xen: Avoid allocations causing swap activity on the resume path
[linux-2.6.git] / drivers / block / xen-blkfront.c
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
44 #include <xen/xenbus.h>
45 #include <xen/grant_table.h>
46 #include <xen/events.h>
47 #include <xen/page.h>
48
49 #include <xen/interface/grant_table.h>
50 #include <xen/interface/io/blkif.h>
51 #include <xen/interface/io/protocols.h>
52
53 #include <asm/xen/hypervisor.h>
54
55 enum blkif_state {
56         BLKIF_STATE_DISCONNECTED,
57         BLKIF_STATE_CONNECTED,
58         BLKIF_STATE_SUSPENDED,
59 };
60
61 struct blk_shadow {
62         struct blkif_request req;
63         unsigned long request;
64         unsigned long frame[BLKIF_MAX_SEGMENTS_PER_REQUEST];
65 };
66
67 static struct block_device_operations xlvbd_block_fops;
68
69 #define BLK_RING_SIZE __RING_SIZE((struct blkif_sring *)0, PAGE_SIZE)
70
71 /*
72  * We have one of these per vbd, whether ide, scsi or 'other'.  They
73  * hang in private_data off the gendisk structure. We may end up
74  * putting all kinds of interesting stuff here :-)
75  */
76 struct blkfront_info
77 {
78         struct xenbus_device *xbdev;
79         struct gendisk *gd;
80         int vdevice;
81         blkif_vdev_t handle;
82         enum blkif_state connected;
83         int ring_ref;
84         struct blkif_front_ring ring;
85         unsigned int evtchn, irq;
86         struct request_queue *rq;
87         struct work_struct work;
88         struct gnttab_free_callback callback;
89         struct blk_shadow shadow[BLK_RING_SIZE];
90         unsigned long shadow_free;
91         int feature_barrier;
92         int is_ready;
93
94         /**
95          * The number of people holding this device open.  We won't allow a
96          * hot-unplug unless this is 0.
97          */
98         int users;
99 };
100
101 static DEFINE_SPINLOCK(blkif_io_lock);
102
103 #define MAXIMUM_OUTSTANDING_BLOCK_REQS \
104         (BLKIF_MAX_SEGMENTS_PER_REQUEST * BLK_RING_SIZE)
105 #define GRANT_INVALID_REF       0
106
107 #define PARTS_PER_DISK          16
108
109 #define BLKIF_MAJOR(dev) ((dev)>>8)
110 #define BLKIF_MINOR(dev) ((dev) & 0xff)
111
112 #define DEV_NAME        "xvd"   /* name in /dev */
113
114 /* Information about our VBDs. */
115 #define MAX_VBDS 64
116 static LIST_HEAD(vbds_list);
117
118 static int get_id_from_freelist(struct blkfront_info *info)
119 {
120         unsigned long free = info->shadow_free;
121         BUG_ON(free > BLK_RING_SIZE);
122         info->shadow_free = info->shadow[free].req.id;
123         info->shadow[free].req.id = 0x0fffffee; /* debug */
124         return free;
125 }
126
127 static void add_id_to_freelist(struct blkfront_info *info,
128                                unsigned long id)
129 {
130         info->shadow[id].req.id  = info->shadow_free;
131         info->shadow[id].request = 0;
132         info->shadow_free = id;
133 }
134
135 static void blkif_restart_queue_callback(void *arg)
136 {
137         struct blkfront_info *info = (struct blkfront_info *)arg;
138         schedule_work(&info->work);
139 }
140
141 static int blkif_getgeo(struct block_device *bd, struct hd_geometry *hg)
142 {
143         /* We don't have real geometry info, but let's at least return
144            values consistent with the size of the device */
