 @@ -1,14 +1,14 @@
-/*      $NetBSD: xbdback_xenbus.c,v 1.82 2020/04/20 14:11:04 jdolecek Exp $      */
+/*      $NetBSD: xbdback_xenbus.c,v 1.83 2020/04/20 16:12:28 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.
+ *
 @@ -16,27 +16,27 @@
  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
  */
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: xbdback_xenbus.c,v 1.82 2020/04/20 14:11:04 jdolecek Exp $");
+__KERNEL_RCSID(0, "$NetBSD: xbdback_xenbus.c,v 1.83 2020/04/20 16:12:28 jdolecek Exp $");
 #include <sys/atomic.h>
 #include <sys/buf.h>
 #include <sys/condvar.h>
 #include <sys/conf.h>
 #include <sys/disk.h>
 #include <sys/device.h>
 #include <sys/fcntl.h>
 #include <sys/kauth.h>
 #include <sys/kernel.h>
 #include <sys/kmem.h>
 #include <sys/kthread.h>
 #include <sys/mutex.h>
 @@ -64,91 +64,76 @@ __KERNEL_RCSID(0, "$NetBSD: xbdback_xenb
 #define BLKIF_RING_SIZE __CONST_RING_SIZE(blkif, PAGE_SIZE)
 /*
  * Backend block device driver for Xen
  */
 /* Values are expressed in 512-byte sectors */
 #define VBD_BSIZE 512
 #define VBD_MAXSECT ((PAGE_SIZE / VBD_BSIZE) - 1)
 /* Need to alloc one extra page to account for possible mapping offset */
 #define VBD_VA_SIZE	(MAXPHYS + PAGE_SIZE)
 struct xbdback_request;
 struct xbdback_io;
 struct xbdback_fragment;
 struct xbdback_instance;
 /*
  * status of a xbdback instance:
  * WAITING: xbdback instance is connected, waiting for requests
  * RUN: xbdi thread must be woken up, I/Os have to be processed
  * DISCONNECTING: the instance is closing, no more I/Os can be scheduled
  * DISCONNECTED: no I/Os, no ring, the thread should terminate.
  */
 typedef enum {WAITING, RUN, DISCONNECTING, DISCONNECTED} xbdback_state_t;
 /*
  * Each xbdback instance is managed by a single thread that handles all
  * the I/O processing. As there are a variety of conditions that can block,
  * everything will be done in a sort of continuation-passing style.
+ *
  * When the execution has to block to delay processing, for example to
  * allow system to recover because of memory shortage (via shared memory
  * callback), the return value of a continuation can be set to NULL. In that
  * case, the thread will go back to sleeping and wait for the proper
  * condition before it starts processing requests again from where it left.
- * Continuation state is "stored" in the xbdback instance (xbdi_cont and
+ * Continuation state is "stored" in the xbdback instance (xbdi_cont),
- * xbdi_cont_aux), and should only be manipulated by the instance thread.
+ * and should only be manipulated by the instance thread.
+ *
  * As xbdback(4) has to handle different sort of asynchronous events (Xen
  * event channels, biointr() soft interrupts, xenbus commands), the xbdi_lock
  * mutex is used to protect specific elements of the xbdback instance from
  * concurrent access: thread status and ring access (when pushing responses).
+ *
  * Here's how the call graph is supposed to be for a single I/O:
+ *
  * xbdback_co_main()
- *        |
+ *        |               --> xbdback_co_cache_flush()
- *        |               --> xbdback_co_cache_doflush() or NULL
+ *        |               |    |
- *        |               |
+ *        |               |    -> xbdback_co_cache_doflush() or NULL
- *        |               - xbdback_co_cache_flush2() <- xbdback_co_do_io() <-
+ *        |               |        |
- *        |                                            |                     |
+ *        |               |        -> xbdback_co_do_io()
  *        |               |-> xbdback_co_cache_flush() -> xbdback_co_map_io()-
  * xbdback_co_main_loop()-|
- *        |               |-> xbdback_co_main_done() ---> xbdback_co_map_io()-
+ *        |               |-> xbdback_co_main_done2() or NULL
  *        |                                           |                      |
  *        |               -- xbdback_co_main_done2() <-- xbdback_co_do_io() <-
  *        |               |
- *        |               --> xbdback_co_main() or NULL
+ *        |               --> xbdback_co_main_incr() -> xbdback_co_main_loop()
  *        |
  *     xbdback_co_io() -> xbdback_co_main_incr() -> xbdback_co_main_loop()
  *        |
- *     xbdback_co_io_gotreq()--+--> xbdback_co_map_io() ---
+ *     xbdback_co_io_gotio() -> xbdback_map_shm()
- *        |                    |                          |
+ *        |                     |
- *  -> xbdback_co_io_loop()----|  <- xbdback_co_do_io() <--
+ *        |                     xbdback_co_main_incr() -> xbdback_co_main_loop()
- *  |     |     |     |
+ *        |
- *  |     |     |     |----------> xbdback_co_io_gotio()
+ *     xbdback_co_do_io()
  *  |     |     |                         |
  *  |     |   xbdback_co_main_incr()      |
  *  |     |     |                         |
  *  |     |   xbdback_co_main_loop()      |
  *  |     |                               |
  *  |  xbdback_co_io_gotio2() <-----------|
  *  |     |           |
  *  |     |           |----------> xbdback_co_io_gotfrag()
  *  |     |                               |
  *  -- xbdback_co_io_gotfrag2() <---------|
  *        |
  *     xbdback_co_main_incr() -> xbdback_co_main_loop()
  */
 typedef void *(* xbdback_cont_t)(struct xbdback_instance *, void *);
 enum xbdi_proto {
 	XBDIP_NATIVE,
 	XBDIP_32,
 	XBDIP_64
 };
 struct xbdback_va {
 	SLIST_ENTRY(xbdback_va) xv_next;
 @@ -182,218 +167,161 @@ struct xbdback_instance {
 	/* private parameters for communication */
 	blkif_back_ring_proto_t xbdi_ring;
 	enum xbdi_proto xbdi_proto;
 	grant_handle_t xbdi_ring_handle; /* to unmap the ring */
 	vaddr_t xbdi_ring_va; /* to unmap the ring */
 	/* disconnection must be postponed until all I/O is done */
 	int xbdi_refcnt;
 	/*
 	 * State for I/O processing/coalescing follows; this has to
 	 * live here instead of on the stack because of the
 	 * continuation-ness (see above).
