diff options
Diffstat (limited to 'drivers/md/dm-clone-target.c')
| -rw-r--r-- | drivers/md/dm-clone-target.c | 2191 |
1 files changed, 2191 insertions, 0 deletions
diff --git a/drivers/md/dm-clone-target.c b/drivers/md/dm-clone-target.c new file mode 100644 index 000000000000..cd6f9e9fc98e --- /dev/null +++ b/drivers/md/dm-clone-target.c @@ -0,0 +1,2191 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright (C) 2019 Arrikto, Inc. All Rights Reserved. + */ + +#include <linux/mm.h> +#include <linux/bio.h> +#include <linux/err.h> +#include <linux/hash.h> +#include <linux/list.h> +#include <linux/log2.h> +#include <linux/init.h> +#include <linux/slab.h> +#include <linux/wait.h> +#include <linux/dm-io.h> +#include <linux/mutex.h> +#include <linux/atomic.h> +#include <linux/bitops.h> +#include <linux/blkdev.h> +#include <linux/kdev_t.h> +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/jiffies.h> +#include <linux/mempool.h> +#include <linux/spinlock.h> +#include <linux/blk_types.h> +#include <linux/dm-kcopyd.h> +#include <linux/workqueue.h> +#include <linux/backing-dev.h> +#include <linux/device-mapper.h> + +#include "dm.h" +#include "dm-clone-metadata.h" + +#define DM_MSG_PREFIX "clone" + +/* + * Minimum and maximum allowed region sizes + */ +#define MIN_REGION_SIZE (1 << 3) /* 4KB */ +#define MAX_REGION_SIZE (1 << 21) /* 1GB */ + +#define MIN_HYDRATIONS 256 /* Size of hydration mempool */ +#define DEFAULT_HYDRATION_THRESHOLD 1 /* 1 region */ +#define DEFAULT_HYDRATION_BATCH_SIZE 1 /* Hydrate in batches of 1 region */ + +#define COMMIT_PERIOD HZ /* 1 sec */ + +/* + * Hydration hash table size: 1 << HASH_TABLE_BITS + */ +#define HASH_TABLE_BITS 15 + +DECLARE_DM_KCOPYD_THROTTLE_WITH_MODULE_PARM(clone_hydration_throttle, + "A percentage of time allocated for hydrating regions"); + +/* Slab cache for struct dm_clone_region_hydration */ +static struct kmem_cache *_hydration_cache; + +/* dm-clone metadata modes */ +enum clone_metadata_mode { + CM_WRITE, /* metadata may be changed */ + CM_READ_ONLY, /* metadata may not be changed */ + CM_FAIL, /* all metadata I/O fails */ +}; + +struct hash_table_bucket; + +struct clone { + struct dm_target *ti; + struct dm_target_callbacks callbacks; + + struct dm_dev *metadata_dev; + struct dm_dev *dest_dev; + struct dm_dev *source_dev; + + unsigned long nr_regions; + sector_t region_size; + unsigned int region_shift; + + /* + * A metadata commit and the actions taken in case it fails should run + * as a single atomic step. + */ + struct mutex commit_lock; + + struct dm_clone_metadata *cmd; + + /* Region hydration hash table */ + struct hash_table_bucket *ht; + + atomic_t ios_in_flight; + + wait_queue_head_t hydration_stopped; + + mempool_t hydration_pool; + + unsigned long last_commit_jiffies; + + /* + * We defer incoming WRITE bios for regions that are not hydrated, + * until after these regions have been hydrated. + * + * Also, we defer REQ_FUA and REQ_PREFLUSH bios, until after the + * metadata have been committed. + */ + spinlock_t lock; + struct bio_list deferred_bios; + struct bio_list deferred_discard_bios; + struct bio_list deferred_flush_bios; + struct bio_list deferred_flush_completions; + + /* Maximum number of regions being copied during background hydration. */ + unsigned int hydration_threshold; + + /* Number of regions to batch together during background hydration. */ + unsigned int hydration_batch_size; + + /* Which region to hydrate next */ + unsigned long hydration_offset; + + atomic_t hydrations_in_flight; + + /* + * Save a copy of the table line rather than reconstructing it for the + * status. + */ + unsigned int nr_ctr_args; + const char **ctr_args; + + struct workqueue_struct *wq; + struct work_struct worker; + struct delayed_work waker; + + struct dm_kcopyd_client *kcopyd_client; + + enum clone_metadata_mode mode; + unsigned long flags; +}; + +/* + * dm-clone flags + */ +#define DM_CLONE_DISCARD_PASSDOWN 0 +#define DM_CLONE_HYDRATION_ENABLED 1 +#define DM_CLONE_HYDRATION_SUSPENDED 2 + +/*---------------------------------------------------------------------------*/ + +/* + * Metadata failure handling. + */ +static enum clone_metadata_mode get_clone_mode(struct clone *clone) +{ + return READ_ONCE(clone->mode); +} + +static const char *clone_device_name(struct clone *clone) +{ + return dm_table_device_name(clone->ti->table); +} + +static void __set_clone_mode(struct clone *clone, enum clone_metadata_mode new_mode) +{ + const char *descs[] = { + "read-write", + "read-only", + "fail" + }; + + enum clone_metadata_mode old_mode = get_clone_mode(clone); + + /* 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_clone_metadata_set_read_only(clone->cmd); + break; + + case CM_WRITE: + dm_clone_metadata_set_read_write(clone->cmd); + break; + } + + WRITE_ONCE(clone->mode, new_mode); + + if (new_mode != old_mode) { + dm_table_event(clone->ti->table); + DMINFO("%s: Switching to %s mode", clone_device_name(clone), + descs[(int)new_mode]); + } +} + +static void __abort_transaction(struct clone *clone) +{ + const char *dev_name = clone_device_name(clone); + + if (get_clone_mode(clone) >= CM_READ_ONLY) + return; + + DMERR("%s: Aborting current metadata transaction", dev_name); + if (dm_clone_metadata_abort(clone->cmd)) { + DMERR("%s: Failed to abort metadata transaction", dev_name); + __set_clone_mode(clone, CM_FAIL); + } +} + +static void __reload_in_core_bitset(struct clone *clone) +{ + const char *dev_name = clone_device_name(clone); + + if (get_clone_mode(clone) == CM_FAIL) + return; + + /* Reload the on-disk bitset */ + DMINFO("%s: Reloading on-disk bitmap", dev_name); + if (dm_clone_reload_in_core_bitset(clone->cmd)) { + DMERR("%s: Failed to reload on-disk bitmap", dev_name); + __set_clone_mode(clone, CM_FAIL); + } +} + +static void __metadata_operation_failed(struct clone *clone, const char *op, int r) +{ + DMERR("%s: Metadata operation `%s' failed: error = %d", + clone_device_name(clone), op, r); + + __abort_transaction(clone); + __set_clone_mode(clone, CM_READ_ONLY); + + /* + * dm_clone_reload_in_core_bitset() may run concurrently with either + * dm_clone_set_region_hydrated() or dm_clone_cond_set_range(), but + * it's safe as we have already set the metadata to read-only mode. + */ + __reload_in_core_bitset(clone); +} + +/*---------------------------------------------------------------------------*/ + +/* Wake up anyone waiting for region hydrations to stop */ +static inline void wakeup_hydration_waiters(struct clone *clone) +{ + wake_up_all(&clone->hydration_stopped); +} + +static inline void wake_worker(struct clone *clone) +{ + queue_work(clone->wq, &clone->worker); +} + +/*---------------------------------------------------------------------------*/ + +/* + * bio helper functions. + */ +static inline void remap_to_source(struct clone *clone, struct bio *bio) +{ + bio_set_dev(bio, clone->source_dev->bdev); +} + +static inline void remap_to_dest(struct clone *clone, struct bio *bio) +{ + bio_set_dev(bio, clone->dest_dev->bdev); +} + +static bool bio_triggers_commit(struct clone *clone, struct