Merge tag 'for-linus-4.8-rc0-tag' of git://git.kernel.org/pub/scm/linux/kernel/git...
[sfrench/cifs-2.6.git] / drivers / block / xen-blkback / xenbus.c
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                             unsigned int);
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                 xen_blkif_get(blkif);
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->xenblkd) {
253                         kthread_stop(ring->xenblkd);
254                         wake_up(&ring->shutdown_wq);
255                         ring->xenblkd = NULL;
256                 }
257
258                 /* The above kthread_stop() guarantees that at this point we
259                  * don't have any discard_io or other_io requests. So, checking
260                  * for inflight IO is enough.
261                  */
262                 if (atomic_read(&ring->inflight) > 0)
263                         return -EBUSY;
264
265                 if (ring->irq) {
266                         unbind_from_irqhandler(ring->irq, ring);
267                         ring->irq = 0;
268                 }
269
270                 if (ring->blk_rings.common.sring) {
271                         xenbus_unmap_ring_vfree(blkif->be->dev, ring->blk_ring);
272                         ring->blk_rings.common.sring = NULL;
273                 }
274
275                 /* Remove all persistent grants and the cache of ballooned pages. */
276                 xen_blkbk_free_caches(ring);
277
278                 /* Check that there is no request in use */
279                 list_for_each_entry_safe(req, n, &ring->pending_free, free_list) {
280                         list_del(&req->free_list);
281
282                         for (j = 0; j < MAX_INDIRECT_SEGMENTS; j++)
283                                 kfree(req->segments[j]);
284
285                         for (j = 0; j < MAX_INDIRECT_PAGES; j++)
286                                 kfree(req->indirect_pages[j]);
287
288                         kfree(req);
289                         i++;
290                 }
291
292                 BUG_ON(atomic_read(&ring->persistent_gnt_in_use) != 0);
293                 BUG_ON(!list_empty(&ring->persistent_purge_list));
294                 BUG_ON(!RB_EMPTY_ROOT(&ring->persistent_gnts));
295                 BUG_ON(!list_empty(&ring->free_pages));
296                 BUG_ON(ring->free_pages_num != 0);
297                 BUG_ON(ring->persistent_gnt_c != 0);
298                 WARN_ON(i != (XEN_BLKIF_REQS_PER_PAGE * blkif->nr_ring_pages));
299                 xen_blkif_put(blkif);
300         }
301         blkif->nr_ring_pages = 0;
302         /*
303          * blkif->rings was allocated in connect_ring, so we should free it in
304          * here.
305          */
306         kfree(blkif->rings);
307         blkif->rings = NULL;
308         blkif->nr_rings = 0;
309
310         return 0;
311 }
312
313 static void xen_blkif_free(struct xen_blkif *blkif)
314 {
315
316         xen_blkif_disconnect(blkif);
317         xen_vbd_free(&blkif->vbd);
318
319         /* Make sure everything is drained before shutting down */
320         kmem_cache_free(xen_blkif_cachep, blkif);
321 }
322
323 int __init xen_blkif_interface_init(void)
324 {
325         xen_blkif_cachep = kmem_cache_create("blkif_cache",
326                                              sizeof(struct xen_blkif),
327                                              0, 0, NULL);
328         if (!xen_blkif_cachep)
329                 return -ENOMEM;
330
331         return 0;
332 }
333
334 /*
335  *  sysfs interface for VBD I/O requests
336  */
337
338 #define VBD_SHOW_ALLRING(name, format)                                  \
339         static ssize_t show_##name(struct device *_dev,                 \
340                                    struct device_attribute *attr,       \
341                                    char *buf)                           \
342         {                                                               \
343                 struct xenbus_device *dev = to_xenbus_device(_dev);     \
344                 struct backend_info *be = dev_get_drvdata(&dev->dev);   \
345                 struct xen_blkif *blkif = be->blkif;                    \
346                 unsigned int i;                                         \
347                 unsigned long long result = 0;                          \
348                                                                         \
