On Tue, Apr 09, 2013 at 05:39:43PM +0800, Asias He wrote:
> This patch makes vhost_scsi_flush() wait for all the pending requests
> issued before the flush operation to be finished.
>
> Changes in v3:
> - Rebase
> - Drop 'tcm_vhost: Wait for pending requests in
> vhost_scsi_clear_endpoint()' in this series, we already did that in
> 'tcm_vhost: Use vq->private_data to indicate if the endpoint is setup'
>
> Changes in v2:
> - Increase/Decrease inflight requests in
> vhost_scsi_{allocate,free}_cmd and tcm_vhost_{allocate,free}_evt
>
> Signed-off-by: Asias He <asias@xxxxxxxxxx>
Nack, let's not do this home-grown here. Please use a kref.
The array of two trick is also too tricky for my taste.
Please replace during_flush in tcm_vhost_cmd and tcm_vhost_evt
by a kref pointer, allocate a new kref when you flush.
Access can be done with RCU so we won't need any locks.
> ---
> drivers/vhost/tcm_vhost.c | 88 ++++++++++++++++++++++++++++++++++++++++++++---
> drivers/vhost/tcm_vhost.h | 4 +++
> 2 files changed, 87 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/vhost/tcm_vhost.c b/drivers/vhost/tcm_vhost.c
> index 1f9116c..719ce13 100644
> --- a/drivers/vhost/tcm_vhost.c
> +++ b/drivers/vhost/tcm_vhost.c
> @@ -91,6 +91,15 @@ struct vhost_scsi {
> struct mutex vs_events_lock; /* protect vs_events_dropped,events_nr */
> bool vs_events_dropped; /* any missed events */
> int vs_events_nr; /* num of pending events */
> +
> + /*
> + * vs_inflight[0]/[1] are used to track requests issued
> + * before/during the flush operation
> + */
> + u64 vs_inflight[2];
> + wait_queue_head_t vs_flush_wait; /* wait queue for flush operation */
> + spinlock_t vs_flush_lock; /* lock to protect vs_during_flush */
> + int vs_during_flush; /* flag to indicate if we are in flush operation */
> };
>
> /* Local pointer to allocated TCM configfs fabric module */
> @@ -108,6 +117,46 @@ static int iov_num_pages(struct iovec *iov)
> ((unsigned long)iov->iov_base & PAGE_MASK)) >> PAGE_SHIFT;
> }
>
> +static int tcm_vhost_inc_inflight(struct vhost_scsi *vs)
> +{
> + int during_flush;
> +
> + spin_lock(&vs->vs_flush_lock);
> + during_flush = vs->vs_during_flush;
> + vs->vs_inflight[during_flush]++;
> + spin_unlock(&vs->vs_flush_lock);
> +
> + return during_flush;
> +}
> +
> +static void tcm_vhost_dec_inflight(struct vhost_scsi *vs, int during_flush)
> +{
> + u64 inflight;
> +
> + spin_lock(&vs->vs_flush_lock);
> + inflight = vs->vs_inflight[during_flush]--;
> + /*
> + * Wakeup the waiter when all the requests issued before the flush
> + * operation are finished and we are during the flush operation.
