[PATCH 4.4 4/9] net/ncsi: Rework request index allocation

[Gavin Shan]

The NCSI request index (struct ncsi_req::nr_id) is put into instance
ID (IID) field while sending NCSI command packet. It was designed the
available IDs are given in round-robin fashion. @ndp->request_id was
introduced to represent the next available ID, but it has been used
as number of successively allocated IDs. It breaks the round-robin
design. Besides, we shouldn't put 0 to NCSI command packet's IID
field, meaning ID#0 should be reserved according section 6.3.1.1
in NCSI spec (v1.1.0).

This fixes above two issues. With it applied, the available IDs will
be assigned in round-robin fashion and ID#0 won't be assigned.

Signed-off-by: Gavin Shan <gwshan at linux.vnet.ibm.com>
Reviewed-by: Joel Stanley <joel at jms.id.au>
---
 net/ncsi/internal.h    |  1 +
 net/ncsi/ncsi-manage.c | 23 +++++++++++------------
 2 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/net/ncsi/internal.h b/net/ncsi/internal.h
index 339177a..212d77b 100644
--- a/net/ncsi/internal.h
+++ b/net/ncsi/internal.h
@@ -87,6 +87,7 @@ struct ncsi_dev_priv {
 	struct list_head	ndp_packages;
 	atomic_t		ndp_pending_reqs;
 	atomic_t		ndp_last_req_idx;
+#define NCSI_REQ_START_IDX	1
 	spinlock_t		ndp_req_lock;
 	struct ncsi_req		ndp_reqs[256];
 	struct work_struct	ndp_work;
diff --git a/net/ncsi/ncsi-manage.c b/net/ncsi/ncsi-manage.c
index b728614..44a740f 100644
--- a/net/ncsi/ncsi-manage.c
+++ b/net/ncsi/ncsi-manage.c
@@ -306,30 +306,29 @@ struct ncsi_req *ncsi_alloc_req(struct ncsi_dev_priv *ndp)
 	spin_lock_irqsave(&ndp->ndp_req_lock, flags);
 
 	/* Check if there is one available request until the ceiling */
-	for (idx = atomic_read(&ndp->ndp_last_req_idx);
-	     !nr && idx < limit; idx++) {
+	for (idx = atomic_read(&ndp->ndp_last_req_idx); idx < limit; idx++) {
 		if (ndp->ndp_reqs[idx].nr_used)
 			continue;
 
-		ndp->ndp_reqs[idx].nr_used = true;
 		nr = &ndp->ndp_reqs[idx];
-		atomic_inc(&ndp->ndp_last_req_idx);
-		if (atomic_read(&ndp->ndp_last_req_idx) >= limit)
-			atomic_set(&ndp->ndp_last_req_idx, 0);
+		nr->nr_used = true;
+		atomic_set(&ndp->ndp_last_req_idx, idx + 1);
+		goto found;
 	}
 
 	/* Fail back to check from the starting cursor */
-	for (idx = 0; !nr && idx < atomic_read(&ndp->ndp_last_req_idx); idx++) {
+	for (idx = NCSI_REQ_START_IDX;
+	     idx < atomic_read(&ndp->ndp_last_req_idx); idx++) {
 		if (ndp->ndp_reqs[idx].nr_used)
 			continue;
 
-		ndp->ndp_reqs[idx].nr_used = true;
 		nr = &ndp->ndp_reqs[idx];
-		atomic_inc(&ndp->ndp_last_req_idx);
-		if (atomic_read(&ndp->ndp_last_req_idx) >= limit)
-			atomic_set(&ndp->ndp_last_req_idx, 0);
+		nr->nr_used = true;
+		atomic_set(&ndp->ndp_last_req_idx, idx + 1);
+		goto found;
 	}
 
+found:
 	spin_unlock_irqrestore(&ndp->ndp_req_lock, flags);
 	return nr;
 }
@@ -834,7 +833,7 @@ struct ncsi_dev *ncsi_register_dev(struct net_device *dev,
 	INIT_LIST_HEAD(&ndp->ndp_packages);
 	INIT_WORK(&ndp->ndp_work, ncsi_dev_work);
 	spin_lock_init(&ndp->ndp_req_lock);
-	atomic_set(&ndp->ndp_last_req_idx, 0);
+	atomic_set(&ndp->ndp_last_req_idx, NCSI_REQ_START_IDX);
 	for (idx = 0; idx < 256; idx++) {
 		ndp->ndp_reqs[idx].nr_id = idx;
 		ndp->ndp_reqs[idx].nr_ndp = ndp;
-- 
2.1.0