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OpenCloudOS-Kernel/drivers/md/dm-cache-target.c

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/*
* Copyright (C) 2012 Red Hat. All rights reserved.
*
* This file is released under the GPL.
*/
#include "dm.h"
#include "dm-bio-prison-v2.h"
#include "dm-bio-record.h"
#include "dm-cache-metadata.h"
#include <linux/dm-io.h>
#include <linux/dm-kcopyd.h>
#include <linux/jiffies.h>
#include <linux/init.h>
#include <linux/mempool.h>
#include <linux/module.h>
#include <linux/rwsem.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
*/
/*----------------------------------------------------------------*/
struct io_tracker {
spinlock_t lock;
/*
* Sectors of in-flight IO.
*/
sector_t in_flight;
/*
* The time, in jiffies, when this device became idle (if it is
* indeed idle).
*/
unsigned long idle_time;
unsigned long last_update_time;
};
static void iot_init(struct io_tracker *iot)
{
spin_lock_init(&iot->lock);
iot->in_flight = 0ul;
iot->idle_time = 0ul;
iot->last_update_time = jiffies;
}
static bool __iot_idle_for(struct io_tracker *iot, unsigned long jifs)
{
if (iot->in_flight)
return false;
return time_after(jiffies, iot->idle_time + jifs);
}
static bool iot_idle_for(struct io_tracker *iot, unsigned long jifs)
{
bool r;
unsigned long flags;
spin_lock_irqsave(&iot->lock, flags);
r = __iot_idle_for(iot, jifs);
spin_unlock_irqrestore(&iot->lock, flags);
return r;
}
static void iot_io_begin(struct io_tracker *iot, sector_t len)
{
unsigned long flags;
spin_lock_irqsave(&iot->lock, flags);
iot->in_flight += len;
spin_unlock_irqrestore(&iot->lock, flags);
}
static void __iot_io_end(struct io_tracker *iot, sector_t len)
{
if (!len)
return;
iot->in_flight -= len;
if (!iot->in_flight)
iot->idle_time = jiffies;
}
static void iot_io_end(struct io_tracker *iot, sector_t len)
{
unsigned long flags;
spin_lock_irqsave(&iot->lock, flags);
__iot_io_end(iot, len);
spin_unlock_irqrestore(&iot->lock, flags);
}
/*----------------------------------------------------------------*/
/*
* Represents a chunk of future work. 'input' allows continuations to pass
* values between themselves, typically error values.
*/
struct continuation {
struct work_struct ws;
blk_status_t input;
};
static inline void init_continuation(struct continuation *k,
void (*fn)(struct work_struct *))
{
INIT_WORK(&k->ws, fn);
k->input = 0;
}
static inline void queue_continuation(struct workqueue_struct *wq,
struct continuation *k)
{
queue_work(wq, &k->ws);
}
/*----------------------------------------------------------------*/
/*
* The batcher collects together pieces of work that need a particular
* operation to occur before they can proceed (typically a commit).
*/
struct batcher {
/*
* The operation that everyone is waiting for.
*/
blk_status_t (*commit_op)(void *context);
void *commit_context;
/*
* This is how bios should be issued once the commit op is complete
* (accounted_request).
*/
void (*issue_op)(struct bio *bio, void *context);
void *issue_context;
/*
* Queued work gets put on here after commit.
*/
struct workqueue_struct *wq;
spinlock_t lock;
struct list_head work_items;
struct bio_list bios;
struct work_struct commit_work;
bool commit_scheduled;
};
static void __commit(struct work_struct *_ws)
{
struct batcher *b = container_of(_ws, struct batcher, commit_work);
blk_status_t r;
unsigned long flags;
struct list_head work_items;
struct work_struct *ws, *tmp;
struct continuation *k;
struct bio *bio;
struct bio_list bios;
INIT_LIST_HEAD(&work_items);
bio_list_init(&bios);
/*
* We have to grab these before the commit_op to avoid a race
* condition.
*/
spin_lock_irqsave(&b->lock, flags);
list_splice_init(&b->work_items, &work_items);
bio_list_merge(&bios, &b->bios);
bio_list_init(&b->bios);
b->commit_scheduled = false;
spin_unlock_irqrestore(&b->lock, flags);
r = b->commit_op(b->commit_context);
list_for_each_entry_safe(ws, tmp, &work_items, entry) {
k = container_of(ws, struct continuation, ws);
k->input = r;
INIT_LIST_HEAD(&ws->entry); /* to avoid a WARN_ON */
queue_work(b->wq, ws);
}
while ((bio = bio_list_pop(&bios))) {
if (r) {
bio->bi_status = r;
bio_endio(bio);
} else
b->issue_op(bio, b->issue_context);
}
}
static void batcher_init(struct batcher *b,
blk_status_t (*commit_op)(void *),
void *commit_context,
void (*issue_op)(struct bio *bio, void *),
void *issue_context,
struct workqueue_struct *wq)
{
b->commit_op = commit_op;
b->commit_context = commit_context;
b->issue_op = issue_op;
b->issue_context = issue_context;
b->wq = wq;
spin_lock_init(&b->lock);
INIT_LIST_HEAD(&b->work_items);
bio_list_init(&b->bios);
INIT_WORK(&b->commit_work, __commit);
b->commit_scheduled = false;
}
static void async_commit(struct batcher *b)
{
queue_work(b->wq, &b->commit_work);
}
static void continue_after_commit(struct batcher *b, struct continuation *k)
{
unsigned long flags;
bool commit_scheduled;
spin_lock_irqsave(&b->lock, flags);
commit_scheduled = b->commit_scheduled;
list_add_tail(&k->ws.entry, &b->work_items);
spin_unlock_irqrestore(&b->lock, flags);
if (commit_scheduled)
async_commit(b);
}
/*
* Bios are errored if commit failed.
*/
static void issue_after_commit(struct batcher *b, struct bio *bio)
{
unsigned long flags;
bool commit_scheduled;
spin_lock_irqsave(&b->lock, flags);
commit_scheduled = b->commit_scheduled;
bio_list_add(&b->bios, bio);
spin_unlock_irqrestore(&b->lock, flags);
if (commit_scheduled)
async_commit(b);
}
/*
* Call this if some urgent work is waiting for the commit to complete.
*/
static void schedule_commit(struct batcher *b)
{
bool immediate;
unsigned long flags;
spin_lock_irqsave(&b->lock, flags);
immediate = !list_empty(&b->work_items) || !bio_list_empty(&b->bios);
b->commit_scheduled = true;
spin_unlock_irqrestore(&b->lock, flags);
if (immediate)
async_commit(b);
}
/*
* There are a couple of places where we let a bio run, but want to do some
* work before calling its endio function. We do this by temporarily
* changing the endio fn.
*/
struct dm_hook_info {
bio_end_io_t *bi_end_io;
};
static void dm_hook_bio(struct dm_hook_info *h, struct bio *bio,
bio_end_io_t *bi_end_io, void *bi_private)
{
h->bi_end_io = bio->bi_end_io;
bio->bi_end_io = bi_end_io;
bio->bi_private = bi_private;
}
static void dm_unhook_bio(struct dm_hook_info *h, struct bio *bio)
{
bio->bi_end_io = h->bi_end_io;
}
/*----------------------------------------------------------------*/
#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
* between 32KB and 1GB.
*/
#define DATA_DEV_BLOCK_SIZE_MIN_SECTORS (32 * 1024 >> SECTOR_SHIFT)
#define DATA_DEV_BLOCK_SIZE_MAX_SECTORS (1024 * 1024 * 1024 >> SECTOR_SHIFT)
enum cache_metadata_mode {
CM_WRITE, /* metadata may be changed */
CM_READ_ONLY, /* metadata may not be changed */
CM_FAIL
};
enum cache_io_mode {
/*
* Data is written to cached blocks only. These blocks are marked
* dirty. If you lose the cache device you will lose data.
* Potential performance increase for both reads and writes.
*/
CM_IO_WRITEBACK,
/*
* Data is written to both cache and origin. Blocks are never
* dirty. Potential performance benfit for reads only.
*/
CM_IO_WRITETHROUGH,
/*
* A degraded mode useful for various cache coherency situations
* (eg, rolling back snapshots). Reads and writes always go to the
* origin. If a write goes to a cached oblock, then the cache
* block is invalidated.
*/
CM_IO_PASSTHROUGH
};
struct cache_features {
enum cache_metadata_mode mode;
enum cache_io_mode io_mode;
unsigned metadata_version;
bool discard_passdown: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 writeback;
atomic_t copies_avoided;
atomic_t cache_cell_clash;
atomic_t commit_count;
atomic_t discard_count;
};
struct cache {
struct dm_target *ti;
spinlock_t lock;
/*
* Fields for converting from sectors to blocks.
*/
int sectors_per_block_shift;
sector_t sectors_per_block;
struct dm_cache_metadata *cmd;
/*
* 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;
/*
* 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;
/*
* Invalidation fields.
*/
spinlock_t invalidation_lock;
struct list_head invalidation_requests;
sector_t migration_threshold;
wait_queue_head_t migration_wait;
atomic_t nr_allocated_migrations;
/*
* The number of in flight migrations that are performing
* background io. eg, promotion, writeback.