 	 */
 	RING_IDX xbdi_req_prod; /* limit on request indices */
-	xbdback_cont_t xbdi_cont, xbdi_cont_aux;
+	xbdback_cont_t xbdi_cont;
 	/* _request state: track requests fetched from ring */
 	struct xbdback_request *xbdi_req; /* if NULL, ignore following */
 	blkif_request_t xbdi_xen_req;
 	int xbdi_segno;
 	/* _io state: I/O associated to this instance */
-	struct xbdback_io *xbdi_io; /* if NULL, ignore next field */
+	struct xbdback_io *xbdi_io;
 	daddr_t xbdi_next_sector;
 	uint8_t xbdi_last_fs, xbdi_this_fs; /* first sectors */
 	uint8_t xbdi_last_ls, xbdi_this_ls; /* last sectors */
 	grant_ref_t xbdi_thisgrt, xbdi_lastgrt; /* grants */
 	/* other state */
 	int xbdi_same_page; /* are we merging two segments on the same page? */
 	uint xbdi_pendingreqs; /* number of I/O in fly */
 	struct timeval xbdi_lasterr_time;    /* error time tracking */
 #ifdef DEBUG
 	struct timeval xbdi_lastfragio_time; /* fragmented I/O tracking */
 #endif
 };
 /* Manipulation of the above reference count. */
 #define xbdi_get(xbdip) atomic_inc_uint(&(xbdip)->xbdi_refcnt)
 #define xbdi_put(xbdip)                                      \
 do {                                                         \
 	if (atomic_dec_uint_nv(&(xbdip)->xbdi_refcnt) == 0)  \
                xbdback_finish_disconnect(xbdip);             \
 } while (/* CONSTCOND */ 0)
 static SLIST_HEAD(, xbdback_instance) xbdback_instances;
 static kmutex_t xbdback_lock;
 /*
  * For each request from a guest, a xbdback_request is allocated from
  * a pool.  This will describe the request until completion.  The
  * request may require multiple IO operations to perform, so the
  * per-IO information is not stored here.
  */
 struct xbdback_request {
 	struct xbdback_instance *rq_xbdi; /* our xbd instance */
 	uint64_t rq_id;
 	int rq_iocount; /* reference count; or, number of outstanding I/O's */
 	int rq_ioerrs;
 	uint8_t rq_operation;
 };
 /*
  * For each I/O operation associated with one of those requests, an
  * xbdback_io is allocated from a pool.  It may correspond to multiple
  * Xen disk requests, or parts of them, if several arrive at once that
  * can be coalesced.
  */
 struct xbdback_io {
 	/* The instance pointer is duplicated for convenience. */
 	struct xbdback_instance *xio_xbdi; /* our xbd instance */
 	uint8_t xio_operation;
 	uint64_t xio_id;
 	union {
 		struct {
 			struct buf xio_buf; /* our I/O */
 			/* xbd requests involved */
 			SLIST_HEAD(, xbdback_fragment) xio_rq;
 			/* the virtual address to map the request at */
 			vaddr_t xio_vaddr;
 			struct xbdback_va *xio_xv;
 			vaddr_t xio_start_offset;	/* I/O start offset */
 			/* grants to map */
 			grant_ref_t xio_gref[XENSHM_MAX_PAGES_PER_REQUEST];
 			/* grants release */
 			grant_handle_t xio_gh[XENSHM_MAX_PAGES_PER_REQUEST];
 			uint16_t xio_nrma; /* number of guest pages */
 			uint16_t xio_mapped; /* == 1: grants are mapped */
 		} xio_rw;
 		uint64_t xio_flush_id;
 	} u;
 };
 #define xio_buf		u.xio_rw.xio_buf
 #define xio_rq		u.xio_rw.xio_rq
 #define xio_vaddr	u.xio_rw.xio_vaddr
 #define xio_start_offset	u.xio_rw.xio_start_offset
 #define xio_xv		u.xio_rw.xio_xv
 #define xio_gref	u.xio_rw.xio_gref
 #define xio_gh		u.xio_rw.xio_gh
 #define xio_nrma	u.xio_rw.xio_nrma
 #define xio_mapped	u.xio_rw.xio_mapped
 #define xio_flush_id	u.xio_flush_id
 /*
  * Rather than having the xbdback_io keep an array of the
  * xbdback_requests involved, since the actual number will probably be
  * small but might be as large as BLKIF_RING_SIZE, use a list.  This
  * would be threaded through xbdback_request, but one of them might be
  * part of multiple I/O's, alas.
  */
 struct xbdback_fragment {
 	struct xbdback_request *car;
 	SLIST_ENTRY(xbdback_fragment) cdr;
 };
 /*
  * Pools to manage the chain of block requests and I/Os fragments
  * submitted by frontend.
