1// SPDX-License-Identifier: GPL-2.0-or-later
2/* Xenbus code for blkif backend
3 Copyright (C) 2005 Rusty Russell <rusty@rustcorp.com.au>
4 Copyright (C) 2005 XenSource Ltd
5
6
7*/
8
9#define pr_fmt(fmt) "xen-blkback: " fmt
10
11#include <linux/module.h>
12#include <linux/kthread.h>
13#include <linux/pagemap.h>
14#include <xen/events.h>
15#include <xen/grant_table.h>
16#include "common.h"
17
18/* On the XenBus the max length of 'ring-ref%u'. */
19#define RINGREF_NAME_LEN (20)
20
21struct backend_info {
22 struct xenbus_device *dev;
23 struct xen_blkif *blkif;
24 struct xenbus_watch backend_watch;
25 unsigned major;
26 unsigned minor;
27 char *mode;
28};
29
30static struct kmem_cache *xen_blkif_cachep;
31static void connect(struct backend_info *);
32static int connect_ring(struct backend_info *);
33static void backend_changed(struct xenbus_watch *, const char *,
34 const char *);
35static void xen_blkif_free(struct xen_blkif *blkif);
36static void xen_vbd_free(struct xen_vbd *vbd);
37
38struct xenbus_device *xen_blkbk_xenbus(struct backend_info *be)
39{
40 return be->dev;
41}
42
43/*
44 * The last request could free the device from softirq context and
45 * xen_blkif_free() can sleep.
46 */
47static void xen_blkif_deferred_free(struct work_struct *work)
48{
49 struct xen_blkif *blkif;
50
51 blkif = container_of(work, struct xen_blkif, free_work);
52 xen_blkif_free(blkif);
53}
54
55static int blkback_name(struct xen_blkif *blkif, char *buf)
56{
57 char *devpath, *devname;
58 struct xenbus_device *dev = blkif->be->dev;
59
60 devpath = xenbus_read(XBT_NIL, dir: dev->nodename, node: "dev", NULL);
61 if (IS_ERR(devpath))
62 return PTR_ERR(devpath);
63
64 devname = strstr(devpath, "/dev/");
65 if (devname != NULL)
66 devname += strlen("/dev/");
67 else
68 devname = devpath;
69
70 snprintf(buf, TASK_COMM_LEN, "%d.%s", blkif->domid, devname);
71 kfree(devpath);
72
73 return 0;
74}
75
76static void xen_update_blkif_status(struct xen_blkif *blkif)
77{
78 int err;
79 char name[TASK_COMM_LEN];
80 struct xen_blkif_ring *ring;
81 int i;
82
83 /* Not ready to connect? */
84 if (!blkif->rings || !blkif->rings[0].irq || !blkif->vbd.bdev_file)
85 return;
86
87 /* Already connected? */
88 if (blkif->be->dev->state == XenbusStateConnected)
89 return;
90
91 /* Attempt to connect: exit if we fail to. */
92 connect(blkif->be);
93 if (blkif->be->dev->state != XenbusStateConnected)
94 return;
95
96 err = blkback_name(blkif, buf: name);
97 if (err) {
98 xenbus_dev_error(dev: blkif->be->dev, err, fmt: "get blkback dev name");
99 return;
100 }
101
102 err = sync_blockdev(bdev: file_bdev(bdev_file: blkif->vbd.bdev_file));
103 if (err) {
104 xenbus_dev_error(dev: blkif->be->dev, err, fmt: "block flush");
105 return;
106 }
107 invalidate_inode_pages2(mapping: blkif->vbd.bdev_file->f_mapping);
108
109 for (i = 0; i < blkif->nr_rings; i++) {
110 ring = &blkif->rings[i];
111 ring->xenblkd = kthread_run(xen_blkif_schedule, ring, "%s-%d", name, i);
112 if (IS_ERR(ptr: ring->xenblkd)) {
113 err = PTR_ERR(ptr: ring->xenblkd);
114 ring->xenblkd = NULL;
115 xenbus_dev_fatal(dev: blkif->be->dev, err,
116 fmt: "start %s-%d xenblkd", name, i);
117 goto out;
118 }
119 }
120 return;
121
122out:
123 while (--i >= 0) {
124 ring = &blkif->rings[i];
125 kthread_stop(k: ring->xenblkd);
126 }
127 return;
128}
129
130static int xen_blkif_alloc_rings(struct xen_blkif *blkif)
131{
132 unsigned int r;
133
134 blkif->rings = kcalloc(n: blkif->nr_rings, size: sizeof(struct xen_blkif_ring),
135 GFP_KERNEL);
136 if (!blkif->rings)
137 return -ENOMEM;
138
139 for (r = 0; r < blkif->nr_rings; r++) {
140 struct xen_blkif_ring *ring = &blkif->rings[r];
141
142 spin_lock_init(&ring->blk_ring_lock);
143 init_waitqueue_head(&ring->wq);
144 INIT_LIST_HEAD(list: &ring->pending_free);
145 INIT_LIST_HEAD(list: &ring->persistent_purge_list);
146 INIT_WORK(&ring->persistent_purge_work, xen_blkbk_unmap_purged_grants);
147 gnttab_page_cache_init(cache: &ring->free_pages);
148
149 spin_lock_init(&ring->pending_free_lock);
150 init_waitqueue_head(&ring->pending_free_wq);
151 init_waitqueue_head(&ring->shutdown_wq);
152 ring->blkif = blkif;
153 ring->st_print = jiffies;
154 ring->active = true;
155 }
156
157 return 0;
158}
159
160/* Enable the persistent grants feature. */
161static bool feature_persistent = true;
162module_param(feature_persistent, bool, 0644);
163MODULE_PARM_DESC(feature_persistent, "Enables the persistent grants feature");
164
165static struct xen_blkif *xen_blkif_alloc(domid_t domid)
166{
167 struct xen_blkif *blkif;
168
169 BUILD_BUG_ON(MAX_INDIRECT_PAGES > BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST);
170
171 blkif = kmem_cache_zalloc(k: xen_blkif_cachep, GFP_KERNEL);
172 if (!blkif)
173 return ERR_PTR(error: -ENOMEM);
174
175 blkif->domid = domid;
176 atomic_set(v: &blkif->refcnt, i: 1);
177 init_completion(x: &blkif->drain_complete);
178
179 /*
180 * Because freeing back to the cache may be deferred, it is not
181 * safe to unload the module (and hence destroy the cache) until
182 * this has completed. To prevent premature unloading, take an
183 * extra module reference here and release only when the object
184 * has been freed back to the cache.
