1 /* Xenbus code for blkif backend
2 Copyright (C) 2005 Rusty Russell <rusty@rustcorp.com.au>
3 Copyright (C) 2005 XenSource Ltd
5 This program is free software; you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by
7 the Free Software Foundation; either version 2 of the License, or
8 (at your option) any later version.
10 This program is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU General Public License for more details.
18 #include <linux/module.h>
19 #include <linux/kthread.h>
20 #include <xen/events.h>
21 #include <xen/grant_table.h>
25 struct xenbus_device *dev;
26 struct xen_blkif *blkif;
27 struct xenbus_watch backend_watch;
33 static struct kmem_cache *xen_blkif_cachep;
34 static void connect(struct backend_info *);
35 static int connect_ring(struct backend_info *);
36 static void backend_changed(struct xenbus_watch *, const char **,
39 struct xenbus_device *xen_blkbk_xenbus(struct backend_info *be)
44 static int blkback_name(struct xen_blkif *blkif, char *buf)
46 char *devpath, *devname;
47 struct xenbus_device *dev = blkif->be->dev;
49 devpath = xenbus_read(XBT_NIL, dev->nodename, "dev", NULL);
51 return PTR_ERR(devpath);
53 devname = strstr(devpath, "/dev/");
55 devname += strlen("/dev/");
59 snprintf(buf, TASK_COMM_LEN, "blkback.%d.%s", blkif->domid, devname);
65 static void xen_update_blkif_status(struct xen_blkif *blkif)
68 char name[TASK_COMM_LEN];
70 /* Not ready to connect? */
71 if (!blkif->irq || !blkif->vbd.bdev)
74 /* Already connected? */
75 if (blkif->be->dev->state == XenbusStateConnected)
78 /* Attempt to connect: exit if we fail to. */
80 if (blkif->be->dev->state != XenbusStateConnected)
83 err = blkback_name(blkif, name);
85 xenbus_dev_error(blkif->be->dev, err, "get blkback dev name");
89 err = filemap_write_and_wait(blkif->vbd.bdev->bd_inode->i_mapping);
91 xenbus_dev_error(blkif->be->dev, err, "block flush");
94 invalidate_inode_pages2(blkif->vbd.bdev->bd_inode->i_mapping);
96 blkif->xenblkd = kthread_run(xen_blkif_schedule, blkif, "%s", name);
97 if (IS_ERR(blkif->xenblkd)) {
98 err = PTR_ERR(blkif->xenblkd);
99 blkif->xenblkd = NULL;
100 xenbus_dev_error(blkif->be->dev, err, "start xenblkd");
105 static struct xen_blkif *xen_blkif_alloc(domid_t domid)
107 struct xen_blkif *blkif;
108 struct pending_req *req, *n;
111 BUILD_BUG_ON(MAX_INDIRECT_PAGES > BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST);
113 blkif = kmem_cache_zalloc(xen_blkif_cachep, GFP_KERNEL);
115 return ERR_PTR(-ENOMEM);
117 blkif->domid = domid;
118 spin_lock_init(&blkif->blk_ring_lock);
119 atomic_set(&blkif->refcnt, 1);
120 init_waitqueue_head(&blkif->wq);
121 init_completion(&blkif->drain_complete);
122 atomic_set(&blkif->drain, 0);
123 blkif->st_print = jiffies;
124 init_waitqueue_head(&blkif->waiting_to_free);
125 blkif->persistent_gnts.rb_node = NULL;
126 spin_lock_init(&blkif->free_pages_lock);
127 INIT_LIST_HEAD(&blkif->free_pages);
128 INIT_LIST_HEAD(&blkif->persistent_purge_list);
129 blkif->free_pages_num = 0;
130 atomic_set(&blkif->persistent_gnt_in_use, 0);
131 atomic_set(&blkif->inflight, 0);