  */
-/* XXXSMP */
+static struct pool_cache xbdback_io_pool;
 static struct xbdback_pool {
 	struct pool_cache pc;
 	struct timeval last_warning;
 } xbdback_request_pool, xbdback_io_pool, xbdback_fragment_pool;
 /* Interval between reports of I/O errors from frontend */
 static const struct timeval xbdback_err_intvl = { 1, 0 };
 #ifdef DEBUG
 static const struct timeval xbdback_fragio_intvl = { 60, 0 };
 #endif
        void xbdbackattach(int);
 static int  xbdback_xenbus_create(struct xenbus_device *);
 static int  xbdback_xenbus_destroy(void *);
 static void xbdback_frontend_changed(void *, XenbusState);
 static void xbdback_backend_changed(struct xenbus_watch *,
     const char **, unsigned int);
 static int  xbdback_evthandler(void *);
 static int  xbdback_connect(struct xbdback_instance *);
 static void xbdback_disconnect(struct xbdback_instance *);
 static void xbdback_finish_disconnect(struct xbdback_instance *);
 static bool xbdif_lookup(domid_t, uint32_t);
 static void *xbdback_co_main(struct xbdback_instance *, void *);
 static void *xbdback_co_main_loop(struct xbdback_instance *, void *);
 static void *xbdback_co_main_incr(struct xbdback_instance *, void *);
 static void *xbdback_co_main_done(struct xbdback_instance *, void *);
 static void *xbdback_co_main_done2(struct xbdback_instance *, void *);
 static void *xbdback_co_cache_flush(struct xbdback_instance *, void *);
 static void *xbdback_co_cache_flush2(struct xbdback_instance *, void *);
 static void *xbdback_co_cache_doflush(struct xbdback_instance *, void *);
 static void *xbdback_co_io(struct xbdback_instance *, void *);
 static void *xbdback_co_io_gotreq(struct xbdback_instance *, void *);
 static void *xbdback_co_io_loop(struct xbdback_instance *, void *);
 static void *xbdback_co_io_gotio(struct xbdback_instance *, void *);
 static void *xbdback_co_io_gotio2(struct xbdback_instance *, void *);
 static void *xbdback_co_io_gotfrag(struct xbdback_instance *, void *);
 static void *xbdback_co_io_gotfrag2(struct xbdback_instance *, void *);
 static void *xbdback_co_map_io(struct xbdback_instance *, void *);
 static void *xbdback_co_do_io(struct xbdback_instance *, void *);
 static void xbdback_io_error(struct xbdback_io *, int);
 static void xbdback_iodone(struct buf *);
 static void xbdback_send_reply(struct xbdback_instance *, uint64_t , int , int);
 static void *xbdback_map_shm(struct xbdback_io *);
 static void xbdback_unmap_shm(struct xbdback_io *);
-static void *xbdback_pool_get(struct xbdback_pool *,
+static void *xbdback_pool_get(struct pool_cache *,
 			      struct xbdback_instance *);
-static void xbdback_pool_put(struct xbdback_pool *, void *);
+static void xbdback_pool_put(struct pool_cache *, void *);
 static void xbdback_thread(void *);
 static void xbdback_wakeup_thread(struct xbdback_instance *);
 static void xbdback_trampoline(struct xbdback_instance *, void *);
 static struct xenbus_backend_driver xbd_backend_driver = {
 	.xbakd_create = xbdback_xenbus_create,
 	.xbakd_type = "vbd"
 };
 void
 xbdbackattach(int n)
+{
 	XENPRINTF(("xbdbackattach\n"));
 	/*
 	 * initialize the backend driver, register the control message handler
 	 * and send driver up message.
 	 */
 	SLIST_INIT(&xbdback_instances);
 	mutex_init(&xbdback_lock, MUTEX_DEFAULT, IPL_NONE);
-	pool_cache_bootstrap(&xbdback_request_pool.pc,
+	pool_cache_bootstrap(&xbdback_io_pool,
 	    sizeof(struct xbdback_request), 0, 0, 0, "xbbrp", NULL,
 	    IPL_SOFTBIO, NULL, NULL, NULL);
 	pool_cache_bootstrap(&xbdback_io_pool.pc,
 	    sizeof(struct xbdback_io), 0, 0, 0, "xbbip", NULL,
 	    IPL_SOFTBIO, NULL, NULL, NULL);
 	pool_cache_bootstrap(&xbdback_fragment_pool.pc,
 	    sizeof(struct xbdback_fragment), 0, 0, 0, "xbbfp", NULL,
 	    IPL_SOFTBIO, NULL, NULL, NULL);
 	/* we allocate enough to handle a whole ring at once */
-	pool_prime(&xbdback_request_pool.pc.pc_pool, BLKIF_RING_SIZE);
+	pool_prime(&xbdback_io_pool.pc_pool, BLKIF_RING_SIZE);
 	pool_prime(&xbdback_io_pool.pc.pc_pool, BLKIF_RING_SIZE);
 	pool_prime(&xbdback_fragment_pool.pc.pc_pool,
             BLKIF_MAX_SEGMENTS_PER_REQUEST * BLKIF_RING_SIZE);
 	xenbus_backend_register(&xbd_backend_driver);
+}
 static int
 xbdback_xenbus_create(struct xenbus_device *xbusd)
+{
 	struct xbdback_instance *xbdi;
 	long domid, handle;
 	int error, i;
 	char *ep;
 	if ((error = xenbus_read_ul(NULL, xbusd->xbusd_path,
 @@ -1064,27 +992,28 @@ xbdback_co_main_loop(struct xbdback_inst
 			break;
 		default:
 			if (ratecheck(&xbdi->xbdi_lasterr_time,
 			    &xbdback_err_intvl)) {
 				printf("%s: unknown operation %d\n",
 				    xbdi->xbdi_name, req->operation);
+			}
 			xbdback_send_reply(xbdi, req->id, req->operation,
 			    BLKIF_RSP_ERROR);
 			xbdi->xbdi_cont = xbdback_co_main_incr;
 			break;
+		}
 	} else {
-		xbdi->xbdi_cont = xbdback_co_main_done;
+		KASSERT(xbdi->xbdi_io == NULL);
 		xbdi->xbdi_cont = xbdback_co_main_done2;
+	}
 	return xbdi;
+}
 /*
  * Increment consumer index and move on to the next request. In case
  * we want to disconnect, leave continuation now.
  */
 static void *
 xbdback_co_main_incr(struct xbdback_instance *xbdi, void *obj)
+{
 	(void)obj;
 	blkif_back_ring_t *ring = &xbdi->xbdi_ring.ring_n;
 @@ -1102,113 +1031,74 @@ xbdback_co_main_incr(struct xbdback_inst
 		xbdi->xbdi_cont = xbdback_co_main_loop;
 	/*
 	 * Each time the thread processes a full ring of requests, give
 	 * a chance to other threads to process I/Os too
 	 */
 	if ((ring->req_cons % BLKIF_RING_SIZE) == 0)
 		yield();
 	return xbdi;
+}
 /*
  * Ring processing is over. If there are any I/O still present for this
  * instance, handle them first.
