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>

drivers/usb/core/hcd.c

@@ -1259,6 +1259,51 @@ static void hcd_free_coherent(struct usb_bus *bus, dma_addr_t *dma_handle,
 	*dma_handle = 0;
 }
 
+static void unmap_urb_for_dma(struct usb_hcd *hcd, struct urb *urb)
+{
+	enum dma_data_direction dir;
+
+	if (urb->transfer_flags & URB_SETUP_MAP_SINGLE)
+		dma_unmap_single(hcd->self.controller,
+				urb->setup_dma,
+				sizeof(struct usb_ctrlrequest),
+				DMA_TO_DEVICE);
+	else if (urb->transfer_flags & URB_SETUP_MAP_LOCAL)
+		hcd_free_coherent(urb->dev->bus,
+				&urb->setup_dma,
+				(void **) &urb->setup_packet,
+				sizeof(struct usb_ctrlrequest),
+				DMA_TO_DEVICE);
+
+	dir = usb_urb_dir_in(urb) ? DMA_FROM_DEVICE : DMA_TO_DEVICE;
+	if (urb->transfer_flags & URB_DMA_MAP_SG)
+		dma_unmap_sg(hcd->self.controller,
+				urb->sg->sg,
+				urb->num_sgs,
+				dir);
+	else if (urb->transfer_flags & URB_DMA_MAP_PAGE)
+		dma_unmap_page(hcd->self.controller,
+				urb->transfer_dma,
+				urb->transfer_buffer_length,
+				dir);
+	else if (urb->transfer_flags & URB_DMA_MAP_SINGLE)
+		dma_unmap_single(hcd->self.controller,
+				urb->transfer_dma,
+				urb->transfer_buffer_length,
+				dir);
+	else if (urb->transfer_flags & URB_MAP_LOCAL)
+		hcd_free_coherent(urb->dev->bus,
+				&urb->transfer_dma,
+				&urb->transfer_buffer,
+				urb->transfer_buffer_length,
+				dir);
+
+	/* Make it safe to call this routine more than once */
+	urb->transfer_flags &= ~(URB_SETUP_MAP_SINGLE | URB_SETUP_MAP_LOCAL |
+			URB_DMA_MAP_SG | URB_DMA_MAP_PAGE |
+			URB_DMA_MAP_SINGLE | URB_MAP_LOCAL);
+}
+
 static int map_urb_for_dma(struct usb_hcd *hcd, struct urb *urb,
 			   gfp_t mem_flags)
 {
@@ -1270,8 +1315,6 @@ static int map_urb_for_dma(struct usb_hcd *hcd, struct urb *urb,
 	 * unless it uses pio or talks to another transport,
 	 * or uses the provided scatter gather list for bulk.
 	 */
-	if (is_root_hub(urb->dev))
-		return 0;
 
 	if (usb_endpoint_xfer_control(&urb->ep->desc)
 	    && !(urb->transfer_flags & URB_NO_SETUP_DMA_MAP)) {
@@ -1284,6 +1327,7 @@ static int map_urb_for_dma(struct usb_hcd *hcd, struct urb *urb,
 			if (dma_mapping_error(hcd->self.controller,
 						urb->setup_dma))
 				return -EAGAIN;
+			urb->transfer_flags |= URB_SETUP_MAP_SINGLE;
 		} else if (hcd->driver->flags & HCD_LOCAL_MEM)
 			ret = hcd_alloc_coherent(
 					urb->dev->bus, mem_flags,
@@ -1291,20 +1335,57 @@ static int map_urb_for_dma(struct usb_hcd *hcd, struct urb *urb,
 					(void **)&urb->setup_packet,
 					sizeof(struct usb_ctrlrequest),
 					DMA_TO_DEVICE);
+			if (ret)
+				return ret;
+			urb->transfer_flags |= URB_SETUP_MAP_LOCAL;
 	}
 
