 @@ -1,1376 +1,1370 @@
-/*      $NetBSD: xbd_xenbus.c,v 1.118 2020/04/17 10:35:06 jdolecek Exp $      */
+/*      $NetBSD: xbd_xenbus.c,v 1.119 2020/04/18 16:58:00 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.
+ *
  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  * 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.
+ *
  */
 /*
  * The file contains the xbd frontend code required for block-level
  * communications (similar to hard disks) between two Xen domains.
+ *
  * We are not supposed to receive solicitations spontaneously from backend. The
  * protocol is therefore fairly simple and uses only one ring to communicate
  * with backend: frontend posts requests to the ring then wait for their
  * replies asynchronously.
+ *
  * xbd follows NetBSD's disk(9) convention. At any time, a LWP can schedule
  * an operation request for the device (be it open(), read(), write(), ...).
  * Calls are typically processed that way:
  * - 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 1.118 2020/04/17 10:35:06 jdolecek Exp $");
+__KERNEL_RCSID(0, "$NetBSD: xbd_xenbus.c,v 1.119 2020/04/18 16:58:00 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>
 #include <sys/proc.h>
 #include <sys/systm.h>
 #include <sys/stat.h>
 #include <sys/vnode.h>
 #include <sys/mutex.h>
 #include <dev/dkvar.h>
 #include <uvm/uvm.h>
 #include <xen/hypervisor.h>
 #include <xen/evtchn.h>
 #include <xen/granttables.h>
 #include <xen/include/public/io/blkif.h>
 #include <xen/include/public/io/protocols.h>
 #include <xen/xenbus.h>
 #include "locators.h"
 #undef XBD_DEBUG
 #ifdef XBD_DEBUG
 #define DPRINTF(x) printf x;
 #else
 #define DPRINTF(x)
 #endif
 #define GRANT_INVALID_REF -1
 #define XBD_RING_SIZE __CONST_RING_SIZE(blkif, PAGE_SIZE)
 #define XBD_MAX_XFER (PAGE_SIZE * BLKIF_MAX_SEGMENTS_PER_REQUEST)
 #define XBD_MAX_CHUNK	32*1024		/* max I/O size we process in 1 req */
 #define XBD_XFER_LIMIT	(2*XBD_MAX_XFER)
 #define XEN_BSHIFT      9               /* log2(XEN_BSIZE) */
 #define XEN_BSIZE       (1 << XEN_BSHIFT)
 CTASSERT((MAXPHYS <= 2*XBD_MAX_CHUNK));
 CTASSERT(XEN_BSIZE == DEV_BSIZE);
 struct xbd_indirect {
 	SLIST_ENTRY(xbd_indirect) in_next;
 	struct blkif_request_segment *in_addr;
 	grant_ref_t in_gntref;
 };
 struct xbd_req {
 	SLIST_ENTRY(xbd_req) req_next;
 	uint16_t req_id; /* ID passed to backend */
 	bus_dmamap_t req_dmamap;
 	struct xbd_req *req_parent, *req_child;
 	bool req_parent_done;
 	union {
 	    struct {
 		grant_ref_t req_gntref[XBD_XFER_LIMIT >> PAGE_SHIFT];
 		struct buf *req_bp; /* buffer associated with this request */
 		void *req_data; /* pointer to the data buffer */
 		struct xbd_indirect *req_indirect;	/* indirect page */
 	    } req_rw;
 	    struct {
 		int s_error;
 		int s_done;
 	    } req_sync;
 	} u;
 };
 #define req_gntref	u.req_rw.req_gntref
 #define req_bp		u.req_rw.req_bp
 #define req_data	u.req_rw.req_data
 #define req_indirect	u.req_rw.req_indirect
 #define req_sync	u.req_sync
 struct xbd_xenbus_softc {
 	struct dk_softc sc_dksc;	/* Must be first in this struct */
 	struct xenbus_device *sc_xbusd;
 	unsigned int sc_evtchn;
 	struct intrhand *sc_ih; /* Interrupt handler for this instance. */
 	kmutex_t sc_lock;
 	kcondvar_t sc_cache_flush_cv;
 	kcondvar_t sc_req_cv;
 	kcondvar_t sc_detach_cv;
 	kcondvar_t sc_suspend_cv;
 	blkif_front_ring_t sc_ring;
 	grant_ref_t sc_ring_gntref;
 	struct xbd_req sc_reqs[XBD_RING_SIZE];
 	SLIST_HEAD(,xbd_req) sc_xbdreq_head; /* list of free requests */
 	struct xbd_indirect sc_indirect[XBD_RING_SIZE];
 	SLIST_HEAD(,xbd_indirect) sc_indirect_head;
 	vmem_addr_t sc_unalign_buffer;
 	struct xbd_req *sc_unalign_used;
 	int sc_backend_status; /* our status with backend */
 #define BLKIF_STATE_DISCONNECTED 0
 #define BLKIF_STATE_CONNECTED    1
 #define BLKIF_STATE_SUSPENDED    2
 	int sc_shutdown;
 #define BLKIF_SHUTDOWN_RUN    0 /* no shutdown */
 #define BLKIF_SHUTDOWN_REMOTE 1 /* backend-initiated shutdown in progress */
 #define BLKIF_SHUTDOWN_LOCAL  2 /* locally-initiated shutdown in progress */
 	uint64_t sc_sectors; /* number of sectors for this device */
 	u_long sc_secsize; /* sector size */
 	uint64_t sc_xbdsize; /* size of disk in DEV_BSIZE */
 	u_long sc_info; /* VDISK_* */
 	u_long sc_handle; /* from backend */
 	int sc_features;
 #define BLKIF_FEATURE_CACHE_FLUSH	0x1
 #define BLKIF_FEATURE_BARRIER		0x2
 #define BLKIF_FEATURE_PERSISTENT	0x4
 #define BLKIF_FEATURE_INDIRECT		0x8
 #define BLKIF_FEATURE_BITS		\
 	"\20\1CACHE-FLUSH\2BARRIER\3PERSISTENT\4INDIRECT"
 	struct evcnt sc_cnt_map_unalign;
 	struct evcnt sc_cnt_unalign_busy;
 	struct evcnt sc_cnt_queue_full;
 	struct evcnt sc_cnt_indirect;
 };
 static int  xbd_xenbus_match(device_t, cfdata_t, void *);
