Fix blk_meta_t/BAM accounting reconciliation flagged in FABRIC-2.md §I.2

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FIRSTTOUCH ownership (blk_meta_t's BLK_FLAG_CLAIMED/owner_fp) and the
generic block-allocation bitmap (BAM, blk_bam_entry_t) were two parallel,
unreconciled accounting systems: blk_firsttouch_claim() never touched the
BAM, and blk_allocate()/devblock_is_free() never checked BLK_FLAG_CLAIMED.
A FIRSTTOUCH claim could be silently overwritten by a later blk_allocate()
call, or could itself steal a devblock already in ordinary use via
BLOCK/UPDATE.

- devblock_is_free() (shared by blk_firsttouch_claim() and
  blk_migration_idle_check()) now also checks the BAM entries of all
  BLK_PACK_RATIO member LBNs, not just blk_meta_t.
- New devblock_claimed_by_lbn() helper wired into blk_allocate()'s
  free-scan, so it skips any LBN whose devblock is BLK_FLAG_CLAIMED.
- blk_firsttouch_claim() now marks the BAM allocated for all 3 member
  LBNs of each devblock it claims, which also fixes vol_meta.free_blocks
  never decrementing for FIRSTTOUCH claims.
- blk_meta_relocate_devblock() traced and confirmed NOT part of the bug —
  it already keeps BAM in sync via blk_subsys_relocate_block()'s own
  blk_mark_free()/blk_update() calls.

Both boundary cases (the reserved/user LBN split at a slot's start_lbn,
and BAM-array bounds) are guarded explicitly.

Verified with the mandatory 3-arch QEMU acceptance (identical dictionary
hashes, clean BYE) plus a live logic test: a temporary TEST-BAM-RECON
word, run once via SK_CMD and fully reverted, confirmed on running code
that ordinary allocation and a FIRSTTOUCH claim land on disjoint LBN
ranges in both directions. FABRIC-2.md §I.2 updated in place with the
closure note, per this project's documentation discipline.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018EjXFo7mPXjUMjfJeuUUz4

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This commit is contained in:

Robert Allan James

2026-09-05 15:57:03 -04:00

co-authored by Claude Sonnet 5

parent 04cc17920e

commit aa33aedca8

3 changed files with 90 additions and 6 deletions

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