IB/srpt: Make it safe to use RCU for srpt_device.rch_list

The next patch will iterate over rch_list from a context from which
it is not allowed to block. Hence make rch_list RCU-safe.

Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

diff --git a/drivers/infiniband/ulp/srpt/ib_srpt.c b/drivers/infiniband/ulp/srpt/ib_srpt.c
index d78f60d..4dd1537 100644 (file)
--- a/drivers/infiniband/ulp/srpt/ib_srpt.c
+++ b/drivers/infiniband/ulp/srpt/ib_srpt.c
@@ -1906,7 +1906,7 @@ static void srpt_free_ch(struct kref *kref)
 {
        struct srpt_rdma_ch *ch = container_of(kref, struct srpt_rdma_ch, kref);
 
-       kfree(ch);
+       kfree_rcu(ch, rcu);
 }
 
 static void srpt_release_channel_work(struct work_struct *w)
@@ -1945,11 +1945,17 @@ static void srpt_release_channel_work(struct work_struct *w)
                             srp_max_req_size, DMA_FROM_DEVICE);
 
        mutex_lock(&sdev->mutex);
-       list_del_init(&ch->list);
+       list_del_rcu(&ch->list);
        if (ch->release_done)
                complete(ch->release_done);
        mutex_unlock(&sdev->mutex);
 
+       synchronize_rcu();
+
+       mutex_lock(&sdev->mutex);
+       INIT_LIST_HEAD(&ch->list);
+       mutex_unlock(&sdev->mutex);
+
        wake_up(&sdev->ch_releaseQ);
 
        kref_put(&ch->kref, srpt_free_ch);
@@ -2064,6 +2070,7 @@ static int srpt_cm_req_recv(struct ib_cm_id *cm_id,
                goto reject;
        }
 
+       init_rcu_head(&ch->rcu);
        kref_init(&ch->kref);
        ch->zw_cqe.done = srpt_zerolength_write_done;
        INIT_WORK(&ch->release_work, srpt_release_channel_work);
@@ -2190,7 +2197,7 @@ static int srpt_cm_req_recv(struct ib_cm_id *cm_id,
        }
 
        mutex_lock(&sdev->mutex);
-       list_add_tail(&ch->list, &sdev->rch_list);
+       list_add_tail_rcu(&ch->list, &sdev->rch_list);
        mutex_unlock(&sdev->mutex);
 
        goto out;

diff --git a/drivers/infiniband/ulp/srpt/ib_srpt.h b/drivers/infiniband/ulp/srpt/ib_srpt.h
index 11ce8c9..0ab59c6 100644 (file)
--- a/drivers/infiniband/ulp/srpt/ib_srpt.h
+++ b/drivers/infiniband/ulp/srpt/ib_srpt.h
@@ -244,6 +244,7 @@ enum rdma_ch_state {
  * @qp:            IB queue pair used for communicating over this channel.
  * @cq:            IB completion queue for this channel.
  * @zw_cqe:       Zero-length write CQE.
+ * @rcu:           RCU head.
  * @kref:         kref for this channel.
  * @rq_size:       IB receive queue size.
  * @max_rsp_size:  Maximum size of an RSP response message in bytes.
@@ -276,6 +277,7 @@ struct srpt_rdma_ch {
        struct ib_qp            *qp;
        struct ib_cq            *cq;
        struct ib_cqe           zw_cqe;
+       struct rcu_head         rcu;
        struct kref             kref;
        int                     rq_size;
        u32                     max_rsp_size;