From: Qi Zheng <zhengqi.arch@bytedance.com>
In the near future, a folio will no longer pin its corresponding memory
cgroup. To ensure safety, it will only be appropriate to hold the rcu read
lock or acquire a reference to the memory cgroup returned by
folio_memcg(), thereby preventing it from being released.
In the current patch, the rcu read lock is employed to safeguard against
the release of the memory cgroup in zswap_compress().
Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
---
mm/zswap.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/mm/zswap.c b/mm/zswap.c
index 5d0f8b13a958d..b468046a90754 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -894,11 +894,14 @@ static bool zswap_compress(struct page *page, struct zswap_entry *entry,
* to the active LRU list in the case.
*/
if (comp_ret || !dlen || dlen >= PAGE_SIZE) {
+ rcu_read_lock();
if (!mem_cgroup_zswap_writeback_enabled(
folio_memcg(page_folio(page)))) {
+ rcu_read_unlock();
comp_ret = comp_ret ? comp_ret : -EINVAL;
goto unlock;
}
+ rcu_read_unlock();
comp_ret = 0;
dlen = PAGE_SIZE;
dst = kmap_local_page(page);
--
2.20.1