349                 if (!blkif->rings)                              \
350                         goto out;                                       \
351                                                                         \
352                 for (i = 0; i < blkif->nr_rings; i++) {         \
353                         struct xen_blkif_ring *ring = &blkif->rings[i]; \
354                                                                         \
355                         result += ring->st_##name;                      \
356                 }                                                       \
357                                                                         \
358 out:                                                                    \
359                 return sprintf(buf, format, result);                    \
360         }                                                               \
361         static DEVICE_ATTR(name, S_IRUGO, show_##name, NULL)
362
363 VBD_SHOW_ALLRING(oo_req,  "%llu\n");
364 VBD_SHOW_ALLRING(rd_req,  "%llu\n");
365 VBD_SHOW_ALLRING(wr_req,  "%llu\n");
366 VBD_SHOW_ALLRING(f_req,  "%llu\n");
367 VBD_SHOW_ALLRING(ds_req,  "%llu\n");
368 VBD_SHOW_ALLRING(rd_sect, "%llu\n");
369 VBD_SHOW_ALLRING(wr_sect, "%llu\n");
370
371 static struct attribute *xen_vbdstat_attrs[] = {
372         &dev_attr_oo_req.attr,
373         &dev_attr_rd_req.attr,
374         &dev_attr_wr_req.attr,
375         &dev_attr_f_req.attr,
376         &dev_attr_ds_req.attr,
377         &dev_attr_rd_sect.attr,
378         &dev_attr_wr_sect.attr,
379         NULL
380 };
381
382 static const struct attribute_group xen_vbdstat_group = {
383         .name = "statistics",
384         .attrs = xen_vbdstat_attrs,
385 };
386
387 #define VBD_SHOW(name, format, args...)                                 \
388         static ssize_t show_##name(struct device *_dev,                 \
389                                    struct device_attribute *attr,       \
390                                    char *buf)                           \
391         {                                                               \
392                 struct xenbus_device *dev = to_xenbus_device(_dev);     \
393                 struct backend_info *be = dev_get_drvdata(&dev->dev);   \
394                                                                         \
395                 return sprintf(buf, format, ##args);                    \
396         }                                                               \
397         static DEVICE_ATTR(name, S_IRUGO, show_##name, NULL)
398
399 VBD_SHOW(physical_device, "%x:%x\n", be->major, be->minor);
400 VBD_SHOW(mode, "%s\n", be->mode);
401
402 static int xenvbd_sysfs_addif(struct xenbus_device *dev)
403 {
404         int error;
405
406         error = device_create_file(&dev->dev, &dev_attr_physical_device);
407         if (error)
408                 goto fail1;
409
410         error = device_create_file(&dev->dev, &dev_attr_mode);
411         if (error)
412                 goto fail2;
413
414         error = sysfs_create_group(&dev->dev.kobj, &xen_vbdstat_group);
415         if (error)
416                 goto fail3;
417
418         return 0;
419
420 fail3:  sysfs_remove_group(&dev->dev.kobj, &xen_vbdstat_group);
421 fail2:  device_remove_file(&dev->dev, &dev_attr_mode);
422 fail1:  device_remove_file(&dev->dev, &dev_attr_physical_device);
423         return error;
424 }
425
426 static void xenvbd_sysfs_delif(struct xenbus_device *dev)
427 {
428         sysfs_remove_group(&dev->dev.kobj, &xen_vbdstat_group);
429         device_remove_file(&dev->dev, &dev_attr_mode);
430         device_remove_file(&dev->dev, &dev_attr_physical_device);
431 }
432
433
434 static void xen_vbd_free(struct xen_vbd *vbd)
435 {
436         if (vbd->bdev)
437                 blkdev_put(vbd->bdev, vbd->readonly ? FMODE_READ : FMODE_WRITE);
438         vbd->bdev = NULL;
439 }
440
441 static int xen_vbd_create(struct xen_blkif *blkif, blkif_vdev_t handle,
442                           unsigned major, unsigned minor, int readonly,
443                           int cdrom)
444 {
445         struct xen_vbd *vbd;
446         struct block_device *bdev;
447         struct request_queue *q;
448
449         vbd = &blkif->vbd;
450         vbd->handle   = handle;
451         vbd->readonly = readonly;
452         vbd->type     = 0;
453
454         vbd->pdevice  = MKDEV(major, minor);
455
456         bdev = blkdev_get_by_dev(vbd->pdevice, vbd->readonly ?
