+++ /dev/null
-/*
- * Copyright (C) 2012 Red Hat. All rights reserved.
- *
- * This file is released under the GPL.
- */
-
-#include "dm-cache-policy.h"
-#include "dm.h"
-
-#include <linux/hash.h>
-#include <linux/jiffies.h>
-#include <linux/module.h>
-#include <linux/mutex.h>
-#include <linux/slab.h>
-#include <linux/vmalloc.h>
-
-#define DM_MSG_PREFIX "cache-policy-mq"
-
-static struct kmem_cache *mq_entry_cache;
-
-/*----------------------------------------------------------------*/
-
-static unsigned next_power(unsigned n, unsigned min)
-{
- return roundup_pow_of_two(max(n, min));
-}
-
-/*----------------------------------------------------------------*/
-
-/*
- * Large, sequential ios are probably better left on the origin device since
- * spindles tend to have good bandwidth.
- *
- * The io_tracker tries to spot when the io is in one of these sequential
- * modes.
- *
- * Two thresholds to switch between random and sequential io mode are defaulting
- * as follows and can be adjusted via the constructor and message interfaces.
- */
-#define RANDOM_THRESHOLD_DEFAULT 4
-#define SEQUENTIAL_THRESHOLD_DEFAULT 512
-
-enum io_pattern {
- PATTERN_SEQUENTIAL,
- PATTERN_RANDOM
-};
-
-struct io_tracker {
- enum io_pattern pattern;
-
- unsigned nr_seq_samples;
- unsigned nr_rand_samples;
- unsigned thresholds[2];
-
- dm_oblock_t last_end_oblock;
-};
-
-static void iot_init(struct io_tracker *t,
- int sequential_threshold, int random_threshold)
-{
- t->pattern = PATTERN_RANDOM;
- t->nr_seq_samples = 0;
- t->nr_rand_samples = 0;
- t->last_end_oblock = 0;
- t->thresholds[PATTERN_RANDOM] = random_threshold;
- t->thresholds[PATTERN_SEQUENTIAL] = sequential_threshold;
-}
-
-static enum io_pattern iot_pattern(struct io_tracker *t)
-{
- return t->pattern;
-}
-
-static void iot_update_stats(struct io_tracker *t, struct bio *bio)
-{
- if (bio->bi_iter.bi_sector == from_oblock(t->last_end_oblock) + 1)
- t->nr_seq_samples++;
- else {
- /*
- * Just one non-sequential IO is enough to reset the
- * counters.
- */
- if (t->nr_seq_samples) {
- t->nr_seq_samples = 0;
- t->nr_rand_samples = 0;
- }
-
- t->nr_rand_samples++;
- }
-
- t->last_end_oblock = to_oblock(bio_end_sector(bio) - 1);
-}
-
-static void iot_check_for_pattern_switch(struct io_tracker *t)
-{
- switch (t->pattern) {
- case PATTERN_SEQUENTIAL:
- if (t->nr_rand_samples >= t->thresholds[PATTERN_RANDOM]) {
- t->pattern = PATTERN_RANDOM;
- t->nr_seq_samples = t->nr_rand_samples = 0;
- }
- break;
-
- case PATTERN_RANDOM:
- if (t->nr_seq_samples >= t->thresholds[PATTERN_SEQUENTIAL]) {
- t->pattern = PATTERN_SEQUENTIAL;
- t->nr_seq_samples = t->nr_rand_samples = 0;
- }
- break;
- }
-}
-
-static void iot_examine_bio(struct io_tracker *t, struct bio *bio)
-{
- iot_update_stats(t, bio);
- iot_check_for_pattern_switch(t);
-}
-
-/*----------------------------------------------------------------*/
-
-
-/*
- * This queue is divided up into different levels. Allowing us to push
- * entries to the back of any of the levels. Think of it as a partially
- * sorted queue.
- */
-#define NR_QUEUE_LEVELS 16u
-#define NR_SENTINELS NR_QUEUE_LEVELS * 3
-
-#define WRITEBACK_PERIOD HZ
-
-struct queue {
- unsigned nr_elts;
- bool current_writeback_sentinels;
- unsigned long next_writeback;
- struct list_head qs[NR_QUEUE_LEVELS];
- struct list_head sentinels[NR_SENTINELS];
-};
-
-static void queue_init(struct queue *q)
-{
- unsigned i;
-
- q->nr_elts = 0;
- q->current_writeback_sentinels = false;
- q->next_writeback = 0;
- for (i = 0; i < NR_QUEUE_LEVELS; i++) {
- INIT_LIST_HEAD(q->qs + i);
- INIT_LIST_HEAD(q->sentinels + i);
- INIT_LIST_HEAD(q->sentinels + NR_QUEUE_LEVELS + i);
- INIT_LIST_HEAD(q->sentinels + (2 * NR_QUEUE_LEVELS) + i);
- }
-}
-
-static unsigned queue_size(struct queue *q)
-{
- return q->nr_elts;
-}
-
-static bool queue_empty(struct queue *q)
-{
- return q->nr_elts == 0;
-}
-
-/*
- * Insert an entry to the back of the given level.
- */
-static void queue_push(struct queue *q, unsigned level, struct list_head *elt)
-{
- q->nr_elts++;
- list_add_tail(elt, q->qs + level);
-}
-
-static void queue_remove(struct queue *q, struct list_head *elt)
-{
- q->nr_elts--;
- list_del(elt);
-}
-
-static bool is_sentinel(struct queue *q, struct list_head *h)
-{
- return (h >= q->sentinels) && (h < (q->sentinels + NR_SENTINELS));
-}
-
-/*
- * Gives us the oldest entry of the lowest popoulated level. If the first
- * level is emptied then we shift down one level.
