1 /*  Xenbus code for blkif backend
2     Copyright (C) 2005 Rusty Russell <rusty@rustcorp.com.au>
3     Copyright (C) 2005 XenSource Ltd
4 
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.
9 
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.
14 
15 */
16 
17 #define pr_fmt(fmt) "xen-blkback: " fmt
18 
19 #include <stdarg.h>
20 #include <linux/module.h>
21 #include <linux/kthread.h>
22 #include <xen/events.h>
23 #include <xen/grant_table.h>
24 #include "common.h"
25 
26 /* On the XenBus the max length of 'ring-ref%u'. */
27 #define RINGREF_NAME_LEN (20)
28 
29 struct backend_info {
30 	struct xenbus_device	*dev;
31 	struct xen_blkif	*blkif;
32 	struct xenbus_watch	backend_watch;
33 	unsigned		major;
34 	unsigned		minor;
35 	char			*mode;
36 };
37 
38 static struct kmem_cache *xen_blkif_cachep;
39 static void connect(struct backend_info *);
40 static int connect_ring(struct backend_info *);
41 static void backend_changed(struct xenbus_watch *, const char *,
42 			    const char *);
43 static void xen_blkif_free(struct xen_blkif *blkif);
44 static void xen_vbd_free(struct xen_vbd *vbd);
45 
46 struct xenbus_device *xen_blkbk_xenbus(struct backend_info *be)
47 {
48 	return be->dev;
49 }
50 
51 /*
52  * The last request could free the device from softirq context and
53  * xen_blkif_free() can sleep.
54  */
55 static void xen_blkif_deferred_free(struct work_struct *work)
56 {
57 	struct xen_blkif *blkif;
58 
59 	blkif = container_of(work, struct xen_blkif, free_work);
60 	xen_blkif_free(blkif);
61 }
62 
63 static int blkback_name(struct xen_blkif *blkif, char *buf)
64 {
65 	char *devpath, *devname;
66 	struct xenbus_device *dev = blkif->be->dev;
67 
68 	devpath = xenbus_read(XBT_NIL, dev->nodename, "dev", NULL);
69 	if (IS_ERR(devpath))
70 		return PTR_ERR(devpath);
71 
72 	devname = strstr(devpath, "/dev/");
73 	if (devname != NULL)
74 		devname += strlen("/dev/");
75 	else
76 		devname  = devpath;
77 
78 	snprintf(buf, TASK_COMM_LEN, "%d.%s", blkif->domid, devname);
79 	kfree(devpath);
80 
81 	return 0;
82 }
83 
84 static void xen_update_blkif_status(struct xen_blkif *blkif)
85 {
86 	int err;
87 	char name[TASK_COMM_LEN];
88 	struct xen_blkif_ring *ring;
89 	int i;
90 
91 	/* Not ready to connect? */
92 	if (!blkif->rings || !blkif->rings[0].irq || !blkif->vbd.bdev)
93 		return;
94 
95 	/* Already connected? */
96 	if (blkif->be->dev->state == XenbusStateConnected)
97 		return;
98 
99 	/* Attempt to connect: exit if we fail to. */
100 	connect(blkif->be);
101 	if (blkif->be->dev->state != XenbusStateConnected)
102 		return;
103 
104 	err = blkback_name(blkif, name);
105 	if (err) {
106 		xenbus_dev_error(blkif->be->dev, err, "get blkback dev name");
107 		return;
108 	}
109 
110 	err = filemap_write_and_wait(blkif->vbd.bdev->bd_inode->i_mapping);
111 	if (err) {
112 		xenbus_dev_error(blkif->be->dev, err, "block flush");
113 		return;
114 	}
115 	invalidate_inode_pages2(blkif->vbd.bdev->bd_inode->i_mapping);
116 
117 	for (i = 0; i < blkif->nr_rings; i++) {
118 		ring = &blkif->rings[i];
119 		ring->xenblkd = kthread_run(xen_blkif_schedule, ring, "%s-%d", name, i);
120 		if (IS_ERR(ring->xenblkd)) {
121 			err = PTR_ERR(ring->xenblkd);
122 			ring->xenblkd = NULL;
123 			xenbus_dev_fatal(blkif->be->dev, err,
124 					"start %s-%d xenblkd", name, i);
125 			goto out;
126 		}
127 	}
128 	return;
129 
130 out:
131 	while (--i >= 0) {
132 		ring = &blkif->rings[i];
133 		kthread_stop(ring->xenblkd);
134 	}
135 	return;
136 }
137 
138 static int xen_blkif_alloc_rings(struct xen_blkif *blkif)
139 {
140 	unsigned int r;
141 
142 	blkif->rings = kzalloc(blkif->nr_rings * sizeof(struct xen_blkif_ring), GFP_KERNEL);
143 	if (!blkif->rings)
144 		return -ENOMEM;
145 
146 	for (r = 0; r < blkif->nr_rings; r++) {
147 		struct xen_blkif_ring *ring = &blkif->rings[r];
148 
149 		spin_lock_init(&ring->blk_ring_lock);
150 		init_waitqueue_head(&ring->wq);
151 		INIT_LIST_HEAD(&ring->pending_free);
152 		INIT_LIST_HEAD(&ring->persistent_purge_list);
153 		INIT_WORK(&ring->persistent_purge_work, xen_blkbk_unmap_purged_grants);
154 		spin_lock_init(&ring->free_pages_lock);
155 		INIT_LIST_HEAD(&ring->free_pages);
156 
157 		spin_lock_init(&ring->pending_free_lock);
158 		init_waitqueue_head(&ring->pending_free_wq);