185 */
186 __module_get(THIS_MODULE);
187 INIT_WORK(&blkif->free_work, xen_blkif_deferred_free);
188
189 return blkif;
190}
191
192static int xen_blkif_map(struct xen_blkif_ring *ring, grant_ref_t *gref,
193 unsigned int nr_grefs, unsigned int evtchn)
194{
195 int err;
196 struct xen_blkif *blkif = ring->blkif;
197 const struct blkif_common_sring *sring_common;
198 RING_IDX rsp_prod, req_prod;
199 unsigned int size;
200
201 /* Already connected through? */
202 if (ring->irq)
203 return 0;
204
205 err = xenbus_map_ring_valloc(dev: blkif->be->dev, gnt_refs: gref, nr_grefs,
206 vaddr: &ring->blk_ring);
207 if (err < 0)
208 return err;
209
210 sring_common = (struct blkif_common_sring *)ring->blk_ring;
211 rsp_prod = READ_ONCE(sring_common->rsp_prod);
212 req_prod = READ_ONCE(sring_common->req_prod);
213
214 switch (blkif->blk_protocol) {
215 case BLKIF_PROTOCOL_NATIVE:
216 {
217 struct blkif_sring *sring_native =
218 (struct blkif_sring *)ring->blk_ring;
219
220 BACK_RING_ATTACH(&ring->blk_rings.native, sring_native,
221 rsp_prod, XEN_PAGE_SIZE * nr_grefs);
222 size = __RING_SIZE(sring_native, XEN_PAGE_SIZE * nr_grefs);
223 break;
224 }
225 case BLKIF_PROTOCOL_X86_32:
226 {
227 struct blkif_x86_32_sring *sring_x86_32 =
228 (struct blkif_x86_32_sring *)ring->blk_ring;
229
230 BACK_RING_ATTACH(&ring->blk_rings.x86_32, sring_x86_32,
231 rsp_prod, XEN_PAGE_SIZE * nr_grefs);
232 size = __RING_SIZE(sring_x86_32, XEN_PAGE_SIZE * nr_grefs);
233 break;
234 }
235 case BLKIF_PROTOCOL_X86_64:
236 {
237 struct blkif_x86_64_sring *sring_x86_64 =
238 (struct blkif_x86_64_sring *)ring->blk_ring;
239
240 BACK_RING_ATTACH(&ring->blk_rings.x86_64, sring_x86_64,
241 rsp_prod, XEN_PAGE_SIZE * nr_grefs);
242 size = __RING_SIZE(sring_x86_64, XEN_PAGE_SIZE * nr_grefs);
243 break;
244 }
245 default:
246 BUG();
247 }
248
249 err = -EIO;
250 if (req_prod - rsp_prod > size)
251 goto fail;
252
253 err = bind_interdomain_evtchn_to_irqhandler_lateeoi(dev: blkif->be->dev,
254 remote_port: evtchn, handler: xen_blkif_be_int, irqflags: 0, devname: "blkif-backend", dev_id: ring);
255 if (err < 0)
256 goto fail;
257 ring->irq = err;
258
259 return 0;
260
261fail:
262 xenbus_unmap_ring_vfree(dev: blkif->be->dev, vaddr: ring->blk_ring);
263 ring->blk_rings.common.sring = NULL;
264 return err;
265}
266
267static int xen_blkif_disconnect(struct xen_blkif *blkif)
268{
269 struct pending_req *req, *n;
270 unsigned int j, r;
271 bool busy = false;
272
273 for (r = 0; r < blkif->nr_rings; r++) {
274 struct xen_blkif_ring *ring = &blkif->rings[r];
275 unsigned int i = 0;
276
277 if (!ring->active)
278 continue;
279
280 if (ring->xenblkd) {
281 kthread_stop(k: ring->xenblkd);
282 ring->xenblkd = NULL;
283 wake_up(&ring->shutdown_wq);
284 }
285
286 /* The above kthread_stop() guarantees that at this point we
287 * don't have any discard_io or other_io requests. So, checking
288 * for inflight IO is enough.