  */
 static void *
 xbdback_co_main_done(struct xbdback_instance *xbdi, void *obj)
 	(void)obj;
 	if (xbdi->xbdi_io != NULL) {
 		KASSERT(xbdi->xbdi_io->xio_operation == BLKIF_OP_READ ||
 		    xbdi->xbdi_io->xio_operation == BLKIF_OP_WRITE);
 		xbdi->xbdi_cont = xbdback_co_map_io;
 		xbdi->xbdi_cont_aux = xbdback_co_main_done2;
 	} else {
 		xbdi->xbdi_cont = xbdback_co_main_done2;
 	return xbdi;
 /*
  * Check for requests in the instance's ring. In case there are, start again
  * from the beginning. If not, stall.
  */
 static void *
 xbdback_co_main_done2(struct xbdback_instance *xbdi, void *obj)
+{
 	int work_to_do;
 	KASSERT(xbdi->xbdio_io == NULL);
 	RING_FINAL_CHECK_FOR_REQUESTS(&xbdi->xbdi_ring.ring_n, work_to_do);
 	if (work_to_do)
 		xbdi->xbdi_cont = xbdback_co_main;
 	else
 		xbdi->xbdi_cont = NULL;
 	return xbdi;
+}
 /*
  * Frontend requested a cache flush operation.
  */
 static void *
-xbdback_co_cache_flush(struct xbdback_instance *xbdi, void *obj)
+xbdback_co_cache_flush(struct xbdback_instance *xbdi, void *obj __unused)
 	(void)obj;
 	XENPRINTF(("xbdback_co_cache_flush %p %p\n", xbdi, obj));
 	if (xbdi->xbdi_io != NULL) {
 		/* Some I/Os are required for this instance. Process them. */
 		KASSERT(xbdi->xbdi_io->xio_operation == BLKIF_OP_READ ||
 		    xbdi->xbdi_io->xio_operation == BLKIF_OP_WRITE);
 		KASSERT(xbdi->xbdi_pendingreqs > 0);
 		xbdi->xbdi_cont = xbdback_co_map_io;
 		xbdi->xbdi_cont_aux = xbdback_co_cache_flush2;
 	} else {
 		xbdi->xbdi_cont = xbdback_co_cache_flush2;
 	return xbdi;
 static void *
 xbdback_co_cache_flush2(struct xbdback_instance *xbdi, void *obj)
+{
 	(void)obj;
 	XENPRINTF(("xbdback_co_cache_flush2 %p %p\n", xbdi, obj));
 	if (xbdi->xbdi_pendingreqs > 0) {
 		/*
 		 * There are pending requests.
 		 * Event or iodone() will restart processing
 		 */
 		xbdi->xbdi_cont = NULL;
 		xbdi_put(xbdi);
 		return NULL;
+	}
 	xbdi->xbdi_cont = xbdback_co_cache_doflush;
 	return xbdback_pool_get(&xbdback_io_pool, xbdi);
+}
 /* Start the flush work */
 static void *
 xbdback_co_cache_doflush(struct xbdback_instance *xbdi, void *obj)
+{
 	struct xbdback_io *xbd_io;
 	XENPRINTF(("xbdback_co_cache_doflush %p %p\n", xbdi, obj));
 	xbd_io = xbdi->xbdi_io = obj;
 	xbd_io->xio_xbdi = xbdi;
 	xbd_io->xio_operation = xbdi->xbdi_xen_req.operation;
-	xbd_io->xio_flush_id = xbdi->xbdi_xen_req.id;
+	xbd_io->xio_id = xbdi->xbdi_xen_req.id;
 	xbdi->xbdi_cont = xbdback_co_do_io;
 	return xbdi;
+}
 /*
  * A read or write I/O request must be processed. Do some checks first,
  * then get the segment information directly from the ring request.
  */
 static void *
 xbdback_co_io(struct xbdback_instance *xbdi, void *obj)
+{
 	int i, error;
 	blkif_request_t *req;
 @@ -1230,461 +1120,212 @@ xbdback_co_io(struct xbdback_instance *x
 		error = EINVAL;
 		goto end;
+	}
 	KASSERT(req->operation == BLKIF_OP_READ ||
 	    req->operation == BLKIF_OP_WRITE);
 	if (req->operation == BLKIF_OP_WRITE) {
 		if (xbdi->xbdi_ro) {
 			error = EROFS;
 			goto end;
+		}
+	}
 	xbdi->xbdi_segno = 0;
 	/* copy request segments */
 	switch(xbdi->xbdi_proto) {
 	case XBDIP_NATIVE:
 		/* already copied in xbdback_co_main_loop */
 		break;
 	case XBDIP_32:
 		req32 = RING_GET_REQUEST(&xbdi->xbdi_ring.ring_32,
 		    xbdi->xbdi_ring.ring_n.req_cons);
 		for (i = 0; i < req->nr_segments; i++)
 			req->seg[i] = req32->seg[i];
 		break;
 	case XBDIP_64:
 		req64 = RING_GET_REQUEST(&xbdi->xbdi_ring.ring_64,
 		    xbdi->xbdi_ring.ring_n.req_cons);
 		for (i = 0; i < req->nr_segments; i++)
 			req->seg[i] = req64->seg[i];
 		break;
+	}
-	xbdi->xbdi_cont = xbdback_co_io_gotreq;
+	KASSERT(xbdi->xbdi_io == NULL);
-	return xbdback_pool_get(&xbdback_request_pool, xbdi);
+	xbdi->xbdi_cont = xbdback_co_io_gotio;
 	return xbdback_pool_get(&xbdback_io_pool, xbdi);
  end:
 	xbdback_send_reply(xbdi, xbdi->xbdi_xen_req.id,
-	    xbdi->xbdi_xen_req.operation, error);
+	    xbdi->xbdi_xen_req.operation,
 	    (error == EROFS) ? BLKIF_RSP_EOPNOTSUPP : BLKIF_RSP_ERROR);
 	xbdi->xbdi_cont = xbdback_co_main_incr;
 	return xbdi;
+}
 /*
  * We have fetched segment requests from the ring. In case there are already
  * I/Os prepared for this instance, we can try coalescing the requests
  * with these I/Os.
