bstack 0.4.4

A persistent, fsync-durable binary stack backed by a single file
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218

//! Fault-injection fuzz for in-place resize
//! ([`BStackInPlaceResizeAllocator`](crate::alloc::BStackInPlaceResizeAllocator)).
//!
//! Arms a random [`FaultPolicy`] around each `alloc`/`realloc_inplace`/`dealloc`
//! and asserts the failure contract under torn multi-call operations, the way
//! [`init_fault`](super::init_fault) does for `realloc`:
//!
//! * every operation succeeds or fails cleanly (an error, never a panic);
//! * `realloc_inplace` never commits a *moved* region, so a returned handle is
//!   always the untouched original — verified byte-for-byte at its original
//!   `(start, len)` — and a `None` handle is a genuine (acceptable) leak;
//! * a fault leaves at most a leak, never corruption: after **reopen +
//!   recovery** every still-live allocation reads back byte-for-byte.
//!
//! The structural in-place paths — a segregated tail extend / shrink-reclaim, a
//! first-fit front carve or free-neighbour merge — are exactly the ones a crash
//! can tear, so this is where their leak-preferring recovery is exercised. A
//! clean `Unsupported`/`InvalidInput` rejection is distinguished from an injected
//! fault by error kind and does not force a reopen.

use super::common::{
    FuzzConfig, Guard, Operation, gen_inplace_deltas, gen_op, make_allocator,
    policies::{RandomFaults, per_mille},
    temp_path, verify_pattern, write_pattern,
};
use super::inplace::apply_ok;
use crate::BStack;
use crate::alloc::{
    BStackInPlaceResizeAllocator, BStackOwnedSlice, BStackOwnedSliceAllocator, BStackRange,
    FirstFitBStackAllocator, GhostTreeBstackAllocator, SegregatedBStackAllocator,
};
use crate::fault::FaultPolicy;
use rand::{RngExt, SeedableRng, rngs::StdRng};
use std::io;
use std::sync::Arc;

/// Disarm, reopen (running recovery), and re-verify every live allocation.
/// Panics on any data mismatch — that is the corruption signal.
fn reopen_and_verify<A, F>(
    alloc: A,
    make: &F,
    live: &[(BStackRange, u64)],
    bias: u64,
    ctx: &str,
) -> A
where
    A: BStackOwnedSliceAllocator + BStackInPlaceResizeAllocator,
    F: Fn(BStack) -> io::Result<A>,
{
    alloc.stack().set_fault_policy(None);
    let stack = alloc.into_stack();
    let alloc = make(stack).unwrap();
    for (i, (range, id)) in live.iter().enumerate() {
        let s = unsafe { BStackOwnedSlice::from_raw_parts(&alloc, range.start(), range.len()) };
        verify_pattern(&s, *id, bias, &format!("{ctx} rec{i}"));
    }
    alloc
}

fn run_inplace_fault_fuzz<A, F>(make: F, seed_salt: u64)
where
    A: BStackOwnedSliceAllocator + BStackInPlaceResizeAllocator,
    F: Fn(BStack) -> io::Result<A>,
{
    let cfg = FuzzConfig::from_env();
    let path = temp_path("ip_fault");
    let _guard = Guard(path.clone());
    // Reproducible: `BSTACK_FUZZ_SEED=<n>` replays an identical run.
    let master_seed = std::env::var("BSTACK_FUZZ_SEED")
        .ok()
        .and_then(|v| v.parse().ok())
        .unwrap_or_else(|| rand::rng().random_range(0..=u64::MAX));
    eprintln!("[alloc_fuzz::inplace_fault salt={seed_salt:#06x}] BSTACK_FUZZ_SEED={master_seed}");
    let mut rng = StdRng::seed_from_u64(master_seed ^ seed_salt);
    let bias = rng.random_range(0..=u64::MAX);
    let fault_seed = rng.random_range(0..=u64::MAX);
    let policy: Arc<dyn FaultPolicy> = Arc::new(RandomFaults::new(fault_seed, per_mille()));

    let mut alloc = make(BStack::open(&path).unwrap()).unwrap();
    let mut live: Vec<(BStackRange, u64)> = Vec::new();
    let mut next_id = 0u64;

    for step in 0..cfg.ops {
        // The op faulted iff it returned an *injected* error (not a clean
        // Unsupported/InvalidInput rejection); a fault may have left the
        // allocator mid-mutation, so we reopen (recover) before continuing.
        let mut faulted = false;

