xref: /openbmc/linux/drivers/block/xen-blkfront.c (revision b6dcefde)
1 /*
2  * blkfront.c
3  *
4  * XenLinux virtual block device driver.
5  *
6  * Copyright (c) 2003-2004, Keir Fraser & Steve Hand
7  * Modifications by Mark A. Williamson are (c) Intel Research Cambridge
8  * Copyright (c) 2004, Christian Limpach
9  * Copyright (c) 2004, Andrew Warfield
10  * Copyright (c) 2005, Christopher Clark
11  * Copyright (c) 2005, XenSource Ltd
12  *
13  * This program is free software; you can redistribute it and/or
14  * modify it under the terms of the GNU General Public License version 2
15  * as published by the Free Software Foundation; or, when distributed
16  * separately from the Linux kernel or incorporated into other
17  * software packages, subject to the following license:
18  *
19  * Permission is hereby granted, free of charge, to any person obtaining a copy
20  * of this source file (the "Software"), to deal in the Software without
21  * restriction, including without limitation the rights to use, copy, modify,
22  * merge, publish, distribute, sublicense, and/or sell copies of the Software,
23  * and to permit persons to whom the Software is furnished to do so, subject to
24  * the following conditions:
25  *
26  * The above copyright notice and this permission notice shall be included in
27  * all copies or substantial portions of the Software.
28  *
29  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
30  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
31  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
32  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
33  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
34  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
35  * IN THE SOFTWARE.
36  */
37 
38 #include <linux/interrupt.h>
39 #include <linux/blkdev.h>
40 #include <linux/hdreg.h>
41 #include <linux/cdrom.h>
42 #include <linux/module.h>
43 #include <linux/scatterlist.h>
44 
45 #include <xen/xen.h>
46 #include <xen/xenbus.h>
47 #include <xen/grant_table.h>
48 #include <xen/events.h>
49 #include <xen/page.h>
50 
51 #include <xen/interface/grant_table.h>
52 #include <xen/interface/io/blkif.h>
53 #include <xen/interface/io/protocols.h>
54 
55 #include <asm/xen/hypervisor.h>
56 
57 enum blkif_state {
58 	BLKIF_STATE_DISCONNECTED,
59 	BLKIF_STATE_CONNECTED,
60 	BLKIF_STATE_SUSPENDED,
61 };
62 
63 struct blk_shadow {
64 	struct blkif_request req;
65 	unsigned long request;
66 	unsigned long frame[BLKIF_MAX_SEGMENTS_PER_REQUEST];
67 };
68 
69 static const struct block_device_operations xlvbd_block_fops;
70 
71 #define BLK_RING_SIZE __RING_SIZE((struct blkif_sring *)0, PAGE_SIZE)
72 
73 /*
74  * We have one of these per vbd, whether ide, scsi or 'other'.  They
75  * hang in private_data off the gendisk structure. We may end up
76  * putting all kinds of interesting stuff here :-)
77  */
78 struct blkfront_info
79 {
80 	struct xenbus_device *xbdev;
81 	struct gendisk *gd;
82 	int vdevice;
83 	blkif_vdev_t handle;
84 	enum blkif_state connected;
85 	int ring_ref;
86 	struct blkif_front_ring ring;
87 	struct scatterlist sg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
88 	unsigned int evtchn, irq;
89 	struct request_queue *rq;
90 	struct work_struct work;
91 	struct gnttab_free_callback callback;
92 	struct blk_shadow shadow[BLK_RING_SIZE];
93 	unsigned long shadow_free;
94 	int feature_barrier;
95 	int is_ready;
96 
97 	/**
98 	 * The number of people holding this device open.  We won't allow a
99 	 * hot-unplug unless this is 0.