289 */
290 if (atomic_read(v: &ring->inflight) > 0) {
291 busy = true;
292 continue;
293 }
294
295 if (ring->irq) {
296 unbind_from_irqhandler(irq: ring->irq, dev_id: ring);
297 ring->irq = 0;
298 }
299
300 if (ring->blk_rings.common.sring) {
301 xenbus_unmap_ring_vfree(dev: blkif->be->dev, vaddr: ring->blk_ring);
302 ring->blk_rings.common.sring = NULL;
303 }
304
305 /* Remove all persistent grants and the cache of ballooned pages. */
306 xen_blkbk_free_caches(ring);
307
308 /* Check that there is no request in use */
309 list_for_each_entry_safe(req, n, &ring->pending_free, free_list) {
310 list_del(entry: &req->free_list);
311
312 for (j = 0; j < MAX_INDIRECT_SEGMENTS; j++)
313 kfree(objp: req->segments[j]);
314
315 for (j = 0; j < MAX_INDIRECT_PAGES; j++)
316 kfree(objp: req->indirect_pages[j]);
317
318 kfree(objp: req);
319 i++;
320 }
321
322 BUG_ON(atomic_read(&ring->persistent_gnt_in_use) != 0);
323 BUG_ON(!list_empty(&ring->persistent_purge_list));
324 BUG_ON(!RB_EMPTY_ROOT(&ring->persistent_gnts));
325 BUG_ON(ring->free_pages.num_pages != 0);
326 BUG_ON(ring->persistent_gnt_c != 0);
327 WARN_ON(i != (XEN_BLKIF_REQS_PER_PAGE * blkif->nr_ring_pages));
328 ring->active = false;
329 }
330 if (busy)
331 return -EBUSY;
332
333 blkif->nr_ring_pages = 0;
334 /*
335 * blkif->rings was allocated in connect_ring, so we should free it in
336 * here.
337 */
338 kfree(objp: blkif->rings);
339 blkif->rings = NULL;
340 blkif->nr_rings = 0;
341
342 return 0;
343}
344
345static void xen_blkif_free(struct xen_blkif *blkif)
346{
347 WARN_ON(xen_blkif_disconnect(blkif));
348 xen_vbd_free(vbd: &blkif->vbd);
349 kfree(objp: blkif->be->mode);
350 kfree(objp: blkif->be);
351
352 /* Make sure everything is drained before shutting down */
353 kmem_cache_free(s: xen_blkif_cachep, objp: blkif);
354 module_put(THIS_MODULE);
355}
356
357int __init xen_blkif_interface_init(void)
358{
359 xen_blkif_cachep = kmem_cache_create(name: "blkif_cache",
360 size: sizeof(struct xen_blkif),
361 align: 0, flags: 0, NULL);
362 if (!xen_blkif_cachep)
363 return -ENOMEM;
364
365 return 0;
366}
367
368void xen_blkif_interface_fini(void)
369{
370 kmem_cache_destroy(s: xen_blkif_cachep);
371 xen_blkif_cachep = NULL;
372}
373
374/*
375 * sysfs interface for VBD I/O requests
376 */
377
378#define VBD_SHOW_ALLRING(name, format) \
379 static ssize_t show_##name(struct device *_dev, \
380 struct device_attribute *attr, \
381 char *buf) \
382 { \
383 struct xenbus_device *dev = to_xenbus_device(_dev); \
384 struct backend_info *be = dev_get_drvdata(&dev->dev); \
385 struct xen_blkif *blkif = be->blkif; \
386 unsigned int i; \
387 unsigned long long result = 0; \
388 \
389 if (!blkif->rings) \
390 goto out; \
391 \
392 for (i = 0; i < blkif->nr_rings; i++) { \
393 struct xen_blkif_ring *ring = &blkif->rings[i]; \
394 \
395 result += ring->st_##name; \
396 } \
397 \
398out: \
399 return sprintf(buf, format, result); \
400 } \
401 static DEVICE_ATTR(name, 0444, show_##name, NULL)
402
403VBD_SHOW_ALLRING(oo_req, "%llu\n");
404VBD_SHOW_ALLRING(rd_req, "%llu\n");
405VBD_SHOW_ALLRING(wr_req, "%llu\n");
406VBD_SHOW_ALLRING(f_req, "%llu\n");
407VBD_SHOW_ALLRING(ds_req, "%llu\n");
408VBD_SHOW_ALLRING(rd_sect, "%llu\n");
409VBD_SHOW_ALLRING(wr_sect, "%llu\n");
410
411static struct attribute *xen_vbdstat_attrs[] = {
412 &dev_attr_oo_req.attr,
413 &dev_attr_rd_req.attr,
414 &dev_attr_wr_req.attr,
415 &dev_attr_f_req.attr,
416 &dev_attr_ds_req.attr,
417 &dev_attr_rd_sect.attr,
418 &dev_attr_wr_sect.attr,
419 NULL
420};
421
422static const struct attribute_group xen_vbdstat_group = {
423 .name = "statistics",
424 .attrs = xen_vbdstat_attrs,
425};
426
427#define VBD_SHOW(name, format, args...) \
428 static ssize_t show_##name(struct device *_dev, \
429 struct device_attribute *attr, \
430 char *buf) \
431 { \
432 struct xenbus_device *dev = to_xenbus_device(_dev); \
433 struct backend_info *be = dev_get_drvdata(&dev->dev); \
434 \
435 return sprintf(buf, format, ##args); \
436 } \
437 static DEVICE_ATTR(name, 0444, show_##name, NULL)
438
439VBD_SHOW(physical_device, "%x:%x\n", be->major, be->minor);
440VBD_SHOW(mode, "%s\n", be->mode);
441
442static int xenvbd_sysfs_addif(struct xenbus_device *dev)
443{
444 int error;
445
446 error = device_create_file(device: &dev->dev, entry: &dev_attr_physical_device);
447 if (error)
448 goto fail1;
449
450 error = device_create_file(device: &dev->dev, entry: &dev_attr_mode);
451 if (error)
452 goto fail2;
453
454 error = sysfs_create_group(kobj: &dev->dev.kobj, grp: &xen_vbdstat_group);
455 if (error)
456 goto fail3;
457
458 return 0;
459
460fail3: sysfs_remove_group(kobj: &dev->dev.kobj, grp: &xen_vbdstat_group);
461fail2: device_remove_file(dev: &dev->dev, attr: &dev_attr_mode);
462fail1: device_remove_file(dev: &dev->dev, attr: &dev_attr_physical_device);
