On Tue, Apr 16, 2013 at 05:16:51PM +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 v5:
> - Use kref and completion
> - Fail req if vs->vs_inflight is NULL
> - Rename tcm_vhost_alloc_inflight to tcm_vhost_set_inflight
>
> Changes in v4:
> - Introduce vhost_scsi_inflight
> - Drop array to track flush
> - Use RCU to protect vs_inflight explicitly
>
> 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>
OK looks good, except error handling needs to be fixed.
> ---
> drivers/vhost/tcm_vhost.c | 101 +++++++++++++++++++++++++++++++++++++++++++---
> drivers/vhost/tcm_vhost.h | 5 +++
> 2 files changed, 101 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/vhost/tcm_vhost.c b/drivers/vhost/tcm_vhost.c
> index 4ae6725..ef40a8f 100644
> --- a/drivers/vhost/tcm_vhost.c
> +++ b/drivers/vhost/tcm_vhost.c
> @@ -74,6 +74,11 @@ enum {
> #define VHOST_SCSI_MAX_VQ 128
> #define VHOST_SCSI_MAX_EVENT 128
>
> +struct vhost_scsi_inflight {
> + struct completion comp; /* Wait for the flush operation to finish */
> + struct kref kref; /* Refcount for the inflight reqs */
> +};
> +
> struct vhost_scsi {
> /* Protected by vhost_scsi->dev.mutex */
> struct tcm_vhost_tpg **vs_tpg;
> @@ -91,6 +96,8 @@ 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 */
> +
> + struct vhost_scsi_inflight __rcu *vs_inflight; /* track inflight reqs */
> };
>
> /* Local pointer to allocated TCM configfs fabric module */
> @@ -108,6 +115,51 @@ static int iov_num_pages(struct iovec *iov)
> ((unsigned long)iov->iov_base & PAGE_MASK)) >> PAGE_SHIFT;
> }
>
> +static int tcm_vhost_set_inflight(struct vhost_scsi *vs)
> +{
> + struct vhost_scsi_inflight *inflight;
> + int ret = -ENOMEM;
> +
> + inflight = kzalloc(sizeof(*inflight), GFP_KERNEL);
kzalloc is not needed, you initialize all fields.
> + if (inflight) {
> + kref_init(&inflight->kref);
> + init_completion(&inflight->comp);
> + ret = 0;
> + }
> + rcu_assign_pointer(vs->vs_inflight, inflight);
So if allocation fails, we stop tracking inflights?
This looks strange, and could break guests. Why not the usual
if (!inflight)
return -ENOMEM;
> + synchronize_rcu();
open call is different:
- sync is not needed
- should use RCU_INIT_POINTER and not rcu_assign_pointer
So please move these out and make this function return the struct:
struct vhost_scsi_inflight *inflight
tcm_vhost_alloc_inflight(void)
> +
> + return ret;
> +}
> +
> +static struct vhost_scsi_inflight *
> +tcm_vhost_inc_inflight(struct vhost_scsi *vs)
And then inc will not need to return inflight pointer,
which is really unusual.
> +{
> + struct vhost_scsi_inflight *inflight;
> +
> + rcu_read_lock();
> + inflight = rcu_dereference(vs->vs_inflight);
> + if (inflight)
> + kref_get(&inflight->kref);
> + rcu_read_unlock();
> +
> + return inflight;
> +}
> +
> +void tcm_vhost_done_inflight(struct kref *kref)
> +{
> + struct vhost_scsi_inflight *inflight;
> +
> + inflight = container_of(kref, struct vhost_scsi_inflight, kref);
> + complete(&inflight->comp);
> +}
> +
> +static void tcm_vhost_dec_inflight(struct vhost_scsi_inflight *inflight)
> +{
> + if (inflight)
Here as in other places, inflight must never be NULL.
Pls fix code so that invariant holds.
> + kref_put(&inflight->kref, tcm_vhost_done_inflight);
> +}
> +
> static bool tcm_vhost_check_feature(struct vhost_scsi *vs, int feature)
> {
> bool ret = false;
> @@ -402,6 +454,7 @@ 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(evt->inflight);
> vs->vs_events_nr--;
> kfree(evt);
> mutex_unlock(&vs->vs_events_lock);
> @@ -413,21 +466,27 @@ static struct tcm_vhost_evt *tcm_vhost_allocate_evt(struct vhost_scsi *vs,
> struct tcm_vhost_evt *evt;
>
> mutex_lock(&vs->vs_events_lock);
> - if (vs->vs_events_nr > VHOST_SCSI_MAX_EVENT) {
> - vs->vs_events_dropped = true;
> - mutex_unlock(&vs->vs_events_lock);
> - return NULL;
> - }
> + if (vs->vs_events_nr > VHOST_SCSI_MAX_EVENT)
> + goto out;
>
> evt = kzalloc(sizeof(*evt), GFP_KERNEL);
BTW it looks like we should replace this kzalloc with kmalloc.