100 	 */
101 	int users;
102 };
103 
104 static DEFINE_SPINLOCK(blkif_io_lock);
105 
106 #define MAXIMUM_OUTSTANDING_BLOCK_REQS \
107 	(BLKIF_MAX_SEGMENTS_PER_REQUEST * BLK_RING_SIZE)
108 #define GRANT_INVALID_REF	0
109 
110 #define PARTS_PER_DISK		16
111 #define PARTS_PER_EXT_DISK      256
112 
113 #define BLKIF_MAJOR(dev) ((dev)>>8)
114 #define BLKIF_MINOR(dev) ((dev) & 0xff)
115 
116 #define EXT_SHIFT 28
117 #define EXTENDED (1<<EXT_SHIFT)
118 #define VDEV_IS_EXTENDED(dev) ((dev)&(EXTENDED))
119 #define BLKIF_MINOR_EXT(dev) ((dev)&(~EXTENDED))
120 
121 #define DEV_NAME	"xvd"	/* name in /dev */
122 
123 static int get_id_from_freelist(struct blkfront_info *info)
124 {
125 	unsigned long free = info->shadow_free;
126 	BUG_ON(free >= BLK_RING_SIZE);
127 	info->shadow_free = info->shadow[free].req.id;
128 	info->shadow[free].req.id = 0x0fffffee; /* debug */
129 	return free;
130 }
131 
132 static void add_id_to_freelist(struct blkfront_info *info,
133 			       unsigned long id)
134 {
135 	info->shadow[id].req.id  = info->shadow_free;
136 	info->shadow[id].request = 0;
137 	info->shadow_free = id;
138 }
139 
140 static void blkif_restart_queue_callback(void *arg)
141 {
142 	struct blkfront_info *info = (struct blkfront_info *)arg;
143 	schedule_work(&info->work);
144 }
145 
146 static int blkif_getgeo(struct block_device *bd, struct hd_geometry *hg)
147 {
148 	/* We don't have real geometry info, but let's at least return
149 	   values consistent with the size of the device */
150 	sector_t nsect = get_capacity(bd->bd_disk);
151 	sector_t cylinders = nsect;
152 
153 	hg->heads = 0xff;
154 	hg->sectors = 0x3f;
155 	sector_div(cylinders, hg->heads * hg->sectors);
156 	hg->cylinders = cylinders;
157 	if ((sector_t)(hg->cylinders + 1) * hg->heads * hg->sectors < nsect)
158 		hg->cylinders = 0xffff;
159 	return 0;
160 }
161 
162 static int blkif_ioctl(struct block_device *bdev, fmode_t mode,
163 		       unsigned command, unsigned long argument)
164 {
165 	struct blkfront_info *info = bdev->bd_disk->private_data;
166 	int i;
167 
168 	dev_dbg(&info->xbdev->dev, "command: 0x%x, argument: 0x%lx\n",
169 		command, (long)argument);
170 
171 	switch (command) {
172 	case CDROMMULTISESSION:
173 		dev_dbg(&info->xbdev->dev, "FIXME: support multisession CDs later\n");
174 		for (i = 0; i < sizeof(struct cdrom_multisession); i++)
175 			if (put_user(0, (char __user *)(argument + i)))
176 				return -EFAULT;
177 		return 0;
178 
179 	case CDROM_GET_CAPABILITY: {
180 		struct gendisk *gd = info->gd;
181 		if (gd->flags & GENHD_FL_CD)
182 			return 0;
183 		return -EINVAL;
184 	}
185 
186 	default:
187 		/*printk(KERN_ALERT "ioctl %08x not supported by Xen blkdev\n",
188 		  command);*/
189 		return -EINVAL; /* same return as native Linux */
190 	}
191 
192 	return 0;
193 }
194 
195 /*
196  * blkif_queue_request
197  *
198  * request block io
199  *
200  * id: for guest use only.
201  * operation: BLKIF_OP_{READ,WRITE,PROBE}
202  * buffer: buffer to read/write into. this should be a
203  *   virtual address in the guest os.
204  */
205 static int blkif_queue_request(struct request *req)
206 {
207 	struct blkfront_info *info = req->rq_disk->private_data;
208 	unsigned long buffer_mfn;
209 	struct blkif_request *ring_req;
210 	unsigned long id;
211 	unsigned int fsect, lsect;
212 	int i, ref;
213 	grant_ref_t gref_head;
214 	struct scatterlist *sg;
215 
216 	if (unlikely(info->connected != BLKIF_STATE_CONNECTED))
217 		return 1;
218 
219 	if (gnttab_alloc_grant_references(
220 		BLKIF_MAX_SEGMENTS_PER_REQUEST, &gref_head) < 0) {
221 		gnttab_request_free_callback(
222 			&info->callback,
223 			blkif_restart_queue_callback,
224 			info,
225 			BLKIF_MAX_SEGMENTS_PER_REQUEST);
226 		return 1;
227 	}
228 
229 	/* Fill out a communications ring structure. */
230 	ring_req = RING_GET_REQUEST(&info->ring, info->ring.req_prod_pvt);
231 	id = get_id_from_freelist(info);
232 	info->shadow[id].request = (unsigned long)req;
233 
234 	ring_req->id = id;
235 	ring_req->sector_number = (blkif_sector_t)blk_rq_pos(req);
236 	ring_req->handle = info->handle;
237 
238 	ring_req->operation = rq_data_dir(req) ?