463 return error;
464}
465
466static void xenvbd_sysfs_delif(struct xenbus_device *dev)
467{
468 sysfs_remove_group(kobj: &dev->dev.kobj, grp: &xen_vbdstat_group);
469 device_remove_file(dev: &dev->dev, attr: &dev_attr_mode);
470 device_remove_file(dev: &dev->dev, attr: &dev_attr_physical_device);
471}
472
473static void xen_vbd_free(struct xen_vbd *vbd)
474{
475 if (vbd->bdev_file)
476 fput(vbd->bdev_file);
477 vbd->bdev_file = NULL;
478}
479
480static int xen_vbd_create(struct xen_blkif *blkif, blkif_vdev_t handle,
481 unsigned major, unsigned minor, int readonly,
482 int cdrom)
483{
484 struct xen_vbd *vbd;
485 struct file *bdev_file;
486
487 vbd = &blkif->vbd;
488 vbd->handle = handle;
489 vbd->readonly = readonly;
490 vbd->type = 0;
491
492 vbd->pdevice = MKDEV(major, minor);
493
494 bdev_file = bdev_file_open_by_dev(dev: vbd->pdevice, mode: vbd->readonly ?
495 BLK_OPEN_READ : BLK_OPEN_WRITE, NULL, NULL);
496
497 if (IS_ERR(ptr: bdev_file)) {
498 pr_warn("xen_vbd_create: device %08x could not be opened\n",
499 vbd->pdevice);
500 return -ENOENT;
501 }
502
503 vbd->bdev_file = bdev_file;
504 if (file_bdev(bdev_file: vbd->bdev_file)->bd_disk == NULL) {
505 pr_warn("xen_vbd_create: device %08x doesn't exist\n",
506 vbd->pdevice);
507 xen_vbd_free(vbd);
508 return -ENOENT;
509 }
510 vbd->size = vbd_sz(vbd);
511
512 if (cdrom || disk_to_cdi(file_bdev(vbd->bdev_file)->bd_disk))
513 vbd->type |= VDISK_CDROM;
514 if (file_bdev(bdev_file: vbd->bdev_file)->bd_disk->flags & GENHD_FL_REMOVABLE)
515 vbd->type |= VDISK_REMOVABLE;
516
517 if (bdev_write_cache(bdev: file_bdev(bdev_file)))
518 vbd->flush_support = true;
519 if (bdev_max_secure_erase_sectors(bdev: file_bdev(bdev_file)))
520 vbd->discard_secure = true;
521
522 pr_debug("Successful creation of handle=%04x (dom=%u)\n",
523 handle, blkif->domid);
524 return 0;
525}
526
527static void xen_blkbk_remove(struct xenbus_device *dev)
528{
529 struct backend_info *be = dev_get_drvdata(dev: &dev->dev);
530
531 pr_debug("%s %p %d\n", __func__, dev, dev->otherend_id);
532
533 if (be->major || be->minor)
534 xenvbd_sysfs_delif(dev);
535
536 if (be->backend_watch.node) {
537 unregister_xenbus_watch(watch: &be->backend_watch);
538 kfree(objp: be->backend_watch.node);
539 be->backend_watch.node = NULL;
540 }
541
542 dev_set_drvdata(dev: &dev->dev, NULL);
543
544 if (be->blkif) {
545 xen_blkif_disconnect(blkif: be->blkif);
546
547 /* Put the reference we set in xen_blkif_alloc(). */
548 xen_blkif_put(be->blkif);
549 }
550}
551
552int xen_blkbk_flush_diskcache(struct xenbus_transaction xbt,
553 struct backend_info *be, int state)
554{
555 struct xenbus_device *dev = be->dev;
556 int err;
557
558 err = xenbus_printf(t: xbt, dir: dev->nodename, node: "feature-flush-cache",
559 fmt: "%d", state);
560 if (err)
561 dev_warn(&dev->dev, "writing feature-flush-cache (%d)", err);
562
563 return err;
564}
565
566static void xen_blkbk_discard(struct xenbus_transaction xbt, struct backend_info *be)
567{
568 struct xenbus_device *dev = be->dev;
569 struct xen_blkif *blkif = be->blkif;
570 int err;
571 int state = 0;
572 struct block_device *bdev = file_bdev(bdev_file: be->blkif->vbd.bdev_file);
573
574 if (!xenbus_read_unsigned(dir: dev->nodename, node: "discard-enable", default_val: 1))
575 return;
576
577 if (bdev_max_discard_sectors(bdev)) {
578 err = xenbus_printf(t: xbt, dir: dev->nodename,
579 node: "discard-granularity", fmt: "%u",
580 bdev_discard_granularity(bdev));
581 if (err) {
582 dev_warn(&dev->dev, "writing discard-granularity (%d)", err);
583 return;
584 }
585 err = xenbus_printf(t: xbt, dir: dev->nodename,
586 node: "discard-alignment", fmt: "%u",
587 bdev_discard_alignment(bdev));
588 if (err) {
589 dev_warn(&dev->dev, "writing discard-alignment (%d)", err);
590 return;
591 }
592 state = 1;
593 /* Optional. */
594 err = xenbus_printf(t: xbt, dir: dev->nodename,
595 node: "discard-secure", fmt: "%d",
596 blkif->vbd.discard_secure);
597 if (err) {
598 dev_warn(&dev->dev, "writing discard-secure (%d)", err);
599 return;
600 }
601 }
602 err = xenbus_printf(t: xbt, dir: dev->nodename, node: "feature-discard",
603 fmt: "%d", state);
604 if (err)
605 dev_warn(&dev->dev, "writing feature-discard (%d)", err);
606}
607
608int xen_blkbk_barrier(struct xenbus_transaction xbt,
609 struct backend_info *be, int state)
610{
611 struct xenbus_device *dev = be->dev;
612 int err;
613
614 err = xenbus_printf(t: xbt, dir: dev->nodename, node: "feature-barrier",
615 fmt: "%d", state);
616 if (err)
617 dev_warn(&dev->dev, "writing feature-barrier (%d)", err);
618
619 return err;
620}
621
622/*
623 * Entry point to this code when a new device is created. Allocate the basic
624 * structures, and watch the store waiting for the hotplug scripts to tell us
625 * the device's physical major and minor numbers. Switch to InitWait.
