diff options
Diffstat (limited to '')
| -rw-r--r-- | block/disk-events.c | 493 |
1 files changed, 493 insertions, 0 deletions
diff --git a/block/disk-events.c b/block/disk-events.c new file mode 100644 index 0000000000..13c3372c46 --- /dev/null +++ b/block/disk-events.c @@ -0,0 +1,493 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Disk events - monitor disk events like media change and eject request. + */ +#include <linux/export.h> +#include <linux/moduleparam.h> +#include <linux/blkdev.h> +#include "blk.h" + +struct disk_events { + struct list_head node; /* all disk_event's */ + struct gendisk *disk; /* the associated disk */ + spinlock_t lock; + + struct mutex block_mutex; /* protects blocking */ + int block; /* event blocking depth */ + unsigned int pending; /* events already sent out */ + unsigned int clearing; /* events being cleared */ + + long poll_msecs; /* interval, -1 for default */ + struct delayed_work dwork; +}; + +static const char *disk_events_strs[] = { + [ilog2(DISK_EVENT_MEDIA_CHANGE)] = "media_change", + [ilog2(DISK_EVENT_EJECT_REQUEST)] = "eject_request", +}; + +static char *disk_uevents[] = { + [ilog2(DISK_EVENT_MEDIA_CHANGE)] = "DISK_MEDIA_CHANGE=1", + [ilog2(DISK_EVENT_EJECT_REQUEST)] = "DISK_EJECT_REQUEST=1", +}; + +/* list of all disk_events */ +static DEFINE_MUTEX(disk_events_mutex); +static LIST_HEAD(disk_events); + +/* disable in-kernel polling by default */ +static unsigned long disk_events_dfl_poll_msecs; + +static unsigned long disk_events_poll_jiffies(struct gendisk *disk) +{ + struct disk_events *ev = disk->ev; + long intv_msecs = 0; + + /* + * If device-specific poll interval is set, always use it. If + * the default is being used, poll if the POLL flag is set. + */ + if (ev->poll_msecs >= 0) + intv_msecs = ev->poll_msecs; + else if (disk->event_flags & DISK_EVENT_FLAG_POLL) + intv_msecs = disk_events_dfl_poll_msecs; + + return msecs_to_jiffies(intv_msecs); +} + +/** + * disk_block_events - block and flush disk event checking + * @disk: disk to block events for + * + * On return from this function, it is guaranteed that event checking + * isn't in progress and won't happen until unblocked by + * disk_unblock_events(). Events blocking is counted and the actual + * unblocking happens after the matching number of unblocks are done. + * + * Note that this intentionally does not block event checking from + * disk_clear_events(). + * + * CONTEXT: + * Might sleep. + */ +void disk_block_events(struct gendisk *disk) +{ + struct disk_events *ev = disk->ev; + unsigned long flags; + bool cancel; + + if (!ev) + return; + + /* + * Outer mutex ensures that the first blocker completes canceling + * the event work before further blockers are allowed to finish. + */ + mutex_lock(&ev->block_mutex); + + spin_lock_irqsave(&ev->lock, flags); + cancel = !ev->block++; + spin_unlock_irqrestore(&ev->lock, flags); + + if (cancel) + cancel_delayed_work_sync(&disk->ev->dwork); + + mutex_unlock(&ev->block_mutex); +} + +static void __disk_unblock_events(struct gendisk *disk, bool check_now) +{ + struct disk_events *ev = disk->ev; + unsigned long intv; + unsigned long flags; + + spin_lock_irqsave(&ev->lock, flags); + + if (WARN_ON_ONCE(ev->block <= 0)) + goto out_unlock; + + if (--ev->block) + goto out_unlock; + + intv = disk_events_poll_jiffies(disk); + if (check_now) + queue_delayed_work(system_freezable_power_efficient_wq, + &ev->dwork, 0); + else if (intv) + queue_delayed_work(system_freezable_power_efficient_wq, + &ev->dwork, intv); +out_unlock: + spin_unlock_irqrestore(&ev->lock, flags); +} + +/** + * disk_unblock_events - unblock disk event checking + * @disk: disk to unblock events for + * + * Undo disk_block_events(). When the block count reaches zero, it + * starts events polling if configured. + * + * CONTEXT: + * Don't care. Safe to call from irq context. + */ +void disk_unblock_events(struct gendisk *disk) +{ + if (disk->ev) + __disk_unblock_events(disk, false); +} + +/** + * disk_flush_events - schedule immediate event checking and flushing + * @disk: disk to check and flush events for + * @mask: events to flush + * + * Schedule immediate event checking on @disk if not blocked. Events in + * @mask are scheduled to be cleared from the driver. Note that this + * doesn't clear the events from @disk->ev. + * + * CONTEXT: + * If @mask is non-zero must be called with disk->open_mutex held. + */ +void disk_flush_events(struct gendisk *disk, unsigned int mask) +{ + struct disk_events *ev = disk->ev; + + if (!ev) + return; + + spin_lock_irq(&ev->lock); + ev->clearing |= mask; + if (!ev->block) + mod_delayed_work(system_freezable_power_efficient_wq, + &ev->dwork, 0); + spin_unlock_irq(&ev->lock); +} + +/* + * Tell userland about new events. Only the events listed in @disk->events are + * reported, and only if DISK_EVENT_FLAG_UEVENT is set. Otherwise, events are + * processed internally but never get reported to userland. + */ +static void disk_event_uevent(struct gendisk *disk, unsigned int events) +{ + char *envp[ARRAY_SIZE(disk_uevents) + 1] = { }; + int nr_events = 0, i; + + for (i = 0; i < ARRAY_SIZE(disk_uevents); i++) + if (events & disk->events & (1 << i)) + envp[nr_events++] = disk_uevents[i]; + + if (nr_events) + kobject_uevent_env(&disk_to_dev(disk)->kobj, KOBJ_CHANGE, envp); +} + +static void disk_check_events(struct disk_events *ev, + unsigned int *clearing_ptr) +{ + struct gendisk *disk = ev->disk; + unsigned int clearing = *clearing_ptr; + unsigned int events; + unsigned long intv; + + /* check events */ + events = disk->fops->check_events(disk, clearing); + + /* accumulate pending events and schedule next poll if necessary */ + spin_lock_irq(&ev->lock); + + events &= ~ev->pending; + ev->pending |= events; + *clearing_ptr &= ~clearing; + + intv = disk_events_poll_jiffies(disk); + if (!ev->block && intv) + queue_delayed_work(system_freezable_power_efficient_wq, + &ev->dwork, intv); + + spin_unlock_irq(&ev->lock); + + if (events & DISK_EVENT_MEDIA_CHANGE) + inc_diskseq(disk); + + if (disk->event_flags & DISK_EVENT_FLAG_UEVENT) + disk_event_uevent(disk, events); +} + +/** + * disk_clear_events - synchronously check, clear and return pending events + * @disk: disk to fetch and clear events from + * @mask: mask of events to be fetched and cleared + * + * Disk events are synchronously checked and pending events in @mask + * are cleared and returned. This ignores the block count. + * + * CONTEXT: + * Might sleep. + */ +static unsigned int disk_clear_events(struct gendisk *disk, unsigned int mask) +{ + struct disk_events *ev = disk->ev; + unsigned int pending; + unsigned int clearing = mask; + + if (!ev) + return 0; + + disk_block_events(disk); + + /* + * store the union of mask and ev->clearing on the stack so that the + * race with disk_flush_events does not cause ambiguity (ev->clearing + * can still be modified even if events are blocked). + */ + spin_lock_irq(&ev->lock); + clearing |= ev->clearing; + ev->clearing = 0; + spin_unlock_irq(&ev->lock); + + disk_check_events(ev, &clearing); + /* + * if ev->clearing is not 0, the disk_flush_events got called in the + * middle of this function, so we want to run the workfn without delay. + */ + __disk_unblock_events(disk, ev->clearing ? true : false); + + /* then, fetch and clear pending events */ + spin_lock_irq(&ev->lock); + pending = ev->pending & mask; + ev->pending &= ~mask; + spin_unlock_irq(&ev->lock); + WARN_ON_ONCE(clearing & mask); + + return pending; +} + +/** + * disk_check_media_change - check if a removable media has been changed + * @disk: gendisk to check + * + * Check whether a removable media has been changed, and attempt to free all + * dentries and inodes and invalidates all block device page cache entries in + * that case. + * + * Returns %true if the media has changed, or %false if not. + */ +bool disk_check_media_change(struct gendisk *disk) +{ + unsigned int events; + + events = disk_clear_events(disk, DISK_EVENT_MEDIA_CHANGE | + DISK_EVENT_EJECT_REQUEST); + if (!(events & DISK_EVENT_MEDIA_CHANGE)) + return false; + + bdev_mark_dead(disk->part0, true); + set_bit(GD_NEED_PART_SCAN, &disk->state); + return true; +} +EXPORT_SYMBOL(disk_check_media_change); + +/** + * disk_force_media_change - force a media change event + * @disk: the disk which will raise the event + * + * Should be called when the media changes for @disk. Generates a uevent + * and attempts to free all dentries and inodes and invalidates all block + * device page cache entries in that case. + */ +void disk_force_media_change(struct gendisk *disk) +{ + disk_event_uevent(disk, DISK_EVENT_MEDIA_CHANGE); + inc_diskseq(disk); + bdev_mark_dead(disk->part0, true); + set_bit(GD_NEED_PART_SCAN, &disk->state); +} +EXPORT_SYMBOL_GPL(disk_force_media_change); + +/* + * Separate this part out so that a different pointer for clearing_ptr can be + * passed in for disk_clear_events. + */ +static void disk_events_workfn(struct work_struct *work) +{ + struct delayed_work *dwork = to_delayed_work(work); + struct disk_events *ev = container_of(dwork, struct disk_events, dwork); + + disk_check_events(ev, &ev->clearing); +} + +/* + * A disk events enabled device has the following sysfs nodes under + * its /sys/block/X/ directory. + * + * events : list of all supported events + * events_async : list of events which can be detected w/o polling + * (always empty, only for backwards compatibility) + * events_poll_msecs : polling interval, 0: disable, -1: system default + */ +static ssize_t __disk_events_show(unsigned int events, char *buf) +{ + const char *delim = ""; + ssize_t pos = 0; + int i; + + for (i = 0; i < ARRAY_SIZE(disk_events_strs); i++) + if (events & (1 << i)) { + pos += sprintf(buf + pos, "%s%s", + delim, disk_events_strs[i]); + delim = " "; + } + if (pos) + pos += sprintf(buf + pos, "\n"); + return pos; +} + +static ssize_t disk_events_show(struct device *dev, + struct device_attribute *attr, char *buf) +{ + struct gendisk *disk = dev_to_disk(dev); + + if (!(disk->event_flags & DISK_EVENT_FLAG_UEVENT)) + return 0; + return __disk_events_show(disk->events, buf); +} + +static ssize_t disk_events_async_show(struct device *dev, + struct device_attribute *attr, char *buf) +{ + return 0; +} + +static ssize_t disk_events_poll_msecs_show(struct device *dev, + struct device_attribute *attr, + char *buf) +{ + struct gendisk *disk = dev_to_disk(dev); + + if (!disk->ev) + return sprintf(buf, "-1\n"); + return sprintf(buf, "%ld\n", disk->ev->poll_msecs); +} + +static ssize_t disk_events_poll_msecs_store(struct device *dev, + struct device_attribute *attr, + const char *buf, size_t count) +{ + struct gendisk *disk = dev_to_disk(dev); + long intv; + + if (!count || !sscanf(buf, "%ld", &intv)) + return -EINVAL; + + if (intv < 0 && intv != -1) + return -EINVAL; + + if (!disk->ev) + return -ENODEV; + + disk_block_events(disk); + disk->ev->poll_msecs = intv; + __disk_unblock_events(disk, true); + return count; +} + +DEVICE_ATTR(events, 0444, disk_events_show, NULL); +DEVICE_ATTR(events_async, 0444, disk_events_async_show, NULL); +DEVICE_ATTR(events_poll_msecs, 0644, disk_events_poll_msecs_show, + disk_events_poll_msecs_store); + +/* + * The default polling interval can be specified by the kernel + * parameter block.events_dfl_poll_msecs which defaults to 0 + * (disable). This can also be modified runtime by writing to + * /sys/module/block/parameters/events_dfl_poll_msecs. + */ +static int disk_events_set_dfl_poll_msecs(const char *val, + const struct kernel_param *kp) +{ + struct disk_events *ev; + int ret; + + ret = param_set_ulong(val, kp); + if (ret < 0) + return ret; + + mutex_lock(&disk_events_mutex); + list_for_each_entry(ev, &disk_events, node) + disk_flush_events(ev->disk, 0); + mutex_unlock(&disk_events_mutex); + return 0; +} + +static const struct kernel_param_ops disk_events_dfl_poll_msecs_param_ops = { + .set = disk_events_set_dfl_poll_msecs, + .get = param_get_ulong, +}; + +#undef MODULE_PARAM_PREFIX +#define MODULE_PARAM_PREFIX "block." + +module_param_cb(events_dfl_poll_msecs, &disk_events_dfl_poll_msecs_param_ops, + &disk_events_dfl_poll_msecs, 0644); + +/* + * disk_{alloc|add|del|release}_events - initialize and destroy disk_events. + */ +int disk_alloc_events(struct gendisk *disk) +{ + struct disk_events *ev; + + if (!disk->fops->check_events || !disk->events) + return 0; + + ev = kzalloc(sizeof(*ev), GFP_KERNEL); + if (!ev) { + pr_warn("%s: failed to initialize events\n", disk->disk_name); + return -ENOMEM; + } + + INIT_LIST_HEAD(&ev->node); + ev->disk = disk; + spin_lock_init(&ev->lock); + mutex_init(&ev->block_mutex); + ev->block = 1; + ev->poll_msecs = -1; + INIT_DELAYED_WORK(&ev->dwork, disk_events_workfn); + + disk->ev = ev; + return 0; +} + +void disk_add_events(struct gendisk *disk) +{ + if (!disk->ev) + return; + + mutex_lock(&disk_events_mutex); + list_add_tail(&disk->ev->node, &disk_events); + mutex_unlock(&disk_events_mutex); + + /* + * Block count is initialized to 1 and the following initial + * unblock kicks it into action. + */ + __disk_unblock_events(disk, true); +} + +void disk_del_events(struct gendisk *disk) +{ + if (disk->ev) { + disk_block_events(disk); + + mutex_lock(&disk_events_mutex); + list_del_init(&disk->ev->node); + mutex_unlock(&disk_events_mutex); + } +} + +void disk_release_events(struct gendisk *disk) +{ + /* the block count should be 1 from disk_del_events() */ + WARN_ON_ONCE(disk->ev && disk->ev->block != 1); + kfree(disk->ev); +} |