linux/drivers/md/dm-vdo/recovery-journal.h

/* SPDX-License-Identifier: GPL-2.0-only */
/*
 * Copyright 2023 Red Hat
 */

#ifndef VDO_RECOVERY_JOURNAL_H
#define VDO_RECOVERY_JOURNAL_H

#include <linux/list.h>

#include "numeric.h"

#include "admin-state.h"
#include "constants.h"
#include "encodings.h"
#include "flush.h"
#include "statistics.h"
#include "types.h"
#include "wait-queue.h"

/**
 * DOC: recovery journal.
 *
 * The recovery_journal provides a log of all block mapping and reference count changes which have
 * not yet been stably written to the block map or slab journals. This log helps to reduce the
 * write amplification of writes by providing amortization of slab journal and block map page
 * updates.
 *
 * The recovery journal has a single dedicated queue and thread for performing all journal updates.
 * The concurrency guarantees of this single-threaded model allow the code to omit more
 * fine-grained locking for recovery journal structures.
 *
 * The journal consists of a set of on-disk blocks arranged as a circular log with monotonically
 * increasing sequence numbers. Three sequence numbers serve to define the active extent of the
 * journal. The 'head' is the oldest active block in the journal. The 'tail' is the end of the
 * half-open interval containing the active blocks. 'active' is the number of the block actively
 * receiving entries. In an empty journal, head == active == tail. Once any entries are added, tail
 * = active + 1, and head may be any value in the interval [tail - size, active].
 *
 * The journal also contains a set of in-memory blocks which are used to buffer up entries until
 * they can be committed. In general the number of in-memory blocks ('tail_buffer_count') will be
 * less than the on-disk size. Each in-memory block is also a vdo_completion. Each in-memory block
 * has a vio which is used to commit that block to disk. The vio's data is the on-disk
 * representation of the journal block. In addition each in-memory block has a buffer which is used
 * to accumulate entries while a partial commit of the block is in progress. In-memory blocks are
 * kept on two rings. Free blocks live on the 'free_tail_blocks' ring. When a block becomes active
 * (see below) it is moved to the 'active_tail_blocks' ring. When a block is fully committed, it is
 * moved back to the 'free_tail_blocks' ring.
 *
 * When entries are added to the journal, they are added to the active in-memory block, as
 * indicated by the 'active_block' field. If the caller wishes to wait for the entry to be
 * committed, the requesting VIO will be attached to the in-memory block to which the caller's
 * entry was added. If the caller does wish to wait, or if the entry filled the active block, an
 * attempt will be made to commit that block to disk. If there is already another commit in
 * progress, the attempt will be ignored and then automatically retried when the in-progress commit
 * completes. If there is no commit in progress, any data_vios waiting on the block are transferred
 * to the block's vio which is then written, automatically waking all of the waiters when it
 * completes. When the write completes, any entries which accumulated in the block are copied to
 * the vio's data buffer.
 *
 * Finally, the journal maintains a set of counters, one for each on disk journal block. These
 * counters are used as locks to prevent premature reaping of journal blocks. Each time a new
 * sequence number is used, the counter for the corresponding block is incremented. The counter is
 * subsequently decremented when that block is filled and then committed for the last time. This
 * prevents blocks from being reaped while they are still being updated. The counter is also
 * incremented once for each entry added to a block, and decremented once each time the block map
 * is updated in memory for that request. This prevents blocks from being reaped while their VIOs
 * are still active. Finally, each in-memory block map page tracks the oldest journal block that
 * contains entries corresponding to uncommitted updates to that block map page. Each time an
 * in-memory block map page is updated, it checks if the journal block for the VIO is earlier than
 * the one it references, in which case it increments the count on the earlier journal block and
 * decrements the count on the later journal block, maintaining a lock on the oldest journal block
 * containing entries for that page. When a block map page has been flushed from the cache, the
 * counter for the journal block it references is decremented. Whenever the counter for the head
 * block goes to 0, the head is advanced until it comes to a block whose counter is not 0 or until
 * it reaches the active block. This is the mechanism for reclaiming journal space on disk.
 *
 * If there is no in-memory space when a VIO attempts to add an entry, the VIO will be attached to
 * the 'commit_completion' and will be woken the next time a full block has committed. If there is
 * no on-disk space when a VIO attempts to add an entry, the VIO will be attached to the
 * 'reap_completion', and will be woken the next time a journal block is reaped.
 */

