fs/bcachefs/journal.h - pub/scm/linux/kernel/git/wireless/wireless-testing - Git at Google

 /* SPDX-License-Identifier: GPL-2.0 */
 #ifndef _BCACHEFS_JOURNAL_H
 #define _BCACHEFS_JOURNAL_H

 /*
  * THE JOURNAL:
  *
  * The primary purpose of the journal is to log updates (insertions) to the
  * b-tree, to avoid having to do synchronous updates to the b-tree on disk.
  *
  * Without the journal, the b-tree is always internally consistent on
  * disk - and in fact, in the earliest incarnations bcache didn't have a journal
  * but did handle unclean shutdowns by doing all index updates synchronously
  * (with coalescing).
  *
  * Updates to interior nodes still happen synchronously and without the journal
  * (for simplicity) - this may change eventually but updates to interior nodes
  * are rare enough it's not a huge priority.
  *
  * This means the journal is relatively separate from the b-tree; it consists of
  * just a list of keys and journal replay consists of just redoing those
  * insertions in same order that they appear in the journal.
  *
  * PERSISTENCE:
  *
  * For synchronous updates (where we're waiting on the index update to hit
  * disk), the journal entry will be written out immediately (or as soon as
  * possible, if the write for the previous journal entry was still in flight).
  *
  * Synchronous updates are specified by passing a closure (@flush_cl) to
  * bch2_btree_insert() or bch_btree_insert_node(), which then pass that parameter
  * down to the journalling code. That closure will wait on the journal write to
  * complete (via closure_wait()).
  *
  * If the index update wasn't synchronous, the journal entry will be
  * written out after 10 ms have elapsed, by default (the delay_ms field
  * in struct journal).
  *
  * JOURNAL ENTRIES:
  *
  * A journal entry is variable size (struct jset), it's got a fixed length
  * header and then a variable number of struct jset_entry entries.
  *
  * Journal entries are identified by monotonically increasing 64 bit sequence
  * numbers - jset->seq; other places in the code refer to this sequence number.
  *
  * A jset_entry entry contains one or more bkeys (which is what gets inserted
  * into the b-tree). We need a container to indicate which b-tree the key is
  * for; also, the roots of the various b-trees are stored in jset_entry entries
  * (one for each b-tree) - this lets us add new b-tree types without changing
  * the on disk format.
  *
  * We also keep some things in the journal header that are logically part of the
  * superblock - all the things that are frequently updated. This is for future
  * bcache on raw flash support; the superblock (which will become another
  * journal) can't be moved or wear leveled, so it contains just enough
  * information to find the main journal, and the superblock only has to be
  * rewritten when we want to move/wear level the main journal.
  *
  * JOURNAL LAYOUT ON DISK:
  *
  * The journal is written to a ringbuffer of buckets (which is kept in the
  * superblock); the individual buckets are not necessarily contiguous on disk
  * which means that journal entries are not allowed to span buckets, but also
  * that we can resize the journal at runtime if desired (unimplemented).
  *
  * The journal buckets exist in the same pool as all the other buckets that are
  * managed by the allocator and garbage collection - garbage collection marks
  * the journal buckets as metadata buckets.
  *
  * OPEN/DIRTY JOURNAL ENTRIES:
  *
  * Open/dirty journal entries are journal entries that contain b-tree updates
  * that have not yet been written out to the b-tree on disk. We have to track
  * which journal entries are dirty, and we also have to avoid wrapping around
  * the journal and overwriting old but still dirty journal entries with new
  * journal entries.
  *
  * On disk, this is represented with the "last_seq" field of struct jset;
  * last_seq is the first sequence number that journal replay has to replay.
  *
  * To avoid overwriting dirty journal entries on disk, we keep a mapping (in
  * journal_device->seq) of for each journal bucket, the highest sequence number
  * any journal entry it contains. Then, by comparing that against last_seq we
  * can determine whether that journal bucket contains dirty journal entries or
  * not.
  *
  * To track which journal entries are dirty, we maintain a fifo of refcounts
  * (where each entry corresponds to a specific sequence number) - when a ref
  * goes to 0, that journal entry is no longer dirty.
  *
  * Journalling of index updates is done at the same time as the b-tree itself is
  * being modified (see btree_insert_key()); when we add the key to the journal
  * the pending b-tree write takes a ref on the journal entry the key was added
  * to. If a pending b-tree write would need to take refs on multiple dirty
  * journal entries, it only keeps the ref on the oldest one (since a newer
  * journal entry will still be replayed if an older entry was dirty).
  *
  * JOURNAL FILLING UP:
  *
  * There are two ways the journal could fill up; either we could run out of
  * space to write to, or we could have too many open journal entries and run out
  * of room in the fifo of refcounts. Since those refcounts are decremented
  * without any locking we can't safely resize that fifo, so we handle it the
  * same way.
  *
  * If the journal fills up, we start flushing dirty btree nodes until we can
  * allocate space for a journal write again - preferentially flushing btree
  * nodes that are pinning the oldest journal entries first.
  */