*/
atomic_t nr_io_migrations;
struct bio_list deferred_bios;
struct rw_semaphore quiesce_lock;
struct dm_target_callbacks callbacks;
/*
* origin_blocks entries, discarded if set.
*/
dm_dblock_t discard_nr_blocks;
unsigned long *discard_bitset;
uint32_t discard_block_size; /* a power of 2 times sectors per block */
/*
* Rather than reconstructing the table line for the status we just
* save it and regurgitate.
*/
unsigned nr_ctr_args;
const char **ctr_args;
struct dm_kcopyd_client *copier;
struct work_struct deferred_bio_worker;
struct work_struct migration_worker;
struct workqueue_struct *wq;
struct delayed_work waker;
struct dm_bio_prison_v2 *prison;
/*
* cache_size entries, dirty if set
*/
unsigned long *dirty_bitset;
atomic_t nr_dirty;
unsigned policy_nr_args;
struct dm_cache_policy *policy;
/*
* Cache features such as write-through.
*/
struct cache_features features;
struct cache_stats stats;
bool need_tick_bio:1;
bool sized:1;
bool invalidate:1;
bool commit_requested:1;
bool loaded_mappings:1;
bool loaded_discards:1;
struct rw_semaphore background_work_lock;
struct batcher committer;
struct work_struct commit_ws;
struct io_tracker tracker;
mempool_t migration_pool;
struct bio_set bs;
};
struct per_bio_data {
bool tick:1;
unsigned req_nr:2;
struct dm_bio_prison_cell_v2 *cell;
struct dm_hook_info hook_info;
sector_t len;
};
struct dm_cache_migration {
struct continuation k;
struct cache *cache;
struct policy_work *op;
struct bio *overwrite_bio;
struct dm_bio_prison_cell_v2 *cell;
dm_cblock_t invalidate_cblock;
dm_oblock_t invalidate_oblock;
};
/*----------------------------------------------------------------*/
static bool writethrough_mode(struct cache *cache)
{
return cache->features.io_mode == CM_IO_WRITETHROUGH;
}
static bool writeback_mode(struct cache *cache)
{
return cache->features.io_mode == CM_IO_WRITEBACK;
}
static inline bool passthrough_mode(struct cache *cache)
{
return unlikely(cache->features.io_mode == CM_IO_PASSTHROUGH);
}
/*----------------------------------------------------------------*/
static void wake_deferred_bio_worker(struct cache *cache)
{
queue_work(cache->wq, &cache->deferred_bio_worker);
}
static void wake_migration_worker(struct cache *cache)
{
if (passthrough_mode(cache))
return;
queue_work(cache->wq, &cache->migration_worker);
}
/*----------------------------------------------------------------*/
static struct dm_bio_prison_cell_v2 *alloc_prison_cell(struct cache *cache)
{
return dm_bio_prison_alloc_cell_v2(cache->prison, GFP_NOIO);
}
static void free_prison_cell(struct cache *cache, struct dm_bio_prison_cell_v2 *cell)
{
dm_bio_prison_free_cell_v2(cache->prison, cell);
}
static struct dm_cache_migration *alloc_migration(struct cache *cache)
{
struct dm_cache_migration *mg;
mg = mempool_alloc(&cache->migration_pool, GFP_NOIO);
memset(mg, 0, sizeof(*mg));
mg->cache = cache;
atomic_inc(&cache->nr_allocated_migrations);
return mg;
}
static void free_migration(struct dm_cache_migration *mg)
{
struct cache *cache = mg->cache;
if (atomic_dec_and_test(&cache->nr_allocated_migrations))
wake_up(&cache->migration_wait);
mempool_free(mg, &cache->migration_pool);
}
/*----------------------------------------------------------------*/
static inline dm_oblock_t oblock_succ(dm_oblock_t b)
{
return to_oblock(from_oblock(b) + 1ull);
}
static void build_key(dm_oblock_t begin, dm_oblock_t end, struct dm_cell_key_v2 *key)
{
key->virtual = 0;
key->dev = 0;
key->block_begin = from_oblock(begin);
key->block_end = from_oblock(end);
}
/*
* We have two lock levels. Level 0, which is used to prevent WRITEs, and
* level 1 which prevents *both* READs and WRITEs.
*/
#define WRITE_LOCK_LEVEL 0
#define READ_WRITE_LOCK_LEVEL 1
static unsigned lock_level(struct bio *bio)
{
return bio_data_dir(bio) == WRITE ?
WRITE_LOCK_LEVEL :
READ_WRITE_LOCK_LEVEL;
}
/*----------------------------------------------------------------
* Per bio data
*--------------------------------------------------------------*/
static struct per_bio_data *get_per_bio_data(struct bio *bio)
{
struct per_bio_data *pb = dm_per_bio_data(bio, sizeof(struct per_bio_data));
BUG_ON(!pb);
return pb;
}
static struct per_bio_data *init_per_bio_data(struct bio *bio)
{
struct per_bio_data *pb = get_per_bio_data(bio);
pb->tick = false;
pb->req_nr = dm_bio_get_target_bio_nr(bio);
pb->cell = NULL;
pb->len = 0;
return pb;
}
/*----------------------------------------------------------------*/
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_deferred_bio_worker(cache);
}
static void defer_bios(struct cache *cache, struct bio_list *bios)
{
unsigned long flags;
spin_lock_irqsave(&cache->lock, flags);
bio_list_merge(&cache->deferred_bios, bios);
bio_list_init(bios);
spin_unlock_irqrestore(&cache->lock, flags);
wake_deferred_bio_worker(cache);
}
/*----------------------------------------------------------------*/
static bool bio_detain_shared(struct cache *cache, dm_oblock_t oblock, struct bio *bio)
{
bool r;
struct per_bio_data *pb;
struct dm_cell_key_v2 key;
dm_oblock_t end = to_oblock(from_oblock(oblock) + 1ULL);
struct dm_bio_prison_cell_v2 *cell_prealloc, *cell;
cell_prealloc = alloc_prison_cell(cache); /* FIXME: allow wait if calling from worker */
build_key(oblock, end, &key);
r = dm_cell_get_v2(cache->prison, &key, lock_level(bio), bio, cell_prealloc, &cell);
if (!r) {
/*
* Failed to get the lock.
*/
free_prison_cell(cache, cell_prealloc);
return r;
}
if (cell != cell_prealloc)
free_prison_cell(cache, cell_prealloc);
pb = get_per_bio_data(bio);
pb->cell = cell;
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_cblock_t cblock)
{
if (!test_and_set_bit(from_cblock(cblock), cache->dirty_bitset)) {
atomic_inc(&cache->nr_dirty);
policy_set_dirty(cache->policy, cblock);
}
}
/*
* These two are called when setting after migrations to force the policy
* and dirty bitset to be in sync.
*/
static void force_set_dirty(struct cache *cache, dm_cblock_t cblock)
{
if (!test_and_set_bit(from_cblock(cblock), cache->dirty_bitset))
atomic_inc(&cache->nr_dirty);
policy_set_dirty(cache->policy, cblock);
}
static void force_clear_dirty(struct cache *cache, dm_cblock_t cblock)
{
if (test_and_clear_bit(from_cblock(cblock), cache->dirty_bitset)) {
if (atomic_dec_return(&cache->nr_dirty) == 0)
dm_table_event(cache->ti->table);
}
policy_clear_dirty(cache->policy, cblock);
}
/*----------------------------------------------------------------*/
static bool block_size_is_power_of_two(struct cache *cache)
{
return cache->sectors_per_block_shift >= 0;
}
/* gcc on ARM generates spurious references to __udivdi3 and __umoddi3 */
#if defined(CONFIG_ARM) && __GNUC__ == 4 && __GNUC_MINOR__ <= 6
__always_inline
#endif
static dm_block_t block_div(dm_block_t b, uint32_t n)
{
do_div(b, n);
return b;
}
static dm_block_t oblocks_per_dblock(struct cache *cache)
{
dm_block_t oblocks = cache->discard_block_size;
if (block_size_is_power_of_two(cache))
oblocks >>= cache->sectors_per_block_shift;
else
oblocks = block_div(oblocks, cache->sectors_per_block);
return oblocks;
}
static dm_dblock_t oblock_to_dblock(struct cache *cache, dm_oblock_t oblock)
{
return to_dblock(block_div(from_oblock(oblock),
oblocks_per_dblock(cache)));
}
static void set_discard(struct cache *cache, dm_dblock_t b)
{
unsigned long flags;
BUG_ON(from_dblock(b) >= from_dblock(cache->discard_nr_blocks));
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;
}
/*----------------------------------------------------------------
* Remapping
*--------------------------------------------------------------*/
static void remap_to_origin(struct cache *cache, struct bio *bio)
{
bio_set_dev(bio, 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_iter.bi_sector;
sector_t block = from_cblock(cblock);
bio_set_dev(bio, cache->cache_dev->bdev);
if (!block_size_is_power_of_two(cache))
bio->bi_iter.bi_sector =
(block * cache->sectors_per_block) +
sector_div(bi_sector, cache->sectors_per_block);
else
bio->bi_iter.bi_sector =
(block << 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;
struct per_bio_data *pb;
spin_lock_irqsave(&cache->lock, flags);
if (cache->need_tick_bio && !op_is_flush(bio->bi_opf) &&
bio_op(bio) != REQ_OP_DISCARD) {
pb = get_per_bio_data(bio);
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, bool bio_has_pbd)
{
if (bio_has_pbd)
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_origin_clear_discard(struct cache *cache, struct bio *bio,
dm_oblock_t oblock)
{
// FIXME: check_if_tick_bio_needed() is called way too much through this interface
__remap_to_origin_clear_discard(cache, bio, oblock, true);
}
static void remap_to_cache_dirty(struct cache *cache, struct bio *bio,
dm_oblock_t oblock, dm_cblock_t cblock)
{
check_if_tick_bio_needed(cache, bio);
remap_to_cache(cache, bio, cblock);
if (bio_data_dir(bio) == WRITE) {
set_dirty(cache, 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_iter.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 bool accountable_bio(struct cache *cache, struct bio *bio)
{
return bio_op(bio) != REQ_OP_DISCARD;
}
static void accounted_begin(struct cache *cache, struct bio *bio)
{
struct per_bio_data *pb;
if (accountable_bio(cache, bio)) {
pb = get_per_bio_data(bio);
pb->len = bio_sectors(bio);
iot_io_begin(&cache->tracker, pb->len);
}
}
static void accounted_complete(struct cache *cache, struct bio *bio)
{
struct per_bio_data *pb = get_per_bio_data(bio);
iot_io_end(&cache->tracker, pb->len);
}
static void accounted_request(struct cache *cache, struct bio *bio)
{
accounted_begin(cache, bio);
generic_make_request(bio);
}
static void issue_op(struct bio *bio, void *context)
{
struct cache *cache = context;
accounted_request(cache, bio);
}
/*
* When running in writethrough mode we need to send writes to clean blocks
* to both the cache and origin devices. Clone the bio and send them in parallel.
