Commit 4f7f46d3 authored by Asias He's avatar Asias He Committed by Nicholas Bellinger
Browse files

tcm_vhost: Use vq->private_data to indicate if the endpoint is setup 



Currently, vs->vs_endpoint is used indicate if the endpoint is setup or
not. It is set or cleared in vhost_scsi_set_endpoint() or
vhost_scsi_clear_endpoint() under the vs->dev.mutex lock. However, when
we check it in vhost_scsi_handle_vq(), we ignored the lock.

Instead of using the vs->vs_endpoint and the vs->dev.mutex lock to
indicate the status of the endpoint, we use per virtqueue
vq->private_data to indicate it. In this way, we can only take the
vq->mutex lock which is per queue and make the concurrent multiqueue
process having less lock contention. Further, in the read side of
vq->private_data, we can even do not take the lock if it is accessed in
the vhost worker thread, because it is protected by "vhost rcu".

(nab: Do s/VHOST_FEATURES/~VHOST_SCSI_FEATURES)

Signed-off-by: default avatarAsias He <asias@redhat.com>
Acked-by: default avatarMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: default avatarNicholas Bellinger <nab@linux-iscsi.org>
parent af0d9187

drivers/vhost/tcm_vhost.c

+101 −43
Original line number Diff line number Diff line
@@ -74,9 +74,8 @@ enum { 


struct vhost_scsi {

	/* Protected by vhost_scsi->dev.mutex */

	struct tcm_vhost_tpg *vs_tpg[VHOST_SCSI_MAX_TARGET];

	struct tcm_vhost_tpg **vs_tpg;

	char vs_vhost_wwpn[TRANSPORT_IQN_LEN];

	bool vs_endpoint;



	struct vhost_dev dev;

	struct vhost_virtqueue vqs[VHOST_SCSI_MAX_VQ];
@@ -582,6 +581,7 @@ static void tcm_vhost_submission_work(struct work_struct *work) 
static void vhost_scsi_handle_vq(struct vhost_scsi *vs,

	struct vhost_virtqueue *vq)

{

	struct tcm_vhost_tpg **vs_tpg;

	struct virtio_scsi_cmd_req v_req;

	struct tcm_vhost_tpg *tv_tpg;

	struct tcm_vhost_cmd *tv_cmd;
@@ -590,8 +590,16 @@ static void vhost_scsi_handle_vq(struct vhost_scsi *vs, 
	int head, ret;

	u8 target;



	/* Must use ioctl VHOST_SCSI_SET_ENDPOINT */

	if (unlikely(!vs->vs_endpoint))

	/*

	 * We can handle the vq only after the endpoint is setup by calling the

	 * VHOST_SCSI_SET_ENDPOINT ioctl.

	 *

	 * TODO: Check that we are running from vhost_worker which acts

	 * as read-side critical section for vhost kind of RCU.

	 * See the comments in struct vhost_virtqueue in drivers/vhost/vhost.h

	 */

	vs_tpg = rcu_dereference_check(vq->private_data, 1);

	if (!vs_tpg)

		return;



	mutex_lock(&vq->mutex);
@@ -661,7 +669,7 @@ static void vhost_scsi_handle_vq(struct vhost_scsi *vs, 


		/* Extract the tpgt */

		target = v_req.lun[1];

		tv_tpg = ACCESS_ONCE(vs->vs_tpg[target]);

		tv_tpg = ACCESS_ONCE(vs_tpg[target]);



		/* Target does not exist, fail the request */

		if (unlikely(!tv_tpg)) {
@@ -780,6 +788,20 @@ static void vhost_scsi_handle_kick(struct vhost_work *work) 
	vhost_scsi_handle_vq(vs, vq);

}



static void vhost_scsi_flush_vq(struct vhost_scsi *vs, int index)

{

	vhost_poll_flush(&vs->dev.vqs[index].poll);

}



static void vhost_scsi_flush(struct vhost_scsi *vs)

{

	int i;



	for (i = 0; i < VHOST_SCSI_MAX_VQ; i++)

		vhost_scsi_flush_vq(vs, i);

	vhost_work_flush(&vs->dev, &vs->vs_completion_work);

}



/*

 * Called from vhost_scsi_ioctl() context to walk the list of available

 * tcm_vhost_tpg with an active struct tcm_vhost_nexus
@@ -790,8 +812,10 @@ static int vhost_scsi_set_endpoint( 
{

	struct tcm_vhost_tport *tv_tport;

	struct tcm_vhost_tpg *tv_tpg;

	struct tcm_vhost_tpg **vs_tpg;

	struct vhost_virtqueue *vq;

	int index, ret, i, len;

	bool match = false;

	int index, ret;



	mutex_lock(&vs->dev.mutex);

	/* Verify that ring has been setup correctly. */
@@ -803,6 +827,15 @@ static int vhost_scsi_set_endpoint( 
		}

	}



	len = sizeof(vs_tpg[0]) * VHOST_SCSI_MAX_TARGET;

	vs_tpg = kzalloc(len, GFP_KERNEL);

	if (!vs_tpg) {

		mutex_unlock(&vs->dev.mutex);

		return -ENOMEM;

	}

	if (vs->vs_tpg)

		memcpy(vs_tpg, vs->vs_tpg, len);



	mutex_lock(&tcm_vhost_mutex);

	list_for_each_entry(tv_tpg, &tcm_vhost_list, tv_tpg_list) {

		mutex_lock(&tv_tpg->tv_tpg_mutex);
@@ -817,14 +850,15 @@ static int vhost_scsi_set_endpoint( 
		tv_tport = tv_tpg->tport;



		if (!strcmp(tv_tport->tport_name, t->vhost_wwpn)) {

			if (vs->vs_tpg[tv_tpg->tport_tpgt]) {

			if (vs->vs_tpg && vs->vs_tpg[tv_tpg->tport_tpgt]) {

				mutex_unlock(&tv_tpg->tv_tpg_mutex);

				mutex_unlock(&tcm_vhost_mutex);

				mutex_unlock(&vs->dev.mutex);

				kfree(vs_tpg);

				return -EEXIST;

