linux/fs/bcachefs/journal_seq_blacklist.c

// SPDX-License-Identifier: GPL-2.0

#include "bcachefs.h"
#include "eytzinger.h"
#include "journal.h"
#include "journal_seq_blacklist.h"
#include "super-io.h"

/*
 * journal_seq_blacklist machinery:
 *
 * To guarantee order of btree updates after a crash, we need to detect when a
 * btree node entry (bset) is newer than the newest journal entry that was
 * successfully written, and ignore it - effectively ignoring any btree updates
 * that didn't make it into the journal.
 *
 * If we didn't do this, we might have two btree nodes, a and b, both with
 * updates that weren't written to the journal yet: if b was updated after a,
 * but b was flushed and not a - oops; on recovery we'll find that the updates
 * to b happened, but not the updates to a that happened before it.
 *
 * Ignoring bsets that are newer than the newest journal entry is always safe,
 * because everything they contain will also have been journalled - and must
 * still be present in the journal on disk until a journal entry has been
 * written _after_ that bset was written.
 *
 * To accomplish this, bsets record the newest journal sequence number they
 * contain updates for; then, on startup, the btree code queries the journal
 * code to ask "Is this sequence number newer than the newest journal entry? If
 * so, ignore it."
 *
 * When this happens, we must blacklist that journal sequence number: the
 * journal must not write any entries with that sequence number, and it must
 * record that it was blacklisted so that a) on recovery we don't think we have
 * missing journal entries and b) so that the btree code continues to ignore
 * that bset, until that btree node is rewritten.
 */

static unsigned sb_blacklist_u64s(unsigned nr)
{ … }

int bch2_journal_seq_blacklist_add(struct bch_fs *c, u64 start, u64 end)
{ … }

static int journal_seq_blacklist_table_cmp(const void *_l, const void *_r)
{ … }

bool bch2_journal_seq_is_blacklisted(struct bch_fs *c, u64 seq,
				     bool dirty)
{ … }

int bch2_blacklist_table_initialize(struct bch_fs *c)
{ … }

static int bch2_sb_journal_seq_blacklist_validate(struct bch_sb *sb, struct bch_sb_field *f,
				enum bch_validate_flags flags, struct printbuf *err)
{ … }

static void bch2_sb_journal_seq_blacklist_to_text(struct printbuf *out,
						  struct bch_sb *sb,
						  struct bch_sb_field *f)
{ … }

const struct bch_sb_field_ops bch_sb_field_ops_journal_seq_blacklist = …;

bool bch2_blacklist_entries_gc(struct bch_fs *c)
{ … }