159 		init_waitqueue_head(&ring->shutdown_wq);
160 		ring->blkif = blkif;
161 		ring->st_print = jiffies;
162 		ring->active = true;
163 	}
164 
165 	return 0;
166 }
167 
168 static struct xen_blkif *xen_blkif_alloc(domid_t domid)
169 {
170 	struct xen_blkif *blkif;
171 
172 	BUILD_BUG_ON(MAX_INDIRECT_PAGES > BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST);
173 
174 	blkif = kmem_cache_zalloc(xen_blkif_cachep, GFP_KERNEL);
175 	if (!blkif)
176 		return ERR_PTR(-ENOMEM);
177 
178 	blkif->domid = domid;
179 	atomic_set(&blkif->refcnt, 1);
180 	init_completion(&blkif->drain_complete);
181 	INIT_WORK(&blkif->free_work, xen_blkif_deferred_free);
182 
183 	return blkif;
184 }
185 
186 static int xen_blkif_map(struct xen_blkif_ring *ring, grant_ref_t *gref,
187 			 unsigned int nr_grefs, unsigned int evtchn)
188 {
189 	int err;
190 	struct xen_blkif *blkif = ring->blkif;
191 
192 	/* Already connected through? */
193 	if (ring->irq)
194 		return 0;
195 
196 	err = xenbus_map_ring_valloc(blkif->be->dev, gref, nr_grefs,
197 				     &ring->blk_ring);
198 	if (err < 0)
199 		return err;
200 
201 	switch (blkif->blk_protocol) {
202 	case BLKIF_PROTOCOL_NATIVE:
203 	{
204 		struct blkif_sring *sring;
205 		sring = (struct blkif_sring *)ring->blk_ring;
206 		BACK_RING_INIT(&ring->blk_rings.native, sring,
207 			       XEN_PAGE_SIZE * nr_grefs);
208 		break;
209 	}
210 	case BLKIF_PROTOCOL_X86_32:
211 	{
212 		struct blkif_x86_32_sring *sring_x86_32;
213 		sring_x86_32 = (struct blkif_x86_32_sring *)ring->blk_ring;
214 		BACK_RING_INIT(&ring->blk_rings.x86_32, sring_x86_32,
215 			       XEN_PAGE_SIZE * nr_grefs);
216 		break;
217 	}
218 	case BLKIF_PROTOCOL_X86_64:
219 	{
220 		struct blkif_x86_64_sring *sring_x86_64;
221 		sring_x86_64 = (struct blkif_x86_64_sring *)ring->blk_ring;
222 		BACK_RING_INIT(&ring->blk_rings.x86_64, sring_x86_64,
223 			       XEN_PAGE_SIZE * nr_grefs);
224 		break;
225 	}
226 	default:
227 		BUG();
228 	}
229 
230 	err = bind_interdomain_evtchn_to_irqhandler(blkif->domid, evtchn,
231 						    xen_blkif_be_int, 0,
232 						    "blkif-backend", ring);
233 	if (err < 0) {
234 		xenbus_unmap_ring_vfree(blkif->be->dev, ring->blk_ring);
235 		ring->blk_rings.common.sring = NULL;
236 		return err;
237 	}
238 	ring->irq = err;
239 
240 	return 0;
241 }
242 
243 static int xen_blkif_disconnect(struct xen_blkif *blkif)
244 {
245 	struct pending_req *req, *n;
246 	unsigned int j, r;
247 
248 	for (r = 0; r < blkif->nr_rings; r++) {
249 		struct xen_blkif_ring *ring = &blkif->rings[r];
250 		unsigned int i = 0;
251 
252 		if (!ring->active)
253 			continue;
254 
255 		if (ring->xenblkd) {
256 			kthread_stop(ring->xenblkd);
257 			wake_up(&ring->shutdown_wq);
258 		}
259 
260 		/* The above kthread_stop() guarantees that at this point we
261 		 * don't have any discard_io or other_io requests. So, checking
262 		 * for inflight IO is enough.
263 		 */
264 		if (atomic_read(&ring->inflight) > 0)
265 			return -EBUSY;
266 
267 		if (ring->irq) {
268 			unbind_from_irqhandler(ring->irq, ring);
269 			ring->irq = 0;
270 		}
271 
272 		if (ring->blk_rings.common.sring) {
273 			xenbus_unmap_ring_vfree(blkif->be->dev, ring->blk_ring);
274 			ring->blk_rings.common.sring = NULL;
275 		}
276 
277 		/* Remove all persistent grants and the cache of ballooned pages. */
278 		xen_blkbk_free_caches(ring);
279 
280 		/* Check that there is no request in use */
281 		list_for_each_entry_safe(req, n, &ring->pending_free, free_list) {
282 			list_del(&req->free_list);
283 
284 			for (j = 0; j < MAX_INDIRECT_SEGMENTS; j++)
285 				kfree(req->segments[j]);
286 
287 			for (j = 0; j < MAX_INDIRECT_PAGES; j++)
288 				kfree(req->indirect_pages[j]);
289 
290 			kfree(req);
291 			i++;
292 		}
293 
294 		BUG_ON(atomic_read(&ring->persistent_gnt_in_use) != 0);
295 		BUG_ON(!list_empty(&ring->persistent_purge_list));
296 		BUG_ON(!RB_EMPTY_ROOT(&ring->persistent_gnts));
297 		BUG_ON(!list_empty(&ring->free_pages));
298 		BUG_ON(ring->free_pages_num != 0);
299 		BUG_ON(ring->persistent_gnt_c != 0);
300 		WARN_ON(i != (XEN_BLKIF_REQS_PER_PAGE * blkif->nr_ring_pages));
301 		ring->active = false;
302 	}
303 	blkif->nr_ring_pages = 0;
304 	/*
305 	 * blkif->rings was allocated in connect_ring, so we should free it in
306 	 * here.