457                                  FMODE_READ : FMODE_WRITE, NULL);
458
459         if (IS_ERR(bdev)) {
460                 pr_warn("xen_vbd_create: device %08x could not be opened\n",
461                         vbd->pdevice);
462                 return -ENOENT;
463         }
464
465         vbd->bdev = bdev;
466         if (vbd->bdev->bd_disk == NULL) {
467                 pr_warn("xen_vbd_create: device %08x doesn't exist\n",
468                         vbd->pdevice);
469                 xen_vbd_free(vbd);
470                 return -ENOENT;
471         }
472         vbd->size = vbd_sz(vbd);
473
474         if (vbd->bdev->bd_disk->flags & GENHD_FL_CD || cdrom)
475                 vbd->type |= VDISK_CDROM;
476         if (vbd->bdev->bd_disk->flags & GENHD_FL_REMOVABLE)
477                 vbd->type |= VDISK_REMOVABLE;
478
479         q = bdev_get_queue(bdev);
480         if (q && test_bit(QUEUE_FLAG_WC, &q->queue_flags))
481                 vbd->flush_support = true;
482
483         if (q && blk_queue_secure_erase(q))
484                 vbd->discard_secure = true;
485
486         pr_debug("Successful creation of handle=%04x (dom=%u)\n",
487                 handle, blkif->domid);
488         return 0;
489 }
490 static int xen_blkbk_remove(struct xenbus_device *dev)
491 {
492         struct backend_info *be = dev_get_drvdata(&dev->dev);
493
494         pr_debug("%s %p %d\n", __func__, dev, dev->otherend_id);
495
496         if (be->major || be->minor)
497                 xenvbd_sysfs_delif(dev);
498
499         if (be->backend_watch.node) {
500                 unregister_xenbus_watch(&be->backend_watch);
501                 kfree(be->backend_watch.node);
502                 be->backend_watch.node = NULL;
503         }
504
505         dev_set_drvdata(&dev->dev, NULL);
506
507         if (be->blkif)
508                 xen_blkif_disconnect(be->blkif);
509
510         /* Put the reference we set in xen_blkif_alloc(). */
511         xen_blkif_put(be->blkif);
512         kfree(be->mode);
513         kfree(be);
514         return 0;
515 }
516
517 int xen_blkbk_flush_diskcache(struct xenbus_transaction xbt,
518                               struct backend_info *be, int state)
519 {
520         struct xenbus_device *dev = be->dev;
521         int err;
522
523         err = xenbus_printf(xbt, dev->nodename, "feature-flush-cache",
524                             "%d", state);
525         if (err)
526                 dev_warn(&dev->dev, "writing feature-flush-cache (%d)", err);
527
528         return err;
529 }
530
531 static void xen_blkbk_discard(struct xenbus_transaction xbt, struct backend_info *be)
532 {
533         struct xenbus_device *dev = be->dev;
534         struct xen_blkif *blkif = be->blkif;
535         int err;
536         int state = 0, discard_enable;
537         struct block_device *bdev = be->blkif->vbd.bdev;
538         struct request_queue *q = bdev_get_queue(bdev);
539
540         err = xenbus_scanf(XBT_NIL, dev->nodename, "discard-enable", "%d",
541                            &discard_enable);
542         if (err == 1 && !discard_enable)
543                 return;
544
545         if (blk_queue_discard(q)) {
546                 err = xenbus_printf(xbt, dev->nodename,
547                         "discard-granularity", "%u",
548                         q->limits.discard_granularity);
549                 if (err) {
550                         dev_warn(&dev->dev, "writing discard-granularity (%d)", err);
551                         return;
552                 }
553                 err = xenbus_printf(xbt, dev->nodename,
554                         "discard-alignment", "%u",
555                         q->limits.discard_alignment);
556                 if (err) {
557                         dev_warn(&dev->dev, "writing discard-alignment (%d)", err);
558                         return;
559                 }
560                 state = 1;
561                 /* Optional. */
562                 err = xenbus_printf(xbt, dev->nodename,
563                                     "discard-secure", "%d",
564                                     blkif->vbd.discard_secure);
565                 if (err) {
566                         dev_warn(&dev->dev, "writing discard-secure (%d)", err);
567                         return;
568                 }
569         }
570         err = xenbus_printf(xbt, dev->nodename, "feature-discard",
571                             "%d", state);
572         if (err)
573                 dev_warn(&dev->dev, "writing feature-discard (%d)", err);
574 }
575 int xen_blkbk_barrier(struct xenbus_transaction xbt,
576                       struct backend_info *be, int state)
577 {
578         struct xenbus_device *dev = be->dev;
579         int err;
580
581         err = xenbus_printf(xbt, dev->nodename, "feature-barrier",
582                             "%d", state);
583         if (err)
584                 dev_warn(&dev->dev, "writing feature-barrier (%d)", err);
585
586         return err;
587 }
588
589 /*
590  * Entry point to this code when a new device is created.  Allocate the basic
591  * structures, and watch the store waiting for the hotplug scripts to tell us
592  * the device's physical major and minor numbers.  Switch to InitWait.
