scsi: add use_cmd_list flag
Add a use_cmd_list flag in struct Scsi_Host to request keeping track of
all outstanding commands per device.
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.), and
only enable it on the two drivers that need it.
Signed-off-by: Kashyap Desai <kashyap.desai@avagotech.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index d837dc1..b9a8ddd 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -645,16 +645,18 @@
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);
+ }
}
/*
@@ -1815,13 +1817,11 @@
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;