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Subject[PATCH 38/52] Dispatch FORGET requests later instead of dropping them
Date
If virtio queue is full, then don't drop FORGET requests. Instead, wait
a bit and try to dispatch these little later using a worker thread.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
---
fs/fuse/virtio_fs.c | 86 ++++++++++++++++++++++++++++++++++++++++++++++++-----
1 file changed, 78 insertions(+), 8 deletions(-)

diff --git a/fs/fuse/virtio_fs.c b/fs/fuse/virtio_fs.c
index 98dba3cf9d40..f436f5b3f85c 100644
--- a/fs/fuse/virtio_fs.c
+++ b/fs/fuse/virtio_fs.c
@@ -22,6 +22,8 @@ static LIST_HEAD(virtio_fs_instances);
struct virtio_fs_vq {
struct virtqueue *vq; /* protected by fpq->lock */
struct work_struct done_work;
+ struct list_head queued_reqs;
+ struct delayed_work dispatch_work;
struct fuse_dev *fud;
char name[24];
} ____cacheline_aligned_in_smp;
@@ -53,6 +55,13 @@ struct virtio_fs {
size_t window_len;
};

+struct virtio_fs_forget {
+ struct fuse_in_header ih;
+ struct fuse_forget_in arg;
+ /* This request can be temporarily queued on virt queue */
+ struct list_head list;
+};
+
/* TODO: This should be in a PCI file somewhere */
static int virtio_pci_find_shm_cap(struct pci_dev *dev,
u8 required_id,
@@ -189,6 +198,7 @@ static void virtio_fs_free_devs(struct virtio_fs *fs)
continue;

flush_work(&fsvq->done_work);
+ flush_delayed_work(&fsvq->dispatch_work);

fuse_dev_free(fsvq->fud); /* TODO need to quiesce/end_requests/decrement dev_count */
fsvq->fud = NULL;
@@ -252,6 +262,58 @@ static void virtio_fs_hiprio_done_work(struct work_struct *work)
spin_unlock(&fpq->lock);
}

+static void virtio_fs_dummy_dispatch_work(struct work_struct *work)
+{
+ return;
+}
+
+static void virtio_fs_hiprio_dispatch_work(struct work_struct *work)
+{
+ struct virtio_fs_forget *forget;
+ struct virtio_fs_vq *fsvq = container_of(work, struct virtio_fs_vq,
+ dispatch_work.work);
+ struct fuse_pqueue *fpq = &fsvq->fud->pq;
+ struct virtqueue *vq = fsvq->vq;
+ struct scatterlist sg;
+ struct scatterlist *sgs[] = {&sg};
+ bool notify;
+ int ret;
+
+ pr_debug("worker virtio_fs_hiprio_dispatch_work() called.\n");
+ while(1) {
+ spin_lock(&fpq->lock);
+ forget = list_first_entry_or_null(&fsvq->queued_reqs,
+ struct virtio_fs_forget, list);
+ if (!forget) {
+ spin_unlock(&fpq->lock);
+ return;
+ }
+
+ list_del(&forget->list);
+ sg_init_one(&sg, forget, sizeof(*forget));
+
+ /* Enqueue the request */
+ dev_dbg(&vq->vdev->dev, "%s\n", __func__);
+ ret = virtqueue_add_sgs(vq, sgs, 1, 0, forget, GFP_ATOMIC);
+ if (ret < 0) {
+ pr_debug("virtio-fs: Could not queue FORGET: queue full. Will try later\n");
+ list_add_tail(&forget->list, &fsvq->queued_reqs);
+ schedule_delayed_work(&fsvq->dispatch_work,
+ msecs_to_jiffies(1));
+ /* TODO handle full virtqueue */
+ spin_unlock(&fpq->lock);
+ return;
+ }
+
+ notify = virtqueue_kick_prepare(vq);
+ spin_unlock(&fpq->lock);
+
+ if (notify)
+ virtqueue_notify(vq);
+ pr_debug("worker virtio_fs_hiprio_dispatch_work() dispatched one forget request.\n");
+ }
+}
+
/* Allocate and copy args into req->argbuf */
static int copy_args_to_argbuf(struct fuse_req *req)
{
@@ -404,15 +466,24 @@ static int virtio_fs_setup_vqs(struct virtio_device *vdev,
snprintf(fs->vqs[0].name, sizeof(fs->vqs[0].name), "notifications");
INIT_WORK(&fs->vqs[0].done_work, virtio_fs_notifications_done_work);
names[0] = fs->vqs[0].name;
+ INIT_LIST_HEAD(&fs->vqs[0].queued_reqs);
+ INIT_DELAYED_WORK(&fs->vqs[0].dispatch_work,
+ virtio_fs_dummy_dispatch_work);