593  */
594 static int xen_blkbk_probe(struct xenbus_device *dev,
595                            const struct xenbus_device_id *id)
596 {
597         int err;
598         struct backend_info *be = kzalloc(sizeof(struct backend_info),
599                                           GFP_KERNEL);
600
601         /* match the pr_debug in xen_blkbk_remove */
602         pr_debug("%s %p %d\n", __func__, dev, dev->otherend_id);
603
604         if (!be) {
605                 xenbus_dev_fatal(dev, -ENOMEM,
606                                  "allocating backend structure");
607                 return -ENOMEM;
608         }
609         be->dev = dev;
610         dev_set_drvdata(&dev->dev, be);
611
612         be->blkif = xen_blkif_alloc(dev->otherend_id);
613         if (IS_ERR(be->blkif)) {
614                 err = PTR_ERR(be->blkif);
615                 be->blkif = NULL;
616                 xenbus_dev_fatal(dev, err, "creating block interface");
617                 goto fail;
618         }
619
620         err = xenbus_printf(XBT_NIL, dev->nodename,
621                             "feature-max-indirect-segments", "%u",
622                             MAX_INDIRECT_SEGMENTS);
623         if (err)
624                 dev_warn(&dev->dev,
625                          "writing %s/feature-max-indirect-segments (%d)",
626                          dev->nodename, err);
627
628         /* Multi-queue: advertise how many queues are supported by us.*/
629         err = xenbus_printf(XBT_NIL, dev->nodename,
630                             "multi-queue-max-queues", "%u", xenblk_max_queues);
631         if (err)
632                 pr_warn("Error writing multi-queue-max-queues\n");
633
634         /* setup back pointer */
635         be->blkif->be = be;
636
637         err = xenbus_watch_pathfmt(dev, &be->backend_watch, backend_changed,
638                                    "%s/%s", dev->nodename, "physical-device");
639         if (err)
640                 goto fail;
641
642         err = xenbus_printf(XBT_NIL, dev->nodename, "max-ring-page-order", "%u",
643                             xen_blkif_max_ring_order);
644         if (err)
645                 pr_warn("%s write out 'max-ring-page-order' failed\n", __func__);
646
647         err = xenbus_switch_state(dev, XenbusStateInitWait);
648         if (err)
649                 goto fail;
650
651         return 0;
652
653 fail:
654         pr_warn("%s failed\n", __func__);
655         xen_blkbk_remove(dev);
656         return err;
657 }
658
659
660 /*
661  * Callback received when the hotplug scripts have placed the physical-device
662  * node.  Read it and the mode node, and create a vbd.  If the frontend is
663  * ready, connect.
664  */
665 static void backend_changed(struct xenbus_watch *watch,
666                             const char **vec, unsigned int len)
667 {
668         int err;
669         unsigned major;
670         unsigned minor;
671         struct backend_info *be
672                 = container_of(watch, struct backend_info, backend_watch);
673         struct xenbus_device *dev = be->dev;
674         int cdrom = 0;
675         unsigned long handle;
676         char *device_type;
677
678         pr_debug("%s %p %d\n", __func__, dev, dev->otherend_id);
679
680         err = xenbus_scanf(XBT_NIL, dev->nodename, "physical-device", "%x:%x",
681                            &major, &minor);
682         if (XENBUS_EXIST_ERR(err)) {
683                 /*
684                  * Since this watch will fire once immediately after it is
685                  * registered, we expect this.  Ignore it, and wait for the
686                  * hotplug scripts.
