[PATCH v2] mm/damon/paddr: initialize 'folio' variables to NULL for safety and clarity

[Aaron Yang <yangqixiao@inspur.com>]

In damon_pa_mark_accessed_or_deactivate(), damon_pa_pageout(),
damon_pa_migrate(), and damon_pa_stat(), the local variable 'folio' is
declared but not initialized.

Initialize 'folio' to NULL to:
- Follow kernel convention: uninitialized pointers should be
  explicitly NULL
- Improve code readability and maintainability
- Provide safe fallback (NULL assignment to s->last_applied is harmless
  and callers check for NULL before dereference)

Signed-off-by: Aaron Yang <yangqixiao@inspur.com>
---
 mm/damon/paddr.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/mm/damon/paddr.c b/mm/damon/paddr.c
index 07a8aead439e..7d887a3c0866 100644
--- a/mm/damon/paddr.c
+++ b/mm/damon/paddr.c
@@ -156,7 +156,7 @@ static unsigned long damon_pa_pageout(struct damon_region *r,
 	LIST_HEAD(folio_list);
 	bool install_young_filter = true;
 	struct damos_filter *filter;
-	struct folio *folio;
+	struct folio *folio = NULL;
 
 	/* check access in page level again by default */
 	damos_for_each_ops_filter(filter, s) {
@@ -212,7 +212,7 @@ static inline unsigned long damon_pa_mark_accessed_or_deactivate(
 		unsigned long *sz_filter_passed)
 {
 	phys_addr_t addr, applied = 0;
-	struct folio *folio;
+	struct folio *folio = NULL;
 
 	addr = damon_pa_phys_addr(r->ar.start, addr_unit);
 	while (addr < damon_pa_phys_addr(r->ar.end, addr_unit)) {
@@ -262,7 +262,7 @@ static unsigned long damon_pa_migrate(struct damon_region *r,
 {
 	phys_addr_t addr, applied;
 	LIST_HEAD(folio_list);
-	struct folio *folio;
+	struct folio *folio = NULL;
 
 	addr = damon_pa_phys_addr(r->ar.start, addr_unit);
 	while (addr < damon_pa_phys_addr(r->ar.end, addr_unit)) {
@@ -295,7 +295,7 @@ static unsigned long damon_pa_stat(struct damon_region *r,
 		unsigned long *sz_filter_passed)
 {
 	phys_addr_t addr;
-	struct folio *folio;
+	struct folio *folio = NULL;
 
 	if (!damos_ops_has_filter(s))
 		return 0;
-- 
2.47.3