1 /*
2  * Copyright (C) 2017 Red Hat. All rights reserved.
3  *
4  * This file is released under the GPL.
5  */
6 
7 #ifndef DM_CACHE_BACKGROUND_WORK_H
8 #define DM_CACHE_BACKGROUND_WORK_H
9 
10 #include <linux/vmalloc.h>
11 #include "dm-cache-policy.h"
12 
13 /*----------------------------------------------------------------*/
14 
15 /*
16  * The cache policy decides what background work should be performed,
17  * such as promotions, demotions and writebacks. The core cache target
18  * is in charge of performing the work, and does so when it sees fit.
19  *
20  * The background_tracker acts as a go between. Keeping track of future
21  * work that the policy has decided upon, and handing (issuing) it to
22  * the core target when requested.
23  *
24  * There is no locking in this, so calls will probably need to be
25  * protected with a spinlock.
26  */
27 
28 struct background_work;
29 struct background_tracker;
30 
31 /*
32  * Create a new tracker, it will not be able to queue more than
33  * 'max_work' entries.
34  */
35 struct background_tracker *btracker_create(unsigned max_work);
36 
37 /*
38  * Destroy the tracker. No issued, but not complete, work should
39  * exist when this is called. It is fine to have queued but unissued
40  * work.
41  */
42 void btracker_destroy(struct background_tracker *b);
43 
44 unsigned btracker_nr_writebacks_queued(struct background_tracker *b);
45 unsigned btracker_nr_demotions_queued(struct background_tracker *b);
46 
47 /*
48  * Queue some work within the tracker. 'work' should point to the work
49  * to queue, this will be copied (ownership doesn't pass).  If pwork
50  * is not NULL then it will be set to point to the tracker's internal
51  * copy of the work.
52  *
53  * returns -EINVAL iff the work is already queued.  -ENOMEM if the work
54  * couldn't be queued for another reason.
55  */
56 int btracker_queue(struct background_tracker *b,
57 		   struct policy_work *work,
58 		   struct policy_work **pwork);
59 
60 /*
61  * Hands out the next piece of work to be performed.
62  * Returns -ENODATA if there's no work.
63  */
64 int btracker_issue(struct background_tracker *b, struct policy_work **work);
65 
66 /*
67  * Informs the tracker that the work has been completed and it may forget
68  * about it.
69  */
70 void btracker_complete(struct background_tracker *b, struct policy_work *op);
71 
72 /*
73  * Predicate to see if an origin block is already scheduled for promotion.
74  */
75 bool btracker_promotion_already_present(struct background_tracker *b,
76 					dm_oblock_t oblock);
77 
78 /*----------------------------------------------------------------*/
79 
80 #endif
81