RDS: Assume recv->r_frag is always NULL in refill_one()

refill_one() should never be called on a recv struct that
doesn't need a new r_frag allocated. Add a WARN and remove
conditional around r_frag alloc code.

Also, add a comment to explain why r_ibinc may or may not
need refilling.

Signed-off-by: Andy Grover <andy.grover@oracle.com>

1 files changed, 16 insertions, 13 deletions

diff --git a/net/rds/ib_recv.c b/net/rds/ib_recv.c
index f6dbf16e0741..5c7e6acf7c60 100644
--- a/net/rds/ib_recv.c
+++ b/net/rds/ib_recv.c
@@ -126,6 +126,10 @@ static int rds_ib_recv_refill_one(struct rds_connection *conn,
         struct ib_sge *sge;
         int ret = -ENOMEM;
 
+        /*
+         * ibinc was taken from recv if recv contained the start of a message.
+         * recvs that were continuations will still have this allocated.
+         */
         if (!recv->r_ibinc) {
                 if (!atomic_add_unless(&rds_ib_allocation, 1, rds_ib_sysctl_max_recv_allocation)) {
                         rds_ib_stats_inc(s_ib_rx_alloc_limit);
@@ -140,19 +144,18 @@ static int rds_ib_recv_refill_one(struct rds_connection *conn,
                 rds_inc_init(&recv->r_ibinc->ii_inc, conn, conn->c_faddr);
         }
 
-        if (!recv->r_frag) {
-                recv->r_frag = kmem_cache_alloc(rds_ib_frag_slab, GFP_NOWAIT);
-                if (!recv->r_frag)
-                        goto out;
-                INIT_LIST_HEAD(&recv->r_frag->f_item);
-                sg_init_table(&recv->r_frag->f_sg, 1);
-                ret = rds_page_remainder_alloc(&recv->r_frag->f_sg,
-                                               RDS_FRAG_SIZE, GFP_NOWAIT);
-                if (ret) {
-                        kmem_cache_free(rds_ib_frag_slab, recv->r_frag);
-                        recv->r_frag = NULL;
-                        goto out;
-                }
+        WARN_ON(recv->r_frag); /* leak! */
+        recv->r_frag = kmem_cache_alloc(rds_ib_frag_slab, GFP_NOWAIT);
+        if (!recv->r_frag)
+                goto out;
+        INIT_LIST_HEAD(&recv->r_frag->f_item);
+        sg_init_table(&recv->r_frag->f_sg, 1);
+        ret = rds_page_remainder_alloc(&recv->r_frag->f_sg,
+                                       RDS_FRAG_SIZE, GFP_NOWAIT);
+        if (ret) {
+                kmem_cache_free(rds_ib_frag_slab, recv->r_frag);
+                recv->r_frag = NULL;
+                goto out;
         }
 
         ret = ib_dma_map_sg(ic->i_cm_id->device, &recv->r_frag->f_sg,