1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Disk events - monitor disk events like media change and eject request.
4 */
5 #include <linux/export.h>
6 #include <linux/moduleparam.h>
7 #include <linux/blkdev.h>
8 #include "blk.h"
9
10 struct disk_events {
11 struct list_head node; /* all disk_event's */
12 struct gendisk *disk; /* the associated disk */
13 spinlock_t lock;
14
15 struct mutex block_mutex; /* protects blocking */
16 int block; /* event blocking depth */
17 unsigned int pending; /* events already sent out */
18 unsigned int clearing; /* events being cleared */
19
20 long poll_msecs; /* interval, -1 for default */
21 struct delayed_work dwork;
22 };
23
24 static const char *disk_events_strs[] = {
25 [ilog2(DISK_EVENT_MEDIA_CHANGE)] = "media_change",
26 [ilog2(DISK_EVENT_EJECT_REQUEST)] = "eject_request",
27 };
28
29 static char *disk_uevents[] = {
30 [ilog2(DISK_EVENT_MEDIA_CHANGE)] = "DISK_MEDIA_CHANGE=1",
31 [ilog2(DISK_EVENT_EJECT_REQUEST)] = "DISK_EJECT_REQUEST=1",
32 };
33
34 /* list of all disk_events */
35 static DEFINE_MUTEX(disk_events_mutex);
36 static LIST_HEAD(disk_events);
37
38 /* disable in-kernel polling by default */
39 static unsigned long disk_events_dfl_poll_msecs;
40
41 static unsigned long disk_events_poll_jiffies(struct gendisk *disk)
42 {
43 struct disk_events *ev = disk->ev;
44 long intv_msecs = 0;
45
46 /*
47 * If device-specific poll interval is set, always use it. If
48 * the default is being used, poll if the POLL flag is set.
49 */
50 if (ev->poll_msecs >= 0)
51 intv_msecs = ev->poll_msecs;
52 else if (disk->event_flags & DISK_EVENT_FLAG_POLL)
53 intv_msecs = disk_events_dfl_poll_msecs;
54
55 return msecs_to_jiffies(intv_msecs);
56 }
57
58 /**
59 * disk_block_events - block and flush disk event checking
60 * @disk: disk to block events for
61 *
62 * On return from this function, it is guaranteed that event checking
63 * isn't in progress and won't happen until unblocked by
64 * disk_unblock_events(). Events blocking is counted and the actual
65 * unblocking happens after the matching number of unblocks are done.
66 *
67 * Note that this intentionally does not block event checking from
68 * disk_clear_events().
69 *
70 * CONTEXT:
71 * Might sleep.
72 */
73 void disk_block_events(struct gendisk *disk)
74 {
75 struct disk_events *ev = disk->ev;
76 unsigned long flags;
77 bool cancel;
78
79 if (!ev)
80 return;
81
82 /*
83 * Outer mutex ensures that the first blocker completes canceling
84 * the event work before further blockers are allowed to finish.
85 */
86 mutex_lock(&ev->block_mutex);
87
88 spin_lock_irqsave(&ev->lock, flags);
89 cancel = !ev->block++;
90 spin_unlock_irqrestore(&ev->lock, flags);
91
92 if (cancel)
93 cancel_delayed_work_sync(&disk->ev->dwork);
94
95 mutex_unlock(&ev->block_mutex);
96 }
97
98 static void __disk_unblock_events(struct gendisk *disk, bool check_now)
99 {
100 struct disk_events *ev = disk->ev;
101 unsigned long intv;
102 unsigned long flags;
103
104 spin_lock_irqsave(&ev->lock, flags);
105
106 if (WARN_ON_ONCE(ev->block <= 0))
107 goto out_unlock;
108
109 if (--ev->block)
110 goto out_unlock;
111
112 intv = disk_events_poll_jiffies(disk);
113 if (check_now)
114 queue_delayed_work(system_freezable_power_efficient_wq,
115 &ev->dwork, 0);
116 else if (intv)
117 queue_delayed_work(system_freezable_power_efficient_wq,
118 &ev->dwork, intv);
119 out_unlock:
120 spin_unlock_irqrestore(&ev->lock, flags);
121 }
122
123 /**
124 * disk_unblock_events - unblock disk event checking
125 * @disk: disk to unblock events for
126 *
127 * Undo disk_block_events(). When the block count reaches zero, it
128 * starts events polling if configured.
