IB/srp: Implement SRP_CRED_REQ and SRP_AER_REQ
This patch adds support for SRP_CRED_REQ to avoid a lockup by targets
that use that mechanism to return credits to the initiator. This
prevents a lockup observed in the field where we would never add the
credits from the SRP_CRED_REQ to our current count, and would therefore
never send another command to the target.
Minimal support for SRP_AER_REQ is also added, as these messages can
also be used to convey additional credits to the initiator.
Based upon extensive debugging and code by Bart Van Assche and a bug
report by Chris Worley.
Signed-off-by: David Dillow <dillowda@ornl.gov>
Signed-off-by: Roland Dreier <rolandd@cisco.com>
diff --git a/drivers/infiniband/ulp/srp/ib_srp.c b/drivers/infiniband/ulp/srp/ib_srp.c
index b8b09a4..a54eee9 100644
--- a/drivers/infiniband/ulp/srp/ib_srp.c
+++ b/drivers/infiniband/ulp/srp/ib_srp.c
@@ -83,6 +83,10 @@
static void srp_recv_completion(struct ib_cq *cq, void *target_ptr);
static void srp_send_completion(struct ib_cq *cq, void *target_ptr);
static int srp_cm_handler(struct ib_cm_id *cm_id, struct ib_cm_event *event);
+static struct srp_iu *__srp_get_tx_iu(struct srp_target_port *target,
+ enum srp_iu_type iu_type);
+static int __srp_post_send(struct srp_target_port *target,
+ struct srp_iu *iu, int len);
static struct scsi_transport_template *ib_srp_transport_template;
@@ -896,6 +900,71 @@
spin_unlock_irqrestore(target->scsi_host->host_lock, flags);
}
+static int srp_response_common(struct srp_target_port *target, s32 req_delta,
+ void *rsp, int len)
+{
+ struct ib_device *dev;
+ unsigned long flags;
+ struct srp_iu *iu;
+ int err = 1;
+
+ dev = target->srp_host->srp_dev->dev;
+
+ spin_lock_irqsave(target->scsi_host->host_lock, flags);
+ target->req_lim += req_delta;
+
+ iu = __srp_get_tx_iu(target, SRP_IU_RSP);
+ if (!iu) {
+ shost_printk(KERN_ERR, target->scsi_host, PFX
+ "no IU available to send response\n");
+ goto out;
+ }
+
+ ib_dma_sync_single_for_cpu(dev, iu->dma, len, DMA_TO_DEVICE);
+ memcpy(iu->buf, rsp, len);
+ ib_dma_sync_single_for_device(dev, iu->dma, len, DMA_TO_DEVICE);
+
+ err = __srp_post_send(target, iu, len);
+ if (err)
+ shost_printk(KERN_ERR, target->scsi_host, PFX
+ "unable to post response: %d\n", err);
+
+out:
+ spin_unlock_irqrestore(target->scsi_host->host_lock, flags);
+ return err;
+}
+
+static void srp_process_cred_req(struct srp_target_port *target,
+ struct srp_cred_req *req)
+{
+ struct srp_cred_rsp rsp = {
+ .opcode = SRP_CRED_RSP,
+ .tag = req->tag,
+ };
+ s32 delta = be32_to_cpu(req->req_lim_delta);
+
+ if (srp_response_common(target, delta, &rsp, sizeof rsp))
+ shost_printk(KERN_ERR, target->scsi_host, PFX
+ "problems processing SRP_CRED_REQ\n");
+}
+
+static void srp_process_aer_req(struct srp_target_port *target,
+ struct srp_aer_req *req)
+{
+ struct srp_aer_rsp rsp = {
+ .opcode = SRP_AER_RSP,
+ .tag = req->tag,
+ };
+ s32 delta = be32_to_cpu(req->req_lim_delta);
+
+ shost_printk(KERN_ERR, target->scsi_host, PFX
+ "ignoring AER for LUN %llu\n", be64_to_cpu(req->lun));
+
+ if (srp_response_common(target, delta, &rsp, sizeof rsp))
+ shost_printk(KERN_ERR, target->scsi_host, PFX
+ "problems processing SRP_AER_REQ\n");
+}
+
static void srp_handle_recv(struct srp_target_port *target, struct ib_wc *wc)
{
struct ib_device *dev;
@@ -923,6 +992,14 @@
srp_process_rsp(target, iu->buf);
break;
+ case SRP_CRED_REQ:
+ srp_process_cred_req(target, iu->buf);
+ break;
+
+ case SRP_AER_REQ:
+ srp_process_aer_req(target, iu->buf);
+ break;
+
case SRP_T_LOGOUT:
/* XXX Handle target logout */
shost_printk(KERN_WARNING, target->scsi_host,
@@ -985,23 +1062,36 @@
* Must be called with target->scsi_host->host_lock held to protect
* req_lim and tx_head. Lock cannot be dropped between call here and
* call to __srp_post_send().
