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block: flush MEDIA_CHANGE from drivers on close(2)

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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: Tejun Heo <tj@kernel.org>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
This commit is contained in:
Tejun Heo
2011-07-01 16:17:47 +02:00
committed by Jens Axboe
parent 04bf7869ca
commit 85ef06d1d2
3 changed files with 27 additions and 20 deletions
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23
fs/block_dev.c
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@@ -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);
@@ -1473,17 +1474,21 @@ 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) {
disk_unblock_events(bdev->bd_disk);
disk_check_events(bdev->bd_disk);
bdev->bd_write_holder = false;
}
if (bdev_free && bdev->bd_write_holder) {
disk_unblock_events(bdev->bd_disk);
bdev->bd_write_holder = false;
}
mutex_unlock(&bdev->bd_mutex);
}
/*
* 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);
}
EXPORT_SYMBOL(blkdev_put);