Comment provided by Bart Van and Chris H is addressed in this patch.
Add use_cmd_list flag in scsi_host to indicate scs.mq stack
to keep track of cmd_list per sdev.
Default behaviour is not to keep track of cmd_list per sdev, as this may introduce
lock contention. (overhead is more on multi-node NUMA.)
Patch is tested using megaraid_sas driver with "use_cmd_list" value set to 1 and 0.
Added MAINTAINER of Adaptec to verify changes.
Signed-off-by: Kashyap Desai <kashyap.desai@xxxxxxxxxxxxx>
--
diff --git a/drivers/scsi/aacraid/linit.c b/drivers/scsi/aacraid/linit.c
index 63f576c..a759cb2 100644
--- a/drivers/scsi/aacraid/linit.c
+++ b/drivers/scsi/aacraid/linit.c
@@ -1152,6 +1152,7 @@ static int aac_probe_one(struct pci_dev *pdev, const struct pci_device_id *id)
shost->irq = pdev->irq;
shost->unique_id = unique_id;
shost->max_cmd_len = 16;
+ shost->use_cmd_list = 1;
aac = (struct aac_dev *)shost->hostdata;
aac->base_start = pci_resource_start(pdev, 0);
diff --git a/drivers/scsi/dpt_i2o.c b/drivers/scsi/dpt_i2o.c
index 67283ef..072f0ec 100644
--- a/drivers/scsi/dpt_i2o.c
+++ b/drivers/scsi/dpt_i2o.c
@@ -2363,6 +2363,7 @@ static s32 adpt_scsi_host_alloc(adpt_hba* pHba, struct scsi_host_template *sht)
host->unique_id = (u32)sys_tbl_pa + pHba->unit;
host->sg_tablesize = pHba->sg_tablesize;
host->can_queue = pHba->post_fifo_size;
+ host->use_cmd_list = 1;
return 0;
}
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 9c44392..f9ce306 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -645,16 +645,18 @@ static void scsi_mq_free_sgtables(struct scsi_cmnd *cmd)
static void scsi_mq_uninit_cmd(struct scsi_cmnd *cmd)
{
struct scsi_device *sdev = cmd->device;
+ struct Scsi_Host *shost = sdev->host;
unsigned long flags;
- BUG_ON(list_empty(&cmd->list));
-
scsi_mq_free_sgtables(cmd);
scsi_uninit_cmd(cmd);
- spin_lock_irqsave(&sdev->list_lock, flags);
- list_del_init(&cmd->list);
- spin_unlock_irqrestore(&sdev->list_lock, flags);
+ if (shost->use_cmd_list) {
+ BUG_ON(list_empty(&cmd->list));
+ spin_lock_irqsave(&sdev->list_lock, flags);
+ list_del_init(&cmd->list);
+ spin_unlock_irqrestore(&sdev->list_lock, flags);
+ }
}
/*
@@ -1815,14 +1817,12 @@ static int scsi_mq_prep_fn(struct request *req)
INIT_LIST_HEAD(&cmd->list);
INIT_DELAYED_WORK(&cmd->abort_work, scmd_eh_abort_handler);
cmd->jiffies_at_alloc = jiffies;
-
- /*
- * XXX: cmd_list lookups are only used by two drivers, try to get
- * rid of this list in common code.
- */
- spin_lock_irq(&sdev->list_lock);
- list_add_tail(&cmd->list, &sdev->cmd_list);
- spin_unlock_irq(&sdev->list_lock);
+
+ if (shost->use_cmd_list) {
+ spin_lock_irq(&sdev->list_lock);
+ list_add_tail(&cmd->list, &sdev->cmd_list);
+ spin_unlock_irq(&sdev->list_lock);
+ }
sg = (void *)cmd + sizeof(struct scsi_cmnd) + shost->hostt->cmd_size;
cmd->sdb.table.sgl = sg;
diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h
index ba20347..cafb260 100644
--- a/include/scsi/scsi_host.h
+++ b/include/scsi/scsi_host.h
@@ -680,6 +680,7 @@ struct Scsi_Host {
unsigned no_write_same:1;
unsigned use_blk_mq:1;
+ unsigned use_cmd_list:1;
/*
* Optional work queue to be utilized by the transport
--
To unsubscribe from this list: send the line "unsubscribe linux-scsi" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
