 @@ -1,1632 +1,1624 @@
-/*      $NetBSD: xbdback_xenbus.c,v 1.86 2020/04/21 13:56:18 jdolecek Exp $      */
+/*      $NetBSD: xbdback_xenbus.c,v 1.87 2020/04/23 07:24:40 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.
+ *
  */
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: xbdback_xenbus.c,v 1.86 2020/04/21 13:56:18 jdolecek Exp $");
+__KERNEL_RCSID(0, "$NetBSD: xbdback_xenbus.c,v 1.87 2020/04/23 07:24:40 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>
 #include <sys/param.h>
 #include <sys/queue.h>
 #include <sys/systm.h>
 #include <sys/time.h>
 #include <sys/types.h>
 #include <sys/vnode.h>
 #include <xen/xen.h>
 #include <xen/xen_shm.h>
 #include <xen/evtchn.h>
 #include <xen/xenbus.h>
 #include <xen/xenring.h>
 #include <xen/include/public/io/protocols.h>
 /* #define XENDEBUG_VBD */
 #ifdef XENDEBUG_VBD
 #define XENPRINTF(x) printf x
 #else
 #define XENPRINTF(x)
 #endif
 #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)
 #define VBD_MAX_INDIRECT_SEGMENTS	VBD_VA_SIZE >> PAGE_SHIFT
 CTASSERT(XENSHM_MAX_PAGES_PER_REQUEST >= VBD_MAX_INDIRECT_SEGMENTS);
 struct xbdback_io;
 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 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_do_io()
  * xbdback_co_main_loop()-|
  *        |               |-> xbdback_co_main_done2() or NULL
  *        |               |
  *        |               --> xbdback_co_main_incr() -> xbdback_co_main_loop()
  *        |
  *     xbdback_co_io() -> xbdback_co_main_incr() -> xbdback_co_main_loop()
  *        |
  *     xbdback_co_io_gotio() -> xbdback_map_shm()
  *        |                     |
  *        |                     xbdback_co_main_incr() -> xbdback_co_main_loop()
  *        |
  *     xbdback_co_do_io()
  *        |
  *     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;
 	vaddr_t xv_vaddr;
 };
 /* we keep the xbdback instances in a linked list */
 struct xbdback_instance {
 	SLIST_ENTRY(xbdback_instance) next;
 	struct xenbus_device *xbdi_xbusd; /* our xenstore entry */
 	struct xenbus_watch xbdi_watch; /* to watch our store */
 	domid_t xbdi_domid;	/* attached to this domain */
 	uint32_t xbdi_handle;	/* domain-specific handle */
 	char xbdi_name[16];	/* name of this instance */
 	/* mutex that protects concurrent access to the xbdback instance */
 	kmutex_t xbdi_lock;
 	kcondvar_t xbdi_cv;	/* wait channel for thread work */
 	xbdback_state_t xbdi_status; /* thread's status */
 	/* KVA for mapping transfers */
 	struct xbdback_va xbdi_va[BLKIF_RING_SIZE];
 	SLIST_HEAD(, xbdback_va) xbdi_va_free;
 	/* backing device parameters */
 	dev_t xbdi_dev;
 	const struct bdevsw *xbdi_bdevsw; /* pointer to the device's bdevsw */
 	struct vnode *xbdi_vp;
 	uint64_t xbdi_size;
 	bool xbdi_ro; /* is device read-only ? */
 	/* parameters for the communication */
 	unsigned int xbdi_evtchn;
 	struct intrhand *xbdi_ih;
 	/* 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;
 	/* _request state: track requests fetched from ring */
 	blkif_request_t xbdi_xen_req;
 	struct blkif_request_segment xbdi_seg[VBD_MAX_INDIRECT_SEGMENTS];
 	bus_dmamap_t xbdi_seg_dmamap;
 	grant_ref_t xbdi_in_gntref;
 	/* _io state: I/O associated to this instance */
 	struct xbdback_io *xbdi_io;
 	/* 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 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 */
 			/* 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[VBD_MAX_INDIRECT_SEGMENTS];
 			/* grants release */
 			grant_handle_t xio_gh[VBD_MAX_INDIRECT_SEGMENTS];
 			uint16_t xio_nrma; /* number of guest pages */
 		} xio_rw;
 	} u;
 };
 #define xio_buf		u.xio_rw.xio_buf
 #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
 /*
  * Pools to manage the chain of block requests and I/Os fragments
  * submitted by frontend.
  */
 static struct pool_cache xbdback_io_pool;
 /* Interval between reports of I/O errors from frontend */
 static const struct timeval xbdback_err_intvl = { 1, 0 };
        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_done2(struct xbdback_instance *, void *);
 static void *xbdback_co_cache_flush(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_gotio(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 pool_cache *,
 			      struct xbdback_instance *);
 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_io_pool,
 	    sizeof(struct xbdback_io), 0, 0, 0, "xbbip", NULL,
 	    IPL_SOFTBIO, NULL, NULL, NULL);
 	/* we allocate enough to handle a whole ring at once */
 	pool_prime(&xbdback_io_pool.pc_pool, 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,
 	    "frontend-id", &domid, 10)) != 0) {
 		aprint_error("xbdback: can't read %s/frontend-id: %d\n",
 		    xbusd->xbusd_path, error);
 		return error;
+	}
 	/*
 	 * get handle: this is the last component of the path; which is
 	 * a decimal number. $path/dev contains the device name, which is not
 	 * appropriate.
