[PATCH v2 1/1] Add timer to handle OOM situations

[ggarcia]

From: Gerard Garcia <ggar...@deic.uab.cat>

v2:
* Use of ERR_PTR/PTR_ERR/IS_ERR
* Timer cleaned on device release.
* Do not process more packets on error.

Signed-off-by: Gerard Garcia <ggar...@deic.uab.cat>
---
 drivers/vhost/vsock.c | 55 +++++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 45 insertions(+), 10 deletions(-)

diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
index 17bfe4e..5c6879d 100644
--- a/drivers/vhost/vsock.c
+++ b/drivers/vhost/vsock.c
@@ -14,11 +14,13 @@
 #include <net/sock.h>
 #include <linux/virtio_vsock.h>
 #include <linux/vhost.h>
+#include <linux/timer.h>
 
 #include <net/af_vsock.h>
 #include "vhost.h"
 
 #define VHOST_VSOCK_DEFAULT_HOST_CID   2
+#define OOM_RETRY_MS   100
 
 enum {
        VHOST_VSOCK_FEATURES = VHOST_FEATURES,
@@ -43,8 +45,12 @@ struct vhost_vsock {
        u32 total_tx_buf;
 
        u32 guest_cid;
+
+       struct timer_list tx_kick;
 };
 
+
+
 static u32 vhost_transport_get_local_cid(void)
 {
        return VHOST_VSOCK_DEFAULT_HOST_CID;
@@ -282,12 +288,13 @@ vhost_vsock_alloc_pkt(struct vhost_virtqueue *vq,
 
        if (in != 0) {
                vq_err(vq, "Expected 0 input buffers, got %u\n", in);
-               return NULL;
+               return ERR_PTR(-EINVAL);
        }
 
        pkt = kzalloc(sizeof(*pkt), GFP_KERNEL);
-       if (!pkt)
-               return NULL;
+       if (!pkt){
+               return ERR_PTR(-ENOMEM);
+       }
 
        len = iov_length(vq->iov, out);
        iov_iter_init(&iov_iter, WRITE, vq->iov, out, len);
@@ -297,7 +304,7 @@ vhost_vsock_alloc_pkt(struct vhost_virtqueue *vq,
                vq_err(vq, "Expected %zu bytes for pkt->hdr, got %zu bytes\n",
                       sizeof(pkt->hdr), nbytes);
                kfree(pkt);
-               return NULL;
+               return ERR_PTR(-EINVAL);
        }
 
        if (le16_to_cpu(pkt->hdr.type) == VIRTIO_VSOCK_TYPE_STREAM)
@@ -310,13 +317,13 @@ vhost_vsock_alloc_pkt(struct vhost_virtqueue *vq,
        /* The pkt is too big */
        if (pkt->len > VIRTIO_VSOCK_MAX_PKT_BUF_SIZE) {
                kfree(pkt);
-               return NULL;
+               return ERR_PTR(-EINVAL);
        }
 
        pkt->buf = kmalloc(pkt->len, GFP_KERNEL);
        if (!pkt->buf) {
                kfree(pkt);
-               return NULL;
+               return ERR_PTR(-EINVAL);
        }
 
        nbytes = copy_from_iter(pkt->buf, pkt->len, &iov_iter);
@@ -324,7 +331,7 @@ vhost_vsock_alloc_pkt(struct vhost_virtqueue *vq,
                vq_err(vq, "Expected %u byte payload, got %zu bytes\n",
                       pkt->len, nbytes);
                virtio_transport_free_pkt(pkt);
-               return NULL;
+               return ERR_PTR(-EINVAL);
        }
 
        return pkt;
@@ -362,9 +369,26 @@ static void vhost_vsock_handle_tx_kick(struct vhost_work 
*work)
                }
 
                pkt = vhost_vsock_alloc_pkt(vq, out, in);
-               if (!pkt) {
-                       vq_err(vq, "Faulted on pkt\n");
-                       continue;
+
+               if (IS_ERR(pkt)) {
+                       if (PTR_ERR(pkt) == -ENOMEM) {
+                               vhost_discard_vq_desc(vq, 1);
+
+                               if (!timer_pending(&vsock->tx_kick)) {
+                                       vsock->tx_kick.data =
+                                               (unsigned long) vq;
+                                       vsock->tx_kick.expires =
+                                               jiffies + 
msecs_to_jiffies(OOM_RETRY_MS);
+                                       add_timer(&vsock->tx_kick);
+                               }
+
+                               break;
+                       } else {
+                               vq_err(vq, "Faulted on pkt\n");
+                               break;
+                       }
+               } else if (unlikely(timer_pending(&vsock->tx_kick))) {
+                       del_timer(&vsock->tx_kick);
                }
 
                /* Only accept correctly addressed packets */
@@ -383,6 +407,13 @@ out:
        mutex_unlock(&vq->mutex);
 }
 
+static void vhost_vsock_rehandle_tx_kick(unsigned long data)
+{
+       struct vhost_virtqueue *vq = (struct vhost_virtqueue *) data;
+
+       vhost_poll_queue(&vq->poll);
+}
+
 static void vhost_vsock_handle_rx_kick(struct vhost_work *work)
 {
        struct vhost_virtqueue *vq = container_of(work, struct vhost_virtqueue,
@@ -493,6 +524,9 @@ static int vhost_vsock_dev_open(struct inode *inode, struct 
file *file)
                goto out;
        }
 
+       setup_timer(&vsock->tx_kick,
+                   vhost_vsock_rehandle_tx_kick, (unsigned long) NULL);
+
        vqs[VSOCK_VQ_TX] = &vsock->vqs[VSOCK_VQ_TX];
        vqs[VSOCK_VQ_RX] = &vsock->vqs[VSOCK_VQ_RX];
        vsock->vqs[VSOCK_VQ_TX].handle_kick = vhost_vsock_handle_tx_kick;
@@ -555,6 +589,7 @@ static int vhost_vsock_dev_release(struct inode *inode, 
struct file *file)
        vhost_dev_stop(&vsock->dev);
        vhost_dev_cleanup(&vsock->dev, false);
        kfree(vsock->dev.vqs);
+       del_timer(&vsock->tx_kick);
        vhost_vsock_free(vsock);
        return 0;
 }
-- 
2.9.1