- */
-static struct list_head *queue_peek(struct queue *q)
-{
- unsigned level;
- struct list_head *h;
-
- for (level = 0; level < NR_QUEUE_LEVELS; level++)
- list_for_each(h, q->qs + level)
- if (!is_sentinel(q, h))
- return h;
-
- return NULL;
-}
-
-static struct list_head *queue_pop(struct queue *q)
-{
- struct list_head *r = queue_peek(q);
-
- if (r) {
- q->nr_elts--;
- list_del(r);
- }
-
- return r;
-}
-
-/*
- * Pops an entry from a level that is not past a sentinel.
- */
-static struct list_head *queue_pop_old(struct queue *q)
-{
- unsigned level;
- struct list_head *h;
-
- for (level = 0; level < NR_QUEUE_LEVELS; level++)
- list_for_each(h, q->qs + level) {
- if (is_sentinel(q, h))
- break;
-
- q->nr_elts--;
- list_del(h);
- return h;
- }
-
- return NULL;
-}
-
-static struct list_head *list_pop(struct list_head *lh)
-{
- struct list_head *r = lh->next;
-
- BUG_ON(!r);
- list_del_init(r);
-
- return r;
-}
-
-static struct list_head *writeback_sentinel(struct queue *q, unsigned level)
-{
- if (q->current_writeback_sentinels)
- return q->sentinels + NR_QUEUE_LEVELS + level;
- else
- return q->sentinels + 2 * NR_QUEUE_LEVELS + level;
-}
-
-static void queue_update_writeback_sentinels(struct queue *q)
-{
- unsigned i;
- struct list_head *h;
-
- if (time_after(jiffies, q->next_writeback)) {
- for (i = 0; i < NR_QUEUE_LEVELS; i++) {
- h = writeback_sentinel(q, i);
- list_del(h);
- list_add_tail(h, q->qs + i);
- }
-
- q->next_writeback = jiffies + WRITEBACK_PERIOD;
- q->current_writeback_sentinels = !q->current_writeback_sentinels;
- }
-}
-
-/*
- * Sometimes we want to iterate through entries that have been pushed since
- * a certain event. We use sentinel entries on the queues to delimit these
- * 'tick' events.
- */
-static void queue_tick(struct queue *q)
-{
- unsigned i;
-
- for (i = 0; i < NR_QUEUE_LEVELS; i++) {
- list_del(q->sentinels + i);
- list_add_tail(q->sentinels + i, q->qs + i);
- }
-}
-
-typedef void (*iter_fn)(struct list_head *, void *);
-static void queue_iterate_tick(struct queue *q, iter_fn fn, void *context)
-{
- unsigned i;
- struct list_head *h;
-
- for (i = 0; i < NR_QUEUE_LEVELS; i++) {
- list_for_each_prev(h, q->qs + i) {
- if (is_sentinel(q, h))
- break;
-
- fn(h, context);
- }
- }
-}
-
-/*----------------------------------------------------------------*/
-
-/*
- * Describes a cache entry. Used in both the cache and the pre_cache.
- */
-struct entry {
- struct hlist_node hlist;
- struct list_head list;
- dm_oblock_t oblock;
-
- /*
- * FIXME: pack these better
- */
- bool dirty:1;
- unsigned hit_count;
-};
-
-/*
- * Rather than storing the cblock in an entry, we allocate all entries in
- * an array, and infer the cblock from the entry position.
- *
- * Free entries are linked together into a list.
- */
-struct entry_pool {
- struct entry *entries, *entries_end;
- struct list_head free;
- unsigned nr_allocated;
-};
-
-static int epool_init(struct entry_pool *ep, unsigned nr_entries)
-{
- unsigned i;
-
- ep->entries = vzalloc(sizeof(struct entry) * nr_entries);
- if (!ep->entries)
- return -ENOMEM;
-
- ep->entries_end = ep->entries + nr_entries;
-
- INIT_LIST_HEAD(&ep->free);
- for (i = 0; i < nr_entries; i++)
- list_add(&ep->entries[i].list, &ep->free);
-
- ep->nr_allocated = 0;
-
- return 0;
-}
-
-static void epool_exit(struct entry_pool *ep)
-{
- vfree(ep->entries);
-}
-
-static struct entry *alloc_entry(struct entry_pool *ep)
-{
- struct entry *e;
-
- if (list_empty(&ep->free))
- return NULL;
-
- e = list_entry(list_pop(&ep->free), struct entry, list);
- INIT_LIST_HEAD(&e->list);
- INIT_HLIST_NODE(&e->hlist);
- ep->nr_allocated++;
-
- return e;
-}
-
-/*
- * This assumes the cblock hasn't already been allocated.
- */
-static struct entry *alloc_particular_entry(struct entry_pool *ep, dm_cblock_t cblock)
-{
- struct entry *e = ep->entries + from_cblock(cblock);
-
- list_del_init(&e->list);
- INIT_HLIST_NODE(&e->hlist);
- ep->nr_allocated++;
-
- return e;
-}
-
-static void free_entry(struct entry_pool *ep, struct entry *e)
-{
- BUG_ON(!ep->nr_allocated);
- ep->nr_allocated--;
- INIT_HLIST_NODE(&e->hlist);
- list_add(&e->list, &ep->free);
-}
-
-/*
- * Returns NULL if the entry is free.
