v4.19.13 snapshot.
diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
new file mode 100644
index 0000000..ae4b33d
--- /dev/null
+++ b/drivers/md/dm-snap.c
@@ -0,0 +1,2504 @@
+/*
+ * dm-snapshot.c
+ *
+ * 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/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 hash_shift;
+ struct list_head *table;
+};
+
+struct dm_snapshot {
+ struct mutex 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;
+
+ /* Protected by "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;
+
+ 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.
+ */
+ int merge_failed;
+
+ /*
+ * 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
+
+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 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 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;
+
+ mutex_lock(&s->lock);
+ active = s->active;
+ mutex_unlock(&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 int dm_exception_table_init(struct dm_exception_table *et,
+ uint32_t size, unsigned hash_shift)
+{
+ unsigned int i;
+
+ et->hash_shift = hash_shift;
+ et->hash_mask = size - 1;
+ et->table = dm_vcalloc(size, sizeof(struct list_head));
+ if (!et->table)
+ return -ENOMEM;
+
+ for (i = 0; i < size; i++)
+ INIT_LIST_HEAD(et->table + i);
+
+ return 0;
+}
+
+static void dm_exception_table_exit(struct dm_exception_table *et,
+ struct kmem_cache *mem)
+{
+ struct list_head *slot;
+ struct dm_exception *ex, *next;
+ int i, size;
+
+ size = et->hash_mask + 1;
+ for (i = 0; i < size; i++) {
+ slot = et->table + i;
+
+ list_for_each_entry_safe (ex, next, slot, hash_list)
+ kmem_cache_free(mem, ex);
+ }
+
+ vfree(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)
+{
+ list_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 list_head *slot;
+ struct dm_exception *e;
+
+ slot = &et->table[exception_hash(et, chunk)];
+ list_for_each_entry (e, 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 list_head *l;
+ 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 */
+ list_for_each_entry_reverse(e, 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:
+ list_add(&new_e->hash_list, e ? &e->hash_list : l);
+}
+
+/*
+ * 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_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;
+
+ dm_insert_exception(&s->complete, e);
+
+ 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 chunk_size = 0;
+
+ 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 list_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;
+
+ mutex_lock(&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:
+ mutex_unlock(&s->lock);
+ if (b)
+ flush_bios(b);
+
+ return r;
+}
+
+static int origin_write_extent(struct dm_snapshot *merging_snap,
+ sector_t sector, unsigned 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");
+ mutex_lock(&s->lock);
+ s->merge_failed = 1;
+ mutex_unlock(&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();
+ }
+
+ mutex_lock(&s->lock);
+ s->first_merging_chunk = old_chunk;
+ s->num_merging_chunks = linear_chunks;
+ mutex_unlock(&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 (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:
+ mutex_lock(&s->lock);
+ s->merge_failed = 1;
+ b = __release_queued_bios_after_merge(s);
+ mutex_unlock(&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);
+}
+
+/*
+ * Construct a snapshot mapping: <origin_dev> <COW-dev> <p|po|n> <chunk-size>
+ */
+static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
+{
+ struct dm_snapshot *s;
+ int i;
+ int r = -EINVAL;
+ char *origin_path, *cow_path;
+ dev_t origin_dev, cow_dev;
+ unsigned args_used, num_flush_bios = 1;
+ fmode_t origin_mode = FMODE_READ;
+
+ if (argc != 4) {
+ ti->error = "requires exactly 4 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;
+ }
+
+ 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);
+ s->exception_start_sequence = 0;
+ s->exception_complete_sequence = 0;
+ s->out_of_order_tree = RB_ROOT;
+ mutex_init(&s->lock);
+ INIT_LIST_HEAD(&s->list);
+ spin_lock_init(&s->pe_lock);
+ s->state_bits = 0;
+ s->merge_failed = 0;
