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

   1 /*
   2  * Copyright (C) 2017 Red Hat. All rights reserved.
   3  *
   4  * This file is released under the GPL.
   5  */
   6
   7 #include "dm-cache-background-tracker.h"
   8
   9 /*----------------------------------------------------------------*/
  10
  11 #define DM_MSG_PREFIX "dm-background-tracker"
  12
  13 struct bt_work {
  14         struct list_head list;
  15         struct rb_node node;
  16         struct policy_work work;
  17 };
  18
  19 struct background_tracker {
  20         unsigned max_work;
  21         atomic_t pending_promotes;
  22         atomic_t pending_writebacks;
  23         atomic_t pending_demotes;
  24
  25         struct list_head issued;
  26         struct list_head queued;
  27         struct rb_root pending;
  28
  29         struct kmem_cache *work_cache;
  30 };
  31
  32 struct background_tracker *btracker_create(unsigned max_work)
  33 {
  34         struct background_tracker *b = kmalloc(sizeof(*b), GFP_KERNEL);
  35
  36         if (!b) {
  37                 DMERR("couldn't create background_tracker");
  38                 return NULL;
  39         }
  40
  41         b->max_work = max_work;
  42         atomic_set(&b->pending_promotes, 0);
  43         atomic_set(&b->pending_writebacks, 0);
  44         atomic_set(&b->pending_demotes, 0);
  45
  46         INIT_LIST_HEAD(&b->issued);
  47         INIT_LIST_HEAD(&b->queued);
  48
  49         b->pending = RB_ROOT;
  50         b->work_cache = KMEM_CACHE(bt_work, 0);
  51         if (!b->work_cache) {
  52                 DMERR("couldn't create mempool for background work items");
  53                 kfree(b);
  54                 b = NULL;
  55         }
  56
  57         return b;
  58 }
  59 EXPORT_SYMBOL_GPL(btracker_create);
  60
  61 void btracker_destroy(struct background_tracker *b)
  62 {
  63         kmem_cache_destroy(b->work_cache);
  64         kfree(b);
  65 }
  66 EXPORT_SYMBOL_GPL(btracker_destroy);
  67
  68 static int cmp_oblock(dm_oblock_t lhs, dm_oblock_t rhs)
  69 {
  70         if (from_oblock(lhs) < from_oblock(rhs))
  71                 return -1;
  72
  73         if (from_oblock(rhs) < from_oblock(lhs))
  74                 return 1;
  75
  76         return 0;
  77 }
  78
  79 static bool __insert_pending(struct background_tracker *b,
  80                              struct bt_work *nw)
  81 {
  82         int cmp;
  83         struct bt_work *w;
  84         struct rb_node **new = &b->pending.rb_node, *parent = NULL;
  85
  86         while (*new) {
  87                 w = container_of(*new, struct bt_work, node);
  88
  89                 parent = *new;
  90                 cmp = cmp_oblock(w->work.oblock, nw->work.oblock);
  91                 if (cmp < 0)
  92                         new = &((*new)->rb_left);
  93
  94                 else if (cmp > 0)
  95                         new = &((*new)->rb_right);
  96
  97                 else
  98                         /* already present */
  99                         return false;
 100         }
 101
 102         rb_link_node(&nw->node, parent, new);
 103         rb_insert_color(&nw->node, &b->pending);
 104
 105         return true;
 106 }
 107
 108 static struct bt_work *__find_pending(struct background_tracker *b,
 109                                       dm_oblock_t oblock)
 110 {
 111         int cmp;
 112         struct bt_work *w;
 113         struct rb_node **new = &b->pending.rb_node;
 114
 115         while (*new) {
 116                 w = container_of(*new, struct bt_work, node);
 117
 118                 cmp = cmp_oblock(w->work.oblock, oblock);
 119                 if (cmp < 0)
 120                         new = &((*new)->rb_left);
 121
 122                 else if (cmp > 0)
 123                         new = &((*new)->rb_right);
 124
 125                 else