307 	 */
308 	kfree(blkif->rings);
309 	blkif->rings = NULL;
310 	blkif->nr_rings = 0;
311 
312 	return 0;
313 }
314 
315 static void xen_blkif_free(struct xen_blkif *blkif)
316 {
317 	WARN_ON(xen_blkif_disconnect(blkif));
318 	xen_vbd_free(&blkif->vbd);
319 	kfree(blkif->be->mode);
320 	kfree(blkif->be);
321 
322 	/* Make sure everything is drained before shutting down */
323 	kmem_cache_free(xen_blkif_cachep, blkif);
324 }
325 
326 int __init xen_blkif_interface_init(void)
327 {
328 	xen_blkif_cachep = kmem_cache_create("blkif_cache",
329 					     sizeof(struct xen_blkif),
330 					     0, 0, NULL);
331 	if (!xen_blkif_cachep)
332 		return -ENOMEM;
333 
334 	return 0;
335 }
336 
337 /*
338  *  sysfs interface for VBD I/O requests
339  */
340 
341 #define VBD_SHOW_ALLRING(name, format)					\
342 	static ssize_t show_##name(struct device *_dev,			\
343 				   struct device_attribute *attr,	\
344 				   char *buf)				\
345 	{								\
346 		struct xenbus_device *dev = to_xenbus_device(_dev);	\
347 		struct backend_info *be = dev_get_drvdata(&dev->dev);	\
348 		struct xen_blkif *blkif = be->blkif;			\
349 		unsigned int i;						\
350 		unsigned long long result = 0;				\
351 									\
352 		if (!blkif->rings)				\
353 			goto out;					\
354 									\
355 		for (i = 0; i < blkif->nr_rings; i++) {		\
356 			struct xen_blkif_ring *ring = &blkif->rings[i];	\
357 									\
358 			result += ring->st_##name;			\
359 		}							\
360 									\
361 out:									\
362 		return sprintf(buf, format, result);			\
363 	}								\
364 	static DEVICE_ATTR(name, S_IRUGO, show_##name, NULL)
365 
366 VBD_SHOW_ALLRING(oo_req,  "%llu\n");
367 VBD_SHOW_ALLRING(rd_req,  "%llu\n");
368 VBD_SHOW_ALLRING(wr_req,  "%llu\n");
369 VBD_SHOW_ALLRING(f_req,  "%llu\n");
370 VBD_SHOW_ALLRING(ds_req,  "%llu\n");
371 VBD_SHOW_ALLRING(rd_sect, "%llu\n");
372 VBD_SHOW_ALLRING(wr_sect, "%llu\n");
373 
374 static struct attribute *xen_vbdstat_attrs[] = {
375 	&dev_attr_oo_req.attr,
376 	&dev_attr_rd_req.attr,
377 	&dev_attr_wr_req.attr,
378 	&dev_attr_f_req.attr,
379 	&dev_attr_ds_req.attr,
380 	&dev_attr_rd_sect.attr,
381 	&dev_attr_wr_sect.attr,
382 	NULL
383 };
384 
385 static const struct attribute_group xen_vbdstat_group = {
386 	.name = "statistics",
387 	.attrs = xen_vbdstat_attrs,
388 };
389 
390 #define VBD_SHOW(name, format, args...)					\
391 	static ssize_t show_##name(struct device *_dev,			\
392 				   struct device_attribute *attr,	\
393 				   char *buf)				\
394 	{								\
395 		struct xenbus_device *dev = to_xenbus_device(_dev);	\
396 		struct backend_info *be = dev_get_drvdata(&dev->dev);	\
397 									\
398 		return sprintf(buf, format, ##args);			\
399 	}								\
400 	static DEVICE_ATTR(name, S_IRUGO, show_##name, NULL)
401 
402 VBD_SHOW(physical_device, "%x:%x\n", be->major, be->minor);
403 VBD_SHOW(mode, "%s\n", be->mode);
404 
405 static int xenvbd_sysfs_addif(struct xenbus_device *dev)
406 {
407 	int error;
408 
409 	error = device_create_file(&dev->dev, &dev_attr_physical_device);
410 	if (error)
411 		goto fail1;
412 
413 	error = device_create_file(&dev->dev, &dev_attr_mode);
414 	if (error)
415 		goto fail2;
416 
417 	error = sysfs_create_group(&dev->dev.kobj, &xen_vbdstat_group);
418 	if (error)
419 		goto fail3;
420 
421 	return 0;
422 
423 fail3:	sysfs_remove_group(&dev->dev.kobj, &xen_vbdstat_group);
424 fail2:	device_remove_file(&dev->dev, &dev_attr_mode);
425 fail1:	device_remove_file(&dev->dev, &dev_attr_physical_device);
426 	return error;
427 }
428 
429 static void xenvbd_sysfs_delif(struct xenbus_device *dev)
430 {
431 	sysfs_remove_group(&dev->dev.kobj, &xen_vbdstat_group);
432 	device_remove_file(&dev->dev, &dev_attr_mode);
433 	device_remove_file(&dev->dev, &dev_attr_physical_device);
434 }
435 
436 
437 static void xen_vbd_free(struct xen_vbd *vbd)
438 {
439 	if (vbd->bdev)
440 		blkdev_put(vbd->bdev, vbd->readonly ? FMODE_READ : FMODE_WRITE);
441 	vbd->bdev = NULL;
442 }
443 
444 static int xen_vbd_create(struct xen_blkif *blkif, blkif_vdev_t handle,
445 			  unsigned major, unsigned minor, int readonly,
446 			  int cdrom)
447 {
448 	struct xen_vbd *vbd;
449 	struct block_device *bdev;
450 	struct request_queue *q;
451 
452 	vbd = &blkif->vbd;
453 	vbd->handle   = handle;
454 	vbd->readonly = readonly;
455 	vbd->type     = 0;
456 
457 	vbd->pdevice  = MKDEV(major, minor);
458 
459 	bdev = blkdev_get_by_dev(vbd->pdevice, vbd->readonly ?