- */
-static struct entry *epool_find(struct entry_pool *ep, dm_cblock_t cblock)
-{
- struct entry *e = ep->entries + from_cblock(cblock);
- return !hlist_unhashed(&e->hlist) ? e : NULL;
-}
-
-static bool epool_empty(struct entry_pool *ep)
-{
- return list_empty(&ep->free);
-}
-
-static bool in_pool(struct entry_pool *ep, struct entry *e)
-{
- return e >= ep->entries && e < ep->entries_end;
-}
-
-static dm_cblock_t infer_cblock(struct entry_pool *ep, struct entry *e)
-{
- return to_cblock(e - ep->entries);
-}
-
-/*----------------------------------------------------------------*/
-
-struct mq_policy {
- struct dm_cache_policy policy;
-
- /* protects everything */
- struct mutex lock;
- dm_cblock_t cache_size;
- struct io_tracker tracker;
-
- /*
- * Entries come from two pools, one of pre-cache entries, and one
- * for the cache proper.
- */
- struct entry_pool pre_cache_pool;
- struct entry_pool cache_pool;
-
- /*
- * We maintain three queues of entries. The cache proper,
- * consisting of a clean and dirty queue, contains the currently
- * active mappings. Whereas the pre_cache tracks blocks that
- * are being hit frequently and potential candidates for promotion
- * to the cache.
- */
- struct queue pre_cache;
- struct queue cache_clean;
- struct queue cache_dirty;
-
- /*
- * Keeps track of time, incremented by the core. We use this to
- * avoid attributing multiple hits within the same tick.
- *
- * Access to tick_protected should be done with the spin lock held.
- * It's copied to tick at the start of the map function (within the
- * mutex).
- */
- spinlock_t tick_lock;
- unsigned tick_protected;
- unsigned tick;
-
- /*
- * A count of the number of times the map function has been called
- * and found an entry in the pre_cache or cache. Currently used to
- * calculate the generation.
- */
- unsigned hit_count;
-
- /*
- * A generation is a longish period that is used to trigger some
- * book keeping effects. eg, decrementing hit counts on entries.
- * This is needed to allow the cache to evolve as io patterns
- * change.
- */
- unsigned generation;
- unsigned generation_period; /* in lookups (will probably change) */
-
- unsigned discard_promote_adjustment;
- unsigned read_promote_adjustment;
- unsigned write_promote_adjustment;
-
- /*
- * The hash table allows us to quickly find an entry by origin
- * block. Both pre_cache and cache entries are in here.
- */
- unsigned nr_buckets;
- dm_block_t hash_bits;
- struct hlist_head *table;
-};
-
-#define DEFAULT_DISCARD_PROMOTE_ADJUSTMENT 1
-#define DEFAULT_READ_PROMOTE_ADJUSTMENT 4
-#define DEFAULT_WRITE_PROMOTE_ADJUSTMENT 8
-#define DISCOURAGE_DEMOTING_DIRTY_THRESHOLD 128
-
-/*----------------------------------------------------------------*/
-
-/*
- * Simple hash table implementation. Should replace with the standard hash
- * table that's making its way upstream.
- */
-static void hash_insert(struct mq_policy *mq, struct entry *e)
-{
- unsigned h = hash_64(from_oblock(e->oblock), mq->hash_bits);
-
- hlist_add_head(&e->hlist, mq->table + h);
-}
-
-static struct entry *hash_lookup(struct mq_policy *mq, dm_oblock_t oblock)
-{
- unsigned h = hash_64(from_oblock(oblock), mq->hash_bits);
- struct hlist_head *bucket = mq->table + h;
- struct entry *e;
-
- hlist_for_each_entry(e, bucket, hlist)
- if (e->oblock == oblock) {
- hlist_del(&e->hlist);
- hlist_add_head(&e->hlist, bucket);
- return e;
- }
-
- return NULL;
-}
-
-static void hash_remove(struct entry *e)
-{
- hlist_del(&e->hlist);
-}
-
-/*----------------------------------------------------------------*/
-
-static bool any_free_cblocks(struct mq_policy *mq)
-{
- return !epool_empty(&mq->cache_pool);
-}
-
-static bool any_clean_cblocks(struct mq_policy *mq)
-{
- return !queue_empty(&mq->cache_clean);
-}
-
-/*----------------------------------------------------------------*/
-
-/*
- * Now we get to the meat of the policy. This section deals with deciding
- * when to to add entries to the pre_cache and cache, and move between
- * them.
- */
-
-/*
- * The queue level is based on the log2 of the hit count.
- */
-static unsigned queue_level(struct entry *e)
-{
- return min((unsigned) ilog2(e->hit_count), NR_QUEUE_LEVELS - 1u);
-}
-
-static bool in_cache(struct mq_policy *mq, struct entry *e)
-{
- return in_pool(&mq->cache_pool, e);
-}
-
-/*
- * Inserts the entry into the pre_cache or the cache. Ensures the cache
- * block is marked as allocated if necc. Inserts into the hash table.
- * Sets the tick which records when the entry was last moved about.
- */
-static void push(struct mq_policy *mq, struct entry *e)
-{
- hash_insert(mq, e);
-
- if (in_cache(mq, e))
- queue_push(e->dirty ? &mq->cache_dirty : &mq->cache_clean,
- queue_level(e), &e->list);
- else
- queue_push(&mq->pre_cache, queue_level(e), &e->list);
-}
-
-/*
- * Removes an entry from pre_cache or cache. Removes from the hash table.
