[SCSI] libiscsi_tcp: use kmap in xmit path

The xmit path can sleep with a page kmapped in the network
xmit code while it waits for space to open up, so we have to use
kmap instead of kmap atomic in that path.
Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>

drivers/scsi/libiscsi_tcp.c

@@ -132,14 +132,25 @@ static void iscsi_tcp_segment_map(struct iscsi_segment *segment, int recv)
 	if (page_count(sg_page(sg)) >= 1 && !recv)
 		return;
 
+	if (recv) {
+		segment->atomic_mapped = true;
 		segment->sg_mapped = kmap_atomic(sg_page(sg), KM_SOFTIRQ0);
+	} else {
+		segment->atomic_mapped = false;
+		/* the xmit path can sleep with the page mapped so use kmap */
+		segment->sg_mapped = kmap(sg_page(sg));
+	}
+
 	segment->data = segment->sg_mapped + sg->offset + segment->sg_offset;
 }
 
 void iscsi_tcp_segment_unmap(struct iscsi_segment *segment)
 {
 	if (segment->sg_mapped) {
+		if (segment->atomic_mapped)
 			kunmap_atomic(segment->sg_mapped, KM_SOFTIRQ0);
+		else
+			kunmap(sg_page(segment->sg));
 		segment->sg_mapped = NULL;
 		segment->data = NULL;
 	}

include/scsi/libiscsi_tcp.h

@@ -47,6 +47,7 @@ struct iscsi_segment {
 	struct scatterlist	*sg;
 	void			*sg_mapped;
 	unsigned int		sg_offset;
+	bool			atomic_mapped;
 
 	iscsi_segment_done_fn_t	*done;
 };