- 根目录:
- drivers
- md
- dm-cache-target.c
/*
* Copyright (C) 2012 Red Hat. All rights reserved.
*
* This file is released under the GPL.
*/
#include "dm.h"
#include "dm-bio-prison.h"
#include "dm-bio-record.h"
#include "dm-cache-metadata.h"
#include <linux/dm-io.h>
#include <linux/dm-kcopyd.h>
#include <linux/init.h>
#include <linux/mempool.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#define DM_MSG_PREFIX "cache"
DECLARE_DM_KCOPYD_THROTTLE_WITH_MODULE_PARM(cache_copy_throttle,
"A percentage of time allocated for copying to and/or from cache");
/*----------------------------------------------------------------*/
/*
* Glossary:
*
* oblock: index of an origin block
* cblock: index of a cache block
* promotion: movement of a block from origin to cache
* demotion: movement of a block from cache to origin
* migration: movement of a block between the origin and cache device,
* either direction
*/
/*----------------------------------------------------------------*/
static size_t bitset_size_in_bytes(unsigned nr_entries)
{
return sizeof(unsigned long) * dm_div_up(nr_entries, BITS_PER_LONG);
}
static unsigned long *alloc_bitset(unsigned nr_entries)
{
size_t s = bitset_size_in_bytes(nr_entries);
return vzalloc(s);
}
static void clear_bitset(void *bitset, unsigned nr_entries)
{
size_t s = bitset_size_in_bytes(nr_entries);
memset(bitset, 0, s);
}
static void free_bitset(unsigned long *bits)
{
vfree(bits);
}
/*----------------------------------------------------------------*/
#define PRISON_CELLS 1024
#define MIGRATION_POOL_SIZE 128
#define COMMIT_PERIOD HZ
#define MIGRATION_COUNT_WINDOW 10
/*
* The block size of the device holding cache data must be >= 32KB
*/
#define DATA_DEV_BLOCK_SIZE_MIN_SECTORS (32 * 1024 >> SECTOR_SHIFT)
/*
* FIXME: the cache is read/write for the time being.
*/
enum cache_mode {
CM_WRITE, /* metadata may be changed */
CM_READ_ONLY, /* metadata may not be changed */
};
struct cache_features {
enum cache_mode mode;
bool write_through:1;
};
struct cache_stats {
atomic_t read_hit;
atomic_t read_miss;
atomic_t write_hit;
atomic_t write_miss;
atomic_t demotion;
atomic_t promotion;
atomic_t copies_avoided;
atomic_t cache_cell_clash;
atomic_t commit_count;
atomic_t discard_count;
};
struct cache {
struct dm_target *ti;
struct dm_target_callbacks callbacks;
/*
* Metadata is written to this device.
*/
struct dm_dev *metadata_dev;
/*
* The slower of the two data devices. Typically a spindle.
*/
struct dm_dev *origin_dev;
/*
* The faster of the two data devices. Typically an SSD.
*/
struct dm_dev *cache_dev;
/*
* Cache features such as write-through.
*/
struct cache_features features;
/*
* Size of the origin device in _complete_ blocks and native sectors.
*/
dm_oblock_t origin_blocks;
sector_t origin_sectors;
/*
* Size of the cache device in blocks.
*/
dm_cblock_t cache_size;
/*
* Fields for converting from sectors to blocks.
*/
uint32_t sectors_per_block;
int sectors_per_block_shift;
struct dm_cache_metadata *cmd;
spinlock_t lock;
struct bio_list deferred_bios;
struct bio_list deferred_flush_bios;
struct bio_list deferred_writethrough_bios;
struct list_head quiesced_migrations;
struct list_head completed_migrations;
struct list_head need_commit_migrations;
sector_t migration_threshold;
atomic_t nr_migrations;
wait_queue_head_t migration_wait;
/*
* cache_size entries, dirty if set
*/
dm_cblock_t nr_dirty;
unsigned long *dirty_bitset;
/*
* origin_blocks entries, discarded if set.
*/
uint32_t discard_block_size; /* a power of 2 times sectors per block */
dm_dblock_t discard_nr_blocks;
unsigned long *discard_bitset;
struct dm_kcopyd_client *copier;
struct workqueue_struct *wq;
struct work_struct worker;
struct delayed_work waker;
unsigned long last_commit_jiffies;
struct dm_bio_prison *prison;
struct dm_deferred_set *all_io_ds;
mempool_t *migration_pool;
struct dm_cache_migration *next_migration;
struct dm_cache_policy *policy;
unsigned policy_nr_args;
bool need_tick_bio:1;
bool sized:1;
bool quiescing:1;
bool commit_requested:1;
bool loaded_mappings:1;
bool loaded_discards:1;
struct cache_stats stats;
/*
* Rather than reconstructing the table line for the status we just
* save it and regurgitate.
*/
unsigned nr_ctr_args;
const char **ctr_args;
};
struct per_bio_data {
bool tick:1;
unsigned req_nr:2;
struct dm_deferred_entry *all_io_entry;
/*
* writethrough fields. These MUST remain at the end of this
* structure and the 'cache' member must be the first as it
* is used to determine the offset of the writethrough fields.
*/
struct cache *cache;
dm_cblock_t cblock;
bio_end_io_t *saved_bi_end_io;
struct dm_bio_details bio_details;
};
struct dm_cache_migration {
struct list_head list;
struct cache *cache;
unsigned long start_jiffies;
dm_oblock_t old_oblock;
dm_oblock_t new_oblock;
dm_cblock_t cblock;
bool err:1;
bool writeback:1;
bool demote:1;
bool promote:1;
struct dm_bio_prison_cell *old_ocell;
struct dm_bio_prison_cell *new_ocell;
};
/*
* Processing a bio in the worker thread may require these memory
* allocations. We prealloc to avoid deadlocks (the same worker thread
* frees them back to the mempool).
*/
struct prealloc {
struct dm_cache_migration *mg;
struct dm_bio_prison_cell *cell1;
struct dm_bio_prison_cell *cell2;
};
static void wake_worker(struct cache *cache)
{
queue_work(cache->wq, &cache->worker);
}
/*----------------------------------------------------------------*/
static struct dm_bio_prison_cell *alloc_prison_cell(struct cache *cache)
{
/* FIXME: change to use a local slab. */
return dm_bio_prison_alloc_cell(cache->prison, GFP_NOWAIT);
}
static void free_prison_cell(struct cache *cache, struct dm_bio_prison_cell *cell)
{
dm_bio_prison_free_cell(cache->prison, cell);
}
static int prealloc_data_structs(struct cache *cache, struct prealloc *p)
{
if (!p->mg) {
p->mg = mempool_alloc(cache->migration_pool, GFP_NOWAIT);
if (!p->mg)
return -ENOMEM;
}
if (!p->cell1) {
p->cell1 = alloc_prison_cell(cache);
if (!p->cell1)
return -ENOMEM;
}
if (!p->cell2) {
p->cell2 = alloc_prison_cell(cache);
if (!p->cell2)
return -ENOMEM;
}
return 0;
}
static void prealloc_free_structs(struct cache *cache, struct prealloc *p)
{
if (p->cell2)
free_prison_cell(cache, p->cell2);
if (p->cell1)
free_prison_cell(cache, p->cell1);
if (p->mg)
mempool_free(p->mg, cache->migration_pool);
}
static struct dm_cache_migration *prealloc_get_migration(struct prealloc *p)
{
struct dm_cache_migration *mg = p->mg;
BUG_ON(!mg);
p->mg = NULL;
return mg;
}
/*
* You must have a cell within the prealloc struct to return. If not this
* function will BUG() rather than returning NULL.
*/
static struct dm_bio_prison_cell *prealloc_get_cell(struct prealloc *p)
{
struct dm_bio_prison_cell *r = NULL;
if (p->cell1) {
r = p->cell1;
p->cell1 = NULL;
} else if (p->cell2) {
r = p->cell2;
p->cell2 = NULL;
} else
BUG();
return r;
}
/*
* You can't have more than two cells in a prealloc struct. BUG() will be
* called if you try and overfill.
*/
static void prealloc_put_cell(struct prealloc *p, struct dm_bio_prison_cell *cell)
{
if (!p->cell2)
p->cell2 = cell;
else if (!p->cell1)
p->cell1 = cell;
else
BUG();
}
/*----------------------------------------------------------------*/
static void build_key(dm_oblock_t oblock, struct dm_cell_key *key)
{
key->virtual = 0;
key->dev = 0;
key->block = from_oblock(oblock);
}
/*
* The caller hands in a preallocated cell, and a free function for it.
* The cell will be freed if there's an error, or if it wasn't used because
* a cell with that key already exists.