- */
-static void del(struct mq_policy *mq, struct entry *e)
-{
- if (in_cache(mq, e))
- queue_remove(e->dirty ? &mq->cache_dirty : &mq->cache_clean, &e->list);
- else
- queue_remove(&mq->pre_cache, &e->list);
-
- hash_remove(e);
-}
-
-/*
- * Like del, except it removes the first entry in the queue (ie. the least
- * recently used).
- */
-static struct entry *pop(struct mq_policy *mq, struct queue *q)
-{
- struct entry *e;
- struct list_head *h = queue_pop(q);
-
- if (!h)
- return NULL;
-
- e = container_of(h, struct entry, list);
- hash_remove(e);
-
- return e;
-}
-
-static struct entry *pop_old(struct mq_policy *mq, struct queue *q)
-{
- struct entry *e;
- struct list_head *h = queue_pop_old(q);
-
- if (!h)
- return NULL;
-
- e = container_of(h, struct entry, list);
- hash_remove(e);
-
- return e;
-}
-
-static struct entry *peek(struct queue *q)
-{
- struct list_head *h = queue_peek(q);
- return h ? container_of(h, struct entry, list) : NULL;
-}
-
-/*
- * The promotion threshold is adjusted every generation. As are the counts
- * of the entries.
- *
- * At the moment the threshold is taken by averaging the hit counts of some
- * of the entries in the cache (the first 20 entries across all levels in
- * ascending order, giving preference to the clean entries at each level).
- *
- * We can be much cleverer than this though. For example, each promotion
- * could bump up the threshold helping to prevent churn. Much more to do
- * here.
- */
-
-#define MAX_TO_AVERAGE 20
-
-static void check_generation(struct mq_policy *mq)
-{
- unsigned total = 0, nr = 0, count = 0, level;
- struct list_head *head;
- struct entry *e;
-
- if ((mq->hit_count >= mq->generation_period) && (epool_empty(&mq->cache_pool))) {
- mq->hit_count = 0;
- mq->generation++;
-
- for (level = 0; level < NR_QUEUE_LEVELS && count < MAX_TO_AVERAGE; level++) {
- head = mq->cache_clean.qs + level;
- list_for_each_entry(e, head, list) {
- nr++;
- total += e->hit_count;
-
- if (++count >= MAX_TO_AVERAGE)
- break;
- }
-
- head = mq->cache_dirty.qs + level;
- list_for_each_entry(e, head, list) {
- nr++;
- total += e->hit_count;
-
- if (++count >= MAX_TO_AVERAGE)
- break;
- }
- }
- }
-}
-
-/*
- * Whenever we use an entry we bump up it's hit counter, and push it to the
- * back to it's current level.
- */
-static void requeue(struct mq_policy *mq, struct entry *e)
-{
- check_generation(mq);
- del(mq, e);
- push(mq, e);
-}
-
-/*
- * Demote the least recently used entry from the cache to the pre_cache.
- * Returns the new cache entry to use, and the old origin block it was
- * mapped to.
- *
- * We drop the hit count on the demoted entry back to 1 to stop it bouncing
- * straight back into the cache if it's subsequently hit. There are
- * various options here, and more experimentation would be good:
- *
- * - just forget about the demoted entry completely (ie. don't insert it
- into the pre_cache).
- * - divide the hit count rather that setting to some hard coded value.
- * - set the hit count to a hard coded value other than 1, eg, is it better
- * if it goes in at level 2?
- */
-static int demote_cblock(struct mq_policy *mq,
- struct policy_locker *locker, dm_oblock_t *oblock)
-{
- struct entry *demoted = peek(&mq->cache_clean);
-
- if (!demoted)
- /*
- * We could get a block from mq->cache_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 the demoted block.
- */
- return -EBUSY;
-
- del(mq, demoted);
- *oblock = demoted->oblock;
- free_entry(&mq->cache_pool, demoted);
-
- /*
- * We used to put the demoted block into the pre-cache, but I think
- * it's simpler to just let it work it's way up from zero again.
- * Stops blocks flickering in and out of the cache.
- */
-
- return 0;
-}
-
-/*
- * Entries in the pre_cache whose hit count passes the promotion
- * threshold move to the cache proper. Working out the correct
- * value for the promotion_threshold is crucial to this policy.
- */
-static unsigned promote_threshold(struct mq_policy *mq)
-{
- struct entry *e;
-
- if (any_free_cblocks(mq))
- return 0;
-
- e = peek(&mq->cache_clean);
- if (e)
- return e->hit_count;
-
- e = peek(&mq->cache_dirty);
- if (e)
- return e->hit_count + DISCOURAGE_DEMOTING_DIRTY_THRESHOLD;
-
- /* This should never happen */
- return 0;
-}
-
-/*
- * We modify the basic promotion_threshold depending on the specific io.
- *
- * If the origin block has been discarded then there's no cost to copy it
- * to the cache.
- *
- * We bias towards reads, since they can be demoted at no cost if they
- * haven't been dirtied.
- */
-static unsigned adjusted_promote_threshold(struct mq_policy *mq,
- bool discarded_oblock, int data_dir)
-{
- if (data_dir == READ)
- return promote_threshold(mq) + mq->read_promote_adjustment;
-
- if (discarded_oblock && (any_free_cblocks(mq) || any_clean_cblocks(mq))) {
- /*
- * We don't need to do any copying at all, so give this a
- * very low threshold.