> + */
> + if (!inflight && !during_flush && vs->vs_during_flush)
> + wake_up(&vs->vs_flush_wait);
> + spin_unlock(&vs->vs_flush_lock);
> +}
> +
> +static bool tcm_vhost_done_inflight(struct vhost_scsi *vs)
> +{
> + bool ret = false;
> +
> + /* The requests issued before the flush operation are finished ? */
> + spin_lock(&vs->vs_flush_lock);
> + if (!vs->vs_inflight[0])
> + ret = true;
> + spin_unlock(&vs->vs_flush_lock);
> +
> + return ret;
> +}
> +
> static bool tcm_vhost_check_feature(struct vhost_scsi *vs, int feature)
> {
> bool ret = false;
> @@ -402,6 +451,7 @@ static int tcm_vhost_queue_tm_rsp(struct se_cmd *se_cmd)
> static void tcm_vhost_free_evt(struct vhost_scsi *vs, struct tcm_vhost_evt *evt)
> {
> mutex_lock(&vs->vs_events_lock);
> + tcm_vhost_dec_inflight(vs, evt->during_flush);
> vs->vs_events_nr--;
> kfree(evt);
> mutex_unlock(&vs->vs_events_lock);
> @@ -423,6 +473,7 @@ static struct tcm_vhost_evt *tcm_vhost_allocate_evt(struct vhost_scsi *vs,
> if (evt) {
> evt->event.event = event;
> evt->event.reason = reason;
> + evt->during_flush = tcm_vhost_inc_inflight(vs);
> vs->vs_events_nr++;
> }
> mutex_unlock(&vs->vs_events_lock);
> @@ -433,6 +484,7 @@ static struct tcm_vhost_evt *tcm_vhost_allocate_evt(struct vhost_scsi *vs,
> static void vhost_scsi_free_cmd(struct tcm_vhost_cmd *tv_cmd)
> {
> struct se_cmd *se_cmd = &tv_cmd->tvc_se_cmd;
> + struct vhost_scsi *vs = tv_cmd->tvc_vhost;
>
> /* TODO locking against target/backend threads? */
> transport_generic_free_cmd(se_cmd, 1);
> @@ -445,13 +497,16 @@ static void vhost_scsi_free_cmd(struct tcm_vhost_cmd *tv_cmd)
> kfree(tv_cmd->tvc_sgl);
> }
>
> + tcm_vhost_dec_inflight(vs, tv_cmd->during_flush);
> +
> kfree(tv_cmd);
> }
>
> static void tcm_vhost_do_evt_work(struct vhost_scsi *vs,
> - struct virtio_scsi_event *event)
> + struct tcm_vhost_evt *evt)
> {
> struct vhost_virtqueue *vq = &vs->vqs[VHOST_SCSI_VQ_EVT];
> + struct virtio_scsi_event *event = &evt->event;
> struct virtio_scsi_event __user *eventp;
> unsigned out, in;
> int head, ret;
> @@ -511,7 +566,7 @@ static void tcm_vhost_evt_work(struct vhost_work *work)
> while (llnode) {
> evt = llist_entry(llnode, struct tcm_vhost_evt, list);
> llnode = llist_next(llnode);
> - tcm_vhost_do_evt_work(vs, &evt->event);
> + tcm_vhost_do_evt_work(vs, evt);
> tcm_vhost_free_evt(vs, evt);
> }
> }
> @@ -529,8 +584,8 @@ static void vhost_scsi_complete_cmd_work(struct vhost_work *work)
> struct virtio_scsi_cmd_resp v_rsp;
> struct tcm_vhost_cmd *tv_cmd;
> struct llist_node *llnode;
> - struct se_cmd *se_cmd;
> int ret, vq;
> + struct se_cmd *se_cmd;
>
> bitmap_zero(signal, VHOST_SCSI_MAX_VQ);
> llnode = llist_del_all(&vs->vs_completion_list);
> @@ -568,6 +623,7 @@ static void vhost_scsi_complete_cmd_work(struct vhost_work *work)
> }
>
> static struct tcm_vhost_cmd *vhost_scsi_allocate_cmd(
> + struct vhost_scsi *vs,
> struct tcm_vhost_tpg *tv_tpg,
> struct virtio_scsi_cmd_req *v_req,
> u32 exp_data_len,
> @@ -592,6 +648,8 @@ static struct tcm_vhost_cmd *vhost_scsi_allocate_cmd(
> tv_cmd->tvc_exp_data_len = exp_data_len;
> tv_cmd->tvc_data_direction = data_direction;
> tv_cmd->tvc_nexus = tv_nexus;
> + tv_cmd->tvc_vhost = vs;
> + tv_cmd->during_flush = tcm_vhost_inc_inflight(vs);
>
> return tv_cmd;
> }