  */
 static void *
 xbdback_co_io_gotreq(struct xbdback_instance *xbdi, void *obj)
 	struct xbdback_request *xrq;
 	xrq = xbdi->xbdi_req = obj;
 	xrq->rq_xbdi = xbdi;
 	xrq->rq_iocount = 0;
 	xrq->rq_ioerrs = 0;
 	xrq->rq_id = xbdi->xbdi_xen_req.id;
 	xrq->rq_operation = xbdi->xbdi_xen_req.operation;
 	KASSERT(xbdi->xbdi_req->rq_operation == BLKIF_OP_READ ||
 	    xbdi->xbdi_req->rq_operation == BLKIF_OP_WRITE);
 	/*
 	 * Request-level reasons not to coalesce: different device,
 	 * different op, or noncontiguous disk sectors (vs. previous
 	 * request handed to us).
 	 */
 	xbdi->xbdi_cont = xbdback_co_io_loop;
 	if (xbdi->xbdi_io != NULL) {
 		struct xbdback_request *last_req;
 		last_req = SLIST_FIRST(&xbdi->xbdi_io->xio_rq)->car;
 		XENPRINTF(("xbdback_io domain %d: hoping for sector %" PRIu64
 		    "; got %" PRIu64 "\n", xbdi->xbdi_domid,
 		    xbdi->xbdi_next_sector,
 		    xbdi->xbdi_xen_req.sector_number));
 		if ((xrq->rq_operation != last_req->rq_operation)
 		    || (xbdi->xbdi_xen_req.sector_number !=
 		    xbdi->xbdi_next_sector)) {
 			XENPRINTF(("xbdback_io domain %d: segment break\n",
 			    xbdi->xbdi_domid));
 			xbdi->xbdi_next_sector =
 			    xbdi->xbdi_xen_req.sector_number;
 			KASSERT(xbdi->xbdi_io->xio_operation == BLKIF_OP_READ ||
 			    xbdi->xbdi_io->xio_operation == BLKIF_OP_WRITE);
 			xbdi->xbdi_cont_aux = xbdback_co_io_loop;
 			xbdi->xbdi_cont = xbdback_co_map_io;
 	} else {
 		xbdi->xbdi_next_sector = xbdi->xbdi_xen_req.sector_number;
 	return xbdi;
 /* Handle coalescing of multiple segment requests into one I/O work */
 static void *
 xbdback_co_io_loop(struct xbdback_instance *xbdi, void *obj)
 	(void)obj;
 	KASSERT(xbdi->xbdi_req->rq_operation == BLKIF_OP_READ ||
 	    xbdi->xbdi_req->rq_operation == BLKIF_OP_WRITE);
 	if (xbdi->xbdi_segno < xbdi->xbdi_xen_req.nr_segments) {
 		uint8_t this_fs, this_ls, last_ls;
 		grant_ref_t thisgrt;
 		/*
 		 * Segment-level reason to coalesce: handling full
 		 * pages, or adjacent sector ranges from the same page
 		 * (and yes, this latter does happen).  But not if the
 		 * array of client pseudo-physical pages is full.
 		 */
 		this_fs = xbdi->xbdi_xen_req.seg[xbdi->xbdi_segno].first_sect;
 		this_ls = xbdi->xbdi_xen_req.seg[xbdi->xbdi_segno].last_sect;
 		thisgrt = xbdi->xbdi_xen_req.seg[xbdi->xbdi_segno].gref;
 		XENPRINTF(("xbdback_io domain %d: "
 			   "first,last_sect[%d]=0%o,0%o\n",
 			   xbdi->xbdi_domid, xbdi->xbdi_segno,
 			   this_fs, this_ls));
 		last_ls = xbdi->xbdi_last_ls = xbdi->xbdi_this_ls;
 		xbdi->xbdi_this_fs = this_fs;
 		xbdi->xbdi_this_ls = this_ls;
 		xbdi->xbdi_thisgrt = thisgrt;
 		if (xbdi->xbdi_io != NULL) {
 			if (last_ls == VBD_MAXSECT
 			    && this_fs == 0
 			    && xbdi->xbdi_io->xio_nrma
 			    < XENSHM_MAX_PAGES_PER_REQUEST) {
 				xbdi->xbdi_same_page = 0;
 			} else if (last_ls + 1
 				       == this_fs
 #ifdef notyet
 				   && (last_fas & ~PAGE_MASK)
 				       == (this_fas & ~PAGE_MASK)
 #else
 				  && 0 /* can't know frame number yet */
 #endif
 			    ) {
 #ifdef DEBUG
 				if (ratecheck(&xbdi->xbdi_lastfragio_time,
 				    &xbdback_fragio_intvl))
 					printf("%s: domain is sending"
 					    " excessively fragmented I/O\n",
 					    xbdi->xbdi_name);
 #endif
 				printf("xbdback_io: would maybe glue "
 				    "same page sec %d (%d->%d)\n",
 				    xbdi->xbdi_segno, this_fs, this_ls);
 				XENPRINTF(("xbdback_io domain %d: glue same "
 				    "page", xbdi->xbdi_domid));
 				panic("notyet!");
 				xbdi->xbdi_same_page = 1;
 			} else {
 				KASSERT(xbdi->xbdi_io->xio_operation ==
 				     BLKIF_OP_READ ||
 				    xbdi->xbdi_io->xio_operation ==
 				     BLKIF_OP_WRITE);
 				xbdi->xbdi_cont_aux = xbdback_co_io_loop;
 				xbdi->xbdi_cont = xbdback_co_map_io;
 				return xbdi;
 		} else
 			xbdi->xbdi_same_page = 0;
 		if (xbdi->xbdi_io == NULL) {
 			xbdi->xbdi_cont = xbdback_co_io_gotio;
 			return xbdback_pool_get(&xbdback_io_pool, xbdi);
 		} else {
 			xbdi->xbdi_cont = xbdback_co_io_gotio2;
 	} else {
 		/* done with the loop over segments; get next request */
 		xbdi->xbdi_cont = xbdback_co_main_incr;
 	return xbdi;