 126                         break;
 127         }
 128
 129         return *new ? w : NULL;
 130 }
 131
 132
 133 static void update_stats(struct background_tracker *b, struct policy_work *w, int delta)
 134 {
 135         switch (w->op) {
 136         case POLICY_PROMOTE:
 137                 atomic_add(delta, &b->pending_promotes);
 138                 break;
 139
 140         case POLICY_DEMOTE:
 141                 atomic_add(delta, &b->pending_demotes);
 142                 break;
 143
 144         case POLICY_WRITEBACK:
 145                 atomic_add(delta, &b->pending_writebacks);
 146                 break;
 147         }
 148 }
 149
 150 unsigned btracker_nr_writebacks_queued(struct background_tracker *b)
 151 {
 152         return atomic_read(&b->pending_writebacks);
 153 }
 154 EXPORT_SYMBOL_GPL(btracker_nr_writebacks_queued);
 155
 156 unsigned btracker_nr_demotions_queued(struct background_tracker *b)
 157 {
 158         return atomic_read(&b->pending_demotes);
 159 }
 160 EXPORT_SYMBOL_GPL(btracker_nr_demotions_queued);
 161
 162 static bool max_work_reached(struct background_tracker *b)
 163 {
 164         return atomic_read(&b->pending_promotes) +
 165                 atomic_read(&b->pending_writebacks) +
 166                 atomic_read(&b->pending_demotes) >= b->max_work;
 167 }
 168
 169 static struct bt_work *alloc_work(struct background_tracker *b)
 170 {
 171         if (max_work_reached(b))
 172                 return NULL;
 173
 174         return kmem_cache_alloc(b->work_cache, GFP_NOWAIT);
 175 }
 176
 177 int btracker_queue(struct background_tracker *b,
 178                    struct policy_work *work,
 179                    struct policy_work **pwork)
 180 {
 181         struct bt_work *w;
 182
 183         if (pwork)
 184                 *pwork = NULL;
 185
 186         w = alloc_work(b);
 187         if (!w)
 188                 return -ENOMEM;
 189
 190         memcpy(&w->work, work, sizeof(*work));
 191
 192         if (!__insert_pending(b, w)) {
 193                 /*
 194                  * There was a race, we'll just ignore this second
 195                  * bit of work for the same oblock.
 196                  */
 197                 kmem_cache_free(b->work_cache, w);
 198                 return -EINVAL;
 199         }
 200
 201         if (pwork) {
 202                 *pwork = &w->work;
 203                 list_add(&w->list, &b->issued);
 204         } else
 205                 list_add(&w->list, &b->queued);
 206         update_stats(b, &w->work, 1);
 207
 208         return 0;
 209 }
 210 EXPORT_SYMBOL_GPL(btracker_queue);
 211
 212 /*
 213  * Returns -ENODATA if there's no work.
 214  */
 215 int btracker_issue(struct background_tracker *b, struct policy_work **work)
 216 {
 217         struct bt_work *w;
 218
 219         if (list_empty(&b->queued))
 220                 return -ENODATA;
 221
 222         w = list_first_entry(&b->queued, struct bt_work, list);
 223         list_move(&w->list, &b->issued);
 224         *work = &w->work;
 225
 226         return 0;
 227 }
 228 EXPORT_SYMBOL_GPL(btracker_issue);
 229
 230 void btracker_complete(struct background_tracker *b,
 231                        struct policy_work *op)
 232 {
 233         struct bt_work *w = container_of(op, struct bt_work, work);
 234
 235         update_stats(b, &w->work, -1);
 236         rb_erase(&w->node, &b->pending);
 237         list_del(&w->list);
 238         kmem_cache_free(b->work_cache, w);
 239 }
 240 EXPORT_SYMBOL_GPL(btracker_complete);
 241
 242 bool btracker_promotion_already_present(struct background_tracker *b,
 243                                         dm_oblock_t oblock)
 244 {
 245         return __find_pending(b, oblock) != NULL;
 246 }
 247 EXPORT_SYMBOL_GPL(btracker_promotion_already_present);
 248
 249 /*----------------------------------------------------------------*/