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Add the dm-clone target, which allows cloning of arbitrary block devices. dm-clone produces a one-to-one copy of an existing, read-only source device into a writable destination device: It presents a virtual block device which makes all data appear immediately, and redirects reads and writes accordingly. The main use case of dm-clone is to clone a potentially remote, high-latency, read-only, archival-type block device into a writable, fast, primary-type device for fast, low-latency I/O. The cloned device is visible/mountable immediately and the copy of the source device to the destination device happens in the background, in parallel with user I/O. When the cloning completes, the dm-clone table can be removed altogether and be replaced, e.g., by a linear table, mapping directly to the destination device. For further information and examples of how to use dm-clone, please read Documentation/admin-guide/device-mapper/dm-clone.rst Suggested-by: Vangelis Koukis <vkoukis@arrikto.com> Co-developed-by: Ilias Tsitsimpis <iliastsi@arrikto.com> Signed-off-by: Ilias Tsitsimpis <iliastsi@arrikto.com> Signed-off-by: Nikos Tsironis <ntsironis@arrikto.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
159 lines
4.8 KiB
C
159 lines
4.8 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* Copyright (C) 2019 Arrikto, Inc. All Rights Reserved.
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*/
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#ifndef DM_CLONE_METADATA_H
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#define DM_CLONE_METADATA_H
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#include "persistent-data/dm-block-manager.h"
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#include "persistent-data/dm-space-map-metadata.h"
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#define DM_CLONE_METADATA_BLOCK_SIZE DM_SM_METADATA_BLOCK_SIZE
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/*
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* The metadata device is currently limited in size.
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*/
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#define DM_CLONE_METADATA_MAX_SECTORS DM_SM_METADATA_MAX_SECTORS
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/*
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* A metadata device larger than 16GB triggers a warning.
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*/
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#define DM_CLONE_METADATA_MAX_SECTORS_WARNING (16 * (1024 * 1024 * 1024 >> SECTOR_SHIFT))
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#define SPACE_MAP_ROOT_SIZE 128
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/* dm-clone metadata */
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struct dm_clone_metadata;
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/*
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* Set region status to hydrated.
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*
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* @cmd: The dm-clone metadata
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* @region_nr: The region number
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*
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* This function doesn't block, so it's safe to call it from interrupt context.
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*/
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int dm_clone_set_region_hydrated(struct dm_clone_metadata *cmd, unsigned long region_nr);
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/*
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* Set status of all regions in the provided range to hydrated, if not already
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* hydrated.
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*
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* @cmd: The dm-clone metadata
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* @start: Starting region number
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* @nr_regions: Number of regions in the range
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*
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* This function doesn't block, so it's safe to call it from interrupt context.
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*/
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int dm_clone_cond_set_range(struct dm_clone_metadata *cmd, unsigned long start,
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unsigned long nr_regions);
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/*
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* Read existing or create fresh metadata.
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*
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* @bdev: The device storing the metadata
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* @target_size: The target size
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* @region_size: The region size
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*
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* @returns: The dm-clone metadata
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*
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* This function reads the superblock of @bdev and checks if it's all zeroes.
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* If it is, it formats @bdev and creates fresh metadata. If it isn't, it
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* validates the metadata stored in @bdev.
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*/
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struct dm_clone_metadata *dm_clone_metadata_open(struct block_device *bdev,
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sector_t target_size,
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sector_t region_size);
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/*
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* Free the resources related to metadata management.
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*/
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void dm_clone_metadata_close(struct dm_clone_metadata *cmd);
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/*
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* Commit dm-clone metadata to disk.
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*/
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int dm_clone_metadata_commit(struct dm_clone_metadata *cmd);
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/*
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* Reload the in core copy of the on-disk bitmap.
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*
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* This should be used after aborting a metadata transaction and setting the
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* metadata to read-only, to invalidate the in-core cache and make it match the
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* on-disk metadata.
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*
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* WARNING: It must not be called concurrently with either
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* dm_clone_set_region_hydrated() or dm_clone_cond_set_range(), as it updates
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* the region bitmap without taking the relevant spinlock. We don't take the
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* spinlock because dm_clone_reload_in_core_bitset() does I/O, so it may block.
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*
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* But, it's safe to use it after calling dm_clone_metadata_set_read_only(),
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* because the latter sets the metadata to read-only mode. Both
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* dm_clone_set_region_hydrated() and dm_clone_cond_set_range() refuse to touch
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* the region bitmap, after calling dm_clone_metadata_set_read_only().
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*/
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int dm_clone_reload_in_core_bitset(struct dm_clone_metadata *cmd);
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/*
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* Check whether dm-clone's metadata changed this transaction.
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*/
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bool dm_clone_changed_this_transaction(struct dm_clone_metadata *cmd);
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/*
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* Abort current metadata transaction and rollback metadata to the last
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* committed transaction.
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*/
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int dm_clone_metadata_abort(struct dm_clone_metadata *cmd);
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/*
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* Switches metadata to a read only mode. Once read-only mode has been entered
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* the following functions will return -EPERM:
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*
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* dm_clone_metadata_commit()
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* dm_clone_set_region_hydrated()
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* dm_clone_cond_set_range()
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* dm_clone_metadata_abort()
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*/
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void dm_clone_metadata_set_read_only(struct dm_clone_metadata *cmd);
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void dm_clone_metadata_set_read_write(struct dm_clone_metadata *cmd);
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/*
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* Returns true if the hydration of the destination device is finished.
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*/
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bool dm_clone_is_hydration_done(struct dm_clone_metadata *cmd);
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/*
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* Returns true if region @region_nr is hydrated.
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*/
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bool dm_clone_is_region_hydrated(struct dm_clone_metadata *cmd, unsigned long region_nr);
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/*
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* Returns true if all the regions in the range are hydrated.
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*/
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bool dm_clone_is_range_hydrated(struct dm_clone_metadata *cmd,
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unsigned long start, unsigned long nr_regions);
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/*
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* Returns the number of hydrated regions.
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*/
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unsigned long dm_clone_nr_of_hydrated_regions(struct dm_clone_metadata *cmd);
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/*
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* Returns the first unhydrated region with region_nr >= @start
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*/
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unsigned long dm_clone_find_next_unhydrated_region(struct dm_clone_metadata *cmd,
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unsigned long start);
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/*
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* Get the number of free metadata blocks.
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*/
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int dm_clone_get_free_metadata_block_count(struct dm_clone_metadata *cmd, dm_block_t *result);
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/*
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* Get the total number of metadata blocks.
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*/
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int dm_clone_get_metadata_dev_size(struct dm_clone_metadata *cmd, dm_block_t *result);
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#endif /* DM_CLONE_METADATA_H */
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