 #include <linux/hash.h>

 #include "journal_types.h"

 struct bch_fs;

 static inline void journal_wake(struct journal *j)
 {
 	wake_up(&j->wait);
 	closure_wake_up(&j->async_wait);
 }

 /* Sequence number of oldest dirty journal entry */

 static inline u64 journal_last_seq(struct journal *j)
 {
 	return j->pin.front;
 }

 static inline u64 journal_cur_seq(struct journal *j)
 {
 	return atomic64_read(&j->seq);
 }

 static inline u64 journal_last_unwritten_seq(struct journal *j)
 {
 	return j->seq_ondisk + 1;
 }

 static inline struct journal_buf *journal_cur_buf(struct journal *j)
 {
 	unsigned idx = (journal_cur_seq(j) &
 			JOURNAL_BUF_MASK &
 			~JOURNAL_STATE_BUF_MASK) + j->reservations.idx;

 	return j->buf + idx;
 }

 static inline int journal_state_count(union journal_res_state s, int idx)
 {
 	switch (idx) {
 	case 0: return s.buf0_count;
 	case 1: return s.buf1_count;
 	case 2: return s.buf2_count;
 	case 3: return s.buf3_count;
 	}
 	BUG();
 }

 static inline int journal_state_seq_count(struct journal *j,
 					  union journal_res_state s, u64 seq)
 {
 	if (journal_cur_seq(j) - seq < JOURNAL_STATE_BUF_NR)
 		return journal_state_count(s, seq & JOURNAL_STATE_BUF_MASK);
 	else
 		return 0;
 }

 static inline void journal_state_inc(union journal_res_state *s)
 {
 	s->buf0_count += s->idx == 0;
 	s->buf1_count += s->idx == 1;
 	s->buf2_count += s->idx == 2;
 	s->buf3_count += s->idx == 3;
 }

 /*
  * Amount of space that will be taken up by some keys in the journal (i.e.
  * including the jset header)
  */
 static inline unsigned jset_u64s(unsigned u64s)
 {
 	return u64s + sizeof(struct jset_entry) / sizeof(u64);
 }

 static inline int journal_entry_overhead(struct journal *j)
 {
 	return sizeof(struct jset) / sizeof(u64) + j->entry_u64s_reserved;
 }

 static inline struct jset_entry *
 bch2_journal_add_entry_noreservation(struct journal_buf *buf, size_t u64s)
 {
 	struct jset *jset = buf->data;
 	struct jset_entry *entry = vstruct_idx(jset, le32_to_cpu(jset->u64s));

 	memset(entry, 0, sizeof(*entry));
 	entry->u64s = cpu_to_le16(u64s);

 	le32_add_cpu(&jset->u64s, jset_u64s(u64s));

 	return entry;
 }

 static inline struct jset_entry *
 journal_res_entry(struct journal *j, struct journal_res *res)
 {
 	return vstruct_idx(j->buf[res->seq & JOURNAL_BUF_MASK].data, res->offset);
 }

 static inline unsigned journal_entry_init(struct jset_entry *entry, unsigned type,
 					  enum btree_id id, unsigned level,
 					  unsigned u64s)
 {
 	entry->u64s	= cpu_to_le16(u64s);
 	entry->btree_id = id;
 	entry->level	= level;
 	entry->type	= type;
 	entry->pad[0]	= 0;
 	entry->pad[1]	= 0;
 	entry->pad[2]	= 0;
 	return jset_u64s(u64s);
 }

