--- /dev/null
+/*
+ * Copyright (C) 2015 Red Hat. All rights reserved.
+ *
+ * This file is released under the GPL.
+ */
+
+#include "dm-cache-policy.h"
+#include "dm-cache-policy-internal.h"
+#include "dm.h"
+
+#include <linux/hash.h>
+#include <linux/jiffies.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/vmalloc.h>
+#include <linux/math64.h>
+
+#define DM_MSG_PREFIX "cache-policy-smq"
+
+/*----------------------------------------------------------------*/
+
+/*
+ * Safe division functions that return zero on divide by zero.
+ */
+static unsigned safe_div(unsigned n, unsigned d)
+{
+ return d ? n / d : 0u;
+}
+
+static unsigned safe_mod(unsigned n, unsigned d)
+{
+ return d ? n % d : 0u;
+}
+
+/*----------------------------------------------------------------*/
+
+struct entry {
+ unsigned hash_next:28;
+ unsigned prev:28;
+ unsigned next:28;
+ unsigned level:7;
+ bool dirty:1;
+ bool allocated:1;
+ bool sentinel:1;
+
+ dm_oblock_t oblock;
+};
+
+/*----------------------------------------------------------------*/
+
+#define INDEXER_NULL ((1u << 28u) - 1u)
+
+/*
+ * An entry_space manages a set of entries that we use for the queues.
+ * The clean and dirty queues share entries, so this object is separate
+ * from the queue itself.
+ */
+struct entry_space {
+ struct entry *begin;
+ struct entry *end;
+};
+
+static int space_init(struct entry_space *es, unsigned nr_entries)
+{
+ if (!nr_entries) {
+ es->begin = es->end = NULL;
+ return 0;
+ }
+
+ es->begin = vzalloc(sizeof(struct entry) * nr_entries);
+ if (!es->begin)
+ return -ENOMEM;
+
+ es->end = es->begin + nr_entries;
+ return 0;
+}
+
+static void space_exit(struct entry_space *es)
+{
+ vfree(es->begin);
+}
+
+static struct entry *__get_entry(struct entry_space *es, unsigned block)
+{
+ struct entry *e;
+
+ e = es->begin + block;
+ BUG_ON(e >= es->end);
+
+ return e;
+}
+
+static unsigned to_index(struct entry_space *es, struct entry *e)
+{
+ BUG_ON(e < es->begin || e >= es->end);
+ return e - es->begin;
+}
+
+static struct entry *to_entry(struct entry_space *es, unsigned block)
+{
+ if (block == INDEXER_NULL)
+ return NULL;
+
+ return __get_entry(es, block);
+}
+
+/*----------------------------------------------------------------*/
+
+struct ilist {
+ unsigned nr_elts; /* excluding sentinel entries */
+ unsigned head, tail;
+};
+
+static void l_init(struct ilist *l)
+{
+ l->nr_elts = 0;
+ l->head = l->tail = INDEXER_NULL;
+}
+
+static struct entry *l_head(struct entry_space *es, struct ilist *l)
+{
+ return to_entry(es, l->head);
+}
+
+static struct entry *l_tail(struct entry_space *es, struct ilist *l)
+{
+ return to_entry(es, l->tail);
+}
+
+static struct entry *l_next(struct entry_space *es, struct entry *e)
+{
+ return to_entry(es, e->next);
+}
+
+static struct entry *l_prev(struct entry_space *es, struct entry *e)
+{
+ return to_entry(es, e->prev);
+}
+
+static bool l_empty(struct ilist *l)
+{
+ return l->head == INDEXER_NULL;
+}
+
+static void l_add_head(struct entry_space *es, struct ilist *l, struct entry *e)
+{
+ struct entry *head = l_head(es, l);
+
+ e->next = l->head;
+ e->prev = INDEXER_NULL;
+
+ if (head)
+ head->prev = l->head = to_index(es, e);
+ else
+ l->head = l->tail = to_index(es, e);
+
+ if (!e->sentinel)
+ l->nr_elts++;
+}
+
+static void l_add_tail(struct entry_space *es, struct ilist *l, struct entry *e)
+{
+ struct entry *tail = l_tail(es, l);
+
+ e->next = INDEXER_NULL;
+ e->prev = l->tail;
+
+ if (tail)
+ tail->next = l->tail = to_index(es, e);
+ else
+ l->head = l->tail = to_index(es, e);
+
+ if (!e->sentinel)
+ l->nr_elts++;
+}
+
+static void l_add_before(struct entry_space *es, struct ilist *l,
+ struct entry *old, struct entry *e)
+{
+ struct entry *prev = l_prev(es, old);
+
+ if (!prev)
+ l_add_head(es, l, e);
+
+ else {
+ e->prev = old->prev;
+ e->next = to_index(es, old);
+ prev->next = old->prev = to_index(es, e);
+
+ if (!e->sentinel)
+ l->nr_elts++;
+ }
+}
+
+static void l_del(struct entry_space *es, struct ilist *l, struct entry *e)
+{
+ struct entry *prev = l_prev(es, e);
+ struct entry *next = l_next(es, e);
+
+ if (prev)
+ prev->next = e->next;
+ else
+ l->head = e->next;
+
+ if (next)
+ next->prev = e->prev;
+ else
+ l->tail = e->prev;
+
+ if (!e->sentinel)
+ l->nr_elts--;
+}
+
+static struct entry *l_pop_tail(struct entry_space *es, struct ilist *l)
+{
+ struct entry *e;
+
+ for (e = l_tail(es, l); e; e = l_prev(es, e))
+ if (!e->sentinel) {
+ l_del(es, l, e);
+ return e;
+ }
+
+ return NULL;
+}
+
+/*----------------------------------------------------------------*/
+
+/*
+ * The stochastic-multi-queue is a set of lru lists stacked into levels.
+ * Entries are moved up levels when they are used, which loosely orders the
+ * most accessed entries in the top levels and least in the bottom. This
+ * structure is *much* better than a single lru list.
+ */
+#define MAX_LEVELS 64u
+
+struct queue {
+ struct entry_space *es;
+
+ unsigned nr_elts;
+ unsigned nr_levels;
+ struct ilist qs[MAX_LEVELS];
+
+ /*
+ * We maintain a count of the number of entries we would like in each
+ * level.
+ */
+ unsigned last_target_nr_elts;
+ unsigned nr_top_levels;
+ unsigned nr_in_top_levels;
+ unsigned target_count[MAX_LEVELS];
+};
+
+static void q_init(struct queue *q, struct entry_space *es, unsigned nr_levels)
+{
+ unsigned i;
+
+ q->es = es;
+ q->nr_elts = 0;
+ q->nr_levels = nr_levels;
+
+ for (i = 0; i < q->nr_levels; i++) {
+ l_init(q->qs + i);
+ q->target_count[i] = 0u;
+ }
+
+ q->last_target_nr_elts = 0u;
+ q->nr_top_levels = 0u;
+ q->nr_in_top_levels = 0u;
+}
+
+static unsigned q_size(struct queue *q)
+{
+ return q->nr_elts;
+}
+
+/*
+ * Insert an entry to the back of the given level.