enum vdo_zone_type {
	VDO_ZONE_TYPE_ADMIN,
	VDO_ZONE_TYPE_JOURNAL,
	VDO_ZONE_TYPE_LOGICAL,
	VDO_ZONE_TYPE_PHYSICAL,
};

struct lock_counter {
	/* The completion for notifying the owner of a lock release */
	struct vdo_completion completion;
	/* The number of logical zones which may hold locks */
	zone_count_t logical_zones;
	/* The number of physical zones which may hold locks */
	zone_count_t physical_zones;
	/* The number of locks */
	block_count_t locks;
	/* Whether the lock release notification is in flight */
	atomic_t state;
	/* The number of logical zones which hold each lock */
	atomic_t *logical_zone_counts;
	/* The number of physical zones which hold each lock */
	atomic_t *physical_zone_counts;
	/* The per-lock counts for the journal zone */
	u16 *journal_counters;
	/* The per-lock decrement counts for the journal zone */
	atomic_t *journal_decrement_counts;
	/* The per-zone, per-lock reference counts for logical zones */
	u16 *logical_counters;
	/* The per-zone, per-lock reference counts for physical zones */
	u16 *physical_counters;
};

struct recovery_journal_block {
	/* The doubly linked pointers for the free or active lists */
	struct list_head list_node;
	/* The waiter for the pending full block list */
	struct vdo_waiter write_waiter;
	/* The journal to which this block belongs */
	struct recovery_journal *journal;
	/* A pointer to the current sector in the packed block buffer */
	struct packed_journal_sector *sector;
	/* The vio for writing this block */
	struct vio vio;
	/* The sequence number for this block */
	sequence_number_t sequence_number;
	/* The location of this block in the on-disk journal */
	physical_block_number_t block_number;
	/* Whether this block is being committed */
	bool committing;
	/* The total number of entries in this block */
	journal_entry_count_t entry_count;
	/* The total number of uncommitted entries (queued or committing) */
	journal_entry_count_t uncommitted_entry_count;
	/* The number of new entries in the current commit */
	journal_entry_count_t entries_in_commit;
	/* The queue of vios which will make entries for the next commit */
	struct vdo_wait_queue entry_waiters;
	/* The queue of vios waiting for the current commit */
	struct vdo_wait_queue commit_waiters;
};

struct recovery_journal {
	/* The thread ID of the journal zone */
	thread_id_t thread_id;
	/* The slab depot which can hold locks on this journal */
	struct slab_depot *depot;
	/* The block map which can hold locks on this journal */
	struct block_map *block_map;
	/* The queue of vios waiting to make entries */
	struct vdo_wait_queue entry_waiters;
	/* The number of free entries in the journal */
	u64 available_space;
	/* The number of decrement entries which need to be made */
	data_vio_count_t pending_decrement_count;
	/* Whether the journal is adding entries from the increment or decrement waiters queues */
	bool adding_entries;
	/* The administrative state of the journal */
	struct admin_state state;
	/* Whether a reap is in progress */
	bool reaping;
	/* The location of the first journal block */
	physical_block_number_t origin;
	/* The oldest active block in the journal on disk for block map rebuild */
	sequence_number_t block_map_head;
	/* The oldest active block in the journal on disk for slab journal replay */
	sequence_number_t slab_journal_head;
	/* The newest block in the journal on disk to which a write has finished */
	sequence_number_t last_write_acknowledged;
	/* The end of the half-open interval of the active journal */
	sequence_number_t tail;
	/* The point at which the last entry will have been added */
	struct journal_point append_point;
	/* The journal point of the vio most recently released from the journal */
	struct journal_point commit_point;
	/* The nonce of the VDO */
	nonce_t nonce;
	/* The number of recoveries completed by the VDO */
	u8 recovery_count;
	/* The number of entries which fit in a single block */
	journal_entry_count_t entries_per_block;
	/* Unused in-memory journal blocks */
	struct list_head free_tail_blocks;
	/* In-memory journal blocks with records */
	struct list_head active_tail_blocks;
	/* A pointer to the active block (the one we are adding entries to now) */
	struct recovery_journal_block *active_block;
	/* Journal blocks that need writing */
	struct vdo_wait_queue pending_writes;
	/* The new block map reap head after reaping */
	sequence_number_t block_map_reap_head;
	/* The head block number for the block map rebuild range */
	block_count_t block_map_head_block_number;
	/* The new slab journal reap head after reaping */
	sequence_number_t slab_journal_reap_head;
	/* The head block number for the slab journal replay range */
	block_count_t slab_journal_head_block_number;
	/* The data-less vio, usable only for flushing */
	struct vio *flush_vio;
	/* The number of blocks in the on-disk journal */
	block_count_t size;
	/* The number of logical blocks that are in-use */
	block_count_t logical_blocks_used;
	/* The number of block map pages that are allocated */
	block_count_t block_map_data_blocks;
	/* The number of journal blocks written but not yet acknowledged */
	block_count_t pending_write_count;
	/* The threshold at which slab journal tail blocks will be written out */
	block_count_t slab_journal_commit_threshold;
	/* Counters for events in the journal that are reported as statistics */
	struct recovery_journal_statistics events;
	/* The locks for each on-disk block */
	struct lock_counter lock_counter;
	/* The tail blocks */
	struct recovery_journal_block blocks[];
};