 static inline unsigned journal_entry_set(struct jset_entry *entry, unsigned type,
 					  enum btree_id id, unsigned level,
 					  const void *data, unsigned u64s)
 {
 	unsigned ret = journal_entry_init(entry, type, id, level, u64s);

 	memcpy_u64s_small(entry->_data, data, u64s);
 	return ret;
 }

 static inline struct jset_entry *
 bch2_journal_add_entry(struct journal *j, struct journal_res *res,
 			 unsigned type, enum btree_id id,
 			 unsigned level, unsigned u64s)
 {
 	struct jset_entry *entry = journal_res_entry(j, res);
 	unsigned actual = journal_entry_init(entry, type, id, level, u64s);

 	EBUG_ON(!res->ref);
 	EBUG_ON(actual > res->u64s);

 	res->offset	+= actual;
 	res->u64s	-= actual;
 	return entry;
 }

 static inline bool journal_entry_empty(struct jset *j)
 {
 	if (j->seq != j->last_seq)
 		return false;

 	vstruct_for_each(j, i)
 		if (i->type == BCH_JSET_ENTRY_btree_keys && i->u64s)
 			return false;
 	return true;
 }

 /*
  * Drop reference on a buffer index and return true if the count has hit zero.
  */
 static inline union journal_res_state journal_state_buf_put(struct journal *j, unsigned idx)
 {
 	union journal_res_state s;

 	s.v = atomic64_sub_return(((union journal_res_state) {
 				    .buf0_count = idx == 0,
 				    .buf1_count = idx == 1,
 				    .buf2_count = idx == 2,
 				    .buf3_count = idx == 3,
 				    }).v, &j->reservations.counter);
 	return s;
 }

 bool bch2_journal_entry_close(struct journal *);
 void bch2_journal_do_writes(struct journal *);
 void bch2_journal_buf_put_final(struct journal *, u64);

 static inline void __bch2_journal_buf_put(struct journal *j, u64 seq)
 {
 	unsigned idx = seq & JOURNAL_STATE_BUF_MASK;
 	union journal_res_state s;

 	s = journal_state_buf_put(j, idx);
 	if (!journal_state_count(s, idx))
 		bch2_journal_buf_put_final(j, seq);
 }

 static inline void bch2_journal_buf_put(struct journal *j, u64 seq)
 {
 	unsigned idx = seq & JOURNAL_STATE_BUF_MASK;
 	union journal_res_state s;

 	s = journal_state_buf_put(j, idx);
 	if (!journal_state_count(s, idx)) {
 		spin_lock(&j->lock);
 		bch2_journal_buf_put_final(j, seq);
 		spin_unlock(&j->lock);
 	} else if (unlikely(s.cur_entry_offset == JOURNAL_ENTRY_BLOCKED_VAL))
 		wake_up(&j->wait);
 }

 /*
  * This function releases the journal write structure so other threads can
  * then proceed to add their keys as well.
  */
 static inline void bch2_journal_res_put(struct journal *j,
 				       struct journal_res *res)
 {
 	if (!res->ref)
 		return;

 	lock_release(&j->res_map, _THIS_IP_);

 	while (res->u64s)
 		bch2_journal_add_entry(j, res,
 				       BCH_JSET_ENTRY_btree_keys,
 				       0, 0, 0);

 	bch2_journal_buf_put(j, res->seq);

 	res->ref = 0;
 }

 int bch2_journal_res_get_slowpath(struct journal *, struct journal_res *,
 				  unsigned, struct btree_trans *);

 /* First bits for BCH_WATERMARK: */
 enum journal_res_flags {
 	__JOURNAL_RES_GET_NONBLOCK	= BCH_WATERMARK_BITS,
 	__JOURNAL_RES_GET_CHECK,
 };

 #define JOURNAL_RES_GET_NONBLOCK	(1 << __JOURNAL_RES_GET_NONBLOCK)
 #define JOURNAL_RES_GET_CHECK		(1 << __JOURNAL_RES_GET_CHECK)

 static inline int journal_res_get_fast(struct journal *j,
 				       struct journal_res *res,
 				       unsigned flags)
 {
 	union journal_res_state old, new;

 	old.v = atomic64_read(&j->reservations.counter);
 	do {
 		new.v = old.v;

