[PATCH 1/2] mm/damon: implement a new DAMOS filter type for unmapped pages

[SeongJae Park <sj@kernel.org>]

Implement yet another DAMOS filter type for unmapped pages on DAMON
kernel API, and add support of it from the physical address space DAMON
operations set (paddr).  Since it is for only unmapped pages, support
from the virtual address spaces DAMON operations set (vaddr) is not
required.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 include/linux/damon.h    | 2 ++
 mm/damon/paddr.c         | 3 +++
 mm/damon/sysfs-schemes.c | 1 +
 3 files changed, 6 insertions(+)

diff --git a/include/linux/damon.h b/include/linux/damon.h
index 0ed84b3656fc..795ca09b1107 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -337,6 +337,7 @@ struct damos_stat {
  * @DAMOS_FILTER_TYPE_MEMCG:	Specific memcg's pages.
  * @DAMOS_FILTER_TYPE_YOUNG:	Recently accessed pages.
  * @DAMOS_FILTER_TYPE_HUGEPAGE_SIZE:	Page is part of a hugepage.
+ * @DAMOS_FILTER_TYPE_UNMAPPED:	Unmapped pages.
  * @DAMOS_FILTER_TYPE_ADDR:	Address range.
  * @DAMOS_FILTER_TYPE_TARGET:	Data Access Monitoring target.
  * @NR_DAMOS_FILTER_TYPES:	Number of filter types.
@@ -357,6 +358,7 @@ enum damos_filter_type {
 	DAMOS_FILTER_TYPE_MEMCG,
 	DAMOS_FILTER_TYPE_YOUNG,
 	DAMOS_FILTER_TYPE_HUGEPAGE_SIZE,
+	DAMOS_FILTER_TYPE_UNMAPPED,
 	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 9f03e1980b8d..25090230da17 100644
--- a/mm/damon/paddr.c
+++ b/mm/damon/paddr.c
@@ -236,6 +236,9 @@ static bool damos_pa_filter_match(struct damos_filter *filter,
 		matched = filter->sz_range.min <= folio_sz &&
 			  folio_sz <= filter->sz_range.max;
 		break;
+	case DAMOS_FILTER_TYPE_UNMAPPED:
+		matched = !folio_mapped(folio) || !folio_raw_mapping(folio);
+		break;
 	default:
 		break;
 	}
diff --git a/mm/damon/sysfs-schemes.c b/mm/damon/sysfs-schemes.c
index 881d00bb3a34..66a1c46cee84 100644
--- a/mm/damon/sysfs-schemes.c
+++ b/mm/damon/sysfs-schemes.c
@@ -331,6 +331,7 @@ static const char * const damon_sysfs_scheme_filter_type_strs[] = {
 	"memcg",
 	"young",
 	"hugepage_size",
+	"unmapped",
 	"addr",
 	"target",
 };
-- 
2.39.5