687                  */
688                 return;
689         }
690         if (err != 2) {
691                 xenbus_dev_fatal(dev, err, "reading physical-device");
692                 return;
693         }
694
695         if (be->major | be->minor) {
696                 if (be->major != major || be->minor != minor)
697                         pr_warn("changing physical device (from %x:%x to %x:%x) not supported.\n",
698                                 be->major, be->minor, major, minor);
699                 return;
700         }
701
702         be->mode = xenbus_read(XBT_NIL, dev->nodename, "mode", NULL);
703         if (IS_ERR(be->mode)) {
704                 err = PTR_ERR(be->mode);
705                 be->mode = NULL;
706                 xenbus_dev_fatal(dev, err, "reading mode");
707                 return;
708         }
709
710         device_type = xenbus_read(XBT_NIL, dev->otherend, "device-type", NULL);
711         if (!IS_ERR(device_type)) {
712                 cdrom = strcmp(device_type, "cdrom") == 0;
713                 kfree(device_type);
714         }
715
716         /* Front end dir is a number, which is used as the handle. */
717         err = kstrtoul(strrchr(dev->otherend, '/') + 1, 0, &handle);
718         if (err) {
719                 kfree(be->mode);
720                 be->mode = NULL;
721                 return;
722         }
723
724         be->major = major;
725         be->minor = minor;
726
727         err = xen_vbd_create(be->blkif, handle, major, minor,
728                              !strchr(be->mode, 'w'), cdrom);
729
730         if (err)
731                 xenbus_dev_fatal(dev, err, "creating vbd structure");
732         else {
733                 err = xenvbd_sysfs_addif(dev);
734                 if (err) {
735                         xen_vbd_free(&be->blkif->vbd);
736                         xenbus_dev_fatal(dev, err, "creating sysfs entries");
737                 }
738         }
739
740         if (err) {
741                 kfree(be->mode);
742                 be->mode = NULL;
743                 be->major = 0;
744                 be->minor = 0;
745         } else {
746                 /* We're potentially connected now */
747                 xen_update_blkif_status(be->blkif);
748         }
749 }
750
751
752 /*
753  * Callback received when the frontend's state changes.
754  */
755 static void frontend_changed(struct xenbus_device *dev,
756                              enum xenbus_state frontend_state)
757 {
758         struct backend_info *be = dev_get_drvdata(&dev->dev);
759         int err;
760
761         pr_debug("%s %p %s\n", __func__, dev, xenbus_strstate(frontend_state));
762
763         switch (frontend_state) {
764         case XenbusStateInitialising:
765                 if (dev->state == XenbusStateClosed) {
766                         pr_info("%s: prepare for reconnect\n", dev->nodename);
767                         xenbus_switch_state(dev, XenbusStateInitWait);
768                 }
769                 break;
770
771         case XenbusStateInitialised:
772         case XenbusStateConnected:
773                 /*
774                  * Ensure we connect even when two watches fire in
775                  * close succession and we miss the intermediate value
776                  * of frontend_state.
777                  */
778                 if (dev->state == XenbusStateConnected)
779                         break;
780
781                 /*
782                  * Enforce precondition before potential leak point.
783                  * xen_blkif_disconnect() is idempotent.
784                  */
785                 err = xen_blkif_disconnect(be->blkif);
786                 if (err) {
787                         xenbus_dev_fatal(dev, err, "pending I/O");
788                         break;
789                 }
790
791                 err = connect_ring(be);
792                 if (err) {
793                         /*
794                          * Clean up so that memory resources can be used by
795                          * other devices. connect_ring reported already error.
