feat(artifacts): add bounded reconciliation

crates/crank-artifacts/src/housekeeping.rs

@@ -1,13 +1,66 @@
 use std::{
+    fmt,
     os::fd::AsRawFd,
     time::{Duration, SystemTime, UNIX_EPOCH},
 };
 
 use crate::{
-    ArtifactError, ArtifactStore,
-    store::{RootLock, ensure_root_unchanged, fsync_fd, open_existing_dir, unlinkat},
+    ArtifactError, ArtifactStore, ReconciliationMutation, ReconciliationNamespace,
+    ReconciliationScan,
+    store::{
+        QUARANTINE_DIR, RootLock, check_file, checkpointed, ensure_root_unchanged, fsync_fd,
+        open_existing_dir, open_or_create_dir, rename_no_replace_at, stat_fd, unlinkat,
+    },
 };
 
+const FINAL_NAMESPACE: u8 = 0;
+const QUARANTINE_NAMESPACE: u8 = 1;
+
+/// Opaque continuation for a bounded reconciliation traversal.  It is valid
+/// only for the unchanged pinned root from which it was returned.
+pub struct ReconciliationCursor {
+    root_dev: u64,
+    root_ino: u64,
+    namespace: u8,
+    shard: u8,
+    position: i64,
+}
+
+impl fmt::Debug for ReconciliationCursor {
+    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
+        formatter.write_str("ReconciliationCursor(..)")
+    }
+}
+
+/// Opaque, inode-bound evidence for one valid final or quarantined artifact.
+/// It intentionally exposes neither its digest nor filesystem path.
+#[derive(Clone)]
+pub struct ReconciliationCandidate {
+    root_dev: u64,
+    root_ino: u64,
+    namespace: ReconciliationNamespace,
+    shard: String,
+    shard_dev: u64,
+    shard_ino: u64,
+    name: String,
+    dev: u64,
+    ino: u64,
+    modified_seconds: i64,
+    modified_nanoseconds: i64,
+}
+
+impl fmt::Debug for ReconciliationCandidate {
+    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
+        formatter.write_str("ReconciliationCandidate(..)")
+    }
+}
+
+impl ReconciliationCandidate {
+    pub fn namespace(&self) -> ReconciliationNamespace {
+        self.namespace
+    }
+}
+
 /// Opaque, single-use evidence that a particular stale temporary inode was
 /// observed under this store's pinned root. It is not a blob reference.
 #[derive(Debug)]
@@ -30,6 +83,259 @@ pub struct TempScan {
 }
 
