{
  "slug": "errseq-t",
  "term": "errseq_t",
  "aliases": [
    "errseq"
  ],
  "definition": "errseq_t is a Linux kernel datatype that records an error and sequence state so observers can detect failures since their saved cursor.",
  "note": "It stores an error code and sequence information in 32 bits. Checking and advancing a cursor acknowledges observation; it does not repair data. It is neither a complete event history nor an exact failure counter, and updating a shared observer cursor requires serialization.",
  "status": "shipping",
  "advantages": [],
  "limitations": [],
  "related": [
    "writeback-error",
    "fsync"
  ],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "citations": [
    {
      "id": "linux-errseq",
      "title": "Linux kernel: The errseq_t datatype",
      "url": "https://docs.kernel.org/core-api/errseq.html",
      "accessed": "2026-10-10"
    },
    {
      "id": "hesela-fsync",
      "title": "Hesela: Why retrying a failed fsync does not prove durability",
      "url": "https://hesela.com/analyses/fsync-failure-retry-durability/",
      "accessed": "2026-10-10"
    }
  ],
  "updated": "2026-10-10"
}