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Commit 4a0b4ddf authored by Mike Snitzer's avatar Mike Snitzer Committed by Alasdair G Kergon
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dm: do not initialise full request queue when bio based 



Change bio-based mapped devices no longer to have a fully initialized
request_queue (request_fn, elevator, etc).  This means bio-based DM
devices no longer register elevator sysfs attributes ('iosched/' tree
or 'scheduler' other than "none").

In contrast, a request-based DM device will continue to have a full
request_queue and will register elevator sysfs attributes.  Therefore
a user can determine a DM device's type by checking if elevator sysfs
attributes exist.

First allocate a minimalist request_queue structure for a DM device
(needed for both bio and request-based DM).

Initialization of a full request_queue is deferred until it is known
that the DM device is request-based, at the end of the table load
sequence.

Factor DM device's request_queue initialization:
- common to both request-based and bio-based into dm_init_md_queue().
- specific to request-based into dm_init_request_based_queue().

The md->type_lock mutex is used to protect md->queue, in addition to
md->type, during table_load().

A DM device's first table_load will establish the immutable md->type.
But md->queue initialization, based on md->type, may fail at that time
(because blk_init_allocated_queue cannot allocate memory).  Therefore
any subsequent table_load must (re)try dm_setup_md_queue independently of
establishing md->type.

Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
Acked-by: default avatarKiyoshi Ueda <k-ueda@ct.jp.nec.com>
Signed-off-by: default avatarAlasdair G Kergon <agk@redhat.com>
parent a5664dad

drivers/md/dm-ioctl.c

+10 −1
Original line number Diff line number Diff line
@@ -1189,7 +1189,7 @@ static int table_load(struct dm_ioctl *param, size_t param_size) 
		goto out;

	}



	/* Protect md->type against concurrent table loads. */

	/* Protect md->type and md->queue against concurrent table loads. */

	dm_lock_md_type(md);

	if (dm_get_md_type(md) == DM_TYPE_NONE)

		/* Initial table load: acquire type of table. */
@@ -1201,6 +1201,15 @@ static int table_load(struct dm_ioctl *param, size_t param_size) 
		r = -EINVAL;

		goto out;

	}



	/* setup md->queue to reflect md's type (may block) */

	r = dm_setup_md_queue(md);

	if (r) {

		DMWARN("unable to set up device queue for new table.");

		dm_table_destroy(t);

		dm_unlock_md_type(md);

		goto out;

	}

	dm_unlock_md_type(md);



	/* stage inactive table */

drivers/md/dm.c

+67 −25
Original line number Diff line number Diff line
@@ -126,7 +126,7 @@ struct mapped_device { 


	struct request_queue *queue;

	unsigned type;

	/* Protect type against concurrent access. */

	/* Protect queue and type against concurrent access. */

	struct mutex type_lock;



	struct gendisk *disk;
@@ -1856,6 +1856,28 @@ static const struct block_device_operations dm_blk_dops; 
static void dm_wq_work(struct work_struct *work);

static void dm_rq_barrier_work(struct work_struct *work);



static void dm_init_md_queue(struct mapped_device *md)

{

	/*

	 * Request-based dm devices cannot be stacked on top of bio-based dm

	 * devices.  The type of this dm device has not been decided yet.

	 * The type is decided at the first table loading time.

	 * To prevent problematic device stacking, clear the queue flag

	 * for request stacking support until then.

	 *

	 * This queue is new, so no concurrency on the queue_flags.

	 */

	queue_flag_clear_unlocked(QUEUE_FLAG_STACKABLE, md->queue);



	md->queue->queuedata = md;

	md->queue->backing_dev_info.congested_fn = dm_any_congested;

	md->queue->backing_dev_info.congested_data = md;

	blk_queue_make_request(md->queue, dm_request);

	blk_queue_bounce_limit(md->queue, BLK_BOUNCE_ANY);

	md->queue->unplug_fn = dm_unplug_all;

	blk_queue_merge_bvec(md->queue, dm_merge_bvec);

}



/*

 * Allocate and initialise a blank device with a given minor.