*/
typedef void (*cell_free_fn)(void *context, struct dm_bio_prison_cell *cell);
static int bio_detain(struct cache *cache, dm_oblock_t oblock,
struct bio *bio, struct dm_bio_prison_cell *cell_prealloc,
cell_free_fn free_fn, void *free_context,
struct dm_bio_prison_cell **cell_result)
{
int r;
struct dm_cell_key key;
build_key(oblock, &key);
r = dm_bio_detain(cache->prison, &key, bio, cell_prealloc, cell_result);
if (r)
free_fn(free_context, cell_prealloc);
return r;
}
static int get_cell(struct cache *cache,
dm_oblock_t oblock,
struct prealloc *structs,
struct dm_bio_prison_cell **cell_result)
{
int r;
struct dm_cell_key key;
struct dm_bio_prison_cell *cell_prealloc;
cell_prealloc = prealloc_get_cell(structs);
build_key(oblock, &key);
r = dm_get_cell(cache->prison, &key, cell_prealloc, cell_result);
if (r)
prealloc_put_cell(structs, cell_prealloc);
return r;
}
/*----------------------------------------------------------------*/
static bool is_dirty(struct cache *cache, dm_cblock_t b)
{
return test_bit(from_cblock(b), cache->dirty_bitset);
}
static void set_dirty(struct cache *cache, dm_oblock_t oblock, dm_cblock_t cblock)
{
if (!test_and_set_bit(from_cblock(cblock), cache->dirty_bitset)) {
cache->nr_dirty = to_cblock(from_cblock(cache->nr_dirty) + 1);
policy_set_dirty(cache->policy, oblock);
}
}
static void clear_dirty(struct cache *cache, dm_oblock_t oblock, dm_cblock_t cblock)
{
if (test_and_clear_bit(from_cblock(cblock), cache->dirty_bitset)) {
policy_clear_dirty(cache->policy, oblock);
cache->nr_dirty = to_cblock(from_cblock(cache->nr_dirty) - 1);
if (!from_cblock(cache->nr_dirty))
dm_table_event(cache->ti->table);
}
}
/*----------------------------------------------------------------*/
static bool block_size_is_power_of_two(struct cache *cache)
{
return cache->sectors_per_block_shift >= 0;
}
static dm_block_t block_div(dm_block_t b, uint32_t n)
{
do_div(b, n);
return b;
}
static dm_dblock_t oblock_to_dblock(struct cache *cache, dm_oblock_t oblock)
{
uint32_t discard_blocks = cache->discard_block_size;
dm_block_t b = from_oblock(oblock);
if (!block_size_is_power_of_two(cache))
discard_blocks = discard_blocks / cache->sectors_per_block;
else
discard_blocks >>= cache->sectors_per_block_shift;
b = block_div(b, discard_blocks);
return to_dblock(b);
}
static void set_discard(struct cache *cache, dm_dblock_t b)
{
unsigned long flags;
atomic_inc(&cache->stats.discard_count);
spin_lock_irqsave(&cache->lock, flags);
set_bit(from_dblock(b), cache->discard_bitset);
spin_unlock_irqrestore(&cache->lock, flags);
}
static void clear_discard(struct cache *cache, dm_dblock_t b)
{
unsigned long flags;
spin_lock_irqsave(&cache->lock, flags);
clear_bit(from_dblock(b), cache->discard_bitset);
spin_unlock_irqrestore(&cache->lock, flags);
}
static bool is_discarded(struct cache *cache, dm_dblock_t b)
{
int r;
unsigned long flags;
spin_lock_irqsave(&cache->lock, flags);
r = test_bit(from_dblock(b), cache->discard_bitset);
spin_unlock_irqrestore(&cache->lock, flags);
return r;
}
static bool is_discarded_oblock(struct cache *cache, dm_oblock_t b)
{
int r;
unsigned long flags;
spin_lock_irqsave(&cache->lock, flags);
r = test_bit(from_dblock(oblock_to_dblock(cache, b)),
cache->discard_bitset);
spin_unlock_irqrestore(&cache->lock, flags);
return r;
}
/*----------------------------------------------------------------*/
static void load_stats(struct cache *cache)
{
struct dm_cache_statistics stats;
dm_cache_metadata_get_stats(cache->cmd, &stats);
atomic_set(&cache->stats.read_hit, stats.read_hits);
atomic_set(&cache->stats.read_miss, stats.read_misses);
atomic_set(&cache->stats.write_hit, stats.write_hits);
atomic_set(&cache->stats.write_miss, stats.write_misses);
}
static void save_stats(struct cache *cache)
{
struct dm_cache_statistics stats;
stats.read_hits = atomic_read(&cache->stats.read_hit);
stats.read_misses = atomic_read(&cache->stats.read_miss);
stats.write_hits = atomic_read(&cache->stats.write_hit);
stats.write_misses = atomic_read(&cache->stats.write_miss);
dm_cache_metadata_set_stats(cache->cmd, &stats);
}
/*----------------------------------------------------------------
* Per bio data
*--------------------------------------------------------------*/
/*
* If using writeback, leave out struct per_bio_data's writethrough fields.
*/
#define PB_DATA_SIZE_WB (offsetof(struct per_bio_data, cache))
#define PB_DATA_SIZE_WT (sizeof(struct per_bio_data))
static size_t get_per_bio_data_size(struct cache *cache)
{
return cache->features.write_through ? PB_DATA_SIZE_WT : PB_DATA_SIZE_WB;
}
static struct per_bio_data *get_per_bio_data(struct bio *bio, size_t data_size)
{
struct per_bio_data *pb = dm_per_bio_data(bio, data_size);
BUG_ON(!pb);
return pb;
}
static struct per_bio_data *init_per_bio_data(struct bio *bio, size_t data_size)
{
struct per_bio_data *pb = get_per_bio_data(bio, data_size);
pb->tick = false;
pb->req_nr = dm_bio_get_target_bio_nr(bio);
pb->all_io_entry = NULL;
return pb;
}
/*----------------------------------------------------------------
* Remapping
*--------------------------------------------------------------*/
static void remap_to_origin(struct cache *cache, struct bio *bio)
{
bio->bi_bdev = cache->origin_dev->bdev;
}
static void remap_to_cache(struct cache *cache, struct bio *bio,
dm_cblock_t cblock)
{
sector_t bi_sector = bio->bi_sector;
bio->bi_bdev = cache->cache_dev->bdev;
if (!block_size_is_power_of_two(cache))
bio->bi_sector = (from_cblock(cblock) * cache->sectors_per_block) +
sector_div(bi_sector, cache->sectors_per_block);
else
bio->bi_sector = (from_cblock(cblock) << cache->sectors_per_block_shift) |
(bi_sector & (cache->sectors_per_block - 1));
}
static void check_if_tick_bio_needed(struct cache *cache, struct bio *bio)
{
unsigned long flags;
size_t pb_data_size = get_per_bio_data_size(cache);
struct per_bio_data *pb = get_per_bio_data(bio, pb_data_size);
spin_lock_irqsave(&cache->lock, flags);
if (cache->need_tick_bio &&
!(bio->bi_rw & (REQ_FUA | REQ_FLUSH | REQ_DISCARD))) {
pb->tick = true;
cache->need_tick_bio = false;
}
spin_unlock_irqrestore(&cache->lock, flags);
}
static void remap_to_origin_clear_discard(struct cache *cache, struct bio *bio,
dm_oblock_t oblock)
{
check_if_tick_bio_needed(cache, bio);
remap_to_origin(cache, bio);
if (bio_data_dir(bio) == WRITE)
clear_discard(cache, oblock_to_dblock(cache, oblock));
}
static void remap_to_cache_dirty(struct cache *cache, struct bio *bio,
dm_oblock_t oblock, dm_cblock_t cblock)
{
remap_to_cache(cache, bio, cblock);
if (bio_data_dir(bio) == WRITE) {
set_dirty(cache, oblock, cblock);
clear_discard(cache, oblock_to_dblock(cache, oblock));
}
}
static dm_oblock_t get_bio_block(struct cache *cache, struct bio *bio)
{
sector_t block_nr = bio->bi_sector;
if (!block_size_is_power_of_two(cache))
(void) sector_div(block_nr, cache->sectors_per_block);
else
block_nr >>= cache->sectors_per_block_shift;
return to_oblock(block_nr);
}
static int bio_triggers_commit(struct cache *cache, struct bio *bio)
{
return bio->bi_rw & (REQ_FLUSH | REQ_FUA);
}
static void issue(struct cache *cache, struct bio *bio)
{
unsigned long flags;
if (!bio_triggers_commit(cache, bio)) {
generic_make_request(bio);
return;
}
/*
* Batch together any bios that trigger commits and then issue a
* single commit for them in do_worker().
*/
spin_lock_irqsave(&cache->lock, flags);
cache->commit_requested = true;
bio_list_add(&cache->deferred_flush_bios, bio);
spin_unlock_irqrestore(&cache->lock, flags);
}
static void defer_writethrough_bio(struct cache *cache, struct bio *bio)
{
unsigned long flags;
spin_lock_irqsave(&cache->lock, flags);
bio_list_add(&cache->deferred_writethrough_bios, bio);
spin_unlock_irqrestore(&cache->lock, flags);
wake_worker(cache);
}
static void writethrough_endio(struct bio *bio, int err)
{
struct per_bio_data *pb = get_per_bio_data(bio, PB_DATA_SIZE_WT);
bio->bi_end_io = pb->saved_bi_end_io;
if (err) {
bio_endio(bio, err);
return;
}
dm_bio_restore(&pb->bio_details, bio);
remap_to_cache(pb->cache, bio, pb->cblock);
/*
* We can't issue this bio directly, since we're in interrupt
* context. So it gets put on a bio list for processing by the
* worker thread.
