[PATCH v3 2/2] mm/damon: introduce DAMOS filter type hugepage

[Usama Arif <usamaarif642@gmail.com>]

This is to gather statistics to check if memory regions of specific
access tempratures are backed by hugepages. This includes both THPs
and hugetlbfs.
This filter can help to observe and prove the effectivenes of
different schemes for shrinking/collapsing hugepages.

Signed-off-by: Usama Arif <usamaarif642@gmail.com>
---
v2 -> v3:
- expose hugepage via sysfs even if the kernel is
  built without hugepage support. DAMON will just
  just return 0. (SJ Park)

v1 -> v2:
- Wrap DAMOS_FILTER_TYPE_HUGEPAGE case with
  CONFIG_PGTABLE_HAS_HUGE_LEAVES (SJ Park)
---
 include/linux/damon.h    | 2 ++
 mm/damon/paddr.c         | 5 +++++
 mm/damon/sysfs-schemes.c | 1 +
 3 files changed, 8 insertions(+)

diff --git a/include/linux/damon.h b/include/linux/damon.h
index af525252b853..1d94d7d88b36 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -326,6 +326,7 @@ struct damos_stat {
  * @DAMOS_FILTER_TYPE_ANON:	Anonymous pages.
  * @DAMOS_FILTER_TYPE_MEMCG:	Specific memcg's pages.
  * @DAMOS_FILTER_TYPE_YOUNG:	Recently accessed pages.
+ * @DAMOS_FILTER_TYPE_HUGEPAGE:	Page is part of a hugepage.
  * @DAMOS_FILTER_TYPE_ADDR:	Address range.
  * @DAMOS_FILTER_TYPE_TARGET:	Data Access Monitoring target.
  * @NR_DAMOS_FILTER_TYPES:	Number of filter types.
@@ -345,6 +346,7 @@ enum damos_filter_type {
 	DAMOS_FILTER_TYPE_ANON,
 	DAMOS_FILTER_TYPE_MEMCG,
 	DAMOS_FILTER_TYPE_YOUNG,
+	DAMOS_FILTER_TYPE_HUGEPAGE,
 	DAMOS_FILTER_TYPE_ADDR,
 	DAMOS_FILTER_TYPE_TARGET,
 	NR_DAMOS_FILTER_TYPES,
diff --git a/mm/damon/paddr.c b/mm/damon/paddr.c
index c0ccf4fade24..224308140441 100644
--- a/mm/damon/paddr.c
+++ b/mm/damon/paddr.c
@@ -222,6 +222,11 @@ static bool damos_pa_filter_match(struct damos_filter *filter,
 		if (matched)
 			damon_folio_mkold(folio);
 		break;
+#if defined(CONFIG_PGTABLE_HAS_HUGE_LEAVES)
+	case DAMOS_FILTER_TYPE_HUGEPAGE:
+		matched = folio_size(folio) == HPAGE_PMD_SIZE;
+		break;
+#endif
 	default:
 		break;
 	}
diff --git a/mm/damon/sysfs-schemes.c b/mm/damon/sysfs-schemes.c
index 98f93ae9f59e..de9265f7ccde 100644
--- a/mm/damon/sysfs-schemes.c
+++ b/mm/damon/sysfs-schemes.c
@@ -329,6 +329,7 @@ static const char * const damon_sysfs_scheme_filter_type_strs[] = {
 	"anon",
 	"memcg",
 	"young",
+	"hugepage",
 	"addr",
 	"target",
 };
-- 
2.43.5