 	 */
 	for (i = strlen(xbusd->xbusd_path); i > 0; i--) {
 		if (xbusd->xbusd_path[i] == '/')
 			break;
+	}
 	if (i == 0) {
 		aprint_error("xbdback: can't parse %s\n",
 		    xbusd->xbusd_path);
 		return EFTYPE;
+	}
 	handle = strtoul(&xbusd->xbusd_path[i+1], &ep, 10);
 	if (*ep != '\0') {
 		aprint_error("xbdback: can't parse %s\n",
 		    xbusd->xbusd_path);
 		return EFTYPE;
+	}
 	if (xbdif_lookup(domid, handle)) {
 		return EEXIST;
+	}
 	xbdi = kmem_zalloc(sizeof(*xbdi), KM_SLEEP);
 	xbdi->xbdi_domid = domid;
 	xbdi->xbdi_handle = handle;
 	snprintf(xbdi->xbdi_name, sizeof(xbdi->xbdi_name), "xbdb%di%d",
 	    xbdi->xbdi_domid, xbdi->xbdi_handle);
 	/* initialize status and reference counter */
 	xbdi->xbdi_status = DISCONNECTED;
 	xbdi_get(xbdi);
 	mutex_init(&xbdi->xbdi_lock, MUTEX_DEFAULT, IPL_BIO);
 	cv_init(&xbdi->xbdi_cv, xbdi->xbdi_name);
 	mutex_enter(&xbdback_lock);
 	SLIST_INSERT_HEAD(&xbdback_instances, xbdi, next);
 	mutex_exit(&xbdback_lock);
 	xbusd->xbusd_u.b.b_cookie = xbdi;
 	xbusd->xbusd_u.b.b_detach = xbdback_xenbus_destroy;
 	xbusd->xbusd_otherend_changed = xbdback_frontend_changed;
 	xbdi->xbdi_xbusd = xbusd;
 	if (bus_dmamap_create(xbdi->xbdi_xbusd->xbusd_dmat, PAGE_SIZE,
 , PAGE_SIZE, PAGE_SIZE, BUS_DMA_WAITOK | BUS_DMA_ALLOCNOW,
 	    &xbdi->xbdi_seg_dmamap) != 0) {
 		printf("%s: can't create dma map for indirect segments\n",
 		    xbdi->xbdi_name);
 		goto fail;
+	}
 	if (bus_dmamap_load(xbdi->xbdi_xbusd->xbusd_dmat,
 	    xbdi->xbdi_seg_dmamap, xbdi->xbdi_seg,
 	    sizeof(xbdi->xbdi_seg), NULL, BUS_DMA_WAITOK) != 0) {
 		printf("%s: can't load dma map for indirect segments\n",
 		    xbdi->xbdi_name);
 		goto fail;
+	}
 	KASSERT(xbdi->xbdi_seg_dmamap->dm_nsegs == 1);
 	SLIST_INIT(&xbdi->xbdi_va_free);
 	for (i = 0; i < BLKIF_RING_SIZE; i++) {
 		xbdi->xbdi_va[i].xv_vaddr = uvm_km_alloc(kernel_map,
 		    VBD_VA_SIZE, 0, UVM_KMF_VAONLY|UVM_KMF_WAITVA);
 		SLIST_INSERT_HEAD(&xbdi->xbdi_va_free, &xbdi->xbdi_va[i],
 		    xv_next);
+	}
 	error = xenbus_watch_path2(xbusd, xbusd->xbusd_path, "physical-device",
 	    &xbdi->xbdi_watch, xbdback_backend_changed);
 	if (error) {
 		printf("failed to watch on %s/physical-device: %d\n",
 		    xbusd->xbusd_path, error);
 		goto fail;
+	}
 	xbdi->xbdi_watch.xbw_dev = xbusd;
 	error = xenbus_switch_state(xbusd, NULL, XenbusStateInitWait);
 	if (error) {
 		printf("failed to switch state on %s: %d\n",
 		    xbusd->xbusd_path, error);
 		goto fail2;
+	}
 	return 0;
 fail2:
 	unregister_xenbus_watch(&xbdi->xbdi_watch);
 fail:
 	kmem_free(xbdi, sizeof(*xbdi));
 	return error;
+}
 static int
 xbdback_xenbus_destroy(void *arg)
+{
 	struct xbdback_instance *xbdi = arg;
 	struct xenbus_device *xbusd = xbdi->xbdi_xbusd;
 	struct gnttab_unmap_grant_ref ungrop;
 	int err;
 	XENPRINTF(("xbdback_xenbus_destroy state %d\n", xbdi->xbdi_status));
 	xbdback_disconnect(xbdi);
 	/* unregister watch */
 	if (xbdi->xbdi_watch.node)
 		xenbus_unwatch_path(&xbdi->xbdi_watch);
 	/* unmap ring */
 	if (xbdi->xbdi_ring_va != 0) {
 		ungrop.host_addr = xbdi->xbdi_ring_va;
 		ungrop.handle = xbdi->xbdi_ring_handle;
 		ungrop.dev_bus_addr = 0;
 		err = HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref,
 		    &ungrop, 1);
 		if (err)
 		    printf("xbdback %s: unmap_grant_ref failed: %d\n",
 			xbusd->xbusd_otherend, err);
 		uvm_km_free(kernel_map, xbdi->xbdi_ring_va,
 		    PAGE_SIZE, UVM_KMF_VAONLY);
+	}
 	/* close device */
 	if (xbdi->xbdi_size) {
 		const char *name;
 		struct dkwedge_info wi;
 		if (getdiskinfo(xbdi->xbdi_vp, &wi) == 0)
 			name = wi.dkw_devname;
 		else
 			name = "*unknown*";
 		printf("xbd backend: detach device %s for domain %d\n",
 		    name, xbdi->xbdi_domid);
 		vn_close(xbdi->xbdi_vp, FREAD, NOCRED);
+	}
 	mutex_enter(&xbdback_lock);
 	SLIST_REMOVE(&xbdback_instances, xbdi, xbdback_instance, next);
 	mutex_exit(&xbdback_lock);
 	for (int i = 0; i < BLKIF_RING_SIZE; i++) {
 		if (xbdi->xbdi_va[i].xv_vaddr != 0) {
 			uvm_km_free(kernel_map, xbdi->xbdi_va[i].xv_vaddr,
 			    VBD_VA_SIZE, UVM_KMF_VAONLY);
 			xbdi->xbdi_va[i].xv_vaddr = 0;
+		}
+	}
 	bus_dmamap_unload(xbdi->xbdi_xbusd->xbusd_dmat, xbdi->xbdi_seg_dmamap);
 	bus_dmamap_destroy(xbdi->xbdi_xbusd->xbusd_dmat, xbdi->xbdi_seg_dmamap);
 	mutex_destroy(&xbdi->xbdi_lock);
 	cv_destroy(&xbdi->xbdi_cv);
 	kmem_free(xbdi, sizeof(*xbdi));
 	return 0;
+}
 static int
 xbdback_connect(struct xbdback_instance *xbdi)
+{
 	int err;
 	struct gnttab_map_grant_ref grop;
 	struct gnttab_unmap_grant_ref ungrop;
 	evtchn_op_t evop;
 	u_long ring_ref, revtchn;
 	char xsproto[32];
 	const char *proto;
 	struct xenbus_device *xbusd = xbdi->xbdi_xbusd;
 	XENPRINTF(("xbdback %s: connect\n", xbusd->xbusd_path));