 static void xbd_xenbus_attach(device_t, device_t, void *);
 static int  xbd_xenbus_detach(device_t, int);
 static bool xbd_xenbus_suspend(device_t, const pmf_qual_t *);
 static bool xbd_xenbus_resume(device_t, const pmf_qual_t *);
 static int  xbd_handler(void *);
 static int  xbd_diskstart(device_t, struct buf *);
 static void xbd_iosize(device_t, int *);
 static void xbd_backend_changed(void *, XenbusState);
 static void xbd_connect(struct xbd_xenbus_softc *);
 static void xbd_features(struct xbd_xenbus_softc *);
 static void xbd_diskstart_submit(struct xbd_xenbus_softc *, int,
 	struct buf *bp, int, bus_dmamap_t, grant_ref_t *);
 static void xbd_diskstart_submit_indirect(struct xbd_xenbus_softc *,
 	struct xbd_req *, struct buf *bp);
 static int  xbd_map_align(struct xbd_xenbus_softc *, struct xbd_req *);
 static void xbd_unmap_align(struct xbd_xenbus_softc *, struct xbd_req *, bool);
 static void xbdminphys(struct buf *);
 CFATTACH_DECL3_NEW(xbd, sizeof(struct xbd_xenbus_softc),
     xbd_xenbus_match, xbd_xenbus_attach, xbd_xenbus_detach, NULL, NULL, NULL,
     DVF_DETACH_SHUTDOWN);
 dev_type_open(xbdopen);
 dev_type_close(xbdclose);
 dev_type_read(xbdread);
 dev_type_write(xbdwrite);
 dev_type_ioctl(xbdioctl);
 dev_type_strategy(xbdstrategy);
 dev_type_dump(xbddump);
 dev_type_size(xbdsize);
 const struct bdevsw xbd_bdevsw = {
 	.d_open = xbdopen,
 	.d_close = xbdclose,
 	.d_strategy = xbdstrategy,
 	.d_ioctl = xbdioctl,
 	.d_dump = xbddump,
 	.d_psize = xbdsize,
 	.d_discard = nodiscard,
 	.d_flag = D_DISK | D_MPSAFE
 };
 const struct cdevsw xbd_cdevsw = {
 	.d_open = xbdopen,
 	.d_close = xbdclose,
 	.d_read = xbdread,
 	.d_write = xbdwrite,
 	.d_ioctl = xbdioctl,
 	.d_stop = nostop,
 	.d_tty = notty,
 	.d_poll = nopoll,
 	.d_mmap = nommap,
 	.d_kqfilter = nokqfilter,
 	.d_discard = nodiscard,
 	.d_flag = D_DISK | D_MPSAFE
 };
 extern struct cfdriver xbd_cd;
 static const struct dkdriver xbddkdriver = {
         .d_strategy = xbdstrategy,
 	.d_minphys = xbdminphys,
 	.d_open = xbdopen,
 	.d_close = xbdclose,
 	.d_diskstart = xbd_diskstart,
 	.d_iosize = xbd_iosize,
 };
 static int
 xbd_xenbus_match(device_t parent, cfdata_t match, void *aux)
+{
 	struct xenbusdev_attach_args *xa = aux;
 	if (strcmp(xa->xa_type, "vbd") != 0)
 		return 0;
 	if (match->cf_loc[XENBUSCF_ID] != XENBUSCF_ID_DEFAULT &&
 	    match->cf_loc[XENBUSCF_ID] != xa->xa_id)
 		return 0;
 	return 1;
+}
 static void
 xbd_xenbus_attach(device_t parent, device_t self, void *aux)
+{
 	struct xbd_xenbus_softc *sc = device_private(self);
 	struct xenbusdev_attach_args *xa = aux;
 	blkif_sring_t *ring;
 	RING_IDX i;
 #ifdef XBD_DEBUG
 	char **dir, *val;
 	int dir_n = 0;
 	char id_str[20];
 	int err;
 #endif
 	config_pending_incr(self);
 	aprint_normal(": Xen Virtual Block Device Interface\n");
 	dk_init(&sc->sc_dksc, self, DKTYPE_ESDI);
 	disk_init(&sc->sc_dksc.sc_dkdev, device_xname(self), &xbddkdriver);
 	sc->sc_xbusd = xa->xa_xbusd;
 	sc->sc_xbusd->xbusd_otherend_changed = xbd_backend_changed;
 	mutex_init(&sc->sc_lock, MUTEX_DEFAULT, IPL_BIO);
 	cv_init(&sc->sc_cache_flush_cv, "xbdsync");
 	cv_init(&sc->sc_req_cv, "xbdreq");
 	cv_init(&sc->sc_detach_cv, "xbddetach");
 	cv_init(&sc->sc_suspend_cv, "xbdsuspend");
 	xbd_features(sc);
 	/* initialize free requests list */
 	SLIST_INIT(&sc->sc_xbdreq_head);
 	for (i = 0; i < XBD_RING_SIZE; i++) {
 		sc->sc_reqs[i].req_id = i;
 		SLIST_INSERT_HEAD(&sc->sc_xbdreq_head, &sc->sc_reqs[i],
 		    req_next);
+	}
 	if (sc->sc_features & BLKIF_FEATURE_INDIRECT) {
 		/* initialize indirect page list */
 		for (i = 0; i < XBD_RING_SIZE; i++) {
 			vmem_addr_t va;
 			if (uvm_km_kmem_alloc(kmem_va_arena,
 			    PAGE_SIZE, VM_SLEEP | VM_INSTANTFIT, &va) != 0) {
 				aprint_error_dev(self,
 				    "can't alloc indirect pages\n");
 				return;
+			}
 			sc->sc_indirect[i].in_addr = (void *)va;
 			SLIST_INSERT_HEAD(&sc->sc_indirect_head,
 			    &sc->sc_indirect[i], in_next);
+		}
+	}
 	sc->sc_backend_status = BLKIF_STATE_DISCONNECTED;
 	sc->sc_shutdown = BLKIF_SHUTDOWN_REMOTE;
 	ring = (void *)uvm_km_alloc(kernel_map, PAGE_SIZE, 0, UVM_KMF_WIRED);
 	if (ring == NULL)
 		panic("%s: can't alloc ring", device_xname(self));
 	sc->sc_ring.sring = ring;
 	evcnt_attach_dynamic(&sc->sc_cnt_map_unalign, EVCNT_TYPE_MISC,
 	    NULL, device_xname(self), "map unaligned");
 	evcnt_attach_dynamic(&sc->sc_cnt_unalign_busy, EVCNT_TYPE_MISC,
 	    NULL, device_xname(self), "map unaligned");
 	evcnt_attach_dynamic(&sc->sc_cnt_queue_full, EVCNT_TYPE_MISC,
 	    NULL, device_xname(self), "queue full");
 	evcnt_attach_dynamic(&sc->sc_cnt_indirect, EVCNT_TYPE_MISC,
 	    NULL, device_xname(self), "indirect segment");
 	for (i = 0; i < XBD_RING_SIZE; i++) {