129 *
130 * CONTEXT:
131 * Don't care. Safe to call from irq context.
132 */
133 void disk_unblock_events(struct gendisk *disk)
134 {
135 if (disk->ev)
136 __disk_unblock_events(disk, false);
137 }
138
139 /**
140 * disk_flush_events - schedule immediate event checking and flushing
141 * @disk: disk to check and flush events for
142 * @mask: events to flush
143 *
144 * Schedule immediate event checking on @disk if not blocked. Events in
145 * @mask are scheduled to be cleared from the driver. Note that this
146 * doesn't clear the events from @disk->ev.
147 *
148 * CONTEXT:
149 * If @mask is non-zero must be called with disk->open_mutex held.
150 */
151 void disk_flush_events(struct gendisk *disk, unsigned int mask)
152 {
153 struct disk_events *ev = disk->ev;
154
155 if (!ev)
156 return;
157
158 spin_lock_irq(&ev->lock);
159 ev->clearing |= mask;
160 if (!ev->block)
161 mod_delayed_work(system_freezable_power_efficient_wq,
162 &ev->dwork, 0);
163 spin_unlock_irq(&ev->lock);
164 }
165
166 /*
167 * Tell userland about new events. Only the events listed in @disk->events are
168 * reported, and only if DISK_EVENT_FLAG_UEVENT is set. Otherwise, events are
169 * processed internally but never get reported to userland.
170 */
171 static void disk_event_uevent(struct gendisk *disk, unsigned int events)
172 {
173 char *envp[ARRAY_SIZE(disk_uevents) + 1] = { };
174 int nr_events = 0, i;
175
176 for (i = 0; i < ARRAY_SIZE(disk_uevents); i++)
177 if (events & disk->events & (1 << i))
178 envp[nr_events++] = disk_uevents[i];
179
180 if (nr_events)
181 kobject_uevent_env(&disk_to_dev(disk)->kobj, KOBJ_CHANGE, envp);
182 }
183
184 static void disk_check_events(struct disk_events *ev,
185 unsigned int *clearing_ptr)
186 {
187 struct gendisk *disk = ev->disk;
188 unsigned int clearing = *clearing_ptr;
189 unsigned int events;
190 unsigned long intv;
191
192 /* check events */
193 events = disk->fops->check_events(disk, clearing);
194
195 /* accumulate pending events and schedule next poll if necessary */
196 spin_lock_irq(&ev->lock);
197
198 events &= ~ev->pending;
199 ev->pending |= events;
200 *clearing_ptr &= ~clearing;
201
202 intv = disk_events_poll_jiffies(disk);
203 if (!ev->block && intv)
204 queue_delayed_work(system_freezable_power_efficient_wq,
205 &ev->dwork, intv);
206
207 spin_unlock_irq(&ev->lock);
208
209 if (events & DISK_EVENT_MEDIA_CHANGE)
210 inc_diskseq(disk);
211
212 if (disk->event_flags & DISK_EVENT_FLAG_UEVENT)
213 disk_event_uevent(disk, events);
214 }
215
216 /**
217 * disk_clear_events - synchronously check, clear and return pending events
218 * @disk: disk to fetch and clear events from
219 * @mask: mask of events to be fetched and cleared
220 *
221 * Disk events are synchronously checked and pending events in @mask
222 * are cleared and returned. This ignores the block count.
223 *
224 * CONTEXT:
225 * Might sleep.
226 */
227 static unsigned int disk_clear_events(struct gendisk *disk, unsigned int mask)
228 {
229 struct disk_events *ev = disk->ev;
230 unsigned int pending;
231 unsigned int clearing = mask;
232
233 if (!ev)
234 return 0;
235
236 disk_block_events(disk);
237
238 /*
239 * store the union of mask and ev->clearing on the stack so that the
240 * race with disk_flush_events does not cause ambiguity (ev->clearing
241 * can still be modified even if events are blocked).