 	/* read comunication informations */
 	err = xenbus_read_ul(NULL, xbusd->xbusd_otherend,
 	    "ring-ref", &ring_ref, 10);
 	if (err) {
 		xenbus_dev_fatal(xbusd, err, "reading %s/ring-ref",
 		    xbusd->xbusd_otherend);
 		return -1;
+	}
 	XENPRINTF(("xbdback %s: connect ring-ref %lu\n", xbusd->xbusd_path, ring_ref));
 	err = xenbus_read_ul(NULL, xbusd->xbusd_otherend,
 	    "event-channel", &revtchn, 10);
 	if (err) {
 		xenbus_dev_fatal(xbusd, err, "reading %s/event-channel",
 		    xbusd->xbusd_otherend);
 		return -1;
+	}
 	XENPRINTF(("xbdback %s: connect revtchn %lu\n", xbusd->xbusd_path, revtchn));
 	err = xenbus_read(NULL, xbusd->xbusd_otherend, "protocol",
 	    xsproto, sizeof(xsproto));
 	if (err) {
 		xbdi->xbdi_proto = XBDIP_NATIVE;
 		proto = "unspecified";
 		XENPRINTF(("xbdback %s: connect no xsproto\n", xbusd->xbusd_path));
 	} else {
 		XENPRINTF(("xbdback %s: connect xsproto %s\n", xbusd->xbusd_path, xsproto));
 		if (strcmp(xsproto, XEN_IO_PROTO_ABI_NATIVE) == 0) {
 			xbdi->xbdi_proto = XBDIP_NATIVE;
 			proto = XEN_IO_PROTO_ABI_NATIVE;
 		} else if (strcmp(xsproto, XEN_IO_PROTO_ABI_X86_32) == 0) {
 			xbdi->xbdi_proto = XBDIP_32;
 			proto = XEN_IO_PROTO_ABI_X86_32;
 		} else if (strcmp(xsproto, XEN_IO_PROTO_ABI_X86_64) == 0) {
 			xbdi->xbdi_proto = XBDIP_64;
 			proto = XEN_IO_PROTO_ABI_X86_64;
 		} else {
 			aprint_error("xbd domain %d: unknown proto %s\n",
 			    xbdi->xbdi_domid, xsproto);
 			return -1;
+		}
+	}
 	/* allocate VA space and map rings */
 	xbdi->xbdi_ring_va = uvm_km_alloc(kernel_map, PAGE_SIZE, 0,
 	    UVM_KMF_VAONLY);
 	if (xbdi->xbdi_ring_va == 0) {
 		xenbus_dev_fatal(xbusd, ENOMEM,
 		    "can't get VA for ring", xbusd->xbusd_otherend);
 		return -1;
+	}
 	XENPRINTF(("xbdback %s: connect va 0x%" PRIxVADDR "\n", xbusd->xbusd_path, xbdi->xbdi_ring_va));
 	grop.host_addr = xbdi->xbdi_ring_va;
 	grop.flags = GNTMAP_host_map;
 	grop.ref = ring_ref;
 	grop.dom = xbdi->xbdi_domid;
 	err = HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref,
 	    &grop, 1);
 	if (err || grop.status) {
 		aprint_error("xbdback %s: can't map grant ref: %d/%d\n",
 		    xbusd->xbusd_path, err, grop.status);
 		xenbus_dev_fatal(xbusd, EINVAL,
 		    "can't map ring", xbusd->xbusd_otherend);
 		goto err;
+	}
 	xbdi->xbdi_ring_handle = grop.handle;
 	XENPRINTF(("xbdback %s: connect grhandle %d\n", xbusd->xbusd_path, grop.handle));
 	switch(xbdi->xbdi_proto) {
 	case XBDIP_NATIVE:
+	{
 		blkif_sring_t *sring = (void *)xbdi->xbdi_ring_va;
 		BACK_RING_INIT(&xbdi->xbdi_ring.ring_n, sring, PAGE_SIZE);
 		break;
+	}
 	case XBDIP_32:
+	{
 		blkif_x86_32_sring_t *sring = (void *)xbdi->xbdi_ring_va;
 		BACK_RING_INIT(&xbdi->xbdi_ring.ring_32, sring, PAGE_SIZE);
 		break;
+	}
 	case XBDIP_64:
+	{
 		blkif_x86_64_sring_t *sring = (void *)xbdi->xbdi_ring_va;
 		BACK_RING_INIT(&xbdi->xbdi_ring.ring_64, sring, PAGE_SIZE);
 		break;
+	}
+	}
 	evop.cmd = EVTCHNOP_bind_interdomain;
 	evop.u.bind_interdomain.remote_dom = xbdi->xbdi_domid;
 	evop.u.bind_interdomain.remote_port = revtchn;
 	err = HYPERVISOR_event_channel_op(&evop);
 	if (err) {
 		aprint_error("blkback %s: "
 		    "can't get event channel: %d\n",
 		    xbusd->xbusd_otherend, err);
 		xenbus_dev_fatal(xbusd, err,
 		    "can't bind event channel", xbusd->xbusd_otherend);
 		goto err2;
+	}
 	XENPRINTF(("xbdback %s: connect evchannel %d\n", xbusd->xbusd_path, xbdi->xbdi_evtchn));
 	xbdi->xbdi_evtchn = evop.u.bind_interdomain.local_port;
 	xbdi->xbdi_ih = xen_intr_establish_xname(-1, &xen_pic, xbdi->xbdi_evtchn,
 	    IST_LEVEL, IPL_BIO, xbdback_evthandler, xbdi, false,
 	    xbdi->xbdi_name);
 	KASSERT(xbdi->xbdi_ih != NULL);
 	aprint_verbose("xbd backend domain %d handle %#x (%d) "
 	    "using event channel %d, protocol %s\n", xbdi->xbdi_domid,
 	    xbdi->xbdi_handle, xbdi->xbdi_handle, xbdi->xbdi_evtchn, proto);
 	/* enable the xbdback event handler machinery */
 	xbdi->xbdi_status = WAITING;
 	hypervisor_unmask_event(xbdi->xbdi_evtchn);
 	hypervisor_notify_via_evtchn(xbdi->xbdi_evtchn);
 	if (kthread_create(PRI_NONE, KTHREAD_MPSAFE, NULL,
 	    xbdback_thread, xbdi, NULL, "%s", xbdi->xbdi_name) == 0)
 		return 0;
 err2:
 	/* unmap ring */
 	ungrop.host_addr = xbdi->xbdi_ring_va;
 	ungrop.handle = xbdi->xbdi_ring_handle;
 	ungrop.dev_bus_addr = 0;
 	err = HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref,
 	    &ungrop, 1);
 	if (err)
 	    aprint_error("xbdback %s: unmap_grant_ref failed: %d\n",
 		xbusd->xbusd_path, err);
 err:
 	/* free ring VA space */
 	uvm_km_free(kernel_map, xbdi->xbdi_ring_va, PAGE_SIZE, UVM_KMF_VAONLY);
 	return -1;
+}
 /*
  * Signal a xbdback thread to disconnect. Done in 'xenwatch' thread context.