626 */
627static int xen_blkbk_probe(struct xenbus_device *dev,
628 const struct xenbus_device_id *id)
629{
630 int err;
631 struct backend_info *be = kzalloc(size: sizeof(struct backend_info),
632 GFP_KERNEL);
633
634 /* match the pr_debug in xen_blkbk_remove */
635 pr_debug("%s %p %d\n", __func__, dev, dev->otherend_id);
636
637 if (!be) {
638 xenbus_dev_fatal(dev, err: -ENOMEM,
639 fmt: "allocating backend structure");
640 return -ENOMEM;
641 }
642 be->dev = dev;
643 dev_set_drvdata(dev: &dev->dev, data: be);
644
645 be->blkif = xen_blkif_alloc(domid: dev->otherend_id);
646 if (IS_ERR(ptr: be->blkif)) {
647 err = PTR_ERR(ptr: be->blkif);
648 be->blkif = NULL;
649 xenbus_dev_fatal(dev, err, fmt: "creating block interface");
650 goto fail;
651 }
652
653 err = xenbus_printf(XBT_NIL, dir: dev->nodename,
654 node: "feature-max-indirect-segments", fmt: "%u",
655 MAX_INDIRECT_SEGMENTS);
656 if (err)
657 dev_warn(&dev->dev,
658 "writing %s/feature-max-indirect-segments (%d)",
659 dev->nodename, err);
660
661 /* Multi-queue: advertise how many queues are supported by us.*/
662 err = xenbus_printf(XBT_NIL, dev->nodename,
663 "multi-queue-max-queues", "%u", xenblk_max_queues);
664 if (err)
665 pr_warn("Error writing multi-queue-max-queues\n");
666
667 /* setup back pointer */
668 be->blkif->be = be;
669
670 err = xenbus_watch_pathfmt(dev, &be->backend_watch, NULL,
671 backend_changed,
672 "%s/%s", dev->nodename, "physical-device");
673 if (err)
674 goto fail;
675
676 err = xenbus_printf(XBT_NIL, dev->nodename, "max-ring-page-order", "%u",
677 xen_blkif_max_ring_order);
678 if (err)
679 pr_warn("%s write out 'max-ring-page-order' failed\n", __func__);
680
681 err = xenbus_switch_state(dev, XenbusStateInitWait);
682 if (err)
683 goto fail;
684
685 return 0;
686
687fail:
688 pr_warn("%s failed\n", __func__);
689 xen_blkbk_remove(dev);
690 return err;
691}
692
693/*
694 * Callback received when the hotplug scripts have placed the physical-device
695 * node. Read it and the mode node, and create a vbd. If the frontend is
696 * ready, connect.
697 */
698static void backend_changed(struct xenbus_watch *watch,
699 const char *path, const char *token)
700{
701 int err;
702 unsigned major;
703 unsigned minor;
704 struct backend_info *be
705 = container_of(watch, struct backend_info, backend_watch);
706 struct xenbus_device *dev = be->dev;
707 int cdrom = 0;
708 unsigned long handle;
709 char *device_type;
710
711 pr_debug("%s %p %d\n", __func__, dev, dev->otherend_id);
712
713 err = xenbus_scanf(XBT_NIL, dir: dev->nodename, node: "physical-device", fmt: "%x:%x",
714 &major, &minor);
715 if (XENBUS_EXIST_ERR(err)) {
716 /*
717 * Since this watch will fire once immediately after it is
718 * registered, we expect this. Ignore it, and wait for the
719 * hotplug scripts.