145         sector_t nsect = get_capacity(bd->bd_disk);
146         sector_t cylinders = nsect;
147
148         hg->heads = 0xff;
149         hg->sectors = 0x3f;
150         sector_div(cylinders, hg->heads * hg->sectors);
151         hg->cylinders = cylinders;
152         if ((sector_t)(hg->cylinders + 1) * hg->heads * hg->sectors < nsect)
153                 hg->cylinders = 0xffff;
154         return 0;
155 }
156
157 int blkif_ioctl(struct inode *inode, struct file *filep,
158                 unsigned command, unsigned long argument)
159 {
160         struct blkfront_info *info =
161                 inode->i_bdev->bd_disk->private_data;
162         int i;
163
164         dev_dbg(&info->xbdev->dev, "command: 0x%x, argument: 0x%lx\n",
165                 command, (long)argument);
166
167         switch (command) {
168         case CDROMMULTISESSION:
169                 dev_dbg(&info->xbdev->dev, "FIXME: support multisession CDs later\n");
170                 for (i = 0; i < sizeof(struct cdrom_multisession); i++)
171                         if (put_user(0, (char __user *)(argument + i)))
172                                 return -EFAULT;
173                 return 0;
174
175         case CDROM_GET_CAPABILITY: {
176                 struct gendisk *gd = info->gd;
177                 if (gd->flags & GENHD_FL_CD)
178                         return 0;
179                 return -EINVAL;
180         }
181
182         default:
183                 /*printk(KERN_ALERT "ioctl %08x not supported by Xen blkdev\n",
184                   command);*/
185                 return -EINVAL; /* same return as native Linux */
186         }
187
188         return 0;
189 }
190
191 /*
192  * blkif_queue_request
193  *
194  * request block io
195  *
196  * id: for guest use only.
197  * operation: BLKIF_OP_{READ,WRITE,PROBE}
198  * buffer: buffer to read/write into. this should be a
199  *   virtual address in the guest os.
200  */
201 static int blkif_queue_request(struct request *req)
202 {
203         struct blkfront_info *info = req->rq_disk->private_data;
204         unsigned long buffer_mfn;
205         struct blkif_request *ring_req;
206         struct req_iterator iter;
207         struct bio_vec *bvec;
208         unsigned long id;
209         unsigned int fsect, lsect;
210         int ref;
211         grant_ref_t gref_head;
212
213         if (unlikely(info->connected != BLKIF_STATE_CONNECTED))
214                 return 1;
215
216         if (gnttab_alloc_grant_references(
217                 BLKIF_MAX_SEGMENTS_PER_REQUEST, &gref_head) < 0) {
218                 gnttab_request_free_callback(
219                         &info->callback,
220                         blkif_restart_queue_callback,
221                         info,
222                         BLKIF_MAX_SEGMENTS_PER_REQUEST);
223                 return 1;
224         }
225
226         /* Fill out a communications ring structure. */
227         ring_req = RING_GET_REQUEST(&info->ring, info->ring.req_prod_pvt);
228         id = get_id_from_freelist(info);
229         info->shadow[id].request = (unsigned long)req;
230
231         ring_req->id = id;
232         ring_req->sector_number = (blkif_sector_t)req->sector;
233         ring_req->handle = info->handle;
234
235         ring_req->operation = rq_data_dir(req) ?
