The patch titled
Subject: mm/zswap: fix zswap_pools_lock usages after changing to percpu_ref
has been added to the -mm mm-unstable branch. Its filename is
mm-zswap-change-zswap_pool-kref-to-percpu_ref-fix.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-zswap-change-zswap_pool-kref-to-percpu_ref-fix.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Chengming Zhou <chengming.zhou@xxxxxxxxx>
Subject: mm/zswap: fix zswap_pools_lock usages after changing to percpu_ref
Date: Wed, 28 Feb 2024 15:49:54 +0000
Now the release of zswap pool is controlled by percpu_ref, its release
callback (__zswap_pool_empty()) will be called when percpu_ref hit 0. But
this release callback may potentially be called from RCU callback context
by percpu_ref_kill(), which maybe from the softirq context.
So we need to use spin_lock/unlock_bh() to avoid potential deadlock.
This problem is introduced by the commit f3da427e82c4 ("mm/zswap: change
zswap_pool kref to percpu_ref"), which is in mm-unstable branch now. It
can be reproduced by testing kernel build in tmpfs with zswap and
CONFIG_LOCKDEP enabled, meanwhile changing the zswap compressor setting
dynamically.
Link: https://lkml.kernel.org/r/20240228154954.3028626-1-chengming.zhou@xxxxxxxxx
Signed-off-by: Chengming Zhou <chengming.zhou@xxxxxxxxx>
Cc: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Nhat Pham <nphamcs@xxxxxxxxx>
Cc: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/zswap.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)
--- a/mm/zswap.c~mm-zswap-change-zswap_pool-kref-to-percpu_ref-fix
+++ a/mm/zswap.c
@@ -459,7 +459,7 @@ static void __zswap_pool_empty(struct pe
pool = container_of(ref, typeof(*pool), ref);
- spin_lock(&zswap_pools_lock);
+ spin_lock_bh(&zswap_pools_lock);
WARN_ON(pool == zswap_pool_current());
@@ -468,7 +468,7 @@ static void __zswap_pool_empty(struct pe
INIT_WORK(&pool->release_work, __zswap_pool_release);
schedule_work(&pool->release_work);
- spin_unlock(&zswap_pools_lock);
+ spin_unlock_bh(&zswap_pools_lock);
}
static int __must_check zswap_pool_get(struct zswap_pool *pool)
@@ -598,7 +598,7 @@ static int __zswap_param_set(const char
return -EINVAL;
}
- spin_lock(&zswap_pools_lock);
+ spin_lock_bh(&zswap_pools_lock);
pool = zswap_pool_find_get(type, compressor);
if (pool) {
@@ -607,7 +607,7 @@ static int __zswap_param_set(const char
list_del_rcu(&pool->list);
}
- spin_unlock(&zswap_pools_lock);
+ spin_unlock_bh(&zswap_pools_lock);
if (!pool)
pool = zswap_pool_create(type, compressor);
@@ -628,7 +628,7 @@ static int __zswap_param_set(const char
else
ret = -EINVAL;
- spin_lock(&zswap_pools_lock);
+ spin_lock_bh(&zswap_pools_lock);
if (!ret) {
put_pool = zswap_pool_current();
@@ -643,7 +643,7 @@ static int __zswap_param_set(const char
put_pool = pool;
}
- spin_unlock(&zswap_pools_lock);
+ spin_unlock_bh(&zswap_pools_lock);
if (!zswap_has_pool && !pool) {
/* if initial pool creation failed, and this pool creation also
_
Patches currently in -mm which might be from chengming.zhou@xxxxxxxxx are
mm-zswap-change-zswap_pool-kref-to-percpu_ref-fix.patch