- */
- return mq->discard_promote_adjustment;
- }
-
- return promote_threshold(mq) + mq->write_promote_adjustment;
-}
-
-static bool should_promote(struct mq_policy *mq, struct entry *e,
- bool discarded_oblock, int data_dir)
-{
- return e->hit_count >=
- adjusted_promote_threshold(mq, discarded_oblock, data_dir);
-}
-
-static int cache_entry_found(struct mq_policy *mq,
- struct entry *e,
- struct policy_result *result)
-{
- requeue(mq, e);
-
- if (in_cache(mq, e)) {
- result->op = POLICY_HIT;
- result->cblock = infer_cblock(&mq->cache_pool, e);
- }
-
- return 0;
-}
-
-/*
- * Moves an entry from the pre_cache to the cache. The main work is
- * finding which cache block to use.
- */
-static int pre_cache_to_cache(struct mq_policy *mq, struct entry *e,
- struct policy_locker *locker,
- struct policy_result *result)
-{
- int r;
- struct entry *new_e;
-
- /* Ensure there's a free cblock in the cache */
- if (epool_empty(&mq->cache_pool)) {
- result->op = POLICY_REPLACE;
- r = demote_cblock(mq, locker, &result->old_oblock);
- if (r) {
- result->op = POLICY_MISS;
- return 0;
- }
-
- } else
- result->op = POLICY_NEW;
-
- new_e = alloc_entry(&mq->cache_pool);
- BUG_ON(!new_e);
-
- new_e->oblock = e->oblock;
- new_e->dirty = false;
- new_e->hit_count = e->hit_count;
-
- del(mq, e);
- free_entry(&mq->pre_cache_pool, e);
- push(mq, new_e);
-
- result->cblock = infer_cblock(&mq->cache_pool, new_e);
-
- return 0;
-}
-
-static int pre_cache_entry_found(struct mq_policy *mq, struct entry *e,
- bool can_migrate, bool discarded_oblock,
- int data_dir, struct policy_locker *locker,
- struct policy_result *result)
-{
- int r = 0;
-
- if (!should_promote(mq, e, discarded_oblock, data_dir)) {
- requeue(mq, e);
- result->op = POLICY_MISS;
-
- } else if (!can_migrate)
- r = -EWOULDBLOCK;
-
- else {
- requeue(mq, e);
- r = pre_cache_to_cache(mq, e, locker, result);
- }
-
- return r;
-}
-
-static void insert_in_pre_cache(struct mq_policy *mq,
- dm_oblock_t oblock)
-{
- struct entry *e = alloc_entry(&mq->pre_cache_pool);
-
- if (!e)
- /*
- * There's no spare entry structure, so we grab the least
- * used one from the pre_cache.
- */
- e = pop(mq, &mq->pre_cache);
-
- if (unlikely(!e)) {
- DMWARN("couldn't pop from pre cache");
- return;
- }
-
- e->dirty = false;
- e->oblock = oblock;
- e->hit_count = 1;
- push(mq, e);
-}
-
-static void insert_in_cache(struct mq_policy *mq, dm_oblock_t oblock,
- struct policy_locker *locker,
- struct policy_result *result)
-{
- int r;
- struct entry *e;
-
- if (epool_empty(&mq->cache_pool)) {
- result->op = POLICY_REPLACE;
- r = demote_cblock(mq, locker, &result->old_oblock);
- if (unlikely(r)) {
- result->op = POLICY_MISS;
- insert_in_pre_cache(mq, oblock);
- return;
- }
-
- /*
- * This will always succeed, since we've just demoted.
- */
- e = alloc_entry(&mq->cache_pool);
- BUG_ON(!e);
-
- } else {
- e = alloc_entry(&mq->cache_pool);
- result->op = POLICY_NEW;
- }
-
- e->oblock = oblock;
- e->dirty = false;
- e->hit_count = 1;
- push(mq, e);
-
- result->cblock = infer_cblock(&mq->cache_pool, e);
-}
-
-static int no_entry_found(struct mq_policy *mq, dm_oblock_t oblock,
- bool can_migrate, bool discarded_oblock,
- int data_dir, struct policy_locker *locker,
- struct policy_result *result)
-{
- if (adjusted_promote_threshold(mq, discarded_oblock, data_dir) <= 1) {
- if (can_migrate)
- insert_in_cache(mq, oblock, locker, result);
- else
- return -EWOULDBLOCK;
- } else {
- insert_in_pre_cache(mq, oblock);
- result->op = POLICY_MISS;
- }
-
- return 0;
-}
-
-/*
- * Looks the oblock up in the hash table, then decides whether to put in
- * pre_cache, or cache etc.
- */
-static int map(struct mq_policy *mq, dm_oblock_t oblock,
- bool can_migrate, bool discarded_oblock,
- int data_dir, struct policy_locker *locker,
- struct policy_result *result)
-{
- int r = 0;
- struct entry *e = hash_lookup(mq, oblock);
-
- if (e && in_cache(mq, e))
- r = cache_entry_found(mq, e, result);
-
- else if (mq->tracker.thresholds[PATTERN_SEQUENTIAL] &&
- iot_pattern(&mq->tracker) == PATTERN_SEQUENTIAL)
- result->op = POLICY_MISS;
-
- else if (e)
- r = pre_cache_entry_found(mq, e, can_migrate, discarded_oblock,
- data_dir, locker, result);
-
- else
- r = no_entry_found(mq, oblock, can_migrate, discarded_oblock,
- data_dir, locker, result);
-
- if (r == -EWOULDBLOCK)
- result->op = POLICY_MISS;
-
- return r;
-}
-
-/*----------------------------------------------------------------*/
-
-/*
- * Public interface, via the policy struct. See dm-cache-policy.h for a
- * description of these.
