On Tue, Jan 28, 2025 at 5:50 PM Hyeonggon Yoo 42.hyeyoo@gmail.com 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()") Cc: stable@vger.kernel.org Signed-off-by: Hyeonggon Yoo 42.hyeyoo@gmail.com
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);
Wait, it also does not account for these events/counters. Will send v2. Sorry for the noise.
If I missed anything else, please let me know.
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