460 				 FMODE_READ : FMODE_WRITE, NULL);
461 
462 	if (IS_ERR(bdev)) {
463 		pr_warn("xen_vbd_create: device %08x could not be opened\n",
464 			vbd->pdevice);
465 		return -ENOENT;
466 	}
467 
468 	vbd->bdev = bdev;
469 	if (vbd->bdev->bd_disk == NULL) {
470 		pr_warn("xen_vbd_create: device %08x doesn't exist\n",
471 			vbd->pdevice);
472 		xen_vbd_free(vbd);
473 		return -ENOENT;
474 	}
475 	vbd->size = vbd_sz(vbd);
476 
477 	if (vbd->bdev->bd_disk->flags & GENHD_FL_CD || cdrom)
478 		vbd->type |= VDISK_CDROM;
479 	if (vbd->bdev->bd_disk->flags & GENHD_FL_REMOVABLE)
480 		vbd->type |= VDISK_REMOVABLE;
481 
482 	q = bdev_get_queue(bdev);
483 	if (q && test_bit(QUEUE_FLAG_WC, &q->queue_flags))
484 		vbd->flush_support = true;
485 
486 	if (q && blk_queue_secure_erase(q))
487 		vbd->discard_secure = true;
488 
489 	pr_debug("Successful creation of handle=%04x (dom=%u)\n",
490 		handle, blkif->domid);
491 	return 0;
492 }
493 static int xen_blkbk_remove(struct xenbus_device *dev)
494 {
495 	struct backend_info *be = dev_get_drvdata(&dev->dev);
496 
497 	pr_debug("%s %p %d\n", __func__, dev, dev->otherend_id);
498 
499 	if (be->major || be->minor)
500 		xenvbd_sysfs_delif(dev);
501 
502 	if (be->backend_watch.node) {
503 		unregister_xenbus_watch(&be->backend_watch);
504 		kfree(be->backend_watch.node);
505 		be->backend_watch.node = NULL;
506 	}
507 
508 	dev_set_drvdata(&dev->dev, NULL);
509 
510 	if (be->blkif) {
511 		xen_blkif_disconnect(be->blkif);
512 
513 		/* Put the reference we set in xen_blkif_alloc(). */
514 		xen_blkif_put(be->blkif);
515 	}
516 
517 	return 0;
518 }
519 
520 int xen_blkbk_flush_diskcache(struct xenbus_transaction xbt,
521 			      struct backend_info *be, int state)
522 {
523 	struct xenbus_device *dev = be->dev;
524 	int err;
525 
526 	err = xenbus_printf(xbt, dev->nodename, "feature-flush-cache",
527 			    "%d", state);
528 	if (err)
529 		dev_warn(&dev->dev, "writing feature-flush-cache (%d)", err);
530 
531 	return err;
532 }
533 
534 static void xen_blkbk_discard(struct xenbus_transaction xbt, struct backend_info *be)
535 {
536 	struct xenbus_device *dev = be->dev;
537 	struct xen_blkif *blkif = be->blkif;
538 	int err;
539 	int state = 0;
540 	struct block_device *bdev = be->blkif->vbd.bdev;
541 	struct request_queue *q = bdev_get_queue(bdev);
542 
543 	if (!xenbus_read_unsigned(dev->nodename, "discard-enable", 1))
544 		return;
545 
546 	if (blk_queue_discard(q)) {
547 		err = xenbus_printf(xbt, dev->nodename,
548 			"discard-granularity", "%u",
549 			q->limits.discard_granularity);
550 		if (err) {
551 			dev_warn(&dev->dev, "writing discard-granularity (%d)", err);
552 			return;
553 		}
554 		err = xenbus_printf(xbt, dev->nodename,
555 			"discard-alignment", "%u",
556 			q->limits.discard_alignment);
557 		if (err) {
558 			dev_warn(&dev->dev, "writing discard-alignment (%d)", err);
559 			return;
560 		}
561 		state = 1;
562 		/* Optional. */
563 		err = xenbus_printf(xbt, dev->nodename,
564 				    "discard-secure", "%d",
565 				    blkif->vbd.discard_secure);
566 		if (err) {
567 			dev_warn(&dev->dev, "writing discard-secure (%d)", err);
568 			return;
569 		}
570 	}
571 	err = xenbus_printf(xbt, dev->nodename, "feature-discard",
572 			    "%d", state);
573 	if (err)
574 		dev_warn(&dev->dev, "writing feature-discard (%d)", err);
575 }
576 int xen_blkbk_barrier(struct xenbus_transaction xbt,
577 		      struct backend_info *be, int state)
578 {
579 	struct xenbus_device *dev = be->dev;
580 	int err;
581 
582 	err = xenbus_printf(xbt, dev->nodename, "feature-barrier",
583 			    "%d", state);
584 	if (err)
585 		dev_warn(&dev->dev, "writing feature-barrier (%d)", err);
586 
587 	return err;
588 }
589 
590 /*
591  * Entry point to this code when a new device is created.  Allocate the basic
592  * structures, and watch the store waiting for the hotplug scripts to tell us
593  * the device's physical major and minor numbers.  Switch to InitWait.
