diff options
Diffstat (limited to 'drivers/md/dm-snap.c')
| -rw-r--r-- | drivers/md/dm-snap.c | 2866 |
1 files changed, 2866 insertions, 0 deletions
diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c new file mode 100644 index 000000000..b748901a4 --- /dev/null +++ b/drivers/md/dm-snap.c @@ -0,0 +1,2866 @@ +/* + * Copyright (C) 2001-2002 Sistina Software (UK) Limited. + * + * This file is released under the GPL. + */ + +#include <linux/blkdev.h> +#include <linux/device-mapper.h> +#include <linux/delay.h> +#include <linux/fs.h> +#include <linux/init.h> +#include <linux/kdev_t.h> +#include <linux/list.h> +#include <linux/list_bl.h> +#include <linux/mempool.h> +#include <linux/module.h> +#include <linux/slab.h> +#include <linux/vmalloc.h> +#include <linux/log2.h> +#include <linux/dm-kcopyd.h> + +#include "dm.h" + +#include "dm-exception-store.h" + +#define DM_MSG_PREFIX "snapshots" + +static const char dm_snapshot_merge_target_name[] = "snapshot-merge"; + +#define dm_target_is_snapshot_merge(ti) \ + ((ti)->type->name == dm_snapshot_merge_target_name) + +/* + * The size of the mempool used to track chunks in use. + */ +#define MIN_IOS 256 + +#define DM_TRACKED_CHUNK_HASH_SIZE 16 +#define DM_TRACKED_CHUNK_HASH(x) ((unsigned long)(x) & \ + (DM_TRACKED_CHUNK_HASH_SIZE - 1)) + +struct dm_exception_table { + uint32_t hash_mask; + unsigned int hash_shift; + struct hlist_bl_head *table; +}; + +struct dm_snapshot { + struct rw_semaphore lock; + + struct dm_dev *origin; + struct dm_dev *cow; + + struct dm_target *ti; + + /* List of snapshots per Origin */ + struct list_head list; + + /* + * You can't use a snapshot if this is 0 (e.g. if full). + * A snapshot-merge target never clears this. + */ + int valid; + + /* + * The snapshot overflowed because of a write to the snapshot device. + * We don't have to invalidate the snapshot in this case, but we need + * to prevent further writes. + */ + int snapshot_overflowed; + + /* Origin writes don't trigger exceptions until this is set */ + int active; + + atomic_t pending_exceptions_count; + + spinlock_t pe_allocation_lock; + + /* Protected by "pe_allocation_lock" */ + sector_t exception_start_sequence; + + /* Protected by kcopyd single-threaded callback */ + sector_t exception_complete_sequence; + + /* + * A list of pending exceptions that completed out of order. + * Protected by kcopyd single-threaded callback. + */ + struct rb_root out_of_order_tree; + + mempool_t pending_pool; + + struct dm_exception_table pending; + struct dm_exception_table complete; + + /* + * pe_lock protects all pending_exception operations and access + * as well as the snapshot_bios list. + */ + spinlock_t pe_lock; + + /* Chunks with outstanding reads */ + spinlock_t tracked_chunk_lock; + struct hlist_head tracked_chunk_hash[DM_TRACKED_CHUNK_HASH_SIZE]; + + /* The on disk metadata handler */ + struct dm_exception_store *store; + + unsigned int in_progress; + struct wait_queue_head in_progress_wait; + + struct dm_kcopyd_client *kcopyd_client; + + /* Wait for events based on state_bits */ + unsigned long state_bits; + + /* Range of chunks currently being merged. */ + chunk_t first_merging_chunk; + int num_merging_chunks; + + /* + * The merge operation failed if this flag is set. + * Failure modes are handled as follows: + * - I/O error reading the header + * => don't load the target; abort. + * - Header does not have "valid" flag set + * => use the origin; forget about the snapshot. + * - I/O error when reading exceptions + * => don't load the target; abort. + * (We can't use the intermediate origin state.) + * - I/O error while merging + * => stop merging; set merge_failed; process I/O normally. + */ + bool merge_failed:1; + + bool discard_zeroes_cow:1; + bool discard_passdown_origin:1; + + /* + * Incoming bios that overlap with chunks being merged must wait + * for them to be committed. + */ + struct bio_list bios_queued_during_merge; +}; + +/* + * state_bits: + * RUNNING_MERGE - Merge operation is in progress. + * SHUTDOWN_MERGE - Set to signal that merge needs to be stopped; + * cleared afterwards. + */ +#define RUNNING_MERGE 0 +#define SHUTDOWN_MERGE 1 + +/* + * Maximum number of chunks being copied on write. + * + * The value was decided experimentally as a trade-off between memory + * consumption, stalling the kernel's workqueues and maintaining a high enough + * throughput. + */ +#define DEFAULT_COW_THRESHOLD 2048 + +static unsigned int cow_threshold = DEFAULT_COW_THRESHOLD; +module_param_named(snapshot_cow_threshold, cow_threshold, uint, 0644); +MODULE_PARM_DESC(snapshot_cow_threshold, "Maximum number of chunks being copied on write"); + +DECLARE_DM_KCOPYD_THROTTLE_WITH_MODULE_PARM(snapshot_copy_throttle, + "A percentage of time allocated for copy on write"); + +struct dm_dev *dm_snap_origin(struct dm_snapshot *s) +{ + return s->origin; +} +EXPORT_SYMBOL(dm_snap_origin); + +struct dm_dev *dm_snap_cow(struct dm_snapshot *s) +{ + return s->cow; +} +EXPORT_SYMBOL(dm_snap_cow); + +static sector_t chunk_to_sector(struct dm_exception_store *store, + chunk_t chunk) +{ + return chunk << store->chunk_shift; +} + +static int bdev_equal(struct block_device *lhs, struct block_device *rhs) +{ + /* + * There is only ever one instance of a particular block + * device so we can compare pointers safely. + */ + return lhs == rhs; +} + +struct dm_snap_pending_exception { + struct dm_exception e; + + /* + * Origin buffers waiting for this to complete are held + * in a bio list + */ + struct bio_list origin_bios; + struct bio_list snapshot_bios; + + /* Pointer back to snapshot context */ + struct dm_snapshot *snap; + + /* + * 1 indicates the exception has already been sent to + * kcopyd. + */ + int started; + + /* There was copying error. */ + int copy_error; + + /* A sequence number, it is used for in-order completion. */ + sector_t exception_sequence; + + struct rb_node out_of_order_node; + + /* + * For writing a complete chunk, bypassing the copy. + */ + struct bio *full_bio; + bio_end_io_t *full_bio_end_io; +}; + +/* + * Hash table mapping origin volumes to lists of snapshots and + * a lock to protect it + */ +static struct kmem_cache *exception_cache; +static struct kmem_cache *pending_cache; + +struct dm_snap_tracked_chunk { + struct hlist_node node; + chunk_t chunk; +}; + +static void init_tracked_chunk(struct bio *bio) +{ + struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk)); + INIT_HLIST_NODE(&c->node); +} + +static bool is_bio_tracked(struct bio *bio) +{ + struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk)); + return !hlist_unhashed(&c->node); +} + +static void track_chunk(struct dm_snapshot *s, struct bio *bio, chunk_t chunk) +{ + struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk)); + + c->chunk = chunk; + + spin_lock_irq(&s->tracked_chunk_lock); + hlist_add_head(&c->node, + &s->tracked_chunk_hash[DM_TRACKED_CHUNK_HASH(chunk)]); + spin_unlock_irq(&s->tracked_chunk_lock); +} + +static void stop_tracking_chunk(struct dm_snapshot *s, struct bio *bio) +{ + struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk)); + unsigned long flags; + + spin_lock_irqsave(&s->tracked_chunk_lock, flags); + hlist_del(&c->node); + spin_unlock_irqrestore(&s->tracked_chunk_lock, flags); +} + +static int __chunk_is_tracked(struct dm_snapshot *s, chunk_t chunk) +{ + struct dm_snap_tracked_chunk *c; + int found = 0; + + spin_lock_irq(&s->tracked_chunk_lock); + + hlist_for_each_entry(c, + &s->tracked_chunk_hash[DM_TRACKED_CHUNK_HASH(chunk)], node) { + if (c->chunk == chunk) { + found = 1; + break; + } + } + + spin_unlock_irq(&s->tracked_chunk_lock); + + return found; +} + +/* + * This conflicting I/O is extremely improbable in the caller, + * so msleep(1) is sufficient and there is no need for a wait queue. + */ +static void __check_for_conflicting_io(struct dm_snapshot *s, chunk_t chunk) +{ + while (__chunk_is_tracked(s, chunk)) + msleep(1); +} + +/* + * One of these per registered origin, held in the snapshot_origins hash + */ +struct origin { + /* The origin device */ + struct block_device *bdev; + + struct list_head hash_list; + + /* List of snapshots for this origin */ + struct list_head snapshots; +}; + +/* + * This structure is allocated for each origin target + */ +struct dm_origin { + struct dm_dev *dev; + struct dm_target *ti; + unsigned int split_boundary; + struct list_head hash_list; +}; + +/* + * Size of the hash table for origin volumes. If we make this + * the size of the minors list then it should be nearly perfect + */ +#define ORIGIN_HASH_SIZE 256 +#define ORIGIN_MASK 0xFF +static struct list_head *_origins; +static struct list_head *_dm_origins; +static struct rw_semaphore _origins_lock; + +static DECLARE_WAIT_QUEUE_HEAD(_pending_exceptions_done); +static DEFINE_SPINLOCK(_pending_exceptions_done_spinlock); +static uint64_t _pending_exceptions_done_count; + +static int init_origin_hash(void) +{ + int i; + + _origins = kmalloc_array(ORIGIN_HASH_SIZE, sizeof(struct list_head), + GFP_KERNEL); + if (!