callbacks[1] = virtio_fs_vq_done;
snprintf(fs->vqs[1].name, sizeof(fs->vqs[1].name), "hiprio");
names[1] = fs->vqs[1].name;
INIT_WORK(&fs->vqs[1].done_work, virtio_fs_hiprio_done_work);
+ INIT_LIST_HEAD(&fs->vqs[1].queued_reqs);
+ INIT_DELAYED_WORK(&fs->vqs[1].dispatch_work,
+ virtio_fs_hiprio_dispatch_work);

/* Initialize the requests virtqueues */
for (i = 2; i < fs->nvqs; i++) {
INIT_WORK(&fs->vqs[i].done_work, virtio_fs_requests_done_work);
+ INIT_DELAYED_WORK(&fs->vqs[i].dispatch_work,
+ virtio_fs_dummy_dispatch_work);
+ INIT_LIST_HEAD(&fs->vqs[i].queued_reqs);
snprintf(fs->vqs[i].name, sizeof(fs->vqs[i].name),
"requests.%u", i - 2);
callbacks[i] = virtio_fs_vq_done;
@@ -718,11 +789,6 @@ static struct virtio_driver virtio_fs_driver = {
#endif
};

-struct virtio_fs_forget {
- struct fuse_in_header ih;
- struct fuse_forget_in arg;
-};
-
static void virtio_fs_wake_forget_and_unlock(struct fuse_iqueue *fiq)
__releases(fiq->waitq.lock)
{
@@ -733,6 +799,7 @@ __releases(fiq->waitq.lock)
struct scatterlist *sgs[] = {&sg};
struct virtio_fs *fs;
struct virtqueue *vq;
+ struct virtio_fs_vq *fsvq;
bool notify;
u64 unique;
int ret;
@@ -746,7 +813,7 @@ __releases(fiq->waitq.lock)
unique = fuse_get_unique(fiq);

fs = fiq->priv;
-
+ fsvq = &fs->vqs[1];
spin_unlock(&fiq->waitq.lock);

/* Allocate a buffer for the request */
@@ -769,14 +836,17 @@ __releases(fiq->waitq.lock)
sg_init_one(&sg, forget, sizeof(*forget));

/* Enqueue the request */
- vq = fs->vqs[1].vq;
+ vq = fsvq->vq;
dev_dbg(&vq->vdev->dev, "%s\n", __func__);
fpq = vq_to_fpq(vq);
spin_lock(&fpq->lock);

ret = virtqueue_add_sgs(vq, sgs, 1, 0, forget, GFP_ATOMIC);
if (ret < 0) {
- pr_err("virtio-fs: dropped FORGET: queue full\n");
+ pr_debug("virtio-fs: Could not queue FORGET: queue full. Will try later\n");
+ list_add_tail(&forget->list, &fsvq->queued_reqs);
+ schedule_delayed_work(&fsvq->dispatch_work,
+ msecs_to_jiffies(1));
/* TODO handle full virtqueue */
spin_unlock(&fpq->lock);
goto out;
--
2.13.6
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