block/disk-events.c

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