diff mbox

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

Message ID 20160726142821.31770-2-ggarcia@deic.uab.cat
State Not Applicable, archived
Delegated to: David Miller
Headers show

Commit Message

ggarcia@abra.uab.cat July 26, 2016, 2:28 p.m. UTC 
From: Gerard Garcia <ggarcia@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 <ggarcia@deic.uab.cat>
---
 drivers/vhost/vsock.c | 55 +++++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 45 insertions(+), 10 deletions(-)

Comments

Stefan Hajnoczi July 29, 2016, 12:20 p.m. UTC | #1 
On Tue, Jul 26, 2016 at 04:28:21PM +0200, ggarcia@abra.uab.cat wrote:
> @@ -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);

Please use del_timer_sync() so that we know the timer callback has
finished executing if it's racing with us.

Also please figure out the correct ordering of this call so
vhost_poll_queue() doesn't crash if the timer fires while we are
executing vhost_vsock_dev_release().  In other words, vq and vq->poll
must still be alive when we delete the timer, otherwise the callback
could fire an run on a vq that has already been cleaned up by
vhost_vsock_dev_release().
diff mbox

Patch

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;
 }