*/
static void remap_to_origin_and_cache(struct cache *cache, struct bio *bio,
dm_oblock_t oblock, dm_cblock_t cblock)
{
struct bio *origin_bio = bio_clone_fast(bio, GFP_NOIO, &cache->bs);
BUG_ON(!origin_bio);
bio_chain(origin_bio, bio);
/*
* Passing false to __remap_to_origin_clear_discard() skips
* all code that might use per_bio_data (since clone doesn't have it)
*/
__remap_to_origin_clear_discard(cache, origin_bio, oblock, false);
submit_bio(origin_bio);
remap_to_cache(cache, bio, cblock);
}
/*----------------------------------------------------------------
* Failure modes
*--------------------------------------------------------------*/
static enum cache_metadata_mode get_cache_mode(struct cache *cache)
{
return cache->features.mode;
}
static const char *cache_device_name(struct cache *cache)
{
return dm_device_name(dm_table_get_md(cache->ti->table));
}
static void notify_mode_switch(struct cache *cache, enum cache_metadata_mode mode)
{
const char *descs[] = {
"write",
"read-only",
"fail"
};
dm_table_event(cache->ti->table);
DMINFO("%s: switching cache to %s mode",
cache_device_name(cache), descs[(int)mode]);
}
static void set_cache_mode(struct cache *cache, enum cache_metadata_mode new_mode)
{
bool needs_check;
enum cache_metadata_mode old_mode = get_cache_mode(cache);
if (dm_cache_metadata_needs_check(cache->cmd, &needs_check)) {
DMERR("%s: unable to read needs_check flag, setting failure mode.",
cache_device_name(cache));
new_mode = CM_FAIL;
}
if (new_mode == CM_WRITE && needs_check) {
DMERR("%s: unable to switch cache to write mode until repaired.",
cache_device_name(cache));
if (old_mode != new_mode)
new_mode = old_mode;
else
new_mode = CM_READ_ONLY;
}
/* Never move out of fail mode */
if (old_mode == CM_FAIL)
new_mode = CM_FAIL;
switch (new_mode) {
case CM_FAIL:
case CM_READ_ONLY:
dm_cache_metadata_set_read_only(cache->cmd);
break;
case CM_WRITE:
dm_cache_metadata_set_read_write(cache->cmd);
break;
}
cache->features.mode = new_mode;
if (new_mode != old_mode)
notify_mode_switch(cache, new_mode);
}
static void abort_transaction(struct cache *cache)
{
const char *dev_name = cache_device_name(cache);
if (get_cache_mode(cache) >= CM_READ_ONLY)
return;
if (dm_cache_metadata_set_needs_check(cache->cmd)) {
DMERR("%s: failed to set 'needs_check' flag in metadata", dev_name);
set_cache_mode(cache, CM_FAIL);
}
DMERR_LIMIT("%s: aborting current metadata transaction", dev_name);
if (dm_cache_metadata_abort(cache->cmd)) {
DMERR("%s: failed to abort metadata transaction", dev_name);
set_cache_mode(cache, CM_FAIL);
}
}
static void metadata_operation_failed(struct cache *cache, const char *op, int r)
{
DMERR_LIMIT("%s: metadata operation '%s' failed: error = %d",
cache_device_name(cache), op, r);
abort_transaction(cache);
set_cache_mode(cache, CM_READ_ONLY);
}
/*----------------------------------------------------------------*/
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;
if (get_cache_mode(cache) >= CM_READ_ONLY)
return;
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);
}
static void update_stats(struct cache_stats *stats, enum policy_operation op)
{
switch (op) {
case POLICY_PROMOTE:
atomic_inc(&stats->promotion);
break;
case POLICY_DEMOTE:
atomic_inc(&stats->demotion);
break;
case POLICY_WRITEBACK:
atomic_inc(&stats->writeback);
break;
}
}
/*----------------------------------------------------------------
* Migration processing
*
* Migration covers moving data from the origin device to the cache, or
* vice versa.
*--------------------------------------------------------------*/
static void inc_io_migrations(struct cache *cache)
{
atomic_inc(&cache->nr_io_migrations);
}
static void dec_io_migrations(struct cache *cache)
{
atomic_dec(&cache->nr_io_migrations);
}
static bool discard_or_flush(struct bio *bio)
{
return bio_op(bio) == REQ_OP_DISCARD || op_is_flush(bio->bi_opf);
}
static void calc_discard_block_range(struct cache *cache, struct bio *bio,
dm_dblock_t *b, dm_dblock_t *e)
{
sector_t sb = bio->bi_iter.bi_sector;
sector_t se = bio_end_sector(bio);
*b = to_dblock(dm_sector_div_up(sb, cache->discard_block_size));
if (se - sb < cache->discard_block_size)
*e = *b;
else
*e = to_dblock(block_div(se, cache->discard_block_size));
}
/*----------------------------------------------------------------*/
static void prevent_background_work(struct cache *cache)
{
lockdep_off();
down_write(&cache->background_work_lock);
lockdep_on();
}
static void allow_background_work(struct cache *cache)
{
lockdep_off();
up_write(&cache->background_work_lock);
lockdep_on();
}
static bool background_work_begin(struct cache *cache)
{
bool r;
lockdep_off();
r = down_read_trylock(&cache->background_work_lock);
lockdep_on();
return r;
}
static void background_work_end(struct cache *cache)
{
lockdep_off();
up_read(&cache->background_work_lock);
lockdep_on();
}
/*----------------------------------------------------------------*/
static bool bio_writes_complete_block(struct cache *cache, struct bio *bio)
{
return (bio_data_dir(bio) == WRITE) &&
(bio->bi_iter.bi_size == (cache->sectors_per_block << SECTOR_SHIFT));
}
static bool optimisable_bio(struct cache *cache, struct bio *bio, dm_oblock_t block)
{
return writeback_mode(cache) &&
(is_discarded_oblock(cache, block) || bio_writes_complete_block(cache, bio));
}
static void quiesce(struct dm_cache_migration *mg,
void (*continuation)(struct work_struct *))
{
init_continuation(&mg->k, continuation);
dm_cell_quiesce_v2(mg->cache->prison, mg->cell, &mg->k.ws);
}
static struct dm_cache_migration *ws_to_mg(struct work_struct *ws)
{
struct continuation *k = container_of(ws, struct continuation, ws);
return container_of(k, struct dm_cache_migration, k);
}
static void copy_complete(int read_err, unsigned long write_err, void *context)
{
struct dm_cache_migration *mg = container_of(context, struct dm_cache_migration, k);
if (read_err || write_err)
mg->k.input = BLK_STS_IOERR;
queue_continuation(mg->cache->wq, &mg->k);
}
static void copy(struct dm_cache_migration *mg, bool promote)
{
struct dm_io_region o_region, c_region;
struct cache *cache = mg->cache;
o_region.bdev = cache->origin_dev->bdev;
o_region.sector = from_oblock(mg->op->oblock) * cache->sectors_per_block;
o_region.count = cache->sectors_per_block;
c_region.bdev = cache->cache_dev->bdev;
c_region.sector = from_cblock(mg->op->cblock) * cache->sectors_per_block;
c_region.count = cache->sectors_per_block;
if (promote)
dm_kcopyd_copy(cache->copier, &o_region, 1, &c_region, 0, copy_complete, &mg->k);
else
dm_kcopyd_copy(cache->copier, &c_region, 1, &o_region, 0, copy_complete, &mg->k);
}
static void bio_drop_shared_lock(struct cache *cache, struct bio *bio)
{
struct per_bio_data *pb = get_per_bio_data(bio);
if (pb->cell && dm_cell_put_v2(cache->prison, pb->cell))
free_prison_cell(cache, pb->cell);
pb->cell = NULL;
}
static void overwrite_endio(struct bio *bio)
{
struct dm_cache_migration *mg = bio->bi_private;
struct cache *cache = mg->cache;
struct per_bio_data *pb = get_per_bio_data(bio);
dm_unhook_bio(&pb->hook_info, bio);
if (bio->bi_status)
mg->k.input = bio->bi_status;
queue_continuation(cache->wq, &mg->k);
}
static void overwrite(struct dm_cache_migration *mg,
void (*continuation)(struct work_struct *))
{
struct bio *bio = mg->overwrite_bio;
struct per_bio_data *pb = get_per_bio_data(bio);
dm_hook_bio(&pb->hook_info, bio, overwrite_endio, mg);
/*
* The overwrite bio is part of the copy operation, as such it does
* not set/clear discard or dirty flags.