 	dir = usb_urb_dir_in(urb) ? DMA_FROM_DEVICE : DMA_TO_DEVICE;
-	if (ret == 0 && urb->transfer_buffer_length != 0
+	if (urb->transfer_buffer_length != 0
 	    && !(urb->transfer_flags & URB_NO_TRANSFER_DMA_MAP)) {
 		if (hcd->self.uses_dma) {
-			urb->transfer_dma = dma_map_single (
-					hcd->self.controller,
-					urb->transfer_buffer,
-					urb->transfer_buffer_length,
-					dir);
-			if (dma_mapping_error(hcd->self.controller,
+			if (urb->num_sgs) {
+				int n = dma_map_sg(
+						hcd->self.controller,
+						urb->sg->sg,
+						urb->num_sgs,
+						dir);
+				if (n <= 0)
+					ret = -EAGAIN;
+				else
+					urb->transfer_flags |= URB_DMA_MAP_SG;
+				if (n != urb->num_sgs) {
+					urb->num_sgs = n;
+					urb->transfer_flags |=
+							URB_DMA_SG_COMBINED;
+				}
+			} else if (urb->sg) {
+				struct scatterlist *sg;
+
+				sg = (struct scatterlist *) urb->sg;
+				urb->transfer_dma = dma_map_page(
+						hcd->self.controller,
+						sg_page(sg),
+						sg->offset,
+						urb->transfer_buffer_length,
+						dir);
+				if (dma_mapping_error(hcd->self.controller,
 						urb->transfer_dma))
-				return -EAGAIN;
+					ret = -EAGAIN;
+				else
+					urb->transfer_flags |= URB_DMA_MAP_PAGE;
+			} else {
+				urb->transfer_dma = dma_map_single(
+						hcd->self.controller,
+						urb->transfer_buffer,
+						urb->transfer_buffer_length,
+						dir);
+				if (dma_mapping_error(hcd->self.controller,
+						urb->transfer_dma))
+					ret = -EAGAIN;
+				else
+					urb->transfer_flags |= URB_DMA_MAP_SINGLE;
+			}
 		} else if (hcd->driver->flags & HCD_LOCAL_MEM) {
 			ret = hcd_alloc_coherent(
 					urb->dev->bus, mem_flags,
@@ -1312,55 +1393,16 @@ static int map_urb_for_dma(struct usb_hcd *hcd, struct urb *urb,
 					&urb->transfer_buffer,
 					urb->transfer_buffer_length,
 					dir);
-
-			if (ret && usb_endpoint_xfer_control(&urb->ep->desc)
-			    && !(urb->transfer_flags & URB_NO_SETUP_DMA_MAP))
-				hcd_free_coherent(urb->dev->bus,
-					&urb->setup_dma,
-					(void **)&urb->setup_packet,
-					sizeof(struct usb_ctrlrequest),
-					DMA_TO_DEVICE);
+			if (ret == 0)
+				urb->transfer_flags |= URB_MAP_LOCAL;
 		}
+		if (ret && (urb->transfer_flags & (URB_SETUP_MAP_SINGLE |
+				URB_SETUP_MAP_LOCAL)))
+			unmap_urb_for_dma(hcd, urb);
 	}
 	return ret;
 }
 
-static void unmap_urb_for_dma(struct usb_hcd *hcd, struct urb *urb)
-{
-	enum dma_data_direction dir;
-
-	if (is_root_hub(urb->dev))
-		return;
-
-	if (usb_endpoint_xfer_control(&urb->ep->desc)
-	    && !(urb->transfer_flags & URB_NO_SETUP_DMA_MAP)) {
-		if (hcd->self.uses_dma)
-			dma_unmap_single(hcd->self.controller, urb->setup_dma,
-					sizeof(struct usb_ctrlrequest),
-					DMA_TO_DEVICE);
-		else if (hcd->driver->flags & HCD_LOCAL_MEM)
-			hcd_free_coherent(urb->dev->bus, &urb->setup_dma,
-					(void **)&urb->setup_packet,
-					sizeof(struct usb_ctrlrequest),
-					DMA_TO_DEVICE);
-	}
-
-	dir = usb_urb_dir_in(urb) ? DMA_FROM_DEVICE : DMA_TO_DEVICE;
-	if (urb->transfer_buffer_length != 0
-	    && !(urb->transfer_flags & URB_NO_TRANSFER_DMA_MAP)) {
-		if (hcd->self.uses_dma)
-			dma_unmap_single(hcd->self.controller,
-					urb->transfer_dma,
-					urb->transfer_buffer_length,
-					dir);
-		else if (hcd->driver->flags & HCD_LOCAL_MEM)
-			hcd_free_coherent(urb->dev->bus, &urb->transfer_dma,
-					&urb->transfer_buffer,
-					urb->transfer_buffer_length,
-					dir);
-	}
-}
-
 /*-------------------------------------------------------------------------*/
 
