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
 10struct 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
 24static const char *disk_events_strs[] = {
 25	[ilog2(DISK_EVENT_MEDIA_CHANGE)]	= "media_change",
 26	[ilog2(DISK_EVENT_EJECT_REQUEST)]	= "eject_request",
 27};
 28
 29static 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 */
 35static DEFINE_MUTEX(disk_events_mutex);
 36static LIST_HEAD(disk_events);
 37
 38/* disable in-kernel polling by default */
 39static unsigned long disk_events_dfl_poll_msecs;
 40
 41static 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 */
 73void 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
 98static 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);
119out_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 */
133void 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 */
151void 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 */
171static 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
184static 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 */
227static 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 * bdev_check_media_change - check if a removable media has been changed
267 * @bdev: block device to check
268 *
269 * Check whether a removable media has been changed, and attempt to free all
270 * dentries and inodes and invalidates all block device page cache entries in
271 * that case.
272 *
273 * Returns %true if the block device changed, or %false if not.
274 */
275bool bdev_check_media_change(struct block_device *bdev)
276{
277	unsigned int events;
278
279	events = disk_clear_events(bdev->bd_disk, DISK_EVENT_MEDIA_CHANGE |
280				   DISK_EVENT_EJECT_REQUEST);
281	if (!(events & DISK_EVENT_MEDIA_CHANGE))
282		return false;
283
284	if (__invalidate_device(bdev, true))
285		pr_warn("VFS: busy inodes on changed media %s\n",
286			bdev->bd_disk->disk_name);
287	set_bit(GD_NEED_PART_SCAN, &bdev->bd_disk->state);
288	return true;
289}
290EXPORT_SYMBOL(bdev_check_media_change);
291
292/**
293 * disk_force_media_change - force a media change event
294 * @disk: the disk which will raise the event
295 * @events: the events to raise
296 *
297 * Generate uevents for the disk. If DISK_EVENT_MEDIA_CHANGE is present,
298 * attempt to free all dentries and inodes and invalidates all block
299 * device page cache entries in that case.
300 *
301 * Returns %true if DISK_EVENT_MEDIA_CHANGE was raised, or %false if not.
302 */
303bool disk_force_media_change(struct gendisk *disk, unsigned int events)
304{
305	disk_event_uevent(disk, events);
306
307	if (!(events & DISK_EVENT_MEDIA_CHANGE))
308		return false;
309
310	if (__invalidate_device(disk->part0, true))
311		pr_warn("VFS: busy inodes on changed media %s\n",
312			disk->disk_name);
313	set_bit(GD_NEED_PART_SCAN, &disk->state);
314	return true;
315}
316EXPORT_SYMBOL_GPL(disk_force_media_change);
317
318/*
319 * Separate this part out so that a different pointer for clearing_ptr can be
320 * passed in for disk_clear_events.
321 */
322static void disk_events_workfn(struct work_struct *work)
323{
324	struct delayed_work *dwork = to_delayed_work(work);
325	struct disk_events *ev = container_of(dwork, struct disk_events, dwork);
326
327	disk_check_events(ev, &ev->clearing);
328}
329
330/*
331 * A disk events enabled device has the following sysfs nodes under
332 * its /sys/block/X/ directory.