Should be a separate patch ...
> if (evt) {
> evt->event.event = event;
> evt->event.reason = reason;
> + evt->inflight = tcm_vhost_inc_inflight(vs);
> + if (!evt->inflight) {
We drop an event because earlier
we run out of memory for allocating the inflight counter.
Does not make sense to me.
> + kfree(evt);
> + goto out;
> + }
> vs->vs_events_nr++;
> }
> mutex_unlock(&vs->vs_events_lock);
>
> return evt;
> +out:
> + vs->vs_events_dropped = true;
> + mutex_unlock(&vs->vs_events_lock);
> + return NULL;
> }
>
> static void vhost_scsi_free_cmd(struct tcm_vhost_cmd *tv_cmd)
> @@ -445,6 +504,8 @@ static void vhost_scsi_free_cmd(struct tcm_vhost_cmd *tv_cmd)
> kfree(tv_cmd->tvc_sgl);
> }
>
> + tcm_vhost_dec_inflight(tv_cmd->inflight);
> +
> kfree(tv_cmd);
> }
>
> @@ -595,6 +656,9 @@ static struct tcm_vhost_cmd *vhost_scsi_allocate_cmd(
> tv_cmd->tvc_data_direction = data_direction;
> tv_cmd->tvc_nexus = tv_nexus;
> tv_cmd->tvc_vhost = vs;
> + tv_cmd->inflight = tcm_vhost_inc_inflight(vs);
> + if (!tv_cmd->inflight)
> + return ERR_PTR(-ENOMEM);
>
> return tv_cmd;
> }
> @@ -982,12 +1046,35 @@ static void vhost_scsi_flush_vq(struct vhost_scsi *vs, int index)
>
> static void vhost_scsi_flush(struct vhost_scsi *vs)
> {
> + struct vhost_scsi_inflight *inflight;
> int i;
>
> + /* inflight points to the old inflight */
> + inflight = rcu_dereference_protected(vs->vs_inflight,
> + lockdep_is_held(&vs->dev.mutex));
> +
> + /* Allocate a new inflight and make vs->vs_inflight points to it */
> + if (tcm_vhost_set_inflight(vs) < 0)
> + pr_warn("vhost_scsi_flush failed to allocate inflight\n");
That's unlikely to reach the application. How about we stop here,
and propagate the error to ioctl caller?
> +
> + /*
> + * The inflight->kref was initialized to 1. We decrement it here to
> + * indicate the start of the flush operation so that it will reach 0
> + * when all the reqs are finished.
> + */
> + kref_put(&inflight->kref, tcm_vhost_done_inflight);
> +
> + /* Flush both the vhost poll and vhost work */
> 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 for all reqs issued before the flush to be finished */
> + if (inflight) {
inflight should never be NULL, otherwise inflight
tracjing is not effective. Please fix error handling so we
never reach here with inflight == NULL.
> + wait_for_completion(&inflight->comp);
> + kfree(inflight);
> + }
> }
>
> /*
> @@ -1196,6 +1283,9 @@ static int vhost_scsi_open(struct inode *inode, struct file *f)
> s->vs_events_dropped = false;
> mutex_init(&s->vs_events_lock);
>
> + if (tcm_vhost_set_inflight(s) < 0)
> + return -ENOMEM;
> +
Better propagate the return code to user.
> 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++)
> @@ -1221,6 +1311,7 @@ static int vhost_scsi_release(struct inode *inode, struct file *f)
> vhost_scsi_clear_endpoint(s, &t);
> vhost_dev_stop(&s->dev);
> vhost_dev_cleanup(&s->dev, false);
> + kfree(s->vs_inflight);
> kfree(s);
> return 0;
> }
> diff --git a/drivers/vhost/tcm_vhost.h b/drivers/vhost/tcm_vhost.h
> index 94e9ee53..7567767 100644
> --- a/drivers/vhost/tcm_vhost.h
> +++ b/drivers/vhost/tcm_vhost.h
> @@ -2,6 +2,7 @@
> #define TCM_VHOST_NAMELEN 256
> #define TCM_VHOST_MAX_CDB_SIZE 32
>
> +struct vhost_scsi_inflight;
> struct tcm_vhost_cmd {
> /* Descriptor from vhost_get_vq_desc() for virt_queue segment */
> int tvc_vq_desc;
> @@ -37,6 +38,8 @@ 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;
> + /* Used to track inflight req */
> + struct vhost_scsi_inflight *inflight;
> };
>
> struct tcm_vhost_nexus {
> @@ -91,6 +94,8 @@ struct tcm_vhost_evt {
> struct virtio_scsi_event event;
> /* virtio_scsi event list, serviced from vhost worker thread */
> struct llist_node list;
> + /* Used to track inflight req */
> + struct vhost_scsi_inflight *inflight;
> };
>
> /*
> --
> 1.8.1.4
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