796                          */
797                         xen_blkif_disconnect(be->blkif);
798                         break;
799                 }
800                 xen_update_blkif_status(be->blkif);
801                 break;
802
803         case XenbusStateClosing:
804                 xenbus_switch_state(dev, XenbusStateClosing);
805                 break;
806
807         case XenbusStateClosed:
808                 xen_blkif_disconnect(be->blkif);
809                 xenbus_switch_state(dev, XenbusStateClosed);
810                 if (xenbus_dev_is_online(dev))
811                         break;
812                 /* fall through if not online */
813         case XenbusStateUnknown:
814                 /* implies xen_blkif_disconnect() via xen_blkbk_remove() */
815                 device_unregister(&dev->dev);
816                 break;
817
818         default:
819                 xenbus_dev_fatal(dev, -EINVAL, "saw state %d at frontend",
820                                  frontend_state);
821                 break;
822         }
823 }
824
825
826 /* ** Connection ** */
827
828
829 /*
830  * Write the physical details regarding the block device to the store, and
831  * switch to Connected state.
832  */
833 static void connect(struct backend_info *be)
834 {
835         struct xenbus_transaction xbt;
836         int err;
837         struct xenbus_device *dev = be->dev;
838
839         pr_debug("%s %s\n", __func__, dev->otherend);
840
841         /* Supply the information about the device the frontend needs */
842 again:
843         err = xenbus_transaction_start(&xbt);
844         if (err) {
845                 xenbus_dev_fatal(dev, err, "starting transaction");
846                 return;
847         }
848
849         /* If we can't advertise it is OK. */
850         xen_blkbk_flush_diskcache(xbt, be, be->blkif->vbd.flush_support);
851
852         xen_blkbk_discard(xbt, be);
853
854         xen_blkbk_barrier(xbt, be, be->blkif->vbd.flush_support);
855
856         err = xenbus_printf(xbt, dev->nodename, "feature-persistent", "%u", 1);
857         if (err) {
858                 xenbus_dev_fatal(dev, err, "writing %s/feature-persistent",
859                                  dev->nodename);
860                 goto abort;
861         }
862
863         err = xenbus_printf(xbt, dev->nodename, "sectors", "%llu",
864                             (unsigned long long)vbd_sz(&be->blkif->vbd));
865         if (err) {
866                 xenbus_dev_fatal(dev, err, "writing %s/sectors",
867                                  dev->nodename);
868                 goto abort;
869         }
870
871         /* FIXME: use a typename instead */
872         err = xenbus_printf(xbt, dev->nodename, "info", "%u",
873                             be->blkif->vbd.type |
874                             (be->blkif->vbd.readonly ? VDISK_READONLY : 0));
875         if (err) {
876                 xenbus_dev_fatal(dev, err, "writing %s/info",
877                                  dev->nodename);
878                 goto abort;
879         }
880         err = xenbus_printf(xbt, dev->nodename, "sector-size", "%lu",
881                             (unsigned long)
882                             bdev_logical_block_size(be->blkif->vbd.bdev));
883         if (err) {
884                 xenbus_dev_fatal(dev, err, "writing %s/sector-size",
885                                  dev->nodename);
886                 goto abort;
887         }
888         err = xenbus_printf(xbt, dev->nodename, "physical-sector-size", "%u",
889                             bdev_physical_block_size(be->blkif->vbd.bdev));
890         if (err)
891                 xenbus_dev_error(dev, err, "writing %s/physical-sector-size",
892                                  dev->nodename);
893
894         err = xenbus_transaction_end(xbt, 0);
895         if (err == -EAGAIN)
896                 goto again;
897         if (err)
898                 xenbus_dev_fatal(dev, err, "ending transaction");
899
900         err = xenbus_switch_state(dev, XenbusStateConnected);
901         if (err)
902                 xenbus_dev_fatal(dev, err, "%s: switching to Connected state",
903                                  dev->nodename);
904
905         return;
906  abort:
907         xenbus_transaction_end(xbt, 1);
908 }
909
910 /*
911  * Each ring may have multi pages, depends on "ring-page-order".
