aboutsummaryrefslogtreecommitdiffstats
path: root/include/linux/fs.h
diff options
context:
space:
mode:
authorTejun Heo <tj@kernel.org>2010-12-08 14:57:37 -0500
committerJens Axboe <jaxboe@fusionio.com>2010-12-16 11:53:38 -0500
commit77ea887e433ad8389d416826936c110fa7910f80 (patch)
treeac9d32aabcebf5a465acae2066b12c9335b5ca6f /include/linux/fs.h
parentd2bf1b6723ed0eab378363649d15b7893bf14e91 (diff)
implement in-kernel gendisk events handling
Currently, media presence polling for removeable block devices is done from userland. There are several issues with this. * Polling is done by periodically opening the device. For SCSI devices, the command sequence generated by such action involves a few different commands including TEST_UNIT_READY. This behavior, while perfectly legal, is different from Windows which only issues single command, GET_EVENT_STATUS_NOTIFICATION. Unfortunately, some ATAPI devices lock up after being periodically queried such command sequences. * There is no reliable and unintrusive way for a userland program to tell whether the target device is safe for media presence polling. For example, polling for media presence during an on-going burning session can make it fail. The polling program can avoid this by opening the device with O_EXCL but then it risks making a valid exclusive user of the device fail w/ -EBUSY. * Userland polling is unnecessarily heavy and in-kernel implementation is lighter and better coordinated (workqueue, timer slack). This patch implements framework for in-kernel disk event handling, which includes media presence polling. * bdops->check_events() is added, which supercedes ->media_changed(). It should check whether there's any pending event and return if so. Currently, two events are defined - DISK_EVENT_MEDIA_CHANGE and DISK_EVENT_EJECT_REQUEST. ->check_events() is guaranteed not to be called parallelly. * gendisk->events and ->async_events are added. These should be initialized by block driver before passing the device to add_disk(). The former contains the mask of all supported events and the latter the mask of all events which the device can report without polling. /sys/block/*/events[_async] export these to userland. * Kernel parameter block.events_dfl_poll_msecs controls the system polling interval (default is 0 which means disable) and /sys/block/*/events_poll_msecs control polling intervals for individual devices (default is -1 meaning use system setting). Note that if a device can report all supported events asynchronously and its polling interval isn't explicitly set, the device won't be polled regardless of the system polling interval. * If a device is opened exclusively with write access, event checking is automatically disabled until all write exclusive accesses are released. * There are event 'clearing' events. For example, both of currently defined events are cleared after the device has been successfully opened. This information is passed to ->check_events() callback using @clearing argument as a hint. * Event checking is always performed from system_nrt_wq and timer slack is set to 25% for polling. * Nothing changes for drivers which implement ->media_changed() but not ->check_events(). Going forward, all drivers will be converted to ->check_events() and ->media_change() will be dropped. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Kay Sievers <kay.sievers@vrfy.org> Cc: Jan Kara <jack@suse.cz> Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Diffstat (limited to 'include/linux/fs.h')
-rw-r--r--include/linux/fs.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/include/linux/fs.h b/include/linux/fs.h
index f48501563917..997d22efdef0 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -662,6 +662,7 @@ struct block_device {
662 void * bd_claiming; 662 void * bd_claiming;
663 void * bd_holder; 663 void * bd_holder;
664 int bd_holders; 664 int bd_holders;
665 bool bd_write_holder;
665#ifdef CONFIG_SYSFS 666#ifdef CONFIG_SYSFS
666 struct gendisk * bd_holder_disk; /* for sysfs slave linkng */ 667 struct gendisk * bd_holder_disk; /* for sysfs slave linkng */
667#endif 668#endif