 /* may be called in any context with a valid urb->dev usecount
@@ -1389,21 +1431,20 @@ int usb_hcd_submit_urb (struct urb *urb, gfp_t mem_flags)
 	 * URBs must be submitted in process context with interrupts
 	 * enabled.
 	 */
-	status = map_urb_for_dma(hcd, urb, mem_flags);
-	if (unlikely(status)) {
-		usbmon_urb_submit_error(&hcd->self, urb, status);
-		goto error;
-	}
 
-	if (is_root_hub(urb->dev))
+	if (is_root_hub(urb->dev)) {
 		status = rh_urb_enqueue(hcd, urb);
-	else
-		status = hcd->driver->urb_enqueue(hcd, urb, mem_flags);
+	} else {
+		status = map_urb_for_dma(hcd, urb, mem_flags);
+		if (likely(status == 0)) {
+			status = hcd->driver->urb_enqueue(hcd, urb, mem_flags);
+			if (unlikely(status))
+				unmap_urb_for_dma(hcd, urb);
+		}
+	}
 
 	if (unlikely(status)) {
 		usbmon_urb_submit_error(&hcd->self, urb, status);
-		unmap_urb_for_dma(hcd, urb);
- error:
 		urb->hcpriv = NULL;
 		INIT_LIST_HEAD(&urb->urb_list);
 		atomic_dec(&urb->use_count);

drivers/usb/core/message.c

@@ -259,9 +259,6 @@ static void sg_clean(struct usb_sg_request *io)
 		kfree(io->urbs);
 		io->urbs = NULL;
 	}
-	if (io->dev->dev.dma_mask != NULL)
-		usb_buffer_unmap_sg(io->dev, usb_pipein(io->pipe),
-				    io->sg, io->nents);
 	io->dev = NULL;
 }
 
@@ -364,7 +361,6 @@ int usb_sg_init(struct usb_sg_request *io, struct usb_device *dev,
 {
 	int i;
 	int urb_flags;
-	int dma;
 	int use_sg;
 
 	if (!io || !dev || !sg
@@ -378,21 +374,9 @@ int usb_sg_init(struct usb_sg_request *io, struct usb_device *dev,
 	io->pipe = pipe;
 	io->sg = sg;
 	io->nents = nents;
-
-	/* not all host controllers use DMA (like the mainstream pci ones);
-	 * they can use PIO (sl811) or be software over another transport.
-	 */
-	dma = (dev->dev.dma_mask != NULL);
-	if (dma)
-		io->entries = usb_buffer_map_sg(dev, usb_pipein(pipe),
-						sg, nents);
-	else
-		io->entries = nents;
+	io->entries = nents;
 
 	/* initialize all the urbs we'll use */
-	if (io->entries <= 0)
-		return io->entries;
-
 	if (dev->bus->sg_tablesize > 0) {
 		io->urbs = kmalloc(sizeof *io->urbs, mem_flags);
 		use_sg = true;
@@ -404,8 +388,6 @@ int usb_sg_init(struct usb_sg_request *io, struct usb_device *dev,
 		goto nomem;
 
 	urb_flags = 0;
-	if (dma)
-		urb_flags |= URB_NO_TRANSFER_DMA_MAP;
 	if (usb_pipein(pipe))
 		urb_flags |= URB_SHORT_NOT_OK;
 
@@ -423,12 +405,13 @@ int usb_sg_init(struct usb_sg_request *io, struct usb_device *dev,
 
 		io->urbs[0]->complete = sg_complete;
 		io->urbs[0]->context = io;
+
 		/* A length of zero means transfer the whole sg list */
 		io->urbs[0]->transfer_buffer_length = length;
 		if (length == 0) {
 			for_each_sg(sg, sg, io->entries, i) {
 				io->urbs[0]->transfer_buffer_length +=
-					sg_dma_len(sg);
+					sg->length;
 			}
 		}
 		io->urbs[0]->sg = io;
@@ -454,26 +437,16 @@ int usb_sg_init(struct usb_sg_request *io, struct usb_device *dev,
 			io->urbs[i]->context = io;
 
 			/*
-			 * Some systems need to revert to PIO when DMA is temporarily
-			 * unavailable.  For their sakes, both transfer_buffer and
-			 * transfer_dma are set when possible.
-			 *
-			 * Note that if IOMMU coalescing occurred, we cannot
-			 * trust sg_page anymore, so check if S/G list shrunk.
+			 * Some systems can't use DMA; they use PIO instead.
+			 * For their sakes, transfer_buffer is set whenever
+			 * possible.
 			 */
-			if (io->nents == io->entries && !PageHighMem(sg_page(sg)))
+			if (!PageHighMem(sg_page(sg)))
 				io->urbs[i]->transfer_buffer = sg_virt(sg);
 			else
 				io->urbs[i]->transfer_buffer = NULL;
 