236                 BLKIF_OP_WRITE : BLKIF_OP_READ;
237         if (blk_barrier_rq(req))
238                 ring_req->operation = BLKIF_OP_WRITE_BARRIER;
239
240         ring_req->nr_segments = 0;
241         rq_for_each_segment(bvec, req, iter) {
242                 BUG_ON(ring_req->nr_segments == BLKIF_MAX_SEGMENTS_PER_REQUEST);
243                 buffer_mfn = pfn_to_mfn(page_to_pfn(bvec->bv_page));
244                 fsect = bvec->bv_offset >> 9;
245                 lsect = fsect + (bvec->bv_len >> 9) - 1;
246                 /* install a grant reference. */
247                 ref = gnttab_claim_grant_reference(&gref_head);
248                 BUG_ON(ref == -ENOSPC);
249
250                 gnttab_grant_foreign_access_ref(
251                                 ref,
252                                 info->xbdev->otherend_id,
253                                 buffer_mfn,
254                                 rq_data_dir(req) );
255
256                 info->shadow[id].frame[ring_req->nr_segments] =
257                                 mfn_to_pfn(buffer_mfn);
258
259                 ring_req->seg[ring_req->nr_segments] =
260                                 (struct blkif_request_segment) {
261                                         .gref       = ref,
262                                         .first_sect = fsect,
263                                         .last_sect  = lsect };
264
265                 ring_req->nr_segments++;
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 = elv_next_request(rq)) != NULL) {
304                 info = req->rq_disk->private_data;
305                 if (!blk_fs_request(req)) {
306                         end_request(req, 0);
307                         continue;
308                 }
309
310                 if (RING_FULL(&info->ring))
311                         goto wait;
312
313                 pr_debug("do_blk_req %p: cmd %p, sec %lx, "
314                          "(%u/%li) buffer:%p [%s]\n",
315                          req, req->cmd, (unsigned long)req->sector,
316                          req->current_nr_sectors,
317                          req->nr_sectors, req->buffer,
318                          rq_data_dir(req) ? "write" : "read");
319
320
321                 blkdev_dequeue_request(req);
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         elevator_init(rq, "noop");
346
347         /* Hard sector size and max sectors impersonate the equiv. hardware. */
348         blk_queue_hardsect_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(int minor, blkif_sector_t capacity,
390                                int vdevice, u16 vdisk_info, u16 sector_size,
391                                struct blkfront_info *info)
392 {
393         struct gendisk *gd;
394         int nr_minors = 1;
395         int err = -ENODEV;
396
397         BUG_ON(info->gd != NULL);
398         BUG_ON(info->rq != NULL);
399
400         if ((minor % PARTS_PER_DISK) == 0)
401                 nr_minors = PARTS_PER_DISK;
402
403         gd = alloc_disk(nr_minors);
404         if (gd == NULL)
405                 goto out;
406
407         if (nr_minors > 1)
408                 sprintf(gd->disk_name, "%s%c", DEV_NAME,
409                         'a' + minor / PARTS_PER_DISK);
410         else
411                 sprintf(gd->disk_name, "%s%c%d", DEV_NAME,
412                         'a' + minor / PARTS_PER_DISK,
413                         minor % PARTS_PER_DISK);
414
415         gd->major = XENVBD_MAJOR;
416         gd->first_minor = minor;
417         gd->fops = &xlvbd_block_fops;
418         gd->private_data = info;
419         gd->driverfs_dev = &(info->xbdev->dev);
420         set_capacity(gd, capacity);
421
422         if (xlvbd_init_blk_queue(gd, sector_size)) {
423                 del_gendisk(gd);
424                 goto out;
425         }
426
427         info->rq = gd->queue;
428         info->gd = gd;
429
430         if (info->feature_barrier)
431                 xlvbd_barrier(info);
432
433         if (vdisk_info & VDISK_READONLY)
434                 set_disk_ro(gd, 1);
435
436         if (vdisk_info & VDISK_REMOVABLE)
437                 gd->flags |= GENHD_FL_REMOVABLE;
438
439         if (vdisk_info & VDISK_CDROM)
440                 gd->flags |= GENHD_FL_CD;
441
442         return 0;
443
444  out:
445         return err;
446 }
447
448 static void kick_pending_request_queues(struct blkfront_info *info)
449 {
450         if (!RING_FULL(&info->ring)) {
451                 /* Re-enable calldowns. */
452                 blk_start_queue(info->rq);
453                 /* Kick things off immediately. */
454                 do_blkif_request(info->rq);
455         }
456 }
457
458 static void blkif_restart_queue(struct work_struct *work)
459 {
460         struct blkfront_info *info = container_of(work, struct blkfront_info, work);
461
462         spin_lock_irq(&blkif_io_lock);
463         if (info->connected == BLKIF_STATE_CONNECTED)
464                 kick_pending_request_queues(info);
465         spin_unlock_irq(&blkif_io_lock);
466 }
467
468 static void blkif_free(struct blkfront_info *info, int suspend)
469 {
470         /* Prevent new requests being issued until we fix things up. */
471         spin_lock_irq(&blkif_io_lock);
472         info->connected = suspend ?