333 *
334 * events		: list of all supported events
335 * events_async		: list of events which can be detected w/o polling
336 *			  (always empty, only for backwards compatibility)
337 * events_poll_msecs	: polling interval, 0: disable, -1: system default
338 */
339static ssize_t __disk_events_show(unsigned int events, char *buf)
340{
341	const char *delim = "";
342	ssize_t pos = 0;
343	int i;
344
345	for (i = 0; i < ARRAY_SIZE(disk_events_strs); i++)
346		if (events & (1 << i)) {
347			pos += sprintf(buf + pos, "%s%s",
348				       delim, disk_events_strs[i]);
349			delim = " ";
350		}
351	if (pos)
352		pos += sprintf(buf + pos, "\n");
353	return pos;
354}
355
356static ssize_t disk_events_show(struct device *dev,
357				struct device_attribute *attr, char *buf)
358{
359	struct gendisk *disk = dev_to_disk(dev);
360
361	if (!(disk->event_flags & DISK_EVENT_FLAG_UEVENT))
362		return 0;
363	return __disk_events_show(disk->events, buf);
364}
365
366static ssize_t disk_events_async_show(struct device *dev,
367				      struct device_attribute *attr, char *buf)
368{
369	return 0;
370}
371
372static ssize_t disk_events_poll_msecs_show(struct device *dev,
373					   struct device_attribute *attr,
374					   char *buf)
375{
376	struct gendisk *disk = dev_to_disk(dev);
377
378	if (!disk->ev)
379		return sprintf(buf, "-1\n");
380	return sprintf(buf, "%ld\n", disk->ev->poll_msecs);
381}
382
383static ssize_t disk_events_poll_msecs_store(struct device *dev,
384					    struct device_attribute *attr,
385					    const char *buf, size_t count)
386{
387	struct gendisk *disk = dev_to_disk(dev);
388	long intv;
389
390	if (!count || !sscanf(buf, "%ld", &intv))
391		return -EINVAL;
392
393	if (intv < 0 && intv != -1)
394		return -EINVAL;
395
396	if (!disk->ev)
397		return -ENODEV;
398
399	disk_block_events(disk);
400	disk->ev->poll_msecs = intv;
401	__disk_unblock_events(disk, true);
402	return count;
403}
404
405DEVICE_ATTR(events, 0444, disk_events_show, NULL);
406DEVICE_ATTR(events_async, 0444, disk_events_async_show, NULL);
407DEVICE_ATTR(events_poll_msecs, 0644, disk_events_poll_msecs_show,
408	    disk_events_poll_msecs_store);
409
410/*
411 * The default polling interval can be specified by the kernel
412 * parameter block.events_dfl_poll_msecs which defaults to 0
413 * (disable).  This can also be modified runtime by writing to
414 * /sys/module/block/parameters/events_dfl_poll_msecs.
415 */
416static int disk_events_set_dfl_poll_msecs(const char *val,
417					  const struct kernel_param *kp)
418{
419	struct disk_events *ev;
420	int ret;
421
422	ret = param_set_ulong(val, kp);
423	if (ret < 0)
424		return ret;
425
426	mutex_lock(&disk_events_mutex);
427	list_for_each_entry(ev, &disk_events, node)
428		disk_flush_events(ev->disk, 0);
429	mutex_unlock(&disk_events_mutex);
430	return 0;
431}
432
433static const struct kernel_param_ops disk_events_dfl_poll_msecs_param_ops = {
434	.set	= disk_events_set_dfl_poll_msecs,
435	.get	= param_get_ulong,
436};
437
438#undef MODULE_PARAM_PREFIX
439#define MODULE_PARAM_PREFIX	"block."
440
441module_param_cb(events_dfl_poll_msecs, &disk_events_dfl_poll_msecs_param_ops,
442		&disk_events_dfl_poll_msecs, 0644);
443
444/*
445 * disk_{alloc|add|del|release}_events - initialize and destroy disk_events.
446 */
447int disk_alloc_events(struct gendisk *disk)
448{
449	struct disk_events *ev;
450
451	if (!disk->fops->check_events || !disk->events)
452		return 0;
453
454	ev = kzalloc(sizeof(*ev), GFP_KERNEL);
455	if (!ev) {
456		pr_warn("%s: failed to initialize events\n", disk->disk_name);
457		return -ENOMEM;
458	}
459
460	INIT_LIST_HEAD(&ev->node);
461	ev->disk = disk;
462	spin_lock_init(&ev->lock);
463	mutex_init(&ev->block_mutex);
464	ev->block = 1;
465	ev->poll_msecs = -1;
466	INIT_DELAYED_WORK(&ev->dwork, disk_events_workfn);
467
468	disk->ev = ev;
469	return 0;
470}
471
472void disk_add_events(struct gendisk *disk)
473{
474	if (!disk->ev)
475		return;
476
477	mutex_lock(&disk_events_mutex);
478	list_add_tail(&disk->ev->node, &disk_events);
479	mutex_unlock(&disk_events_mutex);
480
481	/*
482	 * Block count is initialized to 1 and the following initial
483	 * unblock kicks it into action.
484	 */
485	__disk_unblock_events(disk, true);
486}
487
488void disk_del_events(struct gendisk *disk)
489{
490	if (disk->ev) {
491		disk_block_events(disk);
492
493		mutex_lock(&disk_events_mutex);
494		list_del_init(&disk->ev->node);
495		mutex_unlock(&disk_events_mutex);
496	}
497}
498
499void disk_release_events(struct gendisk *disk)
500{
501	/* the block count should be 1 from disk_del_events() */
502	WARN_ON_ONCE(disk->ev && disk->ev->block != 1);
503	kfree(disk->ev);
504}