239 		BLKIF_OP_WRITE : BLKIF_OP_READ;
240 	if (blk_barrier_rq(req))
241 		ring_req->operation = BLKIF_OP_WRITE_BARRIER;
242 
243 	ring_req->nr_segments = blk_rq_map_sg(req->q, req, info->sg);
244 	BUG_ON(ring_req->nr_segments > BLKIF_MAX_SEGMENTS_PER_REQUEST);
245 
246 	for_each_sg(info->sg, sg, ring_req->nr_segments, i) {
247 		buffer_mfn = pfn_to_mfn(page_to_pfn(sg_page(sg)));
248 		fsect = sg->offset >> 9;
249 		lsect = fsect + (sg->length >> 9) - 1;
250 		/* install a grant reference. */
251 		ref = gnttab_claim_grant_reference(&gref_head);
252 		BUG_ON(ref == -ENOSPC);
253 
254 		gnttab_grant_foreign_access_ref(
255 				ref,
256 				info->xbdev->otherend_id,
257 				buffer_mfn,
258 				rq_data_dir(req) );
259 
260 		info->shadow[id].frame[i] = mfn_to_pfn(buffer_mfn);
261 		ring_req->seg[i] =
262 				(struct blkif_request_segment) {
263 					.gref       = ref,
264 					.first_sect = fsect,
265 					.last_sect  = lsect };
266 	}
267 
268 	info->ring.req_prod_pvt++;
269 
270 	/* Keep a private copy so we can reissue requests when recovering. */
271 	info->shadow[id].req = *ring_req;
272 
273 	gnttab_free_grant_references(gref_head);
274 
275 	return 0;
276 }
277 
278 
279 static inline void flush_requests(struct blkfront_info *info)
280 {
281 	int notify;
282 
283 	RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&info->ring, notify);
284 
285 	if (notify)
286 		notify_remote_via_irq(info->irq);
287 }
288 
289 /*
290  * do_blkif_request
291  *  read a block; request is in a request queue
292  */
293 static void do_blkif_request(struct request_queue *rq)
294 {
295 	struct blkfront_info *info = NULL;
296 	struct request *req;
297 	int queued;
298 
299 	pr_debug("Entered do_blkif_request\n");
300 
301 	queued = 0;
302 
303 	while ((req = blk_peek_request(rq)) != NULL) {
304 		info = req->rq_disk->private_data;
305 
306 		if (RING_FULL(&info->ring))
307 			goto wait;
308 
309 		blk_start_request(req);
310 
311 		if (!blk_fs_request(req)) {
312 			__blk_end_request_all(req, -EIO);
313 			continue;
314 		}
315 
316 		pr_debug("do_blk_req %p: cmd %p, sec %lx, "
317 			 "(%u/%u) buffer:%p [%s]\n",
318 			 req, req->cmd, (unsigned long)blk_rq_pos(req),
319 			 blk_rq_cur_sectors(req), blk_rq_sectors(req),
320 			 req->buffer, rq_data_dir(req) ? "write" : "read");
321 
322 		if (blkif_queue_request(req)) {
323 			blk_requeue_request(rq, req);
324 wait:
325 			/* Avoid pointless unplugs. */
326 			blk_stop_queue(rq);
327 			break;
328 		}
329 
330 		queued++;
331 	}
332 
333 	if (queued != 0)
334 		flush_requests(info);
335 }
336 
337 static int xlvbd_init_blk_queue(struct gendisk *gd, u16 sector_size)
338 {
339 	struct request_queue *rq;
340 
341 	rq = blk_init_queue(do_blkif_request, &blkif_io_lock);
342 	if (rq == NULL)
343 		return -1;
344 
345 	queue_flag_set_unlocked(QUEUE_FLAG_VIRT, rq);
346 
347 	/* Hard sector size and max sectors impersonate the equiv. hardware. */
348 	blk_queue_logical_block_size(rq, sector_size);
349 	blk_queue_max_sectors(rq, 512);
350 
351 	/* Each segment in a request is up to an aligned page in size. */
352 	blk_queue_segment_boundary(rq, PAGE_SIZE - 1);
353 	blk_queue_max_segment_size(rq, PAGE_SIZE);
354 
355 	/* Ensure a merged request will fit in a single I/O ring slot. */
356 	blk_queue_max_phys_segments(rq, BLKIF_MAX_SEGMENTS_PER_REQUEST);
357 	blk_queue_max_hw_segments(rq, BLKIF_MAX_SEGMENTS_PER_REQUEST);
358 
359 	/* Make sure buffer addresses are sector-aligned. */
360 	blk_queue_dma_alignment(rq, 511);
361 
362 	/* Make sure we don't use bounce buffers. */
363 	blk_queue_bounce_limit(rq, BLK_BOUNCE_ANY);