 */
@@ -1895,33 +1917,11 @@ static struct mapped_device *alloc_dev(int minor) 
	INIT_LIST_HEAD(&md->uevent_list);

	spin_lock_init(&md->uevent_lock);



	md->queue = blk_init_queue(dm_request_fn, NULL);

	md->queue = blk_alloc_queue(GFP_KERNEL);

	if (!md->queue)

		goto bad_queue;



	/*

	 * Request-based dm devices cannot be stacked on top of bio-based dm

	 * devices.  The type of this dm device has not been decided yet,

	 * although we initialized the queue using blk_init_queue().

	 * The type is decided at the first table loading time.

	 * To prevent problematic device stacking, clear the queue flag

	 * for request stacking support until then.

	 *

	 * This queue is new, so no concurrency on the queue_flags.

	 */

	queue_flag_clear_unlocked(QUEUE_FLAG_STACKABLE, md->queue);

	md->saved_make_request_fn = md->queue->make_request_fn;

	md->queue->queuedata = md;

	md->queue->backing_dev_info.congested_fn = dm_any_congested;

	md->queue->backing_dev_info.congested_data = md;

	blk_queue_make_request(md->queue, dm_request);

	blk_queue_bounce_limit(md->queue, BLK_BOUNCE_ANY);

	md->queue->unplug_fn = dm_unplug_all;

	blk_queue_merge_bvec(md->queue, dm_merge_bvec);

	blk_queue_softirq_done(md->queue, dm_softirq_done);

	blk_queue_prep_rq(md->queue, dm_prep_fn);

	blk_queue_lld_busy(md->queue, dm_lld_busy);

	blk_queue_ordered(md->queue, QUEUE_ORDERED_DRAIN_FLUSH);

	dm_init_md_queue(md);



	md->disk = alloc_disk(1);

	if (!md->disk)
@@ -2160,6 +2160,48 @@ unsigned dm_get_md_type(struct mapped_device *md) 
	return md->type;

}



/*

 * Fully initialize a request-based queue (->elevator, ->request_fn, etc).

 */

static int dm_init_request_based_queue(struct mapped_device *md)

{

	struct request_queue *q = NULL;



	if (md->queue->elevator)

		return 1;



	/* Fully initialize the queue */

	q = blk_init_allocated_queue(md->queue, dm_request_fn, NULL);

	if (!q)

		return 0;



	md->queue = q;

	md->saved_make_request_fn = md->queue->make_request_fn;

	dm_init_md_queue(md);

	blk_queue_softirq_done(md->queue, dm_softirq_done);

	blk_queue_prep_rq(md->queue, dm_prep_fn);

	blk_queue_lld_busy(md->queue, dm_lld_busy);

	blk_queue_ordered(md->queue, QUEUE_ORDERED_DRAIN_FLUSH);



	elv_register_queue(md->queue);



	return 1;

}



/*

 * Setup the DM device's queue based on md's type

 */

int dm_setup_md_queue(struct mapped_device *md)

{

	if ((dm_get_md_type(md) == DM_TYPE_REQUEST_BASED) &&

	    !dm_init_request_based_queue(md)) {

		DMWARN("Cannot initialize queue for request-based mapped device");

		return -EINVAL;

	}



	return 0;

}



static struct mapped_device *dm_find_md(dev_t dev)

{

	struct mapped_device *md;

drivers/md/dm.h

+2 −0
Original line number Diff line number Diff line
@@ -71,6 +71,8 @@ void dm_unlock_md_type(struct mapped_device *md); 
void dm_set_md_type(struct mapped_device *md, unsigned type);

unsigned dm_get_md_type(struct mapped_device *md);



int dm_setup_md_queue(struct mapped_device *md);



/*

 * To check the return value from dm_table_find_target().

 */