  */
 static void
 xbdback_disconnect(struct xbdback_instance *xbdi)
+{
 	mutex_enter(&xbdi->xbdi_lock);
 	if (xbdi->xbdi_status == DISCONNECTED) {
 		mutex_exit(&xbdi->xbdi_lock);
 		return;
+	}
 	hypervisor_mask_event(xbdi->xbdi_evtchn);
 	xen_intr_disestablish(xbdi->xbdi_ih);
 	/* signal thread that we want to disconnect, then wait for it */
 	xbdi->xbdi_status = DISCONNECTING;
 	cv_signal(&xbdi->xbdi_cv);
 	while (xbdi->xbdi_status != DISCONNECTED)
 		cv_wait(&xbdi->xbdi_cv, &xbdi->xbdi_lock);
 	mutex_exit(&xbdi->xbdi_lock);
 	xenbus_switch_state(xbdi->xbdi_xbusd, NULL, XenbusStateClosing);
+}
 static void
 xbdback_frontend_changed(void *arg, XenbusState new_state)
+{
 	struct xbdback_instance *xbdi = arg;
 	struct xenbus_device *xbusd = xbdi->xbdi_xbusd;
 	XENPRINTF(("xbdback %s: new state %d\n", xbusd->xbusd_path, new_state));
 	switch(new_state) {
 	case XenbusStateInitialising:
 		break;
 	case XenbusStateInitialised:
 	case XenbusStateConnected:
 		if (xbdi->xbdi_status == WAITING || xbdi->xbdi_status == RUN)
 			break;
 		xbdback_connect(xbdi);
 		break;
 	case XenbusStateClosing:
 		xbdback_disconnect(xbdi);
 		break;
 	case XenbusStateClosed:
 		/* otherend_changed() should handle it for us */
 		panic("xbdback_frontend_changed: closed\n");
 	case XenbusStateUnknown:
 	case XenbusStateInitWait:
 	default:
 		aprint_error("xbdback %s: invalid frontend state %d\n",
 		    xbusd->xbusd_path, new_state);
+	}
 	return;
+}
 static void
 xbdback_backend_changed(struct xenbus_watch *watch,
     const char **vec, unsigned int len)
+{
 	struct xenbus_device *xbusd = watch->xbw_dev;
 	struct xbdback_instance *xbdi = xbusd->xbusd_u.b.b_cookie;
 	int err;
 	long dev;
 	char mode[32];
 	struct xenbus_transaction *xbt;
 	const char *devname;
 	int major;
 	err = xenbus_read_ul(NULL, xbusd->xbusd_path, "physical-device",
 	    &dev, 10);
 	/*
 	 * An error can occur as the watch can fire up just after being
 	 * registered. So we have to ignore error  :(
 	 */
 	if (err)
 		return;
 	/*
 	 * we can also fire up after having opened the device, don't try
 	 * to do it twice.
