@ int detect_hugetlb_page_sizes(unsigned long sizes[], int max);
 unsigned long default_huge_page_size(void);
 unsigned long get_free_hugepages(void);
 
+unsigned long hugetlb_nr_pages(unsigned long size);
+void hugetlb_set_nr_pages(unsigned long size, unsigned long nr);
+
+static inline unsigned long hugetlb_nr_default_pages(void)
+{
+	unsigned long size = default_huge_page_size();
+
+	if (!size)
+		return 0;
+
+	return hugetlb_nr_pages(size);
+}
+
+static inline void hugetlb_set_nr_default_pages(unsigned long nr)
+{
+	unsigned long size = default_huge_page_size();
+
+	if (!size)
+		return;
+
+	hugetlb_set_nr_pages(size, nr);
+}
+
 #endif /* __THP_SETTINGS_H__ */
-- 
2.53.0