_origins) { + DMERR("unable to allocate memory for _origins"); + return -ENOMEM; + } + for (i = 0; i < ORIGIN_HASH_SIZE; i++) + INIT_LIST_HEAD(_origins + i); + + _dm_origins = kmalloc_array(ORIGIN_HASH_SIZE, + sizeof(struct list_head), + GFP_KERNEL); + if (!_dm_origins) { + DMERR("unable to allocate memory for _dm_origins"); + kfree(_origins); + return -ENOMEM; + } + for (i = 0; i < ORIGIN_HASH_SIZE; i++) + INIT_LIST_HEAD(_dm_origins + i); + + init_rwsem(&_origins_lock); + + return 0; +} + +static void exit_origin_hash(void) +{ + kfree(_origins); + kfree(_dm_origins); +} + +static unsigned int origin_hash(struct block_device *bdev) +{ + return bdev->bd_dev & ORIGIN_MASK; +} + +static struct origin *__lookup_origin(struct block_device *origin) +{ + struct list_head *ol; + struct origin *o; + + ol = &_origins[origin_hash(origin)]; + list_for_each_entry(o, ol, hash_list) + if (bdev_equal(o->bdev, origin)) + return o; + + return NULL; +} + +static void __insert_origin(struct origin *o) +{ + struct list_head *sl = &_origins[origin_hash(o->bdev)]; + list_add_tail(&o->hash_list, sl); +} + +static struct dm_origin *__lookup_dm_origin(struct block_device *origin) +{ + struct list_head *ol; + struct dm_origin *o; + + ol = &_dm_origins[origin_hash(origin)]; + list_for_each_entry(o, ol, hash_list) + if (bdev_equal(o->dev->bdev, origin)) + return o; + + return NULL; +} + +static void __insert_dm_origin(struct dm_origin *o) +{ + struct list_head *sl = &_dm_origins[origin_hash(o->dev->bdev)]; + list_add_tail(&o->hash_list, sl); +} + +static void __remove_dm_origin(struct dm_origin *o) +{ + list_del(&o->hash_list); +} + +/* + * _origins_lock must be held when calling this function. + * Returns number of snapshots registered using the supplied cow device, plus: + * snap_src - a snapshot suitable for use as a source of exception handover + * snap_dest - a snapshot capable of receiving exception handover. + * snap_merge - an existing snapshot-merge target linked to the same origin. + * There can be at most one snapshot-merge target. The parameter is optional. + * + * Possible return values and states of snap_src and snap_dest. + * 0: NULL, NULL - first new snapshot + * 1: snap_src, NULL - normal snapshot + * 2: snap_src, snap_dest - waiting for handover + * 2: snap_src, NULL - handed over, waiting for old to be deleted + * 1: NULL, snap_dest - source got destroyed without handover + */ +static int __find_snapshots_sharing_cow(struct dm_snapshot *snap, + struct dm_snapshot **snap_src, + struct dm_snapshot **snap_dest, + struct dm_snapshot **snap_merge) +{ + struct dm_snapshot *s; + struct origin *o; + int count = 0; + int active; + + o = __lookup_origin(snap->origin->bdev); + if (!o) + goto out; + + list_for_each_entry(s, &o->snapshots, list) { + if (dm_target_is_snapshot_merge(s->ti) && snap_merge) + *snap_merge = s; + if (!bdev_equal(s->cow->bdev, snap->cow->bdev)) + continue; + + down_read(&s->lock); + active = s->active; + up_read(&s->lock); + + if (active) { + if (snap_src) + *snap_src = s; + } else if (snap_dest) + *snap_dest = s; + + count++; + } + +out: + return count; +} + +/* + * On success, returns 1 if this snapshot is a handover destination, + * otherwise returns 0. + */ +static int __validate_exception_handover(struct dm_snapshot *snap) +{ + struct dm_snapshot *snap_src = NULL, *snap_dest = NULL; + struct dm_snapshot *snap_merge = NULL; + + /* Does snapshot need exceptions handed over to it? */ + if ((__find_snapshots_sharing_cow(snap, &snap_src, &snap_dest, + &snap_merge) == 2) || + snap_dest) { + snap->ti->error = "Snapshot cow pairing for exception table handover failed"; + return -EINVAL; + } + + /* + * If no snap_src was found, snap cannot become a handover + * destination. + */ + if (!snap_src) + return 0; + + /* + * Non-snapshot-merge handover? + */ + if (!dm_target_is_snapshot_merge(snap->ti)) + return 1; + + /* + * Do not allow more than one merging snapshot. + */ + if (snap_merge) { + snap->ti->error = "A snapshot is already merging."; + return -EINVAL; + } + + if (!snap_src->store->type->prepare_merge || + !snap_src->store->type->commit_merge) { + snap->ti->error = "Snapshot exception store does not support snapshot-merge."; + return -EINVAL; + } + + return 1; +} + +static void __insert_snapshot(struct origin *o, struct dm_snapshot *s) +{ + struct dm_snapshot *l; + + /* Sort the list according to chunk size, largest-first smallest-last */ + list_for_each_entry(l, &o->snapshots, list) + if (l->store->chunk_size < s->store->chunk_size) + break; + list_add_tail(&s->list, &l->list); +} + +/* + * Make a note of the snapshot and its origin so we can look it + * up when the origin has a write on it. + * + * Also validate snapshot exception store handovers. + * On success, returns 1 if this registration is a handover destination, + * otherwise returns 0. + */ +static int register_snapshot(struct dm_snapshot *snap) +{ + struct origin *o, *new_o = NULL; + struct block_device *bdev = snap->origin->bdev; + int r = 0; + + new_o = kmalloc(sizeof(*new_o), GFP_KERNEL); + if (!new_o) + return -ENOMEM; + + down_write(&_origins_lock); + + r = __validate_exception_handover(snap); + if (r < 0) { + kfree(new_o); + goto out; + } + + o = __lookup_origin(bdev); + if (o) + kfree(new_o); + else { + /* New origin */ + o = new_o; + + /* Initialise the struct */ + INIT_LIST_HEAD(&o->snapshots); + o->bdev = bdev; + + __insert_origin(o); + } + + __insert_snapshot(o, snap); + +out: + up_write(&_origins_lock); + + return r; +} + +/* + * Move snapshot to correct place in list according to chunk size. + */ +static void reregister_snapshot(struct dm_snapshot *s) +{ + struct block_device *bdev = s->origin->bdev; + + down_write(&_origins_lock); + + list_del(&s->list); + __insert_snapshot(__lookup_origin(bdev), s); + + up_write(&_origins_lock); +} + +static void unregister_snapshot(struct dm_snapshot *s) +{ + struct origin *o; + + down_write(&_origins_lock); + o = __lookup_origin(s->origin->bdev); + + list_del(&s->list); + if (o && list_empty(&o->snapshots)) { + list_del(&o->hash_list); + kfree(o); + } + + up_write(&_origins_lock); +} + +/* + * Implementation of the exception hash tables. + * The lowest hash_shift bits of the chunk number are ignored, allowing + * some consecutive chunks to be grouped together. + */ +static uint32_t exception_hash(struct dm_exception_table *et, chunk_t chunk); + +/* Lock to protect access to the completed and pending exception hash tables. */ +struct dm_exception_table_lock { + struct hlist_bl_head *complete_slot; + struct hlist_bl_head *pending_slot; +}; + +static void dm_exception_table_lock_init(struct dm_snapshot *s, chunk_t chunk, + struct dm_exception_table_lock *lock) +{ + struct dm_exception_table *complete = &s->complete; + struct dm_exception_table *pending = &s->pending; + + lock->complete_slot = &complete->table[exception_hash(complete, chunk)]; + lock->pending_slot = &pending->table[exception_hash(pending, chunk)]; +} + +static void dm_exception_table_lock(struct dm_exception_table_lock *lock) +{ + hlist_bl_lock(lock->complete_slot); + hlist_bl_lock(lock->pending_slot); +} + +static void dm_exception_table_unlock(struct dm_exception_table_lock *lock) +{ + hlist_bl_unlock(lock->pending_slot); + hlist_bl_unlock(lock->complete_slot); +} + +static int dm_exception_table_init(struct dm_exception_table *et, + uint32_t size, unsigned int hash_shift) +{ + unsigned int i; + + et->hash_shift = hash_shift; + et->hash_mask = size - 1; + et->table = kvmalloc_array(size, sizeof(struct hlist_bl_head), + GFP_KERNEL); + if (!et->table) + return -ENOMEM; + + for (i = 0; i < size; i++) + INIT_HLIST_BL_HEAD(et->table + i); + + return 0; +} + +static void dm_exception_table_exit(struct dm_exception_table *et, + struct kmem_cache *mem) +{ + struct hlist_bl_head *slot; + struct dm_exception *ex; + struct hlist_bl_node *pos, *n; + int i, size; + + size = et->hash_mask + 1; + for (i = 0; i < size; i++) { + slot = et->table + i; + + hlist_bl_for_each_entry_safe(ex, pos, n, slot, hash_list) + kmem_cache_free(mem, ex); + } + + kvfree(et->table); +} + +static uint32_t exception_hash(struct dm_exception_table *et, chunk_t chunk) +{ + return (chunk >> et->hash_shift) & et->hash_mask; +} + +static void dm_remove_exception(struct dm_exception *e) +{ + hlist_bl_del(&e->hash_list); +} + +/* + * Return the exception data for a sector, or NULL if not + * remapped. + */ +static struct dm_exception *dm_lookup_exception(struct dm_exception_table *et, + chunk_t chunk) +{ + struct hlist_bl_head *slot; + struct hlist_bl_node *pos; + struct dm_exception *e; + + slot = &et->table[exception_hash(et, chunk)]; + hlist_bl_for_each_entry(e, pos, slot, hash_list) + if (chunk >= e->old_chunk && + chunk <= e->old_chunk + dm_consecutive_chunk_count(e)) + return e; + + return