364 
365 	gd->queue = rq;
366 
367 	return 0;
368 }
369 
370 
371 static int xlvbd_barrier(struct blkfront_info *info)
372 {
373 	int err;
374 
375 	err = blk_queue_ordered(info->rq,
376 				info->feature_barrier ? QUEUE_ORDERED_DRAIN : QUEUE_ORDERED_NONE,
377 				NULL);
378 
379 	if (err)
380 		return err;
381 
382 	printk(KERN_INFO "blkfront: %s: barriers %s\n",
383 	       info->gd->disk_name,
384 	       info->feature_barrier ? "enabled" : "disabled");
385 	return 0;
386 }
387 
388 
389 static int xlvbd_alloc_gendisk(blkif_sector_t capacity,
390 			       struct blkfront_info *info,
391 			       u16 vdisk_info, u16 sector_size)
392 {
393 	struct gendisk *gd;
394 	int nr_minors = 1;
395 	int err = -ENODEV;
396 	unsigned int offset;
397 	int minor;
398 	int nr_parts;
399 
400 	BUG_ON(info->gd != NULL);
401 	BUG_ON(info->rq != NULL);
402 
403 	if ((info->vdevice>>EXT_SHIFT) > 1) {
404 		/* this is above the extended range; something is wrong */
405 		printk(KERN_WARNING "blkfront: vdevice 0x%x is above the extended range; ignoring\n", info->vdevice);
406 		return -ENODEV;
407 	}
408 
409 	if (!VDEV_IS_EXTENDED(info->vdevice)) {
410 		minor = BLKIF_MINOR(info->vdevice);
411 		nr_parts = PARTS_PER_DISK;
412 	} else {
413 		minor = BLKIF_MINOR_EXT(info->vdevice);
414 		nr_parts = PARTS_PER_EXT_DISK;
415 	}
416 
417 	if ((minor % nr_parts) == 0)
418 		nr_minors = nr_parts;
419 
420 	gd = alloc_disk(nr_minors);
421 	if (gd == NULL)
422 		goto out;
423 
424 	offset = minor / nr_parts;
425 
426 	if (nr_minors > 1) {
427 		if (offset < 26)
428 			sprintf(gd->disk_name, "%s%c", DEV_NAME, 'a' + offset);
429 		else
430 			sprintf(gd->disk_name, "%s%c%c", DEV_NAME,
431 				'a' + ((offset / 26)-1), 'a' + (offset % 26));
432 	} else {
433 		if (offset < 26)
434 			sprintf(gd->disk_name, "%s%c%d", DEV_NAME,
435 				'a' + offset,
436 				minor & (nr_parts - 1));
437 		else
438 			sprintf(gd->disk_name, "%s%c%c%d", DEV_NAME,
439 				'a' + ((offset / 26) - 1),
440 				'a' + (offset % 26),
441 				minor & (nr_parts - 1));
442 	}
443 
444 	gd->major = XENVBD_MAJOR;
445 	gd->first_minor = minor;
446 	gd->fops = &xlvbd_block_fops;
447 	gd->private_data = info;
448 	gd->driverfs_dev = &(info->xbdev->dev);
449 	set_capacity(gd, capacity);
450 
451 	if (xlvbd_init_blk_queue(gd, sector_size)) {
452 		del_gendisk(gd);
453 		goto out;
454 	}
455 
456 	info->rq = gd->queue;
457 	info->gd = gd;
458 
459 	if (info->feature_barrier)
460 		xlvbd_barrier(info);
461 
462 	if (vdisk_info & VDISK_READONLY)
463 		set_disk_ro(gd, 1);
464 
465 	if (vdisk_info & VDISK_REMOVABLE)
466 		gd->flags |= GENHD_FL_REMOVABLE;
467 
468 	if (vdisk_info & VDISK_CDROM)
469 		gd->flags |= GENHD_FL_CD;
470 
471 	return 0;
472 
473  out:
474 	return err;
475 }
476 
477 static void kick_pending_request_queues(struct blkfront_info *info)
478 {
479 	if (!RING_FULL(&info->ring)) {
480 		/* Re-enable calldowns. */
481 		blk_start_queue(info->rq);
482 		/* Kick things off immediately. */
483 		do_blkif_request(info->rq);
484 	}
485 }
486 
487 static void blkif_restart_queue(struct work_struct *work)
488 {
489 	struct blkfront_info *info = container_of(work, struct blkfront_info, work);
490 
491 	spin_lock_irq(&blkif_io_lock);
492 	if (info->connected == BLKIF_STATE_CONNECTED)
493 		kick_pending_request_queues(info);
494 	spin_unlock_irq(&blkif_io_lock);
495 }
496 
497 static void blkif_free(struct blkfront_info *info, int suspend)
498 {
499 	/* Prevent new requests being issued until we fix things up. */
500 	spin_lock_irq(&blkif_io_lock);
501 	info->connected = suspend ?