+ *
+ * Note:
+ * An upper limit for the number of allocated information units for each
+ * request type is:
+ * - SRP_IU_CMD: SRP_CMD_SQ_SIZE, since the SCSI mid-layer never queues
+ * more than Scsi_Host.can_queue requests.
+ * - SRP_IU_TSK_MGMT: SRP_TSK_MGMT_SQ_SIZE.
+ * - SRP_IU_RSP: 1, since a conforming SRP target never sends more than
+ * one unanswered SRP request to an initiator.
*/
static struct srp_iu *__srp_get_tx_iu(struct srp_target_port *target,
- enum srp_request_type req_type)
+ enum srp_iu_type iu_type)
{
- s32 rsv = (req_type == SRP_REQ_TASK_MGMT) ? 0 : SRP_TSK_MGMT_SQ_SIZE;
+ s32 rsv = (iu_type == SRP_IU_TSK_MGMT) ? 0 : SRP_TSK_MGMT_SQ_SIZE;
+ struct srp_iu *iu;
srp_send_completion(target->send_cq, target);
if (target->tx_head - target->tx_tail >= SRP_SQ_SIZE)
return NULL;
- if (target->req_lim <= rsv) {
+ /* Initiator responses to target requests do not consume credits */
+ if (target->req_lim <= rsv && iu_type != SRP_IU_RSP) {
++target->zero_req_lim;
return NULL;
}
- return target->tx_ring[target->tx_head & SRP_SQ_MASK];
+ iu = target->tx_ring[target->tx_head & SRP_SQ_MASK];
+ iu->type = iu_type;
+ return iu;
}
/*
@@ -1030,7 +1120,8 @@
if (!ret) {
++target->tx_head;
- --target->req_lim;
+ if (iu->type != SRP_IU_RSP)
+ --target->req_lim;
}
return ret;
@@ -1056,7 +1147,7 @@
return 0;
}
- iu = __srp_get_tx_iu(target, SRP_REQ_NORMAL);
+ iu = __srp_get_tx_iu(target, SRP_IU_CMD);
if (!iu)
goto err;
@@ -1363,7 +1454,7 @@
init_completion(&req->done);
- iu = __srp_get_tx_iu(target, SRP_REQ_TASK_MGMT);
+ iu = __srp_get_tx_iu(target, SRP_IU_TSK_MGMT);
if (!iu)
goto out;
diff --git a/drivers/infiniband/ulp/srp/ib_srp.h b/drivers/infiniband/ulp/srp/ib_srp.h
index 7a959d5..ed0dce9 100644
--- a/drivers/infiniband/ulp/srp/ib_srp.h
+++ b/drivers/infiniband/ulp/srp/ib_srp.h
@@ -82,9 +82,10 @@
SRP_TARGET_REMOVED
};
-enum srp_request_type {
- SRP_REQ_NORMAL,
- SRP_REQ_TASK_MGMT,
+enum srp_iu_type {
+ SRP_IU_CMD,
+ SRP_IU_TSK_MGMT,
+ SRP_IU_RSP,
};
struct srp_device {
@@ -171,6 +172,7 @@
void *buf;
size_t size;
enum dma_data_direction direction;
+ enum srp_iu_type type;
};
#endif /* IB_SRP_H */