diff options
| -rw-r--r-- | drivers/md/dm-snap.c | 83 |
1 files changed, 83 insertions, 0 deletions
diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c index bc52776..1498704 100644 --- a/drivers/md/dm-snap.c +++ b/drivers/md/dm-snap.c @@ -270,6 +270,10 @@ struct origin { 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; @@ -847,14 +851,38 @@ out: 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))) @@ -887,6 +915,24 @@ static void snapshot_merge_next_chunks(struct dm_snapshot *s) 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; @@ -1372,6 +1418,8 @@ static void pending_complete(struct dm_snap_pending_exception *pe, int success) 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 */ @@ -1963,6 +2011,41 @@ static int do_origin(struct dm_dev *origin, struct bio *bio) } /* + * 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. */ |
