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

   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 #include "dm-cache-background-tracker.h"
   9
  10 /*----------------------------------------------------------------*/
  11
  12 #define DM_MSG_PREFIX "dm-background-tracker"
  13
  14 struct background_tracker {
  15         unsigned int max_work;
  16         atomic_t pending_promotes;
  17         atomic_t pending_writebacks;
  18         atomic_t pending_demotes;
  19
  20         struct list_head issued;
  21         struct list_head queued;
  22         struct rb_root pending;
  23 };
  24
  25 struct kmem_cache *btracker_work_cache = NULL;
  26
  27 struct background_tracker *btracker_create(unsigned int max_work)
  28 {
  29         struct background_tracker *b = kmalloc(sizeof(*b), GFP_KERNEL);
  30
  31         if (!b) {
  32                 DMERR("couldn't create background_tracker");
  33                 return NULL;
  34         }
  35
  36         b->max_work = max_work;
  37         atomic_set(&b->pending_promotes, 0);
  38         atomic_set(&b->pending_writebacks, 0);
  39         atomic_set(&b->pending_demotes, 0);
  40
  41         INIT_LIST_HEAD(&b->issued);
  42         INIT_LIST_HEAD(&b->queued);
  43
  44         b->pending = RB_ROOT;
  45
  46         return b;
  47 }
  48 EXPORT_SYMBOL_GPL(btracker_create);
  49
  50 void btracker_destroy(struct background_tracker *b)
  51 {
  52         struct bt_work *w, *tmp;
  53
  54         BUG_ON(!list_empty(&b->issued));
  55         list_for_each_entry_safe (w, tmp, &b->queued, list) {
  56                 list_del(&w->list);
  57                 kmem_cache_free(btracker_work_cache, w);
  58         }
  59
  60         kfree(b);
  61 }
  62 EXPORT_SYMBOL_GPL(btracker_destroy);
  63
  64 static int cmp_oblock(dm_oblock_t lhs, dm_oblock_t rhs)
  65 {
  66         if (from_oblock(lhs) < from_oblock(rhs))
  67                 return -1;
  68
  69         if (from_oblock(rhs) < from_oblock(lhs))
  70                 return 1;
  71
  72         return 0;
  73 }
  74
  75 static bool __insert_pending(struct background_tracker *b,
  76                              struct bt_work *nw)
  77 {
  78         int cmp;
  79         struct bt_work *w;
  80         struct rb_node **new = &b->pending.rb_node, *parent = NULL;
  81
  82         while (*new) {
  83                 w = container_of(*new, struct bt_work, node);
  84
  85                 parent = *new;
  86                 cmp = cmp_oblock(w->work.oblock, nw->work.oblock);
  87                 if (cmp < 0)
  88                         new = &((*new)->rb_left);
  89
  90                 else if (cmp > 0)
  91                         new = &((*new)->rb_right);
  92
  93                 else
  94                         /* already present */
  95                         return false;
  96         }
  97
  98         rb_link_node(&nw->node, parent, new);
  99         rb_insert_color(&nw->node, &b->pending);
 100
 101         return true;
 102 }
 103
 104 static struct bt_work *__find_pending(struct background_tracker *b,
 105                                       dm_oblock_t oblock)
 106 {
 107         int cmp;
 108         struct bt_work *w;
 109         struct rb_node **new = &b->pending.rb_node;
 110
 111         while (*new) {
 112                 w = container_of(*new, struct bt_work, node);
 113
 114                 cmp = cmp_oblock(w->work.oblock, oblock);
 115                 if (cmp < 0)
 116                         new = &((*new)->rb_left);
 117
 118                 else if (cmp > 0)
 119                         new = &((*new)->rb_right);
 120
 121                 else
 122                         break;
 123         }
 124
 125         return *new ? w : NULL;
 126 }
 127
 128
 129 static void update_stats(struct background_tracker *b, struct policy_work *w, int delta)
 130 {
 131         switch (w->op) {
 132         case POLICY_PROMOTE:
 133                 atomic_add(delta, &b->pending_promotes);
 134                 break;
 135
 136         case POLICY_DEMOTE:
 137                 atomic_add(delta, &b->pending_demotes);
 138                 break;
 139
 140         case POLICY_WRITEBACK:
 141                 atomic_add(delta, &b->pending_writebacks);
 142                 break;
 143         }
 144 }
 145
 146 unsigned int btracker_nr_demotions_queued(struct background_tracker *b)
 147 {
 148         return atomic_read(&b->pending_demotes);
 149 }
 150 EXPORT_SYMBOL_GPL(btracker_nr_demotions_queued);
 151
 152 static bool max_work_reached(struct background_tracker *b)
 153 {
 154         return atomic_read(&b->pending_promotes) +
 155                 atomic_read(&b->pending_writebacks) +
 156                 atomic_read(&b->pending_demotes) >= b->max_work;
 157 }
 158
 159 static struct bt_work *alloc_work(struct background_tracker *b)
 160 {
 161         if (max_work_reached(b))
 162                 return NULL;
 163
 164         return kmem_cache_alloc(btracker_work_cache, GFP_NOWAIT);
 165 }
 166
 167 int btracker_queue(struct background_tracker *b,
 168                    struct policy_work *work,
 169                    struct policy_work **pwork)
 170 {
 171         struct bt_work *w;
 172
 173         if (pwork)
 174                 *pwork = NULL;
 175
 176         w = alloc_work(b);
 177         if (!w)
 178                 return -ENOMEM;
 179
 180         memcpy(&w->work, work, sizeof(*work));
 181
 182         if (!__insert_pending(b, w)) {
 183                 /*
 184                  * There was a race, we'll just ignore this second
 185                  * bit of work for the same oblock.
 186                  */
 187                 kmem_cache_free(btracker_work_cache, w);
 188                 return -EINVAL;
 189         }
 190
 191         if (pwork) {
 192                 *pwork = &w->work;
 193                 list_add(&w->list, &b->issued);
 194         } else
 195                 list_add(&w->list, &b->queued);
 196         update_stats(b, &w->work, 1);
 197
 198         return 0;
 199 }
 200 EXPORT_SYMBOL_GPL(btracker_queue);
 201
 202 /*
 203  * Returns -ENODATA if there's no work.
 204  */
 205 int btracker_issue(struct background_tracker *b, struct policy_work **work)
 206 {
 207         struct bt_work *w;
 208
 209         if (list_empty(&b->queued))
 210                 return -ENODATA;
 211
 212         w = list_first_entry(&b->queued, struct bt_work, list);
 213         list_move(&w->list, &b->issued);
 214         *work = &w->work;
 215
 216         return 0;
 217 }
 218 EXPORT_SYMBOL_GPL(btracker_issue);
 219
 220 void btracker_complete(struct background_tracker *b,
 221                        struct policy_work *op)
 222 {
 223         struct bt_work *w = container_of(op, struct bt_work, work);
 224
 225         update_stats(b, &w->work, -1);
 226         rb_erase(&w->node, &b->pending);
 227         list_del(&w->list);
 228         kmem_cache_free(btracker_work_cache, w);
 229 }
 230 EXPORT_SYMBOL_GPL(btracker_complete);
 231
 232 bool btracker_promotion_already_present(struct background_tracker *b,
 233                                         dm_oblock_t oblock)
 234 {
 235         return __find_pending(b, oblock) != NULL;
 236 }
 237 EXPORT_SYMBOL_GPL(btracker_promotion_already_present);
 238
 239 /*----------------------------------------------------------------*/