- */
-
-static struct mq_policy *to_mq_policy(struct dm_cache_policy *p)
-{
- return container_of(p, struct mq_policy, policy);
-}
-
-static void mq_destroy(struct dm_cache_policy *p)
-{
- struct mq_policy *mq = to_mq_policy(p);
-
- vfree(mq->table);
- epool_exit(&mq->cache_pool);
- epool_exit(&mq->pre_cache_pool);
- kfree(mq);
-}
-
-static void update_pre_cache_hits(struct list_head *h, void *context)
-{
- struct entry *e = container_of(h, struct entry, list);
- e->hit_count++;
-}
-
-static void update_cache_hits(struct list_head *h, void *context)
-{
- struct mq_policy *mq = context;
- struct entry *e = container_of(h, struct entry, list);
- e->hit_count++;
- mq->hit_count++;
-}
-
-static void copy_tick(struct mq_policy *mq)
-{
- unsigned long flags, tick;
-
- spin_lock_irqsave(&mq->tick_lock, flags);
- tick = mq->tick_protected;
- if (tick != mq->tick) {
- queue_iterate_tick(&mq->pre_cache, update_pre_cache_hits, mq);
- queue_iterate_tick(&mq->cache_dirty, update_cache_hits, mq);
- queue_iterate_tick(&mq->cache_clean, update_cache_hits, mq);
- mq->tick = tick;
- }
-
- queue_tick(&mq->pre_cache);
- queue_tick(&mq->cache_dirty);
- queue_tick(&mq->cache_clean);
- queue_update_writeback_sentinels(&mq->cache_dirty);
- spin_unlock_irqrestore(&mq->tick_lock, flags);
-}
-
-static int mq_map(struct dm_cache_policy *p, dm_oblock_t oblock,
- bool can_block, bool can_migrate, bool discarded_oblock,
- struct bio *bio, struct policy_locker *locker,
- struct policy_result *result)
-{
- int r;
- struct mq_policy *mq = to_mq_policy(p);
-
- result->op = POLICY_MISS;
-
- if (can_block)
- mutex_lock(&mq->lock);
- else if (!mutex_trylock(&mq->lock))
- return -EWOULDBLOCK;
-
- copy_tick(mq);
-
- iot_examine_bio(&mq->tracker, bio);
- r = map(mq, oblock, can_migrate, discarded_oblock,
- bio_data_dir(bio), locker, result);
-
- mutex_unlock(&mq->lock);
-
- return r;
-}
-
-static int mq_lookup(struct dm_cache_policy *p, dm_oblock_t oblock, dm_cblock_t *cblock)
-{
- int r;
- struct mq_policy *mq = to_mq_policy(p);
- struct entry *e;
-
- if (!mutex_trylock(&mq->lock))
- return -EWOULDBLOCK;
-
- e = hash_lookup(mq, oblock);
- if (e && in_cache(mq, e)) {
- *cblock = infer_cblock(&mq->cache_pool, e);
- r = 0;
- } else
- r = -ENOENT;
-
- mutex_unlock(&mq->lock);
-
- return r;
-}
-
-static void __mq_set_clear_dirty(struct mq_policy *mq, dm_oblock_t oblock, bool set)
-{
- struct entry *e;
-
- e = hash_lookup(mq, oblock);
- BUG_ON(!e || !in_cache(mq, e));
-
- del(mq, e);
- e->dirty = set;
- push(mq, e);
-}
-
-static void mq_set_dirty(struct dm_cache_policy *p, dm_oblock_t oblock)
-{
- struct mq_policy *mq = to_mq_policy(p);
-
- mutex_lock(&mq->lock);
- __mq_set_clear_dirty(mq, oblock, true);
- mutex_unlock(&mq->lock);
-}
-
-static void mq_clear_dirty(struct dm_cache_policy *p, dm_oblock_t oblock)
-{
- struct mq_policy *mq = to_mq_policy(p);
-
- mutex_lock(&mq->lock);
- __mq_set_clear_dirty(mq, oblock, false);
- mutex_unlock(&mq->lock);
-}
-
-static int mq_load_mapping(struct dm_cache_policy *p,
- dm_oblock_t oblock, dm_cblock_t cblock,
- uint32_t hint, bool hint_valid)
-{
- struct mq_policy *mq = to_mq_policy(p);
- struct entry *e;
-
- e = alloc_particular_entry(&mq->cache_pool, cblock);
- e->oblock = oblock;
- e->dirty = false; /* this gets corrected in a minute */
- e->hit_count = hint_valid ? hint : 1;
- push(mq, e);
-
- return 0;
-}
-
-static int mq_save_hints(struct mq_policy *mq, struct queue *q,
- policy_walk_fn fn, void *context)
-{
- int r;
- unsigned level;
- struct list_head *h;
- struct entry *e;
-
- for (level = 0; level < NR_QUEUE_LEVELS; level++)
- list_for_each(h, q->qs + level) {
- if (is_sentinel(q, h))
- continue;
-
- e = container_of(h, struct entry, list);
- r = fn(context, infer_cblock(&mq->cache_pool, e),
- e->oblock, e->hit_count);
- if (r)
- return r;
- }
-
- return 0;
-}
-
-static int mq_walk_mappings(struct dm_cache_policy *p, policy_walk_fn fn,
- void *context)
-{
