On Wed, Jan 29, 2025 at 02:49:38AM +0900, Hyeonggon Yoo wrote:
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()")
This commit is in 6.13, not 6.12, so your subject line is a bit confusing :(