242 */
243 spin_lock_irq(&ev->lock);
244 clearing |= ev->clearing;
245 ev->clearing = 0;
246 spin_unlock_irq(&ev->lock);
247
248 disk_check_events(ev, &clearing);
249 /*
250 * if ev->clearing is not 0, the disk_flush_events got called in the
251 * middle of this function, so we want to run the workfn without delay.
252 */
253 __disk_unblock_events(disk, ev->clearing ? true : false);
254
255 /* then, fetch and clear pending events */
256 spin_lock_irq(&ev->lock);
257 pending = ev->pending & mask;
258 ev->pending &= ~mask;
259 spin_unlock_irq(&ev->lock);
260 WARN_ON_ONCE(clearing & mask);
261
262 return pending;
263 }
264
265 /**
266 * disk_check_media_change - check if a removable media has been changed
267 * @disk: gendisk to check
268 *
269 * Returns %true and marks the disk for a partition rescan whether a removable
270 * media has been changed, and %false if the media did not change.
271 */
272 bool disk_check_media_change(struct gendisk *disk)
273 {
274 unsigned int events;
275
276 events = disk_clear_events(disk, DISK_EVENT_MEDIA_CHANGE |
277 DISK_EVENT_EJECT_REQUEST);
278 if (events & DISK_EVENT_MEDIA_CHANGE) {
279 set_bit(GD_NEED_PART_SCAN, &disk->state);
280 return true;
281 }
282 return false;
283 }
284 EXPORT_SYMBOL(disk_check_media_change);
285
286 /**
287 * disk_force_media_change - force a media change event
288 * @disk: the disk which will raise the event
289 *
290 * Should be called when the media changes for @disk. Generates a uevent
291 * and attempts to free all dentries and inodes and invalidates all block
292 * device page cache entries in that case.
293 */
294 void disk_force_media_change(struct gendisk *disk)
295 {
296 disk_event_uevent(disk, DISK_EVENT_MEDIA_CHANGE);
297 inc_diskseq(disk);
298 bdev_mark_dead(disk->part0, true);
299 set_bit(GD_NEED_PART_SCAN, &disk->state);
300 }
301 EXPORT_SYMBOL_GPL(disk_force_media_change);
302
303 /*
304 * Separate this part out so that a different pointer for clearing_ptr can be
305 * passed in for disk_clear_events.
306 */
307 static void disk_events_workfn(struct work_struct *work)
308 {
309 struct delayed_work *dwork = to_delayed_work(work);
310 struct disk_events *ev = container_of(dwork, struct disk_events, dwork);
311
312 disk_check_events(ev, &ev->clearing);
313 }
314
315 /*
316 * A disk events enabled device has the following sysfs nodes under
317 * its /sys/block/X/ directory.
318 *
319 * events : list of all supported events
320 * events_async : list of events which can be detected w/o polling
321 * (always empty, only for backwards compatibility)
322 * events_poll_msecs : polling interval, 0: disable, -1: system default
323 */
324 static ssize_t __disk_events_show(unsigned int events, char *buf)
325 {
326 const char *delim = "";
327 ssize_t pos = 0;
328 int i;
329
330 for (i = 0; i < ARRAY_SIZE(disk_events_strs); i++)
331 if (events & (1 << i)) {
332 pos += sprintf(buf + pos, "%s%s",
333 delim, disk_events_strs[i]);
334 delim = " ";
335 }
336 if (pos)
337 pos += sprintf(buf + pos, "\n");
338 return pos;
339 }
340
341 static ssize_t disk_events_show(struct device *dev,
342 struct device_attribute *attr, char *buf)
343 {
344 struct gendisk *disk = dev_to_disk(dev);
345
346 if (!(disk->event_flags & DISK_EVENT_FLAG_UEVENT))
347 return 0;
348 return __disk_events_show(disk->events, buf);
349 }
350
351 static ssize_t disk_events_async_show(struct device *dev,
352 struct device_attribute *attr, char *buf)
353 {
354 return 0;
355 }
356
357 static ssize_t disk_events_poll_msecs_show(struct device *dev,