- struct mq_policy *mq = to_mq_policy(p);
- int r = 0;
-
- mutex_lock(&mq->lock);
-
- r = mq_save_hints(mq, &mq->cache_clean, fn, context);
- if (!r)
- r = mq_save_hints(mq, &mq->cache_dirty, fn, context);
-
- mutex_unlock(&mq->lock);
-
- return r;
-}
-
-static void __remove_mapping(struct mq_policy *mq, dm_oblock_t oblock)
-{
- struct entry *e;
-
- e = hash_lookup(mq, oblock);
- BUG_ON(!e || !in_cache(mq, e));
-
- del(mq, e);
- free_entry(&mq->cache_pool, e);
-}
-
-static void mq_remove_mapping(struct dm_cache_policy *p, dm_oblock_t oblock)
-{
- struct mq_policy *mq = to_mq_policy(p);
-
- mutex_lock(&mq->lock);
- __remove_mapping(mq, oblock);
- mutex_unlock(&mq->lock);
-}
-
-static int __remove_cblock(struct mq_policy *mq, dm_cblock_t cblock)
-{
- struct entry *e = epool_find(&mq->cache_pool, cblock);
-
- if (!e)
- return -ENODATA;
-
- del(mq, e);
- free_entry(&mq->cache_pool, e);
-
- return 0;
-}
-
-static int mq_remove_cblock(struct dm_cache_policy *p, dm_cblock_t cblock)
-{
- int r;
- struct mq_policy *mq = to_mq_policy(p);
-
- mutex_lock(&mq->lock);
- r = __remove_cblock(mq, cblock);
- mutex_unlock(&mq->lock);
-
- return r;
-}
-
-#define CLEAN_TARGET_PERCENTAGE 25
-
-static bool clean_target_met(struct mq_policy *mq)
-{
- /*
- * 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) - queue_size(&mq->cache_dirty);
- unsigned target = from_cblock(mq->cache_size) * CLEAN_TARGET_PERCENTAGE / 100;
-
- return nr_clean >= target;
-}
-
-static int __mq_writeback_work(struct mq_policy *mq, dm_oblock_t *oblock,
- dm_cblock_t *cblock)
-{
- struct entry *e = pop_old(mq, &mq->cache_dirty);
-
- if (!e && !clean_target_met(mq))
- e = pop(mq, &mq->cache_dirty);
-
- if (!e)
- return -ENODATA;
-
- *oblock = e->oblock;
- *cblock = infer_cblock(&mq->cache_pool, e);
- e->dirty = false;
- push(mq, e);
-
- return 0;
-}
-
-static int mq_writeback_work(struct dm_cache_policy *p, dm_oblock_t *oblock,
- dm_cblock_t *cblock, bool critical_only)
-{
- int r;
- struct mq_policy *mq = to_mq_policy(p);
-
- mutex_lock(&mq->lock);
- r = __mq_writeback_work(mq, oblock, cblock);
- mutex_unlock(&mq->lock);
-
- return r;
-}
-
-static void __force_mapping(struct mq_policy *mq,
- dm_oblock_t current_oblock, dm_oblock_t new_oblock)
-{
- struct entry *e = hash_lookup(mq, current_oblock);
-
- if (e && in_cache(mq, e)) {
- del(mq, e);
- e->oblock = new_oblock;
- e->dirty = true;
- push(mq, e);
- }
-}
-
-static void mq_force_mapping(struct dm_cache_policy *p,
- dm_oblock_t current_oblock, dm_oblock_t new_oblock)
-{
- struct mq_policy *mq = to_mq_policy(p);
-
- mutex_lock(&mq->lock);
- __force_mapping(mq, current_oblock, new_oblock);
- mutex_unlock(&mq->lock);
-}
-
-static dm_cblock_t mq_residency(struct dm_cache_policy *p)
-{
- dm_cblock_t r;
- struct mq_policy *mq = to_mq_policy(p);
-
- mutex_lock(&mq->lock);
- r = to_cblock(mq->cache_pool.nr_allocated);
- mutex_unlock(&mq->lock);
-
- return r;
-}
-
-static void mq_tick(struct dm_cache_policy *p, bool can_block)
-{
- struct mq_policy *mq = to_mq_policy(p);
- unsigned long flags;
-
- spin_lock_irqsave(&mq->tick_lock, flags);
- mq->tick_protected++;
- spin_unlock_irqrestore(&mq->tick_lock, flags);
-
- if (can_block) {
- mutex_lock(&mq->lock);
- copy_tick(mq);
- mutex_unlock(&mq->lock);
- }
-}
-
-static int mq_set_config_value(struct dm_cache_policy *p,
- const char *key, const char *value)
-{
- struct mq_policy *mq = to_mq_policy(p);
- unsigned long tmp;
-
- if (kstrtoul(value, 10, &tmp))
- return -EINVAL;
-
- if (!strcasecmp(key, "random_threshold")) {
- mq->tracker.thresholds[PATTERN_RANDOM] = tmp;
-
- } else if (!strcasecmp(key, "sequential_threshold")) {
- mq->tracker.thresholds[PATTERN_SEQUENTIAL] = tmp;
-
- } else if (!strcasecmp(key, "discard_promote_adjustment"))
- mq->discard_promote_adjustment = tmp;
-
- else if (!strcasecmp(key, "read_promote_adjustment"))
- mq->read_promote_adjustment = tmp;
-
- else if (!strcasecmp(key, "write_promote_adjustment"))