594  */
595 static int xen_blkbk_probe(struct xenbus_device *dev,
596 			   const struct xenbus_device_id *id)
597 {
598 	int err;
599 	struct backend_info *be = kzalloc(sizeof(struct backend_info),
600 					  GFP_KERNEL);
601 
602 	/* match the pr_debug in xen_blkbk_remove */
603 	pr_debug("%s %p %d\n", __func__, dev, dev->otherend_id);
604 
605 	if (!be) {
606 		xenbus_dev_fatal(dev, -ENOMEM,
607 				 "allocating backend structure");
608 		return -ENOMEM;
609 	}
610 	be->dev = dev;
611 	dev_set_drvdata(&dev->dev, be);
612 
613 	be->blkif = xen_blkif_alloc(dev->otherend_id);
614 	if (IS_ERR(be->blkif)) {
615 		err = PTR_ERR(be->blkif);
616 		be->blkif = NULL;
617 		xenbus_dev_fatal(dev, err, "creating block interface");
618 		goto fail;
619 	}
620 
621 	err = xenbus_printf(XBT_NIL, dev->nodename,
622 			    "feature-max-indirect-segments", "%u",
623 			    MAX_INDIRECT_SEGMENTS);
624 	if (err)
625 		dev_warn(&dev->dev,
626 			 "writing %s/feature-max-indirect-segments (%d)",
627 			 dev->nodename, err);
628 
629 	/* Multi-queue: advertise how many queues are supported by us.*/
630 	err = xenbus_printf(XBT_NIL, dev->nodename,
631 			    "multi-queue-max-queues", "%u", xenblk_max_queues);
632 	if (err)
633 		pr_warn("Error writing multi-queue-max-queues\n");
634 
635 	/* setup back pointer */
636 	be->blkif->be = be;
637 
638 	err = xenbus_watch_pathfmt(dev, &be->backend_watch, backend_changed,
639 				   "%s/%s", dev->nodename, "physical-device");
640 	if (err)
641 		goto fail;
642 
643 	err = xenbus_printf(XBT_NIL, dev->nodename, "max-ring-page-order", "%u",
644 			    xen_blkif_max_ring_order);
645 	if (err)
646 		pr_warn("%s write out 'max-ring-page-order' failed\n", __func__);
647 
648 	err = xenbus_switch_state(dev, XenbusStateInitWait);
649 	if (err)
650 		goto fail;
651 
652 	return 0;
653 
654 fail:
655 	pr_warn("%s failed\n", __func__);
656 	xen_blkbk_remove(dev);
657 	return err;
658 }
659 
660 
661 /*
662  * Callback received when the hotplug scripts have placed the physical-device
663  * node.  Read it and the mode node, and create a vbd.  If the frontend is
664  * ready, connect.
665  */
666 static void backend_changed(struct xenbus_watch *watch,
667 			    const char *path, const char *token)
668 {
669 	int err;
670 	unsigned major;
671 	unsigned minor;
672 	struct backend_info *be
673 		= container_of(watch, struct backend_info, backend_watch);
674 	struct xenbus_device *dev = be->dev;
675 	int cdrom = 0;
676 	unsigned long handle;
677 	char *device_type;
678 
679 	pr_debug("%s %p %d\n", __func__, dev, dev->otherend_id);
680 
681 	err = xenbus_scanf(XBT_NIL, dev->nodename, "physical-device", "%x:%x",
682 			   &major, &minor);
683 	if (XENBUS_EXIST_ERR(err)) {
684 		/*
685 		 * Since this watch will fire once immediately after it is
686 		 * registered, we expect this.  Ignore it, and wait for the
687 		 * hotplug scripts.