*/
if (mg->op->op == POLICY_PROMOTE)
remap_to_cache(mg->cache, bio, mg->op->cblock);
else
remap_to_origin(mg->cache, bio);
init_continuation(&mg->k, continuation);
accounted_request(mg->cache, bio);
}
/*
* Migration steps:
*
* 1) exclusive lock preventing WRITEs
* 2) quiesce
* 3) copy or issue overwrite bio
* 4) upgrade to exclusive lock preventing READs and WRITEs
* 5) quiesce
* 6) update metadata and commit
* 7) unlock
*/
static void mg_complete(struct dm_cache_migration *mg, bool success)
{
struct bio_list bios;
struct cache *cache = mg->cache;
struct policy_work *op = mg->op;
dm_cblock_t cblock = op->cblock;
if (success)
update_stats(&cache->stats, op->op);
switch (op->op) {
case POLICY_PROMOTE:
clear_discard(cache, oblock_to_dblock(cache, op->oblock));
policy_complete_background_work(cache->policy, op, success);
if (mg->overwrite_bio) {
if (success)
force_set_dirty(cache, cblock);
else if (mg->k.input)
mg->overwrite_bio->bi_status = mg->k.input;
else
mg->overwrite_bio->bi_status = BLK_STS_IOERR;
bio_endio(mg->overwrite_bio);
} else {
if (success)
force_clear_dirty(cache, cblock);
dec_io_migrations(cache);
}
break;
case POLICY_DEMOTE:
/*
* We clear dirty here to update the nr_dirty counter.
*/
if (success)
force_clear_dirty(cache, cblock);
policy_complete_background_work(cache->policy, op, success);
dec_io_migrations(cache);
break;
case POLICY_WRITEBACK:
if (success)
force_clear_dirty(cache, cblock);
policy_complete_background_work(cache->policy, op, success);
dec_io_migrations(cache);
break;
}
bio_list_init(&bios);
if (mg->cell) {
if (dm_cell_unlock_v2(cache->prison, mg->cell, &bios))
free_prison_cell(cache, mg->cell);
}
free_migration(mg);
defer_bios(cache, &bios);
wake_migration_worker(cache);
background_work_end(cache);
}
static void mg_success(struct work_struct *ws)
{
struct dm_cache_migration *mg = ws_to_mg(ws);
mg_complete(mg, mg->k.input == 0);
}
static void mg_update_metadata(struct work_struct *ws)
{
int r;
struct dm_cache_migration *mg = ws_to_mg(ws);
struct cache *cache = mg->cache;
struct policy_work *op = mg->op;
switch (op->op) {
case POLICY_PROMOTE:
r = dm_cache_insert_mapping(cache->cmd, op->cblock, op->oblock);
if (r) {
DMERR_LIMIT("%s: migration failed; couldn't insert mapping",
cache_device_name(cache));
metadata_operation_failed(cache, "dm_cache_insert_mapping", r);
mg_complete(mg, false);
return;
}
mg_complete(mg, true);
break;
case POLICY_DEMOTE:
r = dm_cache_remove_mapping(cache->cmd, op->cblock);
if (r) {
DMERR_LIMIT("%s: migration failed; couldn't update on disk metadata",
cache_device_name(cache));
metadata_operation_failed(cache, "dm_cache_remove_mapping", r);
mg_complete(mg, false);
return;
}
/*
* It would be nice if we only had to commit when a REQ_FLUSH
* comes through. But there's one scenario that we have to
* look out for:
*
* - vblock x in a cache block
* - domotion occurs
* - cache block gets reallocated and over written
* - crash
*
* When we recover, because there was no commit the cache will
* rollback to having the data for vblock x in the cache block.
* But the cache block has since been overwritten, so it'll end
* up pointing to data that was never in 'x' during the history
* of the device.
*
* To avoid this issue we require a commit as part of the
* demotion operation.
*/
init_continuation(&mg->k, mg_success);
continue_after_commit(&cache->committer, &mg->k);
schedule_commit(&cache->committer);
break;
case POLICY_WRITEBACK:
mg_complete(mg, true);
break;
}
}
static void mg_update_metadata_after_copy(struct work_struct *ws)
{
struct dm_cache_migration *mg = ws_to_mg(ws);
/*
* Did the copy succeed?
*/
if (mg->k.input)
mg_complete(mg, false);
else
mg_update_metadata(ws);
}
static void mg_upgrade_lock(struct work_struct *ws)
{
int r;
struct dm_cache_migration *mg = ws_to_mg(ws);
/*
* Did the copy succeed?
*/
if (mg->k.input)
mg_complete(mg, false);
else {
/*
* Now we want the lock to prevent both reads and writes.
*/
r = dm_cell_lock_promote_v2(mg->cache->prison, mg->cell,
READ_WRITE_LOCK_LEVEL);
if (r < 0)
mg_complete(mg, false);
else if (r)
quiesce(mg, mg_update_metadata);
else
mg_update_metadata(ws);
}
}
static void mg_full_copy(struct work_struct *ws)
{
struct dm_cache_migration *mg = ws_to_mg(ws);
struct cache *cache = mg->cache;
struct policy_work *op = mg->op;
bool is_policy_promote = (op->op == POLICY_PROMOTE);
if ((!is_policy_promote && !is_dirty(cache, op->cblock)) ||
is_discarded_oblock(cache, op->oblock)) {
mg_upgrade_lock(ws);
return;
}
init_continuation(&mg->k, mg_upgrade_lock);
copy(mg, is_policy_promote);
}
static void mg_copy(struct work_struct *ws)
{
struct dm_cache_migration *mg = ws_to_mg(ws);
if (mg->overwrite_bio) {
/*
* No exclusive lock was held when we last checked if the bio
* was optimisable. So we have to check again in case things
* have changed (eg, the block may no longer be discarded).
*/
if (!optimisable_bio(mg->cache, mg->overwrite_bio, mg->op->oblock)) {
/*
* Fallback to a real full copy after doing some tidying up.
*/
bool rb = bio_detain_shared(mg->cache, mg->op->oblock, mg->overwrite_bio);
BUG_ON(rb); /* An exclussive lock must _not_ be held for this block */
mg->overwrite_bio = NULL;
inc_io_migrations(mg->cache);
mg_full_copy(ws);
return;
}
/*
* It's safe to do this here, even though it's new data
* because all IO has been locked out of the block.
*
* mg_lock_writes() already took READ_WRITE_LOCK_LEVEL
* so _not_ using mg_upgrade_lock() as continutation.
*/
overwrite(mg, mg_update_metadata_after_copy);
} else
mg_full_copy(ws);
}
static int mg_lock_writes(struct dm_cache_migration *mg)
{
int r;
struct dm_cell_key_v2 key;
struct cache *cache = mg->cache;
struct dm_bio_prison_cell_v2 *prealloc;
prealloc = alloc_prison_cell(cache);
/*
* Prevent writes to the block, but allow reads to continue.
* Unless we're using an overwrite bio, in which case we lock
* everything.
