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Commit 85ef06d1 authored by Tejun Heo's avatar Tejun Heo Committed by Jens Axboe
Browse files

block: flush MEDIA_CHANGE from drivers on close(2) 



Currently, only open(2) is defined as the 'clearing' point.  It has
two roles - first, it's an acknowledgement from userland indicating
that the event has been received and kernel can clear pending states
and proceed to generate more events.  Secondly, it's passed on to
device drivers as a hint indicating that a synchronization point has
been reached and it might want to take a deeper look at the device.

The latter currently is only used by sr which uses two different
mechanisms - GET_EVENT_MEDIA_STATUS_NOTIFICATION and TEST_UNIT_READY
to discover events, where the former is lighter weight and safe to be
used repeatedly but may not provide full coverage.  Among other
things, GET_EVENT can't detect media removal while TUR can.

This patch makes close(2) - blkdev_put() - indicate clearing hint for
MEDIA_CHANGE to drivers.  disk_check_events() is renamed to
disk_flush_events() and updated to take @mask for events to flush
which is or'd to ev->clearing and will be passed to the driver on the
next ->check_events() invocation.

This change makes sr generate MEDIA_CHANGE when media is ejected from
userland - e.g. with eject(1).

Note: Given the current usage, it seems @clearing hint is needlessly
complex.  disk_clear_events() can simply clear all events and the hint
can be boolean @flush.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: default avatarJens Axboe <jaxboe@fusionio.com>
parent 04bf7869

block/genhd.c

+12 −10
Original line number Diff line number Diff line
@@ -1500,30 +1500,32 @@ void disk_unblock_events(struct gendisk *disk) 
}



/**

 * disk_check_events - schedule immediate event checking

 * @disk: disk to check events for

 * 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.

 * 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:

 * Don't care.  Safe to call from irq context.

 * If @mask is non-zero must be called with bdev->bd_mutex held.

 */

void disk_check_events(struct gendisk *disk)

void disk_flush_events(struct gendisk *disk, unsigned int mask)

{

	struct disk_events *ev = disk->ev;

	unsigned long flags;



	if (!ev)

		return;



	spin_lock_irqsave(&ev->lock, flags);

	spin_lock_irq(&ev->lock);

	ev->clearing |= mask;

	if (!ev->block) {

		cancel_delayed_work(&ev->dwork);

		queue_delayed_work(system_nrt_wq, &ev->dwork, 0);

	}

	spin_unlock_irqrestore(&ev->lock, flags);

	spin_unlock_irq(&ev->lock);

}

EXPORT_SYMBOL_GPL(disk_check_events);



/**

 * disk_clear_events - synchronously check, clear and return pending events
@@ -1713,7 +1715,7 @@ static int disk_events_set_dfl_poll_msecs(const char *val, 
	mutex_lock(&disk_events_mutex);



	list_for_each_entry(ev, &disk_events, node)

		disk_check_events(ev->disk);

		disk_flush_events(ev->disk, 0);



	mutex_unlock(&disk_events_mutex);

fs/block_dev.c

+14 −9
Original line number Diff line number Diff line
@@ -1447,6 +1447,8 @@ static int __blkdev_put(struct block_device *bdev, fmode_t mode, int for_part) 


int blkdev_put(struct block_device *bdev, fmode_t mode)

{

	mutex_lock(&bdev->bd_mutex);



	if (mode & FMODE_EXCL) {

		bool bdev_free;
@@ -1455,7 +1457,6 @@ int blkdev_put(struct block_device *bdev, fmode_t mode) 
		 * are protected with bdev_lock.  bd_mutex is to

		 * synchronize disk_holder unlinking.

		 */

		mutex_lock(&bdev->bd_mutex);

		spin_lock(&bdev_lock);



		WARN_ON_ONCE(--bdev->bd_holders < 0);
@@ -1473,16 +1474,20 @@ int blkdev_put(struct block_device *bdev, fmode_t mode) 
		 * If this was the last claim, remove holder link and

		 * unblock evpoll if it was a write holder.

		 */

		if (bdev_free) {

			if (bdev->bd_write_holder) {

		if (bdev_free && bdev->bd_write_holder) {

			disk_unblock_events(bdev->bd_disk);

				disk_check_events(bdev->bd_disk);

			bdev->bd_write_holder = false;

		}

	}



	/*

	 * Trigger event checking and tell drivers to flush MEDIA_CHANGE

	 * event.  This is to ensure detection of media removal commanded

	 * from userland - e.g. eject(1).

	 */

	disk_flush_events(bdev->bd_disk, DISK_EVENT_MEDIA_CHANGE);



	mutex_unlock(&bdev->bd_mutex);

	}



	return __blkdev_put(bdev, mode, 0);

}

include/linux/genhd.h

+1 −1
Original line number Diff line number Diff line
@@ -420,7 +420,7 @@ static inline int get_disk_ro(struct gendisk *disk) 


extern void disk_block_events(struct gendisk *disk);

extern void disk_unblock_events(struct gendisk *disk);

extern void disk_check_events(struct gendisk *disk);

extern void disk_flush_events(struct gendisk *disk, unsigned int mask);

extern unsigned int disk_clear_events(struct gendisk *disk, unsigned int mask);



/* drivers/char/random.c */