The commit bf9b7df23cb3 ("mm/zswap: global lru and shrinker shared by
all zswap_pools") introduced a new lock to protect zswap_next_shrink,
instead of reusing zswap_pools_lock.
But the problem is that it's initialized only when zswap enabled,
which causes bug if zswap_memcg_offline_cleanup() called without
zswap enabled.
Fix it by using DEFINE_SPINLOCK() to statically initialize them
and define them as multiple static variables to keep in consistent
with the existing global variables in zswap.
Fixes: bf9b7df23cb3 ("mm/zswap: global lru and shrinker shared by all zswap_pools")
Reported-by: kernel test robot <[email protected]>
Closes: https://lore.kernel.org/oe-lkp/[email protected]
Signed-off-by: Chengming Zhou <[email protected]>
---
mm/zswap.c | 77 +++++++++++++++++++++++++++---------------------------
1 file changed, 38 insertions(+), 39 deletions(-)
diff --git a/mm/zswap.c b/mm/zswap.c
index da90933c6d20..9a3237752082 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -180,15 +180,16 @@ struct zswap_pool {
char tfm_name[CRYPTO_MAX_ALG_NAME];
};
-static struct {
- struct list_lru list_lru;
- atomic_t nr_stored;
- struct shrinker *shrinker;
- struct work_struct shrink_work;
- struct mem_cgroup *next_shrink;
- /* The lock protects next_shrink. */
- spinlock_t shrink_lock;
-} zswap;
+/* Global LRU lists shared by all zswap pools. */
+static struct list_lru zswap_list_lru;
+/* counter of pages stored in all zswap pools. */
+static atomic_t zswap_nr_stored = ATOMIC_INIT(0);
+
+/* The lock protects zswap_next_shrink updates. */
+static DEFINE_SPINLOCK(zswap_shrink_lock);
+static struct mem_cgroup *zswap_next_shrink;
+static struct work_struct zswap_shrink_work;
+static struct shrinker *zswap_shrinker;
/*
* struct zswap_entry
@@ -798,10 +799,10 @@ void zswap_folio_swapin(struct folio *folio)
void zswap_memcg_offline_cleanup(struct mem_cgroup *memcg)
{
/* lock out zswap shrinker walking memcg tree */
- spin_lock(&zswap.shrink_lock);
- if (zswap.next_shrink == memcg)
- zswap.next_shrink = mem_cgroup_iter(NULL, zswap.next_shrink, NULL);
- spin_unlock(&zswap.shrink_lock);
+ spin_lock(&zswap_shrink_lock);
+ if (zswap_next_shrink == memcg)
+ zswap_next_shrink = mem_cgroup_iter(NULL, zswap_next_shrink, NULL);
+ spin_unlock(&zswap_shrink_lock);
}
/*********************************
@@ -900,9 +901,9 @@ static void zswap_entry_free(struct zswap_entry *entry)
if (!entry->length)
atomic_dec(&zswap_same_filled_pages);
else {
- zswap_lru_del(&zswap.list_lru, entry);
+ zswap_lru_del(&zswap_list_lru, entry);
zpool_free(zswap_find_zpool(entry), entry->handle);
- atomic_dec(&zswap.nr_stored);
+ atomic_dec(&zswap_nr_stored);
zswap_pool_put(entry->pool);
}
if (entry->objcg) {
@@ -1274,7 +1275,7 @@ static unsigned long zswap_shrinker_scan(struct shrinker *shrinker,
nr_protected =
atomic_long_read(&lruvec->zswap_lruvec_state.nr_zswap_protected);
- lru_size = list_lru_shrink_count(&zswap.list_lru, sc);
+ lru_size = list_lru_shrink_count(&zswap_list_lru, sc);
/*
* Abort if we are shrinking into the protected region.
@@ -1291,7 +1292,7 @@ static unsigned long zswap_shrinker_scan(struct shrinker *shrinker,
return SHRINK_STOP;
}
- shrink_ret = list_lru_shrink_walk(&zswap.list_lru, sc, &shrink_memcg_cb,
+ shrink_ret = list_lru_shrink_walk(&zswap_list_lru, sc, &shrink_memcg_cb,
&encountered_page_in_swapcache);
if (encountered_page_in_swapcache)
@@ -1317,7 +1318,7 @@ static unsigned long zswap_shrinker_count(struct shrinker *shrinker,
#else
/* use pool stats instead of memcg stats */
nr_backing = zswap_pool_total_size >> PAGE_SHIFT;
- nr_stored = atomic_read(&zswap.nr_stored);
+ nr_stored = atomic_read(&zswap_nr_stored);
#endif
if (!nr_stored)
@@ -1325,7 +1326,7 @@ static unsigned long zswap_shrinker_count(struct shrinker *shrinker,
nr_protected =
atomic_long_read(&lruvec->zswap_lruvec_state.nr_zswap_protected);
- nr_freeable = list_lru_shrink_count(&zswap.list_lru, sc);
+ nr_freeable = list_lru_shrink_count(&zswap_list_lru, sc);
/*
* Subtract the lru size by an estimate of the number of pages
* that should be protected.