+ */
+static void q_push(struct queue *q, struct entry *e)
+{
+ if (!e->sentinel)
+ q->nr_elts++;
+
+ l_add_tail(q->es, q->qs + e->level, e);
+}
+
+static void q_push_before(struct queue *q, struct entry *old, struct entry *e)
+{
+ if (!e->sentinel)
+ q->nr_elts++;
+
+ l_add_before(q->es, q->qs + e->level, old, e);
+}
+
+static void q_del(struct queue *q, struct entry *e)
+{
+ l_del(q->es, q->qs + e->level, e);
+ if (!e->sentinel)
+ q->nr_elts--;
+}
+
+/*
+ * Return the oldest entry of the lowest populated level.
+ */
+static struct entry *q_peek(struct queue *q, unsigned max_level, bool can_cross_sentinel)
+{
+ unsigned level;
+ struct entry *e;
+
+ max_level = min(max_level, q->nr_levels);
+
+ for (level = 0; level < max_level; level++)
+ for (e = l_head(q->es, q->qs + level); e; e = l_next(q->es, e)) {
+ if (e->sentinel) {
+ if (can_cross_sentinel)
+ continue;
+ else
+ break;
+ }
+
+ return e;
+ }
+
+ return NULL;
+}
+
+static struct entry *q_pop(struct queue *q)
+{
+ struct entry *e = q_peek(q, q->nr_levels, true);
+
+ if (e)
+ q_del(q, e);
+
+ return e;
+}
+
+/*
+ * Pops an entry from a level that is not past a sentinel.
+ */
+static struct entry *q_pop_old(struct queue *q, unsigned max_level)
+{
+ struct entry *e = q_peek(q, max_level, false);
+
+ if (e)
+ q_del(q, e);
+
+ return e;
+}
+
+/*
+ * This function assumes there is a non-sentinel entry to pop. It's only
+ * used by redistribute, so we know this is true. It also doesn't adjust
+ * the q->nr_elts count.
+ */
+static struct entry *__redist_pop_from(struct queue *q, unsigned level)
+{
+ struct entry *e;
+
+ for (; level < q->nr_levels; level++)
+ for (e = l_head(q->es, q->qs + level); e; e = l_next(q->es, e))
+ if (!e->sentinel) {
+ l_del(q->es, q->qs + e->level, e);
+ return e;
+ }
+
+ return NULL;
+}
+
+static void q_set_targets_subrange_(struct queue *q, unsigned nr_elts, unsigned lbegin, unsigned lend)
+{
+ unsigned level, nr_levels, entries_per_level, remainder;
+
+ BUG_ON(lbegin > lend);
+ BUG_ON(lend > q->nr_levels);
+ nr_levels = lend - lbegin;
+ entries_per_level = safe_div(nr_elts, nr_levels);
+ remainder = safe_mod(nr_elts, nr_levels);
+
+ for (level = lbegin; level < lend; level++)
+ q->target_count[level] =
+ (level < (lbegin + remainder)) ? entries_per_level + 1u : entries_per_level;
+}
+
+/*
+ * Typically we have fewer elements in the top few levels which allows us
+ * to adjust the promote threshold nicely.
+ */
+static void q_set_targets(struct queue *q)
+{
+ if (q->last_target_nr_elts == q->nr_elts)
+ return;
+
+ q->last_target_nr_elts = q->nr_elts;
+
+ if (q->nr_top_levels > q->nr_levels)
+ q_set_targets_subrange_(q, q->nr_elts, 0, q->nr_levels);
+
+ else {
+ q_set_targets_subrange_(q, q->nr_in_top_levels,
+ q->nr_levels - q->nr_top_levels, q->nr_levels);
+
+ if (q->nr_in_top_levels < q->nr_elts)
+ q_set_targets_subrange_(q, q->nr_elts - q->nr_in_top_levels,
+ 0, q->nr_levels - q->nr_top_levels);
+ else
+ q_set_targets_subrange_(q, 0, 0, q->nr_levels - q->nr_top_levels);
+ }
+}
+
+static void q_redistribute(struct queue *q)
+{
+ unsigned target, level;
+ struct ilist *l, *l_above;
+ struct entry *e;
+
+ q_set_targets(q);
+
+ for (level = 0u; level < q->nr_levels - 1u; level++) {
+ l = q->qs + level;
+ target = q->target_count[level];
+
+ /*
+ * Pull down some entries from the level above.
+ */
+ while (l->nr_elts < target) {
+ e = __redist_pop_from(q, level + 1u);
+ if (!e) {
+ /* bug in nr_elts */
+ break;
+ }
+
+ e->level = level;
+ l_add_tail(q->es, l, e);
+ }
+
+ /*
+ * Push some entries up.
+ */
+ l_above = q->qs + level + 1u;
+ while (l->nr_elts > target) {
+ e = l_pop_tail(q->es, l);
+
+ if (!e)
+ /* bug in nr_elts */
+ break;
+
+ e->level = level + 1u;
+ l_add_head(q->es, l_above, e);
+ }
+ }
+}
+
+static void q_requeue_before(struct queue *q, struct entry *dest, struct entry *e, unsigned extra_levels)
+{
+ struct entry *de;
+ unsigned new_level;
+
+ q_del(q, e);
+
+ if (extra_levels && (e->level < q->nr_levels - 1u)) {
+ new_level = min(q->nr_levels - 1u, e->level + extra_levels);
+ for (de = l_head(q->es, q->qs + new_level); de; de = l_next(q->es, de)) {
+ if (de->sentinel)
+ continue;
+
+ q_del(q, de);
+ de->level = e->level;
+
+ if (dest)
+ q_push_before(q, dest, de);
+ else
+ q_push(q, de);
+ break;
+ }
+
+ e->level = new_level;
+ }
+
+ q_push(q, e);
+}
+
+static void q_requeue(struct queue *q, struct entry *e, unsigned extra_levels)
+{
+ q_requeue_before(q, NULL, e, extra_levels);
+}
+
+/*----------------------------------------------------------------*/
+
+#define FP_SHIFT 8
+#define SIXTEENTH (1u << (FP_SHIFT - 4u))
+#define EIGHTH (1u << (FP_SHIFT - 3u))
+
+struct stats {
+ unsigned hit_threshold;
+ unsigned hits;
+ unsigned misses;
+};
+
+enum performance {
+ Q_POOR,
+ Q_FAIR,
+ Q_WELL
+};
+
+static void stats_init(struct stats *s, unsigned nr_levels)
+{
+ s->hit_threshold = (nr_levels * 3u) / 4u;
+ s->hits = 0u;
+ s->misses = 0u;
+}
+
+static void stats_reset(struct stats *s)
+{
+ s->hits = s->misses = 0u;
+}
+
+static void stats_level_accessed(struct stats *s, unsigned level)
+{
+ if (level >= s->hit_threshold)
+ s->hits++;
+ else
+ s->misses++;
+}
+
+static void stats_miss(struct stats *s)
+{
+ s->misses++;
+}
+
+/*
+ * There are times when we don't have any confidence in the hotspot queue.