358 struct device_attribute *attr,
359 char *buf)
360 {
361 struct gendisk *disk = dev_to_disk(dev);
362
363 if (!disk->ev)
364 return sprintf(buf, "-1\n");
365 return sprintf(buf, "%ld\n", disk->ev->poll_msecs);
366 }
367
368 static ssize_t disk_events_poll_msecs_store(struct device *dev,
369 struct device_attribute *attr,
370 const char *buf, size_t count)
371 {
372 struct gendisk *disk = dev_to_disk(dev);
373 long intv;
374
375 if (!count || !sscanf(buf, "%ld", &intv))
376 return -EINVAL;
377
378 if (intv < 0 && intv != -1)
379 return -EINVAL;
380
381 if (!disk->ev)
382 return -ENODEV;
383
384 disk_block_events(disk);
385 disk->ev->poll_msecs = intv;
386 __disk_unblock_events(disk, true);
387 return count;
388 }
389
390 DEVICE_ATTR(events, 0444, disk_events_show, NULL);
391 DEVICE_ATTR(events_async, 0444, disk_events_async_show, NULL);
392 DEVICE_ATTR(events_poll_msecs, 0644, disk_events_poll_msecs_show,
393 disk_events_poll_msecs_store);
394
395 /*
396 * The default polling interval can be specified by the kernel
397 * parameter block.events_dfl_poll_msecs which defaults to 0
398 * (disable). This can also be modified runtime by writing to
399 * /sys/module/block/parameters/events_dfl_poll_msecs.
400 */
401 static int disk_events_set_dfl_poll_msecs(const char *val,
402 const struct kernel_param *kp)
403 {
404 struct disk_events *ev;
405 int ret;
406
407 ret = param_set_ulong(val, kp);
408 if (ret < 0)
409 return ret;
410
411 mutex_lock(&disk_events_mutex);
412 list_for_each_entry(ev, &disk_events, node)
413 disk_flush_events(ev->disk, 0);
414 mutex_unlock(&disk_events_mutex);
415 return 0;
416 }
417
418 static const struct kernel_param_ops disk_events_dfl_poll_msecs_param_ops = {
419 .set = disk_events_set_dfl_poll_msecs,
420 .get = param_get_ulong,
421 };
422
423 #undef MODULE_PARAM_PREFIX
424 #define MODULE_PARAM_PREFIX "block."
425
426 module_param_cb(events_dfl_poll_msecs, &disk_events_dfl_poll_msecs_param_ops,
427 &disk_events_dfl_poll_msecs, 0644);
428
429 /*
430 * disk_{alloc|add|del|release}_events - initialize and destroy disk_events.
431 */
432 int disk_alloc_events(struct gendisk *disk)
433 {
434 struct disk_events *ev;
435
436 if (!disk->fops->check_events || !disk->events)
437 return 0;
438
439 ev = kzalloc(sizeof(*ev), GFP_KERNEL);
440 if (!ev) {
441 pr_warn("%s: failed to initialize events\n", disk->disk_name);
442 return -ENOMEM;
443 }
444
445 INIT_LIST_HEAD(&ev->node);
446 ev->disk = disk;
447 spin_lock_init(&ev->lock);
448 mutex_init(&ev->block_mutex);
449 ev->block = 1;
450 ev->poll_msecs = -1;
451 INIT_DELAYED_WORK(&ev->dwork, disk_events_workfn);
452
453 disk->ev = ev;
454 return 0;
455 }
456
457 void disk_add_events(struct gendisk *disk)
458 {
459 if (!disk->ev)
460 return;
461
462 mutex_lock(&disk_events_mutex);
463 list_add_tail(&disk->ev->node, &disk_events);
464 mutex_unlock(&disk_events_mutex);
465
466 /*
467 * Block count is initialized to 1 and the following initial
468 * unblock kicks it into action.
469 */
470 __disk_unblock_events(disk, true);
471 }
472
473 void disk_del_events(struct gendisk *disk)
474 {
475 if (disk->ev) {
476 disk_block_events(disk);
477
478 mutex_lock(&disk_events_mutex);
479 list_del_init(&disk->ev->node);
480 mutex_unlock(&disk_events_mutex);
481 }
482 }
483
484 void disk_release_events(struct gendisk *disk)
485 {
486 /* the block count should be 1 from disk_del_events() */
487 WARN_ON_ONCE(disk->ev && disk->ev->block != 1);
488 kfree(disk->ev);
489 }
490
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