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/*
* Copyright (C) 2017 Red Hat. All rights reserved.
*
* This file is released under the GPL.
*/
#ifndef DM_CACHE_BACKGROUND_WORK_H
#define DM_CACHE_BACKGROUND_WORK_H
#include <linux/vmalloc.h>
#include "dm-cache-policy.h"
/*----------------------------------------------------------------*/
/*
* The cache policy decides what background work should be performed,
* such as promotions, demotions and writebacks. The core cache target
* is in charge of performing the work, and does so when it sees fit.
*
* The background_tracker acts as a go between. Keeping track of future
* work that the policy has decided upon, and handing (issuing) it to
* the core target when requested.
*
* There is no locking in this, so calls will probably need to be
* protected with a spinlock.
*/
struct background_work;
struct background_tracker;
/*
* Create a new tracker, it will not be able to queue more than
* 'max_work' entries.
*/
struct background_tracker *btracker_create(unsigned int max_work);
/*
* Destroy the tracker. No issued, but not complete, work should
* exist when this is called. It is fine to have queued but unissued
* work.
*/
void btracker_destroy(struct background_tracker *b);
unsigned int btracker_nr_writebacks_queued(struct background_tracker *b);
unsigned int btracker_nr_demotions_queued(struct background_tracker *b);
/*
* Queue some work within the tracker. 'work' should point to the work
* to queue, this will be copied (ownership doesn't pass). If pwork
* is not NULL then it will be set to point to the tracker's internal
* copy of the work.
*
* returns -EINVAL iff the work is already queued. -ENOMEM if the work
* couldn't be queued for another reason.
*/
int btracker_queue(struct background_tracker *b,
struct policy_work *work,
struct policy_work **pwork);
/*
* Hands out the next piece of work to be performed.
* Returns -ENODATA if there's no work.
*/
int btracker_issue(struct background_tracker *b, struct policy_work **work);
/*
* Informs the tracker that the work has been completed and it may forget
* about it.
*/
void btracker_complete(struct background_tracker *b, struct policy_work *op);
/*
* Predicate to see if an origin block is already scheduled for promotion.
*/
bool btracker_promotion_already_present(struct background_tracker *b,
dm_oblock_t oblock);
/*----------------------------------------------------------------*/
#endif
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