688 		 */
689 		return;
690 	}
691 	if (err != 2) {
692 		xenbus_dev_fatal(dev, err, "reading physical-device");
693 		return;
694 	}
695 
696 	if (be->major | be->minor) {
697 		if (be->major != major || be->minor != minor)
698 			pr_warn("changing physical device (from %x:%x to %x:%x) not supported.\n",
699 				be->major, be->minor, major, minor);
700 		return;
701 	}
702 
703 	be->mode = xenbus_read(XBT_NIL, dev->nodename, "mode", NULL);
704 	if (IS_ERR(be->mode)) {
705 		err = PTR_ERR(be->mode);
706 		be->mode = NULL;
707 		xenbus_dev_fatal(dev, err, "reading mode");
708 		return;
709 	}
710 
711 	device_type = xenbus_read(XBT_NIL, dev->otherend, "device-type", NULL);
712 	if (!IS_ERR(device_type)) {
713 		cdrom = strcmp(device_type, "cdrom") == 0;
714 		kfree(device_type);
715 	}
716 
717 	/* Front end dir is a number, which is used as the handle. */
718 	err = kstrtoul(strrchr(dev->otherend, '/') + 1, 0, &handle);
719 	if (err) {
720 		kfree(be->mode);
721 		be->mode = NULL;
722 		return;
723 	}
724 
725 	be->major = major;
726 	be->minor = minor;
727 
728 	err = xen_vbd_create(be->blkif, handle, major, minor,
729 			     !strchr(be->mode, 'w'), cdrom);
730 
731 	if (err)
732 		xenbus_dev_fatal(dev, err, "creating vbd structure");
733 	else {
734 		err = xenvbd_sysfs_addif(dev);
735 		if (err) {
736 			xen_vbd_free(&be->blkif->vbd);
737 			xenbus_dev_fatal(dev, err, "creating sysfs entries");
738 		}
739 	}
740 
741 	if (err) {
742 		kfree(be->mode);
743 		be->mode = NULL;
744 		be->major = 0;
745 		be->minor = 0;
746 	} else {
747 		/* We're potentially connected now */
748 		xen_update_blkif_status(be->blkif);
749 	}
750 }
751 
752 
753 /*
754  * Callback received when the frontend's state changes.
755  */
756 static void frontend_changed(struct xenbus_device *dev,
757 			     enum xenbus_state frontend_state)
758 {
759 	struct backend_info *be = dev_get_drvdata(&dev->dev);
760 	int err;
761 
762 	pr_debug("%s %p %s\n", __func__, dev, xenbus_strstate(frontend_state));
763 
764 	switch (frontend_state) {
765 	case XenbusStateInitialising:
766 		if (dev->state == XenbusStateClosed) {
767 			pr_info("%s: prepare for reconnect\n", dev->nodename);
768 			xenbus_switch_state(dev, XenbusStateInitWait);
769 		}
770 		break;
771 
772 	case XenbusStateInitialised:
773 	case XenbusStateConnected:
774 		/*
775 		 * Ensure we connect even when two watches fire in
776 		 * close succession and we miss the intermediate value
777 		 * of frontend_state.
778 		 */
779 		if (dev->state == XenbusStateConnected)
780 			break;
781 
782 		/*
783 		 * Enforce precondition before potential leak point.
784 		 * xen_blkif_disconnect() is idempotent.
785 		 */
786 		err = xen_blkif_disconnect(be->blkif);
787 		if (err) {
788 			xenbus_dev_fatal(dev, err, "pending I/O");
789 			break;
790 		}
791 
792 		err = connect_ring(be);
793 		if (err) {
794 			/*
795 			 * Clean up so that memory resources can be used by
796 			 * other devices. connect_ring reported already error.
797 			 */
798 			xen_blkif_disconnect(be->blkif);
799 			break;
800 		}
801 		xen_update_blkif_status(be->blkif);
802 		break;
803 
804 	case XenbusStateClosing:
805 		xenbus_switch_state(dev, XenbusStateClosing);
806 		break;
807 
808 	case XenbusStateClosed:
809 		xen_blkif_disconnect(be->blkif);
810 		xenbus_switch_state(dev, XenbusStateClosed);
811 		if (xenbus_dev_is_online(dev))
812 			break;
813 		/* fall through if not online */
814 	case XenbusStateUnknown:
815 		/* implies xen_blkif_disconnect() via xen_blkbk_remove() */
816 		device_unregister(&dev->dev);
817 		break;
818 
819 	default:
820 		xenbus_dev_fatal(dev, -EINVAL, "saw state %d at frontend",
821 				 frontend_state);
822 		break;
823 	}
824 }
825 
826 
827 /* ** Connection ** */
828 
829 
830 /*
831  * Write the physical details regarding the block device to the store, and
832  * switch to Connected state.