720 */
721 return;
722 }
723 if (err != 2) {
724 xenbus_dev_fatal(dev, err, "reading physical-device");
725 return;
726 }
727
728 if (be->major | be->minor) {
729 if (be->major != major || be->minor != minor)
730 pr_warn("changing physical device (from %x:%x to %x:%x) not supported.\n",
731 be->major, be->minor, major, minor);
732 return;
733 }
734
735 be->mode = xenbus_read(XBT_NIL, dev->nodename, "mode", NULL);
736 if (IS_ERR(be->mode)) {
737 err = PTR_ERR(be->mode);
738 be->mode = NULL;
739 xenbus_dev_fatal(dev, err, "reading mode");
740 return;
741 }
742
743 device_type = xenbus_read(XBT_NIL, dev->otherend, "device-type", NULL);
744 if (!IS_ERR(device_type)) {
745 cdrom = strcmp(device_type, "cdrom") == 0;
746 kfree(device_type);
747 }
748
749 /* Front end dir is a number, which is used as the handle. */
750 err = kstrtoul(strrchr(dev->otherend, '/') + 1, 0, &handle);
751 if (err) {
752 kfree(be->mode);
753 be->mode = NULL;
754 return;
755 }
756
757 be->major = major;
758 be->minor = minor;
759
760 err = xen_vbd_create(be->blkif, handle, major, minor,
761 !strchr(be->mode, 'w'), cdrom);
762
763 if (err)
764 xenbus_dev_fatal(dev, err, "creating vbd structure");
765 else {
766 err = xenvbd_sysfs_addif(dev);
767 if (err) {
768 xen_vbd_free(&be->blkif->vbd);
769 xenbus_dev_fatal(dev, err, "creating sysfs entries");
770 }
771 }
772
773 if (err) {
774 kfree(be->mode);
775 be->mode = NULL;
776 be->major = 0;
777 be->minor = 0;
778 } else {
779 /* We're potentially connected now */
780 xen_update_blkif_status(be->blkif);
781 }
782}
783
784/*
785 * Callback received when the frontend's state changes.
786 */
787static void frontend_changed(struct xenbus_device *dev,
788 enum xenbus_state frontend_state)
789{
790 struct backend_info *be = dev_get_drvdata(dev: &dev->dev);
791 int err;
792
793 pr_debug("%s %p %s\n", __func__, dev, xenbus_strstate(frontend_state));
794
795 switch (frontend_state) {
796 case XenbusStateInitialising:
797 if (dev->state == XenbusStateClosed) {
798 pr_info("%s: prepare for reconnect\n", dev->nodename);
799 xenbus_switch_state(dev, new_state: XenbusStateInitWait);
800 }
801 break;
802
803 case XenbusStateInitialised:
804 case XenbusStateConnected:
805 /*
806 * Ensure we connect even when two watches fire in
807 * close succession and we miss the intermediate value
808 * of frontend_state.
809 */
810 if (dev->state == XenbusStateConnected)
811 break;
812
813 /*
814 * Enforce precondition before potential leak point.
815 * xen_blkif_disconnect() is idempotent.
816 */
817 err = xen_blkif_disconnect(blkif: be->blkif);
818 if (err) {
819 xenbus_dev_fatal(dev, err, fmt: "pending I/O");
820 break;
821 }
822
823 err = connect_ring(be);
824 if (err) {
825 /*
826 * Clean up so that memory resources can be used by
827 * other devices. connect_ring reported already error.
828 */
829 xen_blkif_disconnect(blkif: be->blkif);
830 break;
831 }
832 xen_update_blkif_status(blkif: be->blkif);
833 break;
834
835 case XenbusStateClosing:
836 xenbus_switch_state(dev, new_state: XenbusStateClosing);
837 break;
838
839 case XenbusStateClosed:
840 xen_blkif_disconnect(blkif: be->blkif);
841 xenbus_switch_state(dev, new_state: XenbusStateClosed);
842 if (xenbus_dev_is_online(dev))
843 break;
844 fallthrough;
845 /* if not online */
846 case XenbusStateUnknown:
847 /* implies xen_blkif_disconnect() via xen_blkbk_remove() */
848 device_unregister(dev: &dev->dev);
849 break;
850
851 default:
852 xenbus_dev_fatal(dev, err: -EINVAL, fmt: "saw state %d at frontend",
853 frontend_state);
854 break;
855 }
856}
857
858/* Once a memory pressure is detected, squeeze free page pools for a while. */
859static unsigned int buffer_squeeze_duration_ms = 10;
860module_param_named(buffer_squeeze_duration_ms,
861 buffer_squeeze_duration_ms, int, 0644);
862MODULE_PARM_DESC(buffer_squeeze_duration_ms,
863"Duration in ms to squeeze pages buffer when a memory pressure is detected");
864
865/*
866 * Callback received when the memory pressure is detected.
867 */
868static void reclaim_memory(struct xenbus_device *dev)
869{
870 struct backend_info *be = dev_get_drvdata(dev: &dev->dev);
871
872 if (!be)
873 return;
874 be->blkif->buffer_squeeze_end = jiffies +
875 msecs_to_jiffies(m: buffer_squeeze_duration_ms);
876}
877
878/* ** Connection ** */
879
880/*
881 * Write the physical details regarding the block device to the store, and
882 * switch to Connected state.