 		/*
 		 * Check if there is still room in the current journal
 		 * entry, smp_rmb() guarantees that reads from reservations.counter
 		 * occur before accessing cur_entry_u64s:
 		 */
 		smp_rmb();
 		if (new.cur_entry_offset + res->u64s > j->cur_entry_u64s)
 			return 0;

 		EBUG_ON(!journal_state_count(new, new.idx));

 		if ((flags & BCH_WATERMARK_MASK) < j->watermark)
 			return 0;

 		new.cur_entry_offset += res->u64s;
 		journal_state_inc(&new);

 		/*
 		 * If the refcount would overflow, we have to wait:
 		 * XXX - tracepoint this:
 		 */
 		if (!journal_state_count(new, new.idx))
 			return 0;

 		if (flags & JOURNAL_RES_GET_CHECK)
 			return 1;
 	} while (!atomic64_try_cmpxchg(&j->reservations.counter,
 				       &old.v, new.v));

 	res->ref	= true;
 	res->offset	= old.cur_entry_offset;
 	res->seq	= journal_cur_seq(j);
 	res->seq -= (res->seq - old.idx) & JOURNAL_STATE_BUF_MASK;
 	return 1;
 }

 static inline int bch2_journal_res_get(struct journal *j, struct journal_res *res,
 				       unsigned u64s, unsigned flags,
 				       struct btree_trans *trans)
 {
 	int ret;

 	EBUG_ON(res->ref);
 	EBUG_ON(!test_bit(JOURNAL_running, &j->flags));

 	res->u64s = u64s;

 	if (journal_res_get_fast(j, res, flags))
 		goto out;

 	ret = bch2_journal_res_get_slowpath(j, res, flags, trans);
 	if (ret)
 		return ret;
 out:
 	if (!(flags & JOURNAL_RES_GET_CHECK)) {
 		lock_acquire_shared(&j->res_map, 0,
 				    (flags & JOURNAL_RES_GET_NONBLOCK) != 0,
 				    NULL, _THIS_IP_);
 		EBUG_ON(!res->ref);
 		BUG_ON(!res->seq);
 	}
 	return 0;
 }

 /* journal_entry_res: */

 void bch2_journal_entry_res_resize(struct journal *,
 				   struct journal_entry_res *,
 				   unsigned);

 int bch2_journal_flush_seq_async(struct journal *, u64, struct closure *);
 void bch2_journal_flush_async(struct journal *, struct closure *);

 int bch2_journal_flush_seq(struct journal *, u64, unsigned);
 int bch2_journal_flush(struct journal *);
 bool bch2_journal_noflush_seq(struct journal *, u64, u64);
 int bch2_journal_meta(struct journal *);

 void bch2_journal_halt_locked(struct journal *);
 void bch2_journal_halt(struct journal *);

 static inline int bch2_journal_error(struct journal *j)
 {
 	return j->reservations.cur_entry_offset == JOURNAL_ENTRY_ERROR_VAL
 		? -BCH_ERR_journal_shutdown : 0;
 }

 struct bch_dev;

 void bch2_journal_unblock(struct journal *);
 void bch2_journal_block(struct journal *);
 struct journal_buf *bch2_next_write_buffer_flush_journal_buf(struct journal *, u64, bool *);

 void __bch2_journal_debug_to_text(struct printbuf *, struct journal *);
 void bch2_journal_debug_to_text(struct printbuf *, struct journal *);

 int bch2_set_nr_journal_buckets(struct bch_fs *, struct bch_dev *, unsigned);
 int bch2_dev_journal_bucket_delete(struct bch_dev *, u64);

 int bch2_dev_journal_alloc(struct bch_dev *, bool);
 int bch2_fs_journal_alloc(struct bch_fs *);

 void bch2_dev_journal_stop(struct journal *, struct bch_dev *);

 void bch2_fs_journal_stop(struct journal *);
 int bch2_fs_journal_start(struct journal *, u64, u64);
 void bch2_journal_set_replay_done(struct journal *);

 void bch2_dev_journal_exit(struct bch_dev *);
 int bch2_dev_journal_init(struct bch_dev *, struct bch_sb *);
 void bch2_fs_journal_exit(struct journal *);
 void bch2_fs_journal_init_early(struct journal *);
 int bch2_fs_journal_init(struct journal *);

