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Commit 2ac87401 authored by NeilBrown's avatar NeilBrown
Browse files

md/raid5: add simple plugging infrastructure. 



md/raid5 uses the plugging infrastructure provided by the block layer
and 'struct request_queue'.  However when we plug raid5 under dm there
is no request queue so we cannot use that.

So create a similar infrastructure that is much lighter weight and use
it for raid5.

Signed-off-by: default avatarNeilBrown <neilb@suse.de>
parent 11d8a6e3

drivers/md/md.c

+45 −0
Original line number Diff line number Diff line
@@ -386,6 +386,51 @@ void md_barrier_request(mddev_t *mddev, struct bio *bio) 
}

EXPORT_SYMBOL(md_barrier_request);



/* Support for plugging.

 * This mirrors the plugging support in request_queue, but does not

 * require having a whole queue

 */

static void plugger_work(struct work_struct *work)

{

	struct plug_handle *plug =

		container_of(work, struct plug_handle, unplug_work);

	plug->unplug_fn(plug);

}

static void plugger_timeout(unsigned long data)

{

	struct plug_handle *plug = (void *)data;

	kblockd_schedule_work(NULL, &plug->unplug_work);

}

void plugger_init(struct plug_handle *plug,

		  void (*unplug_fn)(struct plug_handle *))

{

	plug->unplug_flag = 0;

	plug->unplug_fn = unplug_fn;

	init_timer(&plug->unplug_timer);

	plug->unplug_timer.function = plugger_timeout;

	plug->unplug_timer.data = (unsigned long)plug;

	INIT_WORK(&plug->unplug_work, plugger_work);

}

EXPORT_SYMBOL_GPL(plugger_init);



void plugger_set_plug(struct plug_handle *plug)

{

	if (!test_and_set_bit(PLUGGED_FLAG, &plug->unplug_flag))

		mod_timer(&plug->unplug_timer, jiffies + msecs_to_jiffies(3)+1);

}

EXPORT_SYMBOL_GPL(plugger_set_plug);



int plugger_remove_plug(struct plug_handle *plug)

{

	if (test_and_clear_bit(PLUGGED_FLAG, &plug->unplug_flag)) {

		del_timer(&plug->unplug_timer);

		return 1;

	} else

		return 0;

}

EXPORT_SYMBOL_GPL(plugger_remove_plug);





static inline mddev_t *mddev_get(mddev_t *mddev)

{

	atomic_inc(&mddev->active);

drivers/md/md.h

+20 −0
Original line number Diff line number Diff line
@@ -29,6 +29,26 @@ 
typedef struct mddev_s mddev_t;

typedef struct mdk_rdev_s mdk_rdev_t;



/* generic plugging support - like that provided with request_queue,

 * but does not require a request_queue

 */

struct plug_handle {

	void			(*unplug_fn)(struct plug_handle *);

	struct timer_list	unplug_timer;

	struct work_struct	unplug_work;

	unsigned long		unplug_flag;

};

#define	PLUGGED_FLAG 1

void plugger_init(struct plug_handle *plug,

		  void (*unplug_fn)(struct plug_handle *));

void plugger_set_plug(struct plug_handle *plug);

int plugger_remove_plug(struct plug_handle *plug);

static inline void plugger_flush(struct plug_handle *plug)

{

	del_timer_sync(&plug->unplug_timer);

	cancel_work_sync(&plug->unplug_work);

}



/*

 * MD's 'extended' device

 */

drivers/md/raid5.c

+25 −14
Original line number Diff line number Diff line
@@ -201,11 +201,11 @@ static void __release_stripe(raid5_conf_t *conf, struct stripe_head *sh) 
		if (test_bit(STRIPE_HANDLE, &sh->state)) {

			if (test_bit(STRIPE_DELAYED, &sh->state)) {

				list_add_tail(&sh->lru, &conf->delayed_list);

				blk_plug_device(conf->mddev->queue);

				plugger_set_plug(&conf->plug);

			} else if (test_bit(STRIPE_BIT_DELAY, &sh->state) &&

				   sh->bm_seq - conf->seq_write > 0) {

				list_add_tail(&sh->lru, &conf->bitmap_list);

				blk_plug_device(conf->mddev->queue);

				plugger_set_plug(&conf->plug);

