xenbus: avoid zero returns from read()
It is possible to get a zero return from read() in instances where the
queue is not empty but has no elements with data to deliver to the user.
Since a zero return from read is an error indicator, resume waiting or
return -EAGAIN (for a nonblocking fd) in this case.
Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
diff --git a/drivers/xen/xenfs/xenbus.c b/drivers/xen/xenfs/xenbus.c
index c4c7db8..55791dd 100644
--- a/drivers/xen/xenfs/xenbus.c
+++ b/drivers/xen/xenfs/xenbus.c
@@ -120,6 +120,7 @@
int ret;
mutex_lock(&u->reply_mutex);
+again:
while (list_empty(&u->read_buffers)) {
mutex_unlock(&u->reply_mutex);
if (filp->f_flags & O_NONBLOCK)
@@ -158,6 +159,8 @@
struct read_buffer, list);
}
}
+ if (i == 0)
+ goto again;
out:
mutex_unlock(&u->reply_mutex);