NULL; +} + +static struct dm_exception *alloc_completed_exception(gfp_t gfp) +{ + struct dm_exception *e; + + e = kmem_cache_alloc(exception_cache, gfp); + if (!e && gfp == GFP_NOIO) + e = kmem_cache_alloc(exception_cache, GFP_ATOMIC); + + return e; +} + +static void free_completed_exception(struct dm_exception *e) +{ + kmem_cache_free(exception_cache, e); +} + +static struct dm_snap_pending_exception *alloc_pending_exception(struct dm_snapshot *s) +{ + struct dm_snap_pending_exception *pe = mempool_alloc(&s->pending_pool, + GFP_NOIO); + + atomic_inc(&s->pending_exceptions_count); + pe->snap = s; + + return pe; +} + +static void free_pending_exception(struct dm_snap_pending_exception *pe) +{ + struct dm_snapshot *s = pe->snap; + + mempool_free(pe, &s->pending_pool); + smp_mb__before_atomic(); + atomic_dec(&s->pending_exceptions_count); +} + +static void dm_insert_exception(struct dm_exception_table *eh, + struct dm_exception *new_e) +{ + struct hlist_bl_head *l; + struct hlist_bl_node *pos; + struct dm_exception *e = NULL; + + l = &eh->table[exception_hash(eh, new_e->old_chunk)]; + + /* Add immediately if this table doesn't support consecutive chunks */ + if (!eh->hash_shift) + goto out; + + /* List is ordered by old_chunk */ + hlist_bl_for_each_entry(e, pos, l, hash_list) { + /* Insert after an existing chunk? */ + if (new_e->old_chunk == (e->old_chunk + + dm_consecutive_chunk_count(e) + 1) && + new_e->new_chunk == (dm_chunk_number(e->new_chunk) + + dm_consecutive_chunk_count(e) + 1)) { + dm_consecutive_chunk_count_inc(e); + free_completed_exception(new_e); + return; + } + + /* Insert before an existing chunk? */ + if (new_e->old_chunk == (e->old_chunk - 1) && + new_e->new_chunk == (dm_chunk_number(e->new_chunk) - 1)) { + dm_consecutive_chunk_count_inc(e); + e->old_chunk--; + e->new_chunk--; + free_completed_exception(new_e); + return; + } + + if (new_e->old_chunk < e->old_chunk) + break; + } + +out: + if (!e) { + /* + * Either the table doesn't support consecutive chunks or slot + * l is empty. + */ + hlist_bl_add_head(&new_e->hash_list, l); + } else if (new_e->old_chunk < e->old_chunk) { + /* Add before an existing exception */ + hlist_bl_add_before(&new_e->hash_list, &e->hash_list); + } else { + /* Add to l's tail: e is the last exception in this slot */ + hlist_bl_add_behind(&new_e->hash_list, &e->hash_list); + } +} + +/* + * Callback used by the exception stores to load exceptions when + * initialising. + */ +static int dm_add_exception(void *context, chunk_t old, chunk_t new) +{ + struct dm_exception_table_lock lock; + struct dm_snapshot *s = context; + struct dm_exception *e; + + e = alloc_completed_exception(GFP_KERNEL); + if (!e) + return -ENOMEM; + + e->old_chunk = old; + + /* Consecutive_count is implicitly initialised to zero */ + e->new_chunk = new; + + /* + * Although there is no need to lock access to the exception tables + * here, if we don't then hlist_bl_add_head(), called by + * dm_insert_exception(), will complain about accessing the + * corresponding list without locking it first. + */ + dm_exception_table_lock_init(s, old, &lock); + + dm_exception_table_lock(&lock); + dm_insert_exception(&s->complete, e); + dm_exception_table_unlock(&lock); + + return 0; +} + +/* + * Return a minimum chunk size of all snapshots that have the specified origin. + * Return zero if the origin has no snapshots. + */ +static uint32_t __minimum_chunk_size(struct origin *o) +{ + struct dm_snapshot *snap; + unsigned int chunk_size = rounddown_pow_of_two(UINT_MAX); + + if (o) + list_for_each_entry(snap, &o->snapshots, list) + chunk_size = min_not_zero(chunk_size, + snap->store->chunk_size); + + return (uint32_t) chunk_size; +} + +/* + * Hard coded magic. + */ +static int calc_max_buckets(void) +{ + /* use a fixed size of 2MB */ + unsigned long mem = 2 * 1024 * 1024; + mem /= sizeof(struct hlist_bl_head); + + return mem; +} + +/* + * Allocate room for a suitable hash table. + */ +static int init_hash_tables(struct dm_snapshot *s) +{ + sector_t hash_size, cow_dev_size, max_buckets; + + /* + * Calculate based on the size of the original volume or + * the COW volume... + */ + cow_dev_size = get_dev_size(s->cow->bdev); + max_buckets = calc_max_buckets(); + + hash_size = cow_dev_size >> s->store->chunk_shift; + hash_size = min(hash_size, max_buckets); + + if (hash_size < 64) + hash_size = 64; + hash_size = rounddown_pow_of_two(hash_size); + if (dm_exception_table_init(&s->complete, hash_size, + DM_CHUNK_CONSECUTIVE_BITS)) + return -ENOMEM; + + /* + * Allocate hash table for in-flight exceptions + * Make this smaller than the real hash table + */ + hash_size >>= 3; + if (hash_size < 64) + hash_size = 64; + + if (dm_exception_table_init(&s->pending, hash_size, 0)) { + dm_exception_table_exit(&s->complete, exception_cache); + return -ENOMEM; + } + + return 0; +} + +static void merge_shutdown(struct dm_snapshot *s) +{ + clear_bit_unlock(RUNNING_MERGE, &s->state_bits); + smp_mb__after_atomic(); + wake_up_bit(&s->state_bits, RUNNING_MERGE); +} + +static struct bio *__release_queued_bios_after_merge(struct dm_snapshot *s) +{ + s->first_merging_chunk = 0; + s->num_merging_chunks = 0; + + return bio_list_get(&s->bios_queued_during_merge); +} + +/* + * Remove one chunk from the index of completed exceptions. + */ +static int __remove_single_exception_chunk(struct dm_snapshot *s, + chunk_t old_chunk) +{ + struct dm_exception *e; + + e = dm_lookup_exception(&s->complete, old_chunk); + if (!e) { + DMERR("Corruption detected: exception for block %llu is on disk but not in memory", + (unsigned long long)old_chunk); + return -EINVAL; + } + + /* + * If this is the only chunk using this exception, remove exception. + */ + if (!dm_consecutive_chunk_count(e)) { + dm_remove_exception(e); + free_completed_exception(e); + return 0; + } + + /* + * The chunk may be either at the beginning or the end of a + * group of consecutive chunks - never in the middle. We are + * removing chunks in the opposite order to that in which they + * were added, so this should always be true. + * Decrement the consecutive chunk counter and adjust the + * starting point if necessary. + */ + if (old_chunk == e->old_chunk) { + e->old_chunk++; + e->new_chunk++; + } else if (old_chunk != e->old_chunk + + dm_consecutive_chunk_count(e)) { + DMERR("Attempt to merge block %llu from the middle of a chunk range [%llu - %llu]", + (unsigned long long)old_chunk, + (unsigned long long)e->old_chunk, + (unsigned long long) + e->old_chunk + dm_consecutive_chunk_count(e)); + return -EINVAL; + } + + dm_consecutive_chunk_count_dec(e); + + return 0; +} + +static void flush_bios(struct bio *bio); + +static int remove_single_exception_chunk(struct dm_snapshot *s) +{ + struct bio *b = NULL; + int r; + chunk_t old_chunk = s->first_merging_chunk + s->num_merging_chunks - 1; + + down_write(&s->lock); + + /* + * Process chunks (and associated exceptions) in reverse order + * so that dm_consecutive_chunk_count_dec() accounting works. + */ + do { + r = __remove_single_exception_chunk(s, old_chunk); + if (r) + goto out; + } while (old_chunk-- > s->first_merging_chunk); + + b = __release_queued_bios_after_merge(s); + +out: + up_write(&s->lock); + if (b) + flush_bios(b); + + return r; +} + +static int origin_write_extent(struct dm_snapshot *merging_snap, + sector_t sector, unsigned int chunk_size); + +static void merge_callback(int read_err, unsigned long write_err, + void *context); + +static uint64_t read_pending_exceptions_done_count(void) +{ + uint64_t pending_exceptions_done; + + spin_lock(&_pending_exceptions_done_spinlock); + pending_exceptions_done = _pending_exceptions_done_count; + spin_unlock(&_pending_exceptions_done_spinlock); + + return pending_exceptions_done; +} + +static void increment_pending_exceptions_done_count(void) +{ + spin_lock(&_pending_exceptions_done_spinlock); + _pending_exceptions_done_count++; + spin_unlock(&_pending_exceptions_done_spinlock); + + wake_up_all(&_pending_exceptions_done); +} + +static void snapshot_merge_next_chunks(struct dm_snapshot *s) +{ + int i, linear_chunks; + chunk_t old_chunk, new_chunk; + struct dm_io_region src, dest; + sector_t io_size; + uint64_t previous_count; + + BUG_ON(!test_bit(RUNNING_MERGE, &s->state_bits)); + if (unlikely(test_bit(SHUTDOWN_MERGE, &s->state_bits))) + goto shut; + + /* + * valid flag never changes during merge, so no lock required. + */ + if (!s->valid) { + DMERR("Snapshot is invalid: can't merge"); + goto shut; + } + + linear_chunks = s->store->type->prepare_merge(s->store, &old_chunk, + &new_chunk); + if (linear_chunks <= 0) { + if (linear_chunks < 0) { + DMERR("Read error in exception store: shutting down merge"); + down_write(&s->lock); + s->merge_failed = true; + up_write(&s->lock); + } + goto shut; + } + + /* Adjust old_chunk and new_chunk to reflect start of linear region */ + old_chunk = old_chunk + 1 - linear_chunks; + new_chunk = new_chunk + 1 - linear_chunks; + + /* + * Use one (potentially large) I/O to copy all 'linear_chunks' + * from the exception store to the origin + */ + io_size = linear_chunks * s->store->chunk_size; + + dest.bdev = s->origin->bdev; + dest.sector = chunk_to_sector(s->store, old_chunk); + dest.count = min(io_size, get_dev_size(dest.bdev) - dest.sector); + + src.bdev = s->cow->bdev; + src.sector = chunk_to_sector(s->store, new_chunk); + src.count = dest.count; + + /* + * Reallocate any exceptions needed in other snapshots then + * wait for the pending exceptions to complete. + * Each time any pending exception (globally on the system) + * completes we are woken and repeat the process to find out + * if we can proceed. While this may not seem a particularly + * efficient algorithm, it is not expected to have any + * significant impact on performance. + */ + previous_count = read_pending_exceptions_done_count(); + while (origin_write_extent(s, dest.sector, io_size)) { + wait_event(_pending_exceptions_done, + (read_pending_exceptions_done_count() != + previous_count)); + /* Retry after the wait, until all exceptions are done. */ + previous_count = read_pending_exceptions_done_count(); + } + + down_write(&s->lock); + s->first_merging_chunk = old_chunk; + s->num_merging_chunks = linear_chunks; + up_write(&s->lock); + + /* Wait until writes to all 'linear_chunks' drain */ + for (i = 0; i < linear_chunks; i++) + __check_for_conflicting_io(s, old_chunk + i); + + dm_kcopyd_copy(s->kcopyd_client, &src, 1, &dest, 0, merge_callback, s); + return; + +shut: + merge_shutdown(s); +} + +static void error_bios(struct bio *bio); + +static void merge_callback(int read_err, unsigned long write_err, void *context) +{ + struct dm_snapshot *s = context; + struct bio *b = NULL; + + if (read_err || write_err) { + if (read_err) + DMERR("Read error: shutting down merge."); + else + DMERR("Write error: shutting down merge."); + goto shut; + } + + if (blkdev_issue_flush(s->origin->bdev) < 0) { + DMERR("Flush after merge failed: shutting down merge"); + goto shut; + } + + if (s->store->type->commit_merge(s->store, + s->num_merging_chunks) < 0) { + DMERR("Write error in exception store: shutting down merge"); + goto shut; + } + + if (remove_single_exception_chunk(s) < 0) + goto shut; + + snapshot_merge_next_chunks(s); + + return; + +shut: + down_write(&s->lock); + s->merge_failed = true; + b = __release_queued_bios_after_merge(s); + up_write(&s->lock); + error_bios(b); + + merge_shutdown(s); +} + +static void start_merge(struct dm_snapshot *s) +{ + if (!test_and_set_bit(RUNNING_MERGE, &s->state_bits)) + snapshot_merge_next_chunks(s); +} + +/* + * Stop the merging process and wait until it finishes. + */ +static void stop_merge(struct dm_snapshot *s) +{ + set_bit(SHUTDOWN_MERGE, &s->state_bits); + wait_on_bit(&s->state_bits, RUNNING_MERGE, TASK_UNINTERRUPTIBLE); + clear_bit(SHUTDOWN_MERGE, &s->state_bits); +} + +static int parse_snapshot_features(struct dm_arg_set *as, struct dm_snapshot *s, + struct dm_target *ti) +{ + int r; + unsigned int argc; + const char *arg_name; + + static const struct dm_arg _args[] = { + {0, 2, "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 -EINVAL; + + while (argc && !r) { + arg_name = dm_shift_arg(as); + argc--; + + if (!strcasecmp(arg_name, "discard_zeroes_cow")) + s->discard_zeroes_cow = true; + + else if (!strcasecmp(arg_name, "discard_passdown_origin")) + s->discard_passdown_origin = true; + + else { + ti->error = "Unrecognised feature requested"; + r = -EINVAL; + break; + } + } + + if (!s->discard_zeroes_cow && s->discard_passdown_origin) { + /* + * TODO: really these are disjoint.. but ti->num_discard_bios + * and dm_bio_get_target_bio_nr() require rigid constraints. + */ + ti->error = "discard_passdown_origin feature depends on discard_zeroes_cow"; + r = -EINVAL; + } + + return r; +} + +/* + * Construct a snapshot mapping: + * <origin_dev> <COW-dev> <p|po|n> <chunk-size> [<# feature args> [<arg>]*] + */ +static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv) +{ + struct dm_snapshot *s; + struct dm_arg_set as; + int i; + int r = -EINVAL; + char *origin_path, *cow_path; + dev_t origin_dev, cow_dev; + unsigned int args_used, num_flush_bios = 1; + fmode_t origin_mode = FMODE_READ; + + if (argc < 4) { + ti->error = "requires 4 or more arguments"; + r = -EINVAL; + goto bad; + } + + if (dm_target_is_snapshot_merge(ti)) { + num_flush_bios = 2; + origin_mode = FMODE_WRITE; + } + + s = kzalloc(sizeof(*s), GFP_KERNEL); + if (!s) { + ti->error = "Cannot allocate private snapshot structure"; + r = -ENOMEM; + goto bad; + } + + as.argc = argc; + as.argv = argv; + dm_consume_args(&as, 4); + r = parse_snapshot_features(&as, s, ti); + if (r) + goto bad_features; + + origin_path = argv[0]; + argv++; + argc--; + + r = dm_get_device(ti, origin_path, origin_mode, &s->origin); + if (r) { + ti->error = "Cannot get origin device"; + goto bad_origin; + } + origin_dev = s->origin->bdev->bd_dev; + + cow_path = argv[0]; + argv++; + argc--; + + cow_dev = dm_get_dev_t(cow_path); + if (cow_dev && cow_dev == origin_dev) { + ti->error = "COW device cannot be the same as origin device"; + r = -EINVAL; + goto bad_cow; + } + + r = dm_get_device(ti, cow_path, dm_table_get_mode(ti->table), &s->cow); + if (r) { + ti->error = "Cannot get COW device"; + goto bad_cow; + } + + r = dm_exception_store_create(ti, argc, argv, s, &args_used, &s->store); + if (r) { + ti->error = "Couldn't create exception store"; + r = -EINVAL; + goto bad_store; + } + + argv += args_used; + argc -= args_used; + + s->ti = ti; + s->valid = 1; + s->snapshot_overflowed = 0; + s->active = 0; + atomic_set(&s->pending_exceptions_count, 0); + spin_lock_init(&s->pe_allocation_lock); + s->exception_start_sequence = 0; + s->exception_complete_sequence = 0; + s->out_of_order_tree = RB_ROOT; + init_rwsem(&s->lock); + INIT_LIST_HEAD(&s->list); + spin_lock_init(&s->pe_lock); + s->state_bits = 0; + s->merge_failed = false; + s->first_merging_chunk = 0; + s->num_merging_chunks = 0; + bio_list_init(&s->bios_queued_during_merge); + + /* Allocate hash table for COW data */ + if (init_hash_tables(s)) { + ti->error = "Unable to allocate hash table space"; + r = -ENOMEM; + goto bad_hash_tables; + } + + init_waitqueue_head(&s->in_progress_wait); + + s->kcopyd_client = dm_kcopyd_client_create(&dm_kcopyd_throttle); + if (IS_ERR(s->kcopyd_client)) { + r = PTR_ERR(s->kcopyd_client); + ti->error = "Could not create kcopyd client"; + goto bad_kcopyd; + } + + r = mempool_init_slab_pool(&s->pending_pool, MIN_IOS, pending_cache); + if (r) { + ti->error = "Could not allocate mempool for pending exceptions"; + goto bad_pending_pool; + } + + for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++) + INIT_HLIST_HEAD(&s->tracked_chunk_hash[i]); + + spin_lock_init(&s->tracked_chunk_lock); + + ti->private = s; + ti->num_flush_bios = num_flush_bios; + if (s->discard_zeroes_cow) + ti->num_discard_bios = (s->discard_passdown_origin ? 2 : 1); + ti->per_io_data_size = sizeof(struct dm_snap_tracked_chunk); + + /* Add snapshot to the list of snapshots for this origin */ + /* Exceptions aren't triggered till snapshot_resume() is called */ + r = register_snapshot(s); + if (r == -ENOMEM) { + ti->error = "Snapshot origin struct allocation failed"; + goto bad_load_and_register; + } else if (r < 0) { + /* invalid handover, register_snapshot has set ti->error */ + goto bad_load_and_register; + } + + /* + * Metadata must only be loaded into one table at once, so skip this + * if metadata will be handed over during resume. + * Chunk size will be set during the handover - set it to zero to + * ensure it's ignored. + */ + if (r > 0) { + s->store->chunk_size = 0; + return 0; + } + + r = s->store->type->read_metadata(s->store, dm_add_exception, + (void *)s); + if (r < 0) { + ti->error = "Failed to read snapshot metadata"; + goto bad_read_metadata; + } else if (r > 0) { + s->valid = 0; + DMWARN("Snapshot is marked invalid."); + } + + if (!s->store->chunk_size) { + ti->error = "Chunk size not set"; + r = -EINVAL; + goto bad_read_metadata; + } + + r = dm_set_target_max_io_len(ti, s->store->chunk_size); + if (r) + goto bad_read_metadata; + + return 0; + +bad_read_metadata: + unregister_snapshot(s); +bad_load_and_register: + mempool_exit(&s->pending_pool); +bad_pending_pool: + dm_kcopyd_client_destroy(s->kcopyd_client); +bad_kcopyd: + dm_exception_table_exit(&s->pending, pending_cache); + dm_exception_table_exit(&s->complete, exception_cache); +bad_hash_tables: + dm_exception_store_destroy(s->store); +bad_store: + dm_put_device(ti, s->cow); +bad_cow: + dm_put_device(ti, s->origin); +bad_origin: +bad_features: + kfree(s); +bad: + return r; +} + +static void __free_exceptions(struct dm_snapshot *s) +{ + dm_kcopyd_client_destroy(s->kcopyd_client); + s->kcopyd_client = NULL; + + dm_exception_table_exit(&s->pending, pending_cache); + dm_exception_table_exit(&s->complete, exception_cache); +} + +static