883 */
884static void connect(struct backend_info *be)
885{
886 struct xenbus_transaction xbt;
887 int err;
888 struct xenbus_device *dev = be->dev;
889
890 pr_debug("%s %s\n", __func__, dev->otherend);
891
892 /* Supply the information about the device the frontend needs */
893again:
894 err = xenbus_transaction_start(t: &xbt);
895 if (err) {
896 xenbus_dev_fatal(dev, err, fmt: "starting transaction");
897 return;
898 }
899
900 /* If we can't advertise it is OK. */
901 xen_blkbk_flush_diskcache(xbt, be, state: be->blkif->vbd.flush_support);
902
903 xen_blkbk_discard(xbt, be);
904
905 xen_blkbk_barrier(xbt, be, state: be->blkif->vbd.flush_support);
906
907 err = xenbus_printf(t: xbt, dir: dev->nodename, node: "feature-persistent", fmt: "%u",
908 be->blkif->vbd.feature_gnt_persistent_parm);
909 if (err) {
910 xenbus_dev_fatal(dev, err, fmt: "writing %s/feature-persistent",
911 dev->nodename);
912 goto abort;
913 }
914
915 err = xenbus_printf(t: xbt, dir: dev->nodename, node: "sectors", fmt: "%llu",
916 (unsigned long long)vbd_sz(&be->blkif->vbd));
917 if (err) {
918 xenbus_dev_fatal(dev, err, fmt: "writing %s/sectors",
919 dev->nodename);
920 goto abort;
921 }
922
923 /* FIXME: use a typename instead */
924 err = xenbus_printf(t: xbt, dir: dev->nodename, node: "info", fmt: "%u",
925 be->blkif->vbd.type |
926 (be->blkif->vbd.readonly ? VDISK_READONLY : 0));
927 if (err) {
928 xenbus_dev_fatal(dev, err, fmt: "writing %s/info",
929 dev->nodename);
930 goto abort;
931 }
932 err = xenbus_printf(t: xbt, dir: dev->nodename, node: "sector-size", fmt: "%lu",
933 (unsigned long)bdev_logical_block_size(
934 bdev: file_bdev(bdev_file: be->blkif->vbd.bdev_file)));
935 if (err) {
936 xenbus_dev_fatal(dev, err, fmt: "writing %s/sector-size",
937 dev->nodename);
938 goto abort;
939 }
940 err = xenbus_printf(t: xbt, dir: dev->nodename, node: "physical-sector-size", fmt: "%u",
941 bdev_physical_block_size(
942 bdev: file_bdev(bdev_file: be->blkif->vbd.bdev_file)));
943 if (err)
944 xenbus_dev_error(dev, err, fmt: "writing %s/physical-sector-size",
945 dev->nodename);
946
947 err = xenbus_transaction_end(t: xbt, abort: 0);
948 if (err == -EAGAIN)
949 goto again;
950 if (err)
951 xenbus_dev_fatal(dev, err, fmt: "ending transaction");
952
953 err = xenbus_switch_state(dev, new_state: XenbusStateConnected);
954 if (err)
955 xenbus_dev_fatal(dev, err, fmt: "%s: switching to Connected state",
956 dev->nodename);
957
958 return;
959 abort:
960 xenbus_transaction_end(t: xbt, abort: 1);
961}
962
963/*
964 * Each ring may have multi pages, depends on "ring-page-order".
965 */
966static int read_per_ring_refs(struct xen_blkif_ring *ring, const char *dir)
967{
968 unsigned int ring_ref[XENBUS_MAX_RING_GRANTS];
969 struct pending_req *req, *n;
970 int err, i, j;
971 struct xen_blkif *blkif = ring->blkif;
972 struct xenbus_device *dev = blkif->be->dev;
973 unsigned int nr_grefs, evtchn;
974
975 err = xenbus_scanf(XBT_NIL, dir, node: "event-channel", fmt: "%u",
976 &evtchn);
977 if (err != 1) {
978 err = -EINVAL;
979 xenbus_dev_fatal(dev, err, "reading %s/event-channel", dir);
980 return err;
981 }
982
983 nr_grefs = blkif->nr_ring_pages;
984
985 if (unlikely(!nr_grefs)) {
986 WARN_ON(true);
987 return -EINVAL;
988 }
989
990 for (i = 0; i < nr_grefs; i++) {
991 char ring_ref_name[RINGREF_NAME_LEN];
992
993 if (blkif->multi_ref)
994 snprintf(ring_ref_name, RINGREF_NAME_LEN, "ring-ref%u", i);
995 else {
996 WARN_ON(i != 0);
997 snprintf(ring_ref_name, RINGREF_NAME_LEN, "ring-ref");
998 }
999
1000 err = xenbus_scanf(XBT_NIL, dir, ring_ref_name,
1001 "%u", &ring_ref[i]);
1002
1003 if (err != 1) {
1004 err = -EINVAL;
1005 xenbus_dev_fatal(dev, err, "reading %s/%s",
1006 dir, ring_ref_name);
1007 return err;
1008 }
1009 }
1010
1011 err = -ENOMEM;
1012 for (i = 0; i < nr_grefs * XEN_BLKIF_REQS_PER_PAGE; i++) {
1013 req = kzalloc(sizeof(*req), GFP_KERNEL);
1014 if (!req)
1015 goto fail;
1016 list_add_tail(&req->free_list, &ring->pending_free);
1017 for (j = 0; j < MAX_INDIRECT_SEGMENTS; j++) {
1018 req->segments[j] = kzalloc(sizeof(*req->segments[0]), GFP_KERNEL);
1019 if (!req->segments[j])
1020 goto fail;
1021 }
1022 for (j = 0; j < MAX_INDIRECT_PAGES; j++) {
1023 req->indirect_pages[j] = kzalloc(sizeof(*req->indirect_pages[0]),
1024 GFP_KERNEL);
1025 if (!req->indirect_pages[j])
1026 goto fail;
1027 }
1028 }
1029
1030 /* Map the shared frame, irq etc. */
1031 err = xen_blkif_map(ring, ring_ref, nr_grefs, evtchn);
1032 if (err) {
1033 xenbus_dev_fatal(dev, err, "mapping ring-ref port %u", evtchn);
