diff options
| -rw-r--r-- | drivers/md/dm-clone-metadata.c | 90 |
1 files changed, 62 insertions, 28 deletions
diff --git a/drivers/md/dm-clone-metadata.c b/drivers/md/dm-clone-metadata.c index 08c552e5e41b..ee870a425ab8 100644 --- a/drivers/md/dm-clone-metadata.c +++ b/drivers/md/dm-clone-metadata.c @@ -67,23 +67,34 @@ struct superblock_disk { * To save constantly doing look ups on disk we keep an in core copy of the * on-disk bitmap, the region_map. * - * To further reduce metadata I/O overhead we use a second bitmap, the dmap - * (dirty bitmap), which tracks the dirty words, i.e. longs, of the region_map. + * In order to track which regions are hydrated during a metadata transaction, + * we use a second set of bitmaps, the dmap (dirty bitmap), which includes two + * bitmaps, namely dirty_regions and dirty_words. The dirty_regions bitmap + * tracks the regions that got hydrated during the current metadata + * transaction. The dirty_words bitmap tracks the dirty words, i.e. longs, of + * the dirty_regions bitmap. + * + * This allows us to precisely track the regions that were hydrated during the + * current metadata transaction and update the metadata accordingly, when we + * commit the current transaction. This is important because dm-clone should + * only commit the metadata of regions that were properly flushed to the + * destination device beforehand. Otherwise, in case of a crash, we could end + * up with a corrupted dm-clone device. * * When a region finishes hydrating dm-clone calls * dm_clone_set_region_hydrated(), or for discard requests * dm_clone_cond_set_range(), which sets the corresponding bits in region_map * and dmap. * - * During a metadata commit we scan the dmap for dirty region_map words (longs) - * and update accordingly the on-disk metadata. Thus, we don't have to flush to - * disk the whole region_map. We can just flush the dirty region_map words. + * During a metadata commit we scan dmap->dirty_words and dmap->dirty_regions + * and update the on-disk metadata accordingly. Thus, we don't have to flush to + * disk the whole region_map. We can just flush the dirty region_map bits. * - * We use a dirty bitmap, which is smaller than the original region_map, to - * reduce the amount of memory accesses during a metadata commit. As dm-bitset - * accesses the on-disk bitmap in 64-bit word granularity, there is no - * significant benefit in tracking the dirty region_map bits with a smaller - * granularity. + * We use the helper dmap->dirty_words bitmap, which is smaller than the + * original region_map, to reduce the amount of memory accesses during a + * metadata commit. Moreover, as dm-bitset also accesses the on-disk bitmap in + * 64-bit word granularity, the dirty_words bitmap helps us avoid useless disk + * accesses. * * We could update directly the on-disk bitmap, when dm-clone calls either * dm_clone_set_region_hydrated() or dm_clone_cond_set_range(), buts this @@ -92,12 +103,13 @@ struct superblock_disk { * e.g., in a hooked overwrite bio's completion routine, and further reduce the * I/O completion latency. * - * We maintain two dirty bitmaps. During a metadata commit we atomically swap - * the currently used dmap with the unused one. This allows the metadata update - * functions to run concurrently with an ongoing commit. + * We maintain two dirty bitmap sets. During a metadata commit we atomically + * swap the currently used dmap with the unused one. This allows the metadata + * update functions to run concurrently with an ongoing commit. */ struct dirty_map { unsigned long *dirty_words; + unsigned long *dirty_regions; unsigned int changed; }; @@ -461,22 +473,40 @@ static size_t bitmap_size(unsigned long nr_bits) return BITS_TO_LONGS(nr_bits) * sizeof(long); } -static int dirty_map_init(struct dm_clone_metadata *cmd) +static int __dirty_map_init(struct dirty_map *dmap, unsigned long nr_words, + unsigned long nr_regions) { - cmd->dmap[0].changed = 0; - cmd->dmap[0].dirty_words = kvzalloc(bitmap_size(cmd->nr_words), GFP_KERNEL); + dmap->changed = 0; - if (!cmd->dmap[0].dirty_words) { - DMERR("Failed to allocate dirty bitmap"); + dmap->dirty_words = kvzalloc(bitmap_size(nr_words), GFP_KERNEL); + if (!dmap->dirty_words) + return -ENOMEM; + + dmap->dirty_regions = kvzalloc(bitmap_size(nr_regions), GFP_KERNEL); + if (!dmap->dirty_regions) { + kvfree(dmap->dirty_words); return -ENOMEM; } - cmd->dmap[1].changed = 0; - cmd->dmap[1].dirty_words = kvzalloc(bitmap_size(cmd->nr_words), GFP_KERNEL); + return 0; +} - if (!cmd->dmap[1].dirty_words) { +static void __dirty_map_exit(struct dirty_map *dmap) +{ + kvfree(dmap->dirty_words); + kvfree(dmap->dirty_regions); +} + +static int dirty_map_init(struct dm_clone_metadata *cmd) +{ + if (__dirty_map_init(&cmd->dmap[0], cmd->nr_words, cmd->nr_regions)) { DMERR("Failed to allocate dirty bitmap"); - kvfree(cmd->dmap[0].dirty_words); + return -ENOMEM; + } + + if (__dirty_map_init(&cmd->dmap[1], cmd->nr_words, cmd->nr_regions)) { + DMERR("Failed to allocate dirty bitmap"); + __dirty_map_exit(&cmd->dmap[0]); return -ENOMEM; } @@ -487,8 +517,8 @@ static int dirty_map_init(struct dm_clone_metadata *cmd) static void dirty_map_exit(struct dm_clone_metadata *cmd) { - kvfree(cmd->dmap[0].dirty_words); - kvfree(cmd->dmap[1].dirty_words); + __dirty_map_exit(&cmd->dmap[0]); + __dirty_map_exit(&cmd->dmap[1]); } static int __load_bitset_in_core(struct dm_clone_metadata *cmd) @@ -633,21 +663,23 @@ unsigned long dm_clone_find_next_unhydrated_region(struct dm_clone_metadata *cmd return find_next_zero_bit(cmd->region_map, cmd->nr_regions, start); } -static int __update_metadata_word(struct dm_clone_metadata *cmd, unsigned long word) +static int __update_metadata_word(struct dm_clone_metadata *cmd, + unsigned long *dirty_regions, + unsigned long word) { int r; unsigned long index = word * BITS_PER_LONG; unsigned long max_index = min(cmd->nr_regions, (word + 1) * BITS_PER_LONG); while (index < max_index) { - if (test_bit(index, cmd->region_map)) { + if (test_bit(index, dirty_regions)) { r = dm_bitset_set_bit(&cmd->bitset_info, cmd->bitset_root, index, &cmd->bitset_root); - if (r) { DMERR("dm_bitset_set_bit failed"); return r; } + __clear_bit(index, dirty_regions); } index++; } @@ -721,7 +753,7 @@ static int __flush_dmap(struct dm_clone_metadata *cmd, struct dirty_map *dmap) if (word == cmd->nr_words) break; - r = __update_metadata_word(cmd, word); + r = __update_metadata_word(cmd, dmap->dirty_regions, word); if (r) return r; @@ -802,6 +834,7 @@ int dm_clone_set_region_hydrated(struct dm_clone_metadata *cmd, unsigned long re dmap = cmd->current_dmap; __set_bit(word, dmap->dirty_words); + __set_bit(region_nr, dmap->dirty_regions); __set_bit(region_nr, cmd->region_map); dmap->changed = 1; @@ -830,6 +863,7 @@ int dm_clone_cond_set_range(struct dm_clone_metadata *cmd, unsigned long start, if (!test_bit(region_nr, cmd->region_map)) { word = region_nr / BITS_PER_LONG; __set_bit(word, dmap->dirty_words); + __set_bit(region_nr, dmap->dirty_regions); __set_bit(region_nr, cmd->region_map); dmap->changed = 1; } |