void __handover_exceptions(struct dm_snapshot *snap_src, + struct dm_snapshot *snap_dest) +{ + union { + struct dm_exception_table table_swap; + struct dm_exception_store *store_swap; + } u; + + /* + * Swap all snapshot context information between the two instances. + */ + u.table_swap = snap_dest->complete; + snap_dest->complete = snap_src->complete; + snap_src->complete = u.table_swap; + + u.store_swap = snap_dest->store; + snap_dest->store = snap_src->store; + snap_dest->store->userspace_supports_overflow = u.store_swap->userspace_supports_overflow; + snap_src->store = u.store_swap; + + snap_dest->store->snap = snap_dest; + snap_src->store->snap = snap_src; + + snap_dest->ti->max_io_len = snap_dest->store->chunk_size; + snap_dest->valid = snap_src->valid; + snap_dest->snapshot_overflowed = snap_src->snapshot_overflowed; + + /* + * Set source invalid to ensure it receives no further I/O. + */ + snap_src->valid = 0; +} + +static void snapshot_dtr(struct dm_target *ti) +{ +#ifdef CONFIG_DM_DEBUG + int i; +#endif + struct dm_snapshot *s = ti->private; + struct dm_snapshot *snap_src = NULL, *snap_dest = NULL; + + down_read(&_origins_lock); + /* Check whether exception handover must be cancelled */ + (void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL); + if (snap_src && snap_dest && (s == snap_src)) { + down_write(&snap_dest->lock); + snap_dest->valid = 0; + up_write(&snap_dest->lock); + DMERR("Cancelling snapshot handover."); + } + up_read(&_origins_lock); + + if (dm_target_is_snapshot_merge(ti)) + stop_merge(s); + + /* Prevent further origin writes from using this snapshot. */ + /* After this returns there can be no new kcopyd jobs. */ + unregister_snapshot(s); + + while (atomic_read(&s->pending_exceptions_count)) + msleep(1); + /* + * Ensure instructions in mempool_exit aren't reordered + * before atomic_read. + */ + smp_mb(); + +#ifdef CONFIG_DM_DEBUG + for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++) + BUG_ON(!hlist_empty(&s->tracked_chunk_hash[i])); +#endif + + __free_exceptions(s); + + mempool_exit(&s->pending_pool); + + dm_exception_store_destroy(s->store); + + dm_put_device(ti, s->cow); + + dm_put_device(ti, s->origin); + + WARN_ON(s->in_progress); + + kfree(s); +} + +static void account_start_copy(struct dm_snapshot *s) +{ + spin_lock(&s->in_progress_wait.lock); + s->in_progress++; + spin_unlock(&s->in_progress_wait.lock); +} + +static void account_end_copy(struct dm_snapshot *s) +{ + spin_lock(&s->in_progress_wait.lock); + BUG_ON(!s->in_progress); + s->in_progress--; + if (likely(s->in_progress <= cow_threshold) && + unlikely(waitqueue_active(&s->in_progress_wait))) + wake_up_locked(&s->in_progress_wait); + spin_unlock(&s->in_progress_wait.lock); +} + +static bool wait_for_in_progress(struct dm_snapshot *s, bool unlock_origins) +{ + if (unlikely(s->in_progress > cow_threshold)) { + spin_lock(&s->in_progress_wait.lock); + if (likely(s->in_progress > cow_threshold)) { + /* + * NOTE: this throttle doesn't account for whether + * the caller is servicing an IO that will trigger a COW + * so excess throttling may result for chunks not required + * to be COW'd. But if cow_threshold was reached, extra + * throttling is unlikely to negatively impact performance. + */ + DECLARE_WAITQUEUE(wait, current); + __add_wait_queue(&s->in_progress_wait, &wait); + __set_current_state(TASK_UNINTERRUPTIBLE); + spin_unlock(&s->in_progress_wait.lock); + if (unlock_origins) + up_read(&_origins_lock); + io_schedule(); + remove_wait_queue(&s->in_progress_wait, &wait); + return false; + } + spin_unlock(&s->in_progress_wait.lock); + } + return true; +} + +/* + * Flush a list of buffers. + */ +static void flush_bios(struct bio *bio) +{ + struct bio *n; + + while (bio) { + n = bio->bi_next; + bio->bi_next = NULL; + submit_bio_noacct(bio); + bio = n; + } +} + +static int do_origin(struct dm_dev *origin, struct bio *bio, bool limit); + +/* + * Flush a list of buffers. + */ +static void retry_origin_bios(struct dm_snapshot *s, struct bio *bio) +{ + struct bio *n; + int r; + + while (bio) { + n = bio->bi_next; + bio->bi_next = NULL; + r = do_origin(s->origin, bio, false); + if (r == DM_MAPIO_REMAPPED) + submit_bio_noacct(bio); + bio = n; + } +} + +/* + * Error a list of buffers. + */ +static void error_bios(struct bio *bio) +{ + struct bio *n; + + while (bio) { + n = bio->bi_next; + bio->bi_next = NULL; + bio_io_error(bio); + bio = n; + } +} + +static void __invalidate_snapshot(struct dm_snapshot *s, int err) +{ + if (!s->valid) + return; + + if (err == -EIO) + DMERR("Invalidating snapshot: Error reading/writing."); + else if (err == -ENOMEM) + DMERR("Invalidating snapshot: Unable to allocate exception."); + + if (s->store->type->drop_snapshot) + s->store->type->drop_snapshot(s->store); + + s->valid = 0; + + dm_table_event(s->ti->table); +} + +static void invalidate_snapshot(struct dm_snapshot *s, int err) +{ + down_write(&s->lock); + __invalidate_snapshot(s, err); + up_write(&s->lock); +} + +static void pending_complete(void *context, int success) +{ + struct dm_snap_pending_exception *pe = context; + struct dm_exception *e; + struct dm_snapshot *s = pe->snap; + struct bio *origin_bios = NULL; + struct bio *snapshot_bios = NULL; + struct bio *full_bio = NULL; + struct dm_exception_table_lock lock; + int error = 0; + + dm_exception_table_lock_init(s, pe->e.old_chunk, &lock); + + if (!success) { + /* Read/write error - snapshot is unusable */ + invalidate_snapshot(s, -EIO); + error = 1; + + dm_exception_table_lock(&lock); + goto out; + } + + e = alloc_completed_exception(GFP_NOIO); + if (!e) { + invalidate_snapshot(s, -ENOMEM); + error = 1; + + dm_exception_table_lock(&lock); + goto out; + } + *e = pe->e; + + down_read(&s->lock); + dm_exception_table_lock(&lock); + if (!s->valid) { + up_read(&s->lock); + free_completed_exception(e); + error = 1; + + goto out; + } + + /* + * Add a proper exception. After inserting the completed exception all + * subsequent snapshot reads to this chunk will be redirected to the + * COW device. This ensures that we do not starve. Moreover, as long + * as the pending exception exists, neither origin writes nor snapshot + * merging can overwrite the chunk in origin. + */ + dm_insert_exception(&s->complete, e); + up_read(&s->lock); + + /* Wait for conflicting reads to drain */ + if (__chunk_is_tracked(s, pe->e.old_chunk)) { + dm_exception_table_unlock(&lock); + __check_for_conflicting_io(s, pe->e.old_chunk); + dm_exception_table_lock(&lock); + } + +out: + /* Remove the in-flight exception from the list */ + dm_remove_exception(&pe->e); + + dm_exception_table_unlock(&lock); + + snapshot_bios = bio_list_get(&pe->snapshot_bios); + origin_bios = bio_list_get(&pe->origin_bios); + full_bio = pe->full_bio; + if (full_bio) + full_bio->bi_end_io = pe->full_bio_end_io; + increment_pending_exceptions_done_count(); + + /* Submit any pending write bios */ + if (error) { + if (full_bio) + bio_io_error(full_bio); + error_bios(snapshot_bios); + } else { + if (full_bio) + bio_endio(full_bio); + flush_bios(snapshot_bios); + } + + retry_origin_bios(s, origin_bios); + + free_pending_exception(pe); +} + +static void complete_exception(struct dm_snap_pending_exception *pe) +{ + struct dm_snapshot *s = pe->snap; + + /* Update the metadata if we are persistent */ + s->store->type->commit_exception(s->store, &pe->e, !pe->copy_error, + pending_complete, pe); +} + +/* + * Called when the copy I/O has finished. kcopyd actually runs + * this code so don't block. + */ +static void copy_callback(int read_err, unsigned long write_err, void *context) +{ + struct dm_snap_pending_exception *pe = context; + struct dm_snapshot *s = pe->snap; + + pe->copy_error = read_err || write_err; + + if (pe->exception_sequence == s->exception_complete_sequence) { + struct rb_node *next; + + s->exception_complete_sequence++; + complete_exception(pe); + + next = rb_first(&s->out_of_order_tree); + while (next) { + pe = rb_entry(next, struct dm_snap_pending_exception, + out_of_order_node); + if (pe->exception_sequence != s->exception_complete_sequence) + break; + next = rb_next(next); + s->exception_complete_sequence++; + rb_erase(&pe->out_of_order_node, &s->out_of_order_tree); + complete_exception(pe); + cond_resched(); + } + } else { + struct rb_node *parent = NULL; + struct rb_node **p = &s->out_of_order_tree.rb_node; + struct dm_snap_pending_exception *pe2; + + while (*p) { + pe2 = rb_entry(*p, struct dm_snap_pending_exception, out_of_order_node); + parent = *p; + + BUG_ON(pe->exception_sequence == pe2->exception_sequence); + if (pe->exception_sequence < pe2->exception_sequence) + p = &((*p)->rb_left); + else + p = &((*p)->rb_right); + } + + rb_link_node(&pe->out_of_order_node, parent, p); + rb_insert_color(&pe->out_of_order_node, &s->out_of_order_tree); + } + account_end_copy(s); +} + +/* + * Dispatches the copy operation to kcopyd. + */ +static void start_copy(struct dm_snap_pending_exception *pe) +{ + struct dm_snapshot *s = pe->snap; + struct dm_io_region src, dest; + struct block_device *bdev = s->origin->bdev; + sector_t dev_size; + + dev_size = get_dev_size(bdev); + + src.bdev = bdev; + src.sector = chunk_to_sector(s->store, pe->e.old_chunk); + src.count = min((sector_t)s->store->chunk_size, dev_size - src.sector); + + dest.bdev = s->cow->bdev; + dest.sector = chunk_to_sector(s->store, pe->e.new_chunk); + dest.count = src.count; + + /* Hand over to kcopyd */ + account_start_copy(s); + dm_kcopyd_copy(s->kcopyd_client, &src, 1, &dest, 0, copy_callback, pe); +} + +static void full_bio_end_io(struct bio *bio) +{ + void *callback_data = bio->bi_private; + + dm_kcopyd_do_callback(callback_data, 0, bio->bi_status ? 