When a zswap store fails due to the limit, it acquires a pool reference and queues the shrinker. When the shrinker runs, it drops the reference. However, there can be multiple store attempts before the shrinker wakes up and runs once. This results in reference leaks and eventual saturation warnings for the pool refcount.
Fix this by dropping the reference again when the shrinker is already queued. This ensures one reference per shrinker run.
Reported-by: Chris Mason clm@fb.com Fixes: 45190f01dd40 ("mm/zswap.c: add allocation hysteresis if pool limit is hit") Cc: stable@vger.kernel.org [5.6+] Cc: Vitaly Wool vitaly.wool@konsulko.com Cc: Domenico Cerasuolo cerasuolodomenico@gmail.com Cc: Nhat Pham nphamcs@gmail.com Signed-off-by: Johannes Weiner hannes@cmpxchg.org --- mm/zswap.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/mm/zswap.c b/mm/zswap.c index 083c693602b8..37d2b1cb2ecb 100644 --- a/mm/zswap.c +++ b/mm/zswap.c @@ -1383,8 +1383,8 @@ bool zswap_store(struct folio *folio)
shrink: pool = zswap_pool_last_get(); - if (pool) - queue_work(shrink_wq, &pool->shrink_work); + if (pool && !queue_work(shrink_wq, &pool->shrink_work)) + zswap_pool_put(pool); goto reject; }