cxgb3 - Fix low memory conditions

Reuse the incoming skb when a clientless abort req is recieved.

The release of RDMA connections HW resources might be deferred in
low memory situations.
Ensure that no further activity is passed up to the RDMA driver
for these connections.
Signed-off-by: Divy Le Ray <divy@chelsio.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

drivers/net/cxgb3/cxgb3_defs.h

@@ -67,7 +67,10 @@ static inline union listen_entry *stid2entry(const struct tid_info *t,
 static inline struct t3c_tid_entry *lookup_tid(const struct tid_info *t,
 					       unsigned int tid)
 {
-	return tid < t->ntids ? &(t->tid_tab[tid]) : NULL;
+	struct t3c_tid_entry *t3c_tid = tid < t->ntids ?
+	    &(t->tid_tab[tid]) : NULL;
+
+	return (t3c_tid && t3c_tid->client) ? t3c_tid : NULL;
 }
 
 /*

drivers/net/cxgb3/cxgb3_offload.c

@@ -508,6 +508,7 @@ void cxgb3_queue_tid_release(struct t3cdev *tdev, unsigned int tid)
 
 	spin_lock_bh(&td->tid_release_lock);
 	p->ctx = (void *)td->tid_release_list;
+	p->client = NULL;
 	td->tid_release_list = p;
 	if (!p->ctx)
 		schedule_work(&td->tid_release_task);
@@ -623,7 +624,8 @@ static int do_act_open_rpl(struct t3cdev *dev, struct sk_buff *skb)
 	struct t3c_tid_entry *t3c_tid;
 
 	t3c_tid = lookup_atid(&(T3C_DATA(dev))->tid_maps, atid);
-	if (t3c_tid->ctx && t3c_tid->client && t3c_tid->client->handlers &&
+	if (t3c_tid && t3c_tid->ctx && t3c_tid->client &&
+	    t3c_tid->client->handlers &&
 	    t3c_tid->client->handlers[CPL_ACT_OPEN_RPL]) {
 		return t3c_tid->client->handlers[CPL_ACT_OPEN_RPL] (dev, skb,
 								    t3c_tid->
@@ -642,7 +644,7 @@ static int do_stid_rpl(struct t3cdev *dev, struct sk_buff *skb)
 	struct t3c_tid_entry *t3c_tid;
 
 	t3c_tid = lookup_stid(&(T3C_DATA(dev))->tid_maps, stid);
-	if (t3c_tid->ctx && t3c_tid->client->handlers &&
+	if (t3c_tid && t3c_tid->ctx && t3c_tid->client->handlers &&
 	    t3c_tid->client->handlers[p->opcode]) {
 		return t3c_tid->client->handlers[p->opcode] (dev, skb,
 							     t3c_tid->ctx);
@@ -660,7 +662,7 @@ static int do_hwtid_rpl(struct t3cdev *dev, struct sk_buff *skb)
 	struct t3c_tid_entry *t3c_tid;
 
 	t3c_tid = lookup_tid(&(T3C_DATA(dev))->tid_maps, hwtid);
-	if (t3c_tid->ctx && t3c_tid->client->handlers &&
+	if (t3c_tid && t3c_tid->ctx && t3c_tid->client->handlers &&
 	    t3c_tid->client->handlers[p->opcode]) {
 		return t3c_tid->client->handlers[p->opcode]
 		    (dev, skb, t3c_tid->ctx);
@@ -689,6 +691,28 @@ static int do_cr(struct t3cdev *dev, struct sk_buff *skb)
 	}
 }
 
+/*
+ * Returns an sk_buff for a reply CPL message of size len.  If the input
+ * sk_buff has no other users it is trimmed and reused, otherwise a new buffer
+ * is allocated.  The input skb must be of size at least len.  Note that this
+ * operation does not destroy the original skb data even if it decides to reuse
+ * the buffer.
+ */
+static struct sk_buff *cxgb3_get_cpl_reply_skb(struct sk_buff *skb, size_t len,
+					       int gfp)
+{
+	if (likely(!skb_cloned(skb))) {
+		BUG_ON(skb->len < len);
+		__skb_trim(skb, len);
+		skb_get(skb);
+	} else {
+		skb = alloc_skb(len, gfp);
+		if (skb)
+			__skb_put(skb, len);
+	}
+	return skb;
+}
+
 static int do_abort_req_rss(struct t3cdev *dev, struct sk_buff *skb)
 {
 	union opcode_tid *p = cplhdr(skb);
@@ -696,30 +720,39 @@ static int do_abort_req_rss(struct t3cdev *dev, struct sk_buff *skb)
 	struct t3c_tid_entry *t3c_tid;
 
