increment_for_block_map(9)

increment_for_block_map(9) 💅 — Kernel API Manual ✨

💖 NAME 💖

increment_for_block_map — increment the reference count for a block map page. That’s the whole assignment, bestie: one block map page’s refcount gets the glow-up. 👑

✨ SYNOPSIS ✨

int increment_for_block_map (struct vdo_slab *slab , struct
       reference_block *block , slab_block_number block_number , enum
       reference_status old_status , struct pbn_lock *lock , bool
       normal_operation , vdo_refcount_t *counter_ptr , bool adjust_block_count
       );

🦋 ARGUMENTS 🦋

• slab — The slab which owns the block. Like, the actual owner, no gatekeeping. 👑
• block — The reference block which contains the block being updated.
• block_number — The block to update. This is the one getting touched. 🫶
• old_status — The reference status of the block before this increment.
• lock — The pbn_lock associated with this increment (may be NULL). Yes, NULL is allowed, ngl.
• normal_operation — Whether we are in normal operation vs. recovery or rebuild.
• counter_ptr — A pointer to the count for the block (in, out). It goes in and comes back out, main character behavior. 🔁
• adjust_block_count — Whether to update the allocator’s free block count.

🌸 DESCRIPTION 🌸

Okay so here’s the vibe check: all block map increments should be from provisional to MAXIMUM_REFERENCE_COUNT. Since block map blocks never dedupe, they should never be adjusted from any other state. The adjustment always results in MAXIMUM_REFERENCE_COUNT, because this value is used to prevent dedupe against block map blocks. No cap, that’s literally the rule. 💅

🎀 RETURN 🎀

VDO_SUCCESS or an error. That’s it — slay or error out, no in-between. 😭

💅 SEE ALSO 💅

Kernel file ./drivers/md/dm-vdo/slab-depot.c is the home base. The extended fam includes get_lock(9), must_make_entries_to_flush(9), is_reaping(9), initialize_tail_block(9), initialize_journal_state(9), block_is_full(9), is_slab_journal_blank(9), mark_slab_journal_dirty(9), compute_fullness_hint(9), check_summary_drain_complete(9), notify_summary_waiters(9), finish_updating_slab_summary_block(9), finish_update(9), handle_write_error(9), launch_write(9), update_slab_summary_entry(9), finish_reaping(9), complete_reaping(9), handle_flush_error(9), flush_for_reaping(9), reap_slab_journal(9), adjust_slab_journal_block_reference(9), release_journal_locks(9), update_tail_block_location(9), reopen_slab_journal(9), complete_write(9), write_slab_journal_block(9), commit_tail(9), encode_slab_journal_entry(9), expand_journal_point(9), add_entry(9), vdo_attempt_replay_into_slab(9), requires_reaping(9), launch_reference_block_write(9), finish_reference_block_write(9), get_reference_counters_for_block(9), pack_reference_block(9), handle_io_error(9), write_reference_block(9), reference_count_to_status(9), dirty_block(9), get_reference_block(9), slab_block_number_from_pbn(9), get_reference_counter(9), adjust_free_block_count(9), increment_for_data(9), decrement_for_data(9), update_reference_count(9), add_entry_from_waiter(9), is_next_entry_a_block_map_increment(9), add_entries(9), reset_search_cursor(9), advance_search_cursor(9), vdo_adjust_reference_count_for_rebuild(9), replay_reference_count_change(9), find_zero_byte_in_word(9), find_free_block(9), search_current_reference_block(9), search_reference_blocks(9), make_provisional_reference(9), dirty_all_reference_blocks(9), match_bytes(9), count_valid_references(9), unpack_reference_block(9), finish_reference_block_load(9), load_reference_block_group(9), load_reference_blocks(9), drain_slab(9), read_slab_journal_tail(9), load_slab_journal(9), get_next_slab(9), has_slabs_to_scrub(9), uninitialize_scrubber_vio(9), finish_scrubbing(9), slab_scrubbed(9), abort_scrubbing(9), handle_scrubber_error(9), apply_block_entries(9), apply_journal_entries(9), start_scrubbing(9), scrub_next_slab(9), scrub_slabs(9), get_depot_slab_iterator(9), next_slab(9), abort_waiter(9), vdo_acquire_provisional_reference(9), open_slab(9), vdo_enqueue_clean_slab_waiter(9), vdo_modify_reference_count(9), vdo_notify_slab_journals_are_recovered(9), make_slab(9), allocate_slabs(9), vdo_abandon_new_slabs(9), release_recovery_journal_lock(9), prepare_for_tail_block_commit(9), schedule_tail_block_commit(9), initialize_slab_scrubber(9), initialize_slab_summary_block(9), vdo_decode_slab_depot(9), vdo_free_slab_depot(9), vdo_record_slab_depot(9), vdo_allocate_reference_counters(9), get_slab_number(9), vdo_get_slab(9), vdo_get_increment_limit(9), vdo_is_physical_data_block(9), vdo_get_slab_depot_allocated_blocks(9), vdo_get_slab_depot_data_blocks(9), finish_combining_zones(9), combine_summaries(9), finish_loading_summary(9), load_slab_summary(9), vdo_load_slab_depot(9), vdo_prepare_slab_depot_to_allocate(9), vdo_update_slab_depot_size(9), vdo_prepare_to_grow_slab_depot(9), finish_registration(9), vdo_use_new_slabs(9), stop_scrubbing(9), vdo_drain_slab_depot(9), resume_scrubbing(9), vdo_resume_slab_depot(9), vdo_commit_oldest_slab_journal_tail_blocks(9), vdo_scrub_all_unrecovered_slabs(9), get_block_allocator_statistics(9), get_ref_counts_statistics(9), get_slab_journal_statistics(9), vdo_get_slab_depot_statistics(9), and vdo_dump_slab_depot(9).

mwah 💋 — source/version vibes: ./drivers/md/dm-vdo; date: October 2026. ✨💖