473                 BLKIF_STATE_SUSPENDED : BLKIF_STATE_DISCONNECTED;
474         /* No more blkif_request(). */
475         if (info->rq)
476                 blk_stop_queue(info->rq);
477         /* No more gnttab callback work. */
478         gnttab_cancel_free_callback(&info->callback);
479         spin_unlock_irq(&blkif_io_lock);
480
481         /* Flush gnttab callback work. Must be done with no locks held. */
482         flush_scheduled_work();
483
484         /* Free resources associated with old device channel. */
485         if (info->ring_ref != GRANT_INVALID_REF) {
486                 gnttab_end_foreign_access(info->ring_ref, 0,
487                                           (unsigned long)info->ring.sring);
488                 info->ring_ref = GRANT_INVALID_REF;
489                 info->ring.sring = NULL;
490         }
491         if (info->irq)
492                 unbind_from_irqhandler(info->irq, info);
493         info->evtchn = info->irq = 0;
494
495 }
496
497 static void blkif_completion(struct blk_shadow *s)
498 {
499         int i;
500         for (i = 0; i < s->req.nr_segments; i++)
501                 gnttab_end_foreign_access(s->req.seg[i].gref, 0, 0UL);
502 }
503
504 static irqreturn_t blkif_interrupt(int irq, void *dev_id)
505 {
506         struct request *req;
507         struct blkif_response *bret;
508         RING_IDX i, rp;
509         unsigned long flags;
510         struct blkfront_info *info = (struct blkfront_info *)dev_id;
511         int error;
512
513         spin_lock_irqsave(&blkif_io_lock, flags);
514
515         if (unlikely(info->connected != BLKIF_STATE_CONNECTED)) {
516                 spin_unlock_irqrestore(&blkif_io_lock, flags);
517                 return IRQ_HANDLED;
518         }
519
520  again:
521         rp = info->ring.sring->rsp_prod;
522         rmb(); /* Ensure we see queued responses up to 'rp'. */
523
524         for (i = info->ring.rsp_cons; i != rp; i++) {
525                 unsigned long id;
526                 int ret;
527
528                 bret = RING_GET_RESPONSE(&info->ring, i);
529                 id   = bret->id;
530                 req  = (struct request *)info->shadow[id].request;
531
532                 blkif_completion(&info->shadow[id]);
533
534                 add_id_to_freelist(info, id);
535
536                 error = (bret->status == BLKIF_RSP_OKAY) ? 0 : -EIO;
537                 switch (bret->operation) {
538                 case BLKIF_OP_WRITE_BARRIER:
539                         if (unlikely(bret->status == BLKIF_RSP_EOPNOTSUPP)) {
540                                 printk(KERN_WARNING "blkfront: %s: write barrier op failed\n",
541                                        info->gd->disk_name);
542                                 error = -EOPNOTSUPP;
543                                 info->feature_barrier = 0;
544                                 xlvbd_barrier(info);
545                         }
546                         /* fall through */
547                 case BLKIF_OP_READ:
548                 case BLKIF_OP_WRITE:
549                         if (unlikely(bret->status != BLKIF_RSP_OKAY))
550                                 dev_dbg(&info->xbdev->dev, "Bad return from blkdev data "
551                                         "request: %x\n", bret->status);
552
553                         ret = __blk_end_request(req, error, blk_rq_bytes(req));
554                         BUG_ON(ret);
555                         break;
556                 default:
557                         BUG();
558                 }
559         }
560
561         info->ring.rsp_cons = i;
562
563         if (i != info->ring.req_prod_pvt) {
564                 int more_to_do;
565                 RING_FINAL_CHECK_FOR_RESPONSES(&info->ring, more_to_do);
566                 if (more_to_do)
567                         goto again;
568         } else
569                 info->ring.sring->rsp_event = i + 1;
570
571         kick_pending_request_queues(info);
