| From 9b1cc9f251affdd27f29fe46d0989ba76c33faf6 Mon Sep 17 00:00:00 2001 |
| From: Joe Thornber <ejt@redhat.com> |
| Date: Fri, 23 Jan 2015 10:00:07 +0000 |
| Subject: dm cache: share cache-metadata object across inactive and active DM tables |
| |
| From: Joe Thornber <ejt@redhat.com> |
| |
| commit 9b1cc9f251affdd27f29fe46d0989ba76c33faf6 upstream. |
| |
| If a DM table is reloaded with an inactive table when the device is not |
| suspended (normal procedure for LVM2), then there will be two dm-bufio |
| objects that can diverge. This can lead to a situation where the |
| inactive table uses bufio to read metadata at the same time the active |
| table writes metadata -- resulting in the inactive table having stale |
| metadata buffers once it is promoted to the active table slot. |
| |
| Fix this by using reference counting and a global list of cache metadata |
| objects to ensure there is only one metadata object per metadata device. |
| |
| Signed-off-by: Joe Thornber <ejt@redhat.com> |
| Signed-off-by: Mike Snitzer <snitzer@redhat.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| drivers/md/dm-cache-metadata.c | 101 ++++++++++++++++++++++++++++++++++++++--- |
| 1 file changed, 95 insertions(+), 6 deletions(-) |
| |
| --- a/drivers/md/dm-cache-metadata.c |
| +++ b/drivers/md/dm-cache-metadata.c |
| @@ -88,6 +88,9 @@ struct cache_disk_superblock { |
| } __packed; |
| |
| struct dm_cache_metadata { |
| + atomic_t ref_count; |
| + struct list_head list; |
| + |
| struct block_device *bdev; |
| struct dm_block_manager *bm; |
| struct dm_space_map *metadata_sm; |
| @@ -634,10 +637,10 @@ static void unpack_value(__le64 value_le |
| |
| /*----------------------------------------------------------------*/ |
| |
| -struct dm_cache_metadata *dm_cache_metadata_open(struct block_device *bdev, |
| - sector_t data_block_size, |
| - bool may_format_device, |
| - size_t policy_hint_size) |
| +static struct dm_cache_metadata *metadata_open(struct block_device *bdev, |
| + sector_t data_block_size, |
| + bool may_format_device, |
| + size_t policy_hint_size) |
| { |
| int r; |
| struct dm_cache_metadata *cmd; |
| @@ -648,6 +651,7 @@ struct dm_cache_metadata *dm_cache_metad |
| return NULL; |
| } |
| |
| + atomic_set(&cmd->ref_count, 1); |
| init_rwsem(&cmd->root_lock); |
| cmd->bdev = bdev; |
| cmd->data_block_size = data_block_size; |
| @@ -670,10 +674,95 @@ struct dm_cache_metadata *dm_cache_metad |
| return cmd; |
| } |
| |
| +/* |
| + * We keep a little list of ref counted metadata objects to prevent two |
| + * different target instances creating separate bufio instances. This is |
| + * an issue if a table is reloaded before the suspend. |
| + */ |
| +static DEFINE_MUTEX(table_lock); |
| +static LIST_HEAD(table); |
| + |
| +static struct dm_cache_metadata *lookup(struct block_device *bdev) |
| +{ |
| + struct dm_cache_metadata *cmd; |
| + |
| + list_for_each_entry(cmd, &table, list) |
| + if (cmd->bdev == bdev) { |
| + atomic_inc(&cmd->ref_count); |
| + return cmd; |
| + } |
| + |
| + return NULL; |
| +} |
| + |
| +static struct dm_cache_metadata *lookup_or_open(struct block_device *bdev, |
| + sector_t data_block_size, |
| + bool may_format_device, |
| + size_t policy_hint_size) |
| +{ |
| + struct dm_cache_metadata *cmd, *cmd2; |
| + |
| + mutex_lock(&table_lock); |
| + cmd = lookup(bdev); |
| + mutex_unlock(&table_lock); |
| + |
| + if (cmd) |
| + return cmd; |
| + |
| + cmd = metadata_open(bdev, data_block_size, may_format_device, policy_hint_size); |
| + if (cmd) { |
| + mutex_lock(&table_lock); |
| + cmd2 = lookup(bdev); |
| + if (cmd2) { |
| + mutex_unlock(&table_lock); |
| + __destroy_persistent_data_objects(cmd); |
| + kfree(cmd); |
| + return cmd2; |
| + } |
| + list_add(&cmd->list, &table); |
| + mutex_unlock(&table_lock); |
| + } |
| + |
| + return cmd; |
| +} |
| + |
| +static bool same_params(struct dm_cache_metadata *cmd, sector_t data_block_size) |
| +{ |
| + if (cmd->data_block_size != data_block_size) { |
| + DMERR("data_block_size (%llu) different from that in metadata (%llu)\n", |
| + (unsigned long long) data_block_size, |
| + (unsigned long long) cmd->data_block_size); |
| + return false; |
| + } |
| + |
| + return true; |
| +} |
| + |
| +struct dm_cache_metadata *dm_cache_metadata_open(struct block_device *bdev, |
| + sector_t data_block_size, |
| + bool may_format_device, |
| + size_t policy_hint_size) |
| +{ |
| + struct dm_cache_metadata *cmd = lookup_or_open(bdev, data_block_size, |
| + may_format_device, policy_hint_size); |
| + if (cmd && !same_params(cmd, data_block_size)) { |
| + dm_cache_metadata_close(cmd); |
| + return NULL; |
| + } |
| + |
| + return cmd; |
| +} |
| + |
| void dm_cache_metadata_close(struct dm_cache_metadata *cmd) |
| { |
| - __destroy_persistent_data_objects(cmd); |
| - kfree(cmd); |
| + if (atomic_dec_and_test(&cmd->ref_count)) { |
| + mutex_lock(&table_lock); |
| + list_del(&cmd->list); |
| + mutex_unlock(&table_lock); |
| + |
| + __destroy_persistent_data_objects(cmd); |
| + kfree(cmd); |
| + } |
| } |
| |
| int dm_cache_resize(struct dm_cache_metadata *cmd, dm_cblock_t new_cache_size) |