*/
defer_writethrough_bio(pb->cache, bio);
}
/*
* When running in writethrough mode we need to send writes to clean blocks
* to both the cache and origin devices. In future we'd like to clone the
* bio and send them in parallel, but for now we're doing them in
* series as this is easier.
*/
static void remap_to_origin_then_cache(struct cache *cache, struct bio *bio,
dm_oblock_t oblock, dm_cblock_t cblock)
{
struct per_bio_data *pb = get_per_bio_data(bio, PB_DATA_SIZE_WT);
pb->cache = cache;
pb->cblock = cblock;
pb->saved_bi_end_io = bio->bi_end_io;
dm_bio_record(&pb->bio_details, bio);
bio->bi_end_io = writethrough_endio;
remap_to_origin_clear_discard(pb->cache, bio, oblock);
}
/*----------------------------------------------------------------
* Migration processing
*
* Migration covers moving data from the origin device to the cache, or
* vice versa.
*--------------------------------------------------------------*/
static void free_migration(struct dm_cache_migration *mg)
{
mempool_free(mg, mg->cache->migration_pool);
}
static void inc_nr_migrations(struct cache *cache)
{
atomic_inc(&cache->nr_migrations);
}
static void dec_nr_migrations(struct cache *cache)
{
atomic_dec(&cache->nr_migrations);
/*
* Wake the worker in case we're suspending the target.
*/
wake_up(&cache->migration_wait);
}
static void __cell_defer(struct cache *cache, struct dm_bio_prison_cell *cell,
bool holder)
{
(holder ? dm_cell_release : dm_cell_release_no_holder)
(cache->prison, cell, &cache->deferred_bios);
free_prison_cell(cache, cell);
}
static void cell_defer(struct cache *cache, struct dm_bio_prison_cell *cell,
bool holder)
{
unsigned long flags;
spin_lock_irqsave(&cache->lock, flags);
__cell_defer(cache, cell, holder);
spin_unlock_irqrestore(&cache->lock, flags);
wake_worker(cache);
}
static void cleanup_migration(struct dm_cache_migration *mg)
{
dec_nr_migrations(mg->cache);
free_migration(mg);
}
static void migration_failure(struct dm_cache_migration *mg)
{
struct cache *cache = mg->cache;
if (mg->writeback) {
DMWARN_LIMIT("writeback failed; couldn't copy block");
set_dirty(cache, mg->old_oblock, mg->cblock);
cell_defer(cache, mg->old_ocell, false);
} else if (mg->demote) {
DMWARN_LIMIT("demotion failed; couldn't copy block");
policy_force_mapping(cache->policy, mg->new_oblock, mg->old_oblock);
cell_defer(cache, mg->old_ocell, mg->promote ? 0 : 1);
if (mg->promote)
cell_defer(cache, mg->new_ocell, 1);
} else {
DMWARN_LIMIT("promotion failed; couldn't copy block");
policy_remove_mapping(cache->policy, mg->new_oblock);
cell_defer(cache, mg->new_ocell, 1);
}
cleanup_migration(mg);
}
static void migration_success_pre_commit(struct dm_cache_migration *mg)
{
unsigned long flags;
struct cache *cache = mg->cache;
if (mg->writeback) {
cell_defer(cache, mg->old_ocell, false);
clear_dirty(cache, mg->old_oblock, mg->cblock);
cleanup_migration(mg);
return;
} else if (mg->demote) {
if (dm_cache_remove_mapping(cache->cmd, mg->cblock)) {
DMWARN_LIMIT("demotion failed; couldn't update on disk metadata");
policy_force_mapping(cache->policy, mg->new_oblock,
mg->old_oblock);
if (mg->promote)
cell_defer(cache, mg->new_ocell, true);
cleanup_migration(mg);
return;
}
} else {
if (dm_cache_insert_mapping(cache->cmd, mg->cblock, mg->new_oblock)) {
DMWARN_LIMIT("promotion failed; couldn't update on disk metadata");
policy_remove_mapping(cache->policy, mg->new_oblock);
cleanup_migration(mg);
return;
}
}
spin_lock_irqsave(&cache->lock, flags);
list_add_tail(&mg->list, &cache->need_commit_migrations);
cache->commit_requested = true;
spin_unlock_irqrestore(&cache->lock, flags);
}
static void migration_success_post_commit(struct dm_cache_migration *mg)
{
unsigned long flags;
struct cache *cache = mg->cache;
if (mg->writeback) {
DMWARN("writeback unexpectedly triggered commit");
return;
} else if (mg->demote) {
cell_defer(cache, mg->old_ocell, mg->promote ? 0 : 1);
if (mg->promote) {
mg->demote = false;
spin_lock_irqsave(&cache->lock, flags);
list_add_tail(&mg->list, &cache->quiesced_migrations);
spin_unlock_irqrestore(&cache->lock, flags);
} else
cleanup_migration(mg);
} else {
cell_defer(cache, mg->new_ocell, true);
clear_dirty(cache, mg->new_oblock, mg->cblock);
cleanup_migration(mg);
}
}
static void copy_complete(int read_err, unsigned long write_err, void *context)
{
unsigned long flags;
struct dm_cache_migration *mg = (struct dm_cache_migration *) context;
struct cache *cache = mg->cache;
if (read_err || write_err)
mg->err = true;
spin_lock_irqsave(&cache->lock, flags);
list_add_tail(&mg->list, &cache->completed_migrations);
spin_unlock_irqrestore(&cache->lock, flags);
wake_worker(cache);
}
static void issue_copy_real(struct dm_cache_migration *mg)
{
int r;
struct dm_io_region o_region, c_region;
struct cache *cache = mg->cache;
o_region.bdev = cache->origin_dev->bdev;
o_region.count = cache->sectors_per_block;
c_region.bdev = cache->cache_dev->bdev;
c_region.sector = from_cblock(mg->cblock) * cache->sectors_per_block;
c_region.count = cache->sectors_per_block;
if (mg->writeback || mg->demote) {
/* demote */
o_region.sector = from_oblock(mg->old_oblock) * cache->sectors_per_block;
r = dm_kcopyd_copy(cache->copier, &c_region, 1, &o_region, 0, copy_complete, mg);
} else {
/* promote */
o_region.sector = from_oblock(mg->new_oblock) * cache->sectors_per_block;
r = dm_kcopyd_copy(cache->copier, &o_region, 1, &c_region, 0, copy_complete, mg);
}
if (r < 0)
migration_failure(mg);
}
static void avoid_copy(struct dm_cache_migration *mg)
{
atomic_inc(&mg->cache->stats.copies_avoided);
migration_success_pre_commit(mg);
}
static void issue_copy(struct dm_cache_migration *mg)
{
bool avoid;
struct cache *cache = mg->cache;
if (mg->writeback || mg->demote)
avoid = !is_dirty(cache, mg->cblock) ||
is_discarded_oblock(cache, mg->old_oblock);
else
avoid = is_discarded_oblock(cache, mg->new_oblock);
avoid ? avoid_copy(mg) : issue_copy_real(mg);
}
static void complete_migration(struct dm_cache_migration *mg)
{
if (mg->err)
migration_failure(mg);
else
migration_success_pre_commit(mg);
}
static void process_migrations(struct cache *cache, struct list_head *head,
void (*fn)(struct dm_cache_migration *))
{
unsigned long flags;
struct list_head list;
struct dm_cache_migration *mg, *tmp;
INIT_LIST_HEAD(&list);
spin_lock_irqsave(&cache->lock, flags);
list_splice_init(head, &list);
spin_unlock_irqrestore(&cache->lock, flags);
list_for_each_entry_safe(mg, tmp, &list, list)
fn(mg);
}
static void __queue_quiesced_migration(struct dm_cache_migration *mg)
{
list_add_tail(&mg->list, &mg->cache->quiesced_migrations);
}
static void queue_quiesced_migration(struct dm_cache_migration *mg)
{
unsigned long flags;
struct cache *cache = mg->cache;
spin_lock_irqsave(&cache->lock, flags);
__queue_quiesced_migration(mg);
spin_unlock_irqrestore(&cache->lock, flags);
wake_worker(cache);
}
static void queue_quiesced_migrations(struct cache *cache, struct list_head *work)
{
unsigned long flags;
struct dm_cache_migration *mg, *tmp;
spin_lock_irqsave(&cache->lock, flags);
list_for_each_entry_safe(mg, tmp, work, list)
__queue_quiesced_migration(mg);
spin_unlock_irqrestore(&cache->lock, flags);
wake_worker(cache);
}
static void check_for_quiesced_migrations(struct cache *cache,
struct per_bio_data *pb)
{
struct list_head work;
if (!pb->all_io_entry)
return;
INIT_LIST_HEAD(&work);
if (pb->all_io_entry)
dm_deferred_entry_dec(pb->all_io_entry, &work);
if (!list_empty(&work))
queue_quiesced_migrations(cache, &work);
}
static void quiesce_migration(struct dm_cache_migration *mg)
{
if (!dm_deferred_set_add_work(mg->cache->all_io_ds, &mg->list))
queue_quiesced_migration(mg);
}
static void promote(struct cache *cache, struct prealloc *structs,
dm_oblock_t oblock, dm_cblock_t cblock,
struct dm_bio_prison_cell *cell)
{
struct dm_cache_migration *mg = prealloc_get_migration(structs);
mg->err = false;
mg->writeback = false;
mg->demote = false;
mg->promote = true;
mg->cache = cache;
mg->new_oblock = oblock;
mg->cblock = cblock;
mg->old_ocell = NULL;
mg->new_ocell = cell;
mg->start_jiffies = jiffies;
inc_nr_migrations(cache);
quiesce_migration(mg);
}
static void writeback(struct cache *cache, struct prealloc *structs,
dm_oblock_t oblock, dm_cblock_t cblock,
struct dm_bio_prison_cell *cell)
{
struct dm_cache_migration *mg = prealloc_get_migration(structs);
mg->err = false;
mg->writeback = true;
mg->demote = false;
mg->promote = false;
mg->cache = cache;
mg->old_oblock = oblock;
mg->cblock = cblock;
mg->old_ocell = cell;
mg->new_ocell = NULL;
mg->start_jiffies = jiffies;
inc_nr_migrations(cache);
quiesce_migration(mg);
}
static void demote_then_promote(struct cache *cache, struct prealloc *structs,
dm_oblock_t old_oblock, dm_oblock_t new_oblock,
dm_cblock_t cblock,
struct dm_bio_prison_cell *old_ocell,
struct dm_bio_prison_cell *new_ocell)
{
struct dm_cache_migration *mg = prealloc_get_migration(structs);
mg->err = false;
mg->writeback = false;
mg->demote = true;
mg->promote = true;
mg->cache = cache;
mg->old_oblock = old_oblock;
mg->new_oblock = new_oblock;
mg->cblock = cblock;
mg->old_ocell = old_ocell;
mg->new_ocell = new_ocell;
mg->start_jiffies = jiffies;
inc_nr_migrations(cache);
quiesce_migration(mg);
}
/*----------------------------------------------------------------
* bio processing
*--------------------------------------------------------------*/
static void defer_bio(struct cache *cache, struct bio *bio)
{
unsigned long flags;
spin_lock_irqsave(&cache->lock, flags);
bio_list_add(&cache->deferred_bios, bio);
spin_unlock_irqrestore(&cache->lock, flags);
wake_worker(cache);
}
static void process_flush_bio(struct cache *cache, struct bio *bio)
{
size_t pb_data_size = get_per_bio_data_size(cache);
struct per_bio_data *pb = get_per_bio_data(bio, pb_data_size);
BUG_ON(bio->bi_size);
if (!pb->req_nr)
remap_to_origin(cache, bio);
else
remap_to_cache(cache, bio, 0);
issue(cache, bio);
}
/*
* People generally discard large parts of a device, eg, the whole device
* when formatting. Splitting these large discards up into cache block
* sized ios and then quiescing (always neccessary for discard) takes too
* long.
