[PATCH] net/9p/client.c: put refcount of trans_mod in error case in parse_opts()

[piaojun]

>From my test, the second mount will fail after umounting successfully.
The reason is that we put refcount of trans_mod in the correct case rather
than the error case in parse_opts() at last. That will cause the refcount
decrease to -1, and when we try to get trans_mod again in
try_module_get(), we could only increase refcount to 0 which will cause
failure as follows:
parse_opts
  v9fs_get_trans_by_name
    try_module_get : return NULL to caller which cause error

So we should put refcount of trans_mod in error case.

Fixes: 9421c3e64137ec ("net/9p/client.c: fix potential refcnt problem of trans 
module")

Signed-off-by: Jun Piao <piao...@huawei.com>
---
 net/9p/client.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/9p/client.c b/net/9p/client.c
index 18c5271..5c13431 100644
--- a/net/9p/client.c
+++ b/net/9p/client.c
@@ -225,7 +225,8 @@ static int parse_opts(char *opts, struct p9_client *clnt)
        }

 free_and_return:
-       v9fs_put_trans(clnt->trans_mod);
+       if (ret)
+               v9fs_put_trans(clnt->trans_mod);
        kfree(tmp_options);
        return ret;
 }
--