502 		BLKIF_STATE_SUSPENDED : BLKIF_STATE_DISCONNECTED;
503 	/* No more blkif_request(). */
504 	if (info->rq)
505 		blk_stop_queue(info->rq);
506 	/* No more gnttab callback work. */
507 	gnttab_cancel_free_callback(&info->callback);
508 	spin_unlock_irq(&blkif_io_lock);
509 
510 	/* Flush gnttab callback work. Must be done with no locks held. */
511 	flush_scheduled_work();
512 
513 	/* Free resources associated with old device channel. */
514 	if (info->ring_ref != GRANT_INVALID_REF) {
515 		gnttab_end_foreign_access(info->ring_ref, 0,
516 					  (unsigned long)info->ring.sring);
517 		info->ring_ref = GRANT_INVALID_REF;
518 		info->ring.sring = NULL;
519 	}
520 	if (info->irq)
521 		unbind_from_irqhandler(info->irq, info);
522 	info->evtchn = info->irq = 0;
523 
524 }
525 
526 static void blkif_completion(struct blk_shadow *s)
527 {
528 	int i;
529 	for (i = 0; i < s->req.nr_segments; i++)
530 		gnttab_end_foreign_access(s->req.seg[i].gref, 0, 0UL);
531 }
532 
533 static irqreturn_t blkif_interrupt(int irq, void *dev_id)
534 {
535 	struct request *req;
536 	struct blkif_response *bret;
537 	RING_IDX i, rp;
538 	unsigned long flags;
539 	struct blkfront_info *info = (struct blkfront_info *)dev_id;
540 	int error;
541 
542 	spin_lock_irqsave(&blkif_io_lock, flags);
543 
544 	if (unlikely(info->connected != BLKIF_STATE_CONNECTED)) {
545 		spin_unlock_irqrestore(&blkif_io_lock, flags);
546 		return IRQ_HANDLED;
547 	}
548 
549  again:
550 	rp = info->ring.sring->rsp_prod;
551 	rmb(); /* Ensure we see queued responses up to 'rp'. */
552 
553 	for (i = info->ring.rsp_cons; i != rp; i++) {
554 		unsigned long id;
555 
556 		bret = RING_GET_RESPONSE(&info->ring, i);
557 		id   = bret->id;
558 		req  = (struct request *)info->shadow[id].request;
559 
560 		blkif_completion(&info->shadow[id]);
561 
562 		add_id_to_freelist(info, id);
563 
564 		error = (bret->status == BLKIF_RSP_OKAY) ? 0 : -EIO;
565 		switch (bret->operation) {
566 		case BLKIF_OP_WRITE_BARRIER:
567 			if (unlikely(bret->status == BLKIF_RSP_EOPNOTSUPP)) {
568 				printk(KERN_WARNING "blkfront: %s: write barrier op failed\n",
569 				       info->gd->disk_name);
570 				error = -EOPNOTSUPP;
571 				info->feature_barrier = 0;
572 				xlvbd_barrier(info);
573 			}
574 			/* fall through */
575 		case BLKIF_OP_READ:
576 		case BLKIF_OP_WRITE:
577 			if (unlikely(bret->status != BLKIF_RSP_OKAY))
578 				dev_dbg(&info->xbdev->dev, "Bad return from blkdev data "
579 					"request: %x\n", bret->status);
580 
581 			__blk_end_request_all(req, error);
582 			break;
583 		default:
584 			BUG();
585 		}
586 	}
587 
588 	info->ring.rsp_cons = i;
589 
590 	if (i != info->ring.req_prod_pvt) {
591 		int more_to_do;
592 		RING_FINAL_CHECK_FOR_RESPONSES(&info->ring, more_to_do);
593 		if (more_to_do)
594 			goto again;
595 	} else
596 		info->ring.sring->rsp_event = i + 1;
597 
598 	kick_pending_request_queues(info);
599 
600 	spin_unlock_irqrestore(&blkif_io_lock, flags);
601 
602 	return IRQ_HANDLED;
603 }
604 
605 
606 static int setup_blkring(struct xenbus_device *dev,
607 			 struct blkfront_info *info)
608 {
609 	struct blkif_sring *sring;
610 	int err;
611 
612 	info->ring_ref = GRANT_INVALID_REF;
613 
614 	sring = (struct blkif_sring *)__get_free_page(GFP_NOIO | __GFP_HIGH);
615 	if (!sring) {
616 		xenbus_dev_fatal(dev, -ENOMEM, "allocating shared ring");
617 		return -ENOMEM;
618 	}
619 	SHARED_RING_INIT(sring);
620 	FRONT_RING_INIT(&info->ring, sring, PAGE_SIZE);
621 
622 	sg_init_table(info->sg, BLKIF_MAX_SEGMENTS_PER_REQUEST);
623 
624 	err = xenbus_grant_ring(dev, virt_to_mfn(info->ring.sring));
625 	if (err < 0) {
626 		free_page((unsigned long)sring);
627 		info->ring.sring = NULL;
628 		goto fail;
629 	}
630 	info->ring_ref = err;
631 
632 	err = xenbus_alloc_evtchn(dev, &info->evtchn);
633 	if (err)
634 		goto fail;
635 
636 	err = bind_evtchn_to_irqhandler(info->evtchn,
637 					blkif_interrupt,
638 					IRQF_SAMPLE_RANDOM, "blkif", info);
639 	if (err <= 0) {
640 		xenbus_dev_fatal(dev, err,
641 				 "bind_evtchn_to_irqhandler failed");
642 		goto fail;
643 	}
644 	info->irq = err;
645 
646 	return 0;
647 fail:
648 	blkif_free(info, 0);
649 	return err;
650 }
651 
652 
653 /* Common code used when first setting up, and when resuming. */
654 static int talk_to_backend(struct xenbus_device *dev,
655 			   struct blkfront_info *info)
656 {
657 	const char *message = NULL;
658 	struct xenbus_transaction xbt;
659 	int err;
660 
661 	/* Create shared ring, alloc event channel. */
662 	err = setup_blkring(dev, info);
663 	if (err)
664 		goto out;
665 
666 again:
667 	err = xenbus_transaction_start(&xbt);
668 	if (err) {
669 		xenbus_dev_fatal(dev, err, "starting transaction");
670 		goto destroy_blkring;
671 	}
672 
673 	err = xenbus_printf(xbt, dev->nodename,
674 			    "ring-ref", "%u", info->ring_ref);
675 	if (err) {
676 		message = "writing ring-ref";
677 		goto abort_transaction;
678 	}
679 	err = xenbus_printf(xbt, dev->nodename,
680 			    "event-channel", "%u", info->evtchn);
681 	if (err) {
682 		message = "writing event-channel";
683 		goto abort_transaction;
684 	}
685 	err = xenbus_printf(xbt, dev->nodename, "protocol", "%s",
686 			    XEN_IO_PROTO_ABI_NATIVE);
687 	if (err) {
688 		message = "writing protocol";
689 		goto abort_transaction;
690 	}
691 
692 	err = xenbus_transaction_end(xbt, 0);
693 	if (err) {
694 		if (err == -EAGAIN)
695 			goto again;
696 		xenbus_dev_fatal(dev, err, "completing transaction");
697 		goto destroy_blkring;
698 	}
699 
700 	xenbus_switch_state(dev, XenbusStateInitialised);
701 
702 	return 0;
703 
704  abort_transaction:
705 	xenbus_transaction_end(xbt, 1);
706 	if (message)
707 		xenbus_dev_fatal(dev, err, "%s", message);
708  destroy_blkring:
709 	blkif_free(info, 0);
710  out:
711 	return err;
712 }
713 
714 
715 /**
716  * Entry point to this code when a new device is created.  Allocate the basic
717  * structures and the ring buffer for communication with the backend, and
718  * inform the backend of the appropriate details for those.  Switch to
719  * Initialised state.
