{
  "slug": "rwf-noappend",
  "term": "RWF_NOAPPEND",
  "aliases": [
    "per-write append override"
  ],
  "definition": "RWF_NOAPPEND is a Linux pwritev2 flag that suppresses O_APPEND placement for one write operation.",
  "note": "Documented since Linux 6.9, it overrides append placement for the call, not the shared file-status flag. A nonnegative offset selects the position; offset -1 still uses and updates the shared current offset. [readv-api] [linux-rw-flags] [linux-write-path]\n\nIn v6.17, kiocb_set_rw_flags returns EPERM when suppressing append would violate an append-only inode, and EINVAL for simultaneous append/noappend flags. It is not a bypass of append-only inode protection. [linux-rw-flags]\n\nA zero-total-length write can finish before flag validation. EOPNOTSUPP can mean an unsupported flag or write path, not only an old kernel. Test a nonempty disposable-file operation and inspect placement and errors. [linux-write-path]",
  "advantages": [
    "Keeps per-call positioning separate from later writes through the same open file description."
  ],
  "limitations": [
    "Availability must be checked for the actual kernel and target, not inferred from a successful empty write. [linux-write-path]",
    "Does not replace synchronization, short-write handling or protection against overlapping writers. [readv-api]"
  ],
  "related": [
    "rwf-append",
    "o-append",
    "pwrite",
    "file-offset",
    "open-file-description",
    "short-write",
    "writev",
    "fsync"
  ],
  "status": "shipping",
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "updated": "2026-11-11",
  "citations": [
    {
      "id": "readv-api",
      "title": "Linux man-pages: readv(2), pwritev2 per-call flags and offset semantics",
      "url": "https://man7.org/linux/man-pages/man2/readv.2.html",
      "accessed": "2026-11-11"
    },
    {
      "id": "linux-rw-flags",
      "title": "Linux v6.17: kiocb_set_rw_flags validation and per-operation append state",
      "url": "https://github.com/torvalds/linux/blob/v6.17/include/linux/fs.h",
      "accessed": "2026-11-11"
    },
    {
      "id": "linux-write-path",
      "title": "Linux v6.17: pwritev2 dispatch, current offsets and zero-length write handling",
      "url": "https://github.com/torvalds/linux/blob/v6.17/fs/read_write.c",
      "accessed": "2026-11-11"
    },
    {
      "id": "hesela-publication",
      "title": "Hesela: Atomic rename is not a durable commit, per-write positioning",
      "url": "https://hesela.com/analyses/atomic-rename-directory-durability/#per-write-position",
      "accessed": "2026-11-11"
    }
  ],
  "provenance": [
    "API documentation and pinned Linux v6.17 source review, not a native transfer, concurrency or crash experiment. [readv-api] [linux-rw-flags] [linux-write-path]"
  ]
}