- mq->write_promote_adjustment = tmp;
-
- else
- return -EINVAL;
-
- return 0;
-}
-
-static int mq_emit_config_values(struct dm_cache_policy *p, char *result,
- unsigned maxlen, ssize_t *sz_ptr)
-{
- ssize_t sz = *sz_ptr;
- struct mq_policy *mq = to_mq_policy(p);
-
- DMEMIT("10 random_threshold %u "
- "sequential_threshold %u "
- "discard_promote_adjustment %u "
- "read_promote_adjustment %u "
- "write_promote_adjustment %u ",
- mq->tracker.thresholds[PATTERN_RANDOM],
- mq->tracker.thresholds[PATTERN_SEQUENTIAL],
- mq->discard_promote_adjustment,
- mq->read_promote_adjustment,
- mq->write_promote_adjustment);
-
- *sz_ptr = sz;
- return 0;
-}
-
-/* Init the policy plugin interface function pointers. */
-static void init_policy_functions(struct mq_policy *mq)
-{
- mq->policy.destroy = mq_destroy;
- mq->policy.map = mq_map;
- mq->policy.lookup = mq_lookup;
- mq->policy.set_dirty = mq_set_dirty;
- mq->policy.clear_dirty = mq_clear_dirty;
- mq->policy.load_mapping = mq_load_mapping;
- mq->policy.walk_mappings = mq_walk_mappings;
- mq->policy.remove_mapping = mq_remove_mapping;
- mq->policy.remove_cblock = mq_remove_cblock;
- mq->policy.writeback_work = mq_writeback_work;
- mq->policy.force_mapping = mq_force_mapping;
- mq->policy.residency = mq_residency;
- mq->policy.tick = mq_tick;
- mq->policy.emit_config_values = mq_emit_config_values;
- mq->policy.set_config_value = mq_set_config_value;
-}
-
-static struct dm_cache_policy *mq_create(dm_cblock_t cache_size,
- sector_t origin_size,
- sector_t cache_block_size)
-{
- struct mq_policy *mq = kzalloc(sizeof(*mq), GFP_KERNEL);
-
- if (!mq)
- return NULL;
-
- init_policy_functions(mq);
- iot_init(&mq->tracker, SEQUENTIAL_THRESHOLD_DEFAULT, RANDOM_THRESHOLD_DEFAULT);
- mq->cache_size = cache_size;
-
- if (epool_init(&mq->pre_cache_pool, from_cblock(cache_size))) {
- DMERR("couldn't initialize pool of pre-cache entries");
- goto bad_pre_cache_init;
- }
-
- if (epool_init(&mq->cache_pool, from_cblock(cache_size))) {
- DMERR("couldn't initialize pool of cache entries");
- goto bad_cache_init;
- }
-
- mq->tick_protected = 0;
- mq->tick = 0;
- mq->hit_count = 0;
- mq->generation = 0;
- mq->discard_promote_adjustment = DEFAULT_DISCARD_PROMOTE_ADJUSTMENT;
- mq->read_promote_adjustment = DEFAULT_READ_PROMOTE_ADJUSTMENT;
- mq->write_promote_adjustment = DEFAULT_WRITE_PROMOTE_ADJUSTMENT;
- mutex_init(&mq->lock);
- spin_lock_init(&mq->tick_lock);
-
- queue_init(&mq->pre_cache);
- queue_init(&mq->cache_clean);
- queue_init(&mq->cache_dirty);
-
- mq->generation_period = max((unsigned) from_cblock(cache_size), 1024U);
-
- mq->nr_buckets = next_power(from_cblock(cache_size) / 2, 16);
- mq->hash_bits = __ffs(mq->nr_buckets);
- mq->table = vzalloc(sizeof(*mq->table) * mq->nr_buckets);
- if (!mq->table)
- goto bad_alloc_table;
-
- return &mq->policy;
-
-bad_alloc_table:
- epool_exit(&mq->cache_pool);
-bad_cache_init:
- epool_exit(&mq->pre_cache_pool);
-bad_pre_cache_init:
- kfree(mq);
-
- return NULL;
-}
-
-/*----------------------------------------------------------------*/
-
-static struct dm_cache_policy_type mq_policy_type = {
- .name = "mq",
- .version = {1, 4, 0},
- .hint_size = 4,
- .owner = THIS_MODULE,
- .create = mq_create
-};
-
-static int __init mq_init(void)
-{
- int r;
-
- mq_entry_cache = kmem_cache_create("dm_mq_policy_cache_entry",
- sizeof(struct entry),
- __alignof__(struct entry),
- 0, NULL);
- if (!mq_entry_cache)
- return -ENOMEM;
-
- r = dm_cache_policy_register(&mq_policy_type);
- if (r) {
- DMERR("register failed %d", r);
- kmem_cache_destroy(mq_entry_cache);
- return -ENOMEM;
- }
-
- return 0;
-}
-
-static void __exit mq_exit(void)
-{
- dm_cache_policy_unregister(&mq_policy_type);
-
- kmem_cache_destroy(mq_entry_cache);
-}
-
-module_init(mq_init);
-module_exit(mq_exit);
-
-MODULE_AUTHOR("Joe Thornber <dm-devel@redhat.com>");
-MODULE_LICENSE("GPL");
-MODULE_DESCRIPTION("mq cache policy");
projects / platform / kernel / linux-rpi.git / commitdiff