svcrdma: Use standard Linux lists for context cache

Replace the one-off linked list implementation used to implement the
context cache with the standard Linux list_head lists. Add a context
counter to catch resource leaks. A WARN_ON will be added later to
ensure that we've freed all contexts.

Signed-off-by: Tom Tucker <tom@opengridcomputing.com>

2 files changed, 29 insertions, 23 deletions

diff --git a/include/linux/sunrpc/svc_rdma.h b/include/linux/sunrpc/svc_rdma.h
index c447c417b37b..701439064d21 100644
--- a/include/linux/sunrpc/svc_rdma.h
+++ b/include/linux/sunrpc/svc_rdma.h
@@ -72,7 +72,7 @@ extern atomic_t rdma_stat_sq_prod;
  */
 struct svc_rdma_op_ctxt {
         struct svc_rdma_op_ctxt *read_hdr;
-        struct svc_rdma_op_ctxt *next;
+        struct list_head free_list;
         struct xdr_buf arg;
         struct list_head dto_q;
         enum ib_wr_opcode wr_op;
@@ -104,7 +104,8 @@ struct svcxprt_rdma {
 
         struct ib_pd         *sc_pd;
 
-        struct svc_rdma_op_ctxt  *sc_ctxt_head;
+        atomic_t             sc_ctxt_used;
+        struct list_head     sc_ctxt_free;
         int                  sc_ctxt_cnt;
         int                  sc_ctxt_bump;
         int                  sc_ctxt_max;
diff --git a/net/sunrpc/xprtrdma/svc_rdma_transport.c b/net/sunrpc/xprtrdma/svc_rdma_transport.c
index 34141eaf25a0..817cf4de746c 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_transport.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_transport.c
@@ -103,8 +103,8 @@ static int rdma_bump_context_cache(struct svcxprt_rdma *xprt)
                 spin_lock_bh(&xprt->sc_ctxt_lock);
                 if (ctxt) {
                         at_least_one = 1;
-                        ctxt->next = xprt->sc_ctxt_head;
-                        xprt->sc_ctxt_head = ctxt;
+                        INIT_LIST_HEAD(&ctxt->free_list);
+                        list_add(&ctxt->free_list, &xprt->sc_ctxt_free);
                 } else {
                         /* kmalloc failed...give up for now */
                         xprt->sc_ctxt_cnt--;
@@ -123,7 +123,7 @@ struct svc_rdma_op_ctxt *svc_rdma_get_context(struct svcxprt_rdma *xprt)
 
         while (1) {
                 spin_lock_bh(&xprt->sc_ctxt_lock);
-                if (unlikely(xprt->sc_ctxt_head == NULL)) {
+                if (unlikely(list_empty(&xprt->sc_ctxt_free))) {
                         /* Try to bump my cache. */
                         spin_unlock_bh(&xprt->sc_ctxt_lock);
 
@@ -136,12 +136,15 @@ struct svc_rdma_op_ctxt *svc_rdma_get_context(struct svcxprt_rdma *xprt)
                         schedule_timeout_uninterruptible(msecs_to_jiffies(500));
                         continue;
                 }
-                ctxt = xprt->sc_ctxt_head;
-                xprt->sc_ctxt_head = ctxt->next;
+                ctxt = list_entry(xprt->sc_ctxt_free.next,
+                                  struct svc_rdma_op_ctxt,
+                                  free_list);
+                list_del_init(&ctxt->free_list);
                 spin_unlock_bh(&xprt->sc_ctxt_lock);
                 ctxt->xprt = xprt;
                 INIT_LIST_HEAD(&ctxt->dto_q);
                 ctxt->count = 0;
+                atomic_inc(&xprt->sc_ctxt_used);
                 break;
         }
         return ctxt;
@@ -163,10 +166,11 @@ void svc_rdma_put_context(struct svc_rdma_op_ctxt *ctxt, int free_pages)
                                  ctxt->sge[i].addr,
                                  ctxt->sge[i].length,
                                  ctxt->direction);
+
         spin_lock_bh(&xprt->sc_ctxt_lock);
-        ctxt->next = xprt->sc_ctxt_head;
-        xprt->sc_ctxt_head = ctxt;
+        list_add(&ctxt->free_list, &xprt->sc_ctxt_free);
         spin_unlock_bh(&xprt->sc_ctxt_lock);
+        atomic_dec(&xprt->sc_ctxt_used);
 }
 
 /* ib_cq event handler */
@@ -412,28 +416,29 @@ static void create_context_cache(struct svcxprt_rdma *xprt,
         xprt->sc_ctxt_max = ctxt_max;
         xprt->sc_ctxt_bump = ctxt_bump;
         xprt->sc_ctxt_cnt = 0;
-        xprt->sc_ctxt_head = NULL;
+        atomic_set(&xprt->sc_ctxt_used, 0);
+
+        INIT_LIST_HEAD(&xprt->sc_ctxt_free);
         for (i = 0; i < ctxt_count; i++) {
                 ctxt = kmalloc(sizeof(*ctxt), GFP_KERNEL);
                 if (ctxt) {
-                        ctxt->next = xprt->sc_ctxt_head;
-                        xprt->sc_ctxt_head = ctxt;
+                        INIT_LIST_HEAD(&ctxt->free_list);
+                        list_add(&ctxt->free_list, &xprt->sc_ctxt_free);
                         xprt->sc_ctxt_cnt++;
                 }
         }
 }
 
-static void destroy_context_cache(struct svc_rdma_op_ctxt *ctxt)
+static void destroy_context_cache(struct svcxprt_rdma *xprt)
 {
-        struct svc_rdma_op_ctxt *next;
-        if (!ctxt)
-                return;
-
-        do {
-                next = ctxt->next;
+        while (!list_empty(&xprt->sc_ctxt_free)) {
+                struct svc_rdma_op_ctxt *ctxt;
+                ctxt = list_entry(xprt->sc_ctxt_free.next,
+                                  struct svc_rdma_op_ctxt,
+                                  free_list);
+                list_del_init(&ctxt->free_list);
                 kfree(ctxt);
-                ctxt = next;
-        } while (next);
+        }
 }
 
 static struct svcxprt_rdma *rdma_create_xprt(struct svc_serv *serv,
@@ -470,7 +475,7 @@ static struct svcxprt_rdma *rdma_create_xprt(struct svc_serv *serv,
                                      reqs +
                                      cma_xprt->sc_sq_depth +
                                      RPCRDMA_MAX_THREADS + 1); /* max */
-                if (!cma_xprt->sc_ctxt_head) {
+                if (list_empty(&cma_xprt->sc_ctxt_free)) {
                         kfree(cma_xprt);
                         return NULL;
                 }
@@ -976,7 +981,7 @@ static void svc_rdma_free(struct svc_xprt *xprt)
         if (rdma->sc_pd && !IS_ERR(rdma->sc_pd))
                 ib_dealloc_pd(rdma->sc_pd);
 
-        destroy_context_cache(rdma->sc_ctxt_head);
+        destroy_context_cache(rdma);
         kfree(rdma);
 }