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-rw-r--r--drivers/md/dm-cache-target.c3121
1 files changed, 3121 insertions, 0 deletions
diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c
new file mode 100644
index 00000000000..2c63326638b
--- /dev/null
+++ b/drivers/md/dm-cache-target.c
@@ -0,0 +1,3121 @@
+/*
+ * 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);
+}
+
+/*----------------------------------------------------------------*/
+
+/*
+ * 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;
+ void *bi_private;
+};
+
+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;
+ h->bi_private = bio->bi_private;
+
+ 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;
+ bio->bi_private = h->bi_private;
+
+ /*
+ * Must bump bi_remaining to allow bio to complete with
+ * restored bi_end_io.
+ */
+ atomic_inc(&bio->bi_remaining);
+}
+
+/*----------------------------------------------------------------*/
+
+#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
+ * 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)
+
+/*
+ * FIXME: the cache is read/write for the time being.
+ */
+enum cache_metadata_mode {
+ CM_WRITE, /* metadata may be changed */
+ CM_READ_ONLY, /* metadata may not be changed */
+};
+
+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;
+};
+
+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;
+};
+
+/*
+ * 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;
+};
+
+struct invalidation_request {
+ struct list_head list;
+ struct cblock_range *cblocks;
+
+ atomic_t complete;
+ int err;
+
+ wait_queue_head_t result_wait;
+};
+
+struct cache {
+ struct dm_target *ti;
+ struct dm_target_callbacks callbacks;
+
+ 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;
+
+ /*
+ * Fields for converting from sectors to blocks.
+ */
+ uint32_t sectors_per_block;
+ int sectors_per_block_shift;
+
+ 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;
+ wait_queue_head_t migration_wait;
+ atomic_t nr_migrations;
+
+ wait_queue_head_t quiescing_wait;
+ atomic_t quiescing;
+ atomic_t quiescing_ack;
+
+ /*
+ * cache_size entries, dirty if set
+ */
+ atomic_t nr_dirty;
+ unsigned long *dirty_bitset;
+
+ /*
+ * origin_blocks entries, discarded if set.
+ */
+ dm_oblock_t discard_nr_blocks;
+ unsigned long *discard_bitset;
+
+ /*
+ * 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 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 invalidate:1;
+ bool commit_requested:1;
+ bool loaded_mappings:1;
+ bool loaded_discards:1;
+
+ /*
+ * Cache features such as write-through.
+ */
+ struct cache_features features;
+
+ struct cache_stats stats;
+
+ /*
+ * Invalidation fields.
+ */
+ spinlock_t invalidation_lock;
+ struct list_head invalidation_requests;
+};
+
+struct per_bio_data {
+ bool tick:1;
+ unsigned req_nr:2;
+ struct dm_deferred_entry *all_io_entry;
+ struct dm_hook_info hook_info;
+
+ /*
+ * 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;
+ 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;
+ bool requeue_holder:1;
+ bool invalidate: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)) {
+ atomic_inc(&cache->nr_dirty);
+ 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);
+ if (atomic_dec_return(&cache->nr_dirty) == 0)
+ dm_table_event(cache->ti->table);
+ }
+}
+
+/*----------------------------------------------------------------*/
+
+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 void set_discard(struct cache *cache, dm_oblock_t b)
+{
+ unsigned long flags;
+
+ atomic_inc(&cache->stats.discard_count);
+
+ spin_lock_irqsave(&cache->lock, flags);
+ set_bit(from_oblock(b), cache->discard_bitset);
+ spin_unlock_irqrestore(&cache->lock, flags);
+}
+
+static void clear_discard(struct cache *cache, dm_oblock_t b)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&cache->lock, flags);
+ clear_bit(from_oblock(b), cache->discard_bitset);
+ spin_unlock_irqrestore(&cache->lock, flags);
+}
+
+static bool is_discarded(struct cache *cache, dm_oblock_t b)
+{
+ int r;
+ unsigned long flags;
+
+ spin_lock_irqsave(&cache->lock, flags);