720  */
721 static int blkfront_probe(struct xenbus_device *dev,
722 			  const struct xenbus_device_id *id)
723 {
724 	int err, vdevice, i;
725 	struct blkfront_info *info;
726 
727 	/* FIXME: Use dynamic device id if this is not set. */
728 	err = xenbus_scanf(XBT_NIL, dev->nodename,
729 			   "virtual-device", "%i", &vdevice);
730 	if (err != 1) {
731 		/* go looking in the extended area instead */
732 		err = xenbus_scanf(XBT_NIL, dev->nodename, "virtual-device-ext",
733 				   "%i", &vdevice);
734 		if (err != 1) {
735 			xenbus_dev_fatal(dev, err, "reading virtual-device");
736 			return err;
737 		}
738 	}
739 
740 	info = kzalloc(sizeof(*info), GFP_KERNEL);
741 	if (!info) {
742 		xenbus_dev_fatal(dev, -ENOMEM, "allocating info structure");
743 		return -ENOMEM;
744 	}
745 
746 	info->xbdev = dev;
747 	info->vdevice = vdevice;
748 	info->connected = BLKIF_STATE_DISCONNECTED;
749 	INIT_WORK(&info->work, blkif_restart_queue);
750 
751 	for (i = 0; i < BLK_RING_SIZE; i++)
752 		info->shadow[i].req.id = i+1;
753 	info->shadow[BLK_RING_SIZE-1].req.id = 0x0fffffff;
754 
755 	/* Front end dir is a number, which is used as the id. */
756 	info->handle = simple_strtoul(strrchr(dev->nodename, '/')+1, NULL, 0);
757 	dev_set_drvdata(&dev->dev, info);
758 
759 	err = talk_to_backend(dev, info);
760 	if (err) {
761 		kfree(info);
762 		dev_set_drvdata(&dev->dev, NULL);
763 		return err;
764 	}
765 
766 	return 0;
767 }
768 
769 
770 static int blkif_recover(struct blkfront_info *info)
771 {
772 	int i;
773 	struct blkif_request *req;
774 	struct blk_shadow *copy;
775 	int j;
776 
777 	/* Stage 1: Make a safe copy of the shadow state. */
778 	copy = kmalloc(sizeof(info->shadow),
779 		       GFP_NOIO | __GFP_REPEAT | __GFP_HIGH);
780 	if (!copy)
781 		return -ENOMEM;
782 	memcpy(copy, info->shadow, sizeof(info->shadow));
783 
784 	/* Stage 2: Set up free list. */
785 	memset(&info->shadow, 0, sizeof(info->shadow));
786 	for (i = 0; i < BLK_RING_SIZE; i++)
787 		info->shadow[i].req.id = i+1;
788 	info->shadow_free = info->ring.req_prod_pvt;
789 	info->shadow[BLK_RING_SIZE-1].req.id = 0x0fffffff;
790 
791 	/* Stage 3: Find pending requests and requeue them. */
792 	for (i = 0; i < BLK_RING_SIZE; i++) {
793 		/* Not in use? */
794 		if (copy[i].request == 0)
795 			continue;
796 
797 		/* Grab a request slot and copy shadow state into it. */
798 		req = RING_GET_REQUEST(&info->ring, info->ring.req_prod_pvt);
799 		*req = copy[i].req;
800 
801 		/* We get a new request id, and must reset the shadow state. */
802 		req->id = get_id_from_freelist(info);
803 		memcpy(&info->shadow[req->id], &copy[i], sizeof(copy[i]));
804 
805 		/* Rewrite any grant references invalidated by susp/resume. */
806 		for (j = 0; j < req->nr_segments; j++)
807 			gnttab_grant_foreign_access_ref(
808 				req->seg[j].gref,
809 				info->xbdev->otherend_id,
810 				pfn_to_mfn(info->shadow[req->id].frame[j]),
811 				rq_data_dir(
812 					(struct request *)
813 					info->shadow[req->id].request));
814 		info->shadow[req->id].req = *req;
815 
816 		info->ring.req_prod_pvt++;
817 	}
818 
819 	kfree(copy);
820 
821 	xenbus_switch_state(info->xbdev, XenbusStateConnected);
822 
823 	spin_lock_irq(&blkif_io_lock);
824 
825 	/* Now safe for us to use the shared ring */
826 	info->connected = BLKIF_STATE_CONNECTED;
827 
828 	/* Send off requeued requests */
829 	flush_requests(info);
830 
831 	/* Kick any other new requests queued since we resumed */
832 	kick_pending_request_queues(info);
833 
834 	spin_unlock_irq(&blkif_io_lock);
835 
836 	return 0;
837 }
838 
839 /**
840  * We are reconnecting to the backend, due to a suspend/resume, or a backend
841  * driver restart.  We tear down our blkif structure and recreate it, but
842  * leave the device-layer structures intact so that this is transparent to the
843  * rest of the kernel.
