drivers/md/dm-cache-background-tracker.h

   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_demotions_queued(struct background_tracker *b);
  54
  55 /*
  56  * Queue some work within the tracker. 'work' should point to the work
  57  * to queue, this will be copied (ownership doesn't pass).  If pwork
  58  * is not NULL then it will be set to point to the tracker's internal
  59  * copy of the work.
  60  *
  61  * returns -EINVAL iff the work is already queued.  -ENOMEM if the work
  62  * couldn't be queued for another reason.
  63  */
  64 int btracker_queue(struct background_tracker *b,
  65                    struct policy_work *work,
  66                    struct policy_work **pwork);
  67
  68 /*
  69  * Hands out the next piece of work to be performed.
  70  * Returns -ENODATA if there's no work.
  71  */
  72 int btracker_issue(struct background_tracker *b, struct policy_work **work);
  73
  74 /*
  75  * Informs the tracker that the work has been completed and it may forget
  76  * about it.
  77  */
  78 void btracker_complete(struct background_tracker *b, struct policy_work *op);
  79
  80 /*
  81  * Predicate to see if an origin block is already scheduled for promotion.
  82  */
  83 bool btracker_promotion_already_present(struct background_tracker *b,
  84                                         dm_oblock_t oblock);
  85
  86 /*----------------------------------------------------------------*/
  87
  88 #endif