572
573         spin_unlock_irqrestore(&blkif_io_lock, flags);
574
575         return IRQ_HANDLED;
576 }
577
578
579 static int setup_blkring(struct xenbus_device *dev,
580                          struct blkfront_info *info)
581 {
582         struct blkif_sring *sring;
583         int err;
584
585         info->ring_ref = GRANT_INVALID_REF;
586
587         sring = (struct blkif_sring *)__get_free_page(GFP_NOIO | __GFP_HIGH);
588         if (!sring) {
589                 xenbus_dev_fatal(dev, -ENOMEM, "allocating shared ring");
590                 return -ENOMEM;
591         }
592         SHARED_RING_INIT(sring);
593         FRONT_RING_INIT(&info->ring, sring, PAGE_SIZE);
594
595         err = xenbus_grant_ring(dev, virt_to_mfn(info->ring.sring));
596         if (err < 0) {
597                 free_page((unsigned long)sring);
598                 info->ring.sring = NULL;
599                 goto fail;
600         }
601         info->ring_ref = err;
602
603         err = xenbus_alloc_evtchn(dev, &info->evtchn);
604         if (err)
605                 goto fail;
606
607         err = bind_evtchn_to_irqhandler(info->evtchn,
608                                         blkif_interrupt,
609                                         IRQF_SAMPLE_RANDOM, "blkif", info);
610         if (err <= 0) {
611                 xenbus_dev_fatal(dev, err,
612                                  "bind_evtchn_to_irqhandler failed");
613                 goto fail;
614         }
615         info->irq = err;
616
617         return 0;
618 fail:
619         blkif_free(info, 0);
620         return err;
621 }
622
623
624 /* Common code used when first setting up, and when resuming. */
625 static int talk_to_backend(struct xenbus_device *dev,
626                            struct blkfront_info *info)
627 {
628         const char *message = NULL;
629         struct xenbus_transaction xbt;
630         int err;
631
632         /* Create shared ring, alloc event channel. */
633         err = setup_blkring(dev, info);
634         if (err)
635                 goto out;
636
637 again:
638         err = xenbus_transaction_start(&xbt);
639         if (err) {
640                 xenbus_dev_fatal(dev, err, "starting transaction");
641                 goto destroy_blkring;
642         }
643
644         err = xenbus_printf(xbt, dev->nodename,
645                             "ring-ref", "%u", info->ring_ref);
646         if (err) {
647                 message = "writing ring-ref";
648                 goto abort_transaction;
649         }
650         err = xenbus_printf(xbt, dev->nodename,
651                             "event-channel", "%u", info->evtchn);
652         if (err) {
653                 message = "writing event-channel";
654                 goto abort_transaction;
655         }
656         err = xenbus_printf(xbt, dev->nodename, "protocol", "%s",
657                             XEN_IO_PROTO_ABI_NATIVE);
658         if (err) {
659                 message = "writing protocol";
660                 goto abort_transaction;
661         }
662
663         err = xenbus_transaction_end(xbt, 0);
664         if (err) {
665                 if (err == -EAGAIN)
666                         goto again;
667                 xenbus_dev_fatal(dev, err, "completing transaction");
668                 goto destroy_blkring;
669         }
670
671         xenbus_switch_state(dev, XenbusStateInitialised);
672
673         return 0;
674
675  abort_transaction:
676         xenbus_transaction_end(xbt, 1);
677         if (message)
678                 xenbus_dev_fatal(dev, err, "%s", message);
679  destroy_blkring:
680         blkif_free(info, 0);
681  out:
682         return err;
683 }
684
685
686 /**
687  * Entry point to this code when a new device is created.  Allocate the basic
688  * structures and the ring buffer for communication with the backend, and
689  * inform the backend of the appropriate details for those.  Switch to
690  * Initialised state.
