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authorTejun Heo <tj@kernel.org>2010-12-08 20:57:37 +0100
committerJens Axboe <jaxboe@fusionio.com>2010-12-16 17:53:38 +0100
commit77ea887e433ad8389d416826936c110fa7910f80 (patch)
treeac9d32aabcebf5a465acae2066b12c9335b5ca6f /include/linux/genhd.h
parentd2bf1b6723ed0eab378363649d15b7893bf14e91 (diff)
downloadlwn-77ea887e433ad8389d416826936c110fa7910f80.tar.gz
lwn-77ea887e433ad8389d416826936c110fa7910f80.zip
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/genhd.h')
-rw-r--r--include/linux/genhd.h18
1 files changed, 17 insertions, 1 deletions
diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index 56e17ed24816..13893aa2ac9d 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -127,6 +127,11 @@ struct hd_struct {
#define GENHD_FL_EXT_DEVT 64 /* allow extended devt */
#define GENHD_FL_NATIVE_CAPACITY 128
+enum {
+ DISK_EVENT_MEDIA_CHANGE = 1 << 0, /* media changed */
+ DISK_EVENT_EJECT_REQUEST = 1 << 1, /* eject requested */
+};
+
#define BLK_SCSI_MAX_CMDS (256)
#define BLK_SCSI_CMD_PER_LONG (BLK_SCSI_MAX_CMDS / (sizeof(long) * 8))
@@ -143,6 +148,8 @@ struct disk_part_tbl {
struct hd_struct __rcu *part[];
};
+struct disk_events;
+
struct gendisk {
/* major, first_minor and minors are input parameters only,
* don't use directly. Use disk_devt() and disk_max_parts().
@@ -154,6 +161,10 @@ struct gendisk {
char disk_name[DISK_NAME_LEN]; /* name of major driver */
char *(*devnode)(struct gendisk *gd, mode_t *mode);
+
+ unsigned int events; /* supported events */
+ unsigned int async_events; /* async events, subset of all */
+
/* Array of pointers to partitions indexed by partno.
* Protected with matching bdev lock but stat and other
* non-critical accesses use RCU. Always access through
@@ -171,8 +182,8 @@ struct gendisk {
struct kobject *slave_dir;
struct timer_rand_state *random;
-
atomic_t sync_io; /* RAID */
+ struct disk_events *ev;
#ifdef CONFIG_BLK_DEV_INTEGRITY
struct blk_integrity *integrity;
#endif
@@ -405,6 +416,11 @@ static inline int get_disk_ro(struct gendisk *disk)
return disk->part0.policy;
}
+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 unsigned int disk_clear_events(struct gendisk *disk, unsigned int mask);
+
/* drivers/char/random.c */
extern void add_disk_randomness(struct gendisk *disk);
extern void rand_initialize_disk(struct gendisk *disk);