*/
build_key(mg->op->oblock, oblock_succ(mg->op->oblock), &key);
r = dm_cell_lock_v2(cache->prison, &key,
mg->overwrite_bio ? READ_WRITE_LOCK_LEVEL : WRITE_LOCK_LEVEL,
prealloc, &mg->cell);
if (r < 0) {
free_prison_cell(cache, prealloc);
mg_complete(mg, false);
return r;
}
if (mg->cell != prealloc)
free_prison_cell(cache, prealloc);
if (r == 0)
mg_copy(&mg->k.ws);
else
quiesce(mg, mg_copy);
return 0;
}
static int mg_start(struct cache *cache, struct policy_work *op, struct bio *bio)
{
struct dm_cache_migration *mg;
if (!background_work_begin(cache)) {
policy_complete_background_work(cache->policy, op, false);
return -EPERM;
}
mg = alloc_migration(cache);
mg->op = op;
mg->overwrite_bio = bio;
if (!bio)
inc_io_migrations(cache);
return mg_lock_writes(mg);
}
/*----------------------------------------------------------------
* invalidation processing
*--------------------------------------------------------------*/
static void invalidate_complete(struct dm_cache_migration *mg, bool success)
{
struct bio_list bios;
struct cache *cache = mg->cache;
bio_list_init(&bios);
if (dm_cell_unlock_v2(cache->prison, mg->cell, &bios))
free_prison_cell(cache, mg->cell);
if (!success && mg->overwrite_bio)
bio_io_error(mg->overwrite_bio);
free_migration(mg);
defer_bios(cache, &bios);
background_work_end(cache);
}
static void invalidate_completed(struct work_struct *ws)
{
struct dm_cache_migration *mg = ws_to_mg(ws);
invalidate_complete(mg, !mg->k.input);
}
static int invalidate_cblock(struct cache *cache, dm_cblock_t cblock)
{
int r = policy_invalidate_mapping(cache->policy, cblock);
if (!r) {
r = dm_cache_remove_mapping(cache->cmd, cblock);
if (r) {
DMERR_LIMIT("%s: invalidation failed; couldn't update on disk metadata",
cache_device_name(cache));
metadata_operation_failed(cache, "dm_cache_remove_mapping", r);
}
} else if (r == -ENODATA) {
/*
* Harmless, already unmapped.
*/
r = 0;
} else
DMERR("%s: policy_invalidate_mapping failed", cache_device_name(cache));
return r;
}
static void invalidate_remove(struct work_struct *ws)
{
int r;
struct dm_cache_migration *mg = ws_to_mg(ws);
struct cache *cache = mg->cache;
r = invalidate_cblock(cache, mg->invalidate_cblock);
if (r) {
invalidate_complete(mg, false);
return;
}
init_continuation(&mg->k, invalidate_completed);
continue_after_commit(&cache->committer, &mg->k);
remap_to_origin_clear_discard(cache, mg->overwrite_bio, mg->invalidate_oblock);
mg->overwrite_bio = NULL;
schedule_commit(&cache->committer);
}
static int invalidate_lock(struct dm_cache_migration *mg)
{
int r;
struct dm_cell_key_v2 key;
struct cache *cache = mg->cache;
struct dm_bio_prison_cell_v2 *prealloc;
prealloc = alloc_prison_cell(cache);
build_key(mg->invalidate_oblock, oblock_succ(mg->invalidate_oblock), &key);
r = dm_cell_lock_v2(cache->prison, &key,
READ_WRITE_LOCK_LEVEL, prealloc, &mg->cell);
if (r < 0) {
free_prison_cell(cache, prealloc);
invalidate_complete(mg, false);
return r;
}
if (mg->cell != prealloc)
free_prison_cell(cache, prealloc);
if (r)
quiesce(mg, invalidate_remove);
else {
/*
* We can't call invalidate_remove() directly here because we
* might still be in request context.
*/
init_continuation(&mg->k, invalidate_remove);
queue_work(cache->wq, &mg->k.ws);
}
return 0;
}
static int invalidate_start(struct cache *cache, dm_cblock_t cblock,
dm_oblock_t oblock, struct bio *bio)
{
struct dm_cache_migration *mg;
if (!background_work_begin(cache))
return -EPERM;
mg = alloc_migration(cache);
mg->overwrite_bio = bio;
mg->invalidate_cblock = cblock;
mg->invalidate_oblock = oblock;
return invalidate_lock(mg);
}
/*----------------------------------------------------------------
* bio processing
*--------------------------------------------------------------*/
enum busy {
IDLE,
BUSY
};
static enum busy spare_migration_bandwidth(struct cache *cache)
{
bool idle = iot_idle_for(&cache->tracker, HZ);
sector_t current_volume = (atomic_read(&cache->nr_io_migrations) + 1) *
cache->sectors_per_block;
if (idle && current_volume <= cache->migration_threshold)
return IDLE;
else
return BUSY;
}
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 int map_bio(struct cache *cache, struct bio *bio, dm_oblock_t block,
bool *commit_needed)
{
int r, data_dir;
bool rb, background_queued;
dm_cblock_t cblock;
*commit_needed = false;
rb = bio_detain_shared(cache, block, bio);
if (!rb) {
/*
* An exclusive lock is held for this block, so we have to
* wait. We set the commit_needed flag so the current
* transaction will be committed asap, allowing this lock
* to be dropped.
*/
*commit_needed = true;
return DM_MAPIO_SUBMITTED;
}
data_dir = bio_data_dir(bio);
if (optimisable_bio(cache, bio, block)) {
struct policy_work *op = NULL;
r = policy_lookup_with_work(cache->policy, block, &cblock, data_dir, true, &op);
if (unlikely(r && r != -ENOENT)) {
DMERR_LIMIT("%s: policy_lookup_with_work() failed with r = %d",
cache_device_name(cache), r);
bio_io_error(bio);
return DM_MAPIO_SUBMITTED;
}
if (r == -ENOENT && op) {
bio_drop_shared_lock(cache, bio);
BUG_ON(op->op != POLICY_PROMOTE);
mg_start(cache, op, bio);
return DM_MAPIO_SUBMITTED;
}
} else {
r = policy_lookup(cache->policy, block, &cblock, data_dir, false, &background_queued);
if (unlikely(r && r != -ENOENT)) {
DMERR_LIMIT("%s: policy_lookup() failed with r = %d",
cache_device_name(cache), r);
bio_io_error(bio);
return DM_MAPIO_SUBMITTED;
}
if (background_queued)
wake_migration_worker(cache);
}
if (r == -ENOENT) {
struct per_bio_data *pb = get_per_bio_data(bio);
/*
* Miss.
*/
inc_miss_counter(cache, bio);
if (pb->req_nr == 0) {
accounted_begin(cache, bio);
remap_to_origin_clear_discard(cache, bio, block);
} else {
/*
* This is a duplicate writethrough io that is no
* longer needed because the block has been demoted.
*/
bio_endio(bio);
return DM_MAPIO_SUBMITTED;
}
} else {
/*
* Hit.
*/
inc_hit_counter(cache, bio);
/*
* Passthrough always maps to the origin, invalidating any
* cache blocks that are written to.
*/
if (passthrough_mode(cache)) {
if (bio_data_dir(bio) == WRITE) {
bio_drop_shared_lock(cache, bio);
atomic_inc(&cache->stats.demotion);
invalidate_start(cache, cblock, block, bio);
} else
remap_to_origin_clear_discard(cache, bio, block);
} else {
if (bio_data_dir(bio) == WRITE && writethrough_mode(cache) &&
!is_dirty(cache, cblock)) {
remap_to_origin_and_cache(cache, bio, block, cblock);
accounted_begin(cache, bio);
} else
remap_to_cache_dirty(cache, bio, block, cblock);
}
}
/*
* dm core turns FUA requests into a separate payload and FLUSH req.
*/
if (bio->bi_opf & REQ_FUA) {
/*
* issue_after_commit will call accounted_begin a second time. So
* we call accounted_complete() to avoid double accounting.
*/
accounted_complete(cache, bio);
issue_after_commit(&cache->committer, bio);
*commit_needed = true;
return DM_MAPIO_SUBMITTED;
}
return DM_MAPIO_REMAPPED;
}
static bool process_bio(struct cache *cache, struct bio *bio)
{
bool commit_needed;
if (map_bio(cache, bio, get_bio_block(cache, bio), &commit_needed) == DM_MAPIO_REMAPPED)
generic_make_request(bio);
return commit_needed;
}
/*
* A non-zero return indicates read_only or fail_io mode.
*/
static int commit(struct cache *cache, bool clean_shutdown)
{
int r;
if (get_cache_mode(cache) >= CM_READ_ONLY)
return -EINVAL;
atomic_inc(&cache->stats.commit_count);
r = dm_cache_commit(cache->cmd, clean_shutdown);
if (r)
metadata_operation_failed(cache, "dm_cache_commit", r);
return r;
}
/*
* Used by the batcher.