+ * Such as when a fresh cache is created and the blocks have been spread
+ * out across the levels, or if an io load changes. We detect this by
+ * seeing how often a lookup is in the top levels of the hotspot queue.
+ */
+static enum performance stats_assess(struct stats *s)
+{
+ unsigned confidence = safe_div(s->hits << FP_SHIFT, s->hits + s->misses);
+
+ if (confidence < SIXTEENTH)
+ return Q_POOR;
+
+ else if (confidence < EIGHTH)
+ return Q_FAIR;
+
+ else
+ return Q_WELL;
+}
+
+/*----------------------------------------------------------------*/
+
+struct hash_table {
+ struct entry_space *es;
+ unsigned long long hash_bits;
+ unsigned *buckets;
+};
+
+/*
+ * All cache entries are stored in a chained hash table. To save space we
+ * use indexing again, and only store indexes to the next entry.
+ */
+static int h_init(struct hash_table *ht, struct entry_space *es, unsigned nr_entries)
+{
+ unsigned i, nr_buckets;
+
+ ht->es = es;
+ nr_buckets = roundup_pow_of_two(max(nr_entries / 4u, 16u));
+ ht->hash_bits = __ffs(nr_buckets);
+
+ ht->buckets = vmalloc(sizeof(*ht->buckets) * nr_buckets);
+ if (!ht->buckets)
+ return -ENOMEM;
+
+ for (i = 0; i < nr_buckets; i++)
+ ht->buckets[i] = INDEXER_NULL;
+
+ return 0;
+}
+
+static void h_exit(struct hash_table *ht)
+{
+ vfree(ht->buckets);
+}
+
+static struct entry *h_head(struct hash_table *ht, unsigned bucket)
+{
+ return to_entry(ht->es, ht->buckets[bucket]);
+}
+
+static struct entry *h_next(struct hash_table *ht, struct entry *e)
+{
+ return to_entry(ht->es, e->hash_next);
+}
+
+static void __h_insert(struct hash_table *ht, unsigned bucket, struct entry *e)
+{
+ e->hash_next = ht->buckets[bucket];
+ ht->buckets[bucket] = to_index(ht->es, e);
+}
+
+static void h_insert(struct hash_table *ht, struct entry *e)
+{
+ unsigned h = hash_64(from_oblock(e->oblock), ht->hash_bits);
+ __h_insert(ht, h, e);
+}
+
+static struct entry *__h_lookup(struct hash_table *ht, unsigned h, dm_oblock_t oblock,
+ struct entry **prev)
+{
+ struct entry *e;
+
+ *prev = NULL;
+ for (e = h_head(ht, h); e; e = h_next(ht, e)) {
+ if (e->oblock == oblock)
+ return e;
+
+ *prev = e;
+ }
+
+ return NULL;
+}
+
+static void __h_unlink(struct hash_table *ht, unsigned h,
+ struct entry *e, struct entry *prev)
+{
+ if (prev)
+ prev->hash_next = e->hash_next;
+ else
+ ht->buckets[h] = e->hash_next;
+}
+
+/*
+ * Also moves each entry to the front of the bucket.
+ */
+static struct entry *h_lookup(struct hash_table *ht, dm_oblock_t oblock)
+{
+ struct entry *e, *prev;
+ unsigned h = hash_64(from_oblock(oblock), ht->hash_bits);
+
+ e = __h_lookup(ht, h, oblock, &prev);
+ if (e && prev) {
+ /*
+ * Move to the front because this entry is likely
+ * to be hit again.
+ */
+ __h_unlink(ht, h, e, prev);
+ __h_insert(ht, h, e);
+ }
+
+ return e;
+}
+
+static void h_remove(struct hash_table *ht, struct entry *e)
+{
+ unsigned h = hash_64(from_oblock(e->oblock), ht->hash_bits);
+ struct entry *prev;
+
+ /*
+ * The down side of using a singly linked list is we have to
+ * iterate the bucket to remove an item.
+ */
+ e = __h_lookup(ht, h, e->oblock, &prev);
+ if (e)
+ __h_unlink(ht, h, e, prev);
+}
+
+/*----------------------------------------------------------------*/
+
+struct entry_alloc {
+ struct entry_space *es;
+ unsigned begin;
+
+ unsigned nr_allocated;
+ struct ilist free;
+};
+
+static void init_allocator(struct entry_alloc *ea, struct entry_space *es,
+ unsigned begin, unsigned end)
+{
+ unsigned i;
+
+ ea->es = es;
+ ea->nr_allocated = 0u;
+ ea->begin = begin;
+
+ l_init(&ea->free);
+ for (i = begin; i != end; i++)
+ l_add_tail(ea->es, &ea->free, __get_entry(ea->es, i));
+}
+
+static void init_entry(struct entry *e)
+{
+ /*
+ * We can't memset because that would clear the hotspot and
+ * sentinel bits which remain constant.
+ */
+ e->hash_next = INDEXER_NULL;
+ e->next = INDEXER_NULL;
+ e->prev = INDEXER_NULL;
+ e->level = 0u;
+ e->allocated = true;
+}
+
+static struct entry *alloc_entry(struct entry_alloc *ea)
+{
+ struct entry *e;
+
+ if (l_empty(&ea->free))
+ return NULL;
+
+ e = l_pop_tail(ea->es, &ea->free);
+ init_entry(e);
+ ea->nr_allocated++;
+
+ return e;
+}
+
+/*
+ * This assumes the cblock hasn't already been allocated.