 		if (bus_dmamap_create(sc->sc_xbusd->xbusd_dmat,
 		    MAXPHYS, XBD_XFER_LIMIT >> PAGE_SHIFT,
 		    PAGE_SIZE, PAGE_SIZE, BUS_DMA_WAITOK | BUS_DMA_ALLOCNOW,
 		    &sc->sc_reqs[i].req_dmamap) != 0) {
 			aprint_error_dev(self, "can't alloc dma maps\n");
 			return;
+		}
+	}
 	if (uvm_km_kmem_alloc(kmem_va_arena,
 	    MAXPHYS, VM_SLEEP | VM_INSTANTFIT, &sc->sc_unalign_buffer) != 0) {
 		aprint_error_dev(self, "can't alloc align buffer\n");
 		return;
+	}
 	/* resume shared structures and tell backend that we are ready */
 	if (xbd_xenbus_resume(self, PMF_Q_NONE) == false) {
 		uvm_km_free(kernel_map, (vaddr_t)ring, PAGE_SIZE,
 		    UVM_KMF_WIRED);
 		return;
+	}
 	if (!pmf_device_register(self, xbd_xenbus_suspend, xbd_xenbus_resume))
 		aprint_error_dev(self, "couldn't establish power handler\n");
+}
 static int
 xbd_xenbus_detach(device_t dev, int flags)
+{
 	struct xbd_xenbus_softc *sc = device_private(dev);
 	int bmaj, cmaj, i, mn, rc;
 	DPRINTF(("%s: xbd_detach\n", device_xname(dev)));
 	rc = disk_begindetach(&sc->sc_dksc.sc_dkdev, NULL, dev, flags);
 	if (rc != 0)
 		return rc;
 	mutex_enter(&sc->sc_lock);
 	if (sc->sc_shutdown == BLKIF_SHUTDOWN_RUN) {
 		sc->sc_shutdown = BLKIF_SHUTDOWN_LOCAL;
 		/* wait for requests to complete */
 		while (sc->sc_backend_status == BLKIF_STATE_CONNECTED &&
 		    disk_isbusy(&sc->sc_dksc.sc_dkdev)) {
 			cv_timedwait(&sc->sc_detach_cv, &sc->sc_lock, hz/2);
+		}
 		mutex_exit(&sc->sc_lock);
 		/* Trigger state transition with backend */
 		xenbus_switch_state(sc->sc_xbusd, NULL, XenbusStateClosing);
 		mutex_enter(&sc->sc_lock);
+	}
 	if ((flags & DETACH_FORCE) == 0) {
 		/* xbd_xenbus_detach already in progress */
 		cv_broadcast(&sc->sc_detach_cv);
 		mutex_exit(&sc->sc_lock);
 		return EALREADY;
+	}
 	mutex_exit(&sc->sc_lock);
 	while (xenbus_read_driver_state(sc->sc_xbusd->xbusd_otherend)
 	    != XenbusStateClosed) {
 		mutex_enter(&sc->sc_lock);
 		cv_timedwait(&sc->sc_detach_cv, &sc->sc_lock, hz/2);
 		mutex_exit(&sc->sc_lock);
+	}
 	/* locate the major number */
 	bmaj = bdevsw_lookup_major(&xbd_bdevsw);
 	cmaj = cdevsw_lookup_major(&xbd_cdevsw);
 	/* Nuke the vnodes for any open instances. */
 	for (i = 0; i < MAXPARTITIONS; i++) {
 		mn = DISKMINOR(device_unit(dev), i);
 		vdevgone(bmaj, mn, mn, VBLK);
 		vdevgone(cmaj, mn, mn, VCHR);
+	}
 	if (sc->sc_backend_status == BLKIF_STATE_CONNECTED) {
 		/* Delete all of our wedges. */
 		dkwedge_delall(&sc->sc_dksc.sc_dkdev);
 		/* Kill off any queued buffers. */
 		dk_drain(&sc->sc_dksc);
 		bufq_free(sc->sc_dksc.sc_bufq);
 		/* detach disk */
 		disk_detach(&sc->sc_dksc.sc_dkdev);
 		disk_destroy(&sc->sc_dksc.sc_dkdev);
 		dk_detach(&sc->sc_dksc);
+	}
 	hypervisor_mask_event(sc->sc_evtchn);
 	xen_intr_disestablish(sc->sc_ih);
 	mutex_enter(&sc->sc_lock);
 	while (xengnt_status(sc->sc_ring_gntref))
 		cv_timedwait(&sc->sc_detach_cv, &sc->sc_lock, hz/2);
 	mutex_exit(&sc->sc_lock);
 	xengnt_revoke_access(sc->sc_ring_gntref);
 	uvm_km_free(kernel_map, (vaddr_t)sc->sc_ring.sring,
 	    PAGE_SIZE, UVM_KMF_WIRED);
 	for (i = 0; i < XBD_RING_SIZE; i++) {
 		if (sc->sc_reqs[i].req_dmamap != NULL) {
 			bus_dmamap_destroy(sc->sc_xbusd->xbusd_dmat,
 			    sc->sc_reqs[i].req_dmamap);
 			sc->sc_reqs[i].req_dmamap = NULL;
+		}
+	}
 	if (sc->sc_unalign_buffer != 0) {
 		uvm_km_kmem_free(kmem_va_arena, sc->sc_unalign_buffer, MAXPHYS);
 		sc->sc_unalign_buffer = 0;
+	}
 	mutex_destroy(&sc->sc_lock);
 	evcnt_detach(&sc->sc_cnt_map_unalign);
 	evcnt_detach(&sc->sc_cnt_unalign_busy);
 	evcnt_detach(&sc->sc_cnt_queue_full);
 	evcnt_detach(&sc->sc_cnt_indirect);
 	pmf_device_deregister(dev);
 	return 0;
+}
 static bool
 xbd_xenbus_suspend(device_t dev, const pmf_qual_t *qual) {
 	struct xbd_xenbus_softc *sc;
 	sc = device_private(dev);
 	mutex_enter(&sc->sc_lock);
 	/* wait for requests to complete, then suspend device */
 	while (sc->sc_backend_status == BLKIF_STATE_CONNECTED &&
 	    disk_isbusy(&sc->sc_dksc.sc_dkdev)) {
 		cv_timedwait(&sc->sc_suspend_cv, &sc->sc_lock, hz/2);
+	}
 	hypervisor_mask_event(sc->sc_evtchn);
 	sc->sc_backend_status = BLKIF_STATE_SUSPENDED;
 	xen_intr_disestablish(sc->sc_ih);
 	mutex_exit(&sc->sc_lock);
 	xenbus_device_suspend(sc->sc_xbusd);
 	aprint_verbose_dev(dev, "removed event channel %d\n", sc->sc_evtchn);
 	return true;
+}
 static bool
 xbd_xenbus_resume(device_t dev, const pmf_qual_t *qual)
+{
 	struct xbd_xenbus_softc *sc;
 	struct xenbus_transaction *xbt;
 	int error;
 	blkif_sring_t *ring;
 	paddr_t ma;
 	const char *errmsg;
 	sc = device_private(dev);
 	if (sc->sc_backend_status == BLKIF_STATE_SUSPENDED) {
 		/*
 		 * Device was suspended, so ensure that access associated to
 		 * the block I/O ring is revoked.