bio *bio) +{ + return op_is_flush(bio->bi_opf) && + dm_clone_changed_this_transaction(clone->cmd); +} + +/* Get the address of the region in sectors */ +static inline sector_t region_to_sector(struct clone *clone, unsigned long region_nr) +{ + return (region_nr << clone->region_shift); +} + +/* Get the region number of the bio */ +static inline unsigned long bio_to_region(struct clone *clone, struct bio *bio) +{ + return (bio->bi_iter.bi_sector >> clone->region_shift); +} + +/* Get the region range covered by the bio */ +static void bio_region_range(struct clone *clone, struct bio *bio, + unsigned long *rs, unsigned long *re) +{ + *rs = dm_sector_div_up(bio->bi_iter.bi_sector, clone->region_size); + *re = bio_end_sector(bio) >> clone->region_shift; +} + +/* Check whether a bio overwrites a region */ +static inline bool is_overwrite_bio(struct clone *clone, struct bio *bio) +{ + return (bio_data_dir(bio) == WRITE && bio_sectors(bio) == clone->region_size); +} + +static void fail_bios(struct bio_list *bios, blk_status_t status) +{ + struct bio *bio; + + while ((bio = bio_list_pop(bios))) { + bio->bi_status = status; + bio_endio(bio); + } +} + +static void submit_bios(struct bio_list *bios) +{ + struct bio *bio; + struct blk_plug plug; + + blk_start_plug(&plug); + + while ((bio = bio_list_pop(bios))) + generic_make_request(bio); + + blk_finish_plug(&plug); +} + +/* + * Submit bio to the underlying device. + * + * If the bio triggers a commit, delay it, until after the metadata have been + * committed. + * + * NOTE: The bio remapping must be performed by the caller. + */ +static void issue_bio(struct clone *clone, struct bio *bio) +{ + unsigned long flags; + + if (!bio_triggers_commit(clone, bio)) { + generic_make_request(bio); + return; + } + + /* + * If the metadata mode is RO or FAIL we won't be able to commit the + * metadata, so we complete the bio with an error. + */ + if (unlikely(get_clone_mode(clone) >= CM_READ_ONLY)) { + bio_io_error(bio); + return; + } + + /* + * Batch together any bios that trigger commits and then issue a single + * commit for them in process_deferred_flush_bios(). + */ + spin_lock_irqsave(&clone->lock, flags); + bio_list_add(&clone->deferred_flush_bios, bio); + spin_unlock_irqrestore(&clone->lock, flags); + + wake_worker(clone); +} + +/* + * Remap bio to the destination device and submit it. + * + * If the bio triggers a commit, delay it, until after the metadata have been + * committed. + */ +static void remap_and_issue(struct clone *clone, struct bio *bio) +{ + remap_to_dest(clone, bio); + issue_bio(clone, bio); +} + +/* + * Issue bios that have been deferred until after their region has finished + * hydrating. + * + * We delegate the bio submission to the worker thread, so this is safe to call + * from interrupt context. + */ +static void issue_deferred_bios(struct clone *clone, struct bio_list *bios) +{ + struct bio *bio; + unsigned long flags; + struct bio_list flush_bios = BIO_EMPTY_LIST; + struct bio_list normal_bios = BIO_EMPTY_LIST; + + if (bio_list_empty(bios)) + return; + + while ((bio = bio_list_pop(bios))) { + if (bio_triggers_commit(clone, bio)) + bio_list_add(&flush_bios, bio); + else + bio_list_add(&normal_bios, bio); + } + + spin_lock_irqsave(&clone->lock, flags); + bio_list_merge(&clone->deferred_bios, &normal_bios); + bio_list_merge(&clone->deferred_flush_bios, &flush_bios); + spin_unlock_irqrestore(&clone->lock, flags); + + wake_worker(clone); +} + +static void complete_overwrite_bio(struct clone *clone, struct bio *bio) +{ + unsigned long flags; + + /* + * If the bio has the REQ_FUA flag set we must commit the metadata + * before signaling its completion. + * + * complete_overwrite_bio() is only called by hydration_complete(), + * after having successfully updated the metadata. This means we don't + * need to call dm_clone_changed_this_transaction() to check if the + * metadata has changed and thus we can avoid taking the metadata spin + * lock. + */ + if (!(bio->bi_opf & REQ_FUA)) { + bio_endio(bio); + return; + } + + /* + * If the metadata mode is RO or FAIL we won't be able to commit the + * metadata, so we complete the bio with an error. + */ + if (unlikely(get_clone_mode(clone) >= CM_READ_ONLY)) { + bio_io_error(bio); + return; + } + + /* + * Batch together any bios that trigger commits and then issue a single + * commit for them in process_deferred_flush_bios(). + */ + spin_lock_irqsave(&clone->lock, flags); + bio_list_add(&clone->deferred_flush_completions, bio); + spin_unlock_irqrestore(&clone->lock, flags); + + wake_worker(clone); +} + +static void trim_bio(struct bio *bio, sector_t sector, unsigned int len) +{ + bio->bi_iter.bi_sector = sector; + bio->bi_iter.bi_size = to_bytes(len); +} + +static void complete_discard_bio(struct clone *clone, struct bio *bio, bool success) +{ + unsigned long rs, re; + + /* + * If the destination device supports discards, remap and trim the + * discard bio and pass it down. Otherwise complete the bio + * immediately. + */ + if (test_bit(DM_CLONE_DISCARD_PASSDOWN, &clone->flags) && success) { + remap_to_dest(clone, bio); + bio_region_range(clone, bio, &rs, &re); + trim_bio(bio, rs << clone->region_shift, + (re - rs) << clone->region_shift); + generic_make_request(bio); + } else + bio_endio(bio); +} + +static void process_discard_bio(struct clone *clone, struct bio *bio) +{ + unsigned long rs, re, flags; + + bio_region_range(clone, bio, &rs, &re); + BUG_ON(re > clone->nr_regions); + + if (unlikely(rs == re)) { + bio_endio(bio); + return; + } + + /* + * The covered regions are already hydrated so we just need to pass + * down the discard. + */ + if (dm_clone_is_range_hydrated(clone->cmd, rs, re - rs)) { + complete_discard_bio(clone, bio, true); + return; + } + + /* + * If the metadata mode is RO or FAIL we won't be able to update the + * metadata for the regions covered by the discard so we just ignore + * it. + */ + if (unlikely(get_clone_mode(clone) >= CM_READ_ONLY)) { + bio_endio(bio); + return; + } + + /* + * Defer discard processing. + */ + spin_lock_irqsave(&clone->lock, flags); + bio_list_add(&clone->deferred_discard_bios, bio); + spin_unlock_irqrestore(&clone->lock, flags); + + wake_worker(clone); +} + +/*---------------------------------------------------------------------------*/ + +/* + * dm-clone region hydrations. + */ +struct dm_clone_region_hydration { + struct clone *clone; + unsigned long region_nr; + + struct bio *overwrite_bio; + bio_end_io_t *overwrite_bio_end_io; + + struct bio_list deferred_bios; + + blk_status_t status; + + /* Used by hydration batching */ + struct list_head list; + + /* Used by hydration hash table */ + struct hlist_node h; +}; + +/* + * Hydration hash table implementation. + * + * Ideally we would like to use list_bl, which uses bit spin locks and employs + * the least significant bit of the list head to lock the corresponding bucket, + * reducing the memory overhead for the locks. But, currently, list_bl and bit + * spin locks don't support IRQ safe versions. Since we have to take the lock + * in both process