diff options
| -rw-r--r-- | drivers/md/dm-exception-store.h | 17 | ||||
| -rw-r--r-- | drivers/md/dm-snap-persistent.c | 114 |
2 files changed, 129 insertions, 2 deletions
diff --git a/drivers/md/dm-exception-store.h b/drivers/md/dm-exception-store.h index bb8874653de1..c53e08935b42 100644 --- a/drivers/md/dm-exception-store.h +++ b/drivers/md/dm-exception-store.h @@ -75,6 +75,23 @@ struct dm_exception_store_type { void *callback_context); /* + * Returns 0 if the exception store is empty. + * + * If there are exceptions still to be merged, sets + * *last_old_chunk and *last_new_chunk to the most recent + * still-to-be-merged chunk and returns the number of + * consecutive previous ones. + */ + int (*prepare_merge) (struct dm_exception_store *store, + chunk_t *last_old_chunk, chunk_t *last_new_chunk); + + /* + * Clear the last n exceptions. + * nr_merged must be <= the value returned by prepare_merge. + */ + int (*commit_merge) (struct dm_exception_store *store, int nr_merged); + + /* * The snapshot is invalid, note this in the metadata. */ void (*drop_snapshot) (struct dm_exception_store *store); diff --git a/drivers/md/dm-snap-persistent.c b/drivers/md/dm-snap-persistent.c index 157999ebd236..7d08879689ac 100644 --- a/drivers/md/dm-snap-persistent.c +++ b/drivers/md/dm-snap-persistent.c @@ -55,6 +55,8 @@ */ #define SNAPSHOT_DISK_VERSION 1 +#define NUM_SNAPSHOT_HDR_CHUNKS 1 + struct disk_header { uint32_t magic; @@ -120,7 +122,22 @@ struct pstore { /* * The next free chunk for an exception. + * + * When creating exceptions, all the chunks here and above are + * free. It holds the next chunk to be allocated. On rare + * occasions (e.g. after a system crash) holes can be left in + * the exception store because chunks can be committed out of + * order. + * + * When merging exceptions, it does not necessarily mean all the + * chunks here and above are free. It holds the value it would + * have held if all chunks had been committed in order of + * allocation. Consequently the value may occasionally be + * slightly too low, but since it's only used for 'status' and + * it can never reach its minimum value too early this doesn't + * matter. */ + chunk_t next_free; /* @@ -409,6 +426,15 @@ static void write_exception(struct pstore *ps, e->new_chunk = cpu_to_le64(de->new_chunk); } +static void clear_exception(struct pstore *ps, uint32_t index) +{ + struct disk_exception *e = get_exception(ps, index); + + /* clear it */ + e->old_chunk = 0; + e->new_chunk = 0; +} + /* * Registers the exceptions that are present in the current area. * 'full' is filled in to indicate if the area has been @@ -505,7 +531,8 @@ static void persistent_usage(struct dm_exception_store *store, * Then there are (ps->current_area + 1) metadata chunks, each one * separated from the next by ps->exceptions_per_area data chunks. */ - *metadata_sectors = (ps->current_area + 2) * store->chunk_size; + *metadata_sectors = (ps->current_area + 1 + NUM_SNAPSHOT_HDR_CHUNKS) * + store->chunk_size; } static void persistent_dtr(struct dm_exception_store *store) @@ -680,6 +707,85 @@ static void persistent_commit_exception(struct dm_exception_store *store, ps->callback_count = 0; } +static int persistent_prepare_merge(struct dm_exception_store *store, + chunk_t *last_old_chunk, + chunk_t *last_new_chunk) +{ + struct pstore *ps = get_info(store); + struct disk_exception de; + int nr_consecutive; + int r; + + /* + * When current area is empty, move back to preceding area. + */ + if (!ps->current_committed) { + /* + * Have we finished? + */ + if (!ps->current_area) + return 0; + + ps->current_area--; + r = area_io(ps, READ); + if (r < 0) + return r; + ps->current_committed = ps->exceptions_per_area; + } + + read_exception(ps, ps->current_committed - 1, &de); + *last_old_chunk = de.old_chunk; + *last_new_chunk = de.new_chunk; + + /* + * Find number of consecutive chunks within the current area, + * working backwards. + */ + for (nr_consecutive = 1; nr_consecutive < ps->current_committed; + nr_consecutive++) { + read_exception(ps, ps->current_committed - 1 - nr_consecutive, + &de); + if (de.old_chunk != *last_old_chunk - nr_consecutive || + de.new_chunk != *last_new_chunk - nr_consecutive) + break; + } + + return nr_consecutive; +} + +static int persistent_commit_merge(struct dm_exception_store *store, + int nr_merged) +{ + int r, i; + struct pstore *ps = get_info(store); + + BUG_ON(nr_merged > ps->current_committed); + + for (i = 0; i < nr_merged; i++) + clear_exception(ps, ps->current_committed - 1 - i); + + r = area_io(ps, WRITE); + if (r < 0) + return r; + + ps->current_committed -= nr_merged; + + /* + * At this stage, only persistent_usage() uses ps->next_free, so + * we make no attempt to keep ps->next_free strictly accurate + * as exceptions may have been committed out-of-order originally. + * Once a snapshot has become merging, we set it to the value it + * would have held had all the exceptions been committed in order. + * + * ps->current_area does not get reduced by prepare_merge() until + * after commit_merge() has removed the nr_merged previous exceptions. + */ + ps->next_free = (area_location(ps, ps->current_area) - 1) + + (ps->current_committed + 1) + NUM_SNAPSHOT_HDR_CHUNKS; + + return 0; +} + static void persistent_drop_snapshot(struct dm_exception_store *store) { struct pstore *ps = get_info(store); @@ -705,7 +811,7 @@ static int persistent_ctr(struct dm_exception_store *store, ps->area = NULL; ps->zero_area = NULL; ps->header_area = NULL; - ps->next_free = 2; /* skipping the header and first area */ + ps->next_free = NUM_SNAPSHOT_HDR_CHUNKS + 1; /* header and 1st area */ ps->current_committed = 0; ps->callback_count = 0; @@ -748,6 +854,8 @@ static struct dm_exception_store_type _persistent_type = { .read_metadata = persistent_read_metadata, .prepare_exception = persistent_prepare_exception, .commit_exception = persistent_commit_exception, + .prepare_merge = persistent_prepare_merge, + .commit_merge = persistent_commit_merge, .drop_snapshot = persistent_drop_snapshot, .usage = persistent_usage, .status = persistent_status, @@ -761,6 +869,8 @@ static struct dm_exception_store_type _persistent_compat_type = { .read_metadata = persistent_read_metadata, .prepare_exception = persistent_prepare_exception, .commit_exception = persistent_commit_exception, + .prepare_merge = persistent_prepare_merge, + .commit_merge = persistent_commit_merge, .drop_snapshot = persistent_drop_snapshot, .usage = persistent_usage, .status = persistent_status, |