844  */
845 static int blkfront_resume(struct xenbus_device *dev)
846 {
847 	struct blkfront_info *info = dev_get_drvdata(&dev->dev);
848 	int err;
849 
850 	dev_dbg(&dev->dev, "blkfront_resume: %s\n", dev->nodename);
851 
852 	blkif_free(info, info->connected == BLKIF_STATE_CONNECTED);
853 
854 	err = talk_to_backend(dev, info);
855 	if (info->connected == BLKIF_STATE_SUSPENDED && !err)
856 		err = blkif_recover(info);
857 
858 	return err;
859 }
860 
861 
862 /*
863  * Invoked when the backend is finally 'ready' (and has told produced
864  * the details about the physical device - #sectors, size, etc).
865  */
866 static void blkfront_connect(struct blkfront_info *info)
867 {
868 	unsigned long long sectors;
869 	unsigned long sector_size;
870 	unsigned int binfo;
871 	int err;
872 
873 	if ((info->connected == BLKIF_STATE_CONNECTED) ||
874 	    (info->connected == BLKIF_STATE_SUSPENDED) )
875 		return;
876 
877 	dev_dbg(&info->xbdev->dev, "%s:%s.\n",
878 		__func__, info->xbdev->otherend);
879 
880 	err = xenbus_gather(XBT_NIL, info->xbdev->otherend,
881 			    "sectors", "%llu", &sectors,
882 			    "info", "%u", &binfo,
883 			    "sector-size", "%lu", &sector_size,
884 			    NULL);
885 	if (err) {
886 		xenbus_dev_fatal(info->xbdev, err,
887 				 "reading backend fields at %s",
888 				 info->xbdev->otherend);
889 		return;
890 	}
891 
892 	err = xenbus_gather(XBT_NIL, info->xbdev->otherend,
893 			    "feature-barrier", "%lu", &info->feature_barrier,
894 			    NULL);
895 	if (err)
896 		info->feature_barrier = 0;
897 
898 	err = xlvbd_alloc_gendisk(sectors, info, binfo, sector_size);
899 	if (err) {
900 		xenbus_dev_fatal(info->xbdev, err, "xlvbd_add at %s",
901 				 info->xbdev->otherend);
902 		return;
903 	}
904 
905 	xenbus_switch_state(info->xbdev, XenbusStateConnected);
906 
907 	/* Kick pending requests. */
908 	spin_lock_irq(&blkif_io_lock);
909 	info->connected = BLKIF_STATE_CONNECTED;
910 	kick_pending_request_queues(info);
911 	spin_unlock_irq(&blkif_io_lock);
912 
913 	add_disk(info->gd);
914 
915 	info->is_ready = 1;
916 }
917 
918 /**
919  * Handle the change of state of the backend to Closing.  We must delete our
920  * device-layer structures now, to ensure that writes are flushed through to
921  * the backend.  Once is this done, we can switch to Closed in
922  * acknowledgement.
923  */
924 static void blkfront_closing(struct xenbus_device *dev)
925 {
926 	struct blkfront_info *info = dev_get_drvdata(&dev->dev);
927 	unsigned long flags;
928 
929 	dev_dbg(&dev->dev, "blkfront_closing: %s removed\n", dev->nodename);
930 
931 	if (info->rq == NULL)
932 		goto out;
933 
934 	spin_lock_irqsave(&blkif_io_lock, flags);
935 
936 	/* No more blkif_request(). */
937 	blk_stop_queue(info->rq);
938 
939 	/* No more gnttab callback work. */
940 	gnttab_cancel_free_callback(&info->callback);
941 	spin_unlock_irqrestore(&blkif_io_lock, flags);
942 
943 	/* Flush gnttab callback work. Must be done with no locks held. */
944 	flush_scheduled_work();
945 
946 	blk_cleanup_queue(info->rq);
947 	info->rq = NULL;
948 
949 	del_gendisk(info->gd);
950 
951  out:
952 	xenbus_frontend_closed(dev);
953 }
954 
955 /**
956  * Callback received when the backend's state changes.