and interrupt context, we must fall back to using regular + * spin locks; one per hash table bucket. + */ +struct hash_table_bucket { + struct hlist_head head; + + /* Spinlock protecting the bucket */ + spinlock_t lock; +}; + +#define bucket_lock_irqsave(bucket, flags) \ + spin_lock_irqsave(&(bucket)->lock, flags) + +#define bucket_unlock_irqrestore(bucket, flags) \ + spin_unlock_irqrestore(&(bucket)->lock, flags) + +static int hash_table_init(struct clone *clone) +{ + unsigned int i, sz; + struct hash_table_bucket *bucket; + + sz = 1 << HASH_TABLE_BITS; + + clone->ht = kvmalloc(sz * sizeof(struct hash_table_bucket), GFP_KERNEL); + if (!clone->ht) + return -ENOMEM; + + for (i = 0; i < sz; i++) { + bucket = clone->ht + i; + + INIT_HLIST_HEAD(&bucket->head); + spin_lock_init(&bucket->lock); + } + + return 0; +} + +static void hash_table_exit(struct clone *clone) +{ + kvfree(clone->ht); +} + +static struct hash_table_bucket *get_hash_table_bucket(struct clone *clone, + unsigned long region_nr) +{ + return &clone->ht[hash_long(region_nr, HASH_TABLE_BITS)]; +} + +/* + * Search hash table for a hydration with hd->region_nr == region_nr + * + * NOTE: Must be called with the bucket lock held + */ +struct dm_clone_region_hydration *__hash_find(struct hash_table_bucket *bucket, + unsigned long region_nr) +{ + struct dm_clone_region_hydration *hd; + + hlist_for_each_entry(hd, &bucket->head, h) { + if (hd->region_nr == region_nr) + return hd; + } + + return NULL; +} + +/* + * Insert a hydration into the hash table. + * + * NOTE: Must be called with the bucket lock held. + */ +static inline void __insert_region_hydration(struct hash_table_bucket *bucket, + struct dm_clone_region_hydration *hd) +{ + hlist_add_head(&hd->h, &bucket->head); +} + +/* + * This function inserts a hydration into the hash table, unless someone else + * managed to insert a hydration for the same region first. In the latter case + * it returns the existing hydration descriptor for this region. + * + * NOTE: Must be called with the hydration hash table lock held. + */ +static struct dm_clone_region_hydration * +__find_or_insert_region_hydration(struct hash_table_bucket *bucket, + struct dm_clone_region_hydration *hd) +{ + struct dm_clone_region_hydration *hd2; + + hd2 = __hash_find(bucket, hd->region_nr); + if (hd2) + return hd2; + + __insert_region_hydration(bucket, hd); + + return hd; +} + +/*---------------------------------------------------------------------------*/ + +/* Allocate a hydration */ +static struct dm_clone_region_hydration *alloc_hydration(struct clone *clone) +{ + struct dm_clone_region_hydration *hd; + + /* + * Allocate a hydration from the hydration mempool. + * This might block but it can't fail. + */ + hd = mempool_alloc(&clone->hydration_pool, GFP_NOIO); + hd->clone = clone; + + return hd; +} + +static inline void free_hydration(struct dm_clone_region_hydration *hd) +{ + mempool_free(hd, &hd->clone->hydration_pool); +} + +/* Initialize a hydration */ +static void hydration_init(struct dm_clone_region_hydration *hd, unsigned long region_nr) +{ + hd->region_nr = region_nr; + hd->overwrite_bio = NULL; + bio_list_init(&hd->deferred_bios); + hd->status = 0; + + INIT_LIST_HEAD(&hd->list); + INIT_HLIST_NODE(&hd->h); +} + +/*---------------------------------------------------------------------------*/ + +/* + * Update dm-clone's metadata after a region has finished hydrating and remove + * hydration from the hash table. + */ +static int hydration_update_metadata(struct dm_clone_region_hydration *hd) +{ + int r = 0; + unsigned long flags; + struct hash_table_bucket *bucket; + struct clone *clone = hd->clone; + + if (unlikely(get_clone_mode(clone) >= CM_READ_ONLY)) + r = -EPERM; + + /* Update the metadata */ + if (likely(!r) && hd->status == BLK_STS_OK) + r = dm_clone_set_region_hydrated(clone->cmd, hd->region_nr); + + bucket = get_hash_table_bucket(clone, hd->region_nr); + + /* Remove hydration from hash table */ + bucket_lock_irqsave(bucket, flags); + hlist_del(&hd->h); + bucket_unlock_irqrestore(bucket, flags); + + return r; +} + +/* + * Complete a region's hydration: + * + * 1. Update dm-clone's metadata. + * 2. Remove hydration from hash table. + * 3. Complete overwrite bio. + * 4. Issue deferred bios. + * 5. If this was the last hydration, wake up anyone waiting for + * hydrations to finish. + */ +static void hydration_complete(struct dm_clone_region_hydration *hd) +{ + int r; + blk_status_t status; + struct clone *clone = hd->clone; + + r = hydration_update_metadata(hd); + + if (hd->status == BLK_STS_OK && likely(!r)) { + if (hd->overwrite_bio) + complete_overwrite_bio(clone, hd->overwrite_bio); + + issue_deferred_bios(clone, &hd->deferred_bios); + } else { + status = r ? BLK_STS_IOERR : hd->status; + + if (hd->overwrite_bio) + bio_list_add(&hd->deferred_bios, hd->overwrite_bio); + + fail_bios(&hd->deferred_bios, status); + } + + free_hydration(hd); + + if (atomic_dec_and_test(&clone->hydrations_in_flight)) + wakeup_hydration_waiters(clone); +} + +static void hydration_kcopyd_callback(int read_err, unsigned long write_err, void *context) +{ + blk_status_t status; + + struct dm_clone_region_hydration *tmp, *hd = context; + struct clone *clone = hd->clone; + + LIST_HEAD(batched_hydrations); + + if (read_err || write_err) { + DMERR_LIMIT("%s: hydration failed", clone_device_name(clone)); + status = BLK_STS_IOERR; + } else { + status = BLK_STS_OK; + } + list_splice_tail(&hd->list, &batched_hydrations); + + hd->status = status; + hydration_complete(hd); + + /* Complete batched hydrations */ + list_for_each_entry_safe(hd, tmp, &batched_hydrations, list) { + hd->status = status; + hydration_complete(hd); + } + + /* Continue background hydration, if there is no I/O in-flight */ + if (test_bit(DM_CLONE_HYDRATION_ENABLED, &clone->flags) && + !atomic_read(&clone->ios_in_flight)) + wake_worker(clone); +} + +static void hydration_copy(struct dm_clone_region_hydration *hd, unsigned int nr_regions) +{ + unsigned long region_start, region_end; + sector_t tail_size, region_size, total_size; + struct dm_io_region from, to; + struct clone *clone = hd->clone; + + region_size = clone->region_size; + region_start = hd->region_nr; + region_end = region_start + nr_regions - 1; + + total_size = (nr_regions - 1) << clone->region_shift; + + if (region_end == clone->nr_regions - 1) { + /* + * The last region of the target might be smaller than + * region_size. + */ + tail_size = clone->ti->len & (region_size - 1); + if (!tail_size) + tail_size = region_size; + } else { + tail_size = region_size; + } + + total_size += tail_size; + + from.bdev = clone->source_dev->bdev; + from.sector = region_to_sector(clone, region_start); + from.count = total_size; + + to.bdev = clone->dest_dev->bdev; + to.sector = from.sector; + to.count = from.count; + + /* Issue copy */ + atomic_add(nr_regions, &clone->hydrations_in_flight); + dm_kcopyd_copy(clone->kcopyd_client, &from, 1, &to, 0, + hydration_kcopyd_callback, hd); +} + +static void overwrite_endio(struct bio *bio) +{ + struct dm_clone_region_hydration *hd = bio->bi_private; + + bio->bi_end_io = hd->overwrite_bio_end_io; + hd->status = bio->bi_status; + + hydration_complete(hd); +} + +static void hydration_overwrite(struct dm_clone_region_hydration *hd, struct bio *bio) +{ + /* + * We don't need to save and restore bio->bi_private because device + * mapper core generates a new bio for us to use, with clean + * bi_private. + */ + hd->overwrite_bio = bio; + hd->overwrite_bio_end_io = bio->bi_end_io; + + bio->bi_end_io = overwrite_endio; + bio->bi_private = hd; + + atomic_inc(&hd->clone->hydrations_in_flight); + generic_make_request(bio); +} + +/* + * Hydrate bio's region. + * + * This function starts the hydration of the bio's region and puts the bio in + * the list of deferred bios for this region. In case, by the time this + * function is called, the region has finished hydrating it's submitted to the + * destination device. + * + * NOTE: The bio remapping must be performed by the caller. + */ +static void hydrate_bio_region(struct clone *clone, struct bio *bio) +{ + unsigned long flags; + unsigned long region_nr; + struct hash_table_bucket *bucket; + struct dm_clone_region_hydration *hd, *hd2; + + region_nr = bio_to_region(clone, bio); + bucket = get_hash_table_bucket(clone, region_nr); + + bucket_lock_irqsave(bucket, flags); + + hd = __hash_find(bucket, region_nr); + if (hd) { + /* Someone else is hydrating the region */ + bio_list_add(&hd->deferred_bios, bio); + bucket_unlock_irqrestore(bucket, flags); + return; + } + + if (dm_clone_is_region_hydrated(clone->cmd, region_nr)) { + /* The region has been hydrated */ + bucket_unlock_irqrestore(bucket, flags); + issue_bio(clone, bio); + return; + } + + /* + * We must allocate a hydration descriptor and start the hydration of + * the corresponding region. + */ + bucket_unlock_irqrestore(bucket, flags); + + hd = alloc_hydration(clone); + hydration_init(hd, region_nr); + + bucket_lock_irqsave(bucket, flags); + + /* Check if the region has been hydrated in the meantime. */ + if (dm_clone_is_region_hydrated(clone->cmd, region_nr)) { + bucket_unlock_irqrestore(bucket, flags); + free_hydration(hd); + issue_bio(clone, bio); + return; + } + + hd2 = __find_or_insert_region_hydration(bucket, hd); + if (hd2 != hd) { + /* Someone else started the region's hydration. */ + bio_list_add(&hd2->deferred_bios, bio); + bucket_unlock_irqrestore(bucket, flags); + free_hydration(hd); + return; + } + + /* + * If the metadata mode is RO or FAIL then there is no point starting a + * hydration, since we will not be able to update the metadata when the + * hydration finishes. + */ + if (unlikely(get_clone_mode(clone) >= CM_READ_ONLY)) { + hlist_del(&hd->h); + bucket_unlock_irqrestore(bucket, flags); + free_hydration(hd); + bio_io_error(bio); + return; + } + + /* + * Start region hydration. + * + * If a bio overwrites a region, i.e., its size is equal to the + * region's size, then we don't need to copy the region from the source + * to the destination device. + */ + if (is_overwrite_bio(clone, bio)) { + bucket_unlock_irqrestore(bucket, flags); + hydration_overwrite(hd, bio); + } else { + bio_list_add(&hd->deferred_bios, bio); + bucket_unlock_irqrestore(bucket, flags); + hydration_copy(hd, 1); + } +} + +/*---------------------------------------------------------------------------*/ + +/* + * Background hydrations. + */ + +/* + * Batch region hydrations. + * + * To better utilize device bandwidth we batch together the hydration of + * adjacent regions. This allows us to use small region sizes, e.g., 4KB, which + * is good for small, random write performance (because of the overwriting of + * un-hydrated regions) and at the same time issue big copy requests to kcopyd + * to achieve high hydration bandwidth. + */ +struct batch_info { + struct dm_clone_region_hydration *head; + unsigned int nr_batched_regions; +}; + +static void __batch_hydration(struct batch_info *batch, + struct dm_clone_region_hydration *hd) +{ + struct clone *clone = hd->clone; + unsigned int max_batch_size = READ_ONCE(clone->hydration_batch_size); + + if (batch->head) { + /* Try to extend the current batch */ + if (batch->nr_batched_regions < max_batch_size && + (batch->head->region_nr + batch->nr_batched_regions) == hd->region_nr) { + list_add_tail(&hd->list, &batch->head->list); + batch->nr_batched_regions++; + hd = NULL; + } + + /* Check if we should issue the current batch */ + if (batch->nr_batched_regions >= max_batch_size || hd) { + hydration_copy(batch->head, batch->nr_batched_regions); + batch->head = NULL; + batch->nr_batched_regions = 0; + } + } + + if (!hd) + return; + + /* We treat max batch sizes of zero and one equivalently */ + if (max_batch_size <= 1) { + hydration_copy(hd, 1); + return; + } + + /* Start a new batch */ + BUG_ON(!list_empty(&hd->list)); + batch->head = hd; + batch->nr_batched_regions = 1; +} + +static unsigned long __start_next_hydration(struct clone *clone, + unsigned long offset, + struct batch_info *batch) +{ + unsigned long flags; + struct hash_table_bucket *bucket; + struct dm_clone_region_hydration *hd; + unsigned long nr_regions = clone->nr_regions; + + hd = alloc_hydration(clone); + + /* Try to find a region to hydrate. */ + do { + offset = dm_clone_find_next_unhydrated_region(clone->cmd, offset); + if (offset == nr_regions) + break; + + bucket = get_hash_table_bucket(clone, offset); + bucket_lock_irqsave(bucket, flags); + + if (!dm_clone_is_region_hydrated(clone->cmd, offset) && + !__hash_find(bucket, offset)) { + hydration_init(hd, offset); + __insert_region_hydration(bucket, hd); + bucket_unlock_irqrestore(bucket, flags); + + /* Batch hydration */ + __batch_hydration(batch, hd); + + return (offset + 1); + } + + bucket_unlock_irqrestore(bucket, flags); + + } while (++offset < nr_regions); + + if (hd) + free_hydration(hd); + + return offset; +} + +/* + * This function searches for regions that still reside in the source device + * and starts their hydration. + */ +static void do_hydration(struct clone *clone) +{ + unsigned int current_volume; + unsigned long offset, nr_regions = clone->nr_regions; + + struct batch_info batch = { + .head = NULL, + .nr_batched_regions = 0, + }; + + if (unlikely(get_clone_mode(clone) >= CM_READ_ONLY)) + return; + + if (dm_clone_is_hydration_done(clone->cmd)) + return; + + /* + * Avoid race with device suspension. + */ + atomic_inc(&clone->hydrations_in_flight); + + /* + * Make sure atomic_inc() is ordered before test_bit(), otherwise we + * might race with clone_postsuspend() and start a region hydration + * after the target has been suspended. + * + * This is paired with the smp_mb__after_atomic() in + * clone_postsuspend(). + */ + smp_mb__after_atomic(); + + offset = clone->hydration_offset; + while (likely(!test_bit(DM_CLONE_HYDRATION_SUSPENDED, &clone->flags)) && + !atomic_read(&clone->ios_in_flight) && + test_bit(DM_CLONE_HYDRATION_ENABLED, &clone->flags) && + offset < nr_regions) { + current_volume = atomic_read(&clone->hydrations_in_flight); + current_volume += batch.nr_batched_regions; + + if (current_volume > READ_ONCE(clone->hydration_threshold)) + break; + + offset = __start_next_hydration(clone, offset, &batch); + } + + if (batch.head) + hydration_copy(batch.head, batch.nr_batched_regions); + + if (offset >= nr_regions) + offset = 0; + + clone->hydration_offset = offset; + + if (atomic_dec_and_test(&clone->hydrations_in_flight)) + wakeup_hydration_waiters(clone); +} + +/*---------------------------------------------------------------------------*/ + +static bool need_commit_due_to_time(struct clone *clone) +{ + return !time_in_range(jiffies, clone->last_commit_jiffies, + clone->last_commit_jiffies + COMMIT_PERIOD); +} + +/* + * A non-zero return indicates read-only or fail mode. + */ +static int commit_metadata(struct clone *clone) +{ + int r = 0; + + mutex_lock(&clone->commit_lock); + + if (!dm_clone_changed_this_transaction(clone->cmd)) + goto out; + + if (unlikely(get_clone_mode(clone) >= CM_READ_ONLY)) { + r = -EPERM; + goto out; + } + + r = dm_clone_metadata_commit(clone->cmd); + + if (unlikely(r)) { + __metadata_operation_failed(clone, "dm_clone_metadata_commit", r); + goto out; + } + + if (dm_clone_is_hydration_done(clone->cmd)) + dm_table_event(clone->ti->table); +out: + mutex_unlock(&clone->commit_lock); + + return r; +} + +static void process_deferred_discards(struct clone *clone) +{ + int r = -EPERM; + struct bio *bio; + struct blk_plug plug; + unsigned long rs, re, flags; + struct bio_list discards = BIO_EMPTY_LIST; + + spin_lock_irqsave(&clone->lock, flags); + bio_list_merge(&discards, &clone->deferred_discard_bios); + bio_list_init(&clone->deferred_discard_bios); + spin_unlock_irqrestore(&clone->lock, flags); + + if (bio_list_empty(&discards)) + return; + + if (unlikely(get_clone_mode(clone) >= CM_READ_ONLY)) + goto out; + + /* Update the metadata */ + bio_list_for_each(bio, &discards) { + bio_region_range(clone, bio, &rs, &re); + /* + * A discard request might cover regions that have been already + * hydrated. There is no need to update the metadata for these + * regions. + */ + r = dm_clone_cond_set_range(clone->cmd, rs, re - rs); + + if (unlikely(r)) + break; + } +out: + blk_start_plug(&plug); + while ((bio = bio_list_pop(&discards))) + complete_discard_bio(clone, bio, r == 0); + blk_finish_plug(&plug); +} + +static void process_deferred_bios(struct clone *clone) +{ + unsigned long flags; + struct bio_list bios = BIO_EMPTY_LIST; + + spin_lock_irqsave(&clone->lock, flags); + bio_list_merge(&bios, &clone->deferred_bios); + bio_list_init(&clone->deferred_bios); + spin_unlock_irqrestore(&clone->lock, flags); + + if (bio_list_empty(&bios)) + return; + + submit_bios(&bios); +} + +static void process_deferred_flush_bios(struct clone *clone) +{ + struct bio *bio; + unsigned long flags; + struct bio_list bios = BIO_EMPTY_LIST; + struct bio_list bio_completions = BIO_EMPTY_LIST; + + /* + * If there are any deferred flush bios, we must commit the metadata + * before issuing them or signaling their completion. + */ + spin_lock_irqsave(&clone->lock, flags); + bio_list_merge(&bios, &clone->deferred_flush_bios); + bio_list_init(&clone->deferred_flush_bios); + + bio_list_merge(&bio_completions, &clone->deferred_flush_completions); + bio_list_init(&clone->deferred_flush_completions); + spin_unlock_irqrestore(&clone->lock, flags); + + if (bio_list_empty(&bios) && bio_list_empty(&bio_completions) && + !(dm_clone_changed_this_transaction(clone->cmd) && need_commit_due_to_time(clone))) + return; + + if (commit_metadata(clone)) { + bio_list_merge(&bios, &bio_completions); + + while ((bio = bio_list_pop(&bios))) + bio_io_error(bio); + + return; + } + + clone->last_commit_jiffies = jiffies; + + while ((bio = bio_list_pop(&bio_completions))) + bio_endio(bio); + + while ((bio = bio_list_pop(&bios))) + generic_make_request(bio); +} + +static void do_worker(struct work_struct *work) +{ + struct clone *clone = container_of(work, typeof(*clone), worker); + + process_deferred_bios(clone); + process_deferred_discards(clone); + + /* + * process_deferred_flush_bios(): + * + * - Commit metadata + * + * - Process deferred REQ_FUA completions + * + * - Process deferred REQ_PREFLUSH bios + */ + process_deferred_flush_bios(clone); + + /* Background hydration */ + do_hydration(clone); +} + +/* + * Commit periodically so that not too much unwritten data builds up. + * + * Also, restart background hydration, if it has been stopped by in-flight I/O. + */ +static void do_waker(struct work_struct *work) +{ + struct clone *clone = container_of(to_delayed_work(work), struct clone, waker); + + wake_worker(clone); + queue_delayed_work(clone->wq, &clone->waker, COMMIT_PERIOD); +} + +/*---------------------------------------------------------------------------*/ + +/* + * Target methods + */ +static int clone_map(struct dm_target *ti, struct bio *bio) +{ + struct clone *clone = ti->private; + unsigned long region_nr; + + atomic_inc(&clone->ios_in_flight); + + if (unlikely(get_clone_mode(clone) == CM_FAIL)) + return DM_MAPIO_KILL; + + /* + * REQ_PREFLUSH bios carry no data: + * + * - Commit metadata, if changed + * + * - Pass down to destination device + */ + if (bio->bi_opf & REQ_PREFLUSH) { + remap_and_issue(clone, bio); + return DM_MAPIO_SUBMITTED; + } + + bio->bi_iter.bi_sector = dm_target_offset(ti, bio->bi_iter.bi_sector); + + /* + * dm-clone interprets discards and performs a fast hydration of the + * discarded regions, i.e., we skip the copy from the source device and + * just mark the regions as hydrated. + */ + if (bio_op(bio) == REQ_OP_DISCARD) { + process_discard_bio(clone, bio); + return DM_MAPIO_SUBMITTED; + } + + /* + * If the bio's region is hydrated, redirect it to the destination + * device. + * + * If the region is not hydrated and the bio is a READ, redirect it to + * the source device. + * + * Else, defer WRITE bio until after its region has been hydrated and + * start the region's hydration immediately. + */ + region_nr = bio_to_region(clone, bio); + if (dm_clone_is_region_hydrated(clone->cmd, region_nr)) { + remap_and_issue(clone, bio); + return DM_MAPIO_SUBMITTED; + } else if (bio_data_dir(bio) == READ) { + remap_to_source(clone, bio); + return DM_MAPIO_REMAPPED; + } + + remap_to_dest(clone, bio); + hydrate_bio_region(clone, bio); + + return DM_MAPIO_SUBMITTED; +} + +static int clone_endio(struct dm_target *ti, struct bio *bio, blk_status_t *error) +{ + struct clone *clone = ti->private; + + atomic_dec(&clone->ios_in_flight); + + return DM_ENDIO_DONE; +} + +static void emit_flags(struct clone *clone, char *result, unsigned int maxlen, + ssize_t *sz_ptr) +{ + ssize_t sz = *sz_ptr; + unsigned int count; + + count = !test_bit(DM_CLONE_HYDRATION_ENABLED, &clone->flags); + count += !test_bit(DM_CLONE_DISCARD_PASSDOWN, &clone->flags); + + DMEMIT("%u ", count); + + if (!test_bit(DM_CLONE_HYDRATION_ENABLED, &clone->flags)) + DMEMIT("no_hydration "); + + if (!test_bit(DM_CLONE_DISCARD_PASSDOWN, &clone->flags)) + DMEMIT("no_discard_passdown "); + + *sz_ptr = sz; +} + +static void emit_core_args(struct clone *clone, char *result, + unsigned int maxlen, ssize_t *sz_ptr) +{ + ssize_t