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path: root/drivers/md/dm-snap.c
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Diffstat (limited to 'drivers/md/dm-snap.c')
-rw-r--r--drivers/md/dm-snap.c239
1 files changed, 233 insertions, 6 deletions
diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
index 7ddee7c0c518..dc2412e6c5cf 100644
--- a/drivers/md/dm-snap.c
+++ b/drivers/md/dm-snap.c
@@ -106,8 +106,20 @@ struct dm_snapshot {
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;
};
+/*
+ * 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;
@@ -386,6 +398,13 @@ static int __validate_exception_handover(struct dm_snapshot *snap)
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;
}
@@ -721,6 +740,178 @@ static int init_hash_tables(struct dm_snapshot *s)
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);
+}
+
+/*
+ * 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;
+
+ /* FIXME: interlock writes to this chunk */
+
+ 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 int remove_single_exception_chunk(struct dm_snapshot *s,
+ chunk_t old_chunk)
+{
+ int r = 0;
+
+ down_write(&s->lock);
+ r = __remove_single_exception_chunk(s, old_chunk);
+ up_write(&s->lock);
+
+ return r;
+}
+
+static void merge_callback(int read_err, unsigned long write_err,
+ void *context);
+
+static void snapshot_merge_next_chunks(struct dm_snapshot *s)
+{
+ int r;
+ chunk_t old_chunk, new_chunk;
+ struct dm_io_region src, dest;
+
+ 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 */
+
+ if (remove_single_exception_chunk(s, old_chunk) < 0)
+ goto shut;
+
+ 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;
+
+ dm_kcopyd_copy(s->kcopyd_client, &src, 1, &dest, 0, merge_callback, s);
+ return;
+
+shut:
+ merge_shutdown(s);
+}
+
+static void merge_callback(int read_err, unsigned long write_err, void *context)
+{
+ struct dm_snapshot *s = context;
+
+ 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, 1) < 0) {
+ DMERR("Write error in exception store: shutting down merge");
+ goto shut;
+ }
+
+ snapshot_merge_next_chunks(s);
+
+ return;
+
+shut:
+ 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>
*/
@@ -791,6 +982,7 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
init_rwsem(&s->lock);
INIT_LIST_HEAD(&s->list);
spin_lock_init(&s->pe_lock);
+ s->state_bits = 0;
/* Allocate hash table for COW data */
if (init_hash_tables(s)) {
@@ -963,6 +1155,9 @@ static void snapshot_dtr(struct dm_target *ti)
}
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);
@@ -1404,6 +1599,13 @@ static int snapshot_end_io(struct dm_target *ti, struct bio *bio,
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;
@@ -1464,6 +1666,34 @@ static void snapshot_resume(struct dm_target *ti)
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)
{
@@ -1722,11 +1952,7 @@ static void origin_resume(struct dm_target *ti)
{
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,
@@ -1790,9 +2016,10 @@ static struct target_type merge_target = {
.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,
};