*/
static blk_status_t commit_op(void *context)
{
struct cache *cache = context;
if (dm_cache_changed_this_transaction(cache->cmd))
return errno_to_blk_status(commit(cache, false));
return 0;
}
/*----------------------------------------------------------------*/
static bool process_flush_bio(struct cache *cache, struct bio *bio)
{
struct per_bio_data *pb = get_per_bio_data(bio);
if (!pb->req_nr)
remap_to_origin(cache, bio);
else
remap_to_cache(cache, bio, 0);
issue_after_commit(&cache->committer, bio);
return true;
}
static bool process_discard_bio(struct cache *cache, struct bio *bio)
{
dm_dblock_t b, e;
// FIXME: do we need to lock the region? Or can we just assume the
// user wont be so foolish as to issue discard concurrently with
// other IO?
calc_discard_block_range(cache, bio, &b, &e);
while (b != e) {
set_discard(cache, b);
b = to_dblock(from_dblock(b) + 1);
}
if (cache->features.discard_passdown) {
remap_to_origin(cache, bio);
generic_make_request(bio);
} else
bio_endio(bio);
return false;
}
static void process_deferred_bios(struct work_struct *ws)
{
struct cache *cache = container_of(ws, struct cache, deferred_bio_worker);
unsigned long flags;
bool commit_needed = false;
struct bio_list bios;
struct bio *bio;
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 = bio_list_pop(&bios))) {
if (bio->bi_opf & REQ_PREFLUSH)
commit_needed = process_flush_bio(cache, bio) || commit_needed;
else if (bio_op(bio) == REQ_OP_DISCARD)
commit_needed = process_discard_bio(cache, bio) || commit_needed;
else
commit_needed = process_bio(cache, bio) || commit_needed;
}
if (commit_needed)
schedule_commit(&cache->committer);
}
/*----------------------------------------------------------------
* Main worker loop
*--------------------------------------------------------------*/
static void requeue_deferred_bios(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->bi_status = BLK_STS_DM_REQUEUE;
bio_endio(bio);
}
}
/*
* 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, true);
wake_migration_worker(cache);
schedule_commit(&cache->committer);
queue_delayed_work(cache->wq, &cache->waker, COMMIT_PERIOD);
}
static void check_migrations(struct work_struct *ws)
{
int r;
struct policy_work *op;
struct cache *cache = container_of(ws, struct cache, migration_worker);
enum busy b;
for (;;) {
b = spare_migration_bandwidth(cache);
r = policy_get_background_work(cache->policy, b == IDLE, &op);
if (r == -ENODATA)
break;
if (r) {
DMERR_LIMIT("%s: policy_background_work failed",
cache_device_name(cache));
break;
}
r = mg_start(cache, op, NULL);
if (r)
break;
}
}
/*----------------------------------------------------------------
* 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;
mempool_exit(&cache->migration_pool);
if (cache->prison)
dm_bio_prison_destroy_v2(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);
bioset_exit(&cache->bs);
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 block_size;
if (!at_least_one_arg(as, error))
return -EINVAL;
if (kstrtoul(dm_shift_arg(as), 10, &block_size) || !block_size ||
block_size < DATA_DEV_BLOCK_SIZE_MIN_SECTORS ||
block_size > DATA_DEV_BLOCK_SIZE_MAX_SECTORS ||
block_size & (DATA_DEV_BLOCK_SIZE_MIN_SECTORS - 1)) {
*error = "Invalid data block size";
return -EINVAL;
}
if (block_size > ca->cache_sectors) {
*error = "Data block size is larger than the cache device";
return -EINVAL;
}
ca->block_size = block_size;
return 0;
}
static void init_features(struct cache_features *cf)
{
cf->mode = CM_WRITE;
cf->io_mode = CM_IO_WRITEBACK;
cf->metadata_version = 1;
cf->discard_passdown = true;
}
static int parse_features(struct cache_args *ca, struct dm_arg_set *as,
char **error)
{
static const struct dm_arg _args[] = {
{0, 3, "Invalid number of cache feature arguments"},
};
int r, mode_ctr = 0;
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->io_mode = CM_IO_WRITEBACK;
mode_ctr++;
}
else if (!strcasecmp(arg, "writethrough")) {
cf->io_mode = CM_IO_WRITETHROUGH;
mode_ctr++;
}
else if (!strcasecmp(arg, "passthrough")) {
cf->io_mode = CM_IO_PASSTHROUGH;
mode_ctr++;
}
else if (!strcasecmp(arg, "metadata2"))
cf->metadata_version = 2;
else if (!strcasecmp(arg, "no_discard_passdown"))
cf->discard_passdown = false;
else {
*error = "Unrecognised cache feature requested";
return -EINVAL;
}
}
if (mode_ctr > 1) {
*error = "Duplicate cache io_mode features requested";
return -EINVAL;
}
return 0;
}
static int parse_policy(struct cache_args *ca, struct dm_arg_set *as,
char **error)
{
static const 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)
{
struct dm_cache_policy *p = dm_cache_policy_create(ca->policy_name,
cache->cache_size,
cache->origin_sectors,
cache->sectors_per_block);
if (IS_ERR(p)) {
*error = "Error creating cache's policy";
return PTR_ERR(p);
}
cache->policy = p;
BUG_ON(!cache->policy);
return 0;
}
/*
* We want the discard block size to be 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 = cache_block_size;
if (origin_size)
while (too_many_discard_blocks(discard_block_size, origin_size))
discard_block_size *= 2;
return discard_block_size;
}
static void set_cache_size(struct cache *cache, dm_cblock_t size)
{
dm_block_t nr_blocks = from_cblock(size);
if (nr_blocks > (1 << 20) && cache->cache_size != size)
DMWARN_LIMIT("You have created a cache device with a lot of individual cache blocks (%llu)\n"
"All these mappings can consume a lot of kernel memory, and take some time to read/write.\n"
"Please consider increasing the cache block size to reduce the overall cache block count.",
(unsigned long long) nr_blocks);
cache->cache_size = size;
}
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);
}
#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->per_io_data_size = sizeof(struct per_bio_data);
cache->features = ca->features;
if (writethrough_mode(cache)) {
/* Create bioset for writethrough bios issued to origin */
r = bioset_init(&cache->bs, BIO_POOL_SIZE, 0, 0);
if (r)
goto bad;
}
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;
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);
set_cache_size(cache, to_cblock(cache_size));
} else {
cache->sectors_per_block_shift = __ffs(ca->block_size);
set_cache_size(cache, 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),
ca->features.metadata_version);
if (IS_ERR(cmd)) {
*error = "Error creating metadata object";
r = PTR_ERR(cmd);
goto bad;
}
cache->cmd = cmd;
set_cache_mode(cache, CM_WRITE);
if (get_cache_mode(cache) != CM_WRITE) {
*error = "Unable to get write access to metadata, please check/repair metadata.";
r = -EINVAL;
goto bad;
}
if (passthrough_mode(cache)) {
bool all_clean;
r = dm_cache_metadata_all_clean(cache->cmd, &all_clean);
if (r) {
*error = "dm_cache_metadata_all_clean() failed";
goto bad;
}
if (!all_clean) {
*error = "Cannot enter passthrough mode unless all blocks are clean";
r = -EINVAL;
goto bad;
}
policy_allow_migrations(cache->policy, false);
}
spin_lock_init(&cache->lock);
bio_list_init(&cache->deferred_bios);
atomic_set(&cache->nr_allocated_migrations, 0);
atomic_set(&cache->nr_io_migrations, 0);
init_waitqueue_head(&cache->migration_wait);
r = -ENOMEM;
atomic_set(&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 = to_dblock(dm_sector_div_up(cache->origin_sectors,
cache->discard_block_size));
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_workqueue("dm-" DM_MSG_PREFIX, WQ_MEM_RECLAIM, 0);
if (!cache->wq) {
*error = "could not create workqueue for metadata object";
goto bad;
}
INIT_WORK(&cache->deferred_bio_worker, process_deferred_bios);
INIT_WORK(&cache->migration_worker, check_migrations);
INIT_DELAYED_WORK(&cache->waker, do_waker);
cache->prison = dm_bio_prison_create_v2(cache->wq);
if (!cache->prison) {
*error = "could not create bio prison";
goto bad;
}
r = mempool_init_slab_pool(&cache->migration_pool, MIGRATION_POOL_SIZE,
migration_cache);
if (r) {
*error = "Error creating cache's migration mempool";
goto bad;
}
cache->need_tick_bio = true;
cache->sized = false;
cache->invalidate = 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);
spin_lock_init(&cache->invalidation_lock);
INIT_LIST_HEAD(&cache->invalidation_requests);
batcher_init(&cache->committer, commit_op, cache,
issue_op, cache, cache->wq);
iot_init(&cache->tracker);
init_rwsem(&cache->background_work_lock);
prevent_background_work(cache);
*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;
bool commit_needed;
dm_oblock_t block = get_bio_block(cache, bio);
init_per_bio_data(bio);
if (unlikely(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(cache, bio);
accounted_begin(cache, bio);
return DM_MAPIO_REMAPPED;
}
if (discard_or_flush(bio)) {
defer_bio(cache, bio);
return DM_MAPIO_SUBMITTED;
}
r = map_bio(cache, bio, block, &commit_needed);
if (commit_needed)
schedule_commit(&cache->committer);
return r;
}
static int cache_end_io(struct dm_target *ti, struct bio *bio, blk_status_t *error)
{
struct cache *cache = ti->private;
unsigned long flags;
struct per_bio_data *pb = get_per_bio_data(bio);
if (pb->tick) {
policy_tick(cache->policy, false);
spin_lock_irqsave(&cache->lock, flags);
cache->need_tick_bio = true;
spin_unlock_irqrestore(&cache->lock, flags);
}
bio_drop_shared_lock(cache, bio);
accounted_complete(cache, bio);
return DM_ENDIO_DONE;
}
static int write_dirty_bitset(struct cache *cache)
{
int r;
if (get_cache_mode(cache) >= CM_READ_ONLY)
return -EINVAL;
r = dm_cache_set_dirty_bits(cache->cmd, from_cblock(cache->cache_size), cache->dirty_bitset);
if (r)
metadata_operation_failed(cache, "dm_cache_set_dirty_bits", r);
return r;
}
static int write_discard_bitset(struct cache *cache)
{
unsigned i, r;
if (get_cache_mode(cache) >= CM_READ_ONLY)
return -EINVAL;
r = dm_cache_discard_bitset_resize(cache->cmd, cache->discard_block_size,
cache->discard_nr_blocks);
if (r) {
DMERR("%s: could not resize on-disk discard bitset", cache_device_name(cache));
metadata_operation_failed(cache, "dm_cache_discard_bitset_resize", r);
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) {
metadata_operation_failed(cache, "dm_cache_set_discard", r);
return r;
}
}
return 0;
}
static int write_hints(struct cache *cache)
{
int r;
if (get_cache_mode(cache) >= CM_READ_ONLY)
return -EINVAL;
r = dm_cache_write_hints(cache->cmd, cache->policy);
if (r) {
metadata_operation_failed(cache, "dm_cache_write_hints", r);
return r;
}
return 0;
}
/*
* returns true on success
*/
static bool sync_metadata(struct cache *cache)
{
int r1, r2, r3, r4;
r1 = write_dirty_bitset(cache);
if (r1)
DMERR("%s: could not write dirty bitset", cache_device_name(cache));
r2 = write_discard_bitset(cache);
if (r2)
DMERR("%s: could not write discard bitset", cache_device_name(cache));
save_stats(cache);
r3 = write_hints(cache);
if (r3)
DMERR("%s: could not write hints", cache_device_name(cache));
/*
* 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 = commit(cache, !r1 && !r2 && !r3);
if (r4)
DMERR("%s: could not write cache metadata", cache_device_name(cache));
return !r1 && !r2 && !r3 && !r4;
}
static void cache_postsuspend(struct dm_target *ti)
{
struct cache *cache = ti->private;
prevent_background_work(cache);
BUG_ON(atomic_read(&cache->nr_io_migrations));
cancel_delayed_work_sync(&cache->waker);
drain_workqueue(cache->wq);
WARN_ON(cache->tracker.in_flight);
/*
* If it's a flush suspend there won't be any deferred bios, so this
* call is harmless.