 impl ArtifactStore {
+    /// Streams valid final and quarantine entries with an opaque continuation.
+    /// Neither the report nor the returned capabilities disclose paths/digests.
+    pub fn scan_reconciliation(
+        &self,
+        continuation: Option<ReconciliationCursor>,
+        scan_budget: usize,
+        result_limit: usize,
+    ) -> Result<(ReconciliationScan, Vec<ReconciliationCandidate>), ArtifactError> {
+        let root = self.root()?;
+        let _lock = RootLock::shared(root)?;
+        ensure_root_unchanged(root)?;
+        let mut cursor = match continuation {
+            Some(cursor) => {
+                if cursor.root_dev != root.dev
+                    || cursor.root_ino != root.ino
+                    || cursor.namespace > QUARANTINE_NAMESPACE
+                {
+                    return Err(ArtifactError::UnsafeRoot);
+                }
+                cursor
+            }
+            None => reconciliation_cursor(root.dev, root.ino, FINAL_NAMESPACE, 0, 0),
+        };
+        let mut report = ReconciliationScan::empty(None);
+        if scan_budget == 0 || result_limit == 0 {
+            report.continuation = Some(cursor);
+            return Ok((report, Vec::new()));
+        }
+
+        let mut remaining = scan_budget;
+        let mut entries = Vec::new();
+        while cursor.namespace <= QUARANTINE_NAMESPACE {
+            if remaining == 0 || entries.len() == result_limit {
+                report.continuation = Some(cursor);
+                return Ok((report, entries));
+            }
+            let namespace_name = namespace_name(cursor.namespace);
+            let namespace = match open_existing_dir(root.fd.as_raw_fd(), namespace_name) {
+                Ok(fd) => fd,
+                Err(ArtifactError::NotFound) => {
+                    advance_namespace(&mut cursor);
+                    continue;
+                }
+                Err(error) => return Err(error),
+            };
+            loop {
+                if remaining == 0 {
+                    report.continuation = Some(cursor);
+                    return Ok((report, entries));
+                }
+                let shard_name = format!("{:02x}", cursor.shard);
+                let shard = match open_existing_dir(namespace.as_raw_fd(), shard_name.as_bytes()) {
+                    Ok(fd) => fd,
+                    Err(ArtifactError::NotFound) => {
+                        consume_scan_work(&mut report, &mut remaining);
+                        if cursor.shard == u8::MAX {
+                            break;
+                        }
+                        advance_shard(&mut cursor);
+                        continue;
+                    }
+                    Err(error) => return Err(error),
+                };
+                let shard_stat = stat_fd(shard.as_raw_fd())?;
+                let mut directory = DirectoryStream::open(shard.as_raw_fd(), cursor.position)?;
+                loop {
+                    if remaining == 0 || entries.len() == result_limit {
+                        report.continuation = Some(cursor);
+                        return Ok((report, entries));
+                    }
+                    let Some((name, after)) = directory.next()? else {
+                        // An empty directory still consumes one bounded
+                        // traversal unit, so a sparse namespace cannot make
+                        // us probe all 256 shards in one page.
+                        consume_scan_work(&mut report, &mut remaining);
+                        break;
+                    };
+                    cursor.position = after;
+                    consume_scan_work(&mut report, &mut remaining);
+                    let Ok(name) = String::from_utf8(name) else {
+                        report.malformed += 1;
+                        continue;
+                    };
+                    if !valid_final_name(&name, &shard_name) {
+                        report.malformed += 1;
+                        continue;
+                    }
+                    #[cfg(debug_assertions)]
+                    let _ = crate::test_support::checkpoint("reconciliation_before_stat");
+                    let stat = match checkpointed("reconciliation_stat", || {
+                        nofollow_stat(shard.as_raw_fd(), &name)
+                    }) {
+                        Ok(stat) => stat,
+                        Err(ArtifactError::NotFound) => {
+                            // The entry was concurrently removed.  It is no
+                            // longer retryable, so the cursor may advance.
+                            continue;
+                        }
+                        Err(ArtifactError::UnsafeRoot) => {
+                            report.unsafe_entries += 1;
+                            continue;
+                        }
+                        Err(error) => return Err(error),
+                    };
+                    if check_file(&stat).is_err() {
+                        report.unsafe_entries += 1;
+                        continue;
+                    }
+                    let namespace = if cursor.namespace == FINAL_NAMESPACE {
+                        report.final_entries += 1;
+                        ReconciliationNamespace::Final
+                    } else {
+                        report.quarantined_entries += 1;
