IB/srp: Use block layer tags

Since the block layer already contains functionality to assign
a tag to each request, use that functionality instead of
reimplementing that functionality in the SRP initiator driver.
This change makes the free_reqs list superfluous. Hence remove
that list.

[hch: updated to use .use_blk_tags instead scsi_activate_tcq]
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Sagi Grimberg <sagig@mellanox.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

2 files changed, 27 insertions, 24 deletions

diff --git a/drivers/infiniband/ulp/srp/ib_srp.c b/drivers/infiniband/ulp/srp/ib_srp.c
index f07a8a614738..42af59f3c8c6 100644
--- a/drivers/infiniband/ulp/srp/ib_srp.c
+++ b/drivers/infiniband/ulp/srp/ib_srp.c
@@ -821,8 +821,6 @@ static int srp_alloc_req_data(struct srp_rdma_ch *ch)
         dma_addr_t dma_addr;
         int i, ret = -ENOMEM;
 
-        INIT_LIST_HEAD(&ch->free_reqs);
-
         ch->req_ring = kcalloc(target->req_ring_size, sizeof(*ch->req_ring),
                                GFP_KERNEL);
         if (!ch->req_ring)
@@ -853,8 +851,6 @@ static int srp_alloc_req_data(struct srp_rdma_ch *ch)
                         goto out;
 
                 req->indirect_dma_addr = dma_addr;
-                req->index = i;
-                list_add_tail(&req->list, &ch->free_reqs);
         }
         ret = 0;
 
@@ -1076,7 +1072,6 @@ static void srp_free_req(struct srp_rdma_ch *ch, struct srp_request *req,
 
         spin_lock_irqsave(&ch->lock, flags);
         ch->req_lim += req_lim_delta;
-        list_add_tail(&req->list, &ch->free_reqs);
         spin_unlock_irqrestore(&ch->lock, flags);
 }
 
@@ -1648,8 +1643,11 @@ static void srp_process_rsp(struct srp_rdma_ch *ch, struct srp_rsp *rsp)
                         ch->tsk_mgmt_status = rsp->data[3];
                 complete(&ch->tsk_mgmt_done);
         } else {
-                req = &ch->req_ring[rsp->tag];
-                scmnd = srp_claim_req(ch, req, NULL, NULL);
+                scmnd = scsi_host_find_tag(target->scsi_host, rsp->tag);
+                if (scmnd) {
+                        req = (void *)scmnd->host_scribble;
+                        scmnd = srp_claim_req(ch, req, NULL, scmnd);
+                }
                 if (!scmnd) {
                         shost_printk(KERN_ERR, target->scsi_host,
                                      "Null scmnd for RSP w/tag %016llx\n",
@@ -1889,6 +1887,8 @@ static int srp_queuecommand(struct Scsi_Host *shost, struct scsi_cmnd *scmnd)
         struct srp_cmd *cmd;
         struct ib_device *dev;
         unsigned long flags;
+        u32 tag;
+        u16 idx;
         int len, ret;
         const bool in_scsi_eh = !in_interrupt() && current == shost->ehandler;
 
@@ -1905,17 +1905,22 @@ static int srp_queuecommand(struct Scsi_Host *shost, struct scsi_cmnd *scmnd)
         if (unlikely(scmnd->result))
                 goto err;
 
+        WARN_ON_ONCE(scmnd->request->tag < 0);
+        tag = blk_mq_unique_tag(scmnd->request);
         ch = &target->ch;
+        idx = blk_mq_unique_tag_to_tag(tag);
+        WARN_ONCE(idx >= target->req_ring_size, "%s: tag %#x: idx %d >= %d\n",
+                  dev_name(&shost->shost_gendev), tag, idx,
+                  target->req_ring_size);
 
         spin_lock_irqsave(&ch->lock, flags);
         iu = __srp_get_tx_iu(ch, SRP_IU_CMD);
-        if (!iu)
-                goto err_unlock;
-
-        req = list_first_entry(&ch->free_reqs, struct srp_request, list);
-        list_del(&req->list);
         spin_unlock_irqrestore(&ch->lock, flags);
 
