IB/srpt: Use a mutex to protect the channel list

In a later patch a function that can block will be called while
iterating over the rch_list. Hence protect that list with a
mutex instead of a spinlock. And since it is not allowed to sleep
while the task state != TASK_RUNNING, convert the list test in
srpt_ch_list_empty() into a lockless test.

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Sagi Grimberg <sagig@mellanox.com>
Cc: Alex Estrin <alex.estrin@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

2 files changed, 17 insertions, 29 deletions

diff --git a/drivers/infiniband/ulp/srpt/ib_srpt.c b/drivers/infiniband/ulp/srpt/ib_srpt.c
index 0bf204ec443e..33bd408c5eea 100644
--- a/drivers/infiniband/ulp/srpt/ib_srpt.c
+++ b/drivers/infiniband/ulp/srpt/ib_srpt.c
@@ -1862,12 +1862,11 @@ static void __srpt_close_ch(struct srpt_rdma_ch *ch)
  */
 static void srpt_close_ch(struct srpt_rdma_ch *ch)
 {
-        struct srpt_device *sdev;
+        struct srpt_device *sdev = ch->sport->sdev;
 
-        sdev = ch->sport->sdev;
-        spin_lock_irq(&sdev->spinlock);
+        mutex_lock(&sdev->mutex);
         __srpt_close_ch(ch);
-        spin_unlock_irq(&sdev->spinlock);
+        mutex_unlock(&sdev->mutex);
 }
 
 /**
@@ -1954,11 +1953,11 @@ static void srpt_release_channel_work(struct work_struct *w)
                              ch->sport->sdev, ch->rq_size,
                              ch->rsp_size, DMA_TO_DEVICE);
 
-        spin_lock_irq(&sdev->spinlock);
+        mutex_lock(&sdev->mutex);
         list_del_init(&ch->list);
         if (ch->release_done)
                 complete(ch->release_done);
-        spin_unlock_irq(&sdev->spinlock);
+        mutex_unlock(&sdev->mutex);
 
         wake_up(&sdev->ch_releaseQ);
 
@@ -2039,7 +2038,7 @@ static int srpt_cm_req_recv(struct ib_cm_id *cm_id,
         if ((req->req_flags & SRP_MTCH_ACTION) == SRP_MULTICHAN_SINGLE) {
                 rsp->rsp_flags = SRP_LOGIN_RSP_MULTICHAN_NO_CHAN;
 
-                spin_lock_irq(&sdev->spinlock);
+                mutex_lock(&sdev->mutex);
 
                 list_for_each_entry_safe(ch, tmp_ch, &sdev->rch_list, list) {
                         if (!memcmp(ch->i_port_id, req->initiator_port_id, 16)
@@ -2063,7 +2062,7 @@ static int srpt_cm_req_recv(struct ib_cm_id *cm_id,
                         }
                 }
 
-                spin_unlock_irq(&sdev->spinlock);
+                mutex_unlock(&sdev->mutex);
 
         } else
                 rsp->rsp_flags = SRP_LOGIN_RSP_MULTICHAN_MAINTAINED;
@@ -2208,9 +2207,9 @@ try_again:
                 goto release_channel;
         }
 
-        spin_lock_irq(&sdev->spinlock);
+        mutex_lock(&sdev->mutex);
         list_add_tail(&ch->list, &sdev->rch_list);
-        spin_unlock_irq(&sdev->spinlock);
+        mutex_unlock(&sdev->mutex);
 
         goto out;
 
@@ -2653,17 +2652,6 @@ static void srpt_refresh_port_work(struct work_struct *work)
         srpt_refresh_port(sport);
 }
 
-static int srpt_ch_list_empty(struct srpt_device *sdev)
-{
-        int res;
-
-        spin_lock_irq(&sdev->spinlock);
-        res = list_empty(&sdev->rch_list);
-        spin_unlock_irq(&sdev->spinlock);
-
-        return res;
-}
-
 /**
  * srpt_release_sdev() - Free the channel resources associated with a target.
  */
@@ -2676,13 +2664,13 @@ static int srpt_release_sdev(struct srpt_device *sdev)
 
         BUG_ON(!sdev);
 
-        spin_lock_irq(&sdev->spinlock);
+        mutex_lock(&sdev->mutex);
         list_for_each_entry_safe(ch, tmp_ch, &sdev->rch_list, list)
                 __srpt_close_ch(ch);
-        spin_unlock_irq(&sdev->spinlock);
+        mutex_unlock(&sdev->mutex);
 
         res = wait_event_interruptible(sdev->ch_releaseQ,
-                                       srpt_ch_list_empty(sdev));
+                                       list_empty_careful(&sdev->rch_list));
         if (res)
                 pr_err("%s: interrupted.\n", __func__);
 
@@ -2743,7 +2731,7 @@ static void srpt_add_one(struct ib_device *device)
         sdev->device = device;
         INIT_LIST_HEAD(&sdev->rch_list);
         init_waitqueue_head(&sdev->ch_releaseQ);
-        spin_lock_init(&sdev->spinlock);
+        mutex_init(&sdev->mutex);
 
         sdev->pd = ib_alloc_pd(device);
         if (IS_ERR(sdev->pd))
@@ -2971,12 +2959,12 @@ static void srpt_close_session(struct se_session *se_sess)
         pr_debug("ch %s-%d state %d\n", ch->sess_name, ch->qp->qp_num,
                  ch->state);
 
-        spin_lock_irq(&sdev->spinlock);
+        mutex_lock(&sdev->mutex);
         BUG_ON(ch->release_done);
         ch->release_done = &release_done;
         wait = !list_empty(&ch->list);
         __srpt_close_ch(ch);
-        spin_unlock_irq(&sdev->spinlock);
+        mutex_unlock(&sdev->mutex);
 
         if (!wait)
                 return;
diff --git a/drivers/infiniband/ulp/srpt/ib_srpt.h b/drivers/infiniband/ulp/srpt/ib_srpt.h
index 9c326c71607c..5883295a7b97 100644
--- a/drivers/infiniband/ulp/srpt/ib_srpt.h
+++ b/drivers/infiniband/ulp/srpt/ib_srpt.h
@@ -342,7 +342,7 @@ struct srpt_port {
  * @ioctx_ring:    Per-HCA SRQ.
  * @rch_list:      Per-device channel list -- see also srpt_rdma_ch.list.
  * @ch_releaseQ:   Enables waiting for removal from rch_list.
- * @spinlock:      Protects rch_list and tpg.
+ * @mutex:         Protects rch_list.
  * @port:          Information about the ports owned by this HCA.
  * @event_handler: Per-HCA asynchronous IB event handler.
  * @list:          Node in srpt_dev_list.
@@ -356,7 +356,7 @@ struct srpt_device {
         struct srpt_recv_ioctx  **ioctx_ring;
         struct list_head        rch_list;
         wait_queue_head_t       ch_releaseQ;
-        spinlock_t              spinlock;
+        struct mutex            mutex;
         struct srpt_port        port[2];
         struct ib_event_handler event_handler;
         struct list_head        list;