sz = *sz_ptr; + unsigned int count = 4; + + DMEMIT("%u hydration_threshold %u hydration_batch_size %u ", count, + READ_ONCE(clone->hydration_threshold), + READ_ONCE(clone->hydration_batch_size)); + + *sz_ptr = sz; +} + +/* + * Status format: + * + * <metadata block size> <#used metadata blocks>/<#total metadata blocks> + * <clone region size> <#hydrated regions>/<#total regions> <#hydrating regions> + * <#features> <features>* <#core args> <core args>* <clone metadata mode> + */ +static void clone_status(struct dm_target *ti, status_type_t type, + unsigned int status_flags, char *result, + unsigned int maxlen) +{ + int r; + unsigned int i; + ssize_t sz = 0; + dm_block_t nr_free_metadata_blocks = 0; + dm_block_t nr_metadata_blocks = 0; + char buf[BDEVNAME_SIZE]; + struct clone *clone = ti->private; + + switch (type) { + case STATUSTYPE_INFO: + if (get_clone_mode(clone) == 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_metadata(clone); + + r = dm_clone_get_free_metadata_block_count(clone->cmd, &nr_free_metadata_blocks); + + if (r) { + DMERR("%s: dm_clone_get_free_metadata_block_count returned %d", + clone_device_name(clone), r); + goto error; + } + + r = dm_clone_get_metadata_dev_size(clone->cmd, &nr_metadata_blocks); + + if (r) { + DMERR("%s: dm_clone_get_metadata_dev_size returned %d", + clone_device_name(clone), r); + goto error; + } + + DMEMIT("%u %llu/%llu %llu %lu/%lu %u ", + DM_CLONE_METADATA_BLOCK_SIZE, + (unsigned long long)(nr_metadata_blocks - nr_free_metadata_blocks), + (unsigned long long)nr_metadata_blocks, + (unsigned long long)clone->region_size, + dm_clone_nr_of_hydrated_regions(clone->cmd), + clone->nr_regions, + atomic_read(&clone->hydrations_in_flight)); + + emit_flags(clone, result, maxlen, &sz); + emit_core_args(clone, result, maxlen, &sz); + + switch (get_clone_mode(clone)) { + case CM_WRITE: + DMEMIT("rw"); + break; + case CM_READ_ONLY: + DMEMIT("ro"); + break; + case CM_FAIL: + DMEMIT("Fail"); + } + + break; + + case STATUSTYPE_TABLE: + format_dev_t(buf, clone->metadata_dev->bdev->bd_dev); + DMEMIT("%s ", buf); + + format_dev_t(buf, clone->dest_dev->bdev->bd_dev); + DMEMIT("%s ", buf); + + format_dev_t(buf, clone->source_dev->bdev->bd_dev); + DMEMIT("%s", buf); + + for (i = 0; i < clone->nr_ctr_args; i++) + DMEMIT(" %s", clone->ctr_args[i]); + } + + return; + +error: + DMEMIT("Error"); +} + +static int clone_is_congested(struct dm_target_callbacks *cb, int bdi_bits) +{ + struct request_queue *dest_q, *source_q; + struct clone *clone = container_of(cb, struct clone, callbacks); + + source_q = bdev_get_queue(clone->source_dev->bdev); + dest_q = bdev_get_queue(clone->dest_dev->bdev); + + return (bdi_congested(dest_q->backing_dev_info, bdi_bits) | + bdi_congested(source_q->backing_dev_info, bdi_bits)); +} + +static sector_t get_dev_size(struct dm_dev *dev) +{ + return i_size_read(dev->bdev->bd_inode) >> SECTOR_SHIFT; +} + +/*---------------------------------------------------------------------------*/ + +/* + * Construct a clone device mapping: + * + * clone <metadata dev> <destination dev> <source dev> <region size> + * [<#feature args> [<feature arg>]* [<#core args> [key value]*]] + * + * metadata dev: Fast device holding the persistent metadata + * destination dev: The destination device, which will become a clone of the + * source device + * source dev: The read-only source device that gets cloned + * region size: dm-clone unit size in sectors + * + * #feature args: Number of feature arguments passed + * feature args: E.g. no_hydration, no_discard_passdown + * + * #core arguments: An even number of core arguments + * core arguments: Key/value pairs for tuning the core + * E.g. 'hydration_threshold 256' + */ +static int parse_feature_args(struct dm_arg_set *as, struct clone *clone) +{ + int r; + unsigned int argc; + const char *arg_name; + struct dm_target *ti = clone->ti; + + const struct dm_arg args = { + .min = 0, + .max = 2, + .error = "Invalid number of feature arguments" + }; + + /* No feature arguments supplied */ + if (!as->argc) + return 0; + + r = dm_read_arg_group(&args, as, &argc, &ti->error); + if (r) + return r; + + while (argc) { + arg_name = dm_shift_arg(as); + argc--; + + if (!strcasecmp(arg_name, "no_hydration")) { + __clear_bit(DM_CLONE_HYDRATION_ENABLED, &clone->flags); + } else if (!strcasecmp(arg_name, "no_discard_passdown")) { + __clear_bit(DM_CLONE_DISCARD_PASSDOWN, &clone->flags); + } else { + ti->error = "Invalid feature argument"; + return -EINVAL; + } + } + + return 0; +} + +static int parse_core_args(struct dm_arg_set *as, struct clone *clone) +{ + int r; + unsigned int argc; + unsigned int value; + const char *arg_name; + struct dm_target *ti = clone->ti; + + const struct dm_arg args = { + .min = 0, + .max = 4, + .error = "Invalid number of core arguments" + }; + + /* Initialize core arguments */ + clone->hydration_batch_size = DEFAULT_HYDRATION_BATCH_SIZE; + clone->hydration_threshold = DEFAULT_HYDRATION_THRESHOLD; + + /* No core arguments supplied */ + if (!as->argc) + return 0; + + r = dm_read_arg_group(&args, as, &argc, &ti->error); + if (r) + return r; + + if (argc & 1) { + ti->error = "Number of core arguments must be even"; + return -EINVAL; + } + + while (argc) { + arg_name = dm_shift_arg(as); + argc -= 2; + + if (!strcasecmp(arg_name, "hydration_threshold")) { + if (kstrtouint(dm_shift_arg(as), 10, &value)) { + ti->error = "Invalid value for argument `hydration_threshold'"; + return -EINVAL; + } + clone->hydration_threshold = value; + } else if (!strcasecmp(arg_name, "hydration_batch_size")) { + if (kstrtouint(dm_shift_arg(as), 10, &value)) { + ti->error = "Invalid value for argument `hydration_batch_size'"; + return -EINVAL; + } + clone->hydration_batch_size = value; + } else { + ti->error = "Invalid core argument"; + return -EINVAL; + } + } + + return 0; +} + +static int parse_region_size(struct clone *clone, struct dm_arg_set *as, char **error) +{ + int r; + unsigned int region_size; + struct dm_arg arg; + + arg.min = MIN_REGION_SIZE; + arg.max = MAX_REGION_SIZE; + arg.error = "Invalid region size"; + + r = dm_read_arg(&arg, as, ®ion_size, error); + if (r) + return r; + + /* Check region size is a power of 2 */ + if (!is_power_of_2(region_size)) { + *error = "Region size is not a power of 2"; + return -EINVAL; + } + + /* Validate the region size against the device logical block size */ + if (region_size % (bdev_logical_block_size(clone->source_dev->bdev) >> 9) || + region_size % (bdev_logical_block_size(clone->dest_dev->bdev) >> 9)) { + *error = "Region size is not a multiple of device logical block size"; + return -EINVAL; + } + + clone->region_size = region_size; + + return 0; +} + +static int validate_nr_regions(unsigned long n, char **error) +{ + /* + * dm_bitset restricts us to 2^32 regions. test_bit & co. restrict us + * further to 2^31 regions. + */ + if (n > (1UL << 31)) { + *error = "Too many regions. Consider increasing the region size"; + return -EINVAL; + } + + return 0; +} + +static int parse_metadata_dev(struct clone *clone, struct dm_arg_set *as, char **error) +{ + int r; + sector_t metadata_dev_size; + char b[BDEVNAME_SIZE]; + + r = dm_get_device(clone->ti, dm_shift_arg(as), FMODE_READ | FMODE_WRITE, + &clone->metadata_dev); + if (r) { + *error = "Error opening metadata device"; + return r; + } + + metadata_dev_size = get_dev_size(clone->metadata_dev); + if (metadata_dev_size > DM_CLONE_METADATA_MAX_SECTORS_WARNING) + DMWARN("Metadata device %s is larger than %u sectors: excess space will not be used.", + bdevname(clone->metadata_dev->bdev, b), DM_CLONE_METADATA_MAX_SECTORS); + + return 0; +} + +static int parse_dest_dev(struct clone *clone, struct dm_arg_set *as, char **error) +{ + int r; + sector_t dest_dev_size; + + r = dm_get_device(clone->ti, dm_shift_arg(as), FMODE_READ | FMODE_WRITE, + &clone->dest_dev); + if (r) { + *error = "Error opening destination device"; + return r; + } + + dest_dev_size = get_dev_size(clone->dest_dev); + if (dest_dev_size < clone->ti->len) { + dm_put_device(clone->ti, clone->dest_dev); + *error = "Device size larger than destination device"; + return -EINVAL; + } + + return 0; +} + +static int parse_source_dev(struct clone *clone, struct dm_arg_set *as, char **error) +{ + int r; + sector_t source_dev_size; + + r = dm_get_device(clone->ti, dm_shift_arg(as), FMODE_READ, + &clone->source_dev); + if (r) { + *error = "Error opening source device"; + return r; + } + + source_dev_size = get_dev_size(clone->source_dev); + if (source_dev_size < clone->ti->len) { + dm_put_device(clone->ti, clone->source_dev); + *error = "Device size larger than source device"; + return -EINVAL; + } + + return 0; +} + +static int copy_ctr_args(struct clone *clone, int argc, const char **argv, char **error) +{ + unsigned int i; + const char **copy; + + copy = kcalloc(argc, sizeof(*copy), GFP_KERNEL); + if (!copy) + goto error; + + for (i = 0; i < argc; i++) { + copy[i] = kstrdup(argv[i], GFP_KERNEL); + + if (!copy[i]) { + while (i--) + kfree(copy[i]); + kfree(copy); + goto error; + } + } + + clone->nr_ctr_args = argc; + clone->ctr_args = copy; + return 0; + +error: + *error = "Failed to allocate memory for table line"; + return -ENOMEM; +} + +static int clone_ctr(struct dm_target *ti, unsigned int argc, char **argv) +{ + int r; + struct clone *clone; + struct dm_arg_set as; + + if (argc < 4) { + ti->error = "Invalid number of arguments"; + return -EINVAL; + } + + as.argc = argc; + as.argv = argv; + + clone = kzalloc(sizeof(*clone), GFP_KERNEL); + if (!clone) { + ti->error = "Failed to allocate clone structure"; + return -ENOMEM; + } + + clone->ti = ti; + + /* Initialize dm-clone flags */ + __set_bit(DM_CLONE_HYDRATION_ENABLED, &clone->flags); + __set_bit(DM_CLONE_HYDRATION_SUSPENDED, &clone->flags); + __set_bit(DM_CLONE_DISCARD_PASSDOWN, &clone->flags); + + r = parse_metadata_dev(clone, &as, &ti->error); + if (r) + goto out_with_clone; + + r = parse_dest_dev(clone, &as, &ti->error); + if (r) + goto out_with_meta_dev; + + r = parse_source_dev(clone, &as, &ti->error); + if (r) + goto out_with_dest_dev; + + r = parse_region_size(clone, &as, &ti->error); + if (r) + goto out_with_source_dev; + + clone->region_shift = __ffs(clone->region_size); + clone->nr_regions = dm_sector_div_up(ti->len, clone->region_size); + + r = validate_nr_regions(clone->nr_regions, &ti->error); + if (r) + goto out_with_source_dev; + + r = dm_set_target_max_io_len(ti, clone->region_size); + if (r) { + ti->error = "Failed to set max io len"; + goto out_with_source_dev; + } + + r = parse_feature_args(&as, clone); + if (r) + goto out_with_source_dev; + + r = parse_core_args(&as, clone); + if (r) + goto out_with_source_dev; + + /* Load metadata */ + clone->cmd = dm_clone_metadata_open(clone->metadata_dev->bdev, ti->len, + clone->region_size); + if (IS_ERR(clone->cmd)) { + ti->error = "Failed to load metadata"; + r = PTR_ERR(clone->cmd); + goto out_with_source_dev; + } + + __set_clone_mode(clone, CM_WRITE); + + if (get_clone_mode(clone) != CM_WRITE) { + ti->error = "Unable to get write access to metadata, please check/repair metadata"; + r = -EPERM; + goto out_with_metadata; + } + + clone->last_commit_jiffies = jiffies; + + /* Allocate hydration hash table */ + r = hash_table_init(clone); + if (r) { + ti->error = "Failed to allocate hydration hash table"; + goto out_with_metadata; + } + + atomic_set(&clone->ios_in_flight, 0); + init_waitqueue_head(&clone->hydration_stopped); + spin_lock_init(&clone->lock); + bio_list_init(&clone->deferred_bios); + bio_list_init(&clone->deferred_discard_bios); + bio_list_init(&clone->deferred_flush_bios); + bio_list_init(&clone->deferred_flush_completions); + clone->hydration_offset = 0; + atomic_set(&clone->hydrations_in_flight, 0); + + clone->wq = alloc_workqueue("dm-" DM_MSG_PREFIX, WQ_MEM_RECLAIM, 0); + if (!clone->wq) { + ti->error = "Failed to allocate workqueue"; + r = -ENOMEM; + goto out_with_ht; + } + + INIT_WORK(&clone->worker, do_worker); + INIT_DELAYED_WORK(&clone->waker, do_waker); + + clone->kcopyd_client = dm_kcopyd_client_create(&dm_kcopyd_throttle); + if (IS_ERR(clone->kcopyd_client)) { + r = PTR_ERR(clone->kcopyd_client); + goto out_with_wq; + } + + r = mempool_init_slab_pool(&clone->hydration_pool, MIN_HYDRATIONS, + _hydration_cache); + if (r) { + ti->error = "Failed to create dm_clone_region_hydration memory pool"; + goto out_with_kcopyd; + } + + /* Save a copy of the table line */ + r = copy_ctr_args(clone, argc - 3, (const char **)argv + 3, &ti->error); + if (r) + goto out_with_mempool; + + mutex_init(&clone->commit_lock); + clone->callbacks.congested_fn = clone_is_congested; + dm_table_add_target_callbacks(ti->table, &clone->callbacks); + + /* Enable flushes */ + ti->num_flush_bios = 1; + ti->flush_supported = true; + + /* Enable discards */ + ti->discards_supported = true; + ti->num_discard_bios = 1; + + ti->private = clone; + + return 0; + +out_with_mempool: + mempool_exit(&clone->hydration_pool); +out_with_kcopyd: + dm_kcopyd_client_destroy(clone->kcopyd_client); +out_with_wq: + destroy_workqueue(clone->wq); +out_with_ht: + hash_table_exit(clone); +out_with_metadata: + dm_clone_metadata_close(clone->cmd); +out_with_source_dev: + dm_put_device(ti, clone->source_dev); +out_with_dest_dev: + dm_put_device(ti, clone->dest_dev); +out_with_meta_dev: + dm_put_device(ti, clone->metadata_dev); +out_with_clone: + kfree(clone); + + return r; +} + +static void clone_dtr(struct dm_target *ti) +{ + unsigned int i; + struct clone *clone = ti->private; + + mutex_destroy(&clone->commit_lock); + + for (i = 0; i < clone->nr_ctr_args; i++) + kfree(clone->ctr_args[i]); + kfree(clone->ctr_args); + + mempool_exit(&clone->hydration_pool); + dm_kcopyd_client_destroy(clone->kcopyd_client); + destroy_workqueue(clone->wq); + hash_table_exit(clone); + dm_clone_metadata_close(clone->cmd); + dm_put_device(ti, clone->source_dev); + dm_put_device(ti, clone->dest_dev); + dm_put_device(ti, clone->metadata_dev); + + kfree(clone); +} + +/*---------------------------------------------------------------------------*/ + +static void clone_postsuspend(struct dm_target *ti) +{ + struct clone *clone = ti->private; + + /* + * To successfully suspend the device: + * + * - We cancel the delayed work for periodic commits and wait for + * it to finish. + * + * - We stop the background hydration, i.e. we prevent new region + * hydrations from starting. + * + * - We wait for any in-flight hydrations to finish. + * + * - We flush the workqueue. + * + * - We commit the metadata. + */ + cancel_delayed_work_sync(&clone->waker); + + set_bit(DM_CLONE_HYDRATION_SUSPENDED, &clone->flags); + + /* + * Make sure set_bit() is ordered before atomic_read(), otherwise we + * might race with do_hydration() and miss some started region + * hydrations. + * + * This is paired with smp_mb__after_atomic() in do_hydration(). + */ + smp_mb__after_atomic(); + + wait_event(clone->hydration_stopped, !atomic_read(&clone->hydrations_in_flight)); + flush_workqueue(clone->wq); + + (void) commit_metadata(clone); +} + +static void clone_resume(struct dm_target *ti) +{ + struct clone *clone = ti->private; + + clear_bit(DM_CLONE_HYDRATION_SUSPENDED, &clone->flags); + do_waker(&clone->waker.work); +} + +static bool bdev_supports_discards(struct block_device *bdev) +{ + struct request_queue *q = bdev_get_queue(bdev); + + return (q && blk_queue_discard(q)); +} + +/* + * If discard_passdown was enabled verify that the destination device supports + * discards. Disable discard_passdown if not. + */ +static void disable_passdown_if_not_supported(struct clone *clone) +{ + struct block_device *dest_dev = clone->dest_dev->bdev; + struct queue_limits *dest_limits = &bdev_get_queue(dest_dev)->limits; + const char *reason = NULL; + char buf[BDEVNAME_SIZE]; + + if (!test_bit(DM_CLONE_DISCARD_PASSDOWN, &clone->flags)) + return; + + if (!bdev_supports_discards(dest_dev)) + reason = "discard unsupported"; + else if (dest_limits->max_discard_sectors < clone->region_size) + reason = "max discard sectors smaller than a region"; + + if (reason) { + DMWARN("Destination device (%s) %s: Disabling discard passdown.", + bdevname(dest_dev, buf), reason); + clear_bit(DM_CLONE_DISCARD_PASSDOWN, &clone->flags); + } +} + +static void set_discard_limits(struct clone *clone, struct queue_limits *limits) +{ + struct block_device *dest_bdev = clone->dest_dev->bdev; + struct queue_limits *dest_limits = &bdev_get_queue(dest_bdev)->limits; + + if (!test_bit(DM_CLONE_DISCARD_PASSDOWN, &clone->flags)) { + /* No passdown is done so we set our own virtual limits */ + limits->discard_granularity = clone->region_size << SECTOR_SHIFT; + limits->max_discard_sectors = round_down(UINT_MAX >> SECTOR_SHIFT, clone->region_size); + return; + } + + /* + * clone_iterate_devices() is stacking both the source and destination + * device limits but discards aren't passed to the source device, so + * inherit destination's limits. + */ + limits->max_discard_sectors = dest_limits->max_discard_sectors; + limits->max_hw_discard_sectors = dest_limits->max_hw_discard_sectors; + limits->discard_granularity = dest_limits->discard_granularity; + limits->discard_alignment = dest_limits->discard_alignment; + limits->discard_misaligned = dest_limits->discard_misaligned; + limits->max_discard_segments = dest_limits->max_discard_segments; +} + +static void clone_io_hints(struct dm_target *ti, struct queue_limits *limits) +{ + struct clone *clone = ti->private; + u64 io_opt_sectors = limits->io_opt >> SECTOR_SHIFT; + + /* + * If the system-determined stacked limits are compatible with + * dm-clone's region size (io_opt is a factor) do not override them. + */ + if (io_opt_sectors < clone->region_size || + do_div(io_opt_sectors, clone->region_size)) { + blk_limits_io_min(limits, clone->region_size << SECTOR_SHIFT); + blk_limits_io_opt(limits, clone->region_size << SECTOR_SHIFT); + } + + disable_passdown_if_not_supported(clone); + set_discard_limits(clone, limits); +} + +static int clone_iterate_devices(struct dm_target *ti, + iterate_devices_callout_fn fn, void *data) +{ + int ret; + struct clone *clone = ti->private; + struct dm_dev *dest_dev = clone->dest_dev; + struct dm_dev *source_dev = clone->source_dev; + + ret = fn(ti, source_dev, 0, ti->len, data); + if (!ret) + ret = fn(ti, dest_dev, 0, ti->len, data); + return ret; +} + +/* + * dm-clone message functions. + */ +static void set_hydration_threshold(struct clone *clone, unsigned int nr_regions) +{ + WRITE_ONCE(clone->hydration_threshold, nr_regions); + + /* + * If user space sets hydration_threshold to zero then the hydration + * will stop. If at a later time the hydration_threshold is increased + * we must restart the hydration process by waking up the worker. + */ + wake_worker(clone); +} + +static void set_hydration_batch_size(struct clone *clone, unsigned int nr_regions) +{ + WRITE_ONCE(clone->hydration_batch_size, nr_regions); +} + +static void enable_hydration(struct clone *clone) +{ + if (!test_and_set_bit(DM_CLONE_HYDRATION_ENABLED, &clone->flags)) + wake_worker(clone); +} + +static void disable_hydration(struct clone *clone) +{ + clear_bit(DM_CLONE_HYDRATION_ENABLED, &clone->flags); +} + +static int clone_message(struct dm_target *ti, unsigned int argc, char **argv, + char *result, unsigned int maxlen) +{ + struct clone *clone = ti->private; + unsigned int value; + + if (!argc) + return -EINVAL; + + if (!strcasecmp(argv[0], "enable_hydration")) { + enable_hydration(clone); + return 0; + } + + if (!strcasecmp(argv[0], "disable_hydration")) { + disable_hydration(clone); + return 0; + } + + if (argc != 2) + return -EINVAL; + + if (!strcasecmp(argv[0], "hydration_threshold")) { + if (kstrtouint(argv[1], 10, &value)) + return -EINVAL; + + set_hydration_threshold(clone, value); + + return 0; + } + + if (!strcasecmp(argv[0], "hydration_batch_size")) { + if (kstrtouint(argv[1], 10, &value)) + return -EINVAL; + + set_hydration_batch_size(clone, value); + + return 0; + } + + DMERR("%s: Unsupported message `%s'", clone_device_name(clone), argv[0]); + return -EINVAL; +} + +static struct target_type clone_target = { + .name = "clone", + .version = {1, 0, 0}, + .module = THIS_MODULE, + .ctr = clone_ctr, + .dtr = clone_dtr, + .map = clone_map, + .end_io = clone_endio, + .postsuspend = clone_postsuspend, + .resume = clone_resume, + .status = clone_status, + .message = clone_message, + .io_hints = clone_io_hints, + .iterate_devices = clone_iterate_devices, +}; + +/*---------------------------------------------------------------------------*/ + +/* Module functions */ +static int __init dm_clone_init(void) +{ + int r; + + _hydration_cache = KMEM_CACHE(dm_clone_region_hydration, 0); + if (!_hydration_cache) + return -ENOMEM; + + r = dm_register_target(&clone_target); + if (r < 0) { + DMERR("Failed to register clone target"); + return r; + } + + return 0; +} + +static void __exit dm_clone_exit(void) +{ + dm_unregister_target(&clone_target); + + kmem_cache_destroy(_hydration_cache); + _hydration_cache = NULL; +} + +/* Module hooks */ +module_init(dm_clone_init); +module_exit(dm_clone_exit); + +MODULE_DESCRIPTION(DM_NAME " clone target"); +MODULE_AUTHOR("Nikos Tsironis <ntsironis@arrikto.com>"); +MODULE_LICENSE("GPL"); |