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Commit 7808121b authored by Daniel De Graaf's avatar Daniel De Graaf Committed by Jeremy Fitzhardinge
Browse files

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: default avatarDaniel De Graaf <dgdegra@tycho.nsa.gov>
Signed-off-by: default avatarJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
parent 76ce7618

drivers/xen/xenfs/xenbus.c

+3 −0
Original line number Diff line number Diff line
@@ -120,6 +120,7 @@ static ssize_t xenbus_file_read(struct file *filp, 
	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 @@ static ssize_t xenbus_file_read(struct file *filp, 
					struct read_buffer, list);

		}

	}

	if (i == 0)

		goto again;



out:

	mutex_unlock(&u->reply_mutex);