833  */
834 static void connect(struct backend_info *be)
835 {
836 	struct xenbus_transaction xbt;
837 	int err;
838 	struct xenbus_device *dev = be->dev;
839 
840 	pr_debug("%s %s\n", __func__, dev->otherend);
841 
842 	/* Supply the information about the device the frontend needs */
843 again:
844 	err = xenbus_transaction_start(&xbt);
845 	if (err) {
846 		xenbus_dev_fatal(dev, err, "starting transaction");
847 		return;
848 	}
849 
850 	/* If we can't advertise it is OK. */
851 	xen_blkbk_flush_diskcache(xbt, be, be->blkif->vbd.flush_support);
852 
853 	xen_blkbk_discard(xbt, be);
854 
855 	xen_blkbk_barrier(xbt, be, be->blkif->vbd.flush_support);
856 
857 	err = xenbus_printf(xbt, dev->nodename, "feature-persistent", "%u", 1);
858 	if (err) {
859 		xenbus_dev_fatal(dev, err, "writing %s/feature-persistent",
860 				 dev->nodename);
861 		goto abort;
862 	}
863 
864 	err = xenbus_printf(xbt, dev->nodename, "sectors", "%llu",
865 			    (unsigned long long)vbd_sz(&be->blkif->vbd));
866 	if (err) {
867 		xenbus_dev_fatal(dev, err, "writing %s/sectors",
868 				 dev->nodename);
869 		goto abort;
870 	}
871 
872 	/* FIXME: use a typename instead */
873 	err = xenbus_printf(xbt, dev->nodename, "info", "%u",
874 			    be->blkif->vbd.type |
875 			    (be->blkif->vbd.readonly ? VDISK_READONLY : 0));
876 	if (err) {
877 		xenbus_dev_fatal(dev, err, "writing %s/info",
878 				 dev->nodename);
879 		goto abort;
880 	}
881 	err = xenbus_printf(xbt, dev->nodename, "sector-size", "%lu",
882 			    (unsigned long)
883 			    bdev_logical_block_size(be->blkif->vbd.bdev));
884 	if (err) {
885 		xenbus_dev_fatal(dev, err, "writing %s/sector-size",
886 				 dev->nodename);
887 		goto abort;
888 	}
889 	err = xenbus_printf(xbt, dev->nodename, "physical-sector-size", "%u",
890 			    bdev_physical_block_size(be->blkif->vbd.bdev));
891 	if (err)
892 		xenbus_dev_error(dev, err, "writing %s/physical-sector-size",
893 				 dev->nodename);
894 
895 	err = xenbus_transaction_end(xbt, 0);
896 	if (err == -EAGAIN)
897 		goto again;
898 	if (err)
899 		xenbus_dev_fatal(dev, err, "ending transaction");
900 
901 	err = xenbus_switch_state(dev, XenbusStateConnected);
902 	if (err)
903 		xenbus_dev_fatal(dev, err, "%s: switching to Connected state",
904 				 dev->nodename);
905 
906 	return;
907  abort:
908 	xenbus_transaction_end(xbt, 1);
909 }
910 
911 /*
912  * Each ring may have multi pages, depends on "ring-page-order".
913  */
914 static int read_per_ring_refs(struct xen_blkif_ring *ring, const char *dir)
915 {
916 	unsigned int ring_ref[XENBUS_MAX_RING_GRANTS];
917 	struct pending_req *req, *n;
918 	int err, i, j;
919 	struct xen_blkif *blkif = ring->blkif;
920 	struct xenbus_device *dev = blkif->be->dev;
921 	unsigned int ring_page_order, nr_grefs, evtchn;
922 
923 	err = xenbus_scanf(XBT_NIL, dir, "event-channel", "%u",
924 			  &evtchn);
925 	if (err != 1) {
926 		err = -EINVAL;
927 		xenbus_dev_fatal(dev, err, "reading %s/event-channel", dir);
928 		return err;
929 	}
930 
931 	err = xenbus_scanf(XBT_NIL, dev->otherend, "ring-page-order", "%u",
932 			  &ring_page_order);
933 	if (err != 1) {
934 		err = xenbus_scanf(XBT_NIL, dir, "ring-ref", "%u", &ring_ref[0]);
935 		if (err != 1) {
936 			err = -EINVAL;
937 			xenbus_dev_fatal(dev, err, "reading %s/ring-ref", dir);
938 			return err;
939 		}
940 		nr_grefs = 1;
941 	} else {
942 		unsigned int i;
943 
944 		if (ring_page_order > xen_blkif_max_ring_order) {
945 			err = -EINVAL;
946 			xenbus_dev_fatal(dev, err, "%s/request %d ring page order exceed max:%d",
947 					 dir, ring_page_order,
948 					 xen_blkif_max_ring_order);
949 			return err;
950 		}
951 
952 		nr_grefs = 1 << ring_page_order;
953 		for (i = 0; i < nr_grefs; i++) {
954 			char ring_ref_name[RINGREF_NAME_LEN];
955 
956 			snprintf(ring_ref_name, RINGREF_NAME_LEN, "ring-ref%u", i);
957 			err = xenbus_scanf(XBT_NIL, dir, ring_ref_name,
958 					   "%u", &ring_ref[i]);
959 			if (err != 1) {
960 				err = -EINVAL;
961 				xenbus_dev_fatal(dev, err, "reading %s/%s",
962 						 dir, ring_ref_name);
963 				return err;
964 			}
965 		}
966 	}
967 	blkif->nr_ring_pages = nr_grefs;
968 
969 	for (i = 0; i < nr_grefs * XEN_BLKIF_REQS_PER_PAGE; i++) {
970 		req = kzalloc(sizeof(*req), GFP_KERNEL);
971 		if (!req)
972 			goto fail;
973 		list_add_tail(&req->free_list, &ring->pending_free);
974 		for (j = 0; j < MAX_INDIRECT_SEGMENTS; j++) {