@@ -1374,7 +1375,7 @@ static int shrink_memcg(struct mem_cgroup *memcg)
for_each_node_state(nid, N_NORMAL_MEMORY) {
unsigned long nr_to_walk = 1;
- shrunk += list_lru_walk_one(&zswap.list_lru, nid, memcg,
+ shrunk += list_lru_walk_one(&zswap_list_lru, nid, memcg,
&shrink_memcg_cb, NULL, &nr_to_walk);
}
return shrunk ? 0 : -EAGAIN;
@@ -1387,9 +1388,9 @@ static void shrink_worker(struct work_struct *w)
/* global reclaim will select cgroup in a round-robin fashion. */
do {
- spin_lock(&zswap.shrink_lock);
- zswap.next_shrink = mem_cgroup_iter(NULL, zswap.next_shrink, NULL);
- memcg = zswap.next_shrink;
+ spin_lock(&zswap_shrink_lock);
+ zswap_next_shrink = mem_cgroup_iter(NULL, zswap_next_shrink, NULL);
+ memcg = zswap_next_shrink;
/*
* We need to retry if we have gone through a full round trip, or if we
@@ -1403,7 +1404,7 @@ static void shrink_worker(struct work_struct *w)
* memcg is not killed when we are reclaiming.
*/
if (!memcg) {
- spin_unlock(&zswap.shrink_lock);
+ spin_unlock(&zswap_shrink_lock);
if (++failures == MAX_RECLAIM_RETRIES)
break;
@@ -1413,15 +1414,15 @@ static void shrink_worker(struct work_struct *w)
if (!mem_cgroup_tryget_online(memcg)) {
/* drop the reference from mem_cgroup_iter() */
mem_cgroup_iter_break(NULL, memcg);
- zswap.next_shrink = NULL;
- spin_unlock(&zswap.shrink_lock);
+ zswap_next_shrink = NULL;
+ spin_unlock(&zswap_shrink_lock);
if (++failures == MAX_RECLAIM_RETRIES)
break;
goto resched;
}
- spin_unlock(&zswap.shrink_lock);
+ spin_unlock(&zswap_shrink_lock);
ret = shrink_memcg(memcg);
/* drop the extra reference */
@@ -1542,7 +1543,7 @@ bool zswap_store(struct folio *folio)
if (objcg) {
memcg = get_mem_cgroup_from_objcg(objcg);
- if (memcg_list_lru_alloc(memcg, &zswap.list_lru, GFP_KERNEL)) {
+ if (memcg_list_lru_alloc(memcg, &zswap_list_lru, GFP_KERNEL)) {
mem_cgroup_put(memcg);
goto put_pool;
}
@@ -1573,8 +1574,8 @@ bool zswap_store(struct folio *folio)
}
if (entry->length) {
INIT_LIST_HEAD(&entry->lru);
- zswap_lru_add(&zswap.list_lru, entry);
- atomic_inc(&zswap.nr_stored);
+ zswap_lru_add(&zswap_list_lru, entry);
+ atomic_inc(&zswap_nr_stored);
}
spin_unlock(&tree->lock);
@@ -1606,7 +1607,7 @@ bool zswap_store(struct folio *folio)
return false;
shrink:
- queue_work(shrink_wq, &zswap.shrink_work);
+ queue_work(shrink_wq, &zswap_shrink_work);
goto reject;
}
@@ -1773,16 +1774,14 @@ static int zswap_setup(void)
if (!shrink_wq)
goto shrink_wq_fail;
- zswap.shrinker = zswap_alloc_shrinker();
- if (!zswap.shrinker)
+ zswap_shrinker = zswap_alloc_shrinker();
+ if (!zswap_shrinker)
goto shrinker_fail;
- if (list_lru_init_memcg(&zswap.list_lru, zswap.shrinker))
+ if (list_lru_init_memcg(&zswap_list_lru, zswap_shrinker))
goto lru_fail;
- shrinker_register(zswap.shrinker);
+ shrinker_register(zswap_shrinker);
- INIT_WORK(&zswap.shrink_work, shrink_worker);
- atomic_set(&zswap.nr_stored, 0);
- spin_lock_init(&zswap.shrink_lock);
+ INIT_WORK(&zswap_shrink_work, shrink_worker);
pool = __zswap_pool_create_fallback();
if (pool) {
@@ -1801,7 +1800,7 @@ static int zswap_setup(void)
return 0;
lru_fail:
- shrinker_free(zswap.shrinker);
+ shrinker_free(zswap_shrinker);
shrinker_fail:
destroy_workqueue(shrink_wq);
shrink_wq_fail:
--
2.40.1
On Tue, Mar 05, 2024 at 07:53:45AM +0000, Chengming Zhou wrote:
> The commit bf9b7df23cb3 ("mm/zswap: global lru and shrinker shared by
> all zswap_pools") introduced a new lock to protect zswap_next_shrink,
> instead of reusing zswap_pools_lock.
>
> But the problem is that it's initialized only when zswap enabled,
> which causes bug if zswap_memcg_offline_cleanup() called without
> zswap enabled.
>
> Fix it by using DEFINE_SPINLOCK() to statically initialize them
> and define them as multiple static variables to keep in consistent
> with the existing global variables in zswap.
>
> Fixes: bf9b7df23cb3 ("mm/zswap: global lru and shrinker shared by all zswap_pools")
> Reported-by: kernel test robot <[email protected]>
> Closes: https://lore.kernel.org/oe-lkp/[email protected]
> Signed-off-by: Chengming Zhou <[email protected]>
Acked-by: Johannes Weiner <[email protected]>