 	 */
 	if (xbdi->xbdi_vp != NULL) {
 		if (xbdi->xbdi_status == WAITING || xbdi->xbdi_status == RUN) {
 			if (xbdi->xbdi_dev != dev) {
 				printf("xbdback %s: changing physical device "
 				    "from %#"PRIx64" to %#lx not supported\n",
 				    xbusd->xbusd_path, xbdi->xbdi_dev, dev);
+			}
+		}
 		return;
+	}
 	xbdi->xbdi_dev = dev;
 	err = xenbus_read(NULL, xbusd->xbusd_path, "mode", mode, sizeof(mode));
 	if (err) {
 		printf("xbdback: failed to read %s/mode: %d\n",
 		    xbusd->xbusd_path, err);
 		return;
+	}
 	if (mode[0] == 'w')
 		xbdi->xbdi_ro = false;
 	else
 		xbdi->xbdi_ro = true;
 	major = major(xbdi->xbdi_dev);
 	devname = devsw_blk2name(major);
 	if (devname == NULL) {
 		printf("xbdback %s: unknown device 0x%"PRIx64"\n",
 		    xbusd->xbusd_path, xbdi->xbdi_dev);
 		return;
+	}
 	xbdi->xbdi_bdevsw = bdevsw_lookup(xbdi->xbdi_dev);
 	if (xbdi->xbdi_bdevsw == NULL) {
 		printf("xbdback %s: no bdevsw for device 0x%"PRIx64"\n",
 		    xbusd->xbusd_path, xbdi->xbdi_dev);
 		return;
+	}
 	err = bdevvp(xbdi->xbdi_dev, &xbdi->xbdi_vp);
 	if (err) {
 		printf("xbdback %s: can't open device 0x%"PRIx64": %d\n",
 		    xbusd->xbusd_path, xbdi->xbdi_dev, err);
 		return;
+	}
 	err = vn_lock(xbdi->xbdi_vp, LK_EXCLUSIVE | LK_RETRY);
 	if (err) {
 		printf("xbdback %s: can't vn_lock device 0x%"PRIx64": %d\n",
 		    xbusd->xbusd_path, xbdi->xbdi_dev, err);
 		vrele(xbdi->xbdi_vp);
 		return;
+	}
 	err  = VOP_OPEN(xbdi->xbdi_vp, FREAD, NOCRED);
 	if (err) {
 		printf("xbdback %s: can't VOP_OPEN device 0x%"PRIx64": %d\n",
 		    xbusd->xbusd_path, xbdi->xbdi_dev, err);
 		vput(xbdi->xbdi_vp);
 		return;
+	}
 	VOP_UNLOCK(xbdi->xbdi_vp);
 	/* dk device; get wedge data */
 	struct dkwedge_info wi;
 	if ((err = getdiskinfo(xbdi->xbdi_vp, &wi)) == 0) {
 		xbdi->xbdi_size = wi.dkw_size;
 		printf("xbd backend: attach device %s (size %" PRIu64 ") "
 		    "for domain %d\n", wi.dkw_devname, xbdi->xbdi_size,
 		    xbdi->xbdi_domid);
 	} else {
 		/* If both Ioctls failed set device size to 0 and return */
 		printf("xbdback %s: can't DIOCGWEDGEINFO device "
 		    "0x%"PRIx64": %d\n", xbusd->xbusd_path,
 		    xbdi->xbdi_dev, err);
 		xbdi->xbdi_size = xbdi->xbdi_dev = 0;
 		vn_close(xbdi->xbdi_vp, FREAD, NOCRED);
 		xbdi->xbdi_vp = NULL;
 		return;
+	}
 again:
 	xbt = xenbus_transaction_start();
 	if (xbt == NULL) {
 		printf("xbdback %s: can't start transaction\n",
 		    xbusd->xbusd_path);
 		    return;
+	}
 	err = xenbus_printf(xbt, xbusd->xbusd_path, "sectors", "%" PRIu64 ,
 	    xbdi->xbdi_size);
 	if (err) {
 		printf("xbdback: failed to write %s/sectors: %d\n",
 		    xbusd->xbusd_path, err);
 		goto abort;
+	}
 	err = xenbus_printf(xbt, xbusd->xbusd_path, "info", "%u",
 	    xbdi->xbdi_ro ? VDISK_READONLY : 0);
 	if (err) {
 		printf("xbdback: failed to write %s/info: %d\n",
 		    xbusd->xbusd_path, err);
 		goto abort;
+	}
 	err = xenbus_printf(xbt, xbusd->xbusd_path, "sector-size", "%lu",
 	    (u_long)DEV_BSIZE);
 	if (err) {
 		printf("xbdback: failed to write %s/sector-size: %d\n",
 		    xbusd->xbusd_path, err);
 		goto abort;
+	}
 	err = xenbus_printf(xbt, xbusd->xbusd_path, "feature-flush-cache",
 	    "%u", 1);
 	if (err) {
 		printf("xbdback: failed to write %s/feature-flush-cache: %d\n",
 		    xbusd->xbusd_path, err);
 		goto abort;
+	}
 	err = xenbus_printf(xbt, xbusd->xbusd_path,
 	    "feature-max-indirect-segments", "%u", VBD_MAX_INDIRECT_SEGMENTS);
 	if (err) {
 		printf("xbdback: failed to write %s/feature-indirect: %d\n",
 		    xbusd->xbusd_path, err);
 		goto abort;
+	}
 	err = xenbus_transaction_end(xbt, 0);
 	if (err == EAGAIN)
 		goto again;
 	if (err) {
 		printf("xbdback %s: can't end transaction: %d\n",
 		    xbusd->xbusd_path, err);
+	}
 	err = xenbus_switch_state(xbusd, NULL, XenbusStateConnected);
 	if (err) {
 		printf("xbdback %s: can't switch state: %d\n",
 		    xbusd->xbusd_path, err);
+	}
 	return;
 abort:
 	xenbus_transaction_end(xbt, 1);
+}
 /*
  * Used by a xbdi thread to signal that it is now disconnected.
  */
 static void
 xbdback_finish_disconnect(struct xbdback_instance *xbdi)
+{
 	KASSERT(mutex_owned(&xbdi->xbdi_lock));
 	KASSERT(xbdi->xbdi_status == DISCONNECTING);
 	xbdi->xbdi_status = DISCONNECTED;
 	cv_signal(&xbdi->xbdi_cv);
+}
 static bool
 xbdif_lookup(domid_t dom , uint32_t handle)
+{
 	struct xbdback_instance *xbdi;
 	bool found = false;
 	mutex_enter(&xbdback_lock);
 	SLIST_FOREACH(xbdi, &xbdback_instances, next) {
 		if (xbdi->xbdi_domid == dom && xbdi->xbdi_handle == handle) {
 			found = true;
 			break;
+		}
+	}
 	mutex_exit(&xbdback_lock);
 	return found;
+}
 static int
 xbdback_evthandler(void *arg)
+{
 	struct xbdback_instance *xbdi = arg;
 	XENPRINTF(("xbdback_evthandler domain %d: cont %p\n",
 	    xbdi->xbdi_domid, xbdi->xbdi_cont));
 	xbdback_wakeup_thread(xbdi);
 	return 1;
+}
 /*
  * Main thread routine for one xbdback instance. Woken up by
  * xbdback_evthandler when a domain has I/O work scheduled in a I/O ring.