+        if (!iu)
+                goto err;
+
+        req = &ch->req_ring[idx];
         dev = target->srp_host->srp_dev->dev;
         ib_dma_sync_single_for_cpu(dev, iu->dma, target->max_iu_len,
                                    DMA_TO_DEVICE);
@@ -1927,7 +1932,7 @@ static int srp_queuecommand(struct Scsi_Host *shost, struct scsi_cmnd *scmnd)
 
         cmd->opcode = SRP_CMD;
         cmd->lun    = cpu_to_be64((u64) scmnd->device->lun << 48);
-        cmd->tag    = req->index;
+        cmd->tag    = tag;
         memcpy(cmd->cdb, scmnd->cmnd, scmnd->cmd_len);
 
         req->scmnd    = scmnd;
@@ -1976,12 +1981,6 @@ err_iu:
          */
         req->scmnd = NULL;
 
-        spin_lock_irqsave(&ch->lock, flags);
-        list_add(&req->list, &ch->free_reqs);
-
-err_unlock:
-        spin_unlock_irqrestore(&ch->lock, flags);
-
 err:
         if (scmnd->result) {
                 scmnd->scsi_done(scmnd);
@@ -2387,6 +2386,7 @@ static int srp_abort(struct scsi_cmnd *scmnd)
 {
         struct srp_target_port *target = host_to_target(scmnd->device->host);
         struct srp_request *req = (struct srp_request *) scmnd->host_scribble;
+        u32 tag;
         struct srp_rdma_ch *ch;
         int ret;
 
@@ -2395,7 +2395,8 @@ static int srp_abort(struct scsi_cmnd *scmnd)
         ch = &target->ch;
         if (!req || !srp_claim_req(ch, req, NULL, scmnd))
                 return SUCCESS;
-        if (srp_send_tsk_mgmt(ch, req->index, scmnd->device->lun,
+        tag = blk_mq_unique_tag(scmnd->request);
+        if (srp_send_tsk_mgmt(ch, tag, scmnd->device->lun,
                               SRP_TSK_ABORT_TASK) == 0)
                 ret = SUCCESS;
         else if (target->rport->state == SRP_RPORT_LOST)
@@ -2633,7 +2634,8 @@ static struct scsi_host_template srp_template = {
         .this_id                        = -1,
         .cmd_per_lun                    = SRP_DEFAULT_CMD_SQ_SIZE,
         .use_clustering                 = ENABLE_CLUSTERING,
-        .shost_attrs                    = srp_host_attrs
+        .shost_attrs                    = srp_host_attrs,
+        .use_blk_tags                   = 1,
 };
 
 static int srp_sdev_count(struct Scsi_Host *host)
@@ -3054,6 +3056,10 @@ static ssize_t srp_create_target(struct device *dev,
         if (ret)
                 goto err;
 
+        ret = scsi_init_shared_tag_map(target_host, target_host->can_queue);
+        if (ret)
+                goto err;
+
         target->req_ring_size = target->queue_size - SRP_TSK_MGMT_SQ_SIZE;
 
         if (!srp_conn_unique(target->srp_host, target)) {
diff --git a/drivers/infiniband/ulp/srp/ib_srp.h b/drivers/infiniband/ulp/srp/ib_srp.h
index 74530d9e6391..37aa9f49947a 100644
--- a/drivers/infiniband/ulp/srp/ib_srp.h
+++ b/drivers/infiniband/ulp/srp/ib_srp.h
@@ -116,7 +116,6 @@ struct srp_host {
 };
 
 struct srp_request {
-        struct list_head        list;
         struct scsi_cmnd       *scmnd;
         struct srp_iu          *cmd;
         union {
@@ -127,7 +126,6 @@ struct srp_request {
         struct srp_direct_buf  *indirect_desc;
         dma_addr_t              indirect_dma_addr;
         short                   nmdesc;
-        short                   index;
 };
 
 /**
@@ -137,7 +135,6 @@ struct srp_request {
 struct srp_rdma_ch {
         /* These are RW in the hot path, and commonly used together */
         struct list_head        free_tx;
-        struct list_head        free_reqs;
         spinlock_t              lock;
         s32                     req_lim;