+ */
+static struct entry *alloc_particular_entry(struct entry_alloc *ea, unsigned i)
+{
+ struct entry *e = __get_entry(ea->es, ea->begin + i);
+
+ BUG_ON(e->allocated);
+
+ l_del(ea->es, &ea->free, e);
+ init_entry(e);
+ ea->nr_allocated++;
+
+ return e;
+}
+
+static void free_entry(struct entry_alloc *ea, struct entry *e)
+{
+ BUG_ON(!ea->nr_allocated);
+ BUG_ON(!e->allocated);
+
+ ea->nr_allocated--;
+ e->allocated = false;
+ l_add_tail(ea->es, &ea->free, e);
+}
+
+static bool allocator_empty(struct entry_alloc *ea)
+{
+ return l_empty(&ea->free);
+}
+
+static unsigned get_index(struct entry_alloc *ea, struct entry *e)
+{
+ return to_index(ea->es, e) - ea->begin;
+}
+
+static struct entry *get_entry(struct entry_alloc *ea, unsigned index)
+{
+ return __get_entry(ea->es, ea->begin + index);
+}
+
+/*----------------------------------------------------------------*/
+
+#define NR_HOTSPOT_LEVELS 64u
+#define NR_CACHE_LEVELS 64u
+
+#define WRITEBACK_PERIOD (10 * HZ)
+#define DEMOTE_PERIOD (60 * HZ)
+
+#define HOTSPOT_UPDATE_PERIOD (HZ)
+#define CACHE_UPDATE_PERIOD (10u * HZ)
+
+struct smq_policy {
+ struct dm_cache_policy policy;
+
+ /* protects everything */
+ spinlock_t lock;
+ dm_cblock_t cache_size;
+ sector_t cache_block_size;
+
+ sector_t hotspot_block_size;
+ unsigned nr_hotspot_blocks;
+ unsigned cache_blocks_per_hotspot_block;
+ unsigned hotspot_level_jump;
+
+ struct entry_space es;
+ struct entry_alloc writeback_sentinel_alloc;
+ struct entry_alloc demote_sentinel_alloc;
+ struct entry_alloc hotspot_alloc;
+ struct entry_alloc cache_alloc;
+
+ unsigned long *hotspot_hit_bits;
+ unsigned long *cache_hit_bits;
+
+ /*
+ * We maintain three queues of entries. The cache proper,
+ * consisting of a clean and dirty queue, containing the currently
+ * active mappings. The hotspot queue uses a larger block size to
+ * track blocks that are being hit frequently and potential
+ * candidates for promotion to the cache.
+ */
+ struct queue hotspot;
+ struct queue clean;
+ struct queue dirty;
+
+ struct stats hotspot_stats;
+ struct stats cache_stats;
+
+ /*
+ * Keeps track of time, incremented by the core. We use this to
+ * avoid attributing multiple hits within the same tick.
+ */
+ unsigned tick;
+
+ /*
+ * The hash tables allows us to quickly find an entry by origin
+ * block.
+ */
+ struct hash_table table;
+ struct hash_table hotspot_table;
+
+ bool current_writeback_sentinels;
+ unsigned long next_writeback_period;
+
+ bool current_demote_sentinels;
+ unsigned long next_demote_period;
+
+ unsigned write_promote_level;
+ unsigned read_promote_level;
+
+ unsigned long next_hotspot_period;
+ unsigned long next_cache_period;
+};
+
+/*----------------------------------------------------------------*/
+
+static struct entry *get_sentinel(struct entry_alloc *ea, unsigned level, bool which)
+{
+ return get_entry(ea, which ? level : NR_CACHE_LEVELS + level);
+}
+
+static struct entry *writeback_sentinel(struct smq_policy *mq, unsigned level)
+{
+ return get_sentinel(&mq->writeback_sentinel_alloc, level, mq->current_writeback_sentinels);
+}
+
+static struct entry *demote_sentinel(struct smq_policy *mq, unsigned level)
+{
+ return get_sentinel(&mq->demote_sentinel_alloc, level, mq->current_demote_sentinels);
+}
+
+static void __update_writeback_sentinels(struct smq_policy *mq)
+{
+ unsigned level;
+ struct queue *q = &mq->dirty;
+ struct entry *sentinel;
+
+ for (level = 0; level < q->nr_levels; level++) {
+ sentinel = writeback_sentinel(mq, level);
+ q_del(q, sentinel);
+ q_push(q, sentinel);
+ }
+}
+
+static void __update_demote_sentinels(struct smq_policy *mq)
+{
+ unsigned level;
+ struct queue *q = &mq->clean;
+ struct entry *sentinel;
+
+ for (level = 0; level < q->nr_levels; level++) {
+ sentinel = demote_sentinel(mq, level);
+ q_del(q, sentinel);
+ q_push(q, sentinel);
+ }
+}
+
+static void update_sentinels(struct smq_policy *mq)
+{
+ if (time_after(jiffies, mq->next_writeback_period)) {
+ __update_writeback_sentinels(mq);
+ mq->next_writeback_period = jiffies + WRITEBACK_PERIOD;
+ mq->current_writeback_sentinels = !mq->current_writeback_sentinels;
+ }
+
+ if (time_after(jiffies, mq->next_demote_period)) {
+ __update_demote_sentinels(mq);
+ mq->next_demote_period = jiffies + DEMOTE_PERIOD;
+ mq->current_demote_sentinels = !mq->current_demote_sentinels;
+ }
+}
+
+static void __sentinels_init(struct smq_policy *mq)
+{
+ unsigned level;
+ struct entry *sentinel;
+
+ for (level = 0; level < NR_CACHE_LEVELS; level++) {
+ sentinel = writeback_sentinel(mq, level);
+ sentinel->level = level;
+ q_push(&mq->dirty, sentinel);
+
+ sentinel = demote_sentinel(mq, level);
+ sentinel->level = level;
+ q_push(&mq->clean, sentinel);
+ }
+}
+
+static void sentinels_init(struct smq_policy *mq)
+{
+ mq->next_writeback_period = jiffies + WRITEBACK_PERIOD;
+ mq->next_demote_period = jiffies + DEMOTE_PERIOD;
+
+ mq->current_writeback_sentinels = false;
+ mq->current_demote_sentinels = false;
+ __sentinels_init(mq);
+
+ mq->current_writeback_sentinels = !mq->current_writeback_sentinels;
+ mq->current_demote_sentinels = !mq->current_demote_sentinels;
+ __sentinels_init(mq);
+}
+
+/*----------------------------------------------------------------*/
+
+/*
+ * These methods tie together the dirty queue, clean queue and hash table.
+ */
+static void push_new(struct smq_policy *mq, struct entry *e)
+{
+ struct queue *q = e->dirty ? &mq->dirty : &mq->clean;
+ h_insert(&mq->table, e);
+ q_push(q, e);
+}
+
+static void push(struct smq_policy *mq, struct entry *e)
+{
+ struct entry *sentinel;
+
+ h_insert(&mq->table, e);
+
+ /*
+ * Punch this into the queue just in front of the sentinel, to
+ * ensure it's cleaned straight away.
+ */
+ if (e->dirty) {
+ sentinel = writeback_sentinel(mq, e->level);
+ q_push_before(&mq->dirty, sentinel, e);
+ } else {
+ sentinel = demote_sentinel(mq, e->level);
+ q_push_before(&mq->clean, sentinel, e);
+ }
+}
+
+/*
+ * Removes an entry from cache. Removes from the hash table.