 /* Prepare an I/O buffer for a xbdback instance */
 static void *
 xbdback_co_io_gotio(struct xbdback_instance *xbdi, void *obj)
+{
 	struct xbdback_io *xbd_io;
 	vaddr_t start_offset; /* start offset in vm area */
 	int buf_flags;
 	size_t bcount;
 	blkif_request_t *req;
 	xbdi_get(xbdi);
 	atomic_inc_uint(&xbdi->xbdi_pendingreqs);
 	req = &xbdi->xbdi_xen_req;
 	xbd_io = xbdi->xbdi_io = obj;
 	memset(xbd_io, 0, sizeof(*xbd_io));
 	buf_init(&xbd_io->xio_buf);
 	xbd_io->xio_xbdi = xbdi;
-	SLIST_INIT(&xbd_io->xio_rq);
+	xbd_io->xio_operation = req->operation;
-	xbd_io->xio_nrma = 0;
+	xbd_io->xio_id = req->id;
 	xbd_io->xio_mapped = 0;
 	xbd_io->xio_operation = xbdi->xbdi_xen_req.operation;
-	start_offset = xbdi->xbdi_this_fs * VBD_BSIZE;
+	/* Process segments */
-	KASSERT(start_offset < PAGE_SIZE);
+	bcount = 0;
 	for (int i = 0; i < req->nr_segments; i++) {
 		xbd_io->xio_gref[i] = req->seg[i].gref;
 		bcount += (req->seg[i].last_sect - req->seg[i].first_sect + 1)
 			* VBD_BSIZE;
+	}
 	KASSERT(bcount <= MAXPHYS);
 	xbd_io->xio_nrma = req->nr_segments;
 	xbd_io->xio_start_offset = req->seg[0].first_sect * VBD_BSIZE;
 	KASSERT(xbd_io->xio_start_offset < PAGE_SIZE);
 	KASSERT(bcount + xbd_io->xio_start_offset < VBD_VA_SIZE);
 	if (xbdi->xbdi_xen_req.operation == BLKIF_OP_WRITE) {
 		buf_flags = B_WRITE;
 	} else {
 		buf_flags = B_READ;
+	}
 	xbd_io->xio_buf.b_flags = buf_flags;
 	xbd_io->xio_buf.b_cflags = 0;
 	xbd_io->xio_buf.b_oflags = 0;
 	xbd_io->xio_buf.b_iodone = xbdback_iodone;
 	xbd_io->xio_buf.b_proc = NULL;
 	xbd_io->xio_buf.b_vp = xbdi->xbdi_vp;
 	xbd_io->xio_buf.b_objlock = xbdi->xbdi_vp->v_interlock;
 	xbd_io->xio_buf.b_dev = xbdi->xbdi_dev;
-	xbd_io->xio_buf.b_blkno = xbdi->xbdi_next_sector;
+	xbd_io->xio_buf.b_blkno = req->sector_number;
-	xbd_io->xio_buf.b_bcount = 0;
+	xbd_io->xio_buf.b_bcount = bcount;
-	xbd_io->xio_buf.b_data = (void *)start_offset;
+	xbd_io->xio_buf.b_data = NULL;
 	xbd_io->xio_buf.b_private = xbd_io;
 	xbdi->xbdi_cont = xbdback_co_io_gotio2;
 	return xbdi;
 /* Manage fragments */
 static void *
 xbdback_co_io_gotio2(struct xbdback_instance *xbdi, void *obj)
 	(void)obj;
 	if (xbdi->xbdi_segno == 0 || SLIST_EMPTY(&xbdi->xbdi_io->xio_rq)) {
 		/* if this is the first segment of a new request */
 		/* or if it's the first segment of the io */
 		xbdi->xbdi_cont = xbdback_co_io_gotfrag;
 		return xbdback_pool_get(&xbdback_fragment_pool, xbdi);
 	xbdi->xbdi_cont = xbdback_co_io_gotfrag2;
 	return xbdi;
 /* Prepare the instance for its first fragment */
 static void *
 xbdback_co_io_gotfrag(struct xbdback_instance *xbdi, void *obj)
 	struct xbdback_fragment *xbd_fr;
 	xbd_fr = obj;
 	xbd_fr->car = xbdi->xbdi_req;
 	SLIST_INSERT_HEAD(&xbdi->xbdi_io->xio_rq, xbd_fr, cdr);
 	++xbdi->xbdi_req->rq_iocount;
 	xbdi->xbdi_cont = xbdback_co_io_gotfrag2;
 	return xbdi;
 /* Last routine to manage segments fragments for one I/O */
 static void *
 xbdback_co_io_gotfrag2(struct xbdback_instance *xbdi, void *obj)
 	struct xbdback_io *xbd_io;
 	int seg_size;
 	uint8_t this_fs, this_ls;
 	this_fs = xbdi->xbdi_this_fs;
 	this_ls = xbdi->xbdi_this_ls;
 	xbd_io = xbdi->xbdi_io;
 	seg_size = this_ls - this_fs + 1;
 	if (seg_size < 0) {
 		if (ratecheck(&xbdi->xbdi_lasterr_time, &xbdback_err_intvl)) {
 			printf("xbdback_io domain %d: negative-size request "
 			    "(%d %d)\n",
 			    xbdi->xbdi_domid, this_ls, this_fs);
 		xbdback_io_error(xbdi->xbdi_io, EINVAL);
 		xbdi->xbdi_io = NULL;
 		xbdi->xbdi_cont = xbdback_co_main_incr;
 		return xbdi;
 	if (!xbdi->xbdi_same_page) {
 		XENPRINTF(("xbdback_io domain %d: appending grant %u\n",
 			   xbdi->xbdi_domid, (u_int)xbdi->xbdi_thisgrt));
 		xbd_io->xio_gref[xbd_io->xio_nrma++] = xbdi->xbdi_thisgrt;
 	xbd_io->xio_buf.b_bcount += (daddr_t)(seg_size * VBD_BSIZE);
 	XENPRINTF(("xbdback_io domain %d: start sect %ld size %d\n",
 	    xbdi->xbdi_domid, (long)xbdi->xbdi_next_sector, seg_size));
 	/* Finally, the end of the segment loop! */
 	xbdi->xbdi_next_sector += seg_size;
 	++xbdi->xbdi_segno;
 	xbdi->xbdi_cont = xbdback_co_io_loop;
 	return xbdi;
 /*
  * Map the different I/O requests in backend's VA space.
