Commit 1b10f0b6 authored by Yang Erkun's avatar Yang Erkun Committed by Chuck Lever
Browse files

SUNRPC: 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 c_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 c224edca

net/sunrpc/cache.c

+3 −9
Original line number Diff line number Diff line
@@ -1438,17 +1438,11 @@ static int c_show(struct seq_file *m, void *p) 
		seq_printf(m, "# expiry=%lld refcnt=%d flags=%lx\n",

			   convert_to_wallclock(cp->expiry_time),

			   kref_read(&cp->ref), cp->flags);

	if (!cache_get_rcu(cp))

		return 0;



	if (cache_check(cd, cp, NULL))

		/* cache_check does a cache_put on failure */

	if (cache_check_rcu(cd, cp, NULL))

		seq_puts(m, "# ");

	else {

		if (cache_is_expired(cd, cp))

	else if (cache_is_expired(cd, cp))

		seq_puts(m, "# ");

		cache_put(cp, cd);

	}



	return cd->cache_show(m, cd, cp);

}