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Commit 9b1cc9f2 authored by Joe Thornber's avatar Joe Thornber Committed by Mike Snitzer
Browse files

dm cache: share cache-metadata object across inactive and active DM tables 



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: default avatarJoe Thornber <ejt@redhat.com>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org
parent 5164bece

drivers/md/dm-cache-metadata.c

+95 −6
Original line number Original line Diff line number Diff line
@@ -94,6 +94,9 @@ struct cache_disk_superblock { 
} __packed;

} __packed;





struct dm_cache_metadata {

struct dm_cache_metadata {

	atomic_t ref_count;

	struct list_head list;



	struct block_device *bdev;

	struct block_device *bdev;

	struct dm_block_manager *bm;

	struct dm_block_manager *bm;

	struct dm_space_map *metadata_sm;

	struct dm_space_map *metadata_sm;
@@ -669,7 +672,7 @@ static void unpack_value(__le64 value_le, dm_oblock_t *block, unsigned *flags) 




/*----------------------------------------------------------------*/

/*----------------------------------------------------------------*/





struct dm_cache_metadata *dm_cache_metadata_open(struct block_device *bdev,

static struct dm_cache_metadata *metadata_open(struct block_device *bdev,

					       sector_t data_block_size,

					       sector_t data_block_size,

					       bool may_format_device,

					       bool may_format_device,

					       size_t policy_hint_size)

					       size_t policy_hint_size)
@@ -683,6 +686,7 @@ struct dm_cache_metadata *dm_cache_metadata_open(struct block_device *bdev, 
		return NULL;

		return NULL;

	}

	}





	atomic_set(&cmd->ref_count, 1);

	init_rwsem(&cmd->root_lock);

	init_rwsem(&cmd->root_lock);

	cmd->bdev = bdev;

	cmd->bdev = bdev;

	cmd->data_block_size = data_block_size;

	cmd->data_block_size = data_block_size;
@@ -705,11 +709,96 @@ struct dm_cache_metadata *dm_cache_metadata_open(struct block_device *bdev, 
	return cmd;

	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)

void dm_cache_metadata_close(struct dm_cache_metadata *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);

		__destroy_persistent_data_objects(cmd);

		kfree(cmd);

		kfree(cmd);

	}

	}

}





/*

/*

 * Checks that the given cache block is either unmapped or clean.

 * Checks that the given cache block is either unmapped or clean.