usb-storage: update earlier scatter-gather bug fix

This patch (as1037) makes a small update to the earlier as1035 patch.
The minimum-length computation shouldn't be done in
usb_stor_access_xfer_buf(), since that routine can be called multiple
times for a single transfer.  It should be done in
usb_stor_set_xfer_buf() instead, which gets called only once.

The way it is now isn't really _wrong_, but it isn't really _right_
either.  Moving the statement will be an improvement.

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

drivers/usb/storage/protocol.c

@@ -170,7 +170,6 @@ unsigned int usb_stor_access_xfer_buf(unsigned char *buffer,
 
 	if (!sg)
 		sg = scsi_sglist(srb);
-	buflen = min(buflen, scsi_bufflen(srb));
 
 	/* This loop handles a single s-g list entry, which may
 	 * include multiple pages.  Find the initial page structure
@@ -232,6 +231,7 @@ void usb_stor_set_xfer_buf(unsigned char *buffer,
 	unsigned int offset = 0;
 	struct scatterlist *sg = NULL;
 
+	buflen = min(buflen, scsi_bufflen(srb));
 	buflen = usb_stor_access_xfer_buf(buffer, buflen, srb, &sg, &offset,
 			TO_XFER_BUF);
 	if (buflen < scsi_bufflen(srb))