virtiofs: Count pending forgets as in_flight forgets

If virtqueue is full, we put forget requests on a list and these forgets
are dispatched later using a worker. As of now we don't count these forgets
in fsvq->in_flight variable. This means when queue is being drained, we
have to have special logic to first drain these pending requests and then
wait for fsvq->in_flight to go to zero.

By counting pending forgets in fsvq->in_flight, we can get rid of special
logic and just wait for in_flight to go to zero. Worker thread will kick
and drain all the forgets anyway, leading in_flight to zero.

I also need similar logic for normal request queue in next patch where I am
about to defer request submission in the worker context if queue is full.

This simplifies the code a bit.

Also add two helper functions to inc/dec in_flight. Decrement in_flight
helper will later used to call completion when in_flight reaches zero.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

diff --git a/fs/fuse/virtio_fs.c b/fs/fuse/virtio_fs.c
index 6d153e7..3ea613d 100644 (file)
--- a/fs/fuse/virtio_fs.c
+++ b/fs/fuse/virtio_fs.c
@@ -67,6 +67,19 @@ static inline struct fuse_pqueue *vq_to_fpq(struct virtqueue *vq)
        return &vq_to_fsvq(vq)->fud->pq;
 }
 
+/* Should be called with fsvq->lock held. */
+static inline void inc_in_flight_req(struct virtio_fs_vq *fsvq)
+{
+       fsvq->in_flight++;
+}
+
+/* Should be called with fsvq->lock held. */
+static inline void dec_in_flight_req(struct virtio_fs_vq *fsvq)
+{
+       WARN_ON(fsvq->in_flight <= 0);
+       fsvq->in_flight--;
+}
+
 static void release_virtio_fs_obj(struct kref *ref)
 {
        struct virtio_fs *vfs = container_of(ref, struct virtio_fs, refcount);
@@ -110,22 +123,6 @@ static void virtio_fs_drain_queue(struct virtio_fs_vq *fsvq)
        flush_delayed_work(&fsvq->dispatch_work);
 }
 
-static inline void drain_hiprio_queued_reqs(struct virtio_fs_vq *fsvq)
-{
-       struct virtio_fs_forget *forget;
-
-       spin_lock(&fsvq->lock);
-       while (1) {
-               forget = list_first_entry_or_null(&fsvq->queued_reqs,
-                                               struct virtio_fs_forget, list);
-               if (!forget)
-                       break;
-               list_del(&forget->list);
-               kfree(forget);
-       }
-       spin_unlock(&fsvq->lock);
-}
-
 static void virtio_fs_drain_all_queues(struct virtio_fs *fs)
 {
        struct virtio_fs_vq *fsvq;
@@ -133,9 +130,6 @@ static void virtio_fs_drain_all_queues(struct virtio_fs *fs)
 
        for (i = 0; i < fs->nvqs; i++) {
                fsvq = &fs->vqs[i];
-               if (i == VQ_HIPRIO)
-                       drain_hiprio_queued_reqs(fsvq);
-
                virtio_fs_drain_queue(fsvq);
        }
 }
@@ -254,7 +248,7 @@ static void virtio_fs_hiprio_done_work(struct work_struct *work)
 
                while ((req = virtqueue_get_buf(vq, &len)) != NULL) {
                        kfree(req);
-                       fsvq->in_flight--;
+                       dec_in_flight_req(fsvq);
                }
        } while (!virtqueue_enable_cb(vq) && likely(!virtqueue_is_broken(vq)));
        spin_unlock(&fsvq->lock);
@@ -306,6 +300,7 @@ static void virtio_fs_hiprio_dispatch_work(struct work_struct *work)
 
                list_del(&forget->list);
                if (!fsvq->connected) {
+                       dec_in_flight_req(fsvq);
                        spin_unlock(&fsvq->lock);
                        kfree(forget);
                        continue;
@@ -327,13 +322,13 @@ static void virtio_fs_hiprio_dispatch_work(struct work_struct *work)
                        } else {
                                pr_debug("virtio-fs: Could not queue FORGET: err=%d. Dropping it.\n",
                                         ret);
+                               dec_in_flight_req(fsvq);
                                kfree(forget);
                        }
                        spin_unlock(&fsvq->lock);
                        return;
                }
 
-               fsvq->in_flight++;
                notify = virtqueue_kick_prepare(vq);
                spin_unlock(&fsvq->lock);
 
@@ -472,7 +467,7 @@ static void virtio_fs_requests_done_work(struct work_struct *work)
 
                fuse_request_end(fc, req);
                spin_lock(&fsvq->lock);
-               fsvq->in_flight--;
+               dec_in_flight_req(fsvq);
                spin_unlock(&fsvq->lock);
        }
 }
@@ -730,6 +725,7 @@ __releases(fiq->lock)
                        list_add_tail(&forget->list, &fsvq->queued_reqs);
                        schedule_delayed_work(&fsvq->dispatch_work,
                                        msecs_to_jiffies(1));
+                       inc_in_flight_req(fsvq);
                } else {
                        pr_debug("virtio-fs: Could not queue FORGET: err=%d. Dropping it.\n",
                                 ret);
@@ -739,7 +735,7 @@ __releases(fiq->lock)
                goto out;
        }
 
-       fsvq->in_flight++;
+       inc_in_flight_req(fsvq);
        notify = virtqueue_kick_prepare(vq);
 
        spin_unlock(&fsvq->lock);
@@ -921,7 +917,7 @@ static int virtio_fs_enqueue_req(struct virtio_fs_vq *fsvq,
        /* matches barrier in request_wait_answer() */
        smp_mb__after_atomic();
 
-       fsvq->in_flight++;
+       inc_in_flight_req(fsvq);
        notify = virtqueue_kick_prepare(vq);
 
        spin_unlock(&fsvq->lock);