 		 */
 		xengnt_revoke_access(sc->sc_ring_gntref);
+	}
 	sc->sc_ring_gntref = GRANT_INVALID_REF;
 	/* Initialize ring */
 	ring = sc->sc_ring.sring;
 	memset(ring, 0, PAGE_SIZE);
 	SHARED_RING_INIT(ring);
 	FRONT_RING_INIT(&sc->sc_ring, ring, PAGE_SIZE);
 	/*
 	 * get MA address of the ring, and use it to set up the grant entry
 	 * for the block device
 	 */
 	(void)pmap_extract_ma(pmap_kernel(), (vaddr_t)ring, &ma);
 	error = xenbus_grant_ring(sc->sc_xbusd, ma, &sc->sc_ring_gntref);
 	if (error)
 		goto abort_resume;
 	if (sc->sc_features & BLKIF_FEATURE_INDIRECT) {
 		for (int i = 0; i < XBD_RING_SIZE; i++) {
 			vaddr_t va = (vaddr_t)sc->sc_indirect[i].in_addr;
 			KASSERT(va != 0);
 			KASSERT((va & PAGE_MASK) == 0);
 			(void)pmap_extract_ma(pmap_kernel(), va, &ma);
 			if (xengnt_grant_access(
 			    sc->sc_xbusd->xbusd_otherend_id,
 			    ma, true, &sc->sc_indirect[i].in_gntref)) {
 				aprint_error_dev(dev,
 				    "indirect page grant failed\n");
 				goto abort_resume;
+			}
+		}
+	}
 	error = xenbus_alloc_evtchn(sc->sc_xbusd, &sc->sc_evtchn);
 	if (error)
 		goto abort_resume;
 	aprint_verbose_dev(dev, "using event channel %d\n",
 	    sc->sc_evtchn);
 	sc->sc_ih = xen_intr_establish_xname(-1, &xen_pic, sc->sc_evtchn,
 	    IST_LEVEL, IPL_BIO, &xbd_handler, sc, true, device_xname(dev));
 	KASSERT(sc->sc_ih != NULL);
 again:
 	xbt = xenbus_transaction_start();
 	if (xbt == NULL)
 		return false;
 	error = xenbus_printf(xbt, sc->sc_xbusd->xbusd_path,
 	    "ring-ref","%u", sc->sc_ring_gntref);
 	if (error) {
 		errmsg = "writing ring-ref";
 		goto abort_transaction;
+	}
 	error = xenbus_printf(xbt, sc->sc_xbusd->xbusd_path,
 	    "event-channel", "%u", sc->sc_evtchn);
 	if (error) {
 		errmsg = "writing event channel";
 		goto abort_transaction;
+	}
 	error = xenbus_printf(xbt, sc->sc_xbusd->xbusd_path,
 	    "protocol", "%s", XEN_IO_PROTO_ABI_NATIVE);
 	if (error) {
 		errmsg = "writing protocol";
 		goto abort_transaction;
+	}
 	error = xenbus_transaction_end(xbt, 0);
 	if (error == EAGAIN)
 		goto again;
 	if (error != 0) {
 		xenbus_dev_fatal(sc->sc_xbusd, error,
 		    "completing transaction");
 		return false;
+	}
 	xenbus_switch_state(sc->sc_xbusd, NULL, XenbusStateInitialised);
 	if (sc->sc_backend_status == BLKIF_STATE_SUSPENDED) {
 		/*
 		 * device was suspended, softc structures are
 		 * already initialized - we use a shortcut
 		 */
 		sc->sc_backend_status = BLKIF_STATE_CONNECTED;
 		xenbus_device_resume(sc->sc_xbusd);
 		hypervisor_unmask_event(sc->sc_evtchn);
 		xenbus_switch_state(sc->sc_xbusd, NULL, XenbusStateConnected);
+	}
 	return true;
 abort_resume:
 	xenbus_dev_fatal(sc->sc_xbusd, error, "resuming device");
 	return false;
 abort_transaction:
 	xenbus_transaction_end(xbt, 1);
 	xenbus_dev_fatal(sc->sc_xbusd, error, "%s", errmsg);
 	return false;
+}
 static void
 xbd_backend_changed(void *arg, XenbusState new_state)
+{
 	struct xbd_xenbus_softc *sc = device_private((device_t)arg);
 	struct disk_geom *dg;
 	char buf[64];
 	DPRINTF(("%s: new backend state %d\n",
 	    device_xname(sc->sc_dksc.sc_dev), new_state));
 	switch (new_state) {
 	case XenbusStateUnknown:
 	case XenbusStateInitialising:
 	case XenbusStateInitWait:
 	case XenbusStateInitialised:
 		break;
 	case XenbusStateClosing:
 		mutex_enter(&sc->sc_lock);
 		if (sc->sc_shutdown == BLKIF_SHUTDOWN_RUN)
 			sc->sc_shutdown = BLKIF_SHUTDOWN_REMOTE;
 		/* wait for requests to complete */
 		while (sc->sc_backend_status == BLKIF_STATE_CONNECTED &&
 		    disk_isbusy(&sc->sc_dksc.sc_dkdev)) {
 			cv_timedwait(&sc->sc_detach_cv, &sc->sc_lock, hz/2);
+		}
 		mutex_exit(&sc->sc_lock);
 		xenbus_switch_state(sc->sc_xbusd, NULL, XenbusStateClosed);
 		break;
 	case XenbusStateConnected:
 		/*
 		 * note that xbd_backend_changed() can only be called by
 		 * the xenbus thread.
 		 */
 		if (sc->sc_backend_status == BLKIF_STATE_CONNECTED ||
 		    sc->sc_backend_status == BLKIF_STATE_SUSPENDED)
 			/* already connected */
 			return;
 		xbd_connect(sc);
 		sc->sc_shutdown = BLKIF_SHUTDOWN_RUN;
 		sc->sc_xbdsize =
 		    sc->sc_sectors * (uint64_t)sc->sc_secsize / DEV_BSIZE;
 		dg = &sc->sc_dksc.sc_dkdev.dk_geom;
 		memset(dg, 0, sizeof(*dg));
 		dg->dg_secperunit = sc->sc_xbdsize;
 		dg->dg_secsize = DEV_BSIZE;
 		dg->dg_ntracks = 1;
 		// XXX: Ok to hard-code DEV_BSIZE?