 #endif /* _BCACHEFS_JOURNAL_H */
	/* SPDX-License-Identifier: GPL-2.0 */
	#ifndef _BCACHEFS_JOURNAL_H
	#define _BCACHEFS_JOURNAL_H

	/*
	* THE JOURNAL:
	*
	* The primary purpose of the journal is to log updates (insertions) to the
	* b-tree, to avoid having to do synchronous updates to the b-tree on disk.
	*
	* Without the journal, the b-tree is always internally consistent on
	* disk - and in fact, in the earliest incarnations bcache didn't have a journal
	* but did handle unclean shutdowns by doing all index updates synchronously
	* (with coalescing).
	*
	* Updates to interior nodes still happen synchronously and without the journal
	* (for simplicity) - this may change eventually but updates to interior nodes
	* are rare enough it's not a huge priority.
	*
	* This means the journal is relatively separate from the b-tree; it consists of
	* just a list of keys and journal replay consists of just redoing those
	* insertions in same order that they appear in the journal.
	*
	* PERSISTENCE:
	*
	* For synchronous updates (where we're waiting on the index update to hit
	* disk), the journal entry will be written out immediately (or as soon as
	* possible, if the write for the previous journal entry was still in flight).
	*
	* Synchronous updates are specified by passing a closure (@flush_cl) to
	* bch2_btree_insert() or bch_btree_insert_node(), which then pass that parameter
	* down to the journalling code. That closure will wait on the journal write to
	* complete (via closure_wait()).
	*
	* If the index update wasn't synchronous, the journal entry will be
	* written out after 10 ms have elapsed, by default (the delay_ms field
	* in struct journal).
	*
	* JOURNAL ENTRIES:
	*
	* A journal entry is variable size (struct jset), it's got a fixed length
	* header and then a variable number of struct jset_entry entries.
	*
	* Journal entries are identified by monotonically increasing 64 bit sequence
	* numbers - jset->seq; other places in the code refer to this sequence number.
	*
	* A jset_entry entry contains one or more bkeys (which is what gets inserted
	* into the b-tree). We need a container to indicate which b-tree the key is
	* for; also, the roots of the various b-trees are stored in jset_entry entries
	* (one for each b-tree) - this lets us add new b-tree types without changing
	* the on disk format.
	*
	* We also keep some things in the journal header that are logically part of the
	* superblock - all the things that are frequently updated. This is for future
	* bcache on raw flash support; the superblock (which will become another
	* journal) can't be moved or wear leveled, so it contains just enough
	* information to find the main journal, and the superblock only has to be
	* rewritten when we want to move/wear level the main journal.
	*
	* JOURNAL LAYOUT ON DISK:
	*
	* The journal is written to a ringbuffer of buckets (which is kept in the
	* superblock); the individual buckets are not necessarily contiguous on disk
	* which means that journal entries are not allowed to span buckets, but also
	* that we can resize the journal at runtime if desired (unimplemented).
	*
	* The journal buckets exist in the same pool as all the other buckets that are
	* managed by the allocator and garbage collection - garbage collection marks
	* the journal buckets as metadata buckets.
	*
	* OPEN/DIRTY JOURNAL ENTRIES:
	*
	* Open/dirty journal entries are journal entries that contain b-tree updates
	* that have not yet been written out to the b-tree on disk. We have to track
	* which journal entries are dirty, and we also have to avoid wrapping around
	* the journal and overwriting old but still dirty journal entries with new
	* journal entries.
	*
	* On disk, this is represented with the "last_seq" field of struct jset;
	* last_seq is the first sequence number that journal replay has to replay.
	*
	* To avoid overwriting dirty journal entries on disk, we keep a mapping (in
	* journal_device->seq) of for each journal bucket, the highest sequence number
	* any journal entry it contains. Then, by comparing that against last_seq we
	* can determine whether that journal bucket contains dirty journal entries or
	* not.
	*
	* To track which journal entries are dirty, we maintain a fifo of refcounts
	* (where each entry corresponds to a specific sequence number) - when a ref
	* goes to 0, that journal entry is no longer dirty.
	*
	* Journalling of index updates is done at the same time as the b-tree itself is
	* being modified (see btree_insert_key()); when we add the key to the journal
	* the pending b-tree write takes a ref on the journal entry the key was added
	* to. If a pending b-tree write would need to take refs on multiple dirty
	* journal entries, it only keeps the ref on the oldest one (since a newer
	* journal entry will still be replayed if an older entry was dirty).
	*
	* JOURNAL FILLING UP:
	*
	* There are two ways the journal could fill up; either we could run out of
	* space to write to, or we could have too many open journal entries and run out
	* of room in the fifo of refcounts. Since those refcounts are decremented
	* without any locking we can't safely resize that fifo, so we handle it the
	* same way.
	*
	* If the journal fills up, we start flushing dirty btree nodes until we can
	* allocate space for a journal write again - preferentially flushing btree
	* nodes that are pinning the oldest journal entries first.
	*/