957  */
958 static void backend_changed(struct xenbus_device *dev,
959 			    enum xenbus_state backend_state)
960 {
961 	struct blkfront_info *info = dev_get_drvdata(&dev->dev);
962 	struct block_device *bd;
963 
964 	dev_dbg(&dev->dev, "blkfront:backend_changed.\n");
965 
966 	switch (backend_state) {
967 	case XenbusStateInitialising:
968 	case XenbusStateInitWait:
969 	case XenbusStateInitialised:
970 	case XenbusStateUnknown:
971 	case XenbusStateClosed:
972 		break;
973 
974 	case XenbusStateConnected:
975 		blkfront_connect(info);
976 		break;
977 
978 	case XenbusStateClosing:
979 		if (info->gd == NULL) {
980 			xenbus_frontend_closed(dev);
981 			break;
982 		}
983 		bd = bdget_disk(info->gd, 0);
984 		if (bd == NULL)
985 			xenbus_dev_fatal(dev, -ENODEV, "bdget failed");
986 
987 		mutex_lock(&bd->bd_mutex);
988 		if (info->users > 0)
989 			xenbus_dev_error(dev, -EBUSY,
990 					 "Device in use; refusing to close");
991 		else
992 			blkfront_closing(dev);
993 		mutex_unlock(&bd->bd_mutex);
994 		bdput(bd);
995 		break;
996 	}
997 }
998 
999 static int blkfront_remove(struct xenbus_device *dev)
1000 {
1001 	struct blkfront_info *info = dev_get_drvdata(&dev->dev);
1002 
1003 	dev_dbg(&dev->dev, "blkfront_remove: %s removed\n", dev->nodename);
1004 
1005 	blkif_free(info, 0);
1006 
1007 	kfree(info);
1008 
1009 	return 0;
1010 }
1011 
1012 static int blkfront_is_ready(struct xenbus_device *dev)
1013 {
1014 	struct blkfront_info *info = dev_get_drvdata(&dev->dev);
1015 
1016 	return info->is_ready;
1017 }
1018 
1019 static int blkif_open(struct block_device *bdev, fmode_t mode)
1020 {
1021 	struct blkfront_info *info = bdev->bd_disk->private_data;
1022 	info->users++;
1023 	return 0;
1024 }
1025 
1026 static int blkif_release(struct gendisk *disk, fmode_t mode)
1027 {
1028 	struct blkfront_info *info = disk->private_data;
1029 	info->users--;
1030 	if (info->users == 0) {
1031 		/* Check whether we have been instructed to close.  We will
1032 		   have ignored this request initially, as the device was
1033 		   still mounted. */
1034 		struct xenbus_device *dev = info->xbdev;
1035 		enum xenbus_state state = xenbus_read_driver_state(dev->otherend);
1036 
1037 		if (state == XenbusStateClosing && info->is_ready)
1038 			blkfront_closing(dev);
1039 	}
1040 	return 0;
1041 }
1042 
1043 static const struct block_device_operations xlvbd_block_fops =
1044 {
1045 	.owner = THIS_MODULE,
1046 	.open = blkif_open,
1047 	.release = blkif_release,
1048 	.getgeo = blkif_getgeo,
1049 	.locked_ioctl = blkif_ioctl,
1050 };
1051 
1052 
1053 static struct xenbus_device_id blkfront_ids[] = {
1054 	{ "vbd" },
1055 	{ "" }
1056 };
1057 
1058 static struct xenbus_driver blkfront = {
1059 	.name = "vbd",
1060 	.owner = THIS_MODULE,
1061 	.ids = blkfront_ids,
1062 	.probe = blkfront_probe,
1063 	.remove = blkfront_remove,
1064 	.resume = blkfront_resume,
1065 	.otherend_changed = backend_changed,
1066 	.is_ready = blkfront_is_ready,
1067 };
1068 
1069 static int __init xlblk_init(void)
1070 {
1071 	if (!xen_domain())
1072 		return -ENODEV;
1073 
1074 	if (register_blkdev(XENVBD_MAJOR, DEV_NAME)) {
1075 		printk(KERN_WARNING "xen_blk: can't get major %d with name %s\n",
1076 		       XENVBD_MAJOR, DEV_NAME);
1077 		return -ENODEV;
1078 	}
1079 
1080 	return xenbus_register_frontend(&blkfront);
1081 }
1082 module_init(xlblk_init);
1083 
1084 
1085 static void __exit xlblk_exit(void)
1086 {
1087 	return xenbus_unregister_driver(&blkfront);
1088 }
1089 module_exit(xlblk_exit);
1090 
1091 MODULE_DESCRIPTION("Xen virtual block device frontend");
1092 MODULE_LICENSE("GPL");
1093 MODULE_ALIAS_BLOCKDEV_MAJOR(XENVBD_MAJOR);
1094 MODULE_ALIAS("xen:vbd");
1095 MODULE_ALIAS("xenblk");
1096