[SCSI] target: Fix interrupt context bug with stats_lock and core_tmr_alloc_req

This patch fixes two bugs wrt to the interrupt context usage of target
core with HW target mode drivers.  It first converts the usage of struct
se_device->stats_lock in transport_get_lun_for_cmd() and core_tmr_lun_reset()
to properly use spin_lock_irq() to address an BUG with CONFIG_LOCKDEP_SUPPORT=y
enabled.

This patch also adds a 'in_interrupt()' check to allow GFP_ATOMIC usage from
core_tmr_alloc_req() to fix a 'sleeping in interrupt context' BUG with HW
target fabrics that require this logic to function.

Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Cc: stable@kernel.org
Signed-off-by: James Bottomley <jbottomley@parallels.com>
diff --git a/drivers/target/target_core_device.c b/drivers/target/target_core_device.c
index d25e208..fc10ed4 100644
--- a/drivers/target/target_core_device.c
+++ b/drivers/target/target_core_device.c
@@ -150,13 +150,13 @@
 
 	{
 	struct se_device *dev = se_lun->lun_se_dev;
-	spin_lock(&dev->stats_lock);
+	spin_lock_irq(&dev->stats_lock);
 	dev->num_cmds++;
 	if (se_cmd->data_direction == DMA_TO_DEVICE)
 		dev->write_bytes += se_cmd->data_length;
 	else if (se_cmd->data_direction == DMA_FROM_DEVICE)
 		dev->read_bytes += se_cmd->data_length;
-	spin_unlock(&dev->stats_lock);
+	spin_unlock_irq(&dev->stats_lock);
 	}
 
 	/*