 	t3c_tid = lookup_tid(&(T3C_DATA(dev))->tid_maps, hwtid);
-	if (t3c_tid->ctx && t3c_tid->client->handlers &&
+	if (t3c_tid && t3c_tid->ctx && t3c_tid->client->handlers &&
 	    t3c_tid->client->handlers[p->opcode]) {
 		return t3c_tid->client->handlers[p->opcode]
 		    (dev, skb, t3c_tid->ctx);
 	} else {
 		struct cpl_abort_req_rss *req = cplhdr(skb);
 		struct cpl_abort_rpl *rpl;
+		struct sk_buff *reply_skb;
+		unsigned int tid = GET_TID(req);
+		u8 cmd = req->status;
 
-		struct sk_buff *skb =
-		    alloc_skb(sizeof(struct cpl_abort_rpl), GFP_ATOMIC);
-		if (!skb) {
+		if (req->status == CPL_ERR_RTX_NEG_ADVICE ||
+		    req->status == CPL_ERR_PERSIST_NEG_ADVICE)
+			goto out;
+
+		reply_skb = cxgb3_get_cpl_reply_skb(skb,
+						    sizeof(struct
+							   cpl_abort_rpl),
+						    GFP_ATOMIC);
+
+		if (!reply_skb) {
 			printk("do_abort_req_rss: couldn't get skb!\n");
 			goto out;
 		}
-		skb->priority = CPL_PRIORITY_DATA;
-		__skb_put(skb, sizeof(struct cpl_abort_rpl));
-		rpl = cplhdr(skb);
+		reply_skb->priority = CPL_PRIORITY_DATA;
+		__skb_put(reply_skb, sizeof(struct cpl_abort_rpl));
+		rpl = cplhdr(reply_skb);
 		rpl->wr.wr_hi =
 		    htonl(V_WR_OP(FW_WROPCODE_OFLD_HOST_ABORT_CON_RPL));
-		rpl->wr.wr_lo = htonl(V_WR_TID(GET_TID(req)));
-		OPCODE_TID(rpl) =
-		    htonl(MK_OPCODE_TID(CPL_ABORT_RPL, GET_TID(req)));
-		rpl->cmd = req->status;
-		cxgb3_ofld_send(dev, skb);
+		rpl->wr.wr_lo = htonl(V_WR_TID(tid));
+		OPCODE_TID(rpl) = htonl(MK_OPCODE_TID(CPL_ABORT_RPL, tid));
+		rpl->cmd = cmd;
+		cxgb3_ofld_send(dev, reply_skb);
 out:
 		return CPL_RET_BUF_DONE;
 	}
@@ -732,7 +765,7 @@ static int do_act_establish(struct t3cdev *dev, struct sk_buff *skb)
 	struct t3c_tid_entry *t3c_tid;
 
 	t3c_tid = lookup_atid(&(T3C_DATA(dev))->tid_maps, atid);
-	if (t3c_tid->ctx && t3c_tid->client->handlers &&
+	if (t3c_tid && t3c_tid->ctx && t3c_tid->client->handlers &&
 	    t3c_tid->client->handlers[CPL_ACT_ESTABLISH]) {
 		return t3c_tid->client->handlers[CPL_ACT_ESTABLISH]
 		    (dev, skb, t3c_tid->ctx);
@@ -762,7 +795,7 @@ static int do_term(struct t3cdev *dev, struct sk_buff *skb)
 	struct t3c_tid_entry *t3c_tid;
 
 	t3c_tid = lookup_tid(&(T3C_DATA(dev))->tid_maps, hwtid);
-	if (t3c_tid->ctx && t3c_tid->client->handlers &&
+	if (t3c_tid && t3c_tid->ctx && t3c_tid->client->handlers &&
 	    t3c_tid->client->handlers[opcode]) {
 		return t3c_tid->client->handlers[opcode] (dev, skb,
 							  t3c_tid->ctx);
@@ -961,7 +994,7 @@ void cxgb_redirect(struct dst_entry *old, struct dst_entry *new)
 	for (tid = 0; tid < ti->ntids; tid++) {
 		te = lookup_tid(ti, tid);
 		BUG_ON(!te);
-		if (te->ctx && te->client && te->client->redirect) {
+		if (te && te->ctx && te->client && te->client->redirect) {
 			update_tcb = te->client->redirect(te->ctx, old, new, e);
 			if (update_tcb) {
 				l2t_hold(L2DATA(tdev), e);