linux-kernel - [PATCH] nfsd: destroy percpu stats counters after reply cache shutdown

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Date:   Mon, 23 May 2022 18:52:26 +0000
From:   Julian Schroeder 
        <jumaco@...-dsk-jumaco-1e-78723413.us-east-1.amazon.com>
To:     Chuck Lever <chuck.lever@...cle.com>,
        Amir Goldstein <amir73il@...il.com>,
        <linux-nfs@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC:     <benh@...zon.com>, <alisaidi@...zon.com>, <jumaco@...zon.com>
Subject: [PATCH] nfsd: destroy percpu stats counters after reply cache shutdown

From: Julian Schroeder <jumaco@...zon.com>

Upon nfsd shutdown any pending DRC cache is freed. DRC cache use is
tracked via a percpu counter. In the current code the percpu counter
is destroyed before. If any pending cache is still present,
percpu_counter_add is called with a percpu counter==NULL. This causes
a kernel crash.
The solution is to destroy the percpu counter after the cache is freed.

Fixes: e567b98ce9a4b (“nfsd: protect concurrent access to nfsd stats counters”)
Signed-off-by: Julian Schroeder <jumaco@...zon.com>
---
 fs/nfsd/nfscache.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/nfsd/nfscache.c b/fs/nfsd/nfscache.c
index 0b3f12aa37ff..7da88bdc0d6c 100644
--- a/fs/nfsd/nfscache.c
+++ b/fs/nfsd/nfscache.c
@@ -206,7 +206,6 @@ void nfsd_reply_cache_shutdown(struct nfsd_net *nn)
 	struct svc_cacherep	*rp;
 	unsigned int i;
 
-	nfsd_reply_cache_stats_destroy(nn);
 	unregister_shrinker(&nn->nfsd_reply_cache_shrinker);
 
 	for (i = 0; i < nn->drc_hashsize; i++) {
@@ -217,6 +216,7 @@ void nfsd_reply_cache_shutdown(struct nfsd_net *nn)
 									rp, nn);
 		}
 	}
+	nfsd_reply_cache_stats_destroy(nn);
 
 	kvfree(nn->drc_hashtbl);
 	nn->drc_hashtbl = NULL;
-- 
2.32.0