+ r = test_bit(from_oblock(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_oblock(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 bool writethrough_mode(struct cache_features *f)
+{
+ return f->io_mode == CM_IO_WRITETHROUGH;
+}
+
+static bool writeback_mode(struct cache_features *f)
+{
+ return f->io_mode == CM_IO_WRITEBACK;
+}
+
+static bool passthrough_mode(struct cache_features *f)
+{
+ return f->io_mode == CM_IO_PASSTHROUGH;
+}
+
+static size_t get_per_bio_data_size(struct cache *cache)
+{
+ return writethrough_mode(&cache->features) ? 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_iter.bi_sector;
+ sector_t block = from_cblock(cblock);
+
+ bio->bi_bdev = 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;
+ 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);
+}
+
+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, oblock, cblock);
+ clear_discard(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 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);
+
+ dm_unhook_bio(&pb->hook_info, bio);
+
+ 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;
+ dm_hook_bio(&pb->hook_info, bio, writethrough_endio, NULL);
+ dm_bio_record(&pb->bio_details, bio);
+
+ 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)
+{
+ struct cache *cache = mg->cache;
+ free_migration(mg);
+ dec_nr_migrations(cache);
+}
+
+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 ? false : true);
+ if (mg->promote)
+ cell_defer(cache, mg->new_ocell, true);
+ } else {
+ DMWARN_LIMIT("promotion failed; couldn't copy block");
+ policy_remove_mapping(cache->policy, mg->new_oblock);
+ cell_defer(cache, mg->new_ocell, true);
+ }
+
+ 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 ? false : true);
+
+ 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 {
+ if (mg->invalidate)
+ policy_remove_mapping(cache->policy, mg->old_oblock);
+ cleanup_migration(mg);
+ }
+
+ } else {
+ if (mg->requeue_holder)
+ cell_defer(cache, mg->new_ocell, true);
+ else {
+ bio_endio(mg->new_ocell->holder, 0);
+ cell_defer(cache, mg->new_ocell, false);
+ }
+ 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;
+ sector_t cblock = from_cblock(mg->cblock);
+
+ o_region.bdev = cache->origin_dev->bdev;
+ o_region.count = cache->sectors_per_block;
+
+ c_region.bdev = cache->cache_dev->bdev;
+ c_region.sector = 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) {
+ DMERR_LIMIT("issuing migration failed");
+ migration_failure(mg);
+ }
+}
+
+static void overwrite_endio(struct bio *bio, int err)
+{
+ struct dm_cache_migration *mg = bio->bi_private;
+ struct cache *cache = mg->cache;
+ size_t pb_data_size = get_per_bio_data_size(cache);
+ struct per_bio_data *pb = get_per_bio_data(bio, pb_data_size);
+ unsigned long flags;
+
+ dm_unhook_bio(&pb->hook_info, bio);
+
+ if (err)
+ mg->err = true;
+
+ mg->requeue_holder = false;
+
+ 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_overwrite(struct dm_cache_migration *mg, struct bio *bio)
+{
+ size_t pb_data_size = get_per_bio_data_size(mg->cache);
+ struct per_bio_data *pb = get_per_bio_data(bio, pb_data_size);
+
+ dm_hook_bio(&pb->hook_info, bio, overwrite_endio, mg);
+ remap_to_cache_dirty(mg->cache, bio, mg->new_oblock, mg->cblock);
+ generic_make_request(bio);
+}
+
+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 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 {
+ struct bio *bio = mg->new_ocell->holder;
+
+ avoid = is_discarded_oblock(cache, mg->new_oblock);
+
+ if (!avoid && bio_writes_complete_block(cache, bio)) {
+ issue_overwrite(mg, bio);
+ return;
+ }
+ }
+
+ 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->requeue_holder = true;
+ mg->invalidate = false;
+ 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->requeue_holder = true;
+ mg->invalidate = 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->requeue_holder = true;
+ mg->invalidate = false;
+ 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);
+}
+
+/*
+ * Invalidate a cache entry. No writeback occurs; any changes in the cache
+ * block are thrown away.
