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>

1 files changed, 4 insertions, 0 deletions

diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c
index 097172e2ba06..8180ce533ebf 100644
--- a/drivers/usb/core/usb.c
+++ b/drivers/usb/core/usb.c
@@ -881,6 +881,7 @@ void usb_buffer_unmap(struct urb *urb)
 EXPORT_SYMBOL_GPL(usb_buffer_unmap);
 #endif  /*  0  */
 
+#if 0
 /**
  * usb_buffer_map_sg - create scatterlist DMA mapping(s) for an endpoint
  * @dev: device to which the scatterlist will be mapped
@@ -924,6 +925,7 @@ int usb_buffer_map_sg(const struct usb_device *dev, int is_in,
                         is_in ? DMA_FROM_DEVICE : DMA_TO_DEVICE) ? : -ENOMEM;
 }
 EXPORT_SYMBOL_GPL(usb_buffer_map_sg);
+#endif
 
 /* XXX DISABLED, no users currently.  If you wish to re-enable this
  * XXX please determine whether the sync is to transfer ownership of
@@ -960,6 +962,7 @@ void usb_buffer_dmasync_sg(const struct usb_device *dev, int is_in,
 EXPORT_SYMBOL_GPL(usb_buffer_dmasync_sg);
 #endif
 
+#if 0
 /**
  * usb_buffer_unmap_sg - free DMA mapping(s) for a scatterlist
  * @dev: device to which the scatterlist will be mapped
@@ -985,6 +988,7 @@ void usb_buffer_unmap_sg(const struct usb_device *dev, int is_in,
                         is_in ? DMA_FROM_DEVICE : DMA_TO_DEVICE);
 }
 EXPORT_SYMBOL_GPL(usb_buffer_unmap_sg);
+#endif
 
 /* To disable USB, kernel command line is 'nousb' not 'usbcore.nousb' */
 #ifdef MODULE