*
* We keep it simple, and allow any size of discard to come in, and just
* mark off blocks on the discard bitset. No passdown occurs!
*
* To implement passdown we need to change the bio_prison such that a cell
* can have a key that spans many blocks.
*/
static void process_discard_bio(struct cache *cache, struct bio *bio)
{
dm_block_t start_block = dm_sector_div_up(bio->bi_sector,
cache->discard_block_size);
dm_block_t end_block = bio->bi_sector + bio_sectors(bio);
dm_block_t b;
end_block = block_div(end_block, cache->discard_block_size);
for (b = start_block; b < end_block; b++)
set_discard(cache, to_dblock(b));
bio_endio(bio, 0);
}
static bool spare_migration_bandwidth(struct cache *cache)
{
sector_t current_volume = (atomic_read(&cache->nr_migrations) + 1) *
cache->sectors_per_block;
return current_volume < cache->migration_threshold;
}
static bool is_writethrough_io(struct cache *cache, struct bio *bio,
dm_cblock_t cblock)
{
return bio_data_dir(bio) == WRITE &&
cache->features.write_through && !is_dirty(cache, cblock);
}
static void inc_hit_counter(struct cache *cache, struct bio *bio)
{
atomic_inc(bio_data_dir(bio) == READ ?
&cache->stats.read_hit : &cache->stats.write_hit);
}
static void inc_miss_counter(struct cache *cache, struct bio *bio)
{
atomic_inc(bio_data_dir(bio) == READ ?
&cache->stats.read_miss : &cache->stats.write_miss);
}
static void process_bio(struct cache *cache, struct prealloc *structs,
struct bio *bio)
{
int r;
bool release_cell = true;
dm_oblock_t block = get_bio_block(cache, bio);
struct dm_bio_prison_cell *cell_prealloc, *old_ocell, *new_ocell;
struct policy_result lookup_result;
size_t pb_data_size = get_per_bio_data_size(cache);
struct per_bio_data *pb = get_per_bio_data(bio, pb_data_size);
bool discarded_block = is_discarded_oblock(cache, block);
bool can_migrate = discarded_block || spare_migration_bandwidth(cache);
/*
* Check to see if that block is currently migrating.
*/
cell_prealloc = prealloc_get_cell(structs);
r = bio_detain(cache, block, bio, cell_prealloc,
(cell_free_fn) prealloc_put_cell,
structs, &new_ocell);
if (r > 0)
return;
r = policy_map(cache->policy, block, true, can_migrate, discarded_block,
bio, &lookup_result);
if (r == -EWOULDBLOCK)
/* migration has been denied */
lookup_result.op = POLICY_MISS;
switch (lookup_result.op) {
case POLICY_HIT:
inc_hit_counter(cache, bio);
pb->all_io_entry = dm_deferred_entry_inc(cache->all_io_ds);
if (is_writethrough_io(cache, bio, lookup_result.cblock))
remap_to_origin_then_cache(cache, bio, block, lookup_result.cblock);
else
remap_to_cache_dirty(cache, bio, block, lookup_result.cblock);
issue(cache, bio);
break;
case POLICY_MISS:
inc_miss_counter(cache, bio);
pb->all_io_entry = dm_deferred_entry_inc(cache->all_io_ds);
remap_to_origin_clear_discard(cache, bio, block);
issue(cache, bio);
break;
case POLICY_NEW:
atomic_inc(&cache->stats.promotion);
promote(cache, structs, block, lookup_result.cblock, new_ocell);
release_cell = false;
break;
case POLICY_REPLACE:
cell_prealloc = prealloc_get_cell(structs);
r = bio_detain(cache, lookup_result.old_oblock, bio, cell_prealloc,
(cell_free_fn) prealloc_put_cell,
structs, &old_ocell);
if (r > 0) {
/*
* We have to be careful to avoid lock inversion of
* the cells. So we back off, and wait for the
* old_ocell to become free.
*/
policy_force_mapping(cache->policy, block,
lookup_result.old_oblock);
atomic_inc(&cache->stats.cache_cell_clash);
break;
}
atomic_inc(&cache->stats.demotion);
atomic_inc(&cache->stats.promotion);
demote_then_promote(cache, structs, lookup_result.old_oblock,
block, lookup_result.cblock,
old_ocell, new_ocell);
release_cell = false;
break;
default:
DMERR_LIMIT("%s: erroring bio, unknown policy op: %u", __func__,
(unsigned) lookup_result.op);
bio_io_error(bio);
}
if (release_cell)
cell_defer(cache, new_ocell, false);
}
static int need_commit_due_to_time(struct cache *cache)
{
return jiffies < cache->last_commit_jiffies ||
jiffies > cache->last_commit_jiffies + COMMIT_PERIOD;
}
static int commit_if_needed(struct cache *cache)
{
if (dm_cache_changed_this_transaction(cache->cmd) &&
(cache->commit_requested || need_commit_due_to_time(cache))) {
atomic_inc(&cache->stats.commit_count);
cache->last_commit_jiffies = jiffies;
cache->commit_requested = false;
return dm_cache_commit(cache->cmd, false);
}
return 0;
}
static void process_deferred_bios(struct cache *cache)
{
unsigned long flags;
struct bio_list bios;
struct bio *bio;
struct prealloc structs;
memset(&structs, 0, sizeof(structs));
bio_list_init(&bios);
spin_lock_irqsave(&cache->lock, flags);
bio_list_merge(&bios, &cache->deferred_bios);
bio_list_init(&cache->deferred_bios);
spin_unlock_irqrestore(&cache->lock, flags);
while (!bio_list_empty(&bios)) {
/*
* If we've got no free migration structs, and processing
* this bio might require one, we pause until there are some
* prepared mappings to process.