+ */
+static void invalidate(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 = true;
+ mg->promote = false;
+ mg->requeue_holder = true;
+ mg->invalidate = true;
+ 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);
+}
+
+/*----------------------------------------------------------------
+ * 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_iter.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_iter.bi_sector,
+ cache->sectors_per_block);
+ dm_block_t end_block = bio_end_sector(bio);
+ dm_block_t b;
+
+ end_block = block_div(end_block, cache->sectors_per_block);
+
+ for (b = start_block; b < end_block; b++)
+ set_discard(cache, to_oblock(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 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 issue_cache_bio(struct cache *cache, struct bio *bio,
+ struct per_bio_data *pb,
+ dm_oblock_t oblock, dm_cblock_t cblock)
+{
+ pb->all_io_entry = dm_deferred_entry_inc(cache->all_io_ds);
+ remap_to_cache_dirty(cache, bio, oblock, cblock);
+ issue(cache, bio);
+}
+
+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 passthrough = passthrough_mode(&cache->features);
+ bool can_migrate = !passthrough && (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:
+ if (passthrough) {
+ inc_miss_counter(cache, bio);
+
+ /*
+ * Passthrough always maps to the origin,
+ * invalidating any cache blocks that are written
+ * to.
+ */
+
+ if (bio_data_dir(bio) == WRITE) {
+ atomic_inc(&cache->stats.demotion);
+ invalidate(cache, structs, block, lookup_result.cblock, new_ocell);
+ release_cell = false;
+
+ } else {
+ /* FIXME: factor out issue_origin() */
+ pb->all_io_entry = dm_deferred_entry_inc(cache->all_io_ds);
+ remap_to_origin_clear_discard(cache, bio, block);
+ issue(cache, bio);
+ }
+ } else {
+ inc_hit_counter(cache, bio);
+
+ if (bio_data_dir(bio) == WRITE &&
+ writethrough_mode(&cache->features) &&
+ !is_dirty(cache, lookup_result.cblock)) {
+ pb->all_io_entry = dm_deferred_entry_inc(cache->all_io_ds);
+ remap_to_origin_then_cache(cache, bio, block, lookup_result.cblock);
+ issue(cache, bio);
+ } else
+ issue_cache_bio(cache, bio, pb, block, lookup_result.cblock);
+ }
+
+ 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)
+{
+ int r = 0;
+
+ if ((cache->commit_requested || need_commit_due_to_time(cache)) &&
+ dm_cache_changed_this_transaction(cache->cmd)) {
+ atomic_inc(&cache->stats.commit_count);
+ cache->commit_requested = false;
+ r = dm_cache_commit(cache->cmd, false);
+ cache->last_commit_jiffies = jiffies;
+ }
+
+ return r;
+}
+
+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);
+}
+
+/*----------------------------------------------------------------
+ * Invalidations.
+ * Dropping something from the cache *without* writing back.
