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;
/* Origin writes don't trigger exceptions until this is set */
int active;
+ /* Whether or not owning mapped_device is suspended */
+ int suspended;
+
mempool_t *pending_pool;
atomic_t pending_exceptions_count;
struct hlist_head tracked_chunk_hash[DM_TRACKED_CHUNK_HASH_SIZE];
};
+struct dm_dev *dm_snap_cow(struct dm_snapshot *s)
+{
+ return s->cow;
+}
+EXPORT_SYMBOL(dm_snap_cow);
+
static struct workqueue_struct *ksnapd;
static void flush_queued_bios(struct work_struct *work);
list_add_tail(&o->hash_list, sl);
}
+/*
+ * _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.
+ *
+ * Possible return values and states:
+ * 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 *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 (!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;
+
+ /* Does snapshot need exceptions handed over to it? */
+ if ((__find_snapshots_sharing_cow(snap, &snap_src, &snap_dest) == 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;
+
+ 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 dm_snapshot *l;
- struct origin *o, *new_o;
+ 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);
- o = __lookup_origin(bdev);
+ r = __validate_exception_handover(snap);
+ if (r < 0) {
+ kfree(new_o);
+ goto out;
+ }
+
+ o = __lookup_origin(bdev);
if (o)
kfree(new_o);
else {
__insert_origin(o);
}
- /* Sort the list according to chunk size, largest-first smallest-last */
- list_for_each_entry(l, &o->snapshots, list)
- if (l->store->chunk_size < snap->store->chunk_size)
- break;
- list_add_tail(&snap->list, &l->list);
+ __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);
- return 0;
}
static void unregister_snapshot(struct dm_snapshot *s)
o = __lookup_origin(s->origin->bdev);
list_del(&s->list);
- if (list_empty(&o->snapshots)) {
+ if (o && list_empty(&o->snapshots)) {
list_del(&o->hash_list);
kfree(o);
}
* Calculate based on the size of the original volume or
* the COW volume...
*/
- cow_dev_size = get_dev_size(s->store->cow->bdev);
+ cow_dev_size = get_dev_size(s->cow->bdev);
origin_dev_size = get_dev_size(s->origin->bdev);
max_buckets = calc_max_buckets();
struct dm_snapshot *s;
int i;
int r = -EINVAL;
- char *origin_path;
- struct dm_exception_store *store;
+ char *origin_path, *cow_path;
unsigned args_used;
if (argc != 4) {
ti->error = "requires exactly 4 arguments";
r = -EINVAL;
- goto bad_args;
+ goto bad;
}
origin_path = argv[0];
argv++;
argc--;
- r = dm_exception_store_create(ti, argc, argv, &args_used, &store);
+ s = kmalloc(sizeof(*s), GFP_KERNEL);
+ if (!s) {
+ ti->error = "Cannot allocate snapshot context private "
+ "structure";
+ r = -ENOMEM;
+ goto bad;
+ }
+
+ cow_path = argv[0];
+ argv++;
+ argc--;
+
+ r = dm_get_device(ti, cow_path, 0, 0,
+ FMODE_READ | FMODE_WRITE, &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_args;
+ goto bad_store;
}
argv += args_used;
argc -= args_used;
- s = kmalloc(sizeof(*s), GFP_KERNEL);
- if (!s) {
- ti->error = "Cannot allocate snapshot context private "
- "structure";
- r = -ENOMEM;
- goto bad_snap;
- }
-
r = dm_get_device(ti, origin_path, 0, ti->len, FMODE_READ, &s->origin);
if (r) {
ti->error = "Cannot get origin device";
goto bad_origin;
}
- s->store = store;
+ s->ti = ti;
s->valid = 1;
s->active = 0;
+ s->suspended = 0;
atomic_set(&s->pending_exceptions_count, 0);
init_rwsem(&s->lock);
+ INIT_LIST_HEAD(&s->list);
spin_lock_init(&s->pe_lock);
/* Allocate hash table for COW data */
spin_lock_init(&s->tracked_chunk_lock);
- /* Metadata must only be loaded into one table at once */
+ bio_list_init(&s->queued_bios);
+ INIT_WORK(&s->queued_bios_work, flush_queued_bios);
+
+ ti->private = s;
+ ti->num_flush_requests = 1;
+
+ /* 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_load_and_register;
+ goto bad_read_metadata;
} else if (r > 0) {
s->valid = 0;
DMWARN("Snapshot is marked invalid.");
}
- bio_list_init(&s->queued_bios);
- INIT_WORK(&s->queued_bios_work, flush_queued_bios);
-
if (!s->store->chunk_size) {
ti->error = "Chunk size not set";
- goto bad_load_and_register;
- }
-
- /* Add snapshot to the list of snapshots for this origin */
- /* Exceptions aren't triggered till snapshot_resume() is called */
- if (register_snapshot(s)) {
- r = -EINVAL;
- ti->error = "Cannot register snapshot origin";
- goto bad_load_and_register;
+ goto bad_read_metadata;
}
-