+ */
+static void __del(struct smq_policy *mq, struct queue *q, struct entry *e)
+{
+ q_del(q, e);
+ h_remove(&mq->table, e);
+}
+
+static void del(struct smq_policy *mq, struct entry *e)
+{
+ __del(mq, e->dirty ? &mq->dirty : &mq->clean, e);
+}
+
+static struct entry *pop_old(struct smq_policy *mq, struct queue *q, unsigned max_level)
+{
+ struct entry *e = q_pop_old(q, max_level);
+ if (e)
+ h_remove(&mq->table, e);
+ return e;
+}
+
+static dm_cblock_t infer_cblock(struct smq_policy *mq, struct entry *e)
+{
+ return to_cblock(get_index(&mq->cache_alloc, e));
+}
+
+static void requeue(struct smq_policy *mq, struct entry *e)
+{
+ struct entry *sentinel;
+
+ if (!test_and_set_bit(from_cblock(infer_cblock(mq, e)), mq->cache_hit_bits)) {
+ if (e->dirty) {
+ sentinel = writeback_sentinel(mq, e->level);
+ q_requeue_before(&mq->dirty, sentinel, e, 1u);
+ } else {
+ sentinel = demote_sentinel(mq, e->level);
+ q_requeue_before(&mq->clean, sentinel, e, 1u);
+ }
+ }
+}
+
+static unsigned default_promote_level(struct smq_policy *mq)
+{
+ /*
+ * The promote level depends on the current performance of the
+ * cache.
+ *
+ * If the cache is performing badly, then we can't afford
+ * to promote much without causing performance to drop below that
+ * of the origin device.
+ *
+ * If the cache is performing well, then we don't need to promote
+ * much. If it isn't broken, don't fix it.
+ *
+ * If the cache is middling then we promote more.
+ *
+ * This scheme reminds me of a graph of entropy vs probability of a
+ * binary variable.
+ */
+ static unsigned table[] = {1, 1, 1, 2, 4, 6, 7, 8, 7, 6, 4, 4, 3, 3, 2, 2, 1};
+
+ unsigned hits = mq->cache_stats.hits;
+ unsigned misses = mq->cache_stats.misses;
+ unsigned index = safe_div(hits << 4u, hits + misses);
+ return table[index];
+}
+
+static void update_promote_levels(struct smq_policy *mq)
+{
+ /*
+ * If there are unused cache entries then we want to be really
+ * eager to promote.
+ */
+ unsigned threshold_level = allocator_empty(&mq->cache_alloc) ?
+ default_promote_level(mq) : (NR_HOTSPOT_LEVELS / 2u);
+
+ /*
+ * If the hotspot queue is performing badly then we have little
+ * confidence that we know which blocks to promote. So we cut down
+ * the amount of promotions.
+ */
+ switch (stats_assess(&mq->hotspot_stats)) {
+ case Q_POOR:
+ threshold_level /= 4u;
+ break;
+
+ case Q_FAIR:
+ threshold_level /= 2u;
+ break;
+
+ case Q_WELL:
+ break;
+ }
+
+ mq->read_promote_level = NR_HOTSPOT_LEVELS - threshold_level;
+ mq->write_promote_level = (NR_HOTSPOT_LEVELS - threshold_level) + 2u;
+}
+
+/*
+ * If the hotspot queue is performing badly, then we try and move entries
+ * around more quickly.
+ */
+static void update_level_jump(struct smq_policy *mq)
+{
+ switch (stats_assess(&mq->hotspot_stats)) {
+ case Q_POOR:
+ mq->hotspot_level_jump = 4u;
+ break;
+
+ case Q_FAIR:
+ mq->hotspot_level_jump = 2u;
+ break;
+
+ case Q_WELL:
+ mq->hotspot_level_jump = 1u;
+ break;
+ }
+}
+
+static void end_hotspot_period(struct smq_policy *mq)
+{
+ clear_bitset(mq->hotspot_hit_bits, mq->nr_hotspot_blocks);
+ update_promote_levels(mq);
+
+ if (time_after(jiffies, mq->next_hotspot_period)) {
+ update_level_jump(mq);
+ q_redistribute(&mq->hotspot);
+ stats_reset(&mq->hotspot_stats);
+ mq->next_hotspot_period = jiffies + HOTSPOT_UPDATE_PERIOD;
+ }
+}
+
+static void end_cache_period(struct smq_policy *mq)
+{
+ if (time_after(jiffies, mq->next_cache_period)) {
+ clear_bitset(mq->cache_hit_bits, from_cblock(mq->cache_size));
+
+ q_redistribute(&mq->dirty);
+ q_redistribute(&mq->clean);
+ stats_reset(&mq->cache_stats);
+
+ mq->next_cache_period = jiffies + CACHE_UPDATE_PERIOD;
+ }
+}
+
+static int demote_cblock(struct smq_policy *mq,
+ struct policy_locker *locker,
+ dm_oblock_t *oblock)
+{
+ struct entry *demoted = q_peek(&mq->clean, mq->clean.nr_levels, false);
+ if (!demoted)
+ /*
+ * We could get a block from mq->dirty, but that
+ * would add extra latency to the triggering bio as it
+ * waits for the writeback. Better to not promote this
+ * time and hope there's a clean block next time this block
+ * is hit.
+ */
+ return -ENOSPC;
+
+ if (locker->fn(locker, demoted->oblock))
+ /*
+ * We couldn't lock this block.
+ */
+ return -EBUSY;
+
+ del(mq, demoted);
+ *oblock = demoted->oblock;
+ free_entry(&mq->cache_alloc, demoted);
+
+ return 0;
+}
+
+enum promote_result {
+ PROMOTE_NOT,
+ PROMOTE_TEMPORARY,
+ PROMOTE_PERMANENT
+};
+
+/*
+ * Converts a boolean into a promote result.
+ */
+static enum promote_result maybe_promote(bool promote)
+{
+ return promote ? PROMOTE_PERMANENT : PROMOTE_NOT;
+}
+
+static enum promote_result should_promote(struct smq_policy *mq, struct entry *hs_e, struct bio *bio,
+ bool fast_promote)
+{
+ if (bio_data_dir(bio) == WRITE) {
+ if (!allocator_empty(&mq->cache_alloc) && fast_promote)
+ return PROMOTE_TEMPORARY;
+
+ else
+ return maybe_promote(hs_e->level >= mq->write_promote_level);
+ } else
+ return maybe_promote(hs_e->level >= mq->read_promote_level);
+}
+
+static void insert_in_cache(struct smq_policy *mq, dm_oblock_t oblock,
+ struct policy_locker *locker,
+ struct policy_result *result, enum promote_result pr)
+{
+ int r;
+ struct entry *e;
+
+ if (allocator_empty(&mq->cache_alloc)) {
+ result->op = POLICY_REPLACE;
+ r = demote_cblock(mq, locker, &result->old_oblock);
+ if (r) {
+ result->op = POLICY_MISS;
+ return;
+ }
+
+ } else
+ result->op = POLICY_NEW;
+
+ e = alloc_entry(&mq->cache_alloc);
+ BUG_ON(!e);
+ e->oblock = oblock;
+
+ if (pr == PROMOTE_TEMPORARY)
+ push(mq, e);
+ else
+ push_new(mq, e);
+
+ result->cblock = infer_cblock(mq, e);
+}
+
+static dm_oblock_t to_hblock(struct smq_policy *mq, dm_oblock_t b)
+{
+ sector_t r = from_oblock(b);
+ (void) sector_div(r, mq->cache_blocks_per_hotspot_block);
+ return to_oblock(r);
+}
+
+static struct entry *update_hotspot_queue(struct smq_policy *mq, dm_oblock_t b, struct bio *bio)
+{
+ unsigned hi;
+ dm_oblock_t hb = to_hblock(mq, b);
+ struct entry *e = h_lookup(&mq->hotspot_table, hb);
+
+ if (e) {
+ stats_level_accessed(&mq->hotspot_stats, e->level);
+
+ hi = get_index(&mq->hotspot_alloc, e);
+ q_requeue(&mq->hotspot, e,
+ test_and_set_bit(hi, mq->hotspot_hit_bits) ?