+ *--------------------------------------------------------------*/
+
+static void process_invalidation_request(struct cache *cache, struct invalidation_request *req)
+{
+ int r = 0;
+ uint64_t begin = from_cblock(req->cblocks->begin);
+ uint64_t end = from_cblock(req->cblocks->end);
+
+ while (begin != end) {
+ r = policy_remove_cblock(cache->policy, to_cblock(begin));
+ if (!r) {
+ r = dm_cache_remove_mapping(cache->cmd, to_cblock(begin));
+ if (r)
+ break;
+
+ } else if (r == -ENODATA) {
+ /* harmless, already unmapped */
+ r = 0;
+
+ } else {
+ DMERR("policy_remove_cblock failed");
+ break;
+ }
+
+ begin++;
+ }
+
+ cache->commit_requested = true;
+
+ req->err = r;
+ atomic_set(&req->complete, 1);
+
+ wake_up(&req->result_wait);
+}
+
+static void process_invalidation_requests(struct cache *cache)
+{
+ struct list_head list;
+ struct invalidation_request *req, *tmp;
+
+ INIT_LIST_HEAD(&list);
+ spin_lock(&cache->invalidation_lock);
+ list_splice_init(&cache->invalidation_requests, &list);
+ spin_unlock(&cache->invalidation_lock);
+
+ list_for_each_entry_safe (req, tmp, &list, list)
+ process_invalidation_request(cache, req);
+}
+
+/*----------------------------------------------------------------
+ * Main worker loop
+ *--------------------------------------------------------------*/
+static bool is_quiescing(struct cache *cache)
+{
+ return atomic_read(&cache->quiescing);
+}
+
+static void ack_quiescing(struct cache *cache)
+{
+ if (is_quiescing(cache)) {
+ atomic_inc(&cache->quiescing_ack);
+ wake_up(&cache->quiescing_wait);
+ }
+}
+
+static void wait_for_quiescing_ack(struct cache *cache)
+{
+ wait_event(cache->quiescing_wait, atomic_read(&cache->quiescing_ack));
+}
+
+static void start_quiescing(struct cache *cache)
+{
+ atomic_inc(&cache->quiescing);
+ wait_for_quiescing_ack(cache);
+}
+
+static void stop_quiescing(struct cache *cache)
+{
+ atomic_set(&cache->quiescing, 0);
+ atomic_set(&cache->quiescing_ack, 0);
+}
+
+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) ||
+ cache->invalidate;
+}
+
+static void do_worker(struct work_struct *ws)
+{
+ struct cache *cache = container_of(ws, struct cache, worker);
+
+ do {
+ if (!is_quiescing(cache)) {
+ writeback_some_dirty_blocks(cache);
+ process_deferred_writethrough_bios(cache);
+ process_deferred_bios(cache);
+ process_invalidation_requests(cache);
+ }
+
+ process_migrations(cache, &cache->quiesced_migrations, issue_copy);
+ process_migrations(cache, &cache->completed_migrations, complete_migration);
+
+ 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);
+ }
+
+ ack_quiescing(cache);
+
+ } 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 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;
+}
+
+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->io_mode = CM_IO_WRITEBACK;
+
+ else if (!strcasecmp(arg, "writethrough"))
+ cf->io_mode = CM_IO_WRITETHROUGH;
+
+ else if (!strcasecmp(arg, "passthrough"))
+ cf->io_mode = CM_IO_PASSTHROUGH;
+
+ 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)
+{
+ 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;
+
+ return 0;
+}
+
+#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;
+ /* Discard bios must be split on a block boundary */
+ ti->split_discard_bios = 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;
+
+ if (passthrough_mode(&cache->features)) {
+ 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;
+ }
+ }
+
+ 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);
+
+ init_waitqueue_head(&cache->quiescing_wait);
+ atomic_set(&cache->quiescing, 0);
+ atomic_set(&cache->quiescing_ack, 0);
+
+ 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_nr_blocks = cache->origin_blocks;
+ cache->discard_bitset = alloc_bitset(from_oblock(cache->discard_nr_blocks));
+ if (!cache->discard_bitset) {
+ *error = "could not allocate discard bitset";
+ goto bad;
+ }
+ clear_bitset(cache->discard_bitset, from_oblock(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->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);
+
+ *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 = init_per_bio_data(bio, pb_data_size);
+
+ 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);
+ return DM_MAPIO_REMAPPED;
+ }
+
+ 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;
+ }
+
+ r = DM_MAPIO_REMAPPED;
+ switch (lookup_result.op) {
+ case POLICY_HIT:
+ if (passthrough_mode(&cache->features)) {
+ if (bio_data_dir(bio) == WRITE) {
+ /*
+ * We need to invalidate this block, so
+ * defer for the worker thread.