132 INIT_WORK(&blkif->persistent_purge_work, xen_blkbk_unmap_purged_grants);
134 INIT_LIST_HEAD(&blkif->pending_free);
136 for (i = 0; i < XEN_BLKIF_REQS; i++) {
137 req = kzalloc(sizeof(*req), GFP_KERNEL);
140 list_add_tail(&req->free_list,
141 &blkif->pending_free);
142 for (j = 0; j < MAX_INDIRECT_SEGMENTS; j++) {
143 req->segments[j] = kzalloc(sizeof(*req->segments[0]),
145 if (!req->segments[j])
148 for (j = 0; j < MAX_INDIRECT_PAGES; j++) {
149 req->indirect_pages[j] = kzalloc(sizeof(*req->indirect_pages[0]),
151 if (!req->indirect_pages[j])
155 spin_lock_init(&blkif->pending_free_lock);
156 init_waitqueue_head(&blkif->pending_free_wq);
157 init_waitqueue_head(&blkif->shutdown_wq);
162 list_for_each_entry_safe(req, n, &blkif->pending_free, free_list) {
163 list_del(&req->free_list);
164 for (j = 0; j < MAX_INDIRECT_SEGMENTS; j++) {
165 if (!req->segments[j])
167 kfree(req->segments[j]);
169 for (j = 0; j < MAX_INDIRECT_PAGES; j++) {
170 if (!req->indirect_pages[j])
172 kfree(req->indirect_pages[j]);
177 kmem_cache_free(xen_blkif_cachep, blkif);
179 return ERR_PTR(-ENOMEM);
182 static int xen_blkif_map(struct xen_blkif *blkif, unsigned long shared_page,
187 /* Already connected through? */
191 err = xenbus_map_ring_valloc(blkif->be->dev, shared_page, &blkif->blk_ring);
195 switch (blkif->blk_protocol) {
196 case BLKIF_PROTOCOL_NATIVE:
198 struct blkif_sring *sring;
199 sring = (struct blkif_sring *)blkif->blk_ring;
200 BACK_RING_INIT(&blkif->blk_rings.native, sring, PAGE_SIZE);
203 case BLKIF_PROTOCOL_X86_32:
205 struct blkif_x86_32_sring *sring_x86_32;
206 sring_x86_32 = (struct blkif_x86_32_sring *)blkif->blk_ring;
207 BACK_RING_INIT(&blkif->blk_rings.x86_32, sring_x86_32, PAGE_SIZE);
210 case BLKIF_PROTOCOL_X86_64:
212 struct blkif_x86_64_sring *sring_x86_64;
213 sring_x86_64 = (struct blkif_x86_64_sring *)blkif->blk_ring;
214 BACK_RING_INIT(&blkif->blk_rings.x86_64, sring_x86_64, PAGE_SIZE);
221 err = bind_interdomain_evtchn_to_irqhandler(blkif->domid, evtchn,
223 "blkif-backend", blkif);
225 xenbus_unmap_ring_vfree(blkif->be->dev, blkif->blk_ring);
226 blkif->blk_rings.common.sring = NULL;
234 static void xen_blkif_disconnect(struct xen_blkif *blkif)
236 if (blkif->xenblkd) {
237 kthread_stop(blkif->xenblkd);
238 wake_up(&blkif->shutdown_wq);
239 blkif->xenblkd = NULL;
242 atomic_dec(&blkif->refcnt);
243 wait_event(blkif->waiting_to_free, atomic_read(&blkif->refcnt) == 0);
244 atomic_inc(&blkif->refcnt);
247 unbind_from_irqhandler(blkif->irq, blkif);
251 if (blkif->blk_rings.common.sring) {
252 xenbus_unmap_ring_vfree(blkif->be->dev, blkif->blk_ring);
253 blkif->blk_rings.common.sring = NULL;
257 static void xen_blkif_free(struct xen_blkif *blkif)
259 struct pending_req *req, *n;
262 if (!atomic_dec_and_test(&blkif->refcnt))
265 /* Remove all persistent grants and the cache of ballooned pages. */
266 xen_blkbk_free_caches(blkif);
268 /* Make sure everything is drained before shutting down */
269 BUG_ON(blkif->persistent_gnt_c != 0);
270 BUG_ON(atomic_read(&blkif->persistent_gnt_in_use) != 0);
271 BUG_ON(blkif->free_pages_num != 0);
272 BUG_ON(!list_empty(&blkif->persistent_purge_list));
273 BUG_ON(!list_empty(&blkif->free_pages));
274 BUG_ON(!RB_EMPTY_ROOT(&blkif->persistent_gnts));
276 /* Check that there is no request in use */
277 list_for_each_entry_safe(req, n, &blkif->pending_free, free_list) {
278 list_del(&req->free_list);
280 for (j = 0; j < MAX_INDIRECT_SEGMENTS; j++)
281 kfree(req->segments[j]);
283 for (j = 0; j < MAX_INDIRECT_PAGES; j++)
284 kfree(req->indirect_pages[j]);
290 WARN_ON(i != XEN_BLKIF_REQS);
292 kmem_cache_free(xen_blkif_cachep, blkif);
295 int __init xen_blkif_interface_init(void)
297 xen_blkif_cachep = kmem_cache_create("blkif_cache",
298 sizeof(struct xen_blkif),
300 if (!xen_blkif_cachep)
307 * sysfs interface for VBD I/O requests
310 #define VBD_SHOW(name, format, args...) \
311 static ssize_t show_##name(struct device *_dev, \
312 struct device_attribute *attr, \
315 struct xenbus_device *dev = to_xenbus_device(_dev); \
316 struct backend_info *be = dev_get_drvdata(&dev->dev); \
318 return sprintf(buf, format, ##args); \
320 static DEVICE_ATTR(name, S_IRUGO, show_##name, NULL)
322 VBD_SHOW(oo_req, "%llu\n", be->blkif->st_oo_req);
323 VBD_SHOW(rd_req, "%llu\n", be->blkif->st_rd_req);
324 VBD_SHOW(wr_req, "%llu\n", be->blkif->st_wr_req);
325 VBD_SHOW(f_req, "%llu\n", be->blkif->st_f_req);
326 VBD_SHOW(ds_req, "%llu\n", be->blkif->st_ds_req);
327 VBD_SHOW(rd_sect, "%llu\n", be->blkif->st_rd_sect);
328 VBD_SHOW(wr_sect, "%llu\n", be->blkif->st_wr_sect);
330 static struct attribute *xen_vbdstat_attrs[] = {
331 &dev_attr_oo_req.attr,
332 &dev_attr_rd_req.attr,
333 &dev_attr_wr_req.attr,
334 &dev_attr_f_req.attr,
335 &dev_attr_ds_req.attr,
336 &dev_attr_rd_sect.attr,
337 &dev_attr_wr_sect.attr,
341 static struct attribute_group xen_vbdstat_group = {
342 .name = "statistics",
343 .attrs = xen_vbdstat_attrs,
346 VBD_SHOW(physical_device, "%x:%x\n", be->major, be->minor);
347 VBD_SHOW(mode, "%s\n", be->mode);
349 static int xenvbd_sysfs_addif(struct xenbus_device *dev)
353 error = device_create_file(&dev->dev, &dev_attr_physical_device);
357 error = device_create_file(&dev->dev, &dev_attr_mode);
361 error = sysfs_create_group(&dev->dev.kobj, &xen_vbdstat_group);
367 fail3: sysfs_remove_group(&dev->dev.kobj, &xen_vbdstat_group);
368 fail2: device_remove_file(&dev->dev, &dev_attr_mode);
369 fail1: device_remove_file(&dev->dev, &dev_attr_physical_device);
373 static void xenvbd_sysfs_delif(struct xenbus_device *dev)
375 sysfs_remove_group(&dev->dev.kobj, &xen_vbdstat_group);
376 device_remove_file(&dev->dev, &dev_attr_mode);
377 device_remove_file(&dev->dev, &dev_attr_physical_device);
381 static void xen_vbd_free(struct xen_vbd *vbd)
384 blkdev_put(vbd->bdev, vbd->readonly ? FMODE_READ : FMODE_WRITE);
388 static int xen_vbd_create(struct xen_blkif *blkif, blkif_vdev_t handle,
389 unsigned major, unsigned minor, int readonly,
393 struct block_device *bdev;
394 struct request_queue *q;
397 vbd->handle = handle;
398 vbd->readonly = readonly;
401 vbd->pdevice = MKDEV(major, minor);
403 bdev = blkdev_get_by_dev(vbd->pdevice, vbd->readonly ?
404 FMODE_READ : FMODE_WRITE, NULL);
407 DPRINTK("xen_vbd_create: device %08x could not be opened.\n",
413 if (vbd->bdev->bd_disk == NULL) {
414 DPRINTK("xen_vbd_create: device %08x doesn't exist.\n",
419 vbd->size = vbd_sz(vbd);
421 if (vbd->bdev->bd_disk->flags & GENHD_FL_CD || cdrom)
422 vbd->type |= VDISK_CDROM;
423 if (vbd->bdev->bd_disk->flags & GENHD_FL_REMOVABLE)
424 vbd->type |= VDISK_REMOVABLE;
426 q = bdev_get_queue(bdev);
427 if (q && q->flush_flags)
428 vbd->flush_support = true;
430 if (q && blk_queue_secdiscard(q))
431 vbd->discard_secure = true;
433 DPRINTK("Successful creation of handle=%04x (dom=%u)\n",
434 handle, blkif->domid);
437 static int xen_blkbk_remove(struct xenbus_device *dev)
439 struct backend_info *be = dev_get_drvdata(&dev->dev);
443 if (be->major || be->minor)
444 xenvbd_sysfs_delif(dev);
446 if (be->backend_watch.node) {
447 unregister_xenbus_watch(&be->backend_watch);
448 kfree(be->backend_watch.node);
449 be->backend_watch.node = NULL;
453 xen_blkif_disconnect(be->blkif);
454 xen_vbd_free(&be->blkif->vbd);
455 xen_blkif_free(be->blkif);
461 dev_set_drvdata(&dev->dev, NULL);
465 int xen_blkbk_flush_diskcache(struct xenbus_transaction xbt,
466 struct backend_info *be, int state)
468 struct xenbus_device *dev = be->dev;
471 err = xenbus_printf(xbt, dev->nodename, "feature-flush-cache",
474 dev_warn(&dev->dev, "writing feature-flush-cache (%d)", err);
479 static void xen_blkbk_discard(struct xenbus_transaction xbt, struct backend_info *be)
481 struct xenbus_device *dev = be->dev;
482 struct xen_blkif *blkif = be->blkif;
485 struct block_device *bdev = be->blkif->vbd.bdev;
486 struct request_queue *q = bdev_get_queue(bdev);
488 if (blk_queue_discard(q)) {
489 err = xenbus_printf(xbt, dev->nodename,
490 "discard-granularity", "%u",
491 q->limits.discard_granularity);
493 dev_warn(&dev->dev, "writing discard-granularity (%d)", err);
496 err = xenbus_printf(xbt, dev->nodename,
497 "discard-alignment", "%u",
498 q->limits.discard_alignment);
500 dev_warn(&dev->dev, "writing discard-alignment (%d)", err);
505 err = xenbus_printf(xbt, dev->nodename,
506 "discard-secure", "%d",
507 blkif->vbd.discard_secure);
509 dev_warn(&dev->dev, "writing discard-secure (%d)", err);
513 err = xenbus_printf(xbt, dev->nodename, "feature-discard",
516 dev_warn(&dev->dev, "writing feature-discard (%d)", err);
518 int xen_blkbk_barrier(struct xenbus_transaction xbt,
519 struct backend_info *be, int state)
521 struct xenbus_device *dev = be->dev;
524 err = xenbus_printf(xbt, dev->nodename, "feature-barrier",
527 dev_warn(&dev->dev, "writing feature-barrier (%d)", err);
533 * Entry point to this code when a new device is created. Allocate the basic
534 * structures, and watch the store waiting for the hotplug scripts to tell us
535 * the device's physical major and minor numbers. Switch to InitWait.
537 static int xen_blkbk_probe(struct xenbus_device *dev,
538 const struct xenbus_device_id *id)
541 struct backend_info *be = kzalloc(sizeof(struct backend_info),
544 xenbus_dev_fatal(dev, -ENOMEM,
545 "allocating backend structure");
549 dev_set_drvdata(&dev->dev, be);
551 be->blkif = xen_blkif_alloc(dev->otherend_id);
552 if (IS_ERR(be->blkif)) {
553 err = PTR_ERR(be->blkif);
555 xenbus_dev_fatal(dev, err, "creating block interface");
559 /* setup back pointer */
562 err = xenbus_watch_pathfmt(dev, &be->backend_watch, backend_changed,
563 "%s/%s", dev->nodename, "physical-device");
567 err = xenbus_switch_state(dev, XenbusStateInitWait);
575 xen_blkbk_remove(dev);
581 * Callback received when the hotplug scripts have placed the physical-device
582 * node. Read it and the mode node, and create a vbd. If the frontend is
585 static void backend_changed(struct xenbus_watch *watch,
586 const char **vec, unsigned int len)
591 struct backend_info *be
592 = container_of(watch, struct backend_info, backend_watch);
593 struct xenbus_device *dev = be->dev;
595 unsigned long handle;
600 err = xenbus_scanf(XBT_NIL, dev->nodename, "physical-device", "%x:%x",
602 if (XENBUS_EXIST_ERR(err)) {
604 * Since this watch will fire once immediately after it is
605 * registered, we expect this. Ignore it, and wait for the
611 xenbus_dev_fatal(dev, err, "reading physical-device");
615 if (be->major | be->minor) {
616 if (be->major != major || be->minor != minor)
617 pr_warn(DRV_PFX "changing physical device (from %x:%x to %x:%x) not supported.\n",
618 be->major, be->minor, major, minor);
622 be->mode = xenbus_read(XBT_NIL, dev->nodename, "mode", NULL);
623 if (IS_ERR(be->mode)) {
624 err = PTR_ERR(be->mode);
626 xenbus_dev_fatal(dev, err, "reading mode");
630 device_type = xenbus_read(XBT_NIL, dev->otherend, "device-type", NULL);
631 if (!IS_ERR(device_type)) {
632 cdrom = strcmp(device_type, "cdrom") == 0;
636 /* Front end dir is a number, which is used as the handle. */
637 err = kstrtoul(strrchr(dev->otherend, '/') + 1, 0, &handle);
644 err = xen_vbd_create(be->blkif, handle, major, minor,
645 !strchr(be->mode, 'w'), cdrom);
648 xenbus_dev_fatal(dev, err, "creating vbd structure");
650 err = xenvbd_sysfs_addif(dev);
652 xen_vbd_free(&be->blkif->vbd);
653 xenbus_dev_fatal(dev, err, "creating sysfs entries");
663 /* We're potentially connected now */
664 xen_update_blkif_status(be->blkif);
670 * Callback received when the frontend's state changes.
672 static void frontend_changed(struct xenbus_device *dev,
673 enum xenbus_state frontend_state)
675 struct backend_info *be = dev_get_drvdata(&dev->dev);
678 DPRINTK("%s", xenbus_strstate(frontend_state));
680 switch (frontend_state) {
681 case XenbusStateInitialising:
682 if (dev->state == XenbusStateClosed) {
683 pr_info(DRV_PFX "%s: prepare for reconnect\n",
685 xenbus_switch_state(dev, XenbusStateInitWait);
689 case XenbusStateInitialised:
690 case XenbusStateConnected:
692 * Ensure we connect even when two watches fire in
693 * close succession and we miss the intermediate value
696 if (dev->state == XenbusStateConnected)
700 * Enforce precondition before potential leak point.
701 * xen_blkif_disconnect() is idempotent.
703 xen_blkif_disconnect(be->blkif);
705 err = connect_ring(be);
708 xen_update_blkif_status(be->blkif);
711 case XenbusStateClosing:
712 xenbus_switch_state(dev, XenbusStateClosing);
715 case XenbusStateClosed:
716 xen_blkif_disconnect(be->blkif);
717 xenbus_switch_state(dev, XenbusStateClosed);
718 if (xenbus_dev_is_online(dev))
720 /* fall through if not online */
721 case XenbusStateUnknown:
722 /* implies xen_blkif_disconnect() via xen_blkbk_remove() */
723 device_unregister(&dev->dev);
727 xenbus_dev_fatal(dev, -EINVAL, "saw state %d at frontend",
734 /* ** Connection ** */
738 * Write the physical details regarding the block device to the store, and
739 * switch to Connected state.
741 static void connect(struct backend_info *be)
743 struct xenbus_transaction xbt;
745 struct xenbus_device *dev = be->dev;
747 DPRINTK("%s", dev->otherend);
749 /* Supply the information about the device the frontend needs */
751 err = xenbus_transaction_start(&xbt);
753 xenbus_dev_fatal(dev, err, "starting transaction");
757 /* If we can't advertise it is OK. */
758 xen_blkbk_flush_diskcache(xbt, be, be->blkif->vbd.flush_support);
760 xen_blkbk_discard(xbt, be);
762 xen_blkbk_barrier(xbt, be, be->blkif->vbd.flush_support);
764 err = xenbus_printf(xbt, dev->nodename, "feature-persistent", "%u", 1);
766 xenbus_dev_fatal(dev, err, "writing %s/feature-persistent",
770 err = xenbus_printf(xbt, dev->nodename, "feature-max-indirect-segments", "%u",
771 MAX_INDIRECT_SEGMENTS);
773 dev_warn(&dev->dev, "writing %s/feature-max-indirect-segments (%d)",
776 err = xenbus_printf(xbt, dev->nodename, "sectors", "%llu",
777 (unsigned long long)vbd_sz(&be->blkif->vbd));
779 xenbus_dev_fatal(dev, err, "writing %s/sectors",
784 /* FIXME: use a typename instead */
785 err = xenbus_printf(xbt, dev->nodename, "info", "%u",
786 be->blkif->vbd.type |
787 (be->blkif->vbd.readonly ? VDISK_READONLY : 0));
789 xenbus_dev_fatal(dev, err, "writing %s/info",
793 err = xenbus_printf(xbt, dev->nodename, "sector-size", "%lu",
795 bdev_logical_block_size(be->blkif->vbd.bdev));
797 xenbus_dev_fatal(dev, err, "writing %s/sector-size",
801 err = xenbus_printf(xbt, dev->nodename, "physical-sector-size", "%u",
802 bdev_physical_block_size(be->blkif->vbd.bdev));
804 xenbus_dev_error(dev, err, "writing %s/physical-sector-size",
807 err = xenbus_transaction_end(xbt, 0);
811 xenbus_dev_fatal(dev, err, "ending transaction");
813 err = xenbus_switch_state(dev, XenbusStateConnected);
815 xenbus_dev_fatal(dev, err, "%s: switching to Connected state",
820 xenbus_transaction_end(xbt, 1);
824 static int connect_ring(struct backend_info *be)
826 struct xenbus_device *dev = be->dev;
827 unsigned long ring_ref;
829 unsigned int pers_grants;
830 char protocol[64] = "";
833 DPRINTK("%s", dev->otherend);
835 err = xenbus_gather(XBT_NIL, dev->otherend, "ring-ref", "%lu",
836 &ring_ref, "event-channel", "%u", &evtchn, NULL);
838 xenbus_dev_fatal(dev, err,
839 "reading %s/ring-ref and event-channel",
844 be->blkif->blk_protocol = BLKIF_PROTOCOL_NATIVE;
845 err = xenbus_gather(XBT_NIL, dev->otherend, "protocol",
846 "%63s", protocol, NULL);
848 strcpy(protocol, "unspecified, assuming native");
849 else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_NATIVE))
850 be->blkif->blk_protocol = BLKIF_PROTOCOL_NATIVE;
851 else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_32))
852 be->blkif->blk_protocol = BLKIF_PROTOCOL_X86_32;
853 else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_64))
854 be->blkif->blk_protocol = BLKIF_PROTOCOL_X86_64;
856 xenbus_dev_fatal(dev, err, "unknown fe protocol %s", protocol);
859 err = xenbus_gather(XBT_NIL, dev->otherend,
860 "feature-persistent", "%u",
865 be->blkif->vbd.feature_gnt_persistent = pers_grants;
866 be->blkif->vbd.overflow_max_grants = 0;
868 pr_info(DRV_PFX "ring-ref %ld, event-channel %d, protocol %d (%s) %s\n",
869 ring_ref, evtchn, be->blkif->blk_protocol, protocol,
870 pers_grants ? "persistent grants" : "");
872 /* Map the shared frame, irq etc. */
873 err = xen_blkif_map(be->blkif, ring_ref, evtchn);
875 xenbus_dev_fatal(dev, err, "mapping ring-ref %lu port %u",
884 /* ** Driver Registration ** */
887 static const struct xenbus_device_id xen_blkbk_ids[] = {
893 static DEFINE_XENBUS_DRIVER(xen_blkbk, ,
894 .probe = xen_blkbk_probe,
895 .remove = xen_blkbk_remove,
896 .otherend_changed = frontend_changed
900 int xen_blkif_xenbus_init(void)
902 return xenbus_register_backend(&xen_blkbk_driver);