+ 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;
+ }
+
+ 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;
+ 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";
+ 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:
+ 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)) {
+ mutex_lock(&snap_dest->lock);
+ snap_dest->valid = 0;
+ mutex_unlock(&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);
+
+ mutex_destroy(&s->lock);
+
+ dm_put_device(ti, s->cow);
+
+ dm_put_device(ti, s->origin);
+
+ kfree(s);
+}
+
+/*
+ * 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;
+ generic_make_request(bio);
+ bio = n;
+ }
+}
+
+static int do_origin(struct dm_dev *origin, struct bio *bio);
+
+/*
+ * 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);
+ if (r == DM_MAPIO_REMAPPED)
+ generic_make_request(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 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;
+ int error = 0;
+
+ if (!success) {
+ /* Read/write error - snapshot is unusable */
+ mutex_lock(&s->lock);
+ __invalidate_snapshot(s, -EIO);
+ error = 1;
+ goto out;
+ }
+
+ e = alloc_completed_exception(GFP_NOIO);
+ if (!e) {
+ mutex_lock(&s->lock);
+ __invalidate_snapshot(s, -ENOMEM);
+ error = 1;
+ goto out;
+ }
+ *e = pe->e;
+
+ mutex_lock(&s->lock);
+ if (!s->valid) {
+ free_completed_exception(e);
+ error = 1;
+ goto out;
+ }
+
+ /* Check for conflicting reads */
+ __check_for_conflicting_io(s, pe->e.old_chunk);
+
+ /*
+ * Add a proper exception, and remove the
+ * in-flight exception from the list.
+ */
+ dm_insert_exception(&s->complete, e);
+
+out:
+ dm_remove_exception(&pe->e);
+ 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();
+
+ mutex_unlock(&s->lock);
+
+ /* 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);
+ }
+}
+
+/*
+ * 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 */
+ 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;
+
+ 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;
+
+ generic_make_request(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);
+}
+
+/*
+ * 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 snap->lock 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;
+ }
+
+ pe->e.old_chunk = chunk;
+ bio_list_init(&pe->origin_bios);
+ bio_list_init(&pe->snapshot_bios);
+ pe->started = 0;
+ pe->full_bio = NULL;
+
+ if (s->store->type->prepare_exception(s->store, &pe->e)) {
+ free_pending_exception(pe);
+ return NULL;
+ }
+
+ pe->exception_sequence = s->exception_start_sequence++;
+
+ dm_insert_exception(&s->pending, &pe->e);
+
+ return pe;
+}
+
+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 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;
+
+ 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);
+
+ /* 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;
+
+ mutex_lock(&s->lock);
+
+ if (!s->valid || (unlikely(s->snapshot_overflowed) &&
+ bio_data_dir(bio) == WRITE)) {
+ r = DM_MAPIO_KILL;
+ goto out_unlock;
+ }
+
+ /* 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);
+ goto out_unlock;
+ }
+
+ /*
+ * Write to snapshot - higher level takes care of RW/RO
+ * flags so we should only get this if we are
+ * writeable.
+ */
+ if (bio_data_dir(bio) == WRITE) {
+ pe = __lookup_pending_exception(s, chunk);
+ if (!pe) {
+ mutex_unlock(&s->lock);
+ pe = alloc_pending_exception(s);
+ mutex_lock(&s->lock);
+
+ if (!s->valid || s->snapshot_overflowed) {
+ free_pending_exception(pe);
+ r = DM_MAPIO_KILL;
+ goto out_unlock;
+ }
+
+ 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) {
+ if (s->store->userspace_supports_overflow) {
+ s->snapshot_overflowed = 1;
+ DMERR("Snapshot overflowed: Unable to allocate exception.");
+ } else
+ __invalidate_snapshot(s, -ENOMEM);
+ r = DM_MAPIO_KILL;
+ goto out_unlock;
+ }
+ }
+
+ remap_exception(s, &pe->e, bio, chunk);
+
+ r = DM_MAPIO_SUBMITTED;
+
+ if (!pe->started &&
+ bio->bi_iter.bi_size ==
+ (s->store->chunk_size << SECTOR_SHIFT)) {
+ pe->started = 1;
+ mutex_unlock(&s->lock);
+ start_full_bio(pe, bio);
+ goto out;
+ }
+
+ bio_list_add(&pe->snapshot_bios, bio);
+
+ if (!pe->started) {