 		dg->dg_nsectors = 1024 * (1024 / dg->dg_secsize);
 		dg->dg_ncylinders = dg->dg_secperunit / dg->dg_nsectors;
 		bufq_alloc(&sc->sc_dksc.sc_bufq, "fcfs", 0);
 		dk_attach(&sc->sc_dksc);
 		disk_attach(&sc->sc_dksc.sc_dkdev);
 		sc->sc_backend_status = BLKIF_STATE_CONNECTED;
 		hypervisor_unmask_event(sc->sc_evtchn);
 		format_bytes(buf, sizeof(buf), sc->sc_sectors * sc->sc_secsize);
 		aprint_normal_dev(sc->sc_dksc.sc_dev,
 				"%s, %d bytes/sect x %" PRIu64 " sectors\n",
 				buf, (int)dg->dg_secsize, sc->sc_xbdsize);
 		snprintb(buf, sizeof(buf), BLKIF_FEATURE_BITS,
 		    sc->sc_features);
 		aprint_normal_dev(sc->sc_dksc.sc_dev,
 		    "backend features %s\n", buf);
 		/* Discover wedges on this disk. */
 		dkwedge_discover(&sc->sc_dksc.sc_dkdev);
 		disk_set_info(sc->sc_dksc.sc_dev, &sc->sc_dksc.sc_dkdev, NULL);
 		/* the disk should be working now */
 		config_pending_decr(sc->sc_dksc.sc_dev);
 		break;
 	default:
 		panic("bad backend state %d", new_state);
+	}
+}
 static void
 xbd_connect(struct xbd_xenbus_softc *sc)
+{
 	int err;
 	unsigned long long sectors;
 	err = xenbus_read_ul(NULL,
 	    sc->sc_xbusd->xbusd_path, "virtual-device", &sc->sc_handle, 10);
 	if (err)
 		panic("%s: can't read number from %s/virtual-device\n",
 		    device_xname(sc->sc_dksc.sc_dev),
 		    sc->sc_xbusd->xbusd_otherend);
 	err = xenbus_read_ull(NULL,
 	    sc->sc_xbusd->xbusd_otherend, "sectors", &sectors, 10);
 	if (err)
 		panic("%s: can't read number from %s/sectors\n",
 		    device_xname(sc->sc_dksc.sc_dev),
 		    sc->sc_xbusd->xbusd_otherend);
 	sc->sc_sectors = sectors;
 	err = xenbus_read_ul(NULL,
 	    sc->sc_xbusd->xbusd_otherend, "info", &sc->sc_info, 10);
 	if (err)
 		panic("%s: can't read number from %s/info\n",
 		    device_xname(sc->sc_dksc.sc_dev),
 		    sc->sc_xbusd->xbusd_otherend);
 	err = xenbus_read_ul(NULL,
 	    sc->sc_xbusd->xbusd_otherend, "sector-size", &sc->sc_secsize, 10);
 	if (err)
 		panic("%s: can't read number from %s/sector-size\n",
 		    device_xname(sc->sc_dksc.sc_dev),
 		    sc->sc_xbusd->xbusd_otherend);
 	xenbus_switch_state(sc->sc_xbusd, NULL, XenbusStateConnected);
+}
 static void
 xbd_features(struct xbd_xenbus_softc *sc)
+{
 	int err;
 	u_long val;
 	err = xenbus_read_ul(NULL, sc->sc_xbusd->xbusd_otherend,
 	    "feature-flush-cache", &val, 10);
 	if (err)
 		val = 0;
 	if (val > 0)
 		sc->sc_features |= BLKIF_FEATURE_CACHE_FLUSH;
 	err = xenbus_read_ul(NULL, sc->sc_xbusd->xbusd_otherend,
 	    "feature-barrier", &val, 10);
 	if (err)
 		val = 0;
 	if (val > 0)
 		sc->sc_features |= BLKIF_FEATURE_BARRIER;
 	err = xenbus_read_ul(NULL, sc->sc_xbusd->xbusd_otherend,
 	    "feature-persistent", &val, 10);
 	if (err)
 		val = 0;
 	if (val > 0)
 		sc->sc_features |= BLKIF_FEATURE_PERSISTENT;
 	err = xenbus_read_ul(NULL, sc->sc_xbusd->xbusd_otherend,
 	    "feature-max-indirect-segments", &val, 10);
 	if (err)
 		val = 0;
 	if (val > (MAXPHYS >> PAGE_SHIFT)) {
 		/* We can use indirect segments, the limit is big enough */
 		sc->sc_features |= BLKIF_FEATURE_INDIRECT;
+	}
+}
 static int
 xbd_handler(void *arg)
+{
 	struct xbd_xenbus_softc *sc = arg;
 	struct buf *bp;
 	RING_IDX resp_prod, i;
 	int more_to_do;
 	int seg;
 	grant_ref_t gntref;
 	DPRINTF(("xbd_handler(%s)\n", device_xname(sc->sc_dksc.sc_dev)));
 	if (__predict_false(sc->sc_backend_status != BLKIF_STATE_CONNECTED))
 		return 0;
 	mutex_enter(&sc->sc_lock);
 again:
 	resp_prod = sc->sc_ring.sring->rsp_prod;
 	xen_rmb(); /* ensure we see replies up to resp_prod */
 	for (i = sc->sc_ring.rsp_cons; i != resp_prod; i++) {
 		blkif_response_t *rep = RING_GET_RESPONSE(&sc->sc_ring, i);
 		struct xbd_req *xbdreq = &sc->sc_reqs[rep->id];
 		if (rep->operation == BLKIF_OP_FLUSH_DISKCACHE) {
 			KASSERT(xbdreq->req_bp == NULL);
 			xbdreq->req_sync.s_error = rep->status;
 			xbdreq->req_sync.s_done = 1;
 			cv_broadcast(&sc->sc_cache_flush_cv);
 			/* caller will free the req */
 			continue;
+		}
 		if (rep->operation != BLKIF_OP_READ &&
 		    rep->operation != BLKIF_OP_WRITE) {
 			aprint_error_dev(sc->sc_dksc.sc_dev,
 			    "bad operation %d from backend\n", rep->operation);
 			continue;
+		}
 		bp = xbdreq->req_bp;
 		KASSERT(bp != NULL && bp->b_data != NULL);
 		DPRINTF(("%s(%p): b_bcount = %ld\n", __func__,
 		    bp, (long)bp->b_bcount));
 		if (bp->b_error != 0 || rep->status != BLKIF_RSP_OKAY) {
 			bp->b_error = EIO;
 			bp->b_resid = bp->b_bcount;
+		}
 		if (xbdreq->req_parent) {
 			struct xbd_req *req_parent = xbdreq->req_parent;
 			/* Unhook and recycle child */
 			xbdreq->req_parent = NULL;
 			req_parent->req_child = NULL;
 			SLIST_INSERT_HEAD(&sc->sc_xbdreq_head, xbdreq,
 				    req_next);
 			if (!req_parent->req_parent_done) {
 				/* Finished before parent, nothig else to do */
 				continue;
+			}
 			/* Must do the cleanup now */
 			xbdreq = req_parent;
+		}
 		if (xbdreq->req_child) {
 			/* Finished before child, child will cleanup */
 			xbdreq->req_parent_done = true;
 			continue;
+		}
 		if (bp->b_error == 0)
 			bp->b_resid = 0;
 		for (seg = 0; seg < xbdreq->req_dmamap->dm_nsegs; seg++) {
 			/*
 			 * We are not allowing persistent mappings, so
 			 * expect the backend to release the grant
 			 * immediately.