*/
if (prealloc_data_structs(cache, &structs)) {
spin_lock_irqsave(&cache->lock, flags);
bio_list_merge(&cache->deferred_bios, &bios);
spin_unlock_irqrestore(&cache->lock, flags);
break;
}
bio = bio_list_pop(&bios);
if (bio->bi_rw & REQ_FLUSH)
process_flush_bio(cache, bio);
else if (bio->bi_rw & REQ_DISCARD)
process_discard_bio(cache, bio);
else
process_bio(cache, &structs, bio);
}
prealloc_free_structs(cache, &structs);
}
static void process_deferred_flush_bios(struct cache *cache, bool submit_bios)
{
unsigned long flags;
struct bio_list bios;
struct bio *bio;
bio_list_init(&bios);
spin_lock_irqsave(&cache->lock, flags);
bio_list_merge(&bios, &cache->deferred_flush_bios);
bio_list_init(&cache->deferred_flush_bios);
spin_unlock_irqrestore(&cache->lock, flags);
while ((bio = bio_list_pop(&bios)))
submit_bios ? generic_make_request(bio) : bio_io_error(bio);
}
static void process_deferred_writethrough_bios(struct cache *cache)
{
unsigned long flags;
struct bio_list bios;
struct bio *bio;
bio_list_init(&bios);
spin_lock_irqsave(&cache->lock, flags);
bio_list_merge(&bios, &cache->deferred_writethrough_bios);
bio_list_init(&cache->deferred_writethrough_bios);
spin_unlock_irqrestore(&cache->lock, flags);
while ((bio = bio_list_pop(&bios)))
generic_make_request(bio);
}
static void writeback_some_dirty_blocks(struct cache *cache)
{
int r = 0;
dm_oblock_t oblock;
dm_cblock_t cblock;
struct prealloc structs;
struct dm_bio_prison_cell *old_ocell;
memset(&structs, 0, sizeof(structs));
while (spare_migration_bandwidth(cache)) {
if (prealloc_data_structs(cache, &structs))
break;
r = policy_writeback_work(cache->policy, &oblock, &cblock);
if (r)
break;
r = get_cell(cache, oblock, &structs, &old_ocell);
if (r) {
policy_set_dirty(cache->policy, oblock);
break;
}
writeback(cache, &structs, oblock, cblock, old_ocell);
}
prealloc_free_structs(cache, &structs);
}
/*----------------------------------------------------------------
* Main worker loop
*--------------------------------------------------------------*/
static void start_quiescing(struct cache *cache)
{
unsigned long flags;
spin_lock_irqsave(&cache->lock, flags);
cache->quiescing = 1;
spin_unlock_irqrestore(&cache->lock, flags);
}
static void stop_quiescing(struct cache *cache)
{
unsigned long flags;
spin_lock_irqsave(&cache->lock, flags);
cache->quiescing = 0;
spin_unlock_irqrestore(&cache->lock, flags);
}
static bool is_quiescing(struct cache *cache)
{
int r;
unsigned long flags;
spin_lock_irqsave(&cache->lock, flags);
r = cache->quiescing;
spin_unlock_irqrestore(&cache->lock, flags);
return r;
}
static void wait_for_migrations(struct cache *cache)
{
wait_event(cache->migration_wait, !atomic_read(&cache->nr_migrations));
}
static void stop_worker(struct cache *cache)
{
cancel_delayed_work(&cache->waker);
flush_workqueue(cache->wq);
}
static void requeue_deferred_io(struct cache *cache)
{
struct bio *bio;
struct bio_list bios;
bio_list_init(&bios);
bio_list_merge(&bios, &cache->deferred_bios);
bio_list_init(&cache->deferred_bios);
while ((bio = bio_list_pop(&bios)))
bio_endio(bio, DM_ENDIO_REQUEUE);
}
static int more_work(struct cache *cache)
{
if (is_quiescing(cache))
return !list_empty(&cache->quiesced_migrations) ||
!list_empty(&cache->completed_migrations) ||
!list_empty(&cache->need_commit_migrations);
else
return !bio_list_empty(&cache->deferred_bios) ||
!bio_list_empty(&cache->deferred_flush_bios) ||
!bio_list_empty(&cache->deferred_writethrough_bios) ||
!list_empty(&cache->quiesced_migrations) ||
!list_empty(&cache->completed_migrations) ||
!list_empty(&cache->need_commit_migrations);
}
static void do_worker(struct work_struct *ws)
{
struct cache *cache = container_of(ws, struct cache, worker);
do {
if (!is_quiescing(cache))
process_deferred_bios(cache);
process_migrations(cache, &cache->quiesced_migrations, issue_copy);
process_migrations(cache, &cache->completed_migrations, complete_migration);
writeback_some_dirty_blocks(cache);
process_deferred_writethrough_bios(cache);
if (commit_if_needed(cache)) {
process_deferred_flush_bios(cache, false);
/*
* FIXME: rollback metadata or just go into a
* failure mode and error everything
*/
} else {
process_deferred_flush_bios(cache, true);
process_migrations(cache, &cache->need_commit_migrations,
migration_success_post_commit);
}
} while (more_work(cache));
}
/*
* We want to commit periodically so that not too much
* unwritten metadata builds up.
*/
static void do_waker(struct work_struct *ws)
{
struct cache *cache = container_of(to_delayed_work(ws), struct cache, waker);
policy_tick(cache->policy);
wake_worker(cache);
queue_delayed_work(cache->wq, &cache->waker, COMMIT_PERIOD);
}
/*----------------------------------------------------------------*/
static int is_congested(struct dm_dev *dev, int bdi_bits)
{
struct request_queue *q = bdev_get_queue(dev->bdev);
return bdi_congested(&q->backing_dev_info, bdi_bits);
}
static int cache_is_congested(struct dm_target_callbacks *cb, int bdi_bits)
{
struct cache *cache = container_of(cb, struct cache, callbacks);
return is_congested(cache->origin_dev, bdi_bits) ||
is_congested(cache->cache_dev, bdi_bits);
}
/*----------------------------------------------------------------
* Target methods
*--------------------------------------------------------------*/
/*
* This function gets called on the error paths of the constructor, so we
* have to cope with a partially initialised struct.
*/
static void destroy(struct cache *cache)
{
unsigned i;
if (cache->next_migration)
mempool_free(cache->next_migration, cache->migration_pool);
if (cache->migration_pool)
mempool_destroy(cache->migration_pool);
if (cache->all_io_ds)
dm_deferred_set_destroy(cache->all_io_ds);
if (cache->prison)
dm_bio_prison_destroy(cache->prison);
if (cache->wq)
destroy_workqueue(cache->wq);
if (cache->dirty_bitset)
free_bitset(cache->dirty_bitset);
if (cache->discard_bitset)
free_bitset(cache->discard_bitset);
if (cache->copier)
dm_kcopyd_client_destroy(cache->copier);
if (cache->cmd)
dm_cache_metadata_close(cache->cmd);
if (cache->metadata_dev)
dm_put_device(cache->ti, cache->metadata_dev);
if (cache->origin_dev)
dm_put_device(cache->ti, cache->origin_dev);
if (cache->cache_dev)
dm_put_device(cache->ti, cache->cache_dev);
if (cache->policy)
dm_cache_policy_destroy(cache->policy);
for (i = 0; i < cache->nr_ctr_args ; i++)
kfree(cache->ctr_args[i]);
kfree(cache->ctr_args);
kfree(cache);
}
static void cache_dtr(struct dm_target *ti)
{
struct cache *cache = ti->private;
destroy(cache);
}
static sector_t get_dev_size(struct dm_dev *dev)
{
return i_size_read(dev->bdev->bd_inode) >> SECTOR_SHIFT;
}
/*----------------------------------------------------------------*/
/*
* Construct a cache device mapping.
*
* cache <metadata dev> <cache dev> <origin dev> <block size>
* <#feature args> [<feature arg>]*
* <policy> <#policy args> [<policy arg>]*
*
* metadata dev : fast device holding the persistent metadata
* cache dev : fast device holding cached data blocks
* origin dev : slow device holding original data blocks
* block size : cache unit size in sectors
*
* #feature args : number of feature arguments passed
* feature args : writethrough. (The default is writeback.)
*
* policy : the replacement policy to use
* #policy args : an even number of policy arguments corresponding
* to key/value pairs passed to the policy
* policy args : key/value pairs passed to the policy
* E.g. 'sequential_threshold 1024'
* See cache-policies.txt for details.
*
* Optional feature arguments are:
* writethrough : write through caching that prohibits cache block
* content from being different from origin block content.
* Without this argument, the default behaviour is to write
* back cache block contents later for performance reasons,
* so they may differ from the corresponding origin blocks.
