From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

Date: Mon, 27 Jan 2020 19:01:04 +0000

Subject: [PATCH] virtiofsd: Keep track of replies

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Keep track of whether we sent a reply to a request; this is a bit

paranoid but it means:

  a) We should always recycle an element even if there was an error

     in the request

  b) Never try and send two replies on one queue element

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 2f65e69a7f22da8d20c747f34f339ebb40a0634f)

---

 tools/virtiofsd/fuse_virtio.c | 23 ++++++++++++++++++++---

 1 file changed, 20 insertions(+), 3 deletions(-)

diff --git a/tools/virtiofsd/fuse_virtio.c b/tools/virtiofsd/fuse_virtio.c

index 05d0e29f12..f1adeb6345 100644

--- a/tools/virtiofsd/fuse_virtio.c

+++ b/tools/virtiofsd/fuse_virtio.c

@@ -44,6 +44,7 @@ struct fv_QueueInfo {

     /* The element for the command currently being processed */

     VuVirtqElement *qe;

+    bool reply_sent;

 };

 /*

@@ -178,6 +179,7 @@ int virtio_send_msg(struct fuse_session *se, struct fuse_chan *ch,

 {

     VuVirtqElement *elem;

     VuVirtq *q;

+    int ret = 0;

     assert(count >= 1);

     assert(iov[0].iov_len >= sizeof(struct fuse_out_header));

@@ -191,6 +193,7 @@ int virtio_send_msg(struct fuse_session *se, struct fuse_chan *ch,

     assert(out->unique);

     /* For virtio we always have ch */

     assert(ch);

+    assert(!ch->qi->reply_sent);

     elem = ch->qi->qe;

     q = &ch->qi->virtio_dev->dev.vq[ch->qi->qidx];

@@ -208,19 +211,23 @@ int virtio_send_msg(struct fuse_session *se, struct fuse_chan *ch,

     if (in_len < sizeof(struct fuse_out_header)) {

         fuse_log(FUSE_LOG_ERR, "%s: elem %d too short for out_header\n",

                  __func__, elem->index);

-        return -E2BIG;

+        ret = -E2BIG;

+        goto err;

     }

     if (in_len < tosend_len) {

         fuse_log(FUSE_LOG_ERR, "%s: elem %d too small for data len %zd\n",

                  __func__, elem->index, tosend_len);

-        return -E2BIG;

+        ret = -E2BIG;

+        goto err;

     }

     copy_iov(iov, count, in_sg, in_num, tosend_len);

     vu_queue_push(&se->virtio_dev->dev, q, elem, tosend_len);

     vu_queue_notify(&se->virtio_dev->dev, q);

+    ch->qi->reply_sent = true;

-    return 0;

+err:

+    return ret;

 }

 /* Thread function for individual queues, created when a queue is 'started' */

@@ -296,6 +303,9 @@ static void *fv_queue_thread(void *opaque)

                 break;

             }

+            qi->qe = elem;

+            qi->reply_sent = false;

+

             if (!fbuf.mem) {

                 fbuf.mem = malloc(se->bufsize);

                 assert(fbuf.mem);

@@ -331,6 +341,13 @@ static void *fv_queue_thread(void *opaque)

             /* TODO: Add checks for fuse_session_exited */

             fuse_session_process_buf_int(se, &fbuf, &ch);

+            if (!qi->reply_sent) {

+                fuse_log(FUSE_LOG_DEBUG, "%s: elem %d no reply sent\n",

+                         __func__, elem->index);

+                /* I think we've still got to recycle the element */

+                vu_queue_push(dev, q, elem, 0);

+                vu_queue_notify(dev, q);

+            }

             qi->qe = NULL;

             free(elem);

             elem = NULL;