When zswap_comp.lock was added, zpool_map/unmap_handle() were called both inside and outside of preempt disabled sections, thus zswap_comp.lock locked sections when those preempt disabled sections were removed. With the later addition of zs_map_area.lock in the zsmalloc map/unmap methods, these two locks collide in a zswap_frontswap_load() vs zswap_frontswap_store() inversion/deadlock. Call zpool map/unmap methods in zswap_frontswap_load() under zswap_comp.lock as they are in zswap_frontswap_store() to prevent deadlock. Signed-off-by: Mike Galbraith <efault@xxxxxx> --- mm/zswap.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/mm/zswap.c +++ b/mm/zswap.c @@ -1183,17 +1183,17 @@ static int zswap_frontswap_load(unsigned } /* decompress */ + local_lock(&zswap_comp.lock); dlen = PAGE_SIZE; src = zpool_map_handle(entry->pool->zpool, entry->handle, ZPOOL_MM_RO); if (zpool_evictable(entry->pool->zpool)) src += sizeof(struct zswap_header); dst = kmap_atomic(page); - local_lock(&zswap_comp.lock); tfm = *this_cpu_ptr(entry->pool->tfm); ret = crypto_comp_decompress(tfm, src, entry->length, dst, &dlen); - local_unlock(&zswap_comp.lock); kunmap_atomic(dst); zpool_unmap_handle(entry->pool->zpool, entry->handle); + local_unlock(&zswap_comp.lock); BUG_ON(ret); freeentry:
