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, 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");
104 static struct xen_blkif *xen_blkif_alloc(domid_t domid)
106 struct xen_blkif *blkif;
108 blkif = kmem_cache_zalloc(xen_blkif_cachep, GFP_KERNEL);
110 return ERR_PTR(-ENOMEM);
112 blkif->domid = domid;
113 spin_lock_init(&blkif->blk_ring_lock);
114 atomic_set(&blkif->refcnt, 1);
115 init_waitqueue_head(&blkif->wq);
116 init_completion(&blkif->drain_complete);
117 atomic_set(&blkif->drain, 0);
118 blkif->st_print = jiffies;
119 init_waitqueue_head(&blkif->waiting_to_free);
120 blkif->persistent_gnts.rb_node = NULL;
125 static int xen_blkif_map(struct xen_blkif *blkif, unsigned long shared_page,
130 /* Already connected through? */
134 err = xenbus_map_ring_valloc(blkif->be->dev, shared_page, &blkif->blk_ring);
138 switch (blkif->blk_protocol) {
139 case BLKIF_PROTOCOL_NATIVE:
141 struct blkif_sring *sring;
142 sring = (struct blkif_sring *)blkif->blk_ring;
143 BACK_RING_INIT(&blkif->blk_rings.native, sring, PAGE_SIZE);
146 case BLKIF_PROTOCOL_X86_32:
148 struct blkif_x86_32_sring *sring_x86_32;
149 sring_x86_32 = (struct blkif_x86_32_sring *)blkif->blk_ring;
150 BACK_RING_INIT(&blkif->blk_rings.x86_32, sring_x86_32, PAGE_SIZE);
153 case BLKIF_PROTOCOL_X86_64:
155 struct blkif_x86_64_sring *sring_x86_64;
156 sring_x86_64 = (struct blkif_x86_64_sring *)blkif->blk_ring;
157 BACK_RING_INIT(&blkif->blk_rings.x86_64, sring_x86_64, PAGE_SIZE);
164 err = bind_interdomain_evtchn_to_irqhandler(blkif->domid, evtchn,
166 "blkif-backend", blkif);
168 xenbus_unmap_ring_vfree(blkif->be->dev, blkif->blk_ring);
169 blkif->blk_rings.common.sring = NULL;
177 static void xen_blkif_disconnect(struct xen_blkif *blkif)
179 if (blkif->xenblkd) {
180 kthread_stop(blkif->xenblkd);
181 blkif->xenblkd = NULL;
184 atomic_dec(&blkif->refcnt);
185 wait_event(blkif->waiting_to_free, atomic_read(&blkif->refcnt) == 0);
186 atomic_inc(&blkif->refcnt);
189 unbind_from_irqhandler(blkif->irq, blkif);
193 if (blkif->blk_rings.common.sring) {
194 xenbus_unmap_ring_vfree(blkif->be->dev, blkif->blk_ring);
195 blkif->blk_rings.common.sring = NULL;
199 static void xen_blkif_free(struct xen_blkif *blkif)
201 if (!atomic_dec_and_test(&blkif->refcnt))
203 kmem_cache_free(xen_blkif_cachep, blkif);
206 int __init xen_blkif_interface_init(void)
208 xen_blkif_cachep = kmem_cache_create("blkif_cache",
209 sizeof(struct xen_blkif),
211 if (!xen_blkif_cachep)
218 * sysfs interface for VBD I/O requests
221 #define VBD_SHOW(name, format, args...) \
222 static ssize_t show_##name(struct device *_dev, \
223 struct device_attribute *attr, \
226 struct xenbus_device *dev = to_xenbus_device(_dev); \
227 struct backend_info *be = dev_get_drvdata(&dev->dev); \
229 return sprintf(buf, format, ##args); \
231 static DEVICE_ATTR(name, S_IRUGO, show_##name, NULL)
233 VBD_SHOW(oo_req, "%llu\n", be->blkif->st_oo_req);
234 VBD_SHOW(rd_req, "%llu\n", be->blkif->st_rd_req);
235 VBD_SHOW(wr_req, "%llu\n", be->blkif->st_wr_req);
236 VBD_SHOW(f_req, "%llu\n", be->blkif->st_f_req);
237 VBD_SHOW(ds_req, "%llu\n", be->blkif->st_ds_req);
238 VBD_SHOW(rd_sect, "%llu\n", be->blkif->st_rd_sect);
239 VBD_SHOW(wr_sect, "%llu\n", be->blkif->st_wr_sect);
241 static struct attribute *xen_vbdstat_attrs[] = {
242 &dev_attr_oo_req.attr,
243 &dev_attr_rd_req.attr,
244 &dev_attr_wr_req.attr,
245 &dev_attr_f_req.attr,
246 &dev_attr_ds_req.attr,
247 &dev_attr_rd_sect.attr,
248 &dev_attr_wr_sect.attr,
252 static struct attribute_group xen_vbdstat_group = {
253 .name = "statistics",
254 .attrs = xen_vbdstat_attrs,
257 VBD_SHOW(physical_device, "%x:%x\n", be->major, be->minor);
258 VBD_SHOW(mode, "%s\n", be->mode);
260 static int xenvbd_sysfs_addif(struct xenbus_device *dev)
264 error = device_create_file(&dev->dev, &dev_attr_physical_device);
268 error = device_create_file(&dev->dev, &dev_attr_mode);
272 error = sysfs_create_group(&dev->dev.kobj, &xen_vbdstat_group);
278 fail3: sysfs_remove_group(&dev->dev.kobj, &xen_vbdstat_group);
279 fail2: device_remove_file(&dev->dev, &dev_attr_mode);
280 fail1: device_remove_file(&dev->dev, &dev_attr_physical_device);
284 static void xenvbd_sysfs_delif(struct xenbus_device *dev)
286 sysfs_remove_group(&dev->dev.kobj, &xen_vbdstat_group);
287 device_remove_file(&dev->dev, &dev_attr_mode);
288 device_remove_file(&dev->dev, &dev_attr_physical_device);
292 static void xen_vbd_free(struct xen_vbd *vbd)
295 blkdev_put(vbd->bdev, vbd->readonly ? FMODE_READ : FMODE_WRITE);
299 static int xen_vbd_create(struct xen_blkif *blkif, blkif_vdev_t handle,
300 unsigned major, unsigned minor, int readonly,
304 struct block_device *bdev;
305 struct request_queue *q;
308 vbd->handle = handle;
309 vbd->readonly = readonly;
312 vbd->pdevice = MKDEV(major, minor);
314 bdev = blkdev_get_by_dev(vbd->pdevice, vbd->readonly ?
315 FMODE_READ : FMODE_WRITE, NULL);
318 DPRINTK("xen_vbd_create: device %08x could not be opened.\n",
324 if (vbd->bdev->bd_disk == NULL) {
325 DPRINTK("xen_vbd_create: device %08x doesn't exist.\n",
330 vbd->size = vbd_sz(vbd);
332 if (vbd->bdev->bd_disk->flags & GENHD_FL_CD || cdrom)
333 vbd->type |= VDISK_CDROM;
334 if (vbd->bdev->bd_disk->flags & GENHD_FL_REMOVABLE)
335 vbd->type |= VDISK_REMOVABLE;
337 q = bdev_get_queue(bdev);
338 if (q && q->flush_flags)
339 vbd->flush_support = true;
341 if (q && blk_queue_secdiscard(q))
342 vbd->discard_secure = true;
344 DPRINTK("Successful creation of handle=%04x (dom=%u)\n",
345 handle, blkif->domid);
348 static int xen_blkbk_remove(struct xenbus_device *dev)
350 struct backend_info *be = dev_get_drvdata(&dev->dev);
354 if (be->major || be->minor)
355 xenvbd_sysfs_delif(dev);
357 if (be->backend_watch.node) {
358 unregister_xenbus_watch(&be->backend_watch);
359 kfree(be->backend_watch.node);
360 be->backend_watch.node = NULL;
364 xen_blkif_disconnect(be->blkif);
365 xen_vbd_free(&be->blkif->vbd);
366 xen_blkif_free(be->blkif);
372 dev_set_drvdata(&dev->dev, NULL);
376 int xen_blkbk_flush_diskcache(struct xenbus_transaction xbt,
377 struct backend_info *be, int state)
379 struct xenbus_device *dev = be->dev;
382 err = xenbus_printf(xbt, dev->nodename, "feature-flush-cache",
385 dev_warn(&dev->dev, "writing feature-flush-cache (%d)", err);
390 static void xen_blkbk_discard(struct xenbus_transaction xbt, struct backend_info *be)
392 struct xenbus_device *dev = be->dev;
393 struct xen_blkif *blkif = be->blkif;
396 struct block_device *bdev = be->blkif->vbd.bdev;
397 struct request_queue *q = bdev_get_queue(bdev);
399 if (blk_queue_discard(q)) {
400 err = xenbus_printf(xbt, dev->nodename,
401 "discard-granularity", "%u",
402 q->limits.discard_granularity);
404 dev_warn(&dev->dev, "writing discard-granularity (%d)", err);
407 err = xenbus_printf(xbt, dev->nodename,
408 "discard-alignment", "%u",
409 q->limits.discard_alignment);
411 dev_warn(&dev->dev, "writing discard-alignment (%d)", err);
416 err = xenbus_printf(xbt, dev->nodename,
417 "discard-secure", "%d",
418 blkif->vbd.discard_secure);
420 dev_warn(&dev->dev, "writing discard-secure (%d)", err);
424 err = xenbus_printf(xbt, dev->nodename, "feature-discard",
427 dev_warn(&dev->dev, "writing feature-discard (%d)", err);
429 int xen_blkbk_barrier(struct xenbus_transaction xbt,
430 struct backend_info *be, int state)
432 struct xenbus_device *dev = be->dev;
435 err = xenbus_printf(xbt, dev->nodename, "feature-barrier",
438 dev_warn(&dev->dev, "writing feature-barrier (%d)", err);
444 * Entry point to this code when a new device is created. Allocate the basic
445 * structures, and watch the store waiting for the hotplug scripts to tell us
446 * the device's physical major and minor numbers. Switch to InitWait.
448 static int xen_blkbk_probe(struct xenbus_device *dev,
449 const struct xenbus_device_id *id)
452 struct backend_info *be = kzalloc(sizeof(struct backend_info),
455 xenbus_dev_fatal(dev, -ENOMEM,
456 "allocating backend structure");
460 dev_set_drvdata(&dev->dev, be);
462 be->blkif = xen_blkif_alloc(dev->otherend_id);
463 if (IS_ERR(be->blkif)) {
464 err = PTR_ERR(be->blkif);
466 xenbus_dev_fatal(dev, err, "creating block interface");
470 /* setup back pointer */
473 err = xenbus_watch_pathfmt(dev, &be->backend_watch, backend_changed,
474 "%s/%s", dev->nodename, "physical-device");
478 err = xenbus_switch_state(dev, XenbusStateInitWait);
486 xen_blkbk_remove(dev);
492 * Callback received when the hotplug scripts have placed the physical-device
493 * node. Read it and the mode node, and create a vbd. If the frontend is
496 static void backend_changed(struct xenbus_watch *watch,
497 const char **vec, unsigned int len)
502 struct backend_info *be
503 = container_of(watch, struct backend_info, backend_watch);
504 struct xenbus_device *dev = be->dev;
506 unsigned long handle;
511 err = xenbus_scanf(XBT_NIL, dev->nodename, "physical-device", "%x:%x",
513 if (XENBUS_EXIST_ERR(err)) {
515 * Since this watch will fire once immediately after it is
516 * registered, we expect this. Ignore it, and wait for the
522 xenbus_dev_fatal(dev, err, "reading physical-device");
526 if (be->major | be->minor) {
527 if (be->major != major || be->minor != minor)
528 pr_warn(DRV_PFX "changing physical device (from %x:%x to %x:%x) not supported.\n",
529 be->major, be->minor, major, minor);
533 be->mode = xenbus_read(XBT_NIL, dev->nodename, "mode", NULL);
534 if (IS_ERR(be->mode)) {
535 err = PTR_ERR(be->mode);
537 xenbus_dev_fatal(dev, err, "reading mode");
541 device_type = xenbus_read(XBT_NIL, dev->otherend, "device-type", NULL);
542 if (!IS_ERR(device_type)) {
543 cdrom = strcmp(device_type, "cdrom") == 0;
547 /* Front end dir is a number, which is used as the handle. */
548 err = strict_strtoul(strrchr(dev->otherend, '/') + 1, 0, &handle);
555 err = xen_vbd_create(be->blkif, handle, major, minor,
556 !strchr(be->mode, 'w'), cdrom);
559 xenbus_dev_fatal(dev, err, "creating vbd structure");
561 err = xenvbd_sysfs_addif(dev);
563 xen_vbd_free(&be->blkif->vbd);
564 xenbus_dev_fatal(dev, err, "creating sysfs entries");
574 /* We're potentially connected now */
575 xen_update_blkif_status(be->blkif);
581 * Callback received when the frontend's state changes.
583 static void frontend_changed(struct xenbus_device *dev,
584 enum xenbus_state frontend_state)
586 struct backend_info *be = dev_get_drvdata(&dev->dev);
589 DPRINTK("%s", xenbus_strstate(frontend_state));
591 switch (frontend_state) {
592 case XenbusStateInitialising:
593 if (dev->state == XenbusStateClosed) {
594 pr_info(DRV_PFX "%s: prepare for reconnect\n",
596 xenbus_switch_state(dev, XenbusStateInitWait);
600 case XenbusStateInitialised:
601 case XenbusStateConnected:
603 * Ensure we connect even when two watches fire in
604 * close succession and we miss the intermediate value
607 if (dev->state == XenbusStateConnected)
611 * Enforce precondition before potential leak point.
612 * xen_blkif_disconnect() is idempotent.
614 xen_blkif_disconnect(be->blkif);
616 err = connect_ring(be);
619 xen_update_blkif_status(be->blkif);
622 case XenbusStateClosing:
623 xenbus_switch_state(dev, XenbusStateClosing);
626 case XenbusStateClosed:
627 xen_blkif_disconnect(be->blkif);
628 xenbus_switch_state(dev, XenbusStateClosed);
629 if (xenbus_dev_is_online(dev))
631 /* fall through if not online */
632 case XenbusStateUnknown:
633 /* implies xen_blkif_disconnect() via xen_blkbk_remove() */
634 device_unregister(&dev->dev);
638 xenbus_dev_fatal(dev, -EINVAL, "saw state %d at frontend",
645 /* ** Connection ** */
649 * Write the physical details regarding the block device to the store, and
650 * switch to Connected state.
652 static void connect(struct backend_info *be)
654 struct xenbus_transaction xbt;
656 struct xenbus_device *dev = be->dev;
658 DPRINTK("%s", dev->otherend);
660 /* Supply the information about the device the frontend needs */
662 err = xenbus_transaction_start(&xbt);
664 xenbus_dev_fatal(dev, err, "starting transaction");
668 /* If we can't advertise it is OK. */
669 xen_blkbk_flush_diskcache(xbt, be, be->blkif->vbd.flush_support);
671 xen_blkbk_discard(xbt, be);
673 xen_blkbk_barrier(xbt, be, be->blkif->vbd.flush_support);
675 err = xenbus_printf(xbt, dev->nodename, "feature-persistent", "%u", 1);
677 xenbus_dev_fatal(dev, err, "writing %s/feature-persistent",
682 err = xenbus_printf(xbt, dev->nodename, "sectors", "%llu",
683 (unsigned long long)vbd_sz(&be->blkif->vbd));
685 xenbus_dev_fatal(dev, err, "writing %s/sectors",
690 /* FIXME: use a typename instead */
691 err = xenbus_printf(xbt, dev->nodename, "info", "%u",
692 be->blkif->vbd.type |
693 (be->blkif->vbd.readonly ? VDISK_READONLY : 0));
695 xenbus_dev_fatal(dev, err, "writing %s/info",
699 err = xenbus_printf(xbt, dev->nodename, "sector-size", "%lu",
701 bdev_logical_block_size(be->blkif->vbd.bdev));
703 xenbus_dev_fatal(dev, err, "writing %s/sector-size",
708 err = xenbus_transaction_end(xbt, 0);
712 xenbus_dev_fatal(dev, err, "ending transaction");
714 err = xenbus_switch_state(dev, XenbusStateConnected);
716 xenbus_dev_fatal(dev, err, "%s: switching to Connected state",
721 xenbus_transaction_end(xbt, 1);
725 static int connect_ring(struct backend_info *be)
727 struct xenbus_device *dev = be->dev;
728 unsigned long ring_ref;
730 unsigned int pers_grants;
731 char protocol[64] = "";
734 DPRINTK("%s", dev->otherend);
736 err = xenbus_gather(XBT_NIL, dev->otherend, "ring-ref", "%lu",
737 &ring_ref, "event-channel", "%u", &evtchn, NULL);
739 xenbus_dev_fatal(dev, err,
740 "reading %s/ring-ref and event-channel",
745 be->blkif->blk_protocol = BLKIF_PROTOCOL_NATIVE;
746 err = xenbus_gather(XBT_NIL, dev->otherend, "protocol",
747 "%63s", protocol, NULL);
749 strcpy(protocol, "unspecified, assuming native");
750 else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_NATIVE))
751 be->blkif->blk_protocol = BLKIF_PROTOCOL_NATIVE;
752 else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_32))
753 be->blkif->blk_protocol = BLKIF_PROTOCOL_X86_32;
754 else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_64))
755 be->blkif->blk_protocol = BLKIF_PROTOCOL_X86_64;
757 xenbus_dev_fatal(dev, err, "unknown fe protocol %s", protocol);
760 err = xenbus_gather(XBT_NIL, dev->otherend,
761 "feature-persistent", "%u",
766 be->blkif->vbd.feature_gnt_persistent = pers_grants;
767 be->blkif->vbd.overflow_max_grants = 0;
769 pr_info(DRV_PFX "ring-ref %ld, event-channel %d, protocol %d (%s) %s\n",
770 ring_ref, evtchn, be->blkif->blk_protocol, protocol,
771 pers_grants ? "persistent grants" : "");
773 /* Map the shared frame, irq etc. */
774 err = xen_blkif_map(be->blkif, ring_ref, evtchn);
776 xenbus_dev_fatal(dev, err, "mapping ring-ref %lu port %u",
785 /* ** Driver Registration ** */
788 static const struct xenbus_device_id xen_blkbk_ids[] = {
794 static DEFINE_XENBUS_DRIVER(xen_blkbk, ,
795 .probe = xen_blkbk_probe,
796 .remove = xen_blkbk_remove,
797 .otherend_changed = frontend_changed
801 int xen_blkif_xenbus_init(void)
803 return xenbus_register_backend(&xen_blkbk_driver);