> @@ -842,7 +900,7 @@ static void vhost_scsi_handle_vq(struct vhost_scsi *vs,
> for (i = 0; i < data_num; i++)
> exp_data_len += vq->iov[data_first + i].iov_len;
>
> - tv_cmd = vhost_scsi_allocate_cmd(tv_tpg, &v_req,
> + tv_cmd = vhost_scsi_allocate_cmd(vs, tv_tpg, &v_req,
> exp_data_len, data_direction);
> if (IS_ERR(tv_cmd)) {
> vq_err(vq, "vhost_scsi_allocate_cmd failed %ld\n",
> @@ -852,7 +910,6 @@ static void vhost_scsi_handle_vq(struct vhost_scsi *vs,
> pr_debug("Allocated tv_cmd: %p exp_data_len: %d, data_direction"
> ": %d\n", tv_cmd, exp_data_len, data_direction);
>
> - tv_cmd->tvc_vhost = vs;
> tv_cmd->tvc_vq = vq;
>
> if (unlikely(vq->iov[out].iov_len !=
> @@ -905,6 +962,7 @@ static void vhost_scsi_handle_vq(struct vhost_scsi *vs,
> * tcm_vhost_queue_data_in() and tcm_vhost_queue_status()
> */
> tv_cmd->tvc_vq_desc = head;
> +
> /*
> * Dispatch tv_cmd descriptor for cmwq execution in process
> * context provided by tcm_vhost_workqueue. This also ensures
> @@ -984,9 +1042,23 @@ static void vhost_scsi_flush(struct vhost_scsi *vs)
> {
> int i;
>
> + /* Flush operation is started */
> + spin_lock(&vs->vs_flush_lock);
> + vs->vs_during_flush = 1;
> + spin_unlock(&vs->vs_flush_lock);
> +
> for (i = 0; i < VHOST_SCSI_MAX_VQ; i++)
> vhost_scsi_flush_vq(vs, i);
> vhost_work_flush(&vs->dev, &vs->vs_completion_work);
> + vhost_work_flush(&vs->dev, &vs->vs_event_work);
> +
> + /* Wait until all requests issued before the flush to be finished */
> + wait_event(vs->vs_flush_wait, tcm_vhost_done_inflight(vs));
> +
> + /* Flush operation is finished */
> + spin_lock(&vs->vs_flush_lock);
> + vs->vs_during_flush = 0;
> + spin_unlock(&vs->vs_flush_lock);
> }
>
> /*
> @@ -1094,6 +1166,7 @@ static int vhost_scsi_clear_endpoint(
> u8 target;
>
> mutex_lock(&vs->dev.mutex);
> +
> /* Verify that ring has been setup correctly. */
> for (index = 0; index < vs->dev.nvqs; ++index) {
> if (!vhost_vq_access_ok(&vs->vqs[index])) {
> @@ -1195,6 +1268,11 @@ static int vhost_scsi_open(struct inode *inode, struct file *f)
> s->vs_events_dropped = false;
> mutex_init(&s->vs_events_lock);
>
> + s->vs_inflight[0] = 0;
> + s->vs_inflight[1] = 0;
> + spin_lock_init(&s->vs_flush_lock);
> + init_waitqueue_head(&s->vs_flush_wait);
> +
> s->vqs[VHOST_SCSI_VQ_CTL].handle_kick = vhost_scsi_ctl_handle_kick;
> s->vqs[VHOST_SCSI_VQ_EVT].handle_kick = vhost_scsi_evt_handle_kick;
> for (i = VHOST_SCSI_VQ_IO; i < VHOST_SCSI_MAX_VQ; i++)
> diff --git a/drivers/vhost/tcm_vhost.h b/drivers/vhost/tcm_vhost.h
> index 94e9ee53..dd84622 100644
> --- a/drivers/vhost/tcm_vhost.h
> +++ b/drivers/vhost/tcm_vhost.h
> @@ -37,6 +37,8 @@ struct tcm_vhost_cmd {
> unsigned char tvc_sense_buf[TRANSPORT_SENSE_BUFFER];
> /* Completed commands list, serviced from vhost worker thread */
> struct llist_node tvc_completion_list;
> + /* Indicate this command is issued during the flush operaton */
> + int during_flush;
> };
>
> struct tcm_vhost_nexus {
> @@ -91,6 +93,8 @@ struct tcm_vhost_evt {
> struct virtio_scsi_event event;
> /* virtio_scsi event list, serviced from vhost worker thread */
> struct llist_node list;
> + /* Indicate this event is issued during the flush operaton */
> + int during_flush;
> };
>
> /*
> --
> 1.8.1.4
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