691  */
692 static int blkfront_probe(struct xenbus_device *dev,
693                           const struct xenbus_device_id *id)
694 {
695         int err, vdevice, i;
696         struct blkfront_info *info;
697
698         /* FIXME: Use dynamic device id if this is not set. */
699         err = xenbus_scanf(XBT_NIL, dev->nodename,
700                            "virtual-device", "%i", &vdevice);
701         if (err != 1) {
702                 xenbus_dev_fatal(dev, err, "reading virtual-device");
703                 return err;
704         }
705
706         info = kzalloc(sizeof(*info), GFP_KERNEL);
707         if (!info) {
708                 xenbus_dev_fatal(dev, -ENOMEM, "allocating info structure");
709                 return -ENOMEM;
710         }
711
712         info->xbdev = dev;
713         info->vdevice = vdevice;
714         info->connected = BLKIF_STATE_DISCONNECTED;
715         INIT_WORK(&info->work, blkif_restart_queue);
716
717         for (i = 0; i < BLK_RING_SIZE; i++)
718                 info->shadow[i].req.id = i+1;
719         info->shadow[BLK_RING_SIZE-1].req.id = 0x0fffffff;
720
721         /* Front end dir is a number, which is used as the id. */
722         info->handle = simple_strtoul(strrchr(dev->nodename, '/')+1, NULL, 0);
723         dev->dev.driver_data = info;
724
725         err = talk_to_backend(dev, info);
726         if (err) {
727                 kfree(info);
728                 dev->dev.driver_data = NULL;
729                 return err;
730         }
731
732         return 0;
733 }
734
735
736 static int blkif_recover(struct blkfront_info *info)
737 {
738         int i;
739         struct blkif_request *req;
740         struct blk_shadow *copy;
741         int j;
742
743         /* Stage 1: Make a safe copy of the shadow state. */
744         copy = kmalloc(sizeof(info->shadow),
745                        GFP_NOIO | __GFP_REPEAT | __GFP_HIGH);
746         if (!copy)
747                 return -ENOMEM;
748         memcpy(copy, info->shadow, sizeof(info->shadow));
749
750         /* Stage 2: Set up free list. */
751         memset(&info->shadow, 0, sizeof(info->shadow));
752         for (i = 0; i < BLK_RING_SIZE; i++)
753                 info->shadow[i].req.id = i+1;
754         info->shadow_free = info->ring.req_prod_pvt;
755         info->shadow[BLK_RING_SIZE-1].req.id = 0x0fffffff;
756
757         /* Stage 3: Find pending requests and requeue them. */
758         for (i = 0; i < BLK_RING_SIZE; i++) {
759                 /* Not in use? */
760                 if (copy[i].request == 0)
761                         continue;
762
763                 /* Grab a request slot and copy shadow state into it. */
764                 req = RING_GET_REQUEST(&info->ring, info->ring.req_prod_pvt);
765                 *req = copy[i].req;
766
767                 /* We get a new request id, and must reset the shadow state. */
768                 req->id = get_id_from_freelist(info);
769                 memcpy(&info->shadow[req->id], &copy[i], sizeof(copy[i]));
770
771                 /* Rewrite any grant references invalidated by susp/resume. */
772                 for (j = 0; j < req->nr_segments; j++)
773                         gnttab_grant_foreign_access_ref(
774                                 req->seg[j].gref,
775                                 info->xbdev->otherend_id,
776                                 pfn_to_mfn(info->shadow[req->id].frame[j]),
777                                 rq_data_dir(
778                                         (struct request *)
779                                         info->shadow[req->id].request));
780                 info->shadow[req->id].req = *req;
781
782                 info->ring.req_prod_pvt++;
783         }
784
785         kfree(copy);
786
787         xenbus_switch_state(info->xbdev, XenbusStateConnected);
788
789         spin_lock_irq(&blkif_io_lock);
790
791         /* Now safe for us to use the shared ring */
792         info->connected = BLKIF_STATE_CONNECTED;
793
794         /* Send off requeued requests */
795         flush_requests(info);
796
797         /* Kick any other new requests queued since we resumed */
798         kick_pending_request_queues(info);
799
800         spin_unlock_irq(&blkif_io_lock);
801
802         return 0;
803 }
804
805 /**
806  * We are reconnecting to the backend, due to a suspend/resume, or a backend
807  * driver restart.  We tear down our blkif structure and recreate it, but
808  * leave the device-layer structures intact so that this is transparent to the
809  * rest of the kernel.