1034 goto fail;
1035 }
1036
1037 return 0;
1038
1039fail:
1040 list_for_each_entry_safe(req, n, &ring->pending_free, free_list) {
1041 list_del(&req->free_list);
1042 for (j = 0; j < MAX_INDIRECT_SEGMENTS; j++) {
1043 if (!req->segments[j])
1044 break;
1045 kfree(req->segments[j]);
1046 }
1047 for (j = 0; j < MAX_INDIRECT_PAGES; j++) {
1048 if (!req->indirect_pages[j])
1049 break;
1050 kfree(req->indirect_pages[j]);
1051 }
1052 kfree(req);
1053 }
1054 return err;
1055}
1056
1057static int connect_ring(struct backend_info *be)
1058{
1059 struct xenbus_device *dev = be->dev;
1060 struct xen_blkif *blkif = be->blkif;
1061 char protocol[64] = "";
1062 int err, i;
1063 char *xspath;
1064 size_t xspathsize;
1065 const size_t xenstore_path_ext_size = 11; /* sufficient for "/queue-NNN" */
1066 unsigned int requested_num_queues = 0;
1067 unsigned int ring_page_order;
1068
1069 pr_debug("%s %s\n", __func__, dev->otherend);
1070
1071 blkif->blk_protocol = BLKIF_PROTOCOL_DEFAULT;
1072 err = xenbus_scanf(XBT_NIL, dir: dev->otherend, node: "protocol",
1073 fmt: "%63s", protocol);
1074 if (err <= 0)
1075 strcpy(protocol, "unspecified, assuming default");
1076 else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_NATIVE))
1077 blkif->blk_protocol = BLKIF_PROTOCOL_NATIVE;
1078 else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_32))
1079 blkif->blk_protocol = BLKIF_PROTOCOL_X86_32;
1080 else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_64))
1081 blkif->blk_protocol = BLKIF_PROTOCOL_X86_64;
1082 else {
1083 xenbus_dev_fatal(dev, err, "unknown fe protocol %s", protocol);
1084 return -ENOSYS;
1085 }
1086
1087 blkif->vbd.feature_gnt_persistent_parm = feature_persistent;
1088 blkif->vbd.feature_gnt_persistent =
1089 blkif->vbd.feature_gnt_persistent_parm &&
1090 xenbus_read_unsigned(dev->otherend, "feature-persistent", 0);
1091
1092 blkif->vbd.overflow_max_grants = 0;
1093
1094 /*
1095 * Read the number of hardware queues from frontend.
1096 */
1097 requested_num_queues = xenbus_read_unsigned(dev->otherend,
1098 "multi-queue-num-queues",
1099 1);
1100 if (requested_num_queues > xenblk_max_queues
1101 || requested_num_queues == 0) {
1102 /* Buggy or malicious guest. */
1103 xenbus_dev_fatal(dev, err,
1104 "guest requested %u queues, exceeding the maximum of %u.",
1105 requested_num_queues, xenblk_max_queues);
1106 return -ENOSYS;
1107 }
1108 blkif->nr_rings = requested_num_queues;
1109 if (xen_blkif_alloc_rings(blkif))
1110 return -ENOMEM;
1111
1112 pr_info("%s: using %d queues, protocol %d (%s) %s\n", dev->nodename,
1113 blkif->nr_rings, blkif->blk_protocol, protocol,
1114 blkif->vbd.feature_gnt_persistent ? "persistent grants" : "");
1115
1116 err = xenbus_scanf(XBT_NIL, dev->otherend, "ring-page-order", "%u",
1117 &ring_page_order);
1118 if (err != 1) {
1119 blkif->nr_ring_pages = 1;
1120 blkif->multi_ref = false;
1121 } else if (ring_page_order <= xen_blkif_max_ring_order) {
1122 blkif->nr_ring_pages = 1 << ring_page_order;
1123 blkif->multi_ref = true;
1124 } else {
1125 err = -EINVAL;
1126 xenbus_dev_fatal(dev, err,
1127 "requested ring page order %d exceed max:%d",
1128 ring_page_order,
1129 xen_blkif_max_ring_order);
1130 return err;
1131 }
1132
1133 if (blkif->nr_rings == 1)
1134 return read_per_ring_refs(&blkif->rings[0], dev->otherend);
1135 else {
1136 xspathsize = strlen(dev->otherend) + xenstore_path_ext_size;
1137 xspath = kmalloc(xspathsize, GFP_KERNEL);
1138 if (!xspath) {
1139 xenbus_dev_fatal(dev, -ENOMEM, "reading ring references");
1140 return -ENOMEM;
1141 }
1142
1143 for (i = 0; i < blkif->nr_rings; i++) {
1144 memset(xspath, 0, xspathsize);
1145 snprintf(xspath, xspathsize, "%s/queue-%u", dev->otherend, i);
1146 err = read_per_ring_refs(&blkif->rings[i], xspath);
1147 if (err) {
1148 kfree(xspath);
1149 return err;
1150 }
1151 }
1152 kfree(xspath);
1153 }
1154 return 0;
1155}
1156
1157static const struct xenbus_device_id xen_blkbk_ids[] = {
1158 { "vbd" },
1159 { "" }
1160};
1161
1162static struct xenbus_driver xen_blkbk_driver = {
1163 .ids = xen_blkbk_ids,
1164 .probe = xen_blkbk_probe,
1165 .remove = xen_blkbk_remove,
1166 .otherend_changed = frontend_changed,
1167 .allow_rebind = true,
1168 .reclaim_memory = reclaim_memory,
1169};
1170
1171int xen_blkif_xenbus_init(void)
1172{
1173 return xenbus_register_backend(&xen_blkbk_driver);
1174}
1175
1176void xen_blkif_xenbus_fini(void)
1177{
1178 xenbus_unregister_driver(drv: &xen_blkbk_driver);
1179}
1180

source code of linux/drivers/block/xen-blkback/xenbus.c