*/
requeue_deferred_bios(cache);
if (get_cache_mode(cache) == CM_WRITE)
(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;
if (dirty) {
set_bit(from_cblock(cblock), cache->dirty_bitset);
atomic_inc(&cache->nr_dirty);
} else
clear_bit(from_cblock(cblock), cache->dirty_bitset);
r = policy_load_mapping(cache->policy, oblock, cblock, dirty, hint, hint_valid);
if (r)
return r;
return 0;
}
/*
* The discard block size in the on disk metadata is not
* neccessarily the same as we're currently using. So we have to
* be careful to only set the discarded attribute if we know it
* covers a complete block of the new size.
*/
struct discard_load_info {
struct cache *cache;
/*
* These blocks are sized using the on disk dblock size, rather
* than the current one.
*/
dm_block_t block_size;
dm_block_t discard_begin, discard_end;
};
static void discard_load_info_init(struct cache *cache,
struct discard_load_info *li)
{
li->cache = cache;
li->discard_begin = li->discard_end = 0;
}
static void set_discard_range(struct discard_load_info *li)
{
sector_t b, e;
if (li->discard_begin == li->discard_end)
return;
/*
* Convert to sectors.
*/
b = li->discard_begin * li->block_size;
e = li->discard_end * li->block_size;
/*
* Then convert back to the current dblock size.
*/
b = dm_sector_div_up(b, li->cache->discard_block_size);
sector_div(e, li->cache->discard_block_size);
/*
* The origin may have shrunk, so we need to check we're still in
* bounds.
*/
if (e > from_dblock(li->cache->discard_nr_blocks))
e = from_dblock(li->cache->discard_nr_blocks);
for (; b < e; b++)
set_discard(li->cache, to_dblock(b));
}
static int load_discard(void *context, sector_t discard_block_size,
dm_dblock_t dblock, bool discard)
{
struct discard_load_info *li = context;
li->block_size = discard_block_size;
if (discard) {
if (from_dblock(dblock) == li->discard_end)
/*
* We're already in a discard range, just extend it.
*/
li->discard_end = li->discard_end + 1ULL;
else {
/*
* Emit the old range and start a new one.
*/
set_discard_range(li);
li->discard_begin = from_dblock(dblock);
li->discard_end = li->discard_begin + 1ULL;
}
} else {
set_discard_range(li);
li->discard_begin = li->discard_end = 0;
}
return 0;
}
static dm_cblock_t get_cache_dev_size(struct cache *cache)
{
sector_t size = get_dev_size(cache->cache_dev);
(void) sector_div(size, cache->sectors_per_block);
return to_cblock(size);
}
static bool can_resize(struct cache *cache, dm_cblock_t new_size)
{
if (from_cblock(new_size) > from_cblock(cache->cache_size)) {
if (cache->sized) {
DMERR("%s: unable to extend cache due to missing cache table reload",
cache_device_name(cache));
return false;
}
}
/*
* We can't drop a dirty block when shrinking the cache.
*/
while (from_cblock(new_size) < from_cblock(cache->cache_size)) {
new_size = to_cblock(from_cblock(new_size) + 1);
if (is_dirty(cache, new_size)) {
DMERR("%s: unable to shrink cache; cache block %llu is dirty",
cache_device_name(cache),
(unsigned long long) from_cblock(new_size));
return false;
}
}
return true;
}
static int resize_cache_dev(struct cache *cache, dm_cblock_t new_size)
{
int r;
r = dm_cache_resize(cache->cmd, new_size);
if (r) {
DMERR("%s: could not resize cache metadata", cache_device_name(cache));
metadata_operation_failed(cache, "dm_cache_resize", r);
return r;
}
set_cache_size(cache, new_size);
return 0;
}
static int cache_preresume(struct dm_target *ti)
{
int r = 0;
struct cache *cache = ti->private;
dm_cblock_t csize = get_cache_dev_size(cache);
/*
* Check to see if the cache has resized.
*/
if (!cache->sized) {
r = resize_cache_dev(cache, csize);
if (r)
return r;
cache->sized = true;
} else if (csize != cache->cache_size) {
if (!can_resize(cache, csize))
return -EINVAL;
r = resize_cache_dev(cache, csize);
if (r)
return r;
}
if (!cache->loaded_mappings) {
r = dm_cache_load_mappings(cache->cmd, cache->policy,
load_mapping, cache);
if (r) {
DMERR("%s: could not load cache mappings", cache_device_name(cache));
metadata_operation_failed(cache, "dm_cache_load_mappings", r);
return r;
}
cache->loaded_mappings = true;
}
if (!cache->loaded_discards) {
struct discard_load_info li;
/*
* The discard bitset could have been resized, or the
* discard block size changed. To be safe we start by
* setting every dblock to not discarded.
*/
clear_bitset(cache->discard_bitset, from_dblock(cache->discard_nr_blocks));
discard_load_info_init(cache, &li);
r = dm_cache_load_discards(cache->cmd, load_discard, &li);
if (r) {
DMERR("%s: could not load origin discards", cache_device_name(cache));
metadata_operation_failed(cache, "dm_cache_load_discards", r);
return r;
}
set_discard_range(&li);
cache->loaded_discards = true;
}
return r;
}
static void cache_resume(struct dm_target *ti)
{
struct cache *cache = ti->private;
cache->need_tick_bio = true;
allow_background_work(cache);
do_waker(&cache->waker.work);
}
static void emit_flags(struct cache *cache, char *result,
unsigned maxlen, ssize_t *sz_ptr)
{
ssize_t sz = *sz_ptr;
struct cache_features *cf = &cache->features;
unsigned count = (cf->metadata_version == 2) + !cf->discard_passdown + 1;
DMEMIT("%u ", count);
if (cf->metadata_version == 2)
DMEMIT("metadata2 ");
if (writethrough_mode(cache))
DMEMIT("writethrough ");
else if (passthrough_mode(cache))
DMEMIT("passthrough ");
else if (writeback_mode(cache))
DMEMIT("writeback ");
else {
DMEMIT("unknown ");
DMERR("%s: internal error: unknown io mode: %d",
cache_device_name(cache), (int) cf->io_mode);
}
if (!cf->discard_passdown)
DMEMIT("no_discard_passdown ");
*sz_ptr = sz;
}
/*
* Status format:
*
* <metadata block size> <#used metadata blocks>/<#total metadata blocks>
* <cache block size> <#used cache blocks>/<#total cache blocks>
* <#read hits> <#read misses> <#write hits> <#write misses>
* <#demotions> <#promotions> <#dirty>
* <#features> <features>*
* <#core args> <core args>
* <policy name> <#policy args> <policy args>* <cache metadata mode> <needs_check>
*/
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;
bool needs_check;
switch (type) {
case STATUSTYPE_INFO:
if (get_cache_mode(cache) == CM_FAIL) {
DMEMIT("Fail");
break;
}
/* Commit to ensure statistics aren't out-of-date */
if (!(status_flags & DM_STATUS_NOFLUSH_FLAG) && !dm_suspended(ti))
(void) commit(cache, false);
r = dm_cache_get_free_metadata_block_count(cache->cmd, &nr_free_blocks_metadata);
if (r) {
DMERR("%s: dm_cache_get_free_metadata_block_count returned %d",
cache_device_name(cache), r);
goto err;
}
r = dm_cache_get_metadata_dev_size(cache->cmd, &nr_blocks_metadata);
if (r) {
DMERR("%s: dm_cache_get_metadata_dev_size returned %d",
cache_device_name(cache), r);
goto err;
}
residency = policy_residency(cache->policy);
DMEMIT("%u %llu/%llu %llu %llu/%llu %u %u %u %u %u %u %lu ",
(unsigned)DM_CACHE_METADATA_BLOCK_SIZE,
(unsigned long long)(nr_blocks_metadata - nr_free_blocks_metadata),
(unsigned long long)nr_blocks_metadata,
(unsigned long long)cache->sectors_per_block,
(unsigned long long) from_cblock(residency),
(unsigned long long) from_cblock(cache->cache_size),
(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) atomic_read(&cache->nr_dirty));
emit_flags(cache, result, maxlen, &sz);
DMEMIT("2 migration_threshold %llu ", (unsigned long long) cache->migration_threshold);
DMEMIT("%s ", dm_cache_policy_get_name(cache->policy));
if (sz < maxlen) {
r = policy_emit_config_values(cache->policy, result, maxlen, &sz);
if (r)
DMERR("%s: policy_emit_config_values returned %d",
cache_device_name(cache), r);
}
if (get_cache_mode(cache) == CM_READ_ONLY)
DMEMIT("ro ");
else
DMEMIT("rw ");
r = dm_cache_metadata_needs_check(cache->cmd, &needs_check);
if (r || needs_check)
DMEMIT("needs_check ");
else
DMEMIT("- ");
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");
}
/*
* Defines a range of cblocks, begin to (end - 1) are in the range. end is
* the one-past-the-end value.