  */
 static void
 xbdback_thread(void *arg)
+{
 	struct xbdback_instance *xbdi = arg;
 	for (;;) {
 		mutex_enter(&xbdi->xbdi_lock);
 		switch (xbdi->xbdi_status) {
 		case WAITING:
 			cv_wait(&xbdi->xbdi_cv, &xbdi->xbdi_lock);
 			mutex_exit(&xbdi->xbdi_lock);
 			break;
 		case RUN:
 			xbdi->xbdi_status = WAITING; /* reset state */
 			mutex_exit(&xbdi->xbdi_lock);
 			if (xbdi->xbdi_cont == NULL) {
 				xbdi->xbdi_cont = xbdback_co_main;
+			}
 			xbdback_trampoline(xbdi, xbdi);
 			break;
 		case DISCONNECTING:
 			if (xbdi->xbdi_pendingreqs > 0) {
 				/* there are pending I/Os. Wait for them. */
 				cv_wait(&xbdi->xbdi_cv, &xbdi->xbdi_lock);
 				mutex_exit(&xbdi->xbdi_lock);
 				break;
+			}
 			/* All I/Os should have been processed by now,
 			 * xbdi_refcnt should drop to 0 */
 			xbdi_put(xbdi);
 			KASSERT(xbdi->xbdi_refcnt == 0);
 			mutex_exit(&xbdi->xbdi_lock);
 			kthread_exit(0);
 			break;
 		default:
 			panic("%s: invalid state %d",
 			    xbdi->xbdi_name, xbdi->xbdi_status);
+		}
+	}
+}
 static void *
 xbdback_co_main(struct xbdback_instance *xbdi, void *obj)
+{
 	(void)obj;
 	xbdi->xbdi_req_prod = xbdi->xbdi_ring.ring_n.sring->req_prod;
 	xen_rmb(); /* ensure we see all requests up to req_prod */
 	/*
 	 * note that we'll eventually get a full ring of request.
 	 * in this case, MASK_BLKIF_IDX(req_cons) == MASK_BLKIF_IDX(req_prod)
 	 */
 	xbdi->xbdi_cont = xbdback_co_main_loop;
 	return xbdi;
+}
 /*
  * Fetch a blkif request from the ring, and pass control to the appropriate
  * continuation.
  * If someone asked for disconnection, do not fetch any more request from
  * the ring.
  */
 static void *
 xbdback_co_main_loop(struct xbdback_instance *xbdi, void *obj __unused)
+{
 	blkif_request_t *req, *reqn;
 	blkif_x86_32_request_t *req32;
 	blkif_x86_64_request_t *req64;
 	blkif_request_indirect_t *rin;
 	if (xbdi->xbdi_ring.ring_n.req_cons != xbdi->xbdi_req_prod) {
 		req = &xbdi->xbdi_xen_req;
 		memset(req, 0, sizeof(*req));
 		switch(xbdi->xbdi_proto) {
 		case XBDIP_NATIVE:
 			reqn = RING_GET_REQUEST(&xbdi->xbdi_ring.ring_n,
 			    xbdi->xbdi_ring.ring_n.req_cons);
 			req->operation = reqn->operation;
 			req->id = reqn->id;
 			break;
 		case XBDIP_32:
 			req32 = RING_GET_REQUEST(&xbdi->xbdi_ring.ring_32,
 			    xbdi->xbdi_ring.ring_n.req_cons);
 			req->operation = req32->operation;
 			req->id = req32->id;
 			break;
 		case XBDIP_64:
 			req64 = RING_GET_REQUEST(&xbdi->xbdi_ring.ring_64,
 			    xbdi->xbdi_ring.ring_n.req_cons);
 			req->operation = req64->operation;
 			req->id = req64->id;
 			break;
+		}
 		__insn_barrier();
 		XENPRINTF(("xbdback op %d req_cons 0x%x req_prod 0x%x "
 		    "resp_prod 0x%x id %" PRIu64 "\n", req->operation,
 			xbdi->xbdi_ring.ring_n.req_cons,
 			xbdi->xbdi_req_prod,
 			xbdi->xbdi_ring.ring_n.rsp_prod_pvt,
 			req->id));
 		switch (req->operation) {
 		case BLKIF_OP_INDIRECT:
 			/* just check indirect_op, rest is handled later */
 			rin = (blkif_request_indirect_t *)
 			    RING_GET_REQUEST(&xbdi->xbdi_ring.ring_n,
 				xbdi->xbdi_ring.ring_n.req_cons);
 			if (rin->indirect_op != BLKIF_OP_READ &&
 			    rin->indirect_op != BLKIF_OP_WRITE) {
 				if (ratecheck(&xbdi->xbdi_lasterr_time,
 				    &xbdback_err_intvl)) {
 					printf("%s: unknown ind operation %d\n",
 					    xbdi->xbdi_name,
 					    rin->indirect_op);
+				}
 				goto fail;
+			}
 			/* FALLTHROUGH */
 		case BLKIF_OP_READ:
 		case BLKIF_OP_WRITE:
 			xbdi->xbdi_cont = xbdback_co_io;
 			break;
 		case BLKIF_OP_FLUSH_DISKCACHE:
 			xbdi_get(xbdi);
 			xbdi->xbdi_cont = xbdback_co_cache_flush;
 			break;
 		default:
 			if (ratecheck(&xbdi->xbdi_lasterr_time,
 			    &xbdback_err_intvl)) {
 				printf("%s: unknown operation %d\n",
 				    xbdi->xbdi_name, req->operation);
+			}
 fail:
 			xbdback_send_reply(xbdi, req->id, req->operation,
 			    BLKIF_RSP_ERROR);
 			xbdi->xbdi_cont = xbdback_co_main_incr;
 			break;
+		}
 	} else {
 		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;
 	ring->req_cons++;
 	/*
 	 * Do not bother with locking here when checking for xbdi_status: if
 	 * we get a transient state, we will get the right value at
 	 * the next increment.
