mm/damon: avoid applying DAMOS action to same entity multiple times

'paddr' DAMON operations set can apply a DAMOS scheme's action to a large
folio multiple times in single DAMOS-regions-walk if the folio is laid on
multiple DAMON regions.  Add a field for DAMOS scheme object that can be
used by the underlying ops to know what was the last entity that the
scheme's action has applied.  The core layer unsets the field when each
DAMOS-regions-walk is done for the given scheme.  And update 'paddr' ops
to use the infrastructure to avoid the problem.

Link: https://lkml.kernel.org/r/20250207212033.45269-3-sj@kernel.org
Fixes: 57223ac29584 ("mm/damon/paddr: support the pageout scheme")
Signed-off-by: SeongJae Park <sj@kernel.org>
Reported-by: Usama Arif <usamaarif642@gmail.com>
Closes: https://lore.kernel.org/20250203225604.44742-3-usamaarif642@gmail.com
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

2 files changed, 28 insertions, 12 deletions

diff --git a/mm/damon/core.c b/mm/damon/core.c
index 384935ef4e65..dc8f94fe7c3b 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -1856,6 +1856,7 @@ static void kdamond_apply_schemes(struct damon_ctx *c)
 		s->next_apply_sis = c->passed_sample_intervals +
 			(s->apply_interval_us ? s->apply_interval_us :
 			 c->attrs.aggr_interval) / sample_interval;
+		s->last_applied = NULL;
 	}
 }
 
diff --git a/mm/damon/paddr.c b/mm/damon/paddr.c
index 2ac19ebc7076..eb10a723b0a7 100644
--- a/mm/damon/paddr.c
+++ b/mm/damon/paddr.c
@@ -254,6 +254,17 @@ static bool damos_pa_filter_out(struct damos *scheme, struct folio *folio)
 	return false;
 }
 
+static bool damon_pa_invalid_damos_folio(struct folio *folio, struct damos *s)
+{
+	if (!folio)
+		return true;
+	if (folio == s->last_applied) {
+		folio_put(folio);
+		return true;
+	}
+	return false;
+}
+
 static unsigned long damon_pa_pageout(struct damon_region *r, struct damos *s,
 		unsigned long *sz_filter_passed)
 {
@@ -261,6 +272,7 @@ static unsigned long damon_pa_pageout(struct damon_region *r, struct damos *s,
 	LIST_HEAD(folio_list);
 	bool install_young_filter = true;
 	struct damos_filter *filter;
+	struct folio *folio;
 
 	/* check access in page level again by default */
 	damos_for_each_filter(filter, s) {
@@ -279,9 +291,8 @@ static unsigned long damon_pa_pageout(struct damon_region *r, struct damos *s,
 
 	addr = r->ar.start;
 	while (addr < r->ar.end) {
-		struct folio *folio = damon_get_folio(PHYS_PFN(addr));
-
-		if (!folio) {
+		folio = damon_get_folio(PHYS_PFN(addr));
+		if (damon_pa_invalid_damos_folio(folio, s)) {
 			addr += PAGE_SIZE;
 			continue;
 		}
@@ -307,6 +318,7 @@ put_folio:
 		damos_destroy_filter(filter);
 	applied = reclaim_pages(&folio_list);
 	cond_resched();
+	s->last_applied = folio;
 	return applied * PAGE_SIZE;
 }
 
@@ -315,12 +327,12 @@ static inline unsigned long damon_pa_mark_accessed_or_deactivate(
 		unsigned long *sz_filter_passed)
 {
 	unsigned long addr, applied = 0;
+	struct folio *folio;
 
 	addr = r->ar.start;
 	while (addr < r->ar.end) {
-		struct folio *folio = damon_get_folio(PHYS_PFN(addr));
-
-		if (!folio) {
+		folio = damon_get_folio(PHYS_PFN(addr));
+		if (damon_pa_invalid_damos_folio(folio, s)) {
 			addr += PAGE_SIZE;
 			continue;
 		}
@@ -339,6 +351,7 @@ put_folio:
 		addr += folio_size(folio);
 		folio_put(folio);
 	}
+	s->last_applied = folio;
 	return applied * PAGE_SIZE;
 }
 
@@ -482,12 +495,12 @@ static unsigned long damon_pa_migrate(struct damon_region *r, struct damos *s,
 {
 	unsigned long addr, applied;
 	LIST_HEAD(folio_list);
+	struct folio *folio;
 
 	addr = r->ar.start;
 	while (addr < r->ar.end) {
-		struct folio *folio = damon_get_folio(PHYS_PFN(addr));
-
-		if (!folio) {
+		folio = damon_get_folio(PHYS_PFN(addr));
+		if (damon_pa_invalid_damos_folio(folio, s)) {
 			addr += PAGE_SIZE;
 			continue;
 		}
@@ -506,6 +519,7 @@ put_folio:
 	}
 	applied = damon_pa_migrate_pages(&folio_list, s->target_nid);
 	cond_resched();
+	s->last_applied = folio;
 	return applied * PAGE_SIZE;
 }
 
@@ -523,15 +537,15 @@ static unsigned long damon_pa_stat(struct damon_region *r, struct damos *s,
 {
 	unsigned long addr;
 	LIST_HEAD(folio_list);
+	struct folio *folio;
 
 	if (!damon_pa_scheme_has_filter(s))
 		return 0;
 
 	addr = r->ar.start;
 	while (addr < r->ar.end) {
-		struct folio *folio = damon_get_folio(PHYS_PFN(addr));
-
-		if (!folio) {
+		folio = damon_get_folio(PHYS_PFN(addr));
+		if (damon_pa_invalid_damos_folio(folio, s)) {
 			addr += PAGE_SIZE;
 			continue;
 		}
@@ -541,6 +555,7 @@ static unsigned long damon_pa_stat(struct damon_region *r, struct damos *s,
 		addr += folio_size(folio);
 		folio_put(folio);
 	}
+	s->last_applied = folio;
 	return 0;
 }