	#include <linux/hash.h>

	#include "journal_types.h"

	struct bch_fs;

	static inline void journal_wake(struct journal *j)
	{
	wake_up(&j->wait);
	closure_wake_up(&j->async_wait);
	}

	/* Sequence number of oldest dirty journal entry */

	static inline u64 journal_last_seq(struct journal *j)
	{
	return j->pin.front;
	}

	static inline u64 journal_cur_seq(struct journal *j)
	{
	return atomic64_read(&j->seq);
	}

	static inline u64 journal_last_unwritten_seq(struct journal *j)
	{
	return j->seq_ondisk + 1;
	}

	static inline struct journal_buf journal_cur_buf(struct journal j)
	{
	unsigned idx = (journal_cur_seq(j) &
	JOURNAL_BUF_MASK &
	~JOURNAL_STATE_BUF_MASK) + j->reservations.idx;

	return j->buf + idx;
	}

	static inline int journal_state_count(union journal_res_state s, int idx)
	{
	switch (idx) {
	case 0: return s.buf0_count;
	case 1: return s.buf1_count;
	case 2: return s.buf2_count;
	case 3: return s.buf3_count;
	}
	BUG();
	}

	static inline int journal_state_seq_count(struct journal *j,
	union journal_res_state s, u64 seq)
	{
	if (journal_cur_seq(j) - seq < JOURNAL_STATE_BUF_NR)
	return journal_state_count(s, seq & JOURNAL_STATE_BUF_MASK);
	else
	return 0;
	}

	static inline void journal_state_inc(union journal_res_state *s)
	{
	s->buf0_count += s->idx == 0;
	s->buf1_count += s->idx == 1;
	s->buf2_count += s->idx == 2;
	s->buf3_count += s->idx == 3;
	}

	/*
	* Amount of space that will be taken up by some keys in the journal (i.e.
	* including the jset header)
	*/
	static inline unsigned jset_u64s(unsigned u64s)
	{
	return u64s + sizeof(struct jset_entry) / sizeof(u64);
	}

	static inline int journal_entry_overhead(struct journal *j)
	{
	return sizeof(struct jset) / sizeof(u64) + j->entry_u64s_reserved;
	}

	static inline struct jset_entry *
	bch2_journal_add_entry_noreservation(struct journal_buf *buf, size_t u64s)
	{
	struct jset *jset = buf->data;
	struct jset_entry *entry = vstruct_idx(jset, le32_to_cpu(jset->u64s));

	memset(entry, 0, sizeof(*entry));
	entry->u64s = cpu_to_le16(u64s);

	le32_add_cpu(&jset->u64s, jset_u64s(u64s));

	return entry;
	}

	static inline struct jset_entry *
	journal_res_entry(struct journal j, struct journal_res res)
	{
	return vstruct_idx(j->buf[res->seq & JOURNAL_BUF_MASK].data, res->offset);
	}

	static inline unsigned journal_entry_init(struct jset_entry *entry, unsigned type,
	enum btree_id id, unsigned level,
	unsigned u64s)
	{
	entry->u64s = cpu_to_le16(u64s);
	entry->btree_id = id;
	entry->level = level;
	entry->type = type;
	entry->pad[0] = 0;
	entry->pad[1] = 0;
	entry->pad[2] = 0;
	return jset_u64s(u64s);
	}