+ */
+ cell_defer(cache, cell, true);
+ r = DM_MAPIO_SUBMITTED;
+
+ } else {
+ pb->all_io_entry = dm_deferred_entry_inc(cache->all_io_ds);
+ inc_miss_counter(cache, bio);
+ remap_to_origin_clear_discard(cache, bio, block);
+
+ cell_defer(cache, cell, false);
+ }
+
+ } else {
+ inc_hit_counter(cache, bio);
+ pb->all_io_entry = dm_deferred_entry_inc(cache->all_io_ds);
+
+ if (bio_data_dir(bio) == WRITE && writethrough_mode(&cache->features) &&
+ !is_dirty(cache, 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);
+ r = DM_MAPIO_SUBMITTED;
+ }
+
+ return r;
+}
+
+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->sectors_per_block,
+ cache->origin_blocks);
+ if (r) {
+ DMERR("could not resize on-disk discard bitset");
+ return r;
+ }
+
+ for (i = 0; i < from_oblock(cache->discard_nr_blocks); i++) {
+ r = dm_cache_set_discard(cache->cmd, to_oblock(i),
+ is_discarded(cache, to_oblock(i)));
+ if (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("could not write dirty bitset");
+
+ r2 = write_discard_bitset(cache);
+ if (r2)
+ DMERR("could not write discard bitset");
+
+ save_stats(cache);
+
+ r3 = dm_cache_write_hints(cache->cmd, cache->policy);
+ 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_oblock_t oblock, bool discard)
+{
+ struct cache *cache = context;
+
+ if (discard)
+ set_discard(cache, oblock);
+ else
+ clear_discard(cache, oblock);
+
+ 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))
+ return true;
+
+ /*
+ * 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("unable to shrink cache; cache block %llu is dirty",
+ (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("could not resize cache metadata");
+ return r;
+ }
+
+ cache->cache_size = 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("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:
+ *
+ * <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>*
+ */
+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("%u %llu/%llu %u %llu/%llu %u %u %u %u %u %u %lu ",
+ (unsigned)(DM_CACHE_METADATA_BLOCK_SIZE >> SECTOR_SHIFT),
+ (unsigned long long)(nr_blocks_metadata - nr_free_blocks_metadata),
+ (unsigned long long)nr_blocks_metadata,
+ 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));
+
+ if (writethrough_mode(&cache->features))
+ DMEMIT("1 writethrough ");
+
+ else if (passthrough_mode(&cache->features))
+ DMEMIT("1 passthrough ");
+
+ else if (writeback_mode(&cache->features))
+ DMEMIT("1 writeback ");
+
+ else {
+ DMERR("internal error: unknown io mode: %d", (int) cache->features.io_mode);
+ goto err;
+ }
+
+ 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 + 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");
+}
+
+/*
+ * A cache block range can take two forms:
+ *
+ * i) A single cblock, eg. '3456'
+ * ii) A begin and end cblock with dots 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("invalid cblock range '%s'", 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("begin cblock out of range: %llu >= %llu", b, n);
+ return -EINVAL;
+ }
+
+ if (e > n) {
+ DMERR("end cblock out of range: %llu > %llu", e, n);
+ return -EINVAL;
+ }
+
+ if (b >= e) {
+ DMERR("invalid cblock range: %llu >= %llu", b, e);
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
+static int request_invalidation(struct cache *cache, struct cblock_range *range)
+{
+ struct invalidation_request req;
+
+ INIT_LIST_HEAD(&req.list);
+ req.cblocks = range;
+ atomic_set(&req.complete, 0);
+ req.err = 0;
+ init_waitqueue_head(&req.result_wait);
+
+ spin_lock(&cache->invalidation_lock);
+ list_add(&req.list, &cache->invalidation_requests);
+ spin_unlock(&cache->invalidation_lock);
+ wake_worker(cache);
+
+ wait_event(req.result_wait, atomic_read(&req.complete));
+ return req.err;
+}
+
+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->features)) {
+ DMERR("cache has to be in passthrough mode for invalidation");
+ 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)
+{
+ struct cache *cache = ti->private;
+
+ if (!argc)
+ return -EINVAL;
+
+ 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;
+}
+
+/*
+ * 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->sectors_per_block;
+ limits->discard_granularity = cache->sectors_per_block << SECTOR_SHIFT;
+}
+
+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, 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, 4, 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,
+ .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");
generated by cgit v1.2.3-70-g09d2 (git 2.46.0) at 2025-11-04 08:11:14 +0000