*/
struct cache_args {
struct dm_target *ti;
struct dm_dev *metadata_dev;
struct dm_dev *cache_dev;
sector_t cache_sectors;
struct dm_dev *origin_dev;
sector_t origin_sectors;
uint32_t block_size;
const char *policy_name;
int policy_argc;
const char **policy_argv;
struct cache_features features;
};
static void destroy_cache_args(struct cache_args *ca)
{
if (ca->metadata_dev)
dm_put_device(ca->ti, ca->metadata_dev);
if (ca->cache_dev)
dm_put_device(ca->ti, ca->cache_dev);
if (ca->origin_dev)
dm_put_device(ca->ti, ca->origin_dev);
kfree(ca);
}
static bool at_least_one_arg(struct dm_arg_set *as, char **error)
{
if (!as->argc) {
*error = "Insufficient args";
return false;
}
return true;
}
static int parse_metadata_dev(struct cache_args *ca, struct dm_arg_set *as,
char **error)
{
int r;
sector_t metadata_dev_size;
char b[BDEVNAME_SIZE];
if (!at_least_one_arg(as, error))
return -EINVAL;
r = dm_get_device(ca->ti, dm_shift_arg(as), FMODE_READ | FMODE_WRITE,
&ca->metadata_dev);
if (r) {
*error = "Error opening metadata device";
return r;
}
metadata_dev_size = get_dev_size(ca->metadata_dev);
if (metadata_dev_size > DM_CACHE_METADATA_MAX_SECTORS_WARNING)
DMWARN("Metadata device %s is larger than %u sectors: excess space will not be used.",
bdevname(ca->metadata_dev->bdev, b), THIN_METADATA_MAX_SECTORS);
return 0;
}
static int parse_cache_dev(struct cache_args *ca, struct dm_arg_set *as,
char **error)
{
int r;
if (!at_least_one_arg(as, error))
return -EINVAL;
r = dm_get_device(ca->ti, dm_shift_arg(as), FMODE_READ | FMODE_WRITE,
&ca->cache_dev);
if (r) {
*error = "Error opening cache device";
return r;
}
ca->cache_sectors = get_dev_size(ca->cache_dev);
return 0;
}
static int parse_origin_dev(struct cache_args *ca, struct dm_arg_set *as,
char **error)
{
int r;
if (!at_least_one_arg(as, error))
return -EINVAL;
r = dm_get_device(ca->ti, dm_shift_arg(as), FMODE_READ | FMODE_WRITE,
&ca->origin_dev);
if (r) {
*error = "Error opening origin device";
return r;
}
ca->origin_sectors = get_dev_size(ca->origin_dev);
if (ca->ti->len > ca->origin_sectors) {
*error = "Device size larger than cached device";
return -EINVAL;
}
return 0;
}
static int parse_block_size(struct cache_args *ca, struct dm_arg_set *as,
char **error)
{
unsigned long tmp;
if (!at_least_one_arg(as, error))
return -EINVAL;
if (kstrtoul(dm_shift_arg(as), 10, &tmp) || !tmp ||
tmp < DATA_DEV_BLOCK_SIZE_MIN_SECTORS ||
tmp & (DATA_DEV_BLOCK_SIZE_MIN_SECTORS - 1)) {
*error = "Invalid data block size";
return -EINVAL;
}
if (tmp > ca->cache_sectors) {
*error = "Data block size is larger than the cache device";
return -EINVAL;
}
ca->block_size = tmp;
return 0;
}
static void init_features(struct cache_features *cf)
{
cf->mode = CM_WRITE;
cf->write_through = false;
}
static int parse_features(struct cache_args *ca, struct dm_arg_set *as,
char **error)
{
static struct dm_arg _args[] = {
{0, 1, "Invalid number of cache feature arguments"},
};
int r;
unsigned argc;
const char *arg;
struct cache_features *cf = &ca->features;
init_features(cf);
r = dm_read_arg_group(_args, as, &argc, error);
if (r)
return -EINVAL;
while (argc--) {
arg = dm_shift_arg(as);
if (!strcasecmp(arg, "writeback"))
cf->write_through = false;
else if (!strcasecmp(arg, "writethrough"))
cf->write_through = true;
else {
*error = "Unrecognised cache feature requested";
return -EINVAL;
}
}
return 0;
}
static int parse_policy(struct cache_args *ca, struct dm_arg_set *as,
char **error)
{
static struct dm_arg _args[] = {
{0, 1024, "Invalid number of policy arguments"},
};
int r;
if (!at_least_one_arg(as, error))
return -EINVAL;
ca->policy_name = dm_shift_arg(as);
r = dm_read_arg_group(_args, as, &ca->policy_argc, error);
if (r)
return -EINVAL;
ca->policy_argv = (const char **)as->argv;
dm_consume_args(as, ca->policy_argc);
return 0;
}
static int parse_cache_args(struct cache_args *ca, int argc, char **argv,
char **error)
{
int r;
struct dm_arg_set as;
as.argc = argc;
as.argv = argv;
r = parse_metadata_dev(ca, &as, error);
if (r)
return r;
r = parse_cache_dev(ca, &as, error);
if (r)
return r;
r = parse_origin_dev(ca, &as, error);
if (r)
return r;
r = parse_block_size(ca, &as, error);
if (r)
return r;
r = parse_features(ca, &as, error);
if (r)
return r;
r = parse_policy(ca, &as, error);
if (r)
return r;
return 0;
}
/*----------------------------------------------------------------*/
static struct kmem_cache *migration_cache;
#define NOT_CORE_OPTION 1
static int process_config_option(struct cache *cache, const char *key, const char *value)
{
unsigned long tmp;
if (!strcasecmp(key, "migration_threshold")) {
if (kstrtoul(value, 10, &tmp))
return -EINVAL;
cache->migration_threshold = tmp;
return 0;
}
return NOT_CORE_OPTION;
}
static int set_config_value(struct cache *cache, const char *key, const char *value)
{
int r = process_config_option(cache, key, value);
if (r == NOT_CORE_OPTION)
r = policy_set_config_value(cache->policy, key, value);
if (r)
DMWARN("bad config value for %s: %s", key, value);
return r;
}
static int set_config_values(struct cache *cache, int argc, const char **argv)
{
int r = 0;
if (argc & 1) {
DMWARN("Odd number of policy arguments given but they should be <key> <value> pairs.");
return -EINVAL;
}
while (argc) {
r = set_config_value(cache, argv[0], argv[1]);
if (r)
break;
argc -= 2;
argv += 2;
}
return r;
}
static int create_cache_policy(struct cache *cache, struct cache_args *ca,
char **error)
{
cache->policy = dm_cache_policy_create(ca->policy_name,
cache->cache_size,
cache->origin_sectors,
cache->sectors_per_block);
if (!cache->policy) {
*error = "Error creating cache's policy";
return -ENOMEM;
}
return 0;
}
/*
* We want the discard block size to be a power of two, at least the size
* of the cache block size, and have no more than 2^14 discard blocks
* across the origin.
*/
#define MAX_DISCARD_BLOCKS (1 << 14)
static bool too_many_discard_blocks(sector_t discard_block_size,
sector_t origin_size)
{
(void) sector_div(origin_size, discard_block_size);
return origin_size > MAX_DISCARD_BLOCKS;
}
static sector_t calculate_discard_block_size(sector_t cache_block_size,
sector_t origin_size)
{
sector_t discard_block_size;
discard_block_size = roundup_pow_of_two(cache_block_size);
if (origin_size)
while (too_many_discard_blocks(discard_block_size, origin_size))
discard_block_size *= 2;
return discard_block_size;
}
#define DEFAULT_MIGRATION_THRESHOLD 2048
static int cache_create(struct cache_args *ca, struct cache **result)
{
int r = 0;
char **error = &ca->ti->error;
struct cache *cache;
struct dm_target *ti = ca->ti;
dm_block_t origin_blocks;
struct dm_cache_metadata *cmd;
bool may_format = ca->features.mode == CM_WRITE;
cache = kzalloc(sizeof(*cache), GFP_KERNEL);
if (!cache)
return -ENOMEM;
cache->ti = ca->ti;
ti->private = cache;
ti->num_flush_bios = 2;
ti->flush_supported = true;
ti->num_discard_bios = 1;
ti->discards_supported = true;
ti->discard_zeroes_data_unsupported = true;
cache->features = ca->features;
ti->per_bio_data_size = get_per_bio_data_size(cache);
cache->callbacks.congested_fn = cache_is_congested;
dm_table_add_target_callbacks(ti->table, &cache->callbacks);
cache->metadata_dev = ca->metadata_dev;
cache->origin_dev = ca->origin_dev;
cache->cache_dev = ca->cache_dev;
ca->metadata_dev = ca->origin_dev = ca->cache_dev = NULL;
/* FIXME: factor out this whole section */
origin_blocks = cache->origin_sectors = ca->origin_sectors;
origin_blocks = block_div(origin_blocks, ca->block_size);
cache->origin_blocks = to_oblock(origin_blocks);
cache->sectors_per_block = ca->block_size;
if (dm_set_target_max_io_len(ti, cache->sectors_per_block)) {
r = -EINVAL;
goto bad;
}
if (ca->block_size & (ca->block_size - 1)) {
dm_block_t cache_size = ca->cache_sectors;
cache->sectors_per_block_shift = -1;
cache_size = block_div(cache_size, ca->block_size);
cache->cache_size = to_cblock(cache_size);
} else {
cache->sectors_per_block_shift = __ffs(ca->block_size);
cache->cache_size = to_cblock(ca->cache_sectors >> cache->sectors_per_block_shift);
}
r = create_cache_policy(cache, ca, error);
if (r)
goto bad;
cache->policy_nr_args = ca->policy_argc;
cache->migration_threshold = DEFAULT_MIGRATION_THRESHOLD;
r = set_config_values(cache, ca->policy_argc, ca->policy_argv);
if (r) {
*error = "Error setting cache policy's config values";