975 			req->segments[j] = kzalloc(sizeof(*req->segments[0]), GFP_KERNEL);
976 			if (!req->segments[j])
977 				goto fail;
978 		}
979 		for (j = 0; j < MAX_INDIRECT_PAGES; j++) {
980 			req->indirect_pages[j] = kzalloc(sizeof(*req->indirect_pages[0]),
981 							 GFP_KERNEL);
982 			if (!req->indirect_pages[j])
983 				goto fail;
984 		}
985 	}
986 
987 	/* Map the shared frame, irq etc. */
988 	err = xen_blkif_map(ring, ring_ref, nr_grefs, evtchn);
989 	if (err) {
990 		xenbus_dev_fatal(dev, err, "mapping ring-ref port %u", evtchn);
991 		return err;
992 	}
993 
994 	return 0;
995 
996 fail:
997 	list_for_each_entry_safe(req, n, &ring->pending_free, free_list) {
998 		list_del(&req->free_list);
999 		for (j = 0; j < MAX_INDIRECT_SEGMENTS; j++) {
1000 			if (!req->segments[j])
1001 				break;
1002 			kfree(req->segments[j]);
1003 		}
1004 		for (j = 0; j < MAX_INDIRECT_PAGES; j++) {
1005 			if (!req->indirect_pages[j])
1006 				break;
1007 			kfree(req->indirect_pages[j]);
1008 		}
1009 		kfree(req);
1010 	}
1011 	return -ENOMEM;
1012 
1013 }
1014 
1015 static int connect_ring(struct backend_info *be)
1016 {
1017 	struct xenbus_device *dev = be->dev;
1018 	unsigned int pers_grants;
1019 	char protocol[64] = "";
1020 	int err, i;
1021 	char *xspath;
1022 	size_t xspathsize;
1023 	const size_t xenstore_path_ext_size = 11; /* sufficient for "/queue-NNN" */
1024 	unsigned int requested_num_queues = 0;
1025 
1026 	pr_debug("%s %s\n", __func__, dev->otherend);
1027 
1028 	be->blkif->blk_protocol = BLKIF_PROTOCOL_DEFAULT;
1029 	err = xenbus_scanf(XBT_NIL, dev->otherend, "protocol",
1030 			   "%63s", protocol);
1031 	if (err <= 0)
1032 		strcpy(protocol, "unspecified, assuming default");
1033 	else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_NATIVE))
1034 		be->blkif->blk_protocol = BLKIF_PROTOCOL_NATIVE;
1035 	else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_32))
1036 		be->blkif->blk_protocol = BLKIF_PROTOCOL_X86_32;
1037 	else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_64))
1038 		be->blkif->blk_protocol = BLKIF_PROTOCOL_X86_64;
1039 	else {
1040 		xenbus_dev_fatal(dev, err, "unknown fe protocol %s", protocol);
1041 		return -ENOSYS;
1042 	}
1043 	pers_grants = xenbus_read_unsigned(dev->otherend, "feature-persistent",
1044 					   0);
1045 	be->blkif->vbd.feature_gnt_persistent = pers_grants;
1046 	be->blkif->vbd.overflow_max_grants = 0;
1047 
1048 	/*
1049 	 * Read the number of hardware queues from frontend.
1050 	 */
1051 	requested_num_queues = xenbus_read_unsigned(dev->otherend,
1052 						    "multi-queue-num-queues",
1053 						    1);
1054 	if (requested_num_queues > xenblk_max_queues
1055 	    || requested_num_queues == 0) {
1056 		/* Buggy or malicious guest. */
1057 		xenbus_dev_fatal(dev, err,
1058 				"guest requested %u queues, exceeding the maximum of %u.",
1059 				requested_num_queues, xenblk_max_queues);
1060 		return -ENOSYS;
1061 	}
1062 	be->blkif->nr_rings = requested_num_queues;
1063 	if (xen_blkif_alloc_rings(be->blkif))
1064 		return -ENOMEM;
1065 
1066 	pr_info("%s: using %d queues, protocol %d (%s) %s\n", dev->nodename,
1067 		 be->blkif->nr_rings, be->blkif->blk_protocol, protocol,
1068 		 pers_grants ? "persistent grants" : "");
1069 
1070 	if (be->blkif->nr_rings == 1)
1071 		return read_per_ring_refs(&be->blkif->rings[0], dev->otherend);
1072 	else {
1073 		xspathsize = strlen(dev->otherend) + xenstore_path_ext_size;
1074 		xspath = kmalloc(xspathsize, GFP_KERNEL);
1075 		if (!xspath) {
1076 			xenbus_dev_fatal(dev, -ENOMEM, "reading ring references");
1077 			return -ENOMEM;
1078 		}
1079 
1080 		for (i = 0; i < be->blkif->nr_rings; i++) {
1081 			memset(xspath, 0, xspathsize);
1082 			snprintf(xspath, xspathsize, "%s/queue-%u", dev->otherend, i);
1083 			err = read_per_ring_refs(&be->blkif->rings[i], xspath);
1084 			if (err) {
1085 				kfree(xspath);
1086 				return err;
1087 			}
1088 		}
1089 		kfree(xspath);
1090 	}
1091 	return 0;
1092 }
1093 
1094 static const struct xenbus_device_id xen_blkbk_ids[] = {
1095 	{ "vbd" },
1096 	{ "" }
1097 };
1098 
1099 static struct xenbus_driver xen_blkbk_driver = {
1100 	.ids  = xen_blkbk_ids,
1101 	.probe = xen_blkbk_probe,
1102 	.remove = xen_blkbk_remove,
1103 	.otherend_changed = frontend_changed
1104 };
1105 
1106 int xen_blkif_xenbus_init(void)
1107 {
1108 	return xenbus_register_backend(&xen_blkbk_driver);
1109 }
1110