  */
 static void *
 xbdback_co_map_io(struct xbdback_instance *xbdi, void *obj)
 	(void)obj;
 	XENPRINTF(("xbdback_io domain %d: flush sect %ld size %d ptr 0x%lx\n",
 	    xbdi->xbdi_domid, (long)xbdi->xbdi_io->xio_buf.b_blkno,
 	    (int)xbdi->xbdi_io->xio_buf.b_bcount, (long)xbdi->xbdi_io));
 	xbdi->xbdi_cont = xbdback_co_do_io;
 	return xbdback_map_shm(xbdi->xbdi_io);
+}
 static void
 xbdback_io_error(struct xbdback_io *xbd_io, int error)
+{
 	xbd_io->xio_buf.b_error = error;
 	xbdback_iodone(&xbd_io->xio_buf);
+}
 /*
  * Main xbdback I/O routine. It can either perform a flush operation or
  * schedule a read/write operation.
  */
 static void *
 xbdback_co_do_io(struct xbdback_instance *xbdi, void *obj)
+{
 	struct xbdback_io *xbd_io = xbdi->xbdi_io;
 	vaddr_t start_offset;
 	int nsegs __diagused;
 	switch (xbd_io->xio_operation) {
 	case BLKIF_OP_FLUSH_DISKCACHE:
+	{
 		int error;
 		int force = 1;
 		error = VOP_IOCTL(xbdi->xbdi_vp, DIOCCACHESYNC, &force, FWRITE,
 		    kauth_cred_get());
 		if (error) {
 			aprint_error("xbdback %s: DIOCCACHESYNC returned %d\n",
 			    xbdi->xbdi_xbusd->xbusd_path, error);
 			 if (error == EOPNOTSUPP || error == ENOTTY)
 				error = BLKIF_RSP_EOPNOTSUPP;
 			 else
 				error = BLKIF_RSP_ERROR;
 		} else
 			error = BLKIF_RSP_OKAY;
-		xbdback_send_reply(xbdi, xbd_io->xio_flush_id,
+		xbdback_send_reply(xbdi, xbd_io->xio_id,
 		    xbd_io->xio_operation, error);
 		xbdback_pool_put(&xbdback_io_pool, xbd_io);
 		xbdi_put(xbdi);
 		xbdi->xbdi_io = NULL;
 		xbdi->xbdi_cont = xbdback_co_main_incr;
 		return xbdi;
+	}
 	case BLKIF_OP_READ:
 	case BLKIF_OP_WRITE:
 		start_offset = (vaddr_t)xbd_io->xio_buf.b_data;
 		KASSERT(xbd_io->xio_buf.b_bcount + start_offset < VBD_VA_SIZE);
 		xbd_io->xio_buf.b_data = (void *)
-		    (start_offset + xbd_io->xio_vaddr);
+		    (xbd_io->xio_vaddr + xbd_io->xio_start_offset);
 #ifdef DIAGNOSTIC
 		nsegs = round_page(start_offset + xbd_io->xio_buf.b_bcount)
 		    >> PAGE_SHIFT;
 		if (nsegs > xbd_io->xio_nrma) {
 			printf("xbdback_co_do_io: vaddr %#" PRIxVADDR
 			    " bcount %#x doesn't fit in %d pages\n",
 			    start_offset, xbd_io->xio_buf.b_bcount,
 			    xbd_io->xio_nrma);
 			panic("xbdback_co_do_io: not enough pages");
 #endif
 		if ((xbd_io->xio_buf.b_flags & B_READ) == 0) {
 			mutex_enter(xbd_io->xio_buf.b_vp->v_interlock);
 			xbd_io->xio_buf.b_vp->v_numoutput++;
 			mutex_exit(xbd_io->xio_buf.b_vp->v_interlock);
+		}
 		bdev_strategy(&xbd_io->xio_buf);
 		/* will call xbdback_iodone() asynchronously when done */
 		bdev_strategy(&xbd_io->xio_buf);
 		xbdi->xbdi_io = NULL;
-		xbdi->xbdi_cont = xbdi->xbdi_cont_aux;
+		xbdi->xbdi_cont = xbdback_co_main_incr;
 		return xbdi;
 	default:
 		/* Should never happen */
 		panic("xbdback_co_do_io: unsupported operation %d",
 		    xbd_io->xio_operation);
+	}
+}
 /*
  * Called from softint(9) context when an I/O is done: for each request, send
  * back the associated reply to the domain.
+ *
  * This gets reused by xbdback_io_error to report errors from other sources.
  */
 static void
 xbdback_iodone(struct buf *bp)
+{
 	struct xbdback_io *xbd_io;
 	struct xbdback_instance *xbdi;
-	int errp;
+	int status;
 	KERNEL_LOCK(1, NULL);		/* XXXSMP */
 	xbd_io = bp->b_private;
 	xbdi = xbd_io->xio_xbdi;
 	XENPRINTF(("xbdback_io domain %d: iodone ptr 0x%lx\n",
 		   xbdi->xbdi_domid, (long)xbd_io));
-	if (xbd_io->xio_mapped == 1)
+	KASSERT(bp->b_error != 0 || xbd_io->xio_xv != NULL);
 	if (xbd_io->xio_xv != NULL)
 		xbdback_unmap_shm(xbd_io);
 	if (bp->b_error != 0) {
 		printf("xbd IO domain %d: error %d\n",
 		       xbdi->xbdi_domid, bp->b_error);
-		errp = 1;
+		status = BLKIF_RSP_ERROR;
 	} else
-		errp = 0;
+		status = BLKIF_RSP_OKAY;
-	/* for each constituent xbd request */
+	xbdback_send_reply(xbdi, xbd_io->xio_id, xbd_io->xio_operation, status);
 	while(!SLIST_EMPTY(&xbd_io->xio_rq)) {
 		struct xbdback_fragment *xbd_fr;
 		struct xbdback_request *xbd_req;
 		struct xbdback_instance *rxbdi __diagused;
 		int error;
 		xbd_fr = SLIST_FIRST(&xbd_io->xio_rq);
 		xbd_req = xbd_fr->car;
 		SLIST_REMOVE_HEAD(&xbd_io->xio_rq, cdr);
 		xbdback_pool_put(&xbdback_fragment_pool, xbd_fr);
 		if (errp)
 			++xbd_req->rq_ioerrs;
 		/* finalize it only if this was its last I/O */
 		if (--xbd_req->rq_iocount > 0)
 			continue;
 		rxbdi = xbd_req->rq_xbdi;
 		KASSERT(xbdi == rxbdi);
 		error = xbd_req->rq_ioerrs > 0
 		    ? BLKIF_RSP_ERROR
 		    : BLKIF_RSP_OKAY;
 		XENPRINTF(("xbdback_io domain %d: end request %"PRIu64
 		    " error=%d\n",
 		    xbdi->xbdi_domid, xbd_req->rq_id, error));
 		xbdback_send_reply(xbdi, xbd_req->rq_id,
 		    xbd_req->rq_operation, error);
 		xbdback_pool_put(&xbdback_request_pool, xbd_req);
 	xbdi_put(xbdi);
 	atomic_dec_uint(&xbdi->xbdi_pendingreqs);
 	buf_destroy(&xbd_io->xio_buf);
 	xbdback_pool_put(&xbdback_io_pool, xbd_io);
 	xbdback_wakeup_thread(xbdi);
 	KERNEL_UNLOCK_ONE(NULL);	/* XXXSMP */
+}
 /*
  * Wake up the per xbdback instance thread.