	static inline unsigned journal_entry_set(struct jset_entry *entry, unsigned type,
	enum btree_id id, unsigned level,
	const void *data, unsigned u64s)
	{
	unsigned ret = journal_entry_init(entry, type, id, level, u64s);

	memcpy_u64s_small(entry->_data, data, u64s);
	return ret;
	}

	static inline struct jset_entry *
	bch2_journal_add_entry(struct journal j, struct journal_res res,
	unsigned type, enum btree_id id,
	unsigned level, unsigned u64s)
	{
	struct jset_entry *entry = journal_res_entry(j, res);
	unsigned actual = journal_entry_init(entry, type, id, level, u64s);

	EBUG_ON(!res->ref);
	EBUG_ON(actual > res->u64s);

	res->offset += actual;
	res->u64s -= actual;
	return entry;
	}

	static inline bool journal_entry_empty(struct jset *j)
	{
	if (j->seq != j->last_seq)
	return false;

	vstruct_for_each(j, i)
	if (i->type == BCH_JSET_ENTRY_btree_keys && i->u64s)
	return false;
	return true;
	}

	/*
	* Drop reference on a buffer index and return true if the count has hit zero.
	*/
	static inline union journal_res_state journal_state_buf_put(struct journal *j, unsigned idx)
	{
	union journal_res_state s;

	s.v = atomic64_sub_return(((union journal_res_state) {
	.buf0_count = idx == 0,
	.buf1_count = idx == 1,
	.buf2_count = idx == 2,
	.buf3_count = idx == 3,
	}).v, &j->reservations.counter);
	return s;
	}

	bool bch2_journal_entry_close(struct journal *);
	void bch2_journal_do_writes(struct journal *);
	void bch2_journal_buf_put_final(struct journal *, u64);

	static inline void __bch2_journal_buf_put(struct journal *j, u64 seq)
	{
	unsigned idx = seq & JOURNAL_STATE_BUF_MASK;
	union journal_res_state s;

	s = journal_state_buf_put(j, idx);
	if (!journal_state_count(s, idx))
	bch2_journal_buf_put_final(j, seq);
	}

	static inline void bch2_journal_buf_put(struct journal *j, u64 seq)
	{
	unsigned idx = seq & JOURNAL_STATE_BUF_MASK;
	union journal_res_state s;

	s = journal_state_buf_put(j, idx);
	if (!journal_state_count(s, idx)) {
	spin_lock(&j->lock);
	bch2_journal_buf_put_final(j, seq);
	spin_unlock(&j->lock);
	} else if (unlikely(s.cur_entry_offset == JOURNAL_ENTRY_BLOCKED_VAL))
	wake_up(&j->wait);
	}

	/*
	* This function releases the journal write structure so other threads can
	* then proceed to add their keys as well.
	*/
	static inline void bch2_journal_res_put(struct journal *j,
	struct journal_res *res)
	{
	if (!res->ref)
	return;

	lock_release(&j->res_map, _THIS_IP_);

	while (res->u64s)
	bch2_journal_add_entry(j, res,
	BCH_JSET_ENTRY_btree_keys,
	0, 0, 0);

	bch2_journal_buf_put(j, res->seq);

	res->ref = 0;
	}

	int bch2_journal_res_get_slowpath(struct journal , struct journal_res ,
	unsigned, struct btree_trans *);

	/* First bits for BCH_WATERMARK: */
	enum journal_res_flags {
	__JOURNAL_RES_GET_NONBLOCK = BCH_WATERMARK_BITS,
	__JOURNAL_RES_GET_CHECK,
	};

	#define JOURNAL_RES_GET_NONBLOCK (1 << __JOURNAL_RES_GET_NONBLOCK)
	#define JOURNAL_RES_GET_CHECK (1 << __JOURNAL_RES_GET_CHECK)

	static inline int journal_res_get_fast(struct journal *j,
	struct journal_res *res,
	unsigned flags)
	{
	union journal_res_state old, new;

	old.v = atomic64_read(&j->reservations.counter);
	do {
	new.v = old.v;

