linux/drivers/md/dm-thin-metadata.h

/*
 * Copyright (C) 2010-2011 Red Hat, Inc.
 *
 * This file is released under the GPL.
 */

#ifndef DM_THIN_METADATA_H
#define DM_THIN_METADATA_H

#include "persistent-data/dm-block-manager.h"
#include "persistent-data/dm-space-map.h"

#define THIN_METADATA_BLOCK_SIZE 4096

/*
 * The metadata device is currently limited in size.
 *
 * We have one block of index, which can hold 255 index entries.  Each
 * index entry contains allocation info about 16k metadata blocks.
 */
#define THIN_METADATA_MAX_SECTORS (255 * (1 << 14) * (THIN_METADATA_BLOCK_SIZE / (1 << SECTOR_SHIFT)))

/*
 * A metadata device larger than 16GB triggers a warning.
 */
#define THIN_METADATA_MAX_SECTORS_WARNING (16 * (1024 * 1024 * 1024 >> SECTOR_SHIFT))

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

struct dm_pool_metadata;
struct dm_thin_device;

/*
 * Device identifier
 */
typedef uint64_t dm_thin_id;

/*
 * Reopens or creates a new, empty metadata volume.
 */
struct dm_pool_metadata *dm_pool_metadata_open(struct block_device *bdev,
					       sector_t data_block_size,
					       bool format_device);

int dm_pool_metadata_close(struct dm_pool_metadata *pmd);

/*
 * Compat feature flags.  Any incompat flags beyond the ones
 * specified below will prevent use of the thin metadata.
 */
#define THIN_FEATURE_COMPAT_SUPP	  0UL
#define THIN_FEATURE_COMPAT_RO_SUPP	  0UL
#define THIN_FEATURE_INCOMPAT_SUPP	  0UL

/*
 * Device creation/deletion.
 */
int dm_pool_create_thin(struct dm_pool_metadata *pmd, dm_thin_id dev);

/*
 * An internal snapshot.
 *
 * You can only snapshot a quiesced origin i.e. one that is either
 * suspended or not instanced at all.
 */
int dm_pool_create_snap(struct dm_pool_metadata *pmd, dm_thin_id dev,
			dm_thin_id origin);

/*
 * Deletes a virtual device from the metadata.  It _is_ safe to call this
 * when that device is open.  Operations on that device will just start
 * failing.  You still need to call close() on the device.
 */
int dm_pool_delete_thin_device(struct dm_pool_metadata *pmd,
			       dm_thin_id dev);

/*
 * Commits _all_ metadata changes: device creation, deletion, mapping
 * updates.
 */
int dm_pool_commit_metadata(struct dm_pool_metadata *pmd);

/*
 * Discards all uncommitted changes.  Rereads the superblock, rolling back
 * to the last good transaction.  Thin devices remain open.
 * dm_thin_aborted_changes() tells you if they had uncommitted changes.
 *
 * If this call fails it's only useful to call dm_pool_metadata_close().
 * All other methods will fail with -EINVAL.
 */
int dm_pool_abort_metadata(struct dm_pool_metadata *pmd);

/*
 * Set/get userspace transaction id.
 */
int dm_pool_set_metadata_transaction_id(struct dm_pool_metadata *pmd,
					uint64_t current_id,
					uint64_t new_id);

int dm_pool_get_metadata_transaction_id(struct dm_pool_metadata *pmd,
					uint64_t *result);

/*
 * Hold/get root for userspace transaction.
 *
 * The metadata snapshot is a copy of the current superblock (minus the
 * space maps).  Userland can access the data structures for READ
 * operations only.  A small performance hit is incurred by providing this
 * copy of the metadata to userland due to extra copy-on-write operations
 * on the metadata nodes.  Release this as soon as you finish with it.
 */
int dm_pool_reserve_metadata_snap(struct dm_pool_metadata *pmd);
int dm_pool_release_metadata_snap(struct dm_pool_metadata *pmd);

int dm_pool_get_metadata_snap(struct dm_pool_metadata *pmd,
			      dm_block_t *result);

/*
 * Actions on a single virtual device.
 */

/*
 * Opening the same device more than once will fail with -EBUSY.
 */
int dm_pool_open_thin_device(struct dm_pool_metadata *pmd, dm_thin_id dev,
			     struct dm_thin_device **td);

int dm_pool_close_thin_device(struct dm_thin_device *td);

dm_thin_id dm_thin_dev_id(struct dm_thin_device *td);

struct dm_thin_lookup_result {
	dm_block_t block;
	unsigned shared:1;
};

/*
 * Returns:
 *   -EWOULDBLOCK iff @can_block is set and would block.
 *   -ENODATA iff that mapping is not present.
 *   0 success
 */
int dm_thin_find_block(struct dm_thin_device *td, dm_block_t block,
		       int can_block, struct dm_thin_lookup_result *result);

/*
 * Obtain an unused block.
 */
int dm_pool_alloc_data_block(struct dm_pool_metadata *pmd, dm_block_t *result);

/*
 * Insert or remove block.
 */
int dm_thin_insert_block(struct dm_thin_device *td, dm_block_t block,
			 dm_block_t data_block);

int dm_thin_remove_block(struct dm_thin_device *td, dm_block_t block);

/*
 * Queries.
 */
bool dm_thin_changed_this_transaction(struct dm_thin_device *td);

bool dm_thin_aborted_changes(struct dm_thin_device *td);

int dm_thin_get_highest_mapped_block(struct dm_thin_device *td,
				     dm_block_t *highest_mapped);

int dm_thin_get_mapped_count(struct dm_thin_device *td, dm_block_t *result);

int dm_pool_get_free_block_count(struct dm_pool_metadata *pmd,
				 dm_block_t *result);

int dm_pool_get_free_metadata_block_count(struct dm_pool_metadata *pmd,
					  dm_block_t *result);

int dm_pool_get_metadata_dev_size(struct dm_pool_metadata *pmd,
				  dm_block_t *result);

int dm_pool_get_data_block_size(struct dm_pool_metadata *pmd, sector_t *result);

int dm_pool_get_data_dev_size(struct dm_pool_metadata *pmd, dm_block_t *result);

/*
 * Returns -ENOSPC if the new size is too small and already allocated
 * blocks would be lost.
 */
int dm_pool_resize_data_dev(struct dm_pool_metadata *pmd, dm_block_t new_size);
int dm_pool_resize_metadata_dev(struct dm_pool_metadata *pmd, dm_block_t new_size);

/*
 * Flicks the underlying block manager into read only mode, so you know
 * that nothing is changing.
 */
void dm_pool_metadata_read_only(struct dm_pool_metadata *pmd);

int dm_pool_register_metadata_threshold(struct dm_pool_metadata *pmd,
					dm_block_t threshold,
					dm_sm_threshold_fn fn,
					void *context);

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

#endif