From:   Chuck Lever <chuck.lever@oracle.com>
To:     linux-nfs@vger.kernel.org
Cc:     paulmck@kernel.org
Subject: [PATCH v2] NFSD: Fix RCU-related sparse splat
Date:   Mon, 29 Nov 2021 13:46:07 -0500
Message-Id:  <163821156142.90770.4019362941494014139.stgit@bazille.1015granger.net>
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To address this error:

  CC [M]  fs/nfsd/filecache.o
  CHECK   /home/cel/src/linux/linux/fs/nfsd/filecache.c
/home/cel/src/linux/linux/fs/nfsd/filecache.c:772:9: error: incompatible types in comparison expression (different address spaces):
/home/cel/src/linux/linux/fs/nfsd/filecache.c:772:9:    struct net [noderef] __rcu *
/home/cel/src/linux/linux/fs/nfsd/filecache.c:772:9:    struct net *

The "net" field in struct nfsd_fcache_disposal is not annotated as
requiring an RCU assignment, so replace the macro that includes an
invocation of rcu_check_sparse() with an equivalent that does not.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 fs/nfsd/filecache.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c
index fdf89fcf1a0c..3b172eda0e9a 100644
--- a/fs/nfsd/filecache.c
+++ b/fs/nfsd/filecache.c
@@ -772,7 +772,7 @@ nfsd_alloc_fcache_disposal(struct net *net)
 static void
 nfsd_free_fcache_disposal(struct nfsd_fcache_disposal *l)
 {
-	rcu_assign_pointer(l->net, NULL);
+	WRITE_ONCE(l->net, NULL);
 	cancel_work_sync(&l->work);
 	nfsd_file_dispose_list(&l->freeme);
 	kfree_rcu(l, rcu);