Tue Aug 21 18:55:09 2018 UTC ()

(only commit message for rev 1.85, no actual change)

shuffle code in xbd_handler() response loop so that req_bp is never
touched for non I/O responses; unknown commands are now just skipped, also
without touching neither xbdreq, nor req_bp

add some KASSERTS() for xbdreq->req_nr_segments and xbdreq->req_bp,
and reset req_bp after it's processed to ensure the buf can never
be processed twice

intended to simplify debugging in cases like PR port-xen/53506


(jdolecek)

diff -r1.85 -r1.86 src/sys/arch/xen/xen/xbd_xenbus.c

--- src/sys/arch/xen/xen/xbd_xenbus.c 2018/08/21 18:45:16	1.85
+++ src/sys/arch/xen/xen/xbd_xenbus.c 2018/08/21 18:55:08	1.86

 @@ -1,14 +1,14 @@
-/*      $NetBSD: xbd_xenbus.c,v 1.85 2018/08/21 18:45:16 jdolecek Exp $      */
+/*      $NetBSD: xbd_xenbus.c,v 1.86 2018/08/21 18:55:08 jdolecek Exp $      */
 /*
  * Copyright (c) 2006 Manuel Bouyer.
+ *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
+ *
 @@ -40,27 +40,27 @@
  * - initiate request: xbdread/write/open/ioctl/..
  * - depending on operation, it is handled directly by disk(9) subsystem or
  *   goes through physio(9) first.
  * - the request is ultimately processed by xbd_diskstart() that prepares the
  *   xbd requests, post them in the ring I/O queue, then signal the backend.
+ *
  * When a response is available in the queue, the backend signals the frontend
  * via its event channel. This triggers xbd_handler(), which will link back
  * the response to its request through the request ID, and mark the I/O as
  * completed.
  */
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: xbd_xenbus.c,v 1.85 2018/08/21 18:45:16 jdolecek Exp $");
+__KERNEL_RCSID(0, "$NetBSD: xbd_xenbus.c,v 1.86 2018/08/21 18:55:08 jdolecek Exp $");
 #include "opt_xen.h"
 #include <sys/param.h>
 #include <sys/buf.h>
 #include <sys/bufq.h>
 #include <sys/device.h>
 #include <sys/disk.h>
 #include <sys/disklabel.h>
 #include <sys/conf.h>
 #include <sys/fcntl.h>
 #include <sys/kernel.h>
 @@ -683,26 +683,27 @@ again:
 			    xengnt_status(xbdreq->req_gntref[seg]))) {
 				aprint_verbose_dev(sc->sc_dksc.sc_dev,
 					"grant still used by backend\n");
 				sc->sc_ring.rsp_cons = i;
 				xbdreq->req_nr_segments = seg + 1;
 				goto done;
+			}
 			xengnt_revoke_access(xbdreq->req_gntref[seg]);
 			xbdreq->req_nr_segments--;
+		}
 		KASSERT(xbdreq->req_nr_segments == 0);
 		bp = xbdreq->req_bp;
 		KASSERT(bp != NULL);
 		xbdreq->req_bp = NULL;
 		DPRINTF(("%s(%p): b_bcount = %ld\n", __func__,
 		    bp, (long)bp->b_bcount));
 		if (rep->status != BLKIF_RSP_OKAY) {
 			bp->b_error = EIO;
 			bp->b_resid = bp->b_bcount;
 			goto next;
+		}
 		/* b_resid was set in dk_start */
 next:
 		dk_done(&sc->sc_dksc, bp);