/**
 * vdo_get_recovery_journal_block_number() - Get the physical block number for a given sequence
 *                                           number.
 * @journal: The journal.
 * @sequence: The sequence number of the desired block.
 *
 * Return: The block number corresponding to the sequence number.
 */
static inline physical_block_number_t __must_check
vdo_get_recovery_journal_block_number(const struct recovery_journal *journal,
				      sequence_number_t sequence)
{
	/*
	 * Since journal size is a power of two, the block number modulus can just be extracted
	 * from the low-order bits of the sequence.
	 */
	return vdo_compute_recovery_journal_block_number(journal->size, sequence);
}

/**
 * vdo_compute_recovery_journal_check_byte() - Compute the check byte for a given sequence number.
 * @journal: The journal.
 * @sequence: The sequence number.
 *
 * Return: The check byte corresponding to the sequence number.
 */
static inline u8 __must_check
vdo_compute_recovery_journal_check_byte(const struct recovery_journal *journal,
					sequence_number_t sequence)
{
	/* The check byte must change with each trip around the journal. */
	return (((sequence / journal->size) & 0x7F) | 0x80);
}

int __must_check vdo_decode_recovery_journal(struct recovery_journal_state_7_0 state,
					     nonce_t nonce, struct vdo *vdo,
					     struct partition *partition,
					     u64 recovery_count,
					     block_count_t journal_size,
					     struct recovery_journal **journal_ptr);

void vdo_free_recovery_journal(struct recovery_journal *journal);

void vdo_initialize_recovery_journal_post_repair(struct recovery_journal *journal,
						 u64 recovery_count,
						 sequence_number_t tail,
						 block_count_t logical_blocks_used,
						 block_count_t block_map_data_blocks);

block_count_t __must_check
vdo_get_journal_block_map_data_blocks_used(struct recovery_journal *journal);

thread_id_t __must_check vdo_get_recovery_journal_thread_id(struct recovery_journal *journal);

void vdo_open_recovery_journal(struct recovery_journal *journal,
			       struct slab_depot *depot, struct block_map *block_map);

sequence_number_t
vdo_get_recovery_journal_current_sequence_number(struct recovery_journal *journal);

block_count_t __must_check vdo_get_recovery_journal_length(block_count_t journal_size);

struct recovery_journal_state_7_0 __must_check
vdo_record_recovery_journal(const struct recovery_journal *journal);

void vdo_add_recovery_journal_entry(struct recovery_journal *journal,
				    struct data_vio *data_vio);

void vdo_acquire_recovery_journal_block_reference(struct recovery_journal *journal,
						  sequence_number_t sequence_number,
						  enum vdo_zone_type zone_type,
						  zone_count_t zone_id);

void vdo_release_recovery_journal_block_reference(struct recovery_journal *journal,
						  sequence_number_t sequence_number,
						  enum vdo_zone_type zone_type,
						  zone_count_t zone_id);

void vdo_release_journal_entry_lock(struct recovery_journal *journal,
				    sequence_number_t sequence_number);

void vdo_drain_recovery_journal(struct recovery_journal *journal,
				const struct admin_state_code *operation,
				struct vdo_completion *parent);

void vdo_resume_recovery_journal(struct recovery_journal *journal,
				 struct vdo_completion *parent);

block_count_t __must_check
vdo_get_recovery_journal_logical_blocks_used(const struct recovery_journal *journal);

struct recovery_journal_statistics __must_check
vdo_get_recovery_journal_statistics(const struct recovery_journal *journal);

void vdo_dump_recovery_journal_statistics(const struct recovery_journal *journal);

#endif /* VDO_RECOVERY_JOURNAL_H */