xenfs/xenbus: report partial reads/writes correctly

copy_(to|from)_user return the number of uncopied bytes, so a successful
return is 0, and any non-zero result indicates some degree of failure.

Reported-by: "Jun Zhu (Intern)" <Jun.Zhu@citrix.com>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>

diff --git a/drivers/xen/xenfs/xenbus.c b/drivers/xen/xenfs/xenbus.c
index 9d5b519d2e4c3ef5a3077639c3ddf4f6145f2552..d2a905826804c3d81412f60ffa7f19c03a3cba5b 100644 (file)
--- a/drivers/xen/xenfs/xenbus.c
+++ b/drivers/xen/xenfs/xenbus.c
@@ -142,7 +142,7 @@ static ssize_t xenbus_file_read(struct file *filp,
                i += sz - ret;
                rb->cons += sz - ret;
 
-               if (ret != sz) {
+               if (ret != 0) {
                        if (i == 0)
                                i = -EFAULT;
                        goto out;
@@ -453,7 +453,7 @@ static ssize_t xenbus_file_write(struct file *filp,
 
        ret = copy_from_user(u->u.buffer + u->len, ubuf, len);
 
-       if (ret == len) {
+       if (ret != 0) {
                rc = -EFAULT;
                goto out;
        }