1 : 0); +} + +static void start_full_bio(struct dm_snap_pending_exception *pe, + struct bio *bio) +{ + struct dm_snapshot *s = pe->snap; + void *callback_data; + + pe->full_bio = bio; + pe->full_bio_end_io = bio->bi_end_io; + + account_start_copy(s); + callback_data = dm_kcopyd_prepare_callback(s->kcopyd_client, + copy_callback, pe); + + bio->bi_end_io = full_bio_end_io; + bio->bi_private = callback_data; + + submit_bio_noacct(bio); +} + +static struct dm_snap_pending_exception * +__lookup_pending_exception(struct dm_snapshot *s, chunk_t chunk) +{ + struct dm_exception *e = dm_lookup_exception(&s->pending, chunk); + + if (!e) + return NULL; + + return container_of(e, struct dm_snap_pending_exception, e); +} + +/* + * Inserts a pending exception into the pending table. + * + * NOTE: a write lock must be held on the chunk's pending exception table slot + * before calling this. + */ +static struct dm_snap_pending_exception * +__insert_pending_exception(struct dm_snapshot *s, + struct dm_snap_pending_exception *pe, chunk_t chunk) +{ + pe->e.old_chunk = chunk; + bio_list_init(&pe->origin_bios); + bio_list_init(&pe->snapshot_bios); + pe->started = 0; + pe->full_bio = NULL; + + spin_lock(&s->pe_allocation_lock); + if (s->store->type->prepare_exception(s->store, &pe->e)) { + spin_unlock(&s->pe_allocation_lock); + free_pending_exception(pe); + return NULL; + } + + pe->exception_sequence = s->exception_start_sequence++; + spin_unlock(&s->pe_allocation_lock); + + dm_insert_exception(&s->pending, &pe->e); + + return pe; +} + +/* + * Looks to see if this snapshot already has a pending exception + * for this chunk, otherwise it allocates a new one and inserts + * it into the pending table. + * + * NOTE: a write lock must be held on the chunk's pending exception table slot + * before calling this. + */ +static struct dm_snap_pending_exception * +__find_pending_exception(struct dm_snapshot *s, + struct dm_snap_pending_exception *pe, chunk_t chunk) +{ + struct dm_snap_pending_exception *pe2; + + pe2 = __lookup_pending_exception(s, chunk); + if (pe2) { + free_pending_exception(pe); + return pe2; + } + + return __insert_pending_exception(s, pe, chunk); +} + +static void remap_exception(struct dm_snapshot *s, struct dm_exception *e, + struct bio *bio, chunk_t chunk) +{ + bio_set_dev(bio, s->cow->bdev); + bio->bi_iter.bi_sector = + chunk_to_sector(s->store, dm_chunk_number(e->new_chunk) + + (chunk - e->old_chunk)) + + (bio->bi_iter.bi_sector & s->store->chunk_mask); +} + +static void zero_callback(int read_err, unsigned long write_err, void *context) +{ + struct bio *bio = context; + struct dm_snapshot *s = bio->bi_private; + + account_end_copy(s); + bio->bi_status = write_err ? BLK_STS_IOERR : 0; + bio_endio(bio); +} + +static void zero_exception(struct dm_snapshot *s, struct dm_exception *e, + struct bio *bio, chunk_t chunk) +{ + struct dm_io_region dest; + + dest.bdev = s->cow->bdev; + dest.sector = bio->bi_iter.bi_sector; + dest.count = s->store->chunk_size; + + account_start_copy(s); + WARN_ON_ONCE(bio->bi_private); + bio->bi_private = s; + dm_kcopyd_zero(s->kcopyd_client, 1, &dest, 0, zero_callback, bio); +} + +static bool io_overlaps_chunk(struct dm_snapshot *s, struct bio *bio) +{ + return bio->bi_iter.bi_size == + (s->store->chunk_size << SECTOR_SHIFT); +} + +static int snapshot_map(struct dm_target *ti, struct bio *bio) +{ + struct dm_exception *e; + struct dm_snapshot *s = ti->private; + int r = DM_MAPIO_REMAPPED; + chunk_t chunk; + struct dm_snap_pending_exception *pe = NULL; + struct dm_exception_table_lock lock; + + init_tracked_chunk(bio); + + if (bio->bi_opf & REQ_PREFLUSH) { + bio_set_dev(bio, s->cow->bdev); + return DM_MAPIO_REMAPPED; + } + + chunk = sector_to_chunk(s->store, bio->bi_iter.bi_sector); + dm_exception_table_lock_init(s, chunk, &lock); + + /* Full snapshots are not usable */ + /* To get here the table must be live so s->active is always set. */ + if (!s->valid) + return DM_MAPIO_KILL; + + if (bio_data_dir(bio) == WRITE) { + while (unlikely(!wait_for_in_progress(s, false))) + ; /* wait_for_in_progress() has slept */ + } + + down_read(&s->lock); + dm_exception_table_lock(&lock); + + if (!s->valid || (unlikely(s->snapshot_overflowed) && + bio_data_dir(bio) == WRITE)) { + r = DM_MAPIO_KILL; + goto out_unlock; + } + + if (unlikely(bio_op(bio) == REQ_OP_DISCARD)) { + if (s->discard_passdown_origin && dm_bio_get_target_bio_nr(bio)) { + /* + * passdown discard to origin (without triggering + * snapshot exceptions via do_origin; doing so would + * defeat the goal of freeing space in origin that is + * implied by the "discard_passdown_origin" feature) + */ + bio_set_dev(bio, s->origin->bdev); + track_chunk(s, bio, chunk); + goto out_unlock; + } + /* discard to snapshot (target_bio_nr == 0) zeroes exceptions */ + } + + /* If the block is already remapped - use that, else remap it */ + e = dm_lookup_exception(&s->complete, chunk); + if (e) { + remap_exception(s, e, bio, chunk); + if (unlikely(bio_op(bio) == REQ_OP_DISCARD) && + io_overlaps_chunk(s, bio)) { + dm_exception_table_unlock(&lock); + up_read(&s->lock); + zero_exception(s, e, bio, chunk); + r = DM_MAPIO_SUBMITTED; /* discard is not issued */ + goto out; + } + goto out_unlock; + } + + if (unlikely(bio_op(bio) == REQ_OP_DISCARD)) { + /* + * If no exception exists, complete discard immediately + * otherwise it'll trigger copy-out. + */ + bio_endio(bio); + r = DM_MAPIO_SUBMITTED; + goto out_unlock; + } + + /* + * Write to snapshot - higher level takes care of RW/RO + * flags so we should only get this if we are + * writable. + */ + if (bio_data_dir(bio) == WRITE) { + pe = __lookup_pending_exception(s, chunk); + if (!pe) { + dm_exception_table_unlock(&lock); + pe = alloc_pending_exception(s); + dm_exception_table_lock(&lock); + + e = dm_lookup_exception(&s->complete, chunk); + if (e) { + free_pending_exception(pe); + remap_exception(s, e, bio, chunk); + goto out_unlock; + } + + pe = __find_pending_exception(s, pe, chunk); + if (!pe) { + dm_exception_table_unlock(&lock); + up_read(&s->lock); + + down_write(&s->lock); + + if (s->store->userspace_supports_overflow) { + if (s->valid && !s->snapshot_overflowed) { + s->snapshot_overflowed = 1; + DMERR("Snapshot overflowed: Unable to allocate exception."); + } + } else + __invalidate_snapshot(s, -ENOMEM); + up_write(&s->lock); + + r = DM_MAPIO_KILL; + goto out; + } + } + + remap_exception(s, &pe->e, bio, chunk); + + r = DM_MAPIO_SUBMITTED; + + if (!pe->started && io_overlaps_chunk(s, bio)) { + pe->started = 1; + + dm_exception_table_unlock(&lock); + up_read(&s->lock); + + start_full_bio(pe, bio); + goto out; + } + + bio_list_add(&pe->snapshot_bios, bio); + + if (!pe->started) { + /* this is protected by the exception table lock */ + pe->started = 1; + + dm_exception_table_unlock(&lock); + up_read(&s->lock); + + start_copy(pe); + goto out; + } + } else { + bio_set_dev(bio, s->origin->bdev); + track_chunk(s, bio, chunk); + } + +out_unlock: + dm_exception_table_unlock(&lock); + up_read(&s->lock); +out: + return r; +} + +/* + * A snapshot-merge target behaves like a combination of a snapshot + * target and a snapshot-origin target. It only generates new + * exceptions in other snapshots and not in the one that is being + * merged. + * + * For each chunk, if there is an existing exception, it is used to + * redirect I/O to the cow device. Otherwise I/O is sent to the origin, + * which in turn might generate exceptions in other snapshots. + * If merging is currently taking place on the chunk in question, the + * I/O is deferred by adding it to s->bios_queued_during_merge. + */ +static int snapshot_merge_map(struct dm_target *ti, struct bio *bio) +{ + struct dm_exception *e; + struct dm_snapshot *s = ti->private; + int r = DM_MAPIO_REMAPPED; + chunk_t chunk; + + init_tracked_chunk(bio); + + if (bio->bi_opf & REQ_PREFLUSH) { + if (!dm_bio_get_target_bio_nr(bio)) + bio_set_dev(bio, s->origin->bdev); + else + bio_set_dev(bio, s->cow->bdev); + return DM_MAPIO_REMAPPED; + } + + if (unlikely(bio_op(bio) == REQ_OP_DISCARD)) { + /* Once