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 bt_work {
  15         struct list_head list;
  16         struct rb_node node;
  17         struct policy_work work;
  18 };
  19
  20 struct background_tracker {
  21         unsigned int max_work;
  22         atomic_t pending_promotes;
  23         atomic_t pending_writebacks;
  24         atomic_t pending_demotes;
  25
  26         struct list_head issued;
  27         struct list_head queued;
  28         struct rb_root pending;
  29
  30         struct kmem_cache *work_cache;
  31 };
  32
  33 struct background_tracker *btracker_create(unsigned int max_work)
  34 {
  35         struct background_tracker *b = kmalloc(sizeof(*b), GFP_KERNEL);
  36
  37         if (!b) {
  38                 DMERR("couldn't create background_tracker");
  39                 return NULL;
  40         }
  41
  42         b->max_work = max_work;
  43         atomic_set(&b->pending_promotes, 0);
  44         atomic_set(&b->pending_writebacks, 0);
  45         atomic_set(&b->pending_demotes, 0);
  46
  47         INIT_LIST_HEAD(&b->issued);
  48         INIT_LIST_HEAD(&b->queued);
  49
  50         b->pending = RB_ROOT;
  51         b->work_cache = KMEM_CACHE(bt_work, 0);
  52         if (!b->work_cache) {
  53                 DMERR("couldn't create mempool for background work items");
  54                 kfree(b);
  55                 b = NULL;
  56         }
  57
  58         return b;
  59 }
  60 EXPORT_SYMBOL_GPL(btracker_create);
  61
  62 void btracker_destroy(struct background_tracker *b)
  63 {
  64         struct bt_work *w, *tmp;
  65
  66         BUG_ON(!list_empty(&b->issued));
  67         list_for_each_entry_safe (w, tmp, &b->queued, list) {
  68                 list_del(&w->list);
  69                 kmem_cache_free(b->work_cache, w);
  70         }
  71
  72         kmem_cache_destroy(b->work_cache);
  73         kfree(b);
  74 }
  75 EXPORT_SYMBOL_GPL(btracker_destroy);
  76
  77 static int cmp_oblock(dm_oblock_t lhs, dm_oblock_t rhs)
  78 {
  79         if (from_oblock(lhs) < from_oblock(rhs))
  80                 return -1;
  81
  82         if (from_oblock(rhs) < from_oblock(lhs))
  83                 return 1;
  84
  85         return 0;
  86 }
  87
  88 static bool __insert_pending(struct background_tracker *b,
  89                              struct bt_work *nw)
  90 {
  91         int cmp;
  92         struct bt_work *w;
  93         struct rb_node **new = &b->pending.rb_node, *parent = NULL;
  94
  95         while (*new) {
  96                 w = container_of(*new, struct bt_work, node);
  97
  98                 parent = *new;
  99                 cmp = cmp_oblock(w->work.oblock, nw->work.oblock);
 100                 if (cmp < 0)
 101                         new = &((*new)->rb_left);
 102
 103                 else if (cmp > 0)
 104                         new = &((*new)->rb_right);
 105
 106                 else
 107                         /* already present */
 108                         return false;
 109         }
 110
 111         rb_link_node(&nw->node, parent, new);
 112         rb_insert_color(&nw->node, &b->pending);
 113
 114         return true;
 115 }
 116
 117 static struct bt_work *__find_pending(struct background_tracker *b,
 118                                       dm_oblock_t oblock)
 119 {
 120         int cmp;
 121         struct bt_work *w;
 122         struct rb_node **new = &b->pending.rb_node;
 123
 124         while (*new) {
 125                 w = container_of(*new, struct bt_work, node);
 126
 127                 cmp = cmp_oblock(w->work.oblock, oblock);
 128                 if (cmp < 0)
 129                         new = &((*new)->rb_left);
 130
 131                 else if (cmp > 0)
 132                         new = &((*new)->rb_right);
 133
 134                 else
 135                         break;
