From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Date: Mon, 27 Jan 2020 19:01:01 +0000
Subject: [PATCH] virtiofsd: Poll kick_fd for queue
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In the queue thread poll the kick_fd we're passed.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
(cherry picked from commit 5dcd1f56141378226d33dc3df68ec57913e0aa04)
---
 tools/virtiofsd/fuse_virtio.c | 40 ++++++++++++++++++++++++++++++++++-
 1 file changed, 39 insertions(+), 1 deletion(-)

diff --git a/tools/virtiofsd/fuse_virtio.c b/tools/virtiofsd/fuse_virtio.c
index 2a94bb3cca..05e7258712 100644
--- a/tools/virtiofsd/fuse_virtio.c
+++ b/tools/virtiofsd/fuse_virtio.c
@@ -24,6 +24,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <sys/eventfd.h>
 #include <sys/socket.h>
 #include <sys/types.h>
 #include <sys/un.h>
@@ -100,13 +101,50 @@ static void fv_panic(VuDev *dev, const char *err)
     exit(EXIT_FAILURE);
 }
 
+/* Thread function for individual queues, created when a queue is 'started' */
 static void *fv_queue_thread(void *opaque)
 {
     struct fv_QueueInfo *qi = opaque;
     fuse_log(FUSE_LOG_INFO, "%s: Start for queue %d kick_fd %d\n", __func__,
              qi->qidx, qi->kick_fd);
     while (1) {
-        /* TODO */
+        struct pollfd pf[1];
+        pf[0].fd = qi->kick_fd;
+        pf[0].events = POLLIN;
+        pf[0].revents = 0;
+
+        fuse_log(FUSE_LOG_DEBUG, "%s: Waiting for Queue %d event\n", __func__,
+                 qi->qidx);
+        int poll_res = ppoll(pf, 1, NULL, NULL);
+
+        if (poll_res == -1) {
+            if (errno == EINTR) {
+                fuse_log(FUSE_LOG_INFO, "%s: ppoll interrupted, going around\n",
+                         __func__);
+                continue;
+            }
+            fuse_log(FUSE_LOG_ERR, "fv_queue_thread ppoll: %m\n");
+            break;
+        }
+        assert(poll_res == 1);
+        if (pf[0].revents & (POLLERR | POLLHUP | POLLNVAL)) {
+            fuse_log(FUSE_LOG_ERR, "%s: Unexpected poll revents %x Queue %d\n",
+                     __func__, pf[0].revents, qi->qidx);
+            break;
+        }
+        assert(pf[0].revents & POLLIN);
+        fuse_log(FUSE_LOG_DEBUG, "%s: Got queue event on Queue %d\n", __func__,
+                 qi->qidx);
+
+        eventfd_t evalue;
+        if (eventfd_read(qi->kick_fd, &evalue)) {
+            fuse_log(FUSE_LOG_ERR, "Eventfd_read for queue: %m\n");
+            break;
+        }
+        if (qi->virtio_dev->se->debug) {
+            fprintf(stderr, "%s: Queue %d gave evalue: %zx\n", __func__,
+                    qi->qidx, (size_t)evalue);
+        }
     }
 
     return NULL;