merging, discards no longer effect change */ + bio_endio(bio); + return DM_MAPIO_SUBMITTED; + } + + chunk = sector_to_chunk(s->store, bio->bi_iter.bi_sector); + + down_write(&s->lock); + + /* Full merging snapshots are redirected to the origin */ + if (!s->valid) + goto redirect_to_origin; + + /* If the block is already remapped - use that */ + e = dm_lookup_exception(&s->complete, chunk); + if (e) { + /* Queue writes overlapping with chunks being merged */ + if (bio_data_dir(bio) == WRITE && + chunk >= s->first_merging_chunk && + chunk < (s->first_merging_chunk + + s->num_merging_chunks)) { + bio_set_dev(bio, s->origin->bdev); + bio_list_add(&s->bios_queued_during_merge, bio); + r = DM_MAPIO_SUBMITTED; + goto out_unlock; + } + + remap_exception(s, e, bio, chunk); + + if (bio_data_dir(bio) == WRITE) + track_chunk(s, bio, chunk); + goto out_unlock; + } + +redirect_to_origin: + bio_set_dev(bio, s->origin->bdev); + + if (bio_data_dir(bio) == WRITE) { + up_write(&s->lock); + return do_origin(s->origin, bio, false); + } + +out_unlock: + up_write(&s->lock); + + return r; +} + +static int snapshot_end_io(struct dm_target *ti, struct bio *bio, + blk_status_t *error) +{ + struct dm_snapshot *s = ti->private; + + if (is_bio_tracked(bio)) + stop_tracking_chunk(s, bio); + + return DM_ENDIO_DONE; +} + +static void snapshot_merge_presuspend(struct dm_target *ti) +{ + struct dm_snapshot *s = ti->private; + + stop_merge(s); +} + +static int snapshot_preresume(struct dm_target *ti) +{ + int r = 0; + struct dm_snapshot *s = ti->private; + struct dm_snapshot *snap_src = NULL, *snap_dest = NULL; + + down_read(&_origins_lock); + (void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL); + if (snap_src && snap_dest) { + down_read(&snap_src->lock); + if (s == snap_src) { + DMERR("Unable to resume snapshot source until handover completes."); + r = -EINVAL; + } else if (!dm_suspended(snap_src->ti)) { + DMERR("Unable to perform snapshot handover until source is suspended."); + r = -EINVAL; + } + up_read(&snap_src->lock); + } + up_read(&_origins_lock); + + return r; +} + +static void snapshot_resume(struct dm_target *ti) +{ + struct dm_snapshot *s = ti->private; + struct dm_snapshot *snap_src = NULL, *snap_dest = NULL, *snap_merging = NULL; + struct dm_origin *o; + struct mapped_device *origin_md = NULL; + bool must_restart_merging = false; + + down_read(&_origins_lock); + + o = __lookup_dm_origin(s->origin->bdev); + if (o) + origin_md = dm_table_get_md(o->ti->table); + if (!origin_md) { + (void) __find_snapshots_sharing_cow(s, NULL, NULL, &snap_merging); + if (snap_merging) + origin_md = dm_table_get_md(snap_merging->ti->table); + } + if (origin_md == dm_table_get_md(ti->table)) + origin_md = NULL; + if (origin_md) { + if (dm_hold(origin_md)) + origin_md = NULL; + } + + up_read(&_origins_lock); + + if (origin_md) { + dm_internal_suspend_fast(origin_md); + if (snap_merging && test_bit(RUNNING_MERGE, &snap_merging->state_bits)) { + must_restart_merging = true; + stop_merge(snap_merging); + } + } + + down_read(&_origins_lock); + + (void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL); + if (snap_src && snap_dest) { + down_write(&snap_src->lock); + down_write_nested(&snap_dest->lock, SINGLE_DEPTH_NESTING); + __handover_exceptions(snap_src, snap_dest); + up_write(&snap_dest->lock); + up_write(&snap_src->lock); + } + + up_read(&_origins_lock); + + if (origin_md) { + if (must_restart_merging) + start_merge(snap_merging); + dm_internal_resume_fast(origin_md); + dm_put(origin_md); + } + + /* Now we have correct chunk size, reregister */ + reregister_snapshot(s); + + down_write(&s->lock); + s->active = 1; + up_write(&s->lock); +} + +static uint32_t get_origin_minimum_chunksize(struct block_device *bdev) +{ + uint32_t min_chunksize; + + down_read(&_origins_lock); + min_chunksize = __minimum_chunk_size(__lookup_origin(bdev)); + up_read(&_origins_lock); + + return min_chunksize; +} + +static void snapshot_merge_resume(struct dm_target *ti) +{ + struct dm_snapshot *s = ti->private; + + /* + * Handover exceptions from existing snapshot. + */ + snapshot_resume(ti); + + /* + * snapshot-merge acts as an origin, so set ti->max_io_len + */ + ti->max_io_len = get_origin_minimum_chunksize(s->origin->bdev); + + start_merge(s); +} + +static void snapshot_status(struct dm_target *ti, status_type_t type, + unsigned int status_flags, char *result, unsigned int maxlen) +{ + unsigned int sz = 0; + struct dm_snapshot *snap = ti->private; + unsigned int num_features; + + switch (type) { + case STATUSTYPE_INFO: + + down_write(&snap->lock); + + if (!snap->valid) + DMEMIT("Invalid"); + else if (snap->merge_failed) + DMEMIT("Merge failed"); + else if (snap->snapshot_overflowed) + DMEMIT("Overflow"); + else { + if (snap->store->type->usage) { + sector_t total_sectors, sectors_allocated, + metadata_sectors; + snap->store->type->usage(snap->store, + &total_sectors, + §ors_allocated, + &metadata_sectors); + DMEMIT("%llu/%llu %llu", + (unsigned long long)sectors_allocated, + (unsigned long long)total_sectors, + (unsigned long long)metadata_sectors); + } + else + DMEMIT("Unknown"); + } + + up_write(&snap->lock); + + break; + + case STATUSTYPE_TABLE: + /* + * kdevname returns a static pointer so we need + * to make private copies if the output is to + * make sense. + */ + DMEMIT("%s %s", snap->origin->name, snap->cow->name); + sz += snap->store->type->status(snap->store, type, result + sz, + maxlen - sz); + num_features = snap->discard_zeroes_cow + snap->discard_passdown_origin; + if (num_features) { + DMEMIT(" %u", num_features); + if (snap->discard_zeroes_cow) + DMEMIT(" discard_zeroes_cow"); + if (snap->discard_passdown_origin) + DMEMIT(" discard_passdown_origin"); + } + break; + + case STATUSTYPE_IMA: + DMEMIT_TARGET_NAME_VERSION(ti->type); + DMEMIT(",snap_origin_name=%s", snap->origin->name); + DMEMIT(",snap_cow_name=%s", snap->cow->name); + DMEMIT(",snap_valid=%c", snap->valid ? 'y' : 'n'); + DMEMIT(",snap_merge_failed=%c", snap->merge_failed ? 'y' : 'n'); + DMEMIT(",snapshot_overflowed=%c", snap->snapshot_overflowed ? 'y' : 'n'); + DMEMIT(";"); + break; + } +} + +static int snapshot_iterate_devices(struct dm_target *ti, + iterate_devices_callout_fn fn, void *data) +{ + struct dm_snapshot *snap = ti->private; + int r; + + r = fn(ti, snap->origin, 0, ti->len, data); + + if (!r) + r = fn(ti, snap->cow, 0, get_dev_size(snap->cow->bdev), data); + + return r; +} + +static void snapshot_io_hints(struct dm_target *ti, struct queue_limits *limits) +{ + struct dm_snapshot *snap = ti->private; + + if (snap->discard_zeroes_cow) { + struct dm_snapshot *snap_src = NULL, *snap_dest = NULL; + + down_read(&_origins_lock); + + (void) __find_snapshots_sharing_cow(snap, &snap_src, &snap_dest, NULL); + if (snap_src && snap_dest) + snap = snap_src; + + /* All discards are split on chunk_size boundary */ + limits->discard_granularity = snap->store->chunk_size; + limits->max_discard_sectors = snap->store->chunk_size; + + up_read(&_origins_lock); + } +} + +/*----------------------------------------------------------------- + * Origin methods + *---------------------------------------------------------------*/ + +/* + * If no exceptions need creating, DM_MAPIO_REMAPPED is returned and any + * supplied bio was ignored. The caller may submit it immediately. + * (No remapping actually occurs as the origin is always a direct linear + * map.) + * + * If further exceptions are required, DM_MAPIO_SUBMITTED is returned + * and any supplied bio is added to a list to be submitted once all + * the necessary exceptions exist. + */ +static int __origin_write(struct list_head *snapshots, sector_t sector, + struct bio *bio) +{ + int r = DM_MAPIO_REMAPPED; + struct dm_snapshot *snap; + struct dm_exception *e; + struct dm_snap_pending_exception *pe, *pe2; + struct dm_snap_pending_exception *pe_to_start_now = NULL; + struct dm_snap_pending_exception *pe_to_start_last = NULL; + struct dm_exception_table_lock lock; + chunk_t chunk; + + /* Do all the snapshots on this origin */ + list_for_each_entry(snap, snapshots, list) { + /* + * Don't make new exceptions in a merging snapshot + * because it has effectively been deleted + */ + if (dm_target_is_snapshot_merge(snap->ti)) + continue; + + /* Nothing to do if writing beyond end of snapshot */ + if (sector >= dm_table_get_size(snap->ti->table)) + continue; + + /* + * Remember, different snapshots can have + * different chunk sizes. + */ + chunk = sector_to_chunk(snap->store, sector); + dm_exception_table_lock_init(snap, chunk, &lock); + + down_read(&snap->lock); + dm_exception_table_lock(&lock); + + /* Only deal with valid and active snapshots */ + if (!snap->valid || !snap->active) + goto next_snapshot; + + pe = __lookup_pending_exception(snap, chunk); + if (!pe) { + /* + * Check exception table to see if block is already + * remapped in this snapshot and trigger an exception + * if