 136         }
 137
 138         return *new ? w : NULL;
 139 }
 140
 141
 142 static void update_stats(struct background_tracker *b, struct policy_work *w, int delta)
 143 {
 144         switch (w->op) {
 145         case POLICY_PROMOTE:
 146                 atomic_add(delta, &b->pending_promotes);
 147                 break;
 148
 149         case POLICY_DEMOTE:
 150                 atomic_add(delta, &b->pending_demotes);
 151                 break;
 152
 153         case POLICY_WRITEBACK:
 154                 atomic_add(delta, &b->pending_writebacks);
 155                 break;
 156         }
 157 }
 158
 159 unsigned int btracker_nr_writebacks_queued(struct background_tracker *b)
 160 {
 161         return atomic_read(&b->pending_writebacks);
 162 }
 163 EXPORT_SYMBOL_GPL(btracker_nr_writebacks_queued);
 164
 165 unsigned int btracker_nr_demotions_queued(struct background_tracker *b)
 166 {
 167         return atomic_read(&b->pending_demotes);
 168 }
 169 EXPORT_SYMBOL_GPL(btracker_nr_demotions_queued);
 170
 171 static bool max_work_reached(struct background_tracker *b)
 172 {
 173         return atomic_read(&b->pending_promotes) +
 174                 atomic_read(&b->pending_writebacks) +
 175                 atomic_read(&b->pending_demotes) >= b->max_work;
 176 }
 177
 178 static struct bt_work *alloc_work(struct background_tracker *b)
 179 {
 180         if (max_work_reached(b))
 181                 return NULL;
 182
 183         return kmem_cache_alloc(b->work_cache, GFP_NOWAIT);
 184 }
 185
 186 int btracker_queue(struct background_tracker *b,
 187                    struct policy_work *work,
 188                    struct policy_work **pwork)
 189 {
 190         struct bt_work *w;
 191
 192         if (pwork)
 193                 *pwork = NULL;
 194
 195         w = alloc_work(b);
 196         if (!w)
 197                 return -ENOMEM;
 198
 199         memcpy(&w->work, work, sizeof(*work));
 200
 201         if (!__insert_pending(b, w)) {
 202                 /*
 203                  * There was a race, we'll just ignore this second
 204                  * bit of work for the same oblock.
 205                  */
 206                 kmem_cache_free(b->work_cache, w);
 207                 return -EINVAL;
 208         }
 209
 210         if (pwork) {
 211                 *pwork = &w->work;
 212                 list_add(&w->list, &b->issued);
 213         } else
 214                 list_add(&w->list, &b->queued);
 215         update_stats(b, &w->work, 1);
 216
 217         return 0;
 218 }
 219 EXPORT_SYMBOL_GPL(btracker_queue);
 220
 221 /*
 222  * Returns -ENODATA if there's no work.
 223  */
 224 int btracker_issue(struct background_tracker *b, struct policy_work **work)
 225 {
 226         struct bt_work *w;
 227
 228         if (list_empty(&b->queued))
 229                 return -ENODATA;
 230
 231         w = list_first_entry(&b->queued, struct bt_work, list);
 232         list_move(&w->list, &b->issued);
 233         *work = &w->work;
 234
 235         return 0;
 236 }
 237 EXPORT_SYMBOL_GPL(btracker_issue);
 238
 239 void btracker_complete(struct background_tracker *b,
 240                        struct policy_work *op)
 241 {
 242         struct bt_work *w = container_of(op, struct bt_work, work);
 243
 244         update_stats(b, &w->work, -1);
 245         rb_erase(&w->node, &b->pending);
 246         list_del(&w->list);
 247         kmem_cache_free(b->work_cache, w);
 248 }
 249 EXPORT_SYMBOL_GPL(btracker_complete);
 250
 251 bool btracker_promotion_already_present(struct background_tracker *b,
 252                                         dm_oblock_t oblock)
 253 {
 254         return __find_pending(b, oblock) != NULL;
 255 }
 256 EXPORT_SYMBOL_GPL(btracker_promotion_already_present);
 257
 258 /*----------------------------------------------------------------*/