 			 */
 			if (xbdreq->req_indirect) {
 				gntref =
 				    xbdreq->req_indirect->in_addr[seg].gref;
 			} else
 				gntref = xbdreq->req_gntref[seg];
 			KASSERT(xengnt_status(gntref) == 0);
 			xengnt_revoke_access(gntref);
+		}
 		bus_dmamap_unload(sc->sc_xbusd->xbusd_dmat, xbdreq->req_dmamap);
 		if (__predict_false(bp->b_data != xbdreq->req_data))
 			xbd_unmap_align(sc, xbdreq, true);
 		xbdreq->req_bp = xbdreq->req_data = NULL;
 		dk_done(&sc->sc_dksc, bp);
 		if (xbdreq->req_indirect) {
 			/* No persistent mappings, so check that
 			 * backend unmapped the indirect segment grant too.
 			 */
 			KASSERT(xengnt_status(xbdreq->req_indirect->in_gntref)
 			    == 0);
 			SLIST_INSERT_HEAD(&sc->sc_indirect_head,
 			    xbdreq->req_indirect, in_next);
 			xbdreq->req_indirect = NULL;
+		}
 		SLIST_INSERT_HEAD(&sc->sc_xbdreq_head, xbdreq, req_next);
+	}
 	xen_rmb();
 	sc->sc_ring.rsp_cons = i;
 	RING_FINAL_CHECK_FOR_RESPONSES(&sc->sc_ring, more_to_do);
 	if (more_to_do)
 		goto again;
 	cv_signal(&sc->sc_req_cv);
 	mutex_exit(&sc->sc_lock);
 	dk_start(&sc->sc_dksc, NULL);
 	return 1;
+}
 static void
 xbdminphys(struct buf *bp)
+{
 	if (bp->b_bcount > XBD_XFER_LIMIT) {
 		bp->b_bcount = XBD_XFER_LIMIT;
+	}
 	minphys(bp);
+}
 static void
 xbd_iosize(device_t dev, int *maxxfer)
+{
 	/*
 	 * Always restrict dumps to XBD_MAX_XFER to avoid indirect segments,
 	 * so that it uses as little memory as possible.
 	 */
 	if (*maxxfer > XBD_MAX_XFER)
 		*maxxfer = XBD_MAX_XFER;
+}
 int
 xbdopen(dev_t dev, int flags, int fmt, struct lwp *l)
+{
 	struct	xbd_xenbus_softc *sc;
 	sc = device_lookup_private(&xbd_cd, DISKUNIT(dev));
 	if (sc == NULL)
 		return (ENXIO);
 	if ((flags & FWRITE) && (sc->sc_info & VDISK_READONLY))
 		return EROFS;
-	DPRINTF(("xbdopen(0x%04x, %d)\n", dev, flags));
+	DPRINTF(("xbdopen(%" PRIx64 ", %d)\n", dev, flags));
 	return dk_open(&sc->sc_dksc, dev, flags, fmt, l);
+}
 int
 xbdclose(dev_t dev, int flags, int fmt, struct lwp *l)
+{
 	struct xbd_xenbus_softc *sc;
 	sc = device_lookup_private(&xbd_cd, DISKUNIT(dev));
-	DPRINTF(("xbdclose(%d, %d)\n", dev, flags));
+	DPRINTF(("xbdclose(%" PRIx64 ", %d)\n", dev, flags));
 	return dk_close(&sc->sc_dksc, dev, flags, fmt, l);
+}
 void
 xbdstrategy(struct buf *bp)
+{
 	struct xbd_xenbus_softc *sc;
 	sc = device_lookup_private(&xbd_cd, DISKUNIT(bp->b_dev));
 	DPRINTF(("xbdstrategy(%p): b_bcount = %ld\n", bp,
 	    (long)bp->b_bcount));
 	if (sc == NULL || sc->sc_shutdown != BLKIF_SHUTDOWN_RUN) {
 		bp->b_error = EIO;
 		biodone(bp);
 		return;
+	}
 	if (__predict_false((sc->sc_info & VDISK_READONLY) &&
 	    (bp->b_flags & B_READ) == 0)) {
 		bp->b_error = EROFS;
 		biodone(bp);
 		return;
+	}
 	dk_strategy(&sc->sc_dksc, bp);
 	return;
+}
 int
 xbdsize(dev_t dev)
+{
 	struct	xbd_xenbus_softc *sc;
-	DPRINTF(("xbdsize(%d)\n", dev));
+	DPRINTF(("xbdsize(%" PRIx64 ")\n", dev));
 	sc = device_lookup_private(&xbd_cd, DISKUNIT(dev));
 	if (sc == NULL || sc->sc_shutdown != BLKIF_SHUTDOWN_RUN)
 		return -1;
 	return dk_size(&sc->sc_dksc, dev);
+}
 int
 xbdread(dev_t dev, struct uio *uio, int flags)
+{
 	struct xbd_xenbus_softc *sc =
 	    device_lookup_private(&xbd_cd, DISKUNIT(dev));
 	struct  dk_softc *dksc = &sc->sc_dksc;
 	if (!DK_ATTACHED(dksc))
 		return ENXIO;
 	return physio(xbdstrategy, NULL, dev, B_READ, xbdminphys, uio);
+}
 int
 xbdwrite(dev_t dev, struct uio *uio, int flags)
+{
 	struct xbd_xenbus_softc *sc =
 	    device_lookup_private(&xbd_cd, DISKUNIT(dev));
 	struct  dk_softc *dksc = &sc->sc_dksc;
 	if (!DK_ATTACHED(dksc))
 		return ENXIO;
 	if (__predict_false(sc->sc_info & VDISK_READONLY))
 		return EROFS;
 	return physio(xbdstrategy, NULL, dev, B_WRITE, xbdminphys, uio);
+}
 int
 xbdioctl(dev_t dev, u_long cmd, void *data, int flag, struct lwp *l)
+{
 	struct xbd_xenbus_softc *sc =
 	    device_lookup_private(&xbd_cd, DISKUNIT(dev));
 	struct	dk_softc *dksc;
 	int	error;
 	struct xbd_req *xbdreq;
 	blkif_request_t *req;
 	int notify;
-	DPRINTF(("xbdioctl(%d, %08lx, %p, %d, %p)\n",
+	DPRINTF(("xbdioctl(%" PRIx64 ", %08lx, %p, %d, %p)\n",
 	    dev, cmd, data, flag, l));
 	dksc = &sc->sc_dksc;
 	switch (cmd) {
 	case DIOCGCACHE:
+	    {
 		/* Assume there is write cache if cache-flush is supported */
 		int *bitsp = (int *)data;
 		*bitsp = 0;
 		if (sc->sc_features & BLKIF_FEATURE_CACHE_FLUSH)
 			*bitsp |= DKCACHE_WRITE;
 		error = 0;
 		break;
+	    }
 	case DIOCCACHESYNC:
 		if ((sc->sc_features & BLKIF_FEATURE_CACHE_FLUSH) == 0)
 			return EOPNOTSUPP;
 		mutex_enter(&sc->sc_lock);
 		while ((xbdreq = SLIST_FIRST(&sc->sc_xbdreq_head)) == NULL)
 			cv_wait(&sc->sc_req_cv, &sc->sc_lock);
