Libguestfs - Nov 2017 - [nbdkit PATCH] nbd: Properly mop up stranded requests

Nothing in the second loop of nbd_reader() was ever setting
quit; the only way the loop could end was via SEGV for
dereferencing NULL or abort() when attempting to write to
an invalid fd.  Finish the implementation to properly mop
up stranded in-flight requests.

The testsuite did not exercise the case of quitting
nbdkit while a transaction was in flight, but was relying
on SIGTERM exiting the entire process before all threads
were reaped; otherwise, I might have spotted this sooner.

Signed-off-by: Eric Blake <eblake@redhat.com>
---
 plugins/nbd/nbd.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/plugins/nbd/nbd.c b/plugins/nbd/nbd.c
index a4a9639..df49a1d 100644
--- a/plugins/nbd/nbd.c
+++ b/plugins/nbd/nbd.c
@@ -384,15 +384,16 @@ nbd_reader (void *handle)
   }

   /* Clean up any stranded in-flight requests */
-  done = false;
   r = ESHUTDOWN;
-  while (!done) {
+  while (1) {
     struct transaction *trans;

     nbd_lock (h);
     trans = h->trans;
-    h->trans = trans->next;
+    h->trans = trans ? trans->next : NULL;
     nbd_unlock (h);
+    if (!trans)
+      break;
     if (write (trans->u.fds[1], &r, sizeof r) != sizeof r) {
       nbdkit_error ("failed to write pipe: %m");
       abort ();
-- 
2.13.6

Thanks Eric, I have pushed this in readiness for a .18 release.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
Fedora Windows cross-compiler. Compile Windows programs, test, and
build Windows installers. Over 100 libraries supported.
http://fedoraproject.org/wiki/MinGW