block: move the disk events code to a separate file

Move the code for handling disk events from genhd.c into a new file
as it isn't very related to the rest of the file while at the same
time requiring lots of forward declarations.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Link: https://lore.kernel.org/r/20210624073843.251178-2-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 484 insertions, 0 deletions

diff --git a/block/disk-events.c b/block/disk-events.c
new file mode 100644
index 000000000000..1bc5dcb75e4e
--- /dev/null
+++ b/block/disk-events.c
@@ -0,0 +1,484 @@
+// 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/genhd.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);
+}
+
+static void disk_check_events(struct disk_events *ev,
+			      unsigned int *clearing_ptr)
+{
+	struct gendisk *disk = ev->disk;
+	char *envp[ARRAY_SIZE(disk_uevents) + 1] = { };
+	unsigned int clearing = *clearing_ptr;
+	unsigned int events;
+	unsigned long intv;
+	int nr_events = 0, i;
+
+	/* 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);
+
+	/*
+	 * 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.
+	 */
+	for (i = 0; i < ARRAY_SIZE(disk_uevents); i++)
+		if ((events & disk->events & (1 << i)) &&
+		    (disk->event_flags & DISK_EVENT_FLAG_UEVENT))
+			envp[nr_events++] = disk_uevents[i];
+
+	if (nr_events)
+		kobject_uevent_env(&disk_to_dev(disk)->kobj, KOBJ_CHANGE, envp);
+}
+
+/**
+ * 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;
+}
+
+/**
+ * bdev_check_media_change - check if a removable media has been changed
+ * @bdev: block device 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 block device changed, or %false if not.
+ */
+bool bdev_check_media_change(struct block_device *bdev)
+{
+	unsigned int events;
+
+	events = disk_clear_events(bdev->bd_disk, DISK_EVENT_MEDIA_CHANGE |
+				   DISK_EVENT_EJECT_REQUEST);
+	if (!(events & DISK_EVENT_MEDIA_CHANGE))
+		return false;
+
+	if (__invalidate_device(bdev, true))
+		pr_warn("VFS: busy inodes on changed media %s\n",
+			bdev->bd_disk->disk_name);
+	set_bit(GD_NEED_PART_SCAN, &bdev->bd_disk->state);
+	return true;
+}
+EXPORT_SYMBOL(bdev_check_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;
+}
+
+static const DEVICE_ATTR(events, 0444, disk_events_show, NULL);
+static const DEVICE_ATTR(events_async, 0444, disk_events_async_show, NULL);
+static const DEVICE_ATTR(events_poll_msecs, 0644,
+			 disk_events_poll_msecs_show,
+			 disk_events_poll_msecs_store);
+
+static const struct attribute *disk_events_attrs[] = {
+	&dev_attr_events.attr,
+	&dev_attr_events_async.attr,
+	&dev_attr_events_poll_msecs.attr,
+	NULL,
+};
+
+/*
+ * 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.
+ */
+void disk_alloc_events(struct gendisk *disk)
+{
+	struct disk_events *ev;
+
+	if (!disk->fops->check_events || !disk->events)
+		return;
+
+	ev = kzalloc(sizeof(*ev), GFP_KERNEL);
+	if (!ev) {
+		pr_warn("%s: failed to initialize events\n", disk->disk_name);
+		return;
+	}
+
+	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;
+}
+
+void disk_add_events(struct gendisk *disk)
+{
+	/* FIXME: error handling */
+	if (sysfs_create_files(&disk_to_dev(disk)->kobj, disk_events_attrs) < 0)
+		pr_warn("%s: failed to create sysfs files for events\n",
+			disk->disk_name);
+
+	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);
+	}
+
+	sysfs_remove_files(&disk_to_dev(disk)->kobj, disk_events_attrs);
+}
+
+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);
+}