810  */
811 static int blkfront_resume(struct xenbus_device *dev)
812 {
813         struct blkfront_info *info = dev->dev.driver_data;
814         int err;
815
816         dev_dbg(&dev->dev, "blkfront_resume: %s\n", dev->nodename);
817
818         blkif_free(info, info->connected == BLKIF_STATE_CONNECTED);
819
820         err = talk_to_backend(dev, info);
821         if (info->connected == BLKIF_STATE_SUSPENDED && !err)
822                 err = blkif_recover(info);
823
824         return err;
825 }
826
827
828 /*
829  * Invoked when the backend is finally 'ready' (and has told produced
830  * the details about the physical device - #sectors, size, etc).
831  */
832 static void blkfront_connect(struct blkfront_info *info)
833 {
834         unsigned long long sectors;
835         unsigned long sector_size;
836         unsigned int binfo;
837         int err;
838
839         if ((info->connected == BLKIF_STATE_CONNECTED) ||
840             (info->connected == BLKIF_STATE_SUSPENDED) )
841                 return;
842
843         dev_dbg(&info->xbdev->dev, "%s:%s.\n",
844                 __func__, info->xbdev->otherend);
845
846         err = xenbus_gather(XBT_NIL, info->xbdev->otherend,
847                             "sectors", "%llu", &sectors,
848                             "info", "%u", &binfo,
849                             "sector-size", "%lu", &sector_size,
850                             NULL);
851         if (err) {
852                 xenbus_dev_fatal(info->xbdev, err,
853                                  "reading backend fields at %s",
854                                  info->xbdev->otherend);
855                 return;
856         }
857
858         err = xenbus_gather(XBT_NIL, info->xbdev->otherend,
859                             "feature-barrier", "%lu", &info->feature_barrier,
860                             NULL);
861         if (err)
862                 info->feature_barrier = 0;
863
864         err = xlvbd_alloc_gendisk(BLKIF_MINOR(info->vdevice),
865                                   sectors, info->vdevice,
866                                   binfo, sector_size, info);
867         if (err) {
868                 xenbus_dev_fatal(info->xbdev, err, "xlvbd_add at %s",
869                                  info->xbdev->otherend);
870                 return;
871         }
872
873         xenbus_switch_state(info->xbdev, XenbusStateConnected);
874
875         /* Kick pending requests. */
876         spin_lock_irq(&blkif_io_lock);
877         info->connected = BLKIF_STATE_CONNECTED;
878         kick_pending_request_queues(info);
879         spin_unlock_irq(&blkif_io_lock);
880
881         add_disk(info->gd);
882
883         info->is_ready = 1;
884 }
885
886 /**
887  * Handle the change of state of the backend to Closing.  We must delete our
888  * device-layer structures now, to ensure that writes are flushed through to
889  * the backend.  Once is this done, we can switch to Closed in
890  * acknowledgement.
891  */
892 static void blkfront_closing(struct xenbus_device *dev)
893 {
894         struct blkfront_info *info = dev->dev.driver_data;
895         unsigned long flags;
896
897         dev_dbg(&dev->dev, "blkfront_closing: %s removed\n", dev->nodename);
898
899         if (info->rq == NULL)
900                 goto out;
901
902         spin_lock_irqsave(&blkif_io_lock, flags);
903
904         del_gendisk(info->gd);
905
906         /* No more blkif_request(). */
907         blk_stop_queue(info->rq);
908
909         /* No more gnttab callback work. */
910         gnttab_cancel_free_callback(&info->callback);
911         spin_unlock_irqrestore(&blkif_io_lock, flags);
912
913         /* Flush gnttab callback work. Must be done with no locks held. */
914         flush_scheduled_work();
915
916         blk_cleanup_queue(info->rq);
917         info->rq = NULL;
918
919  out:
920         xenbus_frontend_closed(dev);
921 }
922
923 /**
924  * Callback received when the backend's state changes.