-			if (dma) {
-				io->urbs[i]->transfer_dma = sg_dma_address(sg);
-				len = sg_dma_len(sg);
-			} else {
-				/* hc may use _only_ transfer_buffer */
-				len = sg->length;
-			}
-
+			len = sg->length;
 			if (length) {
 				len = min_t(unsigned, len, length);
 				length -= len;
@@ -481,6 +454,8 @@ int usb_sg_init(struct usb_sg_request *io, struct usb_device *dev,
 					io->entries = i + 1;
 			}
 			io->urbs[i]->transfer_buffer_length = len;
+
+			io->urbs[i]->sg = (struct usb_sg_request *) sg;
 		}
 		io->urbs[--i]->transfer_flags &= ~URB_NO_INTERRUPT;
 	}

drivers/usb/core/urb.c

@@ -333,9 +333,12 @@ int usb_submit_urb(struct urb *urb, gfp_t mem_flags)
 		is_out = usb_endpoint_dir_out(&ep->desc);
 	}
 
-	/* Cache the direction for later use */
-	urb->transfer_flags = (urb->transfer_flags & ~URB_DIR_MASK) |
-			(is_out ? URB_DIR_OUT : URB_DIR_IN);
+	/* Clear the internal flags and cache the direction for later use */
+	urb->transfer_flags &= ~(URB_DIR_MASK | URB_DMA_MAP_SINGLE |
+			URB_DMA_MAP_PAGE | URB_DMA_MAP_SG | URB_MAP_LOCAL |
+			URB_SETUP_MAP_SINGLE | URB_SETUP_MAP_LOCAL |
+			URB_DMA_SG_COMBINED);
+	urb->transfer_flags |= (is_out ? URB_DIR_OUT : URB_DIR_IN);
 
 	if (xfertype != USB_ENDPOINT_XFER_CONTROL &&
 			dev->state < USB_STATE_CONFIGURED)

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

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);

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;

drivers/usb/mon/mon_bin.c

@@ -416,7 +416,7 @@ static unsigned int mon_bin_get_data(const struct mon_reader_bin *rp,
 
 	} else {
 		/* If IOMMU coalescing occurred, we cannot trust sg_page */
-		if (urb->sg->nents != urb->num_sgs) {
+		if (urb->transfer_flags & URB_DMA_SG_COMBINED) {
 			*flag = 'D';
 			return length;
 		}

drivers/usb/mon/mon_text.c

@@ -161,9 +161,7 @@ static inline char mon_text_get_data(struct mon_event_text *ep, struct urb *urb,
 	} else {
 		struct scatterlist *sg = urb->sg->sg;
 
-		/* If IOMMU coalescing occurred, we cannot trust sg_page */
-		if (urb->sg->nents != urb->num_sgs ||
-				PageHighMem(sg_page(sg)))
+		if (PageHighMem(sg_page(sg)))
 			return 'D';
 
 		/* For the text interface we copy only the first sg buffer */

include/linux/usb.h

@@ -965,10 +965,19 @@ extern int usb_disabled(void);
 					 * needed */
 #define URB_FREE_BUFFER		0x0100	/* Free transfer buffer with the URB */
 
+/* The following flags are used internally by usbcore and HCDs */
 #define URB_DIR_IN		0x0200	/* Transfer from device to host */
 #define URB_DIR_OUT		0
 #define URB_DIR_MASK		URB_DIR_IN
 
+#define URB_DMA_MAP_SINGLE	0x00010000	/* Non-scatter-gather mapping */
+#define URB_DMA_MAP_PAGE	0x00020000	/* HCD-unsupported S-G */
+#define URB_DMA_MAP_SG		0x00040000	/* HCD-supported S-G */
+#define URB_MAP_LOCAL		0x00080000	/* HCD-local-memory mapping */
+#define URB_SETUP_MAP_SINGLE	0x00100000	/* Setup packet DMA mapped */
+#define URB_SETUP_MAP_LOCAL	0x00200000	/* HCD-local setup packet */
+#define URB_DMA_SG_COMBINED	0x00400000	/* S-G entries were combined */
+
 struct usb_iso_packet_descriptor {
 	unsigned int offset;
 	unsigned int length;		/* expected length */