- ti->private = s;
ti->split_io = s->store->chunk_size;
- ti->num_flush_requests = 1;
return 0;
+bad_read_metadata:
+ unregister_snapshot(s);
+
bad_load_and_register:
mempool_destroy(s->tracked_chunk_pool);
dm_put_device(ti, s->origin);
bad_origin:
- kfree(s);
+ dm_exception_store_destroy(s->store);
-bad_snap:
- dm_exception_store_destroy(store);
+bad_store:
+ dm_put_device(ti, s->cow);
-bad_args:
+bad_cow:
+ kfree(s);
+
+bad:
return r;
}
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_src->store = u.store_swap;
+
+ snap_dest->store->snap = snap_dest;
+ snap_src->store->snap = snap_src;
+
+ snap_dest->ti->split_io = snap_dest->store->chunk_size;
+ snap_dest->valid = snap_src->valid;
+
+ /*
+ * 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;
flush_workqueue(ksnapd);
+ down_read(&_origins_lock);
+ /* Check whether exception handover must be cancelled */
+ (void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest);
+ 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);
+
/* Prevent further origin writes from using this snapshot. */
/* After this returns there can be no new kcopyd jobs. */
unregister_snapshot(s);
dm_exception_store_destroy(s->store);
+ dm_put_device(ti, s->cow);
+
kfree(s);
}
s->valid = 0;
- dm_table_event(s->store->ti->table);
+ dm_table_event(s->ti->table);
}
static void get_pending_exception(struct dm_snap_pending_exception *pe)
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->store->cow->bdev;
+ dest.bdev = s->cow->bdev;
dest.sector = chunk_to_sector(s->store, pe->e.new_chunk);
dest.count = src.count;
static void remap_exception(struct dm_snapshot *s, struct dm_exception *e,
struct bio *bio, chunk_t chunk)
{
- bio->bi_bdev = s->store->cow->bdev;
+ bio->bi_bdev = s->cow->bdev;
bio->bi_sector = chunk_to_sector(s->store,
dm_chunk_number(e->new_chunk) +
(chunk - e->old_chunk)) +
struct dm_snap_pending_exception *pe = NULL;
if (unlikely(bio_empty_barrier(bio))) {
- bio->bi_bdev = s->store->cow->bdev;
+ bio->bi_bdev = s->cow->bdev;
return DM_MAPIO_REMAPPED;
}
return 0;
}
+static void snapshot_postsuspend(struct dm_target *ti)
+{
+ struct dm_snapshot *s = ti->private;
+
+ down_write(&s->lock);
+ s->suspended = 1;
+ up_write(&s->lock);
+}
+
+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);
+ 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 (!snap_src->suspended) {
+ 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;
+
+ down_read(&_origins_lock);
+ (void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest);
+ 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);
+
+ /* Now we have correct chunk size, reregister */
+ reregister_snapshot(s);
down_write(&s->lock);
s->active = 1;
+ s->suspended = 0;
up_write(&s->lock);
}
* to make private copies if the output is to
* make sense.
*/
- DMEMIT("%s", snap->origin->name);
+ DMEMIT("%s %s", snap->origin->name, snap->cow->name);
snap->store->type->status(snap->store, type, result + sz,
maxlen - sz);
break;
/*-----------------------------------------------------------------
* Origin methods
*---------------------------------------------------------------*/
-static int __origin_write(struct list_head *snapshots, struct bio *bio)
+
+/*
+ * 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, first = 0;
struct dm_snapshot *snap;
goto next_snapshot;
/* Nothing to do if writing beyond end of snapshot */
- if (bio->bi_sector >= dm_table_get_size(snap->store->ti->table))
+ 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, bio->bi_sector);
+ chunk = sector_to_chunk(snap->store, sector);
/*
* Check exception table to see if block
first = 1;
}
- bio_list_add(&primary_pe->origin_bios, bio);
+ if (bio)
+ bio_list_add(&primary_pe->origin_bios, bio);
r = DM_MAPIO_SUBMITTED;
}
down_read(&_origins_lock);
o = __lookup_origin(origin->bdev);
if (o)
- r = __origin_write(&o->snapshots, bio);
+ r = __origin_write(&o->snapshots, bio->bi_sector, bio);
up_read(&_origins_lock);
return r;
static struct target_type snapshot_target = {
.name = "snapshot",
- .version = {1, 8, 0},
+ .version = {1, 9, 0},
.module = THIS_MODULE,
.ctr = snapshot_ctr,
.dtr = snapshot_dtr,
.map = snapshot_map,
.end_io = snapshot_end_io,
+ .postsuspend = snapshot_postsuspend,
+ .preresume = snapshot_preresume,
.resume = snapshot_resume,
.status = snapshot_status,
.iterate_devices = snapshot_iterate_devices,
projects / firefly-linux-kernel-4.4.55.git / blobdiff