Commit c224edca authored by Yang Erkun's avatar Yang Erkun Committed by Chuck Lever
Browse files

nfsd: no need get cache ref when protected by rcu 



rcu_read_lock/rcu_read_unlock has already provide protection for the
pointer we will reference when we call e_show. Therefore, there is no
need to obtain a cache reference to help protect cache_head.
Additionally, the .put such as expkey_put/svc_export_put will invoke
dput, which can sleep and break rcu. Stop get cache reference to fix
them all.

Fixes: ae74136b ("SUNRPC: Allow cache lookups to use RCU protection rather than the r/w spinlock")
Suggested-by: default avatarNeilBrown <neilb@suse.de>
Signed-off-by: default avatarYang Erkun <yangerkun@huawei.com>
Reviewed-by: default avatarJeff Layton <jlayton@kernel.org>
Signed-off-by: default avatarChuck Lever <chuck.lever@oracle.com>
parent 2f55dbe4

fs/nfsd/export.c

+1 −5
Original line number Diff line number Diff line
@@ -1425,13 +1425,9 @@ static int e_show(struct seq_file *m, void *p) 
		return 0;

	}



	if (!cache_get_rcu(&exp->h))

	if (cache_check_rcu(cd, &exp->h, NULL))

		return 0;



	if (cache_check(cd, &exp->h, NULL))

		return 0;



	exp_put(exp);

	return svc_export_show(m, cd, cp);

}