+ /* this is protected by snap->lock */
+ pe->started = 1;
+ mutex_unlock(&s->lock);
+ start_copy(pe);
+ goto out;
+ }
+ } else {
+ bio_set_dev(bio, s->origin->bdev);
+ track_chunk(s, bio, chunk);
+ }
+
+out_unlock:
+ mutex_unlock(&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;
+ }
+
+ chunk = sector_to_chunk(s->store, bio->bi_iter.bi_sector);
+
+ mutex_lock(&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) {
+ mutex_unlock(&s->lock);
+ return do_origin(s->origin, bio);
+ }
+
+out_unlock:
+ mutex_unlock(&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) {
+ mutex_lock(&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;
+ }
+ mutex_unlock(&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) {
+ mutex_lock(&snap_src->lock);
+ mutex_lock_nested(&snap_dest->lock, SINGLE_DEPTH_NESTING);
+ __handover_exceptions(snap_src, snap_dest);
+ mutex_unlock(&snap_dest->lock);
+ mutex_unlock(&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);
+
+ mutex_lock(&s->lock);
+ s->active = 1;
+ mutex_unlock(&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 status_flags, char *result, unsigned maxlen)
+{
+ unsigned sz = 0;
+ struct dm_snapshot *snap = ti->private;
+
+ switch (type) {
+ case STATUSTYPE_INFO:
+
+ mutex_lock(&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");
+ }
+
+ mutex_unlock(&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);
+ snap->store->type->status(snap->store, type, result + sz,
+ maxlen - sz);
+ 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;
+}
+
+
+/*-----------------------------------------------------------------
+ * 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;
+ struct dm_snap_pending_exception *pe_to_start_now = NULL;
+ struct dm_snap_pending_exception *pe_to_start_last = NULL;
+ 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;
+
+ mutex_lock(&snap->lock);
+
+ /* Only deal with valid and active snapshots */
+ if (!snap->valid || !snap->active)
+ goto next_snapshot;
+
+ /* Nothing to do if writing beyond end of snapshot */
+ if (sector >= dm_table_get_size(snap->ti->table))
+ goto next_snapshot;
+
+ /*
+ * Remember, different snapshots can have
+ * different chunk sizes.
+ */
+ chunk = sector_to_chunk(snap->store, sector);
+
+ /*
+ * 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;
+
+ pe = __lookup_pending_exception(snap, chunk);
+ if (!pe) {
+ mutex_unlock(&snap->lock);
+ pe = alloc_pending_exception(snap);
+ mutex_lock(&snap->lock);
+
+ if (!snap->valid) {
+ free_pending_exception(pe);
+ goto next_snapshot;
+ }
+
+ e = dm_lookup_exception(&snap->complete, chunk);
+ if (e) {
+ free_pending_exception(pe);
+ goto next_snapshot;
+ }
+
+ pe = __find_pending_exception(snap, pe, chunk);
+ if (!pe) {
+ __invalidate_snapshot(snap, -ENOMEM);
+ goto next_snapshot;
+ }
+ }
+
+ 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:
+ mutex_unlock(&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)
+{
+ struct origin *o;
+ int r = DM_MAPIO_REMAPPED;
+
+ down_read(&_origins_lock);
+ o = __lookup_origin(origin->bdev);
+ if (o)
+ 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 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 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)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);
+}
+
+static long origin_dax_direct_access(struct dm_target *ti, pgoff_t pgoff,
+ long nr_pages, void **kaddr, pfn_t *pfn)
+{
+ DMWARN("device does not support dax.");
+ return -EIO;
+}
+
+/*
+ * 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 status_flags, char *result, unsigned 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;
+ }
+}
+
+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,
+ .direct_access = origin_dax_direct_access,
+};
+
+static struct target_type snapshot_target = {
+ .name = "snapshot",
+ .version = {1, 15, 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,
+};
+
+static struct target_type merge_target = {
+ .name = dm_snapshot_merge_target_name,
+ .version = {1, 4, 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,
+};
+
+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");