---
title: "vfs-memory — Mova code model"
description: "Mova code model of vfs/src/mem.rs: components with their labels, obernants and the model text."
url: "https://groupants.elamur.ai/free/en/mova/vfs/src/mem.rs.groupant/"
---
Elamur: [Mova](https://md.mova.elamur.ai/free/en/) · [Dictionary](https://md.dictionary.elamur.ai/free/en/) · [Research](https://md.research.elamur.ai/free/en/) · **Groupants**

This page as HTML: <https://groupants.elamur.ai/free/en/mova/vfs/src/mem.rs.groupant/>

# vfs-memory

The groupant beside vfs/src/mem.rs in the Mova repository: what the code computes, what it never does, how to go back from its outputs, its invariants, cost and checks.

## Facts

- **kind:** groupant
- **status:** partial source bound model
- **source:** [`vfs/src/mem.rs`](https://github.com/ElamurAI/mova-free/blob/main/vfs/src/mem.rs)
- **source SHA-256:** `d97f98687ddc88ba…`
- **repository folder:** [`vfs/src/mem.rs.groupant`](https://github.com/ElamurAI/mova-free/tree/main/vfs/src/mem.rs.groupant)
- **repository commit:** `855da7bd4a7b`

> **Implementation material.** A Mova code model describes this code at one source revision: partial models, finite checks and their stated scope. It is not a reviewed general exposition, and its labels are shown as written, never raised.

## Components

| component | label | where |
|---|---|---|
| **approximant** | partial | [approximant](#approximant) |
| **ast** | partial | `syntax.json` |
| **composition** | partial | [composition](#composition) |
| **cost** | partial | [Cost](#cost) |
| **descriptant** | present | [descriptant](#descriptant) |
| **invariant** | partial | [Invariant](#invariant) |
| **tests** | executed bounded checks | [tests](#tests) |

## Obernants

The typed relations around the forward model: the behaviour complement (what the code never does), the reverse reconstruction (every input compatible with an output) and specialised views.

| id | type | label | where |
|---|---|---|---|
| `behavior_complement` | behavior_complement | partial source derived model | [behavior_complement](#behavior-complement) |
| `reverse_reconstruction` | reverse_reconstruction | partial source derived model | [reverse_reconstruction](#reverse-reconstruction) |
| `quota_order` | quota_order | partial source derived model | [quota_order](#quota-order) |
| `cow_ownership` | cow_ownership | partial source derived model | [cow_ownership](#cow-ownership) |
| `partial_effects` | partial_effects | partial source derived model | [partial_effects](#partial-effects) |
| `snapshot_projection` | snapshot_projection | partial source derived model | [snapshot_projection](#snapshot-projection) |

## Parts

- [vfs-memory-resolution](https://md.groupants.elamur.ai/free/en/mova/vfs/src/mem.rs.groupant/resolution.groupant/)
- [vfs-memory-edits](https://md.groupants.elamur.ai/free/en/mova/vfs/src/mem.rs.groupant/edits.groupant/)
- [vfs-memory-directories](https://md.groupants.elamur.ai/free/en/mova/vfs/src/mem.rs.groupant/directories.groupant/)
- [vfs-memory-snapshots](https://md.groupants.elamur.ai/free/en/mova/vfs/src/mem.rs.groupant/snapshots.groupant/)
- [vfs-memory-transfers](https://md.groupants.elamur.ai/free/en/mova/vfs/src/mem.rs.groupant/transfers.groupant/)

## Model text


### descriptant

#### vfs-memory

Arc tree, symlink resolution, edits, snapshots and explicit transfers.

##### Prospective epoch

2026-10-31: source reviewed before edits; prospective review retained under $MOVA_DATA/runs/octopus-wave31-vfs-2026-10-31/prospective.md. Predicted order/cost: Resolve O(path+expanded link bytes+sum log fanout); COW clones shared directory maps O(sum fanouts), shared content O(old bytes) on append/At/truncate. Snapshot O(cwd bytes); restore also drops unshared divergent tree. dump O(tree+content+path output).

##### Observation epoch

Bounded actual calls and compiled negative controls are recorded in tests.md. Production behavior bytes unchanged; only focused test blocks added. Snapshot constant-time wording is conditional on cwd and destruction; recursive operations may partially commit.

##### Unsupported approximants

No executable percentage surrogate is claimed for these categorical/state/effect observations. Future 1%,2%,5%,10% require a useful metric, explicit domain and exact reference.

Integration review narrows the quota complement to single-file mutations. Compound mkdir/import/export paths retain their separately modeled successful prefixes.

### approximant

#### Forward relation

Arc tree, symlink resolution, edits, snapshots and explicit transfers.

State S=(root,cwd,clock,next_ino,usage,tmp;limits,journal,fault). Resolution expands links at most40 hops. Validated edits tick then COW mutate; file bytes and node counts update. snapshot captures first6 fields while journal records; restore reuses root and copies cwd, restoring counters except deliberate fault.

Domain: bounded inputs with available allocation and nonoverflowing counters unless checked explicitly. The relation is partial and source-derived.

### composition

#### Composition

Arc tree, symlink resolution, edits, snapshots and explicit transfers. Shared state and order: State S=(root,cwd,clock,next_ino,usage,tmp;limits,journal,fault). Resolution expands links at most40 hops. Validated edits tick then COW mutate; file bytes and node counts update. snapshot captures first6 fields while journal records; restore reuses root and copies cwd, restoring counters except deliberate fault.

