9P: Fix race in p9_write_work()

See previous commit about p9_read_work() for details.

This fixes a similar race between p9_write_work() and p9_poll_mux()

Signed-off-by: Simon Derr <simon.derr@bull.net>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>

1 files changed, 10 insertions, 9 deletions

diff --git a/net/9p/trans_fd.c b/net/9p/trans_fd.c
index 7088a94b2601..b2c308fffb8a 100644
--- a/net/9p/trans_fd.c
+++ b/net/9p/trans_fd.c
@@ -476,10 +476,9 @@ static void p9_write_work(struct work_struct *work)
         clear_bit(Wpending, &m->wsched);
         err = p9_fd_write(m->client, m->wbuf + m->wpos, m->wsize - m->wpos);
         p9_debug(P9_DEBUG_TRANS, "mux %p sent %d bytes\n", m, err);
-        if (err == -EAGAIN) {
-                clear_bit(Wworksched, &m->wsched);
-                return;
-        }
+        if (err == -EAGAIN)
+                goto end_clear;
+
 
         if (err < 0)
                 goto error;
@@ -492,19 +491,21 @@ static void p9_write_work(struct work_struct *work)
         if (m->wpos == m->wsize)
                 m->wpos = m->wsize = 0;
 
+end_clear:
+        clear_bit(Wworksched, &m->wsched);
+
         if (m->wsize || !list_empty(&m->unsent_req_list)) {
                 if (test_and_clear_bit(Wpending, &m->wsched))
                         n = POLLOUT;
                 else
                         n = p9_fd_poll(m->client, NULL);
 
-                if (n & POLLOUT) {
+                if ((n & POLLOUT) &&
+                   !test_and_set_bit(Wworksched, &m->wsched)) {
                         p9_debug(P9_DEBUG_TRANS, "sched write work %p\n", m);
                         schedule_work(&m->wq);
-                } else
-                        clear_bit(Wworksched, &m->wsched);
-        } else
-                clear_bit(Wworksched, &m->wsched);
+                }
+        }
 
         return;