 	 */
 	if (xbdi->xbdi_status == DISCONNECTING)
 		xbdi->xbdi_cont = NULL;
 	else
 		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;
+}
 /*
  * 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->xbdi_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 __unused)
+{
 	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 = obj;
 	xbd_io->xio_xbdi = xbdi;
 	xbd_io->xio_operation = xbdi->xbdi_xen_req.operation;
 	xbd_io->xio_id = xbdi->xbdi_xen_req.id;
 	xbdi->xbdi_cont = xbdback_co_do_io;
-	return xbdi;
+	return xbd_io;
+}
 /*
  * 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 __unused)
+{
 	int i, error;
 	blkif_request_t *req, *reqn;
 	blkif_x86_32_request_t *req32;
 	blkif_x86_64_request_t *req64;
 	blkif_request_indirect_t *rinn;
 	blkif_x86_32_request_indirect_t *rin32;
 	blkif_x86_64_request_indirect_t *rin64;
 	req = &xbdi->xbdi_xen_req;
 	/* some sanity checks */
 	KASSERT(req->operation == BLKIF_OP_READ ||
 	    req->operation == BLKIF_OP_WRITE ||
 	    req->operation == BLKIF_OP_INDIRECT);
 	if (req->operation == BLKIF_OP_WRITE) {
 		if (xbdi->xbdi_ro) {
 			error = EROFS;
 			goto end;
+		}
+	}
 	/* copy request segments */
 	switch (xbdi->xbdi_proto) {
 	case XBDIP_NATIVE:
 		reqn = RING_GET_REQUEST(&xbdi->xbdi_ring.ring_n,
 		    xbdi->xbdi_ring.ring_n.req_cons);
 		req->handle = reqn->handle;
 		req->sector_number = reqn->sector_number;
 		if (reqn->operation == BLKIF_OP_INDIRECT) {
 			rinn = (blkif_request_indirect_t *)reqn;
 			req->operation = rinn->indirect_op;
 			req->nr_segments = (uint8_t)rinn->nr_segments;
 			if (req->nr_segments > VBD_MAX_INDIRECT_SEGMENTS)
 				goto bad_nr_segments;
 			xbdi->xbdi_in_gntref = rinn->indirect_grefs[0];
 			/* first_sect and segment grefs fetched later */
 		} else {
 			req->nr_segments = reqn->nr_segments;
 			if (req->nr_segments > BLKIF_MAX_SEGMENTS_PER_REQUEST)
 				goto bad_nr_segments;
 			for (i = 0; i < req->nr_segments; i++)
 				xbdi->xbdi_seg[i] = reqn->seg[i];
 			xbdi->xbdi_in_gntref = 0;
+		}
 		break;
 	case XBDIP_32:
 		req32 = RING_GET_REQUEST(&xbdi->xbdi_ring.ring_32,
 		    xbdi->xbdi_ring.ring_n.req_cons);
 		req->handle = req32->handle;
 		req->sector_number = req32->sector_number;
 		if (req32->operation == BLKIF_OP_INDIRECT) {
 			rin32 = (blkif_x86_32_request_indirect_t *)req32;
 			req->operation = rin32->indirect_op;
 			req->nr_segments = (uint8_t)rin32->nr_segments;
 			if (req->nr_segments > VBD_MAX_INDIRECT_SEGMENTS)
 				goto bad_nr_segments;
 			xbdi->xbdi_in_gntref = rin32->indirect_grefs[0];
 			/* first_sect and segment grefs fetched later */
 		} else {
 			req->nr_segments = req32->nr_segments;
 			if (req->nr_segments > BLKIF_MAX_SEGMENTS_PER_REQUEST)
 				goto bad_nr_segments;
 			for (i = 0; i < req->nr_segments; i++)
 				xbdi->xbdi_seg[i] = req32->seg[i];
 			xbdi->xbdi_in_gntref = 0;
+		}
 		break;
 	case XBDIP_64:
 		req64 = RING_GET_REQUEST(&xbdi->xbdi_ring.ring_64,
 		    xbdi->xbdi_ring.ring_n.req_cons);
 		req->handle = req64->handle;
 		req->sector_number = req64->sector_number;
 		if (req64->operation == BLKIF_OP_INDIRECT) {
 			rin64 = (blkif_x86_64_request_indirect_t *)req64;
 			req->nr_segments = (uint8_t)rin64->nr_segments;
 			if (req->nr_segments > VBD_MAX_INDIRECT_SEGMENTS)
 				goto bad_nr_segments;
 			xbdi->xbdi_in_gntref = rin64->indirect_grefs[0];
 			/* first_sect and segment grefs fetched later */
 		} else {
 			req->nr_segments = req64->nr_segments;
 			if (req->nr_segments > BLKIF_MAX_SEGMENTS_PER_REQUEST)
 				goto bad_nr_segments;
 			for (i = 0; i < req->nr_segments; i++)
 				xbdi->xbdi_seg[i] = req64->seg[i];
 			xbdi->xbdi_in_gntref = 0;
+		}
 		break;
+	}
 	/* Max value checked already earlier */
 	if (req->nr_segments < 1)
 		goto bad_nr_segments;
 	KASSERT(xbdi->xbdi_io == NULL);
 	xbdi->xbdi_cont = xbdback_co_io_gotio;
 	return xbdback_pool_get(&xbdback_io_pool, xbdi);
  bad_nr_segments:
 	if (ratecheck(&xbdi->xbdi_lasterr_time, &xbdback_err_intvl)) {
 		printf("%s: invalid number of segments: %d\n",
 		       xbdi->xbdi_name, req->nr_segments);
+	}
 	error = EINVAL;
 	/* FALLTHROUGH */
  end:
 	xbdback_send_reply(xbdi, xbdi->xbdi_xen_req.id,
 	    xbdi->xbdi_xen_req.operation,
 	    (error == EROFS) ? BLKIF_RSP_EOPNOTSUPP : BLKIF_RSP_ERROR);
 	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;
 	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;
+	xbd_io = obj;
 	memset(xbd_io, 0, sizeof(*xbd_io));
 	buf_init(&xbd_io->xio_buf);
 	xbd_io->xio_xbdi = xbdi;
 	xbd_io->xio_operation = req->operation;
 	xbd_io->xio_id = req->id;
 	/* If segments are on an indirect page, copy them now */
 	if (xbdi->xbdi_in_gntref) {
 		gnttab_copy_t gop;
 		paddr_t ma;
 		gop.flags = GNTCOPY_source_gref;
 		gop.len = req->nr_segments
 		    * sizeof(struct blkif_request_segment);
 		gop.source.u.ref = xbdi->xbdi_in_gntref;
 		gop.source.offset = 0;
 		gop.source.domid = xbdi->xbdi_domid;
 		ma = xbdi->xbdi_seg_dmamap->dm_segs[0].ds_addr;
 		gop.dest.offset = ma & PAGE_MASK;
 		gop.dest.domid = DOMID_SELF;