  */
 static void
 @@ -1749,62 +1390,56 @@ xbdback_send_reply(struct xbdback_instan
 		XENPRINTF(("xbdback_send_reply notify %d\n", xbdi->xbdi_domid));
 		hypervisor_notify_via_evtchn(xbdi->xbdi_evtchn);
+	}
+}
 /*
  * Map multiple entries of an I/O request into backend's VA space.
  * The xbd_io->xio_gref array has to be filled out by the caller.
  */
 static void *
 xbdback_map_shm(struct xbdback_io *xbd_io)
+{
 	struct xbdback_instance *xbdi = xbd_io->xio_xbdi;
 	struct xbdback_request *xbd_rq;
 	int error, s;
 #ifdef XENDEBUG_VBD
 	int i;
 	printf("xbdback_map_shm map grant ");
 	for (i = 0; i < xbd_io->xio_nrma; i++) {
 		printf("%u ", (u_int)xbd_io->xio_gref[i]);
+	}
 #endif
 	KASSERT(xbd_io->xio_mapped == 0);
 	s = splvm();	/* XXXSMP */
 	xbd_rq = SLIST_FIRST(&xbd_io->xio_rq)->car;
 	xbd_io->xio_xv = SLIST_FIRST(&xbdi->xbdi_va_free);
 	KASSERT(xbd_io->xio_xv != NULL);
 	SLIST_REMOVE_HEAD(&xbdi->xbdi_va_free, xv_next);
 	xbd_io->xio_vaddr = xbd_io->xio_xv->xv_vaddr;
 	splx(s);
 	error = xen_shm_map(xbd_io->xio_nrma, xbdi->xbdi_domid,
 	    xbd_io->xio_gref, xbd_io->xio_vaddr, xbd_io->xio_gh,
-	    (xbd_rq->rq_operation == BLKIF_OP_WRITE) ? XSHM_RO : 0);
+	    (xbd_io->xio_operation == BLKIF_OP_WRITE) ? XSHM_RO : 0);
 	switch(error) {
 	case 0:
 #ifdef XENDEBUG_VBD
 		printf("handle ");
 		for (i = 0; i < xbd_io->xio_nrma; i++) {
 			printf("%u ", (u_int)xbd_io->xio_gh[i]);
+		}
 		printf("\n");
 #endif
 		xbd_io->xio_mapped = 1;
 		return xbdi;
 	default:
 		if (ratecheck(&xbdi->xbdi_lasterr_time, &xbdback_err_intvl)) {
 			printf("xbdback_map_shm: xen_shm error %d ", error);
+		}
 		xbdback_io_error(xbdi->xbdi_io, error);
 		SLIST_INSERT_HEAD(&xbdi->xbdi_va_free, xbd_io->xio_xv, xv_next);
 		xbd_io->xio_xv = NULL;
 		xbdi->xbdi_io = NULL;
 		// do not retry
 		xbdi->xbdi_cont = xbdback_co_main_incr;
 		return xbdi;
+	}
 @@ -1815,48 +1450,47 @@ static void
 xbdback_unmap_shm(struct xbdback_io *xbd_io)
+{
 	struct xbdback_instance *xbdi = xbd_io->xio_xbdi;
 #ifdef XENDEBUG_VBD
 	int i;
 	printf("xbdback_unmap_shm handle ");
 	for (i = 0; i < xbd_io->xio_nrma; i++) {
 		printf("%u ", (u_int)xbd_io->xio_gh[i]);
+	}
 	printf("\n");
 #endif
-	KASSERT(xbd_io->xio_mapped == 1);
+	KASSERT(xbd_io->xio_xv != NULL);
 	xbd_io->xio_mapped = 0;
 	xen_shm_unmap(xbd_io->xio_vaddr, xbd_io->xio_nrma,
 	    xbd_io->xio_gh);
 	SLIST_INSERT_HEAD(&xbdi->xbdi_va_free, xbd_io->xio_xv, xv_next);
 	xbd_io->xio_xv = NULL;
 	xbd_io->xio_vaddr = -1;
+}
 /* Obtain memory from a pool */
 static void *
-xbdback_pool_get(struct xbdback_pool *pp,
+xbdback_pool_get(struct pool_cache *pc,
 			      struct xbdback_instance *xbdi)
+{
-	return pool_cache_get(&pp->pc, PR_WAITOK);
+	return pool_cache_get(pc, PR_WAITOK);
+}
 /* Restore memory to a pool */
 static void
-xbdback_pool_put(struct xbdback_pool *pp, void *item)
+xbdback_pool_put(struct pool_cache *pc, void *item)
+{
-	pool_cache_put(&pp->pc, item);
+	pool_cache_put(pc, item);
+}
 /*
  * Trampoline routine. Calls continuations in a loop and only exits when
  * either the returned object or the next callback is NULL.
  */
 static void
 xbdback_trampoline(struct xbdback_instance *xbdi, void *obj)
+{
 	xbdback_cont_t cont;
 	while(obj != NULL && xbdi->xbdi_cont != NULL) {
 		cont = xbdi->xbdi_cont;