[PATCH] mm/zswap: convert zswap_store_page() and zswap_compress() to take a folio

[Wilson Felipe Pereira <wfelipe@google.com>]

Currently, zswap_store() iterates through a folio and extracts individual
struct page pointers using folio_page() to pass into zswap_store_page()
and zswap_compress().

Pass the folio and the page index directly into these functions instead.
This eliminates the need to materialize struct page pointers inside the
zswap_store() loop and replaces legacy page-based accessors with their
folio equivalents:

- sg_set_page() -> sg_set_folio()
- kmap_local_page() -> kmap_local_folio()
- page_to_nid() -> folio_nid()
- page_swap_entry() -> calculated via folio->swap and index

Signed-off-by: Wilson Felipe Pereira <wfelipe@google.com>
---
 mm/zswap.c | 26 ++++++++++++--------------
 1 file changed, 12 insertions(+), 14 deletions(-)

diff --git a/mm/zswap.c b/mm/zswap.c
index 37f34e406c8e..225308c195c7 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -837,8 +837,8 @@ static int zswap_cpu_comp_prepare(unsigned int cpu, struct hlist_node *node)
 	return ret;
 }
 
-static bool zswap_compress(struct page *page, struct zswap_entry *entry,
-			   struct zswap_pool *pool)
+static bool zswap_compress(struct folio *folio, long index,
+			   struct zswap_entry *entry, struct zswap_pool *pool)
 {
 	struct crypto_acomp_ctx *acomp_ctx;
 	struct scatterlist input, output;
@@ -854,7 +854,7 @@ static bool zswap_compress(struct page *page, struct zswap_entry *entry,
 
 	dst = acomp_ctx->buffer;
 	sg_init_table(&input, 1);
-	sg_set_page(&input, page, PAGE_SIZE, 0);
+	sg_set_folio(&input, folio, PAGE_SIZE, index * PAGE_SIZE);
 
 	sg_init_one(&output, dst, PAGE_SIZE);
 	acomp_request_set_params(acomp_ctx->req, &input, &output, PAGE_SIZE, dlen);
@@ -883,8 +883,7 @@ static bool zswap_compress(struct page *page, struct zswap_entry *entry,
 	 */
 	if (comp_ret || !dlen || dlen >= PAGE_SIZE) {
 		rcu_read_lock();
-		if (!mem_cgroup_zswap_writeback_enabled(
-					folio_memcg(page_folio(page)))) {
+		if (!mem_cgroup_zswap_writeback_enabled(folio_memcg(folio))) {
 			rcu_read_unlock();
 			comp_ret = comp_ret ? comp_ret : -EINVAL;
 			goto unlock;
@@ -892,12 +891,12 @@ static bool zswap_compress(struct page *page, struct zswap_entry *entry,
 		rcu_read_unlock();
 		comp_ret = 0;
 		dlen = PAGE_SIZE;
-		dst = kmap_local_page(page);
+		dst = kmap_local_folio(folio, index * PAGE_SIZE);
 		mapped = true;
 	}
 
 	gfp = GFP_NOWAIT | __GFP_NORETRY | __GFP_HIGHMEM | __GFP_MOVABLE;
-	handle = zs_malloc(pool->zs_pool, dlen, gfp, page_to_nid(page));
+	handle = zs_malloc(pool->zs_pool, dlen, gfp, folio_nid(folio));
 	if (IS_ERR_VALUE(handle)) {
 		alloc_ret = PTR_ERR((void *)handle);
 		goto unlock;
@@ -1405,21 +1404,22 @@ static void shrink_worker(struct work_struct *w)
 * main API
 **********************************/
 
-static bool zswap_store_page(struct page *page,
+static bool zswap_store_page(struct folio *folio, long index,
 			     struct obj_cgroup *objcg,
 			     struct zswap_pool *pool)
 {
-	swp_entry_t page_swpentry = page_swap_entry(page);
+	swp_entry_t page_swpentry = swp_entry(swp_type(folio->swap),
+					      swp_offset(folio->swap) + index);
 	struct zswap_entry *entry, *old;
 
 	/* allocate entry */
-	entry = zswap_entry_cache_alloc(GFP_KERNEL, page_to_nid(page));
+	entry = zswap_entry_cache_alloc(GFP_KERNEL, folio_nid(folio));
 	if (!entry) {
 		zswap_reject_kmemcache_fail++;
 		return false;
 	}
 
-	if (!zswap_compress(page, entry, pool))
+	if (!zswap_compress(folio, index, entry, pool))
 		goto compress_failed;
 
 	old = xa_store(swap_zswap_tree(page_swpentry),
@@ -1528,9 +1528,7 @@ bool zswap_store(struct folio *folio)
 	}
 
 	for (index = 0; index < nr_pages; ++index) {
-		struct page *page = folio_page(folio, index);
-
-		if (!zswap_store_page(page, objcg, pool))
+		if (!zswap_store_page(folio, index, objcg, pool))
 			goto put_pool;
 	}
 
-- 
2.55.0.979.g7e5102b832-goog