[SCSI] Fix hang with split requests

Sometimes, particularly for USB devices with the last sector bug,
requests get completed in chunks.  There's a bug in this in that if
one of the chunks gets an error, we complete that chunk with an error
but never move on to the remaining ones, leading to the request
hanging (because it's not fully completed).

Fix this by completing all remaining chunks if an error is encountered.

Cc: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: NJames Bottomley <James.Bottomley@HansenPartnership.com>

drivers/scsi/scsi_lib.c

@@ -852,7 +852,7 @@ static void scsi_end_bidi_request(struct scsi_cmnd *cmd)
 void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
 {
 	int result = cmd->result;
-	int this_count = scsi_bufflen(cmd);
+	int this_count;
 	struct request_queue *q = cmd->device->request_queue;
 	struct request *req = cmd->request;
 	int error = 0;
@@ -908,6 +908,7 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
 	 */
 	if (scsi_end_request(cmd, error, good_bytes, result == 0) == NULL)
 		return;
+	this_count = blk_rq_bytes(req);
 
 	/* good_bytes = 0, or (inclusive) there were leftovers and
 	 * result = 0, so scsi_end_request couldn't retry.