+ 0u : mq->hotspot_level_jump);
+
+ } else {
+ stats_miss(&mq->hotspot_stats);
+
+ e = alloc_entry(&mq->hotspot_alloc);
+ if (!e) {
+ e = q_pop(&mq->hotspot);
+ if (e) {
+ h_remove(&mq->hotspot_table, e);
+ hi = get_index(&mq->hotspot_alloc, e);
+ clear_bit(hi, mq->hotspot_hit_bits);
+ }
+
+ }
+
+ if (e) {
+ e->oblock = hb;
+ q_push(&mq->hotspot, e);
+ h_insert(&mq->hotspot_table, e);
+ }
+ }
+
+ return e;
+}
+
+/*
+ * Looks the oblock up in the hash table, then decides whether to put in
+ * pre_cache, or cache etc.
+ */
+static int map(struct smq_policy *mq, struct bio *bio, dm_oblock_t oblock,
+ bool can_migrate, bool fast_promote,
+ struct policy_locker *locker, struct policy_result *result)
+{
+ struct entry *e, *hs_e;
+ enum promote_result pr;
+
+ hs_e = update_hotspot_queue(mq, oblock, bio);
+
+ e = h_lookup(&mq->table, oblock);
+ if (e) {
+ stats_level_accessed(&mq->cache_stats, e->level);
+
+ requeue(mq, e);
+ result->op = POLICY_HIT;
+ result->cblock = infer_cblock(mq, e);
+
+ } else {
+ stats_miss(&mq->cache_stats);
+
+ pr = should_promote(mq, hs_e, bio, fast_promote);
+ if (pr == PROMOTE_NOT)
+ result->op = POLICY_MISS;
+
+ else {
+ if (!can_migrate) {
+ result->op = POLICY_MISS;
+ return -EWOULDBLOCK;
+ }
+
+ insert_in_cache(mq, oblock, locker, result, pr);
+ }
+ }
+
+ return 0;
+}
+
+/*----------------------------------------------------------------*/
+
+/*
+ * Public interface, via the policy struct. See dm-cache-policy.h for a
+ * description of these.
+ */
+
+static struct smq_policy *to_smq_policy(struct dm_cache_policy *p)
+{
+ return container_of(p, struct smq_policy, policy);
+}
+
+static void smq_destroy(struct dm_cache_policy *p)
+{
+ struct smq_policy *mq = to_smq_policy(p);
+
+ h_exit(&mq->hotspot_table);
+ h_exit(&mq->table);
+ free_bitset(mq->hotspot_hit_bits);
+ free_bitset(mq->cache_hit_bits);
+ space_exit(&mq->es);
+ kfree(mq);
+}
+
+static int smq_map(struct dm_cache_policy *p, dm_oblock_t oblock,
+ bool can_block, bool can_migrate, bool fast_promote,
+ struct bio *bio, struct policy_locker *locker,
+ struct policy_result *result)
+{
+ int r;
+ unsigned long flags;
+ struct smq_policy *mq = to_smq_policy(p);
+
+ result->op = POLICY_MISS;
+
+ spin_lock_irqsave(&mq->lock, flags);
+ r = map(mq, bio, oblock, can_migrate, fast_promote, locker, result);
+ spin_unlock_irqrestore(&mq->lock, flags);
+
+ return r;
+}
+
+static int smq_lookup(struct dm_cache_policy *p, dm_oblock_t oblock, dm_cblock_t *cblock)
+{
+ int r;
+ unsigned long flags;
+ struct smq_policy *mq = to_smq_policy(p);
+ struct entry *e;
+
+ spin_lock_irqsave(&mq->lock, flags);
+ e = h_lookup(&mq->table, oblock);
+ if (e) {
+ *cblock = infer_cblock(mq, e);
+ r = 0;
+ } else
+ r = -ENOENT;
+ spin_unlock_irqrestore(&mq->lock, flags);
+
+ return r;
+}
+
+static void __smq_set_clear_dirty(struct smq_policy *mq, dm_oblock_t oblock, bool set)
+{
+ struct entry *e;
+
+ e = h_lookup(&mq->table, oblock);
+ BUG_ON(!e);
+
+ del(mq, e);
+ e->dirty = set;
+ push(mq, e);
+}
+
+static void smq_set_dirty(struct dm_cache_policy *p, dm_oblock_t oblock)
+{
+ unsigned long flags;
+ struct smq_policy *mq = to_smq_policy(p);
+
+ spin_lock_irqsave(&mq->lock, flags);
+ __smq_set_clear_dirty(mq, oblock, true);
+ spin_unlock_irqrestore(&mq->lock, flags);
+}
+
+static void smq_clear_dirty(struct dm_cache_policy *p, dm_oblock_t oblock)
+{
+ struct smq_policy *mq = to_smq_policy(p);
+ unsigned long flags;
+
+ spin_lock_irqsave(&mq->lock, flags);
+ __smq_set_clear_dirty(mq, oblock, false);
+ spin_unlock_irqrestore(&mq->lock, flags);
+}
+
+static int smq_load_mapping(struct dm_cache_policy *p,
+ dm_oblock_t oblock, dm_cblock_t cblock,
+ uint32_t hint, bool hint_valid)
+{
+ struct smq_policy *mq = to_smq_policy(p);
+ struct entry *e;
+
+ e = alloc_particular_entry(&mq->cache_alloc, from_cblock(cblock));
+ e->oblock = oblock;
+ e->dirty = false; /* this gets corrected in a minute */
+ e->level = hint_valid ? min(hint, NR_CACHE_LEVELS - 1) : 1;
+ push(mq, e);
+
+ return 0;
+}
+
+static int smq_save_hints(struct smq_policy *mq, struct queue *q,
+ policy_walk_fn fn, void *context)
+{
+ int r;
+ unsigned level;
+ struct entry *e;
+
+ for (level = 0; level < q->nr_levels; level++)
+ for (e = l_head(q->es, q->qs + level); e; e = l_next(q->es, e)) {
+ if (!e->sentinel) {
+ r = fn(context, infer_cblock(mq, e),
+ e->oblock, e->level);
+ if (r)
+ return r;
+ }
+ }
+
+ return 0;
+}
+
+static int smq_walk_mappings(struct dm_cache_policy *p, policy_walk_fn fn,
+ void *context)
+{
+ struct smq_policy *mq = to_smq_policy(p);
+ int r = 0;
+
+ /*
+ * We don't need to lock here since this method is only called once
+ * the IO has stopped.
