Commit b7c0ccdfbafd ("mm: zswap: support large folios in zswap_store()")
mistakenly skipped charging any zswapped pages when a single call to
zswap_store_page() failed, even if some pages in the folio are
successfully stored in zswap.
Making things worse, these not-charged pages are uncharged in
zswap_entry_free(), making zswap charging inconsistent.
This inconsistency triggers two warnings when following these steps:
# On a machine with 64GiB of RAM and 36GiB of zswap
$ stress-ng --bigheap 2 # wait until the OOM-killer kills stress-ng
$ sudo reboot
Two warnings are:
in mm/memcontrol.c:163, function obj_cgroup_release():
WARN_ON_ONCE(nr_bytes & (PAGE_SIZE - 1));
in mm/page_counter.c:60, function page_counter_cancel():
if (WARN_ONCE(new < 0, "page_counter underflow: %ld nr_pages=%lu\n",
new, nr_pages))
Charge zswapped pages even if some pages of the folio are not zswapped.
After resolving the inconsistency, these warnings disappear.
Fixes: b7c0ccdfbafd ("mm: zswap: support large folios in zswap_store()")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Hyeonggon Yoo <42.hyeyoo@xxxxxxxxx>
---
mm/zswap.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)
diff --git a/mm/zswap.c b/mm/zswap.c
index 6504174fbc6a..92752cd05c75 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -1568,20 +1568,20 @@ bool zswap_store(struct folio *folio)
bytes = zswap_store_page(page, objcg, pool);
if (bytes < 0)
- goto put_pool;
+ goto charge_zswap;
compressed_bytes += bytes;
}
- if (objcg) {
- obj_cgroup_charge_zswap(objcg, compressed_bytes);
- count_objcg_events(objcg, ZSWPOUT, nr_pages);
- }
-
atomic_long_add(nr_pages, &zswap_stored_pages);
count_vm_events(ZSWPOUT, nr_pages);
ret = true;
+charge_zswap:
+ if (objcg) {
+ obj_cgroup_charge_zswap(objcg, compressed_bytes);
+ count_objcg_events(objcg, ZSWPOUT, nr_pages);
+ }
put_pool:
zswap_pool_put(pool);
put_objcg:
--
2.47.1
