{
  "slug": "journal-checksum",
  "term": "Journal checksum",
  "aliases": [],
  "definition": "A journal checksum is an integrity value computed over specified journal records or payloads to detect changes within that coverage.",
  "note": "Checksum coverage and recovery action depend on the journal format. In JBD2, descriptor, commit and journaled-block tag checks have distinct roles. A valid commit-block checksum does not by itself validate every journal payload. [recovery]\n\nIn Linux v6.12, a journaled-block tag mismatch skips that image while remembering a recovery error. Other images can still be replayed, and final writeback is attempted even after a failed pass. This is not a guarantee that mounting succeeds. [recovery]",
  "status": "shipping",
  "advantages": [],
  "limitations": [],
  "related": [
    "checksum",
    "journal-checkpoint",
    "journal-revoke-record",
    "crash-corruption-ambiguity"
  ],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "citations": [
    {
      "id": "recovery",
      "title": "Linux v6.12: JBD2 recovery.c",
      "url": "https://github.com/torvalds/linux/blob/adc218676eef25575469234709c2d87185ca223a/fs/jbd2/recovery.c",
      "accessed": "2026-10-17"
    },
    {
      "id": "hesela",
      "title": "Hesela: Ext4 replay, checksum failure paths and ambiguous tails",
      "url": "https://hesela.com/analyses/ext4-journal-replay-revocation/",
      "accessed": "2026-10-17"
    }
  ],
  "updated": "2026-10-17",
  "provenance": [
    "Behavior is scoped to the pinned Linux v6.12 source, not a fault-injection experiment or a guarantee about every filesystem."
  ]
}