+ */
+ r = smq_save_hints(mq, &mq->clean, fn, context);
+ if (!r)
+ r = smq_save_hints(mq, &mq->dirty, fn, context);
+
+ return r;
+}
+
+static void __remove_mapping(struct smq_policy *mq, dm_oblock_t oblock)
+{
+ struct entry *e;
+
+ e = h_lookup(&mq->table, oblock);
+ BUG_ON(!e);
+
+ del(mq, e);
+ free_entry(&mq->cache_alloc, e);
+}
+
+static void smq_remove_mapping(struct dm_cache_policy *p, dm_oblock_t oblock)
+{
+ struct smq_policy *mq = to_smq_policy(p);
+ unsigned long flags;
+
+ spin_lock_irqsave(&mq->lock, flags);
+ __remove_mapping(mq, oblock);
+ spin_unlock_irqrestore(&mq->lock, flags);
+}
+
+static int __remove_cblock(struct smq_policy *mq, dm_cblock_t cblock)
+{
+ struct entry *e = get_entry(&mq->cache_alloc, from_cblock(cblock));
+
+ if (!e || !e->allocated)
+ return -ENODATA;
+
+ del(mq, e);
+ free_entry(&mq->cache_alloc, e);
+
+ return 0;
+}
+
+static int smq_remove_cblock(struct dm_cache_policy *p, dm_cblock_t cblock)
+{
+ int r;
+ unsigned long flags;
+ struct smq_policy *mq = to_smq_policy(p);
+
+ spin_lock_irqsave(&mq->lock, flags);
+ r = __remove_cblock(mq, cblock);
+ spin_unlock_irqrestore(&mq->lock, flags);
+
+ return r;
+}
+
+
+#define CLEAN_TARGET_CRITICAL 5u /* percent */
+
+static bool clean_target_met(struct smq_policy *mq, bool critical)
+{
+ if (critical) {
+ /*
+ * Cache entries may not be populated. So we're cannot rely on the
+ * size of the clean queue.
+ */
+ unsigned nr_clean = from_cblock(mq->cache_size) - q_size(&mq->dirty);
+ unsigned target = from_cblock(mq->cache_size) * CLEAN_TARGET_CRITICAL / 100u;
+
+ return nr_clean >= target;
+ } else
+ return !q_size(&mq->dirty);
+}
+
+static int __smq_writeback_work(struct smq_policy *mq, dm_oblock_t *oblock,
+ dm_cblock_t *cblock, bool critical_only)
+{
+ struct entry *e = NULL;
+ bool target_met = clean_target_met(mq, critical_only);
+
+ if (critical_only)
+ /*
+ * Always try and keep the bottom level clean.
+ */
+ e = pop_old(mq, &mq->dirty, target_met ? 1u : mq->dirty.nr_levels);
+
+ else
+ e = pop_old(mq, &mq->dirty, mq->dirty.nr_levels);
+
+ if (!e)
+ return -ENODATA;
+
+ *oblock = e->oblock;
+ *cblock = infer_cblock(mq, e);
+ e->dirty = false;
+ push_new(mq, e);
+
+ return 0;
+}
+
+static int smq_writeback_work(struct dm_cache_policy *p, dm_oblock_t *oblock,
+ dm_cblock_t *cblock, bool critical_only)
+{
+ int r;
+ unsigned long flags;
+ struct smq_policy *mq = to_smq_policy(p);
+
+ spin_lock_irqsave(&mq->lock, flags);
+ r = __smq_writeback_work(mq, oblock, cblock, critical_only);
+ spin_unlock_irqrestore(&mq->lock, flags);
+
+ return r;
+}
+
+static void __force_mapping(struct smq_policy *mq,
+ dm_oblock_t current_oblock, dm_oblock_t new_oblock)
+{
+ struct entry *e = h_lookup(&mq->table, current_oblock);
+
+ if (e) {
+ del(mq, e);
+ e->oblock = new_oblock;
+ e->dirty = true;
+ push(mq, e);
+ }
+}
+
+static void smq_force_mapping(struct dm_cache_policy *p,
+ dm_oblock_t current_oblock, dm_oblock_t new_oblock)
+{
+ unsigned long flags;
+ struct smq_policy *mq = to_smq_policy(p);
+
+ spin_lock_irqsave(&mq->lock, flags);
+ __force_mapping(mq, current_oblock, new_oblock);
+ spin_unlock_irqrestore(&mq->lock, flags);
+}
+
+static dm_cblock_t smq_residency(struct dm_cache_policy *p)
+{
+ dm_cblock_t r;
+ unsigned long flags;
+ struct smq_policy *mq = to_smq_policy(p);
+
+ spin_lock_irqsave(&mq->lock, flags);
+ r = to_cblock(mq->cache_alloc.nr_allocated);
+ spin_unlock_irqrestore(&mq->lock, flags);
+
+ return r;
+}
+
+static void smq_tick(struct dm_cache_policy *p, bool can_block)
+{
+ struct smq_policy *mq = to_smq_policy(p);
+ unsigned long flags;
+
+ spin_lock_irqsave(&mq->lock, flags);
+ mq->tick++;
+ update_sentinels(mq);
+ end_hotspot_period(mq);
+ end_cache_period(mq);
+ spin_unlock_irqrestore(&mq->lock, flags);
+}
+
+/* Init the policy plugin interface function pointers. */
+static void init_policy_functions(struct smq_policy *mq)
+{
+ mq->policy.destroy = smq_destroy;
+ mq->policy.map = smq_map;
+ mq->policy.lookup = smq_lookup;
+ mq->policy.set_dirty = smq_set_dirty;
+ mq->policy.clear_dirty = smq_clear_dirty;
+ mq->policy.load_mapping = smq_load_mapping;
+ mq->policy.walk_mappings = smq_walk_mappings;
+ mq->policy.remove_mapping = smq_remove_mapping;
+ mq->policy.remove_cblock = smq_remove_cblock;
+ mq->policy.writeback_work = smq_writeback_work;
+ mq->policy.force_mapping = smq_force_mapping;
+ mq->policy.residency = smq_residency;
+ mq->policy.tick = smq_tick;
+}
+
+static bool too_many_hotspot_blocks(sector_t origin_size,
+ sector_t hotspot_block_size,
+ unsigned nr_hotspot_blocks)
+{
+ return (hotspot_block_size * nr_hotspot_blocks) > origin_size;
+}
+
+static void calc_hotspot_params(sector_t origin_size,
+ sector_t cache_block_size,
+ unsigned nr_cache_blocks,
