IB/srp: Fix srp_map_sg_fr()

After dma_map_sg() has been called the return value of that function
must be used as the number of elements in the scatterlist instead of
scsi_sg_count().

Fixes: commit f7f7aab1 ("IB/srp: Convert to new registration API")
Reported-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Cc: stable <stable@vger.kernel.org> # v4.4+
Cc: Sagi Grimberg <sagig@mellanox.com>
Cc: Sebastian Parschauer <sebastian.riemer@profitbricks.com>
Reviewed-by: Sagi Grimberg <sagig@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

drivers/infiniband/ulp/srp/ib_srp.c

@@ -1313,7 +1313,7 @@ static int srp_map_finish_fmr(struct srp_map_state *state,
 }
 
 static int srp_map_finish_fr(struct srp_map_state *state,
-			     struct srp_rdma_ch *ch)
+			     struct srp_rdma_ch *ch, int sg_nents)
 {
 	struct srp_target_port *target = ch->target;
 	struct srp_device *dev = target->srp_host->srp_dev;
@@ -1328,10 +1328,10 @@ static int srp_map_finish_fr(struct srp_map_state *state,
 
 	WARN_ON_ONCE(!dev->use_fast_reg);
 
-	if (state->sg_nents == 0)
+	if (sg_nents == 0)
 		return 0;
 
-	if (state->sg_nents == 1 && target->global_mr) {
+	if (sg_nents == 1 && target->global_mr) {
 		srp_map_desc(state, sg_dma_address(state->sg),
 			     sg_dma_len(state->sg),
 			     target->global_mr->rkey);
@@ -1345,8 +1345,7 @@ static int srp_map_finish_fr(struct srp_map_state *state,
 	rkey = ib_inc_rkey(desc->mr->rkey);
 	ib_update_fast_reg_key(desc->mr, rkey);
 
-	n = ib_map_mr_sg(desc->mr, state->sg, state->sg_nents,
-			 dev->mr_page_size);
+	n = ib_map_mr_sg(desc->mr, state->sg, sg_nents, dev->mr_page_size);
 	if (unlikely(n < 0))
 		return n;
 
@@ -1452,16 +1451,15 @@ static int srp_map_sg_fr(struct srp_map_state *state, struct srp_rdma_ch *ch,
 	state->fr.next = req->fr_list;
 	state->fr.end = req->fr_list + ch->target->cmd_sg_cnt;
 	state->sg = scat;
-	state->sg_nents = scsi_sg_count(req->scmnd);
 
-	while (state->sg_nents) {
+	while (count) {
 		int i, n;
 
-		n = srp_map_finish_fr(state, ch);
+		n = srp_map_finish_fr(state, ch, count);
 		if (unlikely(n < 0))
 			return n;
 
-		state->sg_nents -= n;
+		count -= n;
 		for (i = 0; i < n; i++)
 			state->sg = sg_next(state->sg);
 	}
@@ -1521,13 +1519,12 @@ static int srp_map_idb(struct srp_rdma_ch *ch, struct srp_request *req,
 
 	if (dev->use_fast_reg) {
 		state.sg = idb_sg;
-		state.sg_nents = 1;
 		sg_set_buf(idb_sg, req->indirect_desc, idb_len);
 		idb_sg->dma_address = req->indirect_dma_addr; /* hack! */
 #ifdef CONFIG_NEED_SG_DMA_LENGTH
 		idb_sg->dma_length = idb_sg->length;	      /* hack^2 */
 #endif
-		ret = srp_map_finish_fr(&state, ch);
+		ret = srp_map_finish_fr(&state, ch, 1);
 		if (ret < 0)
 			return ret;
 	} else if (dev->use_fmr) {

drivers/infiniband/ulp/srp/ib_srp.h

@@ -300,10 +300,7 @@ struct srp_map_state {
 	dma_addr_t		base_dma_addr;
 	u32			dma_len;
 	u32			total_len;
-	union {
 	unsigned int		npages;
-		int		sg_nents;
-	};
 	unsigned int		nmdesc;
 	unsigned int		ndesc;
 };