From: Hugh Dickins <hughd@google.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: kernel test robot <oliver.sang@intel.com>,
Yang Shi <shy828301@gmail.com>,
Stephen Rothwell <sfr@canb.auug.org.au>,
Roman Gushchin <guro@fb.com>, Kirill Tkhai <ktkhai@virtuozzo.com>,
Vlastimil Babka <vbabka@suse.cz>,
Shakeel Butt <shakeelb@google.com>,
Dave Chinner <david@fromorbit.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Michal Hocko <mhocko@suse.com>,
LKML <linux-kernel@vger.kernel.org>,
Linux Memory Management List <linux-mm@kvack.org>,
lkp@lists.01.org, lkp@intel.com
Subject: [PATCH mmotm] mm: vmscan: fix shrinker_rwsem in free_shrinker_info()
Date: Tue, 30 Mar 2021 16:44:05 -0700 (PDT) [thread overview]
Message-ID: <alpine.LSU.2.11.2103301640240.2584@eggly.anvils> (raw)
Lockdep warns mm/vmscan.c: suspicious rcu_dereference_protected() usage!
when free_shrinker_info() is called from mem_cgroup_css_free(): there it
is called with no locking, whereas alloc_shrinker_info() calls it with
down_write of shrinker_rwsem - which seems appropriate. Rearrange that
so free_shrinker_info() can manage the shrinker_rwsem for itself.
Link: https://lkml.kernel.org/r/20210317140615.GB28839@xsang-OptiPlex-9020
Reported-by: kernel test robot <oliver.sang@intel.com>
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Yang Shi <shy828301@gmail.com>
---
Sorry, I've made no attempt to work out precisely where in the series
the locking went missing, nor tried to fit this in as a fix on top of
mm-vmscan-add-shrinker_info_protected-helper.patch
which Oliver reported (and which you notated in mmotm's "series" file).
This patch just adds the fix to the end of the series, after
mm-vmscan-shrink-deferred-objects-proportional-to-priority.patch
mm/vmscan.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
--- mmotm/mm/vmscan.c 2021-03-28 17:26:54.935553064 -0700
+++ linux/mm/vmscan.c 2021-03-30 15:55:13.374459559 -0700
@@ -249,18 +249,20 @@ void free_shrinker_info(struct mem_cgrou
struct shrinker_info *info;
int nid;
+ down_write(&shrinker_rwsem);
for_each_node(nid) {
pn = memcg->nodeinfo[nid];
info = shrinker_info_protected(memcg, nid);
kvfree(info);
rcu_assign_pointer(pn->shrinker_info, NULL);
}
+ up_write(&shrinker_rwsem);
}
int alloc_shrinker_info(struct mem_cgroup *memcg)
{
struct shrinker_info *info;
- int nid, size, ret = 0;
+ int nid, size;
int map_size, defer_size = 0;
down_write(&shrinker_rwsem);
@@ -270,9 +272,9 @@ int alloc_shrinker_info(struct mem_cgrou
for_each_node(nid) {
info = kvzalloc_node(sizeof(*info) + size, GFP_KERNEL, nid);
if (!info) {
+ up_write(&shrinker_rwsem);
free_shrinker_info(memcg);
- ret = -ENOMEM;
- break;
+ return -ENOMEM;
}
info->nr_deferred = (atomic_long_t *)(info + 1);
info->map = (void *)info->nr_deferred + defer_size;
@@ -280,7 +282,7 @@ int alloc_shrinker_info(struct mem_cgrou
}
up_write(&shrinker_rwsem);
- return ret;
+ return 0;
}
static inline bool need_expand(int nr_max)
next reply other threads:[~2021-03-30 23:45 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-30 23:44 Hugh Dickins [this message]
2021-03-31 13:54 ` [PATCH mmotm] mm: vmscan: fix shrinker_rwsem in free_shrinker_info() Shakeel Butt
2021-03-31 18:06 ` Yang Shi
2021-03-31 21:12 ` Hugh Dickins
2021-03-31 23:14 ` Yang Shi
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