goto bad;
}
cmd = dm_cache_metadata_open(cache->metadata_dev->bdev,
ca->block_size, may_format,
dm_cache_policy_get_hint_size(cache->policy));
if (IS_ERR(cmd)) {
*error = "Error creating metadata object";
r = PTR_ERR(cmd);
goto bad;
}
cache->cmd = cmd;
spin_lock_init(&cache->lock);
bio_list_init(&cache->deferred_bios);
bio_list_init(&cache->deferred_flush_bios);
bio_list_init(&cache->deferred_writethrough_bios);
INIT_LIST_HEAD(&cache->quiesced_migrations);
INIT_LIST_HEAD(&cache->completed_migrations);
INIT_LIST_HEAD(&cache->need_commit_migrations);
atomic_set(&cache->nr_migrations, 0);
init_waitqueue_head(&cache->migration_wait);
r = -ENOMEM;
cache->nr_dirty = 0;
cache->dirty_bitset = alloc_bitset(from_cblock(cache->cache_size));
if (!cache->dirty_bitset) {
*error = "could not allocate dirty bitset";
goto bad;
}
clear_bitset(cache->dirty_bitset, from_cblock(cache->cache_size));
cache->discard_block_size =
calculate_discard_block_size(cache->sectors_per_block,
cache->origin_sectors);
cache->discard_nr_blocks = oblock_to_dblock(cache, cache->origin_blocks);
cache->discard_bitset = alloc_bitset(from_dblock(cache->discard_nr_blocks));
if (!cache->discard_bitset) {
*error = "could not allocate discard bitset";
goto bad;
}
clear_bitset(cache->discard_bitset, from_dblock(cache->discard_nr_blocks));
cache->copier = dm_kcopyd_client_create(&dm_kcopyd_throttle);
if (IS_ERR(cache->copier)) {
*error = "could not create kcopyd client";
r = PTR_ERR(cache->copier);
goto bad;
}
cache->wq = alloc_ordered_workqueue("dm-" DM_MSG_PREFIX, WQ_MEM_RECLAIM);
if (!cache->wq) {
*error = "could not create workqueue for metadata object";
goto bad;
}
INIT_WORK(&cache->worker, do_worker);
INIT_DELAYED_WORK(&cache->waker, do_waker);
cache->last_commit_jiffies = jiffies;
cache->prison = dm_bio_prison_create(PRISON_CELLS);
if (!cache->prison) {
*error = "could not create bio prison";
goto bad;
}
cache->all_io_ds = dm_deferred_set_create();
if (!cache->all_io_ds) {
*error = "could not create all_io deferred set";
goto bad;
}
cache->migration_pool = mempool_create_slab_pool(MIGRATION_POOL_SIZE,
migration_cache);
if (!cache->migration_pool) {
*error = "Error creating cache's migration mempool";
goto bad;
}
cache->next_migration = NULL;
cache->need_tick_bio = true;
cache->sized = false;
cache->quiescing = false;
cache->commit_requested = false;
cache->loaded_mappings = false;
cache->loaded_discards = false;
load_stats(cache);
atomic_set(&cache->stats.demotion, 0);
atomic_set(&cache->stats.promotion, 0);
atomic_set(&cache->stats.copies_avoided, 0);
atomic_set(&cache->stats.cache_cell_clash, 0);
atomic_set(&cache->stats.commit_count, 0);
atomic_set(&cache->stats.discard_count, 0);
*result = cache;
return 0;
bad:
destroy(cache);
return r;
}
static int copy_ctr_args(struct cache *cache, int argc, const char **argv)
{
unsigned i;
const char **copy;
copy = kcalloc(argc, sizeof(*copy), GFP_KERNEL);
if (!copy)
return -ENOMEM;
for (i = 0; i < argc; i++) {
copy[i] = kstrdup(argv[i], GFP_KERNEL);
if (!copy[i]) {
while (i--)
kfree(copy[i]);
kfree(copy);
return -ENOMEM;
}
}
cache->nr_ctr_args = argc;
cache->ctr_args = copy;
return 0;
}
static int cache_ctr(struct dm_target *ti, unsigned argc, char **argv)
{
int r = -EINVAL;
struct cache_args *ca;
struct cache *cache = NULL;
ca = kzalloc(sizeof(*ca), GFP_KERNEL);
if (!ca) {
ti->error = "Error allocating memory for cache";
return -ENOMEM;
}
ca->ti = ti;
r = parse_cache_args(ca, argc, argv, &ti->error);
if (r)
goto out;
r = cache_create(ca, &cache);
if (r)
goto out;
r = copy_ctr_args(cache, argc - 3, (const char **)argv + 3);
if (r) {
destroy(cache);
goto out;
}
ti->private = cache;
out:
destroy_cache_args(ca);
return r;
}
static int cache_map(struct dm_target *ti, struct bio *bio)
{
struct cache *cache = ti->private;
int r;
dm_oblock_t block = get_bio_block(cache, bio);
size_t pb_data_size = get_per_bio_data_size(cache);
bool can_migrate = false;
bool discarded_block;
struct dm_bio_prison_cell *cell;
struct policy_result lookup_result;
struct per_bio_data *pb;
if (from_oblock(block) > from_oblock(cache->origin_blocks)) {
/*
* This can only occur if the io goes to a partial block at
* the end of the origin device. We don't cache these.
* Just remap to the origin and carry on.
*/
remap_to_origin_clear_discard(cache, bio, block);
return DM_MAPIO_REMAPPED;
}
pb = init_per_bio_data(bio, pb_data_size);
if (bio->bi_rw & (REQ_FLUSH | REQ_FUA | REQ_DISCARD)) {
defer_bio(cache, bio);
return DM_MAPIO_SUBMITTED;
}
/*
* Check to see if that block is currently migrating.
*/
cell = alloc_prison_cell(cache);
if (!cell) {
defer_bio(cache, bio);
return DM_MAPIO_SUBMITTED;
}
r = bio_detain(cache, block, bio, cell,
(cell_free_fn) free_prison_cell,
cache, &cell);
if (r) {
if (r < 0)
defer_bio(cache, bio);
return DM_MAPIO_SUBMITTED;
}
discarded_block = is_discarded_oblock(cache, block);
r = policy_map(cache->policy, block, false, can_migrate, discarded_block,
bio, &lookup_result);
if (r == -EWOULDBLOCK) {
cell_defer(cache, cell, true);
return DM_MAPIO_SUBMITTED;
} else if (r) {
DMERR_LIMIT("Unexpected return from cache replacement policy: %d", r);
bio_io_error(bio);
return DM_MAPIO_SUBMITTED;
}
switch (lookup_result.op) {
case POLICY_HIT:
inc_hit_counter(cache, bio);
pb->all_io_entry = dm_deferred_entry_inc(cache->all_io_ds);
if (is_writethrough_io(cache, bio, lookup_result.cblock))
remap_to_origin_then_cache(cache, bio, block, lookup_result.cblock);
else
remap_to_cache_dirty(cache, bio, block, lookup_result.cblock);
cell_defer(cache, cell, false);
break;
case POLICY_MISS:
inc_miss_counter(cache, bio);
pb->all_io_entry = dm_deferred_entry_inc(cache->all_io_ds);
if (pb->req_nr != 0) {
/*
* This is a duplicate writethrough io that is no
* longer needed because the block has been demoted.
*/
bio_endio(bio, 0);
cell_defer(cache, cell, false);
return DM_MAPIO_SUBMITTED;
} else {
remap_to_origin_clear_discard(cache, bio, block);
cell_defer(cache, cell, false);
}
break;
default:
DMERR_LIMIT("%s: erroring bio: unknown policy op: %u", __func__,
(unsigned) lookup_result.op);
bio_io_error(bio);
return DM_MAPIO_SUBMITTED;
}
return DM_MAPIO_REMAPPED;
}
static int cache_end_io(struct dm_target *ti, struct bio *bio, int error)
{
struct cache *cache = ti->private;
unsigned long flags;
size_t pb_data_size = get_per_bio_data_size(cache);
struct per_bio_data *pb = get_per_bio_data(bio, pb_data_size);
if (pb->tick) {
policy_tick(cache->policy);
spin_lock_irqsave(&cache->lock, flags);
cache->need_tick_bio = true;
spin_unlock_irqrestore(&cache->lock, flags);
}
check_for_quiesced_migrations(cache, pb);
return 0;
}
static int write_dirty_bitset(struct cache *cache)
{
unsigned i, r;
for (i = 0; i < from_cblock(cache->cache_size); i++) {
r = dm_cache_set_dirty(cache->cmd, to_cblock(i),
is_dirty(cache, to_cblock(i)));
if (r)
return r;
}
return 0;
}
static int write_discard_bitset(struct cache *cache)
{
unsigned i, r;
r = dm_cache_discard_bitset_resize(cache->cmd, cache->discard_block_size,
cache->discard_nr_blocks);
if (r) {
DMERR("could not resize on-disk discard bitset");
return r;
}
for (i = 0; i < from_dblock(cache->discard_nr_blocks); i++) {
r = dm_cache_set_discard(cache->cmd, to_dblock(i),
is_discarded(cache, to_dblock(i)));
if (r)
return r;
}
return 0;
}
static int save_hint(void *context, dm_cblock_t cblock, dm_oblock_t oblock,
uint32_t hint)
{
struct cache *cache = context;
return dm_cache_save_hint(cache->cmd, cblock, hint);
}
static int write_hints(struct cache *cache)
{
int r;
r = dm_cache_begin_hints(cache->cmd, cache->policy);
if (r) {
DMERR("dm_cache_begin_hints failed");
return r;
}
r = policy_walk_mappings(cache->policy, save_hint, cache);
if (r)
DMERR("policy_walk_mappings failed");
return r;
}
/*
* returns true on success
*/
static bool sync_metadata(struct cache *cache)
{
int r1, r2, r3, r4;
r1 = write_dirty_bitset(cache);
if (r1)
DMERR("could not write dirty bitset");
r2 = write_discard_bitset(cache);
if (r2)
DMERR("could not write discard bitset");
save_stats(cache);
r3 = write_hints(cache);
if (r3)
DMERR("could not write hints");
/*
* If writing the above metadata failed, we still commit, but don't
* set the clean shutdown flag. This will effectively force every
* dirty bit to be set on reload.