912  */
913 static int read_per_ring_refs(struct xen_blkif_ring *ring, const char *dir)
914 {
915         unsigned int ring_ref[XENBUS_MAX_RING_GRANTS];
916         struct pending_req *req, *n;
917         int err, i, j;
918         struct xen_blkif *blkif = ring->blkif;
919         struct xenbus_device *dev = blkif->be->dev;
920         unsigned int ring_page_order, nr_grefs, evtchn;
921
922         err = xenbus_scanf(XBT_NIL, dir, "event-channel", "%u",
923                           &evtchn);
924         if (err != 1) {
925                 err = -EINVAL;
926                 xenbus_dev_fatal(dev, err, "reading %s/event-channel", dir);
927                 return err;
928         }
929
930         err = xenbus_scanf(XBT_NIL, dev->otherend, "ring-page-order", "%u",
931                           &ring_page_order);
932         if (err != 1) {
933                 err = xenbus_scanf(XBT_NIL, dir, "ring-ref", "%u", &ring_ref[0]);
934                 if (err != 1) {
935                         err = -EINVAL;
936                         xenbus_dev_fatal(dev, err, "reading %s/ring-ref", dir);
937                         return err;
938                 }
939                 nr_grefs = 1;
940         } else {
941                 unsigned int i;
942
943                 if (ring_page_order > xen_blkif_max_ring_order) {
944                         err = -EINVAL;
945                         xenbus_dev_fatal(dev, err, "%s/request %d ring page order exceed max:%d",
946                                          dir, ring_page_order,
947                                          xen_blkif_max_ring_order);
948                         return err;
949                 }
950
951                 nr_grefs = 1 << ring_page_order;
952                 for (i = 0; i < nr_grefs; i++) {
953                         char ring_ref_name[RINGREF_NAME_LEN];
954
955                         snprintf(ring_ref_name, RINGREF_NAME_LEN, "ring-ref%u", i);
956                         err = xenbus_scanf(XBT_NIL, dir, ring_ref_name,
957                                            "%u", &ring_ref[i]);
958                         if (err != 1) {
959                                 err = -EINVAL;
960                                 xenbus_dev_fatal(dev, err, "reading %s/%s",
961                                                  dir, ring_ref_name);
962                                 return err;
963                         }
964                 }
965         }
966         blkif->nr_ring_pages = nr_grefs;
967
968         for (i = 0; i < nr_grefs * XEN_BLKIF_REQS_PER_PAGE; i++) {
969                 req = kzalloc(sizeof(*req), GFP_KERNEL);
970                 if (!req)
971                         goto fail;
972                 list_add_tail(&req->free_list, &ring->pending_free);
973                 for (j = 0; j < MAX_INDIRECT_SEGMENTS; j++) {
974                         req->segments[j] = kzalloc(sizeof(*req->segments[0]), GFP_KERNEL);
975                         if (!req->segments[j])
976                                 goto fail;
977                 }
978                 for (j = 0; j < MAX_INDIRECT_PAGES; j++) {
979                         req->indirect_pages[j] = kzalloc(sizeof(*req->indirect_pages[0]),
980                                                          GFP_KERNEL);
981                         if (!req->indirect_pages[j])
982                                 goto fail;
983                 }
984         }
985
986         /* Map the shared frame, irq etc. */
987         err = xen_blkif_map(ring, ring_ref, nr_grefs, evtchn);
988         if (err) {
989                 xenbus_dev_fatal(dev, err, "mapping ring-ref port %u", evtchn);
990                 return err;
991         }
992
993         return 0;
994
995 fail:
996         list_for_each_entry_safe(req, n, &ring->pending_free, free_list) {
997                 list_del(&req->free_list);
998                 for (j = 0; j < MAX_INDIRECT_SEGMENTS; j++) {
999                         if (!req->segments[j])
1000                                 break;
1001                         kfree(req->segments[j]);
1002                 }
1003                 for (j = 0; j < MAX_INDIRECT_PAGES; j++) {
1004                         if (!req->indirect_pages[j])
1005                                 break;
1006                         kfree(req->indirect_pages[j]);
1007                 }
1008                 kfree(req);
1009         }
1010         return -ENOMEM;
1011
1012 }
1013
