implement O_NONBLOCK for /proc/xen/xenbus

This patch implements O_NONBLOCK for /proc/xen/xenbus.  It is a simple
matter of returning -EAGAIN instead of waiting on a queue.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.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 a9592d9..9d5b519 100644 (file)
--- a/drivers/xen/xenfs/xenbus.c
+++ b/drivers/xen/xenfs/xenbus.c
@@ -122,6 +122,9 @@ static ssize_t xenbus_file_read(struct file *filp,
        mutex_lock(&u->reply_mutex);
        while (list_empty(&u->read_buffers)) {
                mutex_unlock(&u->reply_mutex);
        mutex_lock(&u->reply_mutex);
        while (list_empty(&u->read_buffers)) {
                mutex_unlock(&u->reply_mutex);

+               if (filp->f_flags & O_NONBLOCK)
+                       return -EAGAIN;
+

                ret = wait_event_interruptible(u->read_waitq,
                                               !list_empty(&u->read_buffers));
                if (ret)
                ret = wait_event_interruptible(u->read_waitq,
                                               !list_empty(&u->read_buffers));
                if (ret)