USB: fix usbmon and DMA mapping for scatter-gather URBs

This patch (as1368) fixes a rather obscure bug in usbmon: When tracing
URBs sent by the scatter-gather library, it accesses the data buffers
while they are still mapped for DMA.

The solution is to move the mapping and unmapping out of the s-g
library and into the usual place in hcd.c.  This requires the addition
of new URB flag bits to describe the kind of mapping needed, since we
have to call dma_map_sg() if the HCD supports native scatter-gather
operation and dma_map_page() if it doesn't.  The nice thing about
having the new flags is that they simplify the testing for unmapping.

The patch removes the only caller of usb_buffer_[un]map_sg(), so those
functions are #if'ed out.  A later patch will remove them entirely.

As a result of this change, urb->sg will be set in situations where
it wasn't set previously.  Hence the xhci and whci drivers are
adjusted to test urb->num_sgs instead, which retains its original
meaning and is nonzero only when the HCD has to handle a scatterlist.

Finally, even when a submission error occurs we don't want to hand
URBs to usbmon before they are unmapped.  The submission path is
rearranged so that map_urb_for_dma() is called only for non-root-hub
URBs and unmap_urb_for_dma() is called immediately after a submission
error.  This simplifies the error handling.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
CC: <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

2 files changed, 2 insertions, 2 deletions

diff --git a/drivers/usb/host/whci/qset.c b/drivers/usb/host/whci/qset.c
index 141d049..b388dd1 100644
--- a/drivers/usb/host/whci/qset.c
+++ b/drivers/usb/host/whci/qset.c
@@ -646,7 +646,7 @@ int qset_add_urb(struct whc *whc, struct whc_qset *qset, struct urb *urb,
 	wurb->urb = urb;
 	INIT_WORK(&wurb->dequeue_work, urb_dequeue_work);
 
-	if (urb->sg) {
+	if (urb->num_sgs) {
 		ret = qset_add_urb_sg(whc, qset, urb, mem_flags);
 		if (ret == -EINVAL) {
 			qset_free_stds(qset, urb);
diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index 407d33f..c1359ed 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -1962,7 +1962,7 @@ int xhci_queue_bulk_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
 	int running_total, trb_buff_len, ret;
 	u64 addr;
 
-	if (urb->sg)
+	if (urb->num_sgs)
 		return queue_bulk_sg_tx(xhci, mem_flags, urb, slot_id, ep_index);
 
 	ep_ring = xhci->devs[slot_id]->eps[ep_index].ring;