925  */
926 static void backend_changed(struct xenbus_device *dev,
927                             enum xenbus_state backend_state)
928 {
929         struct blkfront_info *info = dev->dev.driver_data;
930         struct block_device *bd;
931
932         dev_dbg(&dev->dev, "blkfront:backend_changed.\n");
933
934         switch (backend_state) {
935         case XenbusStateInitialising:
936         case XenbusStateInitWait:
937         case XenbusStateInitialised:
938         case XenbusStateUnknown:
939         case XenbusStateClosed:
940                 break;
941
942         case XenbusStateConnected:
943                 blkfront_connect(info);
944                 break;
945
946         case XenbusStateClosing:
947                 bd = bdget_disk(info->gd, 0);
948                 if (bd == NULL)
949                         xenbus_dev_fatal(dev, -ENODEV, "bdget failed");
950
951                 mutex_lock(&bd->bd_mutex);
952                 if (info->users > 0)
953                         xenbus_dev_error(dev, -EBUSY,
954                                          "Device in use; refusing to close");
955                 else
956                         blkfront_closing(dev);
957                 mutex_unlock(&bd->bd_mutex);
958                 bdput(bd);
959                 break;
960         }
961 }
962
963 static int blkfront_remove(struct xenbus_device *dev)
964 {
965         struct blkfront_info *info = dev->dev.driver_data;
966
967         dev_dbg(&dev->dev, "blkfront_remove: %s removed\n", dev->nodename);
968
969         blkif_free(info, 0);
970
971         kfree(info);
972
973         return 0;
974 }
975
976 static int blkfront_is_ready(struct xenbus_device *dev)
977 {
978         struct blkfront_info *info = dev->dev.driver_data;
979
980         return info->is_ready;
981 }
982
983 static int blkif_open(struct inode *inode, struct file *filep)
984 {
985         struct blkfront_info *info = inode->i_bdev->bd_disk->private_data;
986         info->users++;
987         return 0;
988 }
989
990 static int blkif_release(struct inode *inode, struct file *filep)
991 {
992         struct blkfront_info *info = inode->i_bdev->bd_disk->private_data;
993         info->users--;
994         if (info->users == 0) {
995                 /* Check whether we have been instructed to close.  We will
996                    have ignored this request initially, as the device was
997                    still mounted. */
998                 struct xenbus_device *dev = info->xbdev;
999                 enum xenbus_state state = xenbus_read_driver_state(dev->otherend);
1000
1001                 if (state == XenbusStateClosing && info->is_ready)
1002                         blkfront_closing(dev);
1003         }
1004         return 0;
1005 }
1006
1007 static struct block_device_operations xlvbd_block_fops =
1008 {
1009         .owner = THIS_MODULE,
1010         .open = blkif_open,
1011         .release = blkif_release,
1012         .getgeo = blkif_getgeo,
1013         .ioctl = blkif_ioctl,
1014 };
1015
1016
1017 static struct xenbus_device_id blkfront_ids[] = {
1018         { "vbd" },
1019         { "" }
1020 };
1021
1022 static struct xenbus_driver blkfront = {
1023         .name = "vbd",
1024         .owner = THIS_MODULE,
1025         .ids = blkfront_ids,
1026         .probe = blkfront_probe,
1027         .remove = blkfront_remove,
1028         .resume = blkfront_resume,
1029         .otherend_changed = backend_changed,
1030         .is_ready = blkfront_is_ready,
1031 };
1032
1033 static int __init xlblk_init(void)
1034 {
1035         if (!is_running_on_xen())
1036                 return -ENODEV;
1037
1038         if (register_blkdev(XENVBD_MAJOR, DEV_NAME)) {
1039                 printk(KERN_WARNING "xen_blk: can't get major %d with name %s\n",
1040                        XENVBD_MAJOR, DEV_NAME);
1041                 return -ENODEV;
1042         }
1043
1044         return xenbus_register_frontend(&blkfront);
1045 }
1046 module_init(xlblk_init);
1047
1048
1049 static void __exit xlblk_exit(void)
1050 {
1051         return xenbus_unregister_driver(&blkfront);
1052 }
1053 module_exit(xlblk_exit);
1054
1055 MODULE_DESCRIPTION("Xen virtual block device frontend");
1056 MODULE_LICENSE("GPL");
1057 MODULE_ALIAS_BLOCKDEV_MAJOR(XENVBD_MAJOR);
1058 MODULE_ALIAS("xen:vbd");
1059 MODULE_ALIAS("xenblk");