*/
r4 = dm_cache_commit(cache->cmd, !r1 && !r2 && !r3);
if (r4)
DMERR("could not write cache metadata. Data loss may occur.");
return !r1 && !r2 && !r3 && !r4;
}
static void cache_postsuspend(struct dm_target *ti)
{
struct cache *cache = ti->private;
start_quiescing(cache);
wait_for_migrations(cache);
stop_worker(cache);
requeue_deferred_io(cache);
stop_quiescing(cache);
(void) sync_metadata(cache);
}
static int load_mapping(void *context, dm_oblock_t oblock, dm_cblock_t cblock,
bool dirty, uint32_t hint, bool hint_valid)
{
int r;
struct cache *cache = context;
r = policy_load_mapping(cache->policy, oblock, cblock, hint, hint_valid);
if (r)
return r;
if (dirty)
set_dirty(cache, oblock, cblock);
else
clear_dirty(cache, oblock, cblock);
return 0;
}
static int load_discard(void *context, sector_t discard_block_size,
dm_dblock_t dblock, bool discard)
{
struct cache *cache = context;
/* FIXME: handle mis-matched block size */
if (discard)
set_discard(cache, dblock);
else
clear_discard(cache, dblock);
return 0;
}
static int cache_preresume(struct dm_target *ti)
{
int r = 0;
struct cache *cache = ti->private;
sector_t actual_cache_size = get_dev_size(cache->cache_dev);
(void) sector_div(actual_cache_size, cache->sectors_per_block);
/*
* Check to see if the cache has resized.
*/
if (from_cblock(cache->cache_size) != actual_cache_size || !cache->sized) {
cache->cache_size = to_cblock(actual_cache_size);
r = dm_cache_resize(cache->cmd, cache->cache_size);
if (r) {
DMERR("could not resize cache metadata");
return r;
}
cache->sized = true;
}
if (!cache->loaded_mappings) {
r = dm_cache_load_mappings(cache->cmd, cache->policy,
load_mapping, cache);
if (r) {
DMERR("could not load cache mappings");
return r;
}
cache->loaded_mappings = true;
}
if (!cache->loaded_discards) {
r = dm_cache_load_discards(cache->cmd, load_discard, cache);
if (r) {
DMERR("could not load origin discards");
return r;
}
cache->loaded_discards = true;
}
return r;
}
static void cache_resume(struct dm_target *ti)
{
struct cache *cache = ti->private;
cache->need_tick_bio = true;
do_waker(&cache->waker.work);
}
/*
* Status format:
*
* <#used metadata blocks>/<#total metadata blocks>
* <#read hits> <#read misses> <#write hits> <#write misses>
* <#demotions> <#promotions> <#blocks in cache> <#dirty>
* <#features> <features>*
* <#core args> <core args>
* <#policy args> <policy args>*
*/
static void cache_status(struct dm_target *ti, status_type_t type,
unsigned status_flags, char *result, unsigned maxlen)
{
int r = 0;
unsigned i;
ssize_t sz = 0;
dm_block_t nr_free_blocks_metadata = 0;
dm_block_t nr_blocks_metadata = 0;
char buf[BDEVNAME_SIZE];
struct cache *cache = ti->private;
dm_cblock_t residency;
switch (type) {
case STATUSTYPE_INFO:
/* Commit to ensure statistics aren't out-of-date */
if (!(status_flags & DM_STATUS_NOFLUSH_FLAG) && !dm_suspended(ti)) {
r = dm_cache_commit(cache->cmd, false);
if (r)
DMERR("could not commit metadata for accurate status");
}
r = dm_cache_get_free_metadata_block_count(cache->cmd,
&nr_free_blocks_metadata);
if (r) {
DMERR("could not get metadata free block count");
goto err;
}
r = dm_cache_get_metadata_dev_size(cache->cmd, &nr_blocks_metadata);
if (r) {
DMERR("could not get metadata device size");
goto err;
}
residency = policy_residency(cache->policy);
DMEMIT("%llu/%llu %u %u %u %u %u %u %llu %u ",
(unsigned long long)(nr_blocks_metadata - nr_free_blocks_metadata),
(unsigned long long)nr_blocks_metadata,
(unsigned) atomic_read(&cache->stats.read_hit),
(unsigned) atomic_read(&cache->stats.read_miss),
(unsigned) atomic_read(&cache->stats.write_hit),
(unsigned) atomic_read(&cache->stats.write_miss),
(unsigned) atomic_read(&cache->stats.demotion),
(unsigned) atomic_read(&cache->stats.promotion),
(unsigned long long) from_cblock(residency),
cache->nr_dirty);
if (cache->features.write_through)
DMEMIT("1 writethrough ");
else
DMEMIT("0 ");
DMEMIT("2 migration_threshold %llu ", (unsigned long long) cache->migration_threshold);
if (sz < maxlen) {
r = policy_emit_config_values(cache->policy, result + sz, maxlen - sz);
if (r)
DMERR("policy_emit_config_values returned %d", r);
}
break;
case STATUSTYPE_TABLE:
format_dev_t(buf, cache->metadata_dev->bdev->bd_dev);
DMEMIT("%s ", buf);
format_dev_t(buf, cache->cache_dev->bdev->bd_dev);
DMEMIT("%s ", buf);
format_dev_t(buf, cache->origin_dev->bdev->bd_dev);
DMEMIT("%s", buf);
for (i = 0; i < cache->nr_ctr_args - 1; i++)
DMEMIT(" %s", cache->ctr_args[i]);
if (cache->nr_ctr_args)
DMEMIT(" %s", cache->ctr_args[cache->nr_ctr_args - 1]);
}
return;
err:
DMEMIT("Error");
}
/*
* Supports <key> <value>.
*
* The key migration_threshold is supported by the cache target core.
*/
static int cache_message(struct dm_target *ti, unsigned argc, char **argv)
{
struct cache *cache = ti->private;
if (argc != 2)
return -EINVAL;
return set_config_value(cache, argv[0], argv[1]);
}
static int cache_iterate_devices(struct dm_target *ti,
iterate_devices_callout_fn fn, void *data)
{
int r = 0;
struct cache *cache = ti->private;
r = fn(ti, cache->cache_dev, 0, get_dev_size(cache->cache_dev), data);
if (!r)
r = fn(ti, cache->origin_dev, 0, ti->len, data);
return r;
}
/*
* We assume I/O is going to the origin (which is the volume
* more likely to have restrictions e.g. by being striped).
* (Looking up the exact location of the data would be expensive
* and could always be out of date by the time the bio is submitted.)
*/
static int cache_bvec_merge(struct dm_target *ti,
struct bvec_merge_data *bvm,
struct bio_vec *biovec, int max_size)
{
struct cache *cache = ti->private;
struct request_queue *q = bdev_get_queue(cache->origin_dev->bdev);
if (!q->merge_bvec_fn)
return max_size;
bvm->bi_bdev = cache->origin_dev->bdev;
return min(max_size, q->merge_bvec_fn(q, bvm, biovec));
}
static void set_discard_limits(struct cache *cache, struct queue_limits *limits)
{
/*
* FIXME: these limits may be incompatible with the cache device
*/
limits->max_discard_sectors = cache->discard_block_size * 1024;
limits->discard_granularity = cache->discard_block_size << SECTOR_SHIFT;
}
static void cache_io_hints(struct dm_target *ti, struct queue_limits *limits)
{
struct cache *cache = ti->private;
blk_limits_io_min(limits, 0);
blk_limits_io_opt(limits, cache->sectors_per_block << SECTOR_SHIFT);
set_discard_limits(cache, limits);
}
/*----------------------------------------------------------------*/
static struct target_type cache_target = {
.name = "cache",
.version = {1, 1, 1},
.module = THIS_MODULE,
.ctr = cache_ctr,
.dtr = cache_dtr,
.map = cache_map,
.end_io = cache_end_io,
.postsuspend = cache_postsuspend,
.preresume = cache_preresume,
.resume = cache_resume,
.status = cache_status,
.message = cache_message,
.iterate_devices = cache_iterate_devices,
.merge = cache_bvec_merge,
.io_hints = cache_io_hints,
};
static int __init dm_cache_init(void)
{
int r;
r = dm_register_target(&cache_target);
if (r) {
DMERR("cache target registration failed: %d", r);
return r;
}
migration_cache = KMEM_CACHE(dm_cache_migration, 0);
if (!migration_cache) {
dm_unregister_target(&cache_target);
return -ENOMEM;
}
return 0;
}
static void __exit dm_cache_exit(void)
{
dm_unregister_target(&cache_target);
kmem_cache_destroy(migration_cache);
}
module_init(dm_cache_init);
module_exit(dm_cache_exit);
MODULE_DESCRIPTION(DM_NAME " cache target");
MODULE_AUTHOR("Joe Thornber <ejt@redhat.com>");
MODULE_LICENSE("GPL");