[PATCH] IB: allow NULL sa_query callbacks

Check if a client passes a NULL callback into an SA query, and if so, never
call back.  This fixes an oops if someone unloads ib_ipoib and ib_sa in
rapid succession.  ib_ipoib does an MCMember delete with a NULL callback
and 0 timeout on unload, which is usually fine since the delete completes
successfully.  However, if ib_sa is unloaded immediately afterwards, the
delete will be canceled and ib_sa will try to call the (now already
unloaded) ib_ipoib module back with the cancel completion, which triggers
the oops.

Signed-off-by: Roland Dreier <roland@topspin.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 18 insertions, 17 deletions

diff --git a/drivers/infiniband/core/sa_query.c b/drivers/infiniband/core/sa_query.c
index d4233ee61c35..276e1a53010d 100644
--- a/drivers/infiniband/core/sa_query.c
+++ b/drivers/infiniband/core/sa_query.c
@@ -587,7 +587,7 @@ int ib_sa_path_rec_get(struct ib_device *device, u8 port_num,
 
         init_mad(query->sa_query.mad, agent);
 
-        query->sa_query.callback              = ib_sa_path_rec_callback;
+        query->sa_query.callback              = callback ? ib_sa_path_rec_callback : NULL;
         query->sa_query.release               = ib_sa_path_rec_release;
         query->sa_query.port                  = port;
         query->sa_query.mad->mad_hdr.method   = IB_MGMT_METHOD_GET;
@@ -663,7 +663,7 @@ int ib_sa_mcmember_rec_query(struct ib_device *device, u8 port_num,
 
         init_mad(query->sa_query.mad, agent);
 
-        query->sa_query.callback              = ib_sa_mcmember_rec_callback;
+        query->sa_query.callback              = callback ? ib_sa_mcmember_rec_callback : NULL;
         query->sa_query.release               = ib_sa_mcmember_rec_release;
         query->sa_query.port                  = port;
         query->sa_query.mad->mad_hdr.method   = method;
@@ -698,20 +698,21 @@ static void send_handler(struct ib_mad_agent *agent,
         if (!query)
                 return;
 
-        switch (mad_send_wc->status) {
-        case IB_WC_SUCCESS:
-                /* No callback -- already got recv */
-                break;
-        case IB_WC_RESP_TIMEOUT_ERR:
-                query->callback(query, -ETIMEDOUT, NULL);
-                break;
-        case IB_WC_WR_FLUSH_ERR:
-                query->callback(query, -EINTR, NULL);
-                break;
-        default:
-                query->callback(query, -EIO, NULL);
-                break;
-        }
+        if (query->callback)
+                switch (mad_send_wc->status) {
+                case IB_WC_SUCCESS:
+                        /* No callback -- already got recv */
+                        break;
+                case IB_WC_RESP_TIMEOUT_ERR:
+                        query->callback(query, -ETIMEDOUT, NULL);
+                        break;
+                case IB_WC_WR_FLUSH_ERR:
+                        query->callback(query, -EINTR, NULL);
+                        break;
+                default:
+                        query->callback(query, -EIO, NULL);
+                        break;
+                }
 
         dma_unmap_single(agent->device->dma_device,
                          pci_unmap_addr(query, mapping),
@@ -736,7 +737,7 @@ static void recv_handler(struct ib_mad_agent *mad_agent,
         query = idr_find(&query_idr, mad_recv_wc->wc->wr_id);
         spin_unlock_irqrestore(&idr_lock, flags);
 
-        if (query) {
+        if (query && query->callback) {
                 if (mad_recv_wc->wc->status == IB_WC_SUCCESS)
                         query->callback(query,
                                         mad_recv_wc->recv_buf.mad->mad_hdr.status ?