+ sector_t *hotspot_block_size,
+ unsigned *nr_hotspot_blocks)
+{
+ *hotspot_block_size = cache_block_size * 16u;
+ *nr_hotspot_blocks = max(nr_cache_blocks / 4u, 1024u);
+
+ while ((*hotspot_block_size > cache_block_size) &&
+ too_many_hotspot_blocks(origin_size, *hotspot_block_size, *nr_hotspot_blocks))
+ *hotspot_block_size /= 2u;
+}
+
+static struct dm_cache_policy *smq_create(dm_cblock_t cache_size,
+ sector_t origin_size,
+ sector_t cache_block_size)
+{
+ unsigned i;
+ unsigned nr_sentinels_per_queue = 2u * NR_CACHE_LEVELS;
+ unsigned total_sentinels = 2u * nr_sentinels_per_queue;
+ struct smq_policy *mq = kzalloc(sizeof(*mq), GFP_KERNEL);
+
+ if (!mq)
+ return NULL;
+
+ init_policy_functions(mq);
+ mq->cache_size = cache_size;
+ mq->cache_block_size = cache_block_size;
+
+ calc_hotspot_params(origin_size, cache_block_size, from_cblock(cache_size),
+ &mq->hotspot_block_size, &mq->nr_hotspot_blocks);
+
+ mq->cache_blocks_per_hotspot_block = div64_u64(mq->hotspot_block_size, mq->cache_block_size);
+ mq->hotspot_level_jump = 1u;
+ if (space_init(&mq->es, total_sentinels + mq->nr_hotspot_blocks + from_cblock(cache_size))) {
+ DMERR("couldn't initialize entry space");
+ goto bad_pool_init;
+ }
+
+ init_allocator(&mq->writeback_sentinel_alloc, &mq->es, 0, nr_sentinels_per_queue);
+ for (i = 0; i < nr_sentinels_per_queue; i++)
+ get_entry(&mq->writeback_sentinel_alloc, i)->sentinel = true;
+
+ init_allocator(&mq->demote_sentinel_alloc, &mq->es, nr_sentinels_per_queue, total_sentinels);
+ for (i = 0; i < nr_sentinels_per_queue; i++)
+ get_entry(&mq->demote_sentinel_alloc, i)->sentinel = true;
+
+ init_allocator(&mq->hotspot_alloc, &mq->es, total_sentinels,
+ total_sentinels + mq->nr_hotspot_blocks);
+
+ init_allocator(&mq->cache_alloc, &mq->es,
+ total_sentinels + mq->nr_hotspot_blocks,
+ total_sentinels + mq->nr_hotspot_blocks + from_cblock(cache_size));
+
+ mq->hotspot_hit_bits = alloc_bitset(mq->nr_hotspot_blocks);
+ if (!mq->hotspot_hit_bits) {
+ DMERR("couldn't allocate hotspot hit bitset");
+ goto bad_hotspot_hit_bits;
+ }
+ clear_bitset(mq->hotspot_hit_bits, mq->nr_hotspot_blocks);
+
+ if (from_cblock(cache_size)) {
+ mq->cache_hit_bits = alloc_bitset(from_cblock(cache_size));
+ if (!mq->cache_hit_bits) {
+ DMERR("couldn't allocate cache hit bitset");
+ goto bad_cache_hit_bits;
+ }
+ clear_bitset(mq->cache_hit_bits, from_cblock(mq->cache_size));
+ } else
+ mq->cache_hit_bits = NULL;
+
+ mq->tick = 0;
+ spin_lock_init(&mq->lock);
+
+ q_init(&mq->hotspot, &mq->es, NR_HOTSPOT_LEVELS);
+ mq->hotspot.nr_top_levels = 8;
+ mq->hotspot.nr_in_top_levels = min(mq->nr_hotspot_blocks / NR_HOTSPOT_LEVELS,
+ from_cblock(mq->cache_size) / mq->cache_blocks_per_hotspot_block);
+
+ q_init(&mq->clean, &mq->es, NR_CACHE_LEVELS);
+ q_init(&mq->dirty, &mq->es, NR_CACHE_LEVELS);
+
+ stats_init(&mq->hotspot_stats, NR_HOTSPOT_LEVELS);
+ stats_init(&mq->cache_stats, NR_CACHE_LEVELS);
+
+ if (h_init(&mq->table, &mq->es, from_cblock(cache_size)))
+ goto bad_alloc_table;
+
+ if (h_init(&mq->hotspot_table, &mq->es, mq->nr_hotspot_blocks))
+ goto bad_alloc_hotspot_table;
+
+ sentinels_init(mq);
+ mq->write_promote_level = mq->read_promote_level = NR_HOTSPOT_LEVELS;
+
+ mq->next_hotspot_period = jiffies;
+ mq->next_cache_period = jiffies;
+
+ return &mq->policy;
+
+bad_alloc_hotspot_table:
+ h_exit(&mq->table);
+bad_alloc_table:
+ free_bitset(mq->cache_hit_bits);
+bad_cache_hit_bits:
+ free_bitset(mq->hotspot_hit_bits);
+bad_hotspot_hit_bits:
+ space_exit(&mq->es);
+bad_pool_init:
+ kfree(mq);
+
+ return NULL;
+}
+
+/*----------------------------------------------------------------*/
+
+static struct dm_cache_policy_type smq_policy_type = {
+ .name = "smq",
+ .version = {1, 0, 0},
+ .hint_size = 4,
+ .owner = THIS_MODULE,
+ .create = smq_create
+};
+
+static struct dm_cache_policy_type default_policy_type = {
+ .name = "default",
+ .version = {1, 4, 0},
+ .hint_size = 4,
+ .owner = THIS_MODULE,
+ .create = smq_create,
+ .real = &smq_policy_type
+};
+
+static int __init smq_init(void)
+{
+ int r;
+
+ r = dm_cache_policy_register(&smq_policy_type);
+ if (r) {
+ DMERR("register failed %d", r);
+ return -ENOMEM;
+ }
+
+ r = dm_cache_policy_register(&default_policy_type);
+ if (r) {
+ DMERR("register failed (as default) %d", r);
+ dm_cache_policy_unregister(&smq_policy_type);
+ return -ENOMEM;
+ }
+
+ return 0;
+}
+
+static void __exit smq_exit(void)
+{
+ dm_cache_policy_unregister(&smq_policy_type);
+ dm_cache_policy_unregister(&default_policy_type);
+}
+
+module_init(smq_init);
+module_exit(smq_exit);
+
+MODULE_AUTHOR("Joe Thornber <dm-devel@redhat.com>");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("smq cache policy");
+
+MODULE_ALIAS("dm-cache-default");
Code Review / kvmfornfv.git / blobdiff