 		SLIST_REMOVE_HEAD(&sc->sc_xbdreq_head, req_next);
 		req = RING_GET_REQUEST(&sc->sc_ring,
 		    sc->sc_ring.req_prod_pvt);
 		req->id = xbdreq->req_id;
 		req->operation = BLKIF_OP_FLUSH_DISKCACHE;
 		req->handle = sc->sc_handle;
 		xbdreq->req_sync.s_done = 0;
 		sc->sc_ring.req_prod_pvt++;
 		RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&sc->sc_ring, notify);
 		if (notify)
 			hypervisor_notify_via_evtchn(sc->sc_evtchn);
 		/* request sent, now wait for completion */
 		while (xbdreq->req_sync.s_done == 0)
 			cv_wait(&sc->sc_cache_flush_cv, &sc->sc_lock);
 		if (xbdreq->req_sync.s_error == BLKIF_RSP_EOPNOTSUPP)
 			error = EOPNOTSUPP;
 		else if (xbdreq->req_sync.s_error == BLKIF_RSP_OKAY)
 			error = 0;
 		else
 			error = EIO;
 		SLIST_INSERT_HEAD(&sc->sc_xbdreq_head, xbdreq, req_next);
 		cv_signal(&sc->sc_req_cv);
 		mutex_exit(&sc->sc_lock);
 		/* Restart I/O if it was waiting for req */
 		dk_start(&sc->sc_dksc, NULL);
 		break;
 	default:
 		error = dk_ioctl(dksc, dev, cmd, data, flag, l);
 		break;
+	}
 	return error;
+}
 int
 xbddump(dev_t dev, daddr_t blkno, void *va, size_t size)
+{
 	struct xbd_xenbus_softc *sc;
 	sc  = device_lookup_private(&xbd_cd, DISKUNIT(dev));
 	if (sc == NULL)
 		return (ENXIO);
-	DPRINTF(("xbddump(%d, %" PRId64 ", %p, %lu)\n", dev, blkno, va,
+	DPRINTF(("xbddump(%" PRIx64 ", %" PRId64 ", %p, %lu)\n", dev, blkno, va,
 	    (unsigned long)size));
 	return dk_dump(&sc->sc_dksc, dev, blkno, va, size, 0);
+}
 static int
 xbd_diskstart(device_t self, struct buf *bp)
+{
 	struct xbd_xenbus_softc *sc = device_private(self);
 	struct xbd_req *xbdreq;
 	int error = 0;
 	int notify;
 	KASSERT(bp->b_bcount <= MAXPHYS);
 	DPRINTF(("xbd_diskstart(%p): b_bcount = %ld\n",
 	    bp, (long)bp->b_bcount));
 	mutex_enter(&sc->sc_lock);
 	if (sc->sc_shutdown != BLKIF_SHUTDOWN_RUN) {
 		error = EIO;
 		goto out;
+	}
 	if (bp->b_rawblkno < 0 || bp->b_rawblkno > sc->sc_xbdsize) {
 		/* invalid block number */
 		error = EINVAL;
 		goto out;
+	}
 	if (__predict_false(
 	    sc->sc_backend_status == BLKIF_STATE_SUSPENDED)) {
 		/* device is suspended, do not consume buffer */
 		DPRINTF(("%s: (xbd_diskstart) device suspended\n",
 		    sc->sc_dksc.sc_xname));
 		error = EAGAIN;
 		goto out;
+	}
 	xbdreq = SLIST_FIRST(&sc->sc_xbdreq_head);
 	if (__predict_false(xbdreq == NULL)) {
 		sc->sc_cnt_queue_full.ev_count++;
 		DPRINTF(("xbd_diskstart: no req\n"));
 		error = EAGAIN;
 		goto out;
+	}
 	if ((sc->sc_features & BLKIF_FEATURE_INDIRECT) == 0
 	    && bp->b_bcount > XBD_MAX_CHUNK) {
 		if (!SLIST_NEXT(xbdreq, req_next)) {
 			DPRINTF(("%s: need extra req\n", __func__));
 			error = EAGAIN;
 			goto out;
+		}
+	}
 	bp->b_resid = bp->b_bcount;
 	xbdreq->req_bp = bp;
 	xbdreq->req_data = bp->b_data;
 	if (__predict_false((vaddr_t)bp->b_data & (XEN_BSIZE - 1))) {
 		if (__predict_false(xbd_map_align(sc, xbdreq) != 0)) {
 			DPRINTF(("xbd_diskstart: no align\n"));
 			error = EAGAIN;
 			goto out;
+		}
+	}
 	if (__predict_false(bus_dmamap_load(sc->sc_xbusd->xbusd_dmat,
 	    xbdreq->req_dmamap, xbdreq->req_data, bp->b_bcount, NULL,
 	    BUS_DMA_NOWAIT) != 0)) {
 		printf("%s: %s: bus_dmamap_load failed\n",
 		    device_xname(sc->sc_dksc.sc_dev), __func__);
 		if (__predict_false(bp->b_data != xbdreq->req_data))
 			xbd_unmap_align(sc, xbdreq, false);
 		error = EINVAL;
 		goto out;
+	}
 	for (int seg = 0; seg < xbdreq->req_dmamap->dm_nsegs; seg++) {
 		KASSERT(seg < __arraycount(xbdreq->req_gntref));
 		paddr_t ma = xbdreq->req_dmamap->dm_segs[seg].ds_addr;
 		if (__predict_false(xengnt_grant_access(
 		    sc->sc_xbusd->xbusd_otherend_id,
 		    (ma & ~PAGE_MASK), (bp->b_flags & B_READ) == 0,
 		    &xbdreq->req_gntref[seg]))) {
 			printf("%s: %s: xengnt_grant_access failed\n",
 			    device_xname(sc->sc_dksc.sc_dev), __func__);
 			if (seg > 0) {
 				for (; --seg >= 0; ) {
 					xengnt_revoke_access(
 					    xbdreq->req_gntref[seg]);
+				}
+			}
 			bus_dmamap_unload(sc->sc_xbusd->xbusd_dmat,
 			    xbdreq->req_dmamap);
 			if (__predict_false(bp->b_data != xbdreq->req_data))
 				xbd_unmap_align(sc, xbdreq, false);
 			error = EAGAIN;
 			goto out;
+		}
+	}
 	KASSERT(xbdreq->req_parent == NULL);
 	KASSERT(xbdreq->req_child == NULL);
 	/* We are now committed to the transfer */
 	SLIST_REMOVE_HEAD(&sc->sc_xbdreq_head, req_next);
 	if ((sc->sc_features & BLKIF_FEATURE_INDIRECT) != 0 &&
 	    bp->b_bcount > XBD_MAX_CHUNK) {
 		xbd_diskstart_submit_indirect(sc, xbdreq, bp);
 		goto push;
+	}
 	xbd_diskstart_submit(sc, xbdreq->req_id,
 	    bp, 0, xbdreq->req_dmamap, xbdreq->req_gntref);