*/
struct cblock_range {
dm_cblock_t begin;
dm_cblock_t end;
};
/*
* A cache block range can take two forms:
*
* i) A single cblock, eg. '3456'
* ii) A begin and end cblock with a dash between, eg. 123-234
*/
static int parse_cblock_range(struct cache *cache, const char *str,
struct cblock_range *result)
{
char dummy;
uint64_t b, e;
int r;
/*
* Try and parse form (ii) first.
*/
r = sscanf(str, "%llu-%llu%c", &b, &e, &dummy);
if (r < 0)
return r;
if (r == 2) {
result->begin = to_cblock(b);
result->end = to_cblock(e);
return 0;
}
/*
* That didn't work, try form (i).
*/
r = sscanf(str, "%llu%c", &b, &dummy);
if (r < 0)
return r;
if (r == 1) {
result->begin = to_cblock(b);
result->end = to_cblock(from_cblock(result->begin) + 1u);
return 0;
}
DMERR("%s: invalid cblock range '%s'", cache_device_name(cache), str);
return -EINVAL;
}
static int validate_cblock_range(struct cache *cache, struct cblock_range *range)
{
uint64_t b = from_cblock(range->begin);
uint64_t e = from_cblock(range->end);
uint64_t n = from_cblock(cache->cache_size);
if (b >= n) {
DMERR("%s: begin cblock out of range: %llu >= %llu",
cache_device_name(cache), b, n);
return -EINVAL;
}
if (e > n) {
DMERR("%s: end cblock out of range: %llu > %llu",
cache_device_name(cache), e, n);
return -EINVAL;
}
if (b >= e) {
DMERR("%s: invalid cblock range: %llu >= %llu",
cache_device_name(cache), b, e);
return -EINVAL;
}
return 0;
}
static inline dm_cblock_t cblock_succ(dm_cblock_t b)
{
return to_cblock(from_cblock(b) + 1);
}
static int request_invalidation(struct cache *cache, struct cblock_range *range)
{
int r = 0;
/*
* We don't need to do any locking here because we know we're in
* passthrough mode. There's is potential for a race between an
* invalidation triggered by an io and an invalidation message. This
* is harmless, we must not worry if the policy call fails.
*/
while (range->begin != range->end) {
r = invalidate_cblock(cache, range->begin);
if (r)
return r;
range->begin = cblock_succ(range->begin);
}
cache->commit_requested = true;
return r;
}
static int process_invalidate_cblocks_message(struct cache *cache, unsigned count,
const char **cblock_ranges)
{
int r = 0;
unsigned i;
struct cblock_range range;
if (!passthrough_mode(cache)) {
DMERR("%s: cache has to be in passthrough mode for invalidation",
cache_device_name(cache));
return -EPERM;
}
for (i = 0; i < count; i++) {
r = parse_cblock_range(cache, cblock_ranges[i], &range);
if (r)
break;
r = validate_cblock_range(cache, &range);
if (r)
break;
/*
* Pass begin and end origin blocks to the worker and wake it.
*/
r = request_invalidation(cache, &range);
if (r)
break;
}
return r;
}
/*
* Supports
* "<key> <value>"
* and
* "invalidate_cblocks [(<begin>)|(<begin>-<end>)]*
*
* The key migration_threshold is supported by the cache target core.
*/
static int cache_message(struct dm_target *ti, unsigned argc, char **argv,
char *result, unsigned maxlen)
{
struct cache *cache = ti->private;
if (!argc)
return -EINVAL;
if (get_cache_mode(cache) >= CM_READ_ONLY) {
DMERR("%s: unable to service cache target messages in READ_ONLY or FAIL mode",
cache_device_name(cache));
return -EOPNOTSUPP;
}
if (!strcasecmp(argv[0], "invalidate_cblocks"))
return process_invalidate_cblocks_message(cache, argc - 1, (const char **) argv + 1);
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;
}
static bool origin_dev_supports_discard(struct block_device *origin_bdev)
{
struct request_queue *q = bdev_get_queue(origin_bdev);
return q && blk_queue_discard(q);
}
/*
* If discard_passdown was enabled verify that the origin device
* supports discards. Disable discard_passdown if not.
*/
static void disable_passdown_if_not_supported(struct cache *cache)
{
struct block_device *origin_bdev = cache->origin_dev->bdev;
struct queue_limits *origin_limits = &bdev_get_queue(origin_bdev)->limits;
const char *reason = NULL;
char buf[BDEVNAME_SIZE];
if (!cache->features.discard_passdown)
return;
if (!origin_dev_supports_discard(origin_bdev))
reason = "discard unsupported";
else if (origin_limits->max_discard_sectors < cache->sectors_per_block)
reason = "max discard sectors smaller than a block";
if (reason) {
DMWARN("Origin device (%s) %s: Disabling discard passdown.",
bdevname(origin_bdev, buf), reason);
cache->features.discard_passdown = false;
}
}
static void set_discard_limits(struct cache *cache, struct queue_limits *limits)
{
struct block_device *origin_bdev = cache->origin_dev->bdev;
struct queue_limits *origin_limits = &bdev_get_queue(origin_bdev)->limits;
if (!cache->features.discard_passdown) {
/* No passdown is done so setting own virtual limits */
limits->max_discard_sectors = min_t(sector_t, cache->discard_block_size * 1024,
cache->origin_sectors);
limits->discard_granularity = cache->discard_block_size << SECTOR_SHIFT;
return;
}
/*
* cache_iterate_devices() is stacking both origin and fast device limits
* but discards aren't passed to fast device, so inherit origin's limits.
*/
limits->max_discard_sectors = origin_limits->max_discard_sectors;
limits->max_hw_discard_sectors = origin_limits->max_hw_discard_sectors;
limits->discard_granularity = origin_limits->discard_granularity;
limits->discard_alignment = origin_limits->discard_alignment;
limits->discard_misaligned = origin_limits->discard_misaligned;
}
static void cache_io_hints(struct dm_target *ti, struct queue_limits *limits)
{
struct cache *cache = ti->private;
uint64_t io_opt_sectors = limits->io_opt >> SECTOR_SHIFT;
/*
* If the system-determined stacked limits are compatible with the
* cache's blocksize (io_opt is a factor) do not override them.
*/
if (io_opt_sectors < cache->sectors_per_block ||
do_div(io_opt_sectors, cache->sectors_per_block)) {
blk_limits_io_min(limits, cache->sectors_per_block << SECTOR_SHIFT);
blk_limits_io_opt(limits, cache->sectors_per_block << SECTOR_SHIFT);
}
disable_passdown_if_not_supported(cache);
set_discard_limits(cache, limits);
}
/*----------------------------------------------------------------*/
static struct target_type cache_target = {
.name = "cache",
.version = {2, 1, 0},
.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,
.io_hints = cache_io_hints,
};
static int __init dm_cache_init(void)
{
int r;
migration_cache = KMEM_CACHE(dm_cache_migration, 0);
if (!migration_cache)
return -ENOMEM;
r = dm_register_target(&cache_target);
if (r) {
DMERR("cache target registration failed: %d", r);
kmem_cache_destroy(migration_cache);
return r;
}
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");
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