        match gen_op(&mut rng, &cfg, !live.is_empty(), false) {
            Operation::Alloc(len) => {
                alloc.stack().set_fault_policy(Some(policy.clone()));
                let r = alloc.alloc(len);
                alloc.stack().set_fault_policy(None);
                match r {
                    Ok(mut s) => {
                        let id = next_id;
                        next_id += 1;
                        write_pattern(&mut s, id, bias).unwrap();
                        live.push((s.as_range(), id));
                    }
                    Err(_) => faulted = true,
                }
            }
            Operation::Realloc(_) => {
                let i = rng.random_range(0..live.len());
                let (range, id) = live.swap_remove(i);
                let (start, len) = (range.start(), range.len());
                let s = unsafe { BStackOwnedSlice::from_raw_parts(&alloc, start, len) };
                let (prepend, append) = gen_inplace_deltas(&mut rng, len, &cfg);
                alloc.stack().set_fault_policy(Some(policy.clone()));
                let r = alloc.realloc_inplace(s, prepend, append);
                alloc.stack().set_fault_policy(None);
                match r {
                    Ok(s2) => {
                        if let Some(s2) = apply_ok(
                            s2,
                            start,
                            len,
                            prepend,
                            append,
                            id,
                            bias,
                            "fault inplace: resize",
                        ) {
                            live.push((s2.as_range(), id));
                        }
                    }
                    Err(e) => {
                        let kind = e.source.kind();
                        if matches!(
                            kind,
                            io::ErrorKind::Unsupported | io::ErrorKind::InvalidInput
                        ) {
                            // Clean rejection, not a fault: original returned intact.
                            let h = e.handle.expect("inplace rejection must return the handle");
                            assert_eq!(h.start(), start, "inplace rejection: start preserved");
                            assert_eq!(h.len(), len, "inplace rejection: len preserved");
                            verify_pattern(&h, id, bias, "inplace rejection: original intact");
                            live.push((h.as_range(), id));
                        } else {
                            // Injected fault. realloc_inplace never commits a moved
                            // region, so a returned handle is the untouched original.
                            faulted = true;
                            if let Some(h) = e.handle {
                                assert_eq!(h.start(), start, "fault inplace: survivor is original");
                                assert_eq!(h.len(), len, "fault inplace: survivor is original");
                                verify_pattern(&h, id, bias, "fault inplace: original intact");
                                live.push((h.as_range(), id));
                            }
                            // None → region genuinely lost; drop it.
                        }
                    }
                }
            }
            Operation::Dealloc => {
                let i = rng.random_range(0..live.len());
                let (range, id) = live.swap_remove(i);
                let s =
                    unsafe { BStackOwnedSlice::from_raw_parts(&alloc, range.start(), range.len()) };
                alloc.stack().set_fault_policy(Some(policy.clone()));
                let r = alloc.dealloc(s);
                alloc.stack().set_fault_policy(None);
                match r {
                    Ok(()) => {}
                    Err(e) => {
                        faulted = true;
                        if let Some(h) = e.handle {
                            // Free failed, region still live and unchanged.
                            verify_pattern(&h, id, bias, "fault inplace dealloc err: retained");
                            live.push((h.as_range(), id));
                        }
                        // None → region lost/leaked; drop it.
                    }
                }
            }
            Operation::Check => {
                let i = rng.random_range(0..live.len());
                let (range, id) = &live[i];
                let s =
                    unsafe { BStackOwnedSlice::from_raw_parts(&alloc, range.start(), range.len()) };
                verify_pattern(&s, *id, bias, "fault inplace: check");
            }
            Operation::Reopen => {}
        }

        let periodic = cfg.reopen_every > 0 && step > 0 && step % cfg.reopen_every == 0;
        if faulted || periodic {
            alloc = reopen_and_verify(alloc, &make, &live, bias, &format!("inplace reopen@{step}"));
        }
    }

    // Final integrity pass.
    let _alloc = reopen_and_verify(alloc, &make, &live, bias, "inplace final");
}

macro_rules! inplace_fault_suite {
    ($mod_name:ident, $make:expr, $salt:expr) => {
        mod $mod_name {
            use super::*;
            #[test]
            fn fault_fuzz() {
                super::run_inplace_fault_fuzz($make, $salt);
            }
        }
    };
}

inplace_fault_suite!(first_fit, make_allocator!(FirstFitBStackAllocator), 0x1B1B);
inplace_fault_suite!(
    ghost_tree,
    make_allocator!(GhostTreeBstackAllocator),
    0x2B2B
);
inplace_fault_suite!(
    segregated,
    make_allocator!(SegregatedBStackAllocator),
    0x7B7B
);