 		gop.dest.u.gmfn = ma >> PAGE_SHIFT;
 		if (HYPERVISOR_grant_table_op(GNTTABOP_copy, &gop, 1) != 0) {
 			printf("%s: GNTTABOP_copy failed\n", xbdi->xbdi_name);
 			xbdback_send_reply(xbdi, xbdi->xbdi_xen_req.id,
 			    xbdi->xbdi_xen_req.operation,
 			    BLKIF_RSP_ERROR);
 			xbdi->xbdi_cont = xbdback_co_main_incr;
 			return NULL;
+		}
+	}
 	/* Process segments */
 	bcount = 0;
 	for (int i = 0; i < req->nr_segments; i++) {
 		struct blkif_request_segment *seg = &xbdi->xbdi_seg[i];
 		xbd_io->xio_gref[i] = seg->gref;
 		bcount += (seg->last_sect - seg->first_sect + 1)
 			* VBD_BSIZE;
+	}
 	xbd_io->xio_nrma = req->nr_segments;
 	xbd_io->xio_start_offset = xbdi->xbdi_seg[0].first_sect * VBD_BSIZE;
 	KASSERT(bcount <= MAXPHYS);
 	KASSERT(xbd_io->xio_start_offset < PAGE_SIZE);
 	KASSERT(bcount + xbd_io->xio_start_offset < VBD_VA_SIZE);
 	/* Fill-in the buf */
 	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 = req->sector_number;
 	xbd_io->xio_buf.b_bcount = bcount;
 	xbd_io->xio_buf.b_data = NULL;
 	xbd_io->xio_buf.b_private = xbd_io;
 	xbdi->xbdi_cont = xbdback_co_do_io;
-	return xbdback_map_shm(xbdi->xbdi_io);
+	return xbdback_map_shm(xbd_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;
+	struct xbdback_io *xbd_io = obj;
 	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_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:
 		xbd_io->xio_buf.b_data = (void *)
 		    (xbd_io->xio_vaddr + xbd_io->xio_start_offset);
 		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);
+		}
 		/* will call xbdback_iodone() asynchronously when done */
 		bdev_strategy(&xbd_io->xio_buf);
 		xbdi->xbdi_io = NULL;
 		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 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));
 	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);
 		status = BLKIF_RSP_ERROR;
 	} else
 		status = BLKIF_RSP_OKAY;
 	xbdback_send_reply(xbdi, xbd_io->xio_id, xbd_io->xio_operation, status);
 	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
 xbdback_wakeup_thread(struct xbdback_instance *xbdi)
+{
 	mutex_enter(&xbdi->xbdi_lock);
 	/* only set RUN state when we are WAITING for work */
 	if (xbdi->xbdi_status == WAITING)
 	       xbdi->xbdi_status = RUN;
 	cv_broadcast(&xbdi->xbdi_cv);
 	mutex_exit(&xbdi->xbdi_lock);
+}
 /*
  * called once a request has completed. Place the reply in the ring and
  * notify the guest OS.
  */
 static void
 xbdback_send_reply(struct xbdback_instance *xbdi, uint64_t id,
     int op, int status)
+{
 	blkif_response_t *resp_n;
 	blkif_x86_32_response_t *resp32;
 	blkif_x86_64_response_t *resp64;
 	int notify;
 	/*
 	 * The ring can be accessed by the xbdback thread, xbdback_iodone()
 	 * handler, or any handler that triggered the shm callback. So
 	 * protect ring access via the xbdi_lock mutex.
 	 */
 	mutex_enter(&xbdi->xbdi_lock);
 	switch (xbdi->xbdi_proto) {
 	case XBDIP_NATIVE:
 		resp_n = RING_GET_RESPONSE(&xbdi->xbdi_ring.ring_n,
 		    xbdi->xbdi_ring.ring_n.rsp_prod_pvt);
 		resp_n->id        = id;
 		resp_n->operation = op;
 		resp_n->status    = status;
 		break;
 	case XBDIP_32:
 		resp32 = RING_GET_RESPONSE(&xbdi->xbdi_ring.ring_32,
 		    xbdi->xbdi_ring.ring_n.rsp_prod_pvt);
 		resp32->id        = id;
 		resp32->operation = op;
 		resp32->status    = status;
 		break;
 	case XBDIP_64:
 		resp64 = RING_GET_RESPONSE(&xbdi->xbdi_ring.ring_64,
 		    xbdi->xbdi_ring.ring_n.rsp_prod_pvt);
 		resp64->id        = id;
 		resp64->operation = op;
 		resp64->status    = status;
 		break;
+	}
 	xbdi->xbdi_ring.ring_n.rsp_prod_pvt++;
 	RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&xbdi->xbdi_ring.ring_n, notify);
 	mutex_exit(&xbdi->xbdi_lock);
 	if (notify) {
 		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;
 	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
 	s = splvm();	/* XXXSMP */
 	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_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
-		return xbdi;
+		return xbd_io;
 	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);
+		/* this will also free xbd_io via xbdback_iodone() */
 		xbdback_io_error(xbd_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 */
 		// do not retry
 		xbdi->xbdi_cont = xbdback_co_main_incr;
 		return xbdi;
+	}
+}
 /* unmap a request from our virtual address space (request is done) */
 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_xv != NULL);
 	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 pool_cache *pc,
 			      struct xbdback_instance *xbdi)
+{
 	return pool_cache_get(pc, PR_WAITOK);
+}
 /* Restore memory to a pool */
 static void
 xbdback_pool_put(struct pool_cache *pc, void *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;
 #ifdef DIAGNOSTIC
 		xbdi->xbdi_cont = (xbdback_cont_t)0xDEADBEEF;
 #endif
 		obj = (*cont)(xbdi, obj);
 #ifdef DIAGNOSTIC
 		if (xbdi->xbdi_cont == (xbdback_cont_t)0xDEADBEEF) {
 			printf("xbdback_trampoline: 0x%lx didn't set "
 			       "xbdi->xbdi_cont!\n", (long)cont);
 			panic("xbdback_trampoline: bad continuation");
+		}
 #endif
+	}
+}