	/*
	* Check if there is still room in the current journal
	* entry, smp_rmb() guarantees that reads from reservations.counter
	* occur before accessing cur_entry_u64s:
	*/
	smp_rmb();
	if (new.cur_entry_offset + res->u64s > j->cur_entry_u64s)
	return 0;

	EBUG_ON(!journal_state_count(new, new.idx));

	if ((flags & BCH_WATERMARK_MASK) < j->watermark)
	return 0;

	new.cur_entry_offset += res->u64s;
	journal_state_inc(&new);

	/*
	* If the refcount would overflow, we have to wait:
	* XXX - tracepoint this:
	*/
	if (!journal_state_count(new, new.idx))
	return 0;

	if (flags & JOURNAL_RES_GET_CHECK)
	return 1;
	} while (!atomic64_try_cmpxchg(&j->reservations.counter,
	&old.v, new.v));

	res->ref = true;
	res->offset = old.cur_entry_offset;
	res->seq = journal_cur_seq(j);
	res->seq -= (res->seq - old.idx) & JOURNAL_STATE_BUF_MASK;
	return 1;
	}

	static inline int bch2_journal_res_get(struct journal j, struct journal_res res,
	unsigned u64s, unsigned flags,
	struct btree_trans *trans)
	{
	int ret;

	EBUG_ON(res->ref);
	EBUG_ON(!test_bit(JOURNAL_running, &j->flags));

	res->u64s = u64s;

	if (journal_res_get_fast(j, res, flags))
	goto out;

	ret = bch2_journal_res_get_slowpath(j, res, flags, trans);
	if (ret)
	return ret;
	out:
	if (!(flags & JOURNAL_RES_GET_CHECK)) {
	lock_acquire_shared(&j->res_map, 0,
	(flags & JOURNAL_RES_GET_NONBLOCK) != 0,
	NULL, _THIS_IP_);
	EBUG_ON(!res->ref);
	BUG_ON(!res->seq);
	}
	return 0;
	}

	/* journal_entry_res: */

	void bch2_journal_entry_res_resize(struct journal *,
	struct journal_entry_res *,
	unsigned);

	int bch2_journal_flush_seq_async(struct journal , u64, struct closure );
	void bch2_journal_flush_async(struct journal , struct closure );

	int bch2_journal_flush_seq(struct journal *, u64, unsigned);
	int bch2_journal_flush(struct journal *);
	bool bch2_journal_noflush_seq(struct journal *, u64, u64);
	int bch2_journal_meta(struct journal *);

	void bch2_journal_halt_locked(struct journal *);
	void bch2_journal_halt(struct journal *);

	static inline int bch2_journal_error(struct journal *j)
	{
	return j->reservations.cur_entry_offset == JOURNAL_ENTRY_ERROR_VAL
	? -BCH_ERR_journal_shutdown : 0;
	}

	struct bch_dev;

	void bch2_journal_unblock(struct journal *);
	void bch2_journal_block(struct journal *);
	struct journal_buf bch2_next_write_buffer_flush_journal_buf(struct journal , u64, bool *);

	void __bch2_journal_debug_to_text(struct printbuf , struct journal );
	void bch2_journal_debug_to_text(struct printbuf , struct journal );

	int bch2_set_nr_journal_buckets(struct bch_fs , struct bch_dev , unsigned);
	int bch2_dev_journal_bucket_delete(struct bch_dev *, u64);

	int bch2_dev_journal_alloc(struct bch_dev *, bool);
	int bch2_fs_journal_alloc(struct bch_fs *);

	void bch2_dev_journal_stop(struct journal , struct bch_dev );

	void bch2_fs_journal_stop(struct journal *);
	int bch2_fs_journal_start(struct journal *, u64, u64);
	void bch2_journal_set_replay_done(struct journal *);

	void bch2_dev_journal_exit(struct bch_dev *);
	int bch2_dev_journal_init(struct bch_dev , struct bch_sb );
	void bch2_fs_journal_exit(struct journal *);
	void bch2_fs_journal_init_early(struct journal *);
	int bch2_fs_journal_init(struct journal *);

	#endif /* _BCACHEFS_JOURNAL_H */