[RFC PATCH 05/14] zswap: unify zswap tree for virtualized swap

[Nhat Pham <nphamcs@gmail.com>]

Similar to swap cache, the zswap tree code, specifically the range
partition logic, can no longer easily be reused for the new virtual swap
space design. Use a simple unified zswap tree in the new implementation
for now. As in the case of swap cache, range partitioning is planned as
a follow up work.

Signed-off-by: Nhat Pham <nphamcs@gmail.com>
---
 mm/zswap.c | 38 ++++++++++++++++++++++++++++++++------
 1 file changed, 32 insertions(+), 6 deletions(-)

diff --git a/mm/zswap.c b/mm/zswap.c
index 23365e76a3ce..c1327569ce80 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -203,8 +203,6 @@ struct zswap_entry {
 	struct list_head lru;
 };
 
-static struct xarray *zswap_trees[MAX_SWAPFILES];
-static unsigned int nr_zswap_trees[MAX_SWAPFILES];
 
 /* RCU-protected iteration */
 static LIST_HEAD(zswap_pools);
@@ -231,12 +229,28 @@ static bool zswap_has_pool;
 * helpers and fwd declarations
 **********************************/
 
+#ifdef CONFIG_VIRTUAL_SWAP
+static DEFINE_XARRAY(zswap_tree);
+
+static inline struct xarray *swap_zswap_tree(swp_entry_t swp)
+{
+	return &zswap_tree;
+}
+
+#define zswap_tree_index(entry)	entry.val
+#else
+static struct xarray *zswap_trees[MAX_SWAPFILES];
+static unsigned int nr_zswap_trees[MAX_SWAPFILES];
+
 static inline struct xarray *swap_zswap_tree(swp_entry_t swp)
 {
 	return &zswap_trees[swp_type(swp)][swp_offset(swp)
 		>> SWAP_ADDRESS_SPACE_SHIFT];
 }
 
+#define zswap_tree_index(entry)	swp_offset(entry)
+#endif
+
 #define zswap_pool_debug(msg, p)				\
 	pr_debug("%s pool %s/%s\n", msg, (p)->tfm_name,		\
 		 zpool_get_type((p)->zpool))
@@ -1047,7 +1061,7 @@ static int zswap_writeback_entry(struct zswap_entry *entry,
 				 swp_entry_t swpentry)
 {
 	struct xarray *tree;
-	pgoff_t offset = swp_offset(swpentry);
+	pgoff_t offset = zswap_tree_index(swpentry);
 	struct folio *folio;
 	struct mempolicy *mpol;
 	bool folio_was_allocated;
@@ -1463,7 +1477,7 @@ static bool zswap_store_page(struct page *page,
 		goto compress_failed;
 
 	old = xa_store(swap_zswap_tree(page_swpentry),
-		       swp_offset(page_swpentry),
+		       zswap_tree_index(page_swpentry),
 		       entry, GFP_KERNEL);
 	if (xa_is_err(old)) {
 		int err = xa_err(old);
@@ -1612,7 +1626,7 @@ bool zswap_store(struct folio *folio)
 bool zswap_load(struct folio *folio)
 {
 	swp_entry_t swp = folio->swap;
-	pgoff_t offset = swp_offset(swp);
+	pgoff_t offset = zswap_tree_index(swp);
 	bool swapcache = folio_test_swapcache(folio);
 	struct xarray *tree = swap_zswap_tree(swp);
 	struct zswap_entry *entry;
@@ -1670,7 +1684,7 @@ bool zswap_load(struct folio *folio)
 
 void zswap_invalidate(swp_entry_t swp)
 {
-	pgoff_t offset = swp_offset(swp);
+	pgoff_t offset = zswap_tree_index(swp);
 	struct xarray *tree = swap_zswap_tree(swp);
 	struct zswap_entry *entry;
 
@@ -1682,6 +1696,16 @@ void zswap_invalidate(swp_entry_t swp)
 		zswap_entry_free(entry);
 }
 
+#ifdef CONFIG_VIRTUAL_SWAP
+int zswap_swapon(int type, unsigned long nr_pages)
+{
+	return 0;
+}
+
+void zswap_swapoff(int type)
+{
+}
+#else
 int zswap_swapon(int type, unsigned long nr_pages)
 {
 	struct xarray *trees, *tree;
@@ -1718,6 +1742,8 @@ void zswap_swapoff(int type)
 	nr_zswap_trees[type] = 0;
 	zswap_trees[type] = NULL;
 }
+#endif /* CONFIG_VIRTUAL_SWAP */
+
 
 /*********************************
 * debugfs functions
-- 
2.47.1