[RFC PATCH v1 1/4] mm: zswap: zswap_is_folio_same_filled() takes an index in the folio.

[Kanchana P Sridhar]

This change is being made so that zswap_store can process mTHP folios.

Modified zswap_is_folio_same_filled() to work for any-order folios,
by accepting an additional "index" parameter to arrive at the
page within the folio to run the same-filled page check.

Signed-off-by: Kanchana P Sridhar <kanchana.p.sridhar@xxxxxxxxx>
---
 mm/zswap.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/mm/zswap.c b/mm/zswap.c
index a50e2986cd2f..a6b0a7c636db 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -1373,14 +1373,14 @@ static void shrink_worker(struct work_struct *w)
 /*********************************
 * same-filled functions
 **********************************/
-static bool zswap_is_folio_same_filled(struct folio *folio, unsigned long *value)
+static bool zswap_is_folio_same_filled(struct folio *folio, long index, unsigned long *value)
 {
 	unsigned long *page;
 	unsigned long val;
 	unsigned int pos, last_pos = PAGE_SIZE / sizeof(*page) - 1;
 	bool ret = false;
 
-	page = kmap_local_folio(folio, 0);
+	page = kmap_local_folio(folio, index * PAGE_SIZE);
 	val = page[0];
 
 	if (val != page[last_pos])
@@ -1450,7 +1450,7 @@ bool zswap_store(struct folio *folio)
 		goto reject;
 	}
 
-	if (zswap_is_folio_same_filled(folio, &value)) {
+	if (zswap_is_folio_same_filled(folio, 0, &value)) {
 		entry->length = 0;
 		entry->value = value;
 		atomic_inc(&zswap_same_filled_pages);
-- 
2.27.0