Scoped children project this same source. Their domains and effects remain conditional; source execution connects these clauses rather than independently proving their wiring. Usage counts file data and all nonroot nodes, not link text. Single-file quota failures leave dump unchanged but journal records. mkdir_all and transfers can partially commit. Journal/limits/fault are outside snapshot.

### models

## Typed source models

Source-bound partial relations; no universal finite-test proof.

### behavior_complement

Subject: vfs-memory. Domain: Arc tree, symlink resolution, edits, snapshots and explicit transfers. Valid allocations, bounded counters, Fault=None unless explicitly named. Observation: one call or the stated finite trace.

Operator: For single-file mutations, Fault=None quota rejection cannot install an over-limit file or advance the edit clock. Snapshot isolation excludes later writes changing retained root. Absolute virtual paths never directly invoke host except explicit import/export.

Approximation: source-derived partial relation; complement is an inner excluded-behavior claim under these premises, converse retains compatible antecedents. Evidence: tests.md; unobserved concurrency/resource failures remain unknown.

### reverse_reconstruction

Subject: vfs-memory. Domain: Arc tree, symlink resolution, edits, snapshots and explicit transfers. Valid allocations, bounded counters, Fault=None unless explicitly named. Observation: one call or the stated finite trace.

Operator: Restored snapshot determines represented state but admits any intervening mutation/journal history; limits/fault remain external. Reads admit any unseen tree; overwrite loses old bytes; dump/fingerprint do not uniquely identify histories.

Approximation: source-derived partial relation; complement is an inner excluded-behavior claim under these premises, converse retains compatible antecedents. Evidence: tests.md; unobserved concurrency/resource failures remain unknown.

### quota_order

Subject: vfs-memory. Domain: Arc tree, symlink resolution, edits, snapshots and explicit transfers. Valid allocations, bounded counters, Fault=None unless explicitly named. Observation: one call or the stated finite trace.

Operator: Node quota checked for new file before size, checked off+len before FBig, then total growth before mutation. Arithmetic overflow/allocation beyond bounded fixtures remains gap.

Approximation: source-derived partial relation; complement is an inner excluded-behavior claim under these premises, converse retains compatible antecedents. Evidence: tests.md; unobserved concurrency/resource failures remain unknown.

### cow_ownership

Subject: vfs-memory. Domain: Arc tree, symlink resolution, edits, snapshots and explicit transfers. Valid allocations, bounded counters, Fault=None unless explicitly named. Observation: one call or the stated finite trace.

Operator: Root and child Arc sharing preserves snapshots; copying maps scales with fanout, not only depth. Shared read buffers retain old bytes.

Approximation: source-derived partial relation; complement is an inner excluded-behavior claim under these premises, converse retains compatible antecedents. Evidence: tests.md; unobserved concurrency/resource failures remain unknown.

### partial_effects

Subject: vfs-memory. Domain: Arc tree, symlink resolution, edits, snapshots and explicit transfers. Valid allocations, bounded counters, Fault=None unless explicitly named. Observation: one call or the stated finite trace.

Operator: mkdir_all creates prefixes incrementally; import/export stop after first error with earlier effects retained. No all-operation transaction claim.

Approximation: source-derived partial relation; complement is an inner excluded-behavior claim under these premises, converse retains compatible antecedents. Evidence: tests.md; unobserved concurrency/resource failures remain unknown.

### snapshot_projection

Subject: vfs-memory. Domain: Arc tree, symlink resolution, edits, snapshots and explicit transfers. Valid allocations, bounded counters, Fault=None unless explicitly named. Observation: one call or the stated finite trace.

Operator: Snapshot excludes limits,journal,fault. cwd cloning and dropping divergent roots refute unconditional O(1) wording; finite tests establish state restoration only.

Approximation: source-derived partial relation; complement is an inner excluded-behavior claim under these premises, converse retains compatible antecedents. Evidence: tests.md; unobserved concurrency/resource failures remain unknown.

### tests

#### Checks and limitations

Exact named observations: escape_by_dotdot_is_denied, symlinks_cannot_lead_outside, bad_names_and_paths, limits_fire_with_clear_errors_and_leave_state_unchanged, limits_parse, snapshot_changes_restore_is_byte_identical, snapshot_is_isolated_copy_on_write, restore_after_failed_ops_and_limits, posix_like_semantics, virtual_clock_is_deterministic, journal_records_ops_errors_and_denials, import_export_round_trip, dirfs_confines_to_root, gates_green_and_negative_controls_red, wave31_sparse_copy_and_partial_directory_failure.

Fresh receipts: $MOVA_DATA/runs/octopus-wave31-vfs-2026-10-31; run.sh retains four profile/repetition sets with raw logs and numeric statuses. native-commands.json and source-test-map.json disambiguate targets. Compiled mutations and exact restoration are separately retained in mutation-summary.json.

These finite observations are not semantic completeness. Source syntax generated twice and compared byte-for-byte. Host effects are limited to owned TMPDIR fixtures. Existing absolute_paths_never_reach_the_host and open_modes are skipped; snapbench main is skipped. Standalone helpers/reexports are only observed through named callers or representation checks; RealFs effect methods unexecuted.

### invariant-and-cost

## Invariant and cost

### Invariant

Usage counts file data and all nonroot nodes, not link text. Single-file quota failures leave dump unchanged but journal records. mkdir_all and transfers can partially commit. Journal/limits/fault are outside snapshot.

### Cost

Resolve O(path+expanded link bytes+sum log fanout); COW clones shared directory maps O(sum fanouts), shared content O(old bytes) on append/At/truncate. Snapshot O(cwd bytes); restore also drops unshared divergent tree. dump O(tree+content+path output).

No timing or numerical error guarantee is inferred from finite tests.