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 bt_work {
30 	struct list_head list;
31 	struct rb_node node;
32 	struct policy_work work;
33 };
34 
35 extern struct kmem_cache *btracker_work_cache;
36 
37 struct background_work;
38 struct background_tracker;
39 
40 /*
41  * Create a new tracker, it will not be able to queue more than
42  * 'max_work' entries.
43  */
44 struct background_tracker *btracker_create(unsigned int max_work);
45 
46 /*
47  * Destroy the tracker. No issued, but not complete, work should
48  * exist when this is called. It is fine to have queued but unissued
49  * work.
50  */
51 void btracker_destroy(struct background_tracker *b);
52 
53 unsigned int btracker_nr_writebacks_queued(struct background_tracker *b);
54 unsigned int btracker_nr_demotions_queued(struct background_tracker *b);
55 
56 /*
57  * Queue some work within the tracker. 'work' should point to the work
58  * to queue, this will be copied (ownership doesn't pass).  If pwork
59  * is not NULL then it will be set to point to the tracker's internal
60  * copy of the work.
61  *
62  * returns -EINVAL iff the work is already queued.  -ENOMEM if the work
63  * couldn't be queued for another reason.
64  */
65 int btracker_queue(struct background_tracker *b,
66 		   struct policy_work *work,
67 		   struct policy_work **pwork);
68 
69 /*
70  * Hands out the next piece of work to be performed.
71  * Returns -ENODATA if there's no work.
72  */
73 int btracker_issue(struct background_tracker *b, struct policy_work **work);
74 
75 /*
76  * Informs the tracker that the work has been completed and it may forget
77  * about it.
78  */
79 void btracker_complete(struct background_tracker *b, struct policy_work *op);
80 
81 /*
82  * Predicate to see if an origin block is already scheduled for promotion.
83  */
84 bool btracker_promotion_already_present(struct background_tracker *b,
85 					dm_oblock_t oblock);
86 
87 /*----------------------------------------------------------------*/
88 
89 #endif
90