dm bio prison: add dm_cell_promote_or_release()

}

EXPORT_SYMBOL_GPL(dm_cell_visit_release);

static int __promote_or_release(struct dm_bio_prison *prison,

				struct dm_bio_prison_cell *cell)

{

	if (bio_list_empty(&cell->bios)) {

		rb_erase(&cell->node, &prison->cells);

		return 1;

	}

	cell->holder = bio_list_pop(&cell->bios);

	return 0;

}

int dm_cell_promote_or_release(struct dm_bio_prison *prison,

			       struct dm_bio_prison_cell *cell)

{

	int r;

	unsigned long flags;

	spin_lock_irqsave(&prison->lock, flags);

	r = __promote_or_release(prison, cell);

	spin_unlock_irqrestore(&prison->lock, flags);

	return r;

}

EXPORT_SYMBOL_GPL(dm_cell_promote_or_release);

/*----------------------------------------------------------------*/

#define DEFERRED_SET_SIZE 64

			   void (*visit_fn)(void *, struct dm_bio_prison_cell *),

			   void *context, struct dm_bio_prison_cell *cell);

/*

 * Rather than always releasing the prisoners in a cell, the client may

 * want to promote one of them to be the new holder.  There is a race here

 * though between releasing an empty cell, and other threads adding new

 * inmates.  So this function makes the decision with its lock held.

 *

 * This function can have two outcomes:

 * i) An inmate is promoted to be the holder of the cell (return value of 0).

 * ii) The cell has no inmate for promotion and is released (return value of 1).

 */

int dm_cell_promote_or_release(struct dm_bio_prison *prison,

			       struct dm_bio_prison_cell *cell);

/*----------------------------------------------------------------*/

/*