[RFC PATCH 2/9] mm: zswap: refactor storing to the tree out of zswap_store()

Yosry Ahmed
2024-03-25T23:50:24Z

Refactor the code that attempts storing to the xarray, handling erros,
and freeing stale entries into a helper. This will be reused in a
following patch to free other types of tree elements as well.

Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
---
mm/zswap.c | 42 ++++++++++++++++++++++++++----------------
1 file changed, 26 insertions(+), 16 deletions(-)

diff --git a/mm/zswap.c b/mm/zswap.c
index 1cf3ab4b22e64..ff1975afb7e3d 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -827,6 +827,30 @@ static void zswap_entry_free(struct zswap_entry *entry)
atomic_dec(&zswap_stored_pages);
}

+/*********************************
+* zswap tree functions
+**********************************/
+static int zswap_tree_store(struct xarray *tree, pgoff_t offset, void *new)
+{
+ void *old;
+ int err;
+
+ old = xa_store(tree, offset, new, GFP_KERNEL);
+ err = xa_is_err(old);
+ if (err) {
+ WARN_ONCE(err != -ENOMEM, "unexpected xarray error: %d\n", err);
+ zswap_reject_alloc_fail++;
+ } else if (old) {
+ /*
+ * We may have had an existing entry that became stale when
+ * the folio was redirtied and now the new version is being
+ * swapped out. Get rid of the old.
+ */
+ zswap_entry_free(old);
+ }
+ return err;
+}
+
/*********************************
* compressed storage functions
**********************************/
@@ -1396,10 +1420,10 @@ bool zswap_store(struct folio *folio)
swp_entry_t swp = folio->swap;
pgoff_t offset = swp_offset(swp);
struct xarray *tree = swap_zswap_tree(swp);
- struct zswap_entry *entry, *old;
struct obj_cgroup *objcg = NULL;
struct mem_cgroup *memcg = NULL;
unsigned long max_pages, cur_pages;
+ struct zswap_entry *entry;

VM_WARN_ON_ONCE(!folio_test_locked(folio));
VM_WARN_ON_ONCE(!folio_test_swapcache(folio));
@@ -1485,22 +1509,8 @@ bool zswap_store(struct folio *folio)
entry->swpentry = swp;
entry->objcg = objcg;

- old = xa_store(tree, offset, entry, GFP_KERNEL);
- if (xa_is_err(old)) {
- int err = xa_err(old);
-
- WARN_ONCE(err != -ENOMEM, "unexpected xarray error: %d\n", err);
- zswap_reject_alloc_fail++;
+ if (zswap_tree_store(tree, offset, entry))
goto store_failed;
- }
-
- /*
- * We may have had an existing entry that became stale when
- * the folio was redirtied and now the new version is being
- * swapped out. Get rid of the old.
- */
- if (old)
- zswap_entry_free(old);

if (objcg) {
obj_cgroup_charge_zswap(objcg, entry->length);
--
2.44.0.396.g6e790dbe36-goog