IB/srp: reduce lock coverage of command completion

We only need the lock to cover list and credit manipulations, so push
those into srp_remove_req() and update the call chains.

We reorder the request removal and command completion in
srp_process_rsp() to avoid the SCSI mid-layer sending another command
before we've released our request and added any credits returned by the
target. This prevents us from returning HOST_BUSY unneccesarily.

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
[ broken out, small cleanups, and modified to avoid potential extraneous
  HOST_BUSY returns by David Dillow ]
Signed-off-by: David Dillow <dillowda@ornl.gov>

diff --git a/drivers/infiniband/ulp/srp/ib_srp.c b/drivers/infiniband/ulp/srp/ib_srp.c
index e5bd181..e76fe54 100644 (file)
--- a/drivers/infiniband/ulp/srp/ib_srp.c
+++ b/drivers/infiniband/ulp/srp/ib_srp.c
@@ -549,18 +549,24 @@ static void srp_unmap_data(struct scsi_cmnd *scmnd,
                        scsi_sg_count(scmnd), scmnd->sc_data_direction);
 }
 
-static void srp_remove_req(struct srp_target_port *target, struct srp_request *req)
+static void srp_remove_req(struct srp_target_port *target,
+                          struct srp_request *req, s32 req_lim_delta)
 {
+       unsigned long flags;
+
        srp_unmap_data(req->scmnd, target, req);
+       spin_lock_irqsave(target->scsi_host->host_lock, flags);
+       target->req_lim += req_lim_delta;
        req->scmnd = NULL;
        list_add_tail(&req->list, &target->free_reqs);
+       spin_unlock_irqrestore(target->scsi_host->host_lock, flags);
 }
 
 static void srp_reset_req(struct srp_target_port *target, struct srp_request *req)
 {
        req->scmnd->result = DID_RESET << 16;
        req->scmnd->scsi_done(req->scmnd);
-       srp_remove_req(target, req);
+       srp_remove_req(target, req, 0);
 }
 
 static int srp_reconnect_target(struct srp_target_port *target)
@@ -595,13 +601,11 @@ static int srp_reconnect_target(struct srp_target_port *target)
        while (ib_poll_cq(target->send_cq, 1, &wc) > 0)
                ; /* nothing */
 
-       spin_lock_irq(target->scsi_host->host_lock);
        for (i = 0; i < SRP_CMD_SQ_SIZE; ++i) {
                struct srp_request *req = &target->req_ring[i];
                if (req->scmnd)
                        srp_reset_req(target, req);
        }
-       spin_unlock_irq(target->scsi_host->host_lock);
 
        INIT_LIST_HEAD(&target->free_tx);
        for (i = 0; i < SRP_SQ_SIZE; ++i)
@@ -914,15 +918,12 @@ static void srp_process_rsp(struct srp_target_port *target, struct srp_rsp *rsp)
        struct srp_request *req;
        struct scsi_cmnd *scmnd;
        unsigned long flags;
-       s32 delta;
-
-       delta = (s32) be32_to_cpu(rsp->req_lim_delta);
-
-       spin_lock_irqsave(target->scsi_host->host_lock, flags);
-
-       target->req_lim += delta;
 
        if (unlikely(rsp->tag & SRP_TAG_TSK_MGMT)) {
+               spin_lock_irqsave(target->scsi_host->host_lock, flags);
+               target->req_lim += be32_to_cpu(rsp->req_lim_delta);
+               spin_unlock_irqrestore(target->scsi_host->host_lock, flags);
+
                target->tsk_mgmt_status = -1;
                if (be32_to_cpu(rsp->resp_data_len) >= 4)
                        target->tsk_mgmt_status = rsp->data[3];
@@ -948,12 +949,10 @@ static void srp_process_rsp(struct srp_target_port *target, struct srp_rsp *rsp)
                else if (rsp->flags & (SRP_RSP_FLAG_DIOVER | SRP_RSP_FLAG_DIUNDER))
                        scsi_set_resid(scmnd, be32_to_cpu(rsp->data_in_res_cnt));
 
+               srp_remove_req(target, req, be32_to_cpu(rsp->req_lim_delta));
                scmnd->host_scribble = NULL;
                scmnd->scsi_done(scmnd);
-               srp_remove_req(target, req);
        }
-
-       spin_unlock_irqrestore(target->scsi_host->host_lock, flags);
 }
 
 static int srp_response_common(struct srp_target_port *target, s32 req_delta,
@@ -1498,18 +1497,14 @@ static int srp_abort(struct scsi_cmnd *scmnd)
                              SRP_TSK_ABORT_TASK))
                return FAILED;
 
-       spin_lock_irq(target->scsi_host->host_lock);
-
        if (req->scmnd) {
                if (!target->tsk_mgmt_status) {
-                       srp_remove_req(target, req);
+                       srp_remove_req(target, req, 0);
                        scmnd->result = DID_ABORT << 16;
                } else
                        ret = FAILED;
        }
 
-       spin_unlock_irq(target->scsi_host->host_lock);
-
        return ret;
 }
 
@@ -1528,16 +1523,12 @@ static int srp_reset_device(struct scsi_cmnd *scmnd)
        if (target->tsk_mgmt_status)
                return FAILED;
 
-       spin_lock_irq(target->scsi_host->host_lock);
-
        for (i = 0; i < SRP_CMD_SQ_SIZE; ++i) {
                struct srp_request *req = &target->req_ring[i];
                if (req->scmnd && req->scmnd->device == scmnd->device)
                        srp_reset_req(target, req);
        }
 
-       spin_unlock_irq(target->scsi_host->host_lock);
-
        return SUCCESS;
 }