1 /* SPDX-License-Identifier: GPL-2.0-only */
2 /*
3  * Copyright (C) 2017 Red Hat. All rights reserved.
4  *
5  * This file is released under the GPL.
6  */
7 
8 #ifndef DM_CACHE_BACKGROUND_WORK_H
9 #define DM_CACHE_BACKGROUND_WORK_H
10 
11 #include <linux/vmalloc.h>
12 #include "dm-cache-policy.h"
13 
14 /*----------------------------------------------------------------*/
15 
16 /*
17  * The cache policy decides what background work should be performed,
18  * such as promotions, demotions and writebacks. The core cache target
19  * is in charge of performing the work, and does so when it sees fit.
20  *
21  * The background_tracker acts as a go between. Keeping track of future
22  * work that the policy has decided upon, and handing (issuing) it to
23  * the core target when requested.
24  *
25  * There is no locking in this, so calls will probably need to be
26  * protected with a spinlock.
27  */
28 
29 struct background_work;
30 struct background_tracker;
31 
32 /*
33  * Create a new tracker, it will not be able to queue more than
34  * 'max_work' entries.
35  */
36 struct background_tracker *btracker_create(unsigned int max_work);
37 
38 /*
39  * Destroy the tracker. No issued, but not complete, work should
40  * exist when this is called. It is fine to have queued but unissued
41  * work.
42  */
43 void btracker_destroy(struct background_tracker *b);
44 
45 unsigned int btracker_nr_writebacks_queued(struct background_tracker *b);
46 unsigned int btracker_nr_demotions_queued(struct background_tracker *b);
47 
48 /*
49  * Queue some work within the tracker. 'work' should point to the work
50  * to queue, this will be copied (ownership doesn't pass).  If pwork
51  * is not NULL then it will be set to point to the tracker's internal
52  * copy of the work.
53  *
54  * returns -EINVAL iff the work is already queued.  -ENOMEM if the work
55  * couldn't be queued for another reason.
56  */
57 int btracker_queue(struct background_tracker *b,
58 		   struct policy_work *work,
59 		   struct policy_work **pwork);
60 
61 /*
62  * Hands out the next piece of work to be performed.
63  * Returns -ENODATA if there's no work.
64  */
65 int btracker_issue(struct background_tracker *b, struct policy_work **work);
66 
67 /*
68  * Informs the tracker that the work has been completed and it may forget
69  * about it.
70  */
71 void btracker_complete(struct background_tracker *b, struct policy_work *op);
72 
73 /*
74  * Predicate to see if an origin block is already scheduled for promotion.
75  */
76 bool btracker_promotion_already_present(struct background_tracker *b,
77 					dm_oblock_t oblock);
78 
79 /*----------------------------------------------------------------*/
80 
81 #endif
82