 	if (bp->b_bcount > XBD_MAX_CHUNK) {
 		struct xbd_req *xbdreq2 = SLIST_FIRST(&sc->sc_xbdreq_head);
 		KASSERT(xbdreq2 != NULL); /* Checked earlier */
 		SLIST_REMOVE_HEAD(&sc->sc_xbdreq_head, req_next);
 		xbdreq->req_child = xbdreq2;
 		xbdreq->req_parent_done = false;
 		xbdreq2->req_parent = xbdreq;
 		xbdreq2->req_bp = bp;
 		xbdreq2->req_data = NULL;
 		xbd_diskstart_submit(sc, xbdreq2->req_id,
 		    bp, XBD_MAX_CHUNK, xbdreq->req_dmamap,
 		    xbdreq->req_gntref);
+	}
 push:
 	RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&sc->sc_ring, notify);
 	if (notify)
 		hypervisor_notify_via_evtchn(sc->sc_evtchn);
 out:
 	mutex_exit(&sc->sc_lock);
 	return error;
+}
 static void
 xbd_diskstart_submit(struct xbd_xenbus_softc *sc,
     int req_id, struct buf *bp, int start, bus_dmamap_t dmamap,
     grant_ref_t *gntref)
+{
 	blkif_request_t *req;
 	paddr_t ma;
 	int nsects, nbytes, dmaseg, first_sect, size, segidx = 0;
 	struct blkif_request_segment *reqseg;
 	KASSERT(mutex_owned(&sc->sc_lock));
 	req = RING_GET_REQUEST(&sc->sc_ring, sc->sc_ring.req_prod_pvt);
 	req->id = req_id;
 	req->operation =
 	    bp->b_flags & B_READ ? BLKIF_OP_READ : BLKIF_OP_WRITE;
 	req->sector_number = bp->b_rawblkno + (start >> XEN_BSHIFT);
 	req->handle = sc->sc_handle;
 	size = uimin(bp->b_bcount - start, XBD_MAX_CHUNK);
 	for (dmaseg = 0; dmaseg < dmamap->dm_nsegs && size > 0; dmaseg++) {
 		bus_dma_segment_t *ds = &dmamap->dm_segs[dmaseg];
 		ma = ds->ds_addr;
 		nbytes = imin(ds->ds_len, size);
 		if (start > 0) {
 			if (start >= nbytes) {
 				start -= nbytes;
 				continue;
+			}
 			ma += start;
 			nbytes -= start;
 			start = 0;
+		}
 		size -= nbytes;
 		KASSERT(((ma & PAGE_MASK) & (XEN_BSIZE - 1)) == 0);
 		KASSERT((nbytes & (XEN_BSIZE - 1)) == 0);
 		KASSERT((size & (XEN_BSIZE - 1)) == 0);
 		first_sect = (ma & PAGE_MASK) >> XEN_BSHIFT;
 		nsects = nbytes >> XEN_BSHIFT;
 		reqseg = &req->seg[segidx++];
 		reqseg->first_sect = first_sect;
 		reqseg->last_sect = first_sect + nsects - 1;
 		KASSERT(reqseg->first_sect <= reqseg->last_sect);
 		KASSERT(reqseg->last_sect < (PAGE_SIZE / XEN_BSIZE));
 		reqseg->gref = gntref[dmaseg];
+	}
 	req->nr_segments = segidx;
 	sc->sc_ring.req_prod_pvt++;
+}
 static void
 xbd_diskstart_submit_indirect(struct xbd_xenbus_softc *sc,
     struct xbd_req *xbdreq, struct buf *bp)
+{
 	blkif_request_indirect_t *req;
 	paddr_t ma;
 	int nsects, nbytes, dmaseg, first_sect;
 	struct blkif_request_segment *reqseg;
 	KASSERT(mutex_owned(&sc->sc_lock));
 	req = (blkif_request_indirect_t *)RING_GET_REQUEST(&sc->sc_ring,
 	    sc->sc_ring.req_prod_pvt);
 	req->id = xbdreq->req_id;
 	req->operation = BLKIF_OP_INDIRECT;
 	req->indirect_op =
 	    bp->b_flags & B_READ ? BLKIF_OP_READ : BLKIF_OP_WRITE;
 	req->sector_number = bp->b_rawblkno;
 	req->handle = sc->sc_handle;
 	xbdreq->req_indirect = SLIST_FIRST(&sc->sc_indirect_head);
 	KASSERT(xbdreq->req_indirect != NULL);	/* always as many as reqs */
 	SLIST_REMOVE_HEAD(&sc->sc_indirect_head, in_next);
 	req->indirect_grefs[0] = xbdreq->req_indirect->in_gntref;
 	reqseg = xbdreq->req_indirect->in_addr;
 	for (dmaseg = 0; dmaseg < xbdreq->req_dmamap->dm_nsegs; dmaseg++) {
 		bus_dma_segment_t *ds = &xbdreq->req_dmamap->dm_segs[dmaseg];
 		ma = ds->ds_addr;
 		nbytes = ds->ds_len;
 		first_sect = (ma & PAGE_MASK) >> XEN_BSHIFT;
 		nsects = nbytes >> XEN_BSHIFT;
 		reqseg->first_sect = first_sect;
 		reqseg->last_sect = first_sect + nsects - 1;
 		reqseg->gref = xbdreq->req_gntref[dmaseg];
 		KASSERT(reqseg->first_sect <= reqseg->last_sect);
 		KASSERT(reqseg->last_sect < (PAGE_SIZE / XEN_BSIZE));
 		reqseg++;
+	}
 	req->nr_segments = dmaseg;
 	sc->sc_ring.req_prod_pvt++;
 	sc->sc_cnt_indirect.ev_count++;
+}
 static int
 xbd_map_align(struct xbd_xenbus_softc *sc, struct xbd_req *req)
+{
 	/*
 	 * Only can get here if this is physio() request, block I/O
 	 * uses DEV_BSIZE-aligned buffers.
 	 */
 	KASSERT((req->req_bp->b_flags & B_PHYS) != 0);
 	sc->sc_cnt_map_unalign.ev_count++;
 	if (sc->sc_unalign_used) {
 		sc->sc_cnt_unalign_busy.ev_count++;
 		return EAGAIN;
+	}
 	sc->sc_unalign_used = req;
 	KASSERT(req->req_bp->b_bcount <= MAXPHYS);
 	req->req_data = (void *)sc->sc_unalign_buffer;
 	if ((req->req_bp->b_flags & B_READ) == 0)
 		memcpy(req->req_data, req->req_bp->b_data,
 		    req->req_bp->b_bcount);
 	return 0;
+}
 static void
 xbd_unmap_align(struct xbd_xenbus_softc *sc, struct xbd_req *req, bool sync)
+{
 	KASSERT(sc->sc_unalign_used == req);
 	if (sync && req->req_bp->b_flags & B_READ)
 		memcpy(req->req_bp->b_data, req->req_data,
 		    req->req_bp->b_bcount);
 	sc->sc_unalign_used = NULL;
+}