not. + */ + e = dm_lookup_exception(&snap->complete, chunk); + if (e) + goto next_snapshot; + + dm_exception_table_unlock(&lock); + pe = alloc_pending_exception(snap); + dm_exception_table_lock(&lock); + + pe2 = __lookup_pending_exception(snap, chunk); + + if (!pe2) { + e = dm_lookup_exception(&snap->complete, chunk); + if (e) { + free_pending_exception(pe); + goto next_snapshot; + } + + pe = __insert_pending_exception(snap, pe, chunk); + if (!pe) { + dm_exception_table_unlock(&lock); + up_read(&snap->lock); + + invalidate_snapshot(snap, -ENOMEM); + continue; + } + } else { + free_pending_exception(pe); + pe = pe2; + } + } + + r = DM_MAPIO_SUBMITTED; + + /* + * If an origin bio was supplied, queue it to wait for the + * completion of this exception, and start this one last, + * at the end of the function. + */ + if (bio) { + bio_list_add(&pe->origin_bios, bio); + bio = NULL; + + if (!pe->started) { + pe->started = 1; + pe_to_start_last = pe; + } + } + + if (!pe->started) { + pe->started = 1; + pe_to_start_now = pe; + } + +next_snapshot: + dm_exception_table_unlock(&lock); + up_read(&snap->lock); + + if (pe_to_start_now) { + start_copy(pe_to_start_now); + pe_to_start_now = NULL; + } + } + + /* + * Submit the exception against which the bio is queued last, + * to give the other exceptions a head start. + */ + if (pe_to_start_last) + start_copy(pe_to_start_last); + + return r; +} + +/* + * Called on a write from the origin driver. + */ +static int do_origin(struct dm_dev *origin, struct bio *bio, bool limit) +{ + struct origin *o; + int r = DM_MAPIO_REMAPPED; + +again: + down_read(&_origins_lock); + o = __lookup_origin(origin->bdev); + if (o) { + if (limit) { + struct dm_snapshot *s; + list_for_each_entry(s, &o->snapshots, list) + if (unlikely(!wait_for_in_progress(s, true))) + goto again; + } + + r = __origin_write(&o->snapshots, bio->bi_iter.bi_sector, bio); + } + up_read(&_origins_lock); + + return r; +} + +/* + * Trigger exceptions in all non-merging snapshots. + * + * The chunk size of the merging snapshot may be larger than the chunk + * size of some other snapshot so we may need to reallocate multiple + * chunks in other snapshots. + * + * We scan all the overlapping exceptions in the other snapshots. + * Returns 1 if anything was reallocated and must be waited for, + * otherwise returns 0. + * + * size must be a multiple of merging_snap's chunk_size. + */ +static int origin_write_extent(struct dm_snapshot *merging_snap, + sector_t sector, unsigned int size) +{ + int must_wait = 0; + sector_t n; + struct origin *o; + + /* + * The origin's __minimum_chunk_size() got stored in max_io_len + * by snapshot_merge_resume(). + */ + down_read(&_origins_lock); + o = __lookup_origin(merging_snap->origin->bdev); + for (n = 0; n < size; n += merging_snap->ti->max_io_len) + if (__origin_write(&o->snapshots, sector + n, NULL) == + DM_MAPIO_SUBMITTED) + must_wait = 1; + up_read(&_origins_lock); + + return must_wait; +} + +/* + * Origin: maps a linear range of a device, with hooks for snapshotting. + */ + +/* + * Construct an origin mapping: <dev_path> + * The context for an origin is merely a 'struct dm_dev *' + * pointing to the real device. + */ +static int origin_ctr(struct dm_target *ti, unsigned int argc, char **argv) +{ + int r; + struct dm_origin *o; + + if (argc != 1) { + ti->error = "origin: incorrect number of arguments"; + return -EINVAL; + } + + o = kmalloc(sizeof(struct dm_origin), GFP_KERNEL); + if (!o) { + ti->error = "Cannot allocate private origin structure"; + r = -ENOMEM; + goto bad_alloc; + } + + r = dm_get_device(ti, argv[0], dm_table_get_mode(ti->table), &o->dev); + if (r) { + ti->error = "Cannot get target device"; + goto bad_open; + } + + o->ti = ti; + ti->private = o; + ti->num_flush_bios = 1; + + return 0; + +bad_open: + kfree(o); +bad_alloc: + return r; +} + +static void origin_dtr(struct dm_target *ti) +{ + struct dm_origin *o = ti->private; + + dm_put_device(ti, o->dev); + kfree(o); +} + +static int origin_map(struct dm_target *ti, struct bio *bio) +{ + struct dm_origin *o = ti->private; + unsigned int available_sectors; + + bio_set_dev(bio, o->dev->bdev); + + if (unlikely(bio->bi_opf & REQ_PREFLUSH)) + return DM_MAPIO_REMAPPED; + + if (bio_data_dir(bio) != WRITE) + return DM_MAPIO_REMAPPED; + + available_sectors = o->split_boundary - + ((unsigned int)bio->bi_iter.bi_sector & (o->split_boundary - 1)); + + if (bio_sectors(bio) > available_sectors) + dm_accept_partial_bio(bio, available_sectors); + + /* Only tell snapshots if this is a write */ + return do_origin(o->dev, bio, true); +} + +/* + * Set the target "max_io_len" field to the minimum of all the snapshots' + * chunk sizes. + */ +static void origin_resume(struct dm_target *ti) +{ + struct dm_origin *o = ti->private; + + o->split_boundary = get_origin_minimum_chunksize(o->dev->bdev); + + down_write(&_origins_lock); + __insert_dm_origin(o); + up_write(&_origins_lock); +} + +static void origin_postsuspend(struct dm_target *ti) +{ + struct dm_origin *o = ti->private; + + down_write(&_origins_lock); + __remove_dm_origin(o); + up_write(&_origins_lock); +} + +static void origin_status(struct dm_target *ti, status_type_t type, + unsigned int status_flags, char *result, unsigned int maxlen) +{ + struct dm_origin *o = ti->private; + + switch (type) { + case STATUSTYPE_INFO: + result[0] = '\0'; + break; + + case STATUSTYPE_TABLE: + snprintf(result, maxlen, "%s", o->dev->name); + break; + case STATUSTYPE_IMA: + result[0] = '\0'; + break; + } +} + +static int origin_iterate_devices(struct dm_target *ti, + iterate_devices_callout_fn fn, void *data) +{ + struct dm_origin *o = ti->private; + + return fn(ti, o->dev, 0, ti->len, data); +} + +static struct target_type origin_target = { + .name = "snapshot-origin", + .version = {1, 9, 0}, + .module = THIS_MODULE, + .ctr = origin_ctr, + .dtr = origin_dtr, + .map = origin_map, + .resume = origin_resume, + .postsuspend = origin_postsuspend, + .status = origin_status, + .iterate_devices = origin_iterate_devices, +}; + +static struct target_type snapshot_target = { + .name = "snapshot", + .version = {1, 16, 0}, + .module = THIS_MODULE, + .ctr = snapshot_ctr, + .dtr = snapshot_dtr, + .map = snapshot_map, + .end_io = snapshot_end_io, + .preresume = snapshot_preresume, + .resume = snapshot_resume, + .status = snapshot_status, + .iterate_devices = snapshot_iterate_devices, + .io_hints = snapshot_io_hints, +}; + +static struct target_type merge_target = { + .name = dm_snapshot_merge_target_name, + .version = {1, 5, 0}, + .module = THIS_MODULE, + .ctr = snapshot_ctr, + .dtr = snapshot_dtr, + .map = snapshot_merge_map, + .end_io = snapshot_end_io, + .presuspend = snapshot_merge_presuspend, + .preresume = snapshot_preresume, + .resume = snapshot_merge_resume, + .status = snapshot_status, + .iterate_devices = snapshot_iterate_devices, + .io_hints = snapshot_io_hints, +}; + +static int __init dm_snapshot_init(void) +{ + int r; + + r = dm_exception_store_init(); + if (r) { + DMERR("Failed to initialize exception stores"); + return r; + } + + r = init_origin_hash(); + if (r) { + DMERR("init_origin_hash failed."); + goto bad_origin_hash; + } + + exception_cache = KMEM_CACHE(dm_exception, 0); + if (!exception_cache) { + DMERR("Couldn't create exception cache."); + r = -ENOMEM; + goto bad_exception_cache; + } + + pending_cache = KMEM_CACHE(dm_snap_pending_exception, 0); + if (!pending_cache) { + DMERR("Couldn't create pending cache."); + r = -ENOMEM; + goto bad_pending_cache; + } + + r = dm_register_target(&snapshot_target); + if (r < 0) { + DMERR("snapshot target register failed %d", r); + goto bad_register_snapshot_target; + } + + r = dm_register_target(&origin_target); + if (r < 0) { + DMERR("Origin target register failed %d", r); + goto bad_register_origin_target; + } + + r = dm_register_target(&merge_target); + if (r < 0) { + DMERR("Merge target register failed %d", r); + goto bad_register_merge_target; + } + + return 0; + +bad_register_merge_target: + dm_unregister_target(&origin_target); +bad_register_origin_target: + dm_unregister_target(&snapshot_target); +bad_register_snapshot_target: + kmem_cache_destroy(pending_cache); +bad_pending_cache: + kmem_cache_destroy(exception_cache); +bad_exception_cache: + exit_origin_hash(); +bad_origin_hash: + dm_exception_store_exit(); + + return r; +} + +static void __exit dm_snapshot_exit(void) +{ + dm_unregister_target(&snapshot_target); + dm_unregister_target(&origin_target); + dm_unregister_target(&merge_target); + + exit_origin_hash(); + kmem_cache_destroy(pending_cache); + kmem_cache_destroy(exception_cache); + + dm_exception_store_exit(); +} + +/* Module hooks */ +module_init(dm_snapshot_init); +module_exit(dm_snapshot_exit); + +MODULE_DESCRIPTION(DM_NAME " snapshot target"); +MODULE_AUTHOR("Joe Thornber"); +MODULE_LICENSE("GPL"); +MODULE_ALIAS("dm-snapshot-origin"); +MODULE_ALIAS("dm-snapshot-merge"); |