mempool_t *tracked_chunk_pool;
spinlock_t tracked_chunk_lock;
struct hlist_head tracked_chunk_hash[DM_TRACKED_CHUNK_HASH_SIZE];
+
+ /* 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;
+
+ /*
+ * 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
+
struct dm_dev *dm_snap_cow(struct dm_snapshot *s)
{
return s->cow;
static struct list_head *_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;
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;
}
return 0;
}
+static void merge_shutdown(struct dm_snapshot *s)
+{
+ clear_bit_unlock(RUNNING_MERGE, &s->state_bits);
+ smp_mb__after_clear_bit();
+ 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 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 r;
+ chunk_t old_chunk, new_chunk;
+ struct dm_io_region src, dest;
+ 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;
+ }
+
+ r = s->store->type->prepare_merge(s->store, &old_chunk, &new_chunk);
+ if (r <= 0) {
+ if (r < 0)
+ DMERR("Read error in exception store: "
+ "shutting down merge");
+ goto shut;
+ }
+
+ /* TODO: use larger I/O size once we verify that kcopyd handles it */
+
+ dest.bdev = s->origin->bdev;
+ dest.sector = chunk_to_sector(s->store, old_chunk);
+ dest.count = min((sector_t)s->store->chunk_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, s->store->chunk_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 = 1;
+ up_write(&s->lock);
+
+ __check_for_conflicting_io(s, old_chunk);
+
+ 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:
+ down_write(&s->lock);
+ 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);
+}
+
+static int wait_schedule(void *ptr)
+{
+ schedule();
+
+ return 0;
+}
+
+/*
+ * 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, wait_schedule,
+ TASK_UNINTERRUPTIBLE);
+ clear_bit(SHUTDOWN_MERGE, &s->state_bits);
+}
+
/*
* Construct a snapshot mapping: <origin_dev> <COW-dev> <p/n> <chunk-size>
*/
init_rwsem(&s->lock);
INIT_LIST_HEAD(&s->list);
spin_lock_init(&s->pe_lock);
+ s->state_bits = 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)) {
}
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);
origin_bios = bio_list_get(&pe->origin_bios);
free_pending_exception(pe);
+ increment_pending_exceptions_done_count();
+
up_write(&s->lock);
/* Submit any pending write bios */
* 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,
union map_info *map_context)
chunk = sector_to_chunk(s->store, bio->bi_sector);
- down_read(&s->lock);
+ down_write(&s->lock);
/* Full snapshots are not usable */
if (!s->valid) {
/* 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_rw(bio) == WRITE &&
+ chunk >= s->first_merging_chunk &&
+ chunk < (s->first_merging_chunk +
+ s->num_merging_chunks)) {
+ bio->bi_bdev = 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_rw(bio) == WRITE)
+ map_context->ptr = track_chunk(s, chunk);
goto out_unlock;
}
bio->bi_bdev = s->origin->bdev;
if (bio_rw(bio) == WRITE) {
- up_read(&s->lock);
+ up_write(&s->lock);
return do_origin(s->origin, bio);
}
out_unlock:
- up_read(&s->lock);
+ up_write(&s->lock);
return r;
}
return 0;
}
+static void snapshot_merge_presuspend(struct dm_target *ti)
+{
+ struct dm_snapshot *s = ti->private;
+
+ stop_merge(s);
+}
+
static void snapshot_postsuspend(struct dm_target *ti)
{
struct dm_snapshot *s = ti->private;
up_write(&s->lock);
}
+static sector_t get_origin_minimum_chunksize(struct block_device *bdev)
+{
+ sector_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->split_io
+ */
+ ti->split_io = get_origin_minimum_chunksize(s->origin->bdev);
+
+ start_merge(s);
+}
+
static int snapshot_status(struct dm_target *ti, status_type_t type,
char *result, unsigned int maxlen)
{
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 split_io
+ * by snapshot_merge_resume().
+ */
+ down_read(&_origins_lock);
+ o = __lookup_origin(merging_snap->origin->bdev);
+ for (n = 0; n < size; n += merging_snap->ti->split_io)
+ 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.
*/
{
struct dm_dev *dev = ti->private;
- down_read(&_origins_lock);
-
- ti->split_io = __minimum_chunk_size(__lookup_origin(dev->bdev));
-
- up_read(&_origins_lock);
+ ti->split_io = get_origin_minimum_chunksize(dev->bdev);
}
static int origin_status(struct dm_target *ti, status_type_t type, char *result,
.dtr = snapshot_dtr,
.map = snapshot_merge_map,
.end_io = snapshot_end_io,
+ .presuspend = snapshot_merge_presuspend,
.postsuspend = snapshot_postsuspend,
.preresume = snapshot_preresume,
- .resume = snapshot_resume,
+ .resume = snapshot_merge_resume,
.status = snapshot_status,
.iterate_devices = snapshot_iterate_devices,
};
projects / firefly-linux-kernel-4.4.55.git / blobdiff