1014 static int connect_ring(struct backend_info *be)
1015 {
1016         struct xenbus_device *dev = be->dev;
1017         unsigned int pers_grants;
1018         char protocol[64] = "";
1019         int err, i;
1020         char *xspath;
1021         size_t xspathsize;
1022         const size_t xenstore_path_ext_size = 11; /* sufficient for "/queue-NNN" */
1023         unsigned int requested_num_queues = 0;
1024
1025         pr_debug("%s %s\n", __func__, dev->otherend);
1026
1027         be->blkif->blk_protocol = BLKIF_PROTOCOL_DEFAULT;
1028         err = xenbus_scanf(XBT_NIL, dev->otherend, "protocol",
1029                            "%63s", protocol);
1030         if (err <= 0)
1031                 strcpy(protocol, "unspecified, assuming default");
1032         else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_NATIVE))
1033                 be->blkif->blk_protocol = BLKIF_PROTOCOL_NATIVE;
1034         else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_32))
1035                 be->blkif->blk_protocol = BLKIF_PROTOCOL_X86_32;
1036         else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_64))
1037                 be->blkif->blk_protocol = BLKIF_PROTOCOL_X86_64;
1038         else {
1039                 xenbus_dev_fatal(dev, err, "unknown fe protocol %s", protocol);
1040                 return -ENOSYS;
1041         }
1042         err = xenbus_scanf(XBT_NIL, dev->otherend,
1043                            "feature-persistent", "%u", &pers_grants);
1044         if (err <= 0)
1045                 pers_grants = 0;
1046
1047         be->blkif->vbd.feature_gnt_persistent = pers_grants;
1048         be->blkif->vbd.overflow_max_grants = 0;
1049
1050         /*
1051          * Read the number of hardware queues from frontend.
1052          */
1053         err = xenbus_scanf(XBT_NIL, dev->otherend, "multi-queue-num-queues",
1054                            "%u", &requested_num_queues);
1055         if (err < 0) {
1056                 requested_num_queues = 1;
1057         } else {
1058                 if (requested_num_queues > xenblk_max_queues
1059                     || requested_num_queues == 0) {
1060                         /* Buggy or malicious guest. */
1061                         xenbus_dev_fatal(dev, err,
1062                                         "guest requested %u queues, exceeding the maximum of %u.",
1063                                         requested_num_queues, xenblk_max_queues);
1064                         return -ENOSYS;
1065                 }
1066         }
1067         be->blkif->nr_rings = requested_num_queues;
1068         if (xen_blkif_alloc_rings(be->blkif))
1069                 return -ENOMEM;
1070
1071         pr_info("%s: using %d queues, protocol %d (%s) %s\n", dev->nodename,
1072                  be->blkif->nr_rings, be->blkif->blk_protocol, protocol,
1073                  pers_grants ? "persistent grants" : "");
1074
1075         if (be->blkif->nr_rings == 1)
1076                 return read_per_ring_refs(&be->blkif->rings[0], dev->otherend);
1077         else {
1078                 xspathsize = strlen(dev->otherend) + xenstore_path_ext_size;
1079                 xspath = kmalloc(xspathsize, GFP_KERNEL);
1080                 if (!xspath) {
1081                         xenbus_dev_fatal(dev, -ENOMEM, "reading ring references");
1082                         return -ENOMEM;
1083                 }
1084
1085                 for (i = 0; i < be->blkif->nr_rings; i++) {
1086                         memset(xspath, 0, xspathsize);
1087                         snprintf(xspath, xspathsize, "%s/queue-%u", dev->otherend, i);
1088                         err = read_per_ring_refs(&be->blkif->rings[i], xspath);
1089                         if (err) {
1090                                 kfree(xspath);
1091                                 return err;
1092                         }
1093                 }
1094                 kfree(xspath);
1095         }
1096         return 0;
1097 }
1098
1099 static const struct xenbus_device_id xen_blkbk_ids[] = {
1100         { "vbd" },
1101         { "" }
1102 };
1103
1104 static struct xenbus_driver xen_blkbk_driver = {
1105         .ids  = xen_blkbk_ids,
1106         .probe = xen_blkbk_probe,
1107         .remove = xen_blkbk_remove,
1108         .otherend_changed = frontend_changed
1109 };
1110
1111 int xen_blkif_xenbus_init(void)
1112 {
1113         return xenbus_register_backend(&xen_blkbk_driver);
1114 }