			}

			tv_tpg->tv_tpg_vhost_count++;

			vs->vs_tpg[tv_tpg->tport_tpgt] = tv_tpg;

			vs_tpg[tv_tpg->tport_tpgt] = tv_tpg;

			smp_mb__after_atomic_inc();

			match = true;

		}
@@ -835,12 +869,26 @@ static int vhost_scsi_set_endpoint( 
	if (match) {

		memcpy(vs->vs_vhost_wwpn, t->vhost_wwpn,

		       sizeof(vs->vs_vhost_wwpn));

		vs->vs_endpoint = true;

		for (i = 0; i < VHOST_SCSI_MAX_VQ; i++) {

			vq = &vs->vqs[i];

			/* Flushing the vhost_work acts as synchronize_rcu */

			mutex_lock(&vq->mutex);

			rcu_assign_pointer(vq->private_data, vs_tpg);

			mutex_unlock(&vq->mutex);

		}

		ret = 0;

	} else {

		ret = -EEXIST;

	}



	/*

	 * Act as synchronize_rcu to make sure access to

	 * old vs->vs_tpg is finished.

	 */

	vhost_scsi_flush(vs);

	kfree(vs->vs_tpg);

	vs->vs_tpg = vs_tpg;



	mutex_unlock(&vs->dev.mutex);

	return ret;

}
@@ -851,6 +899,8 @@ static int vhost_scsi_clear_endpoint( 
{

	struct tcm_vhost_tport *tv_tport;

	struct tcm_vhost_tpg *tv_tpg;

	struct vhost_virtqueue *vq;

	bool match = false;

	int index, ret, i;

	u8 target;
@@ -862,9 +912,14 @@ static int vhost_scsi_clear_endpoint( 
			goto err_dev;

		}

	}



	if (!vs->vs_tpg) {

		mutex_unlock(&vs->dev.mutex);

		return 0;

	}



	for (i = 0; i < VHOST_SCSI_MAX_TARGET; i++) {

		target = i;



		tv_tpg = vs->vs_tpg[target];

		if (!tv_tpg)

			continue;
@@ -886,10 +941,27 @@ static int vhost_scsi_clear_endpoint( 
		}

		tv_tpg->tv_tpg_vhost_count--;

		vs->vs_tpg[target] = NULL;

		vs->vs_endpoint = false;

		match = true;

		mutex_unlock(&tv_tpg->tv_tpg_mutex);

	}

	if (match) {

		for (i = 0; i < VHOST_SCSI_MAX_VQ; i++) {

			vq = &vs->vqs[i];

			/* Flushing the vhost_work acts as synchronize_rcu */

			mutex_lock(&vq->mutex);

			rcu_assign_pointer(vq->private_data, NULL);

			mutex_unlock(&vq->mutex);

		}

	}

	/*

	 * Act as synchronize_rcu to make sure access to

	 * old vs->vs_tpg is finished.

	 */

	vhost_scsi_flush(vs);

	kfree(vs->vs_tpg);

	vs->vs_tpg = NULL;

	mutex_unlock(&vs->dev.mutex);



	return 0;



err_tpg:
@@ -899,6 +971,24 @@ err_dev: 
	return ret;

}



static int vhost_scsi_set_features(struct vhost_scsi *vs, u64 features)

{

	if (features & ~VHOST_SCSI_FEATURES)

		return -EOPNOTSUPP;



	mutex_lock(&vs->dev.mutex);

	if ((features & (1 << VHOST_F_LOG_ALL)) &&

	    !vhost_log_access_ok(&vs->dev)) {

		mutex_unlock(&vs->dev.mutex);

		return -EFAULT;

	}

	vs->dev.acked_features = features;

	smp_wmb();

	vhost_scsi_flush(vs);

	mutex_unlock(&vs->dev.mutex);

	return 0;

}



static int vhost_scsi_open(struct inode *inode, struct file *f)

{

	struct vhost_scsi *s;
@@ -939,38 +1029,6 @@ static int vhost_scsi_release(struct inode *inode, struct file *f) 
	return 0;

}



static void vhost_scsi_flush_vq(struct vhost_scsi *vs, int index)

{

	vhost_poll_flush(&vs->dev.vqs[index].poll);

}



static void vhost_scsi_flush(struct vhost_scsi *vs)

{

	int i;



	for (i = 0; i < VHOST_SCSI_MAX_VQ; i++)

		vhost_scsi_flush_vq(vs, i);

	vhost_work_flush(&vs->dev, &vs->vs_completion_work);

}



static int vhost_scsi_set_features(struct vhost_scsi *vs, u64 features)

{

	if (features & ~VHOST_SCSI_FEATURES)

		return -EOPNOTSUPP;



	mutex_lock(&vs->dev.mutex);

	if ((features & (1 << VHOST_F_LOG_ALL)) &&

	    !vhost_log_access_ok(&vs->dev)) {

		mutex_unlock(&vs->dev.mutex);

		return -EFAULT;

	}

	vs->dev.acked_features = features;

	smp_wmb();

	vhost_scsi_flush(vs);

	mutex_unlock(&vs->dev.mutex);

	return 0;

}



static long vhost_scsi_ioctl(struct file *f, unsigned int ioctl,

				unsigned long arg)

{

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