			} else {

				clear_bit(STRIPE_BIT_DELAY, &sh->state);

				list_add_tail(&sh->lru, &conf->handle_list);
@@ -434,7 +434,7 @@ static int has_failed(raid5_conf_t *conf) 
}



static void unplug_slaves(mddev_t *mddev);

static void raid5_unplug_device(struct request_queue *q);

static void raid5_unplug_device(raid5_conf_t *conf);



static struct stripe_head *

get_active_stripe(raid5_conf_t *conf, sector_t sector,
@@ -464,7 +464,7 @@ get_active_stripe(raid5_conf_t *conf, sector_t sector, 
						     < (conf->max_nr_stripes *3/4)

						     || !conf->inactive_blocked),

						    conf->device_lock,

						    raid5_unplug_device(conf->mddev->queue)

						    raid5_unplug_device(conf)

					);

				conf->inactive_blocked = 0;

			} else
@@ -3618,7 +3618,7 @@ static void raid5_activate_delayed(raid5_conf_t *conf) 
			list_add_tail(&sh->lru, &conf->hold_list);

		}

	} else

		blk_plug_device(conf->mddev->queue);

		plugger_set_plug(&conf->plug);

}



static void activate_bit_delay(raid5_conf_t *conf)
@@ -3659,23 +3659,33 @@ static void unplug_slaves(mddev_t *mddev) 
	rcu_read_unlock();

}



static void raid5_unplug_device(struct request_queue *q)

static void raid5_unplug_device(raid5_conf_t *conf)

{

	mddev_t *mddev = q->queuedata;

	raid5_conf_t *conf = mddev->private;

	unsigned long flags;



	spin_lock_irqsave(&conf->device_lock, flags);



	if (blk_remove_plug(q)) {

	if (plugger_remove_plug(&conf->plug)) {

		conf->seq_flush++;

		raid5_activate_delayed(conf);

	}

	md_wakeup_thread(mddev->thread);

	md_wakeup_thread(conf->mddev->thread);



	spin_unlock_irqrestore(&conf->device_lock, flags);



	unplug_slaves(mddev);

	unplug_slaves(conf->mddev);

}



static void raid5_unplug(struct plug_handle *plug)

{

	raid5_conf_t *conf = container_of(plug, raid5_conf_t, plug);

	raid5_unplug_device(conf);

}



static void raid5_unplug_queue(struct request_queue *q)

{

	mddev_t *mddev = q->queuedata;

	raid5_unplug_device(mddev->private);

}



int md_raid5_congested(mddev_t *mddev, int bits)
@@ -4085,7 +4095,7 @@ static int make_request(mddev_t *mddev, struct bio * bi) 
				 * add failed due to overlap.  Flush everything

				 * and wait a while

				 */

				raid5_unplug_device(mddev->queue);

				raid5_unplug_device(conf);

				release_stripe(sh);

				schedule();

				goto retry;
@@ -5178,6 +5188,7 @@ static int run(mddev_t *mddev) 
		       mdname(mddev));

	md_set_array_sectors(mddev, raid5_size(mddev, 0, 0));



	plugger_init(&conf->plug, raid5_unplug);

	if (mddev->queue) {

		/* read-ahead size must cover two whole stripes, which

		 * is 2 * (datadisks) * chunksize where 'n' is the
@@ -5197,7 +5208,7 @@ static int run(mddev_t *mddev) 


	mddev->queue->queue_lock = &conf->device_lock;



	mddev->queue->unplug_fn = raid5_unplug_device;

	mddev->queue->unplug_fn = raid5_unplug_queue;



	chunk_size = mddev->chunk_sectors << 9;

	blk_queue_io_min(mddev->queue, chunk_size);
@@ -5229,7 +5240,7 @@ static int stop(mddev_t *mddev) 
	mddev->thread = NULL;

	if (mddev->queue)

		mddev->queue->backing_dev_info.congested_fn = NULL;

	blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/

	plugger_flush(&conf->plug); /* the unplug fn references 'conf'*/

	free_conf(conf);

	mddev->private = NULL;

	mddev->to_remove = &raid5_attrs_group;

drivers/md/raid5.h

+3 −0
Original line number Diff line number Diff line
@@ -398,6 +398,9 @@ struct raid5_private_data { 
					    * (fresh device added).

					    * Cleared when a sync completes.

					    */



	struct plug_handle	plug;



	/* per cpu variables */

	struct raid5_percpu {

		struct page	*spare_page; /* Used when checking P/Q in raid6 */