[SCSI] scsi_kmap_atomic_sg(): check that local irqs are disabled

The KM_BIO_SRC_IRQ kmap slot must be taken with local irqs disabled.  Add a
check into scsi for this.

Cc: James Bottomley <James.Bottomley@steeleye.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 503f09c..0f9b6c2 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -2250,6 +2250,8 @@
 	size_t sg_len = 0, len_complete = 0;
 	struct page *page;
 
+	WARN_ON(!irqs_disabled());
+
 	for (i = 0; i < sg_count; i++) {
 		len_complete = sg_len; /* Complete sg-entries */
 		sg_len += sg[i].length;