[PATCH] xen/9pfs: fix return value check in xen_9pfs_front_probe()

[Wei Yongjun]

From: Wei Yongjun <weiyongj...@huawei.com>

In case of error, the function xenbus_read() returns ERR_PTR() and never
returns NULL. The NULL test in the return value check should be replaced
with IS_ERR().

Fixes: 71ebd71921e4 ("xen/9pfs: connect to the backend")
Signed-off-by: Wei Yongjun <weiyongj...@huawei.com>
---
 net/9p/trans_xen.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/9p/trans_xen.c b/net/9p/trans_xen.c
index 71e8564..83fe487 100644
--- a/net/9p/trans_xen.c
+++ b/net/9p/trans_xen.c
@@ -454,8 +454,8 @@ static int xen_9pfs_front_probe(struct xenbus_device *dev,
                        goto error_xenbus;
        }
        priv->tag = xenbus_read(xbt, dev->nodename, "tag", NULL);
-       if (!priv->tag) {
-               ret = -EINVAL;
+       if (IS_ERR(priv->tag)) {
+               ret = PTR_ERR(priv->tag);
                goto error_xenbus;
        }
        ret = xenbus_transaction_end(xbt, 0);