+                        ReconciliationNamespace::Quarantine
+                    };
+                    entries.push(ReconciliationCandidate {
+                        root_dev: root.dev,
+                        root_ino: root.ino,
+                        namespace,
+                        shard: shard_name.clone(),
+                        shard_dev: shard_stat.st_dev,
+                        shard_ino: shard_stat.st_ino,
+                        name,
+                        dev: stat.st_dev,
+                        ino: stat.st_ino,
+                        modified_seconds: stat.st_mtime,
+                        modified_nanoseconds: stat.st_mtime_nsec,
+                    });
+                    // The continuation is deliberately kept at `after`,
+                    // immediately before the next unissued item.
+                }
+                if cursor.shard == u8::MAX {
+                    break;
+                }
+                advance_shard(&mut cursor);
+            }
+            advance_namespace(&mut cursor);
+        }
+        Ok((report, entries))
+    }
+
+    /// Moves a revalidated final inode into the private quarantine namespace
+    /// without replacing any existing quarantine inode.
+    pub fn quarantine_reconciliation(
+        &self,
+        candidate: ReconciliationCandidate,
+    ) -> Result<ReconciliationMutation, ArtifactError> {
+        if candidate.namespace != ReconciliationNamespace::Final {
+            return Err(ArtifactError::UnsafeRoot);
+        }
+        let root = self.root()?;
+        let _lock = RootLock::exclusive(root)?;
+        ensure_reconciliation_root(root, &candidate)?;
+        let final_root = open_existing_dir(root.fd.as_raw_fd(), namespace_name(FINAL_NAMESPACE))?;
+        let final_shard = open_existing_dir(final_root.as_raw_fd(), candidate.shard.as_bytes())?;
+        match revalidate_candidate(&candidate, final_shard.as_raw_fd()) {
+            Ok(()) => {}
+            Err(ArtifactError::NotFound) => {
+                return self.recover_quarantine(root, &candidate);
+            }
+            Err(ArtifactError::UnsafeRoot) => {
+                return match self.recover_quarantine(root, &candidate) {
+                    Ok(outcome) => Ok(outcome),
+                    Err(ArtifactError::NotFound) => Err(ArtifactError::UnsafeRoot),
+                    Err(error) => Err(error),
+                };
+            }
+            Err(error) => return Err(error),
+        }
+        let quarantine_root = open_or_create_dir(root.fd.as_raw_fd(), QUARANTINE_DIR)?;
+        let quarantine_shard =
+            open_or_create_dir(quarantine_root.as_raw_fd(), candidate.shard.as_bytes())?;
+        match checkpointed("reconciliation_quarantine_rename", || {
+            rename_no_replace_at(
+                final_shard.as_raw_fd(),
+                candidate.name.as_bytes(),
+                quarantine_shard.as_raw_fd(),
+                candidate.name.as_bytes(),
+            )
+        })? {
+            true => match fsync_quarantine_dirs(&final_shard, &quarantine_shard) {
+                Ok(()) => Ok(ReconciliationMutation::Quarantined),
+                Err(_) => Ok(ReconciliationMutation::Retryable),
+            },
+            false => self.recover_quarantine(root, &candidate),
+        }
+    }
+
+    /// Idempotently removes a revalidated quarantined inode and fsyncs its
+    /// directory. An fsync ambiguity is explicitly retryable.
+    pub fn delete_quarantined_reconciliation(
+        &self,
+        candidate: ReconciliationCandidate,
+    ) -> Result<ReconciliationMutation, ArtifactError> {
+        if candidate.namespace != ReconciliationNamespace::Quarantine {
+            return Err(ArtifactError::UnsafeRoot);
+        }
+        let root = self.root()?;
+        let _lock = RootLock::exclusive(root)?;
+        ensure_reconciliation_root(root, &candidate)?;
+        let quarantine_root = match open_existing_dir(root.fd.as_raw_fd(), QUARANTINE_DIR) {
+            Ok(fd) => fd,
+            Err(ArtifactError::NotFound) => return Ok(ReconciliationMutation::AlreadyAbsent),
+            Err(error) => return Err(error),
+        };
+        let shard = match open_existing_dir(quarantine_root.as_raw_fd(), candidate.shard.as_bytes())
+        {
+            Ok(fd) => fd,
+            Err(ArtifactError::NotFound) => return Ok(ReconciliationMutation::AlreadyAbsent),
+            Err(error) => return Err(error),
+        };
+        match revalidate_candidate(&candidate, shard.as_raw_fd()) {
+            Ok(()) => {}
+            Err(ArtifactError::NotFound) => {
+                return fsync_mutation(&shard, ReconciliationMutation::AlreadyAbsent);
+            }
+            Err(error) => return Err(error),
+        }
+        match checkpointed("reconciliation_delete_unlink", || {
+            unlinkat(shard.as_raw_fd(), candidate.name.as_bytes())
+        }) {
+            Ok(()) => fsync_mutation(&shard, ReconciliationMutation::Deleted),
+            Err(ArtifactError::NotFound) => {
+                fsync_mutation(&shard, ReconciliationMutation::AlreadyAbsent)
+            }
+            Err(error) => Err(error),
+        }
+    }
+
+    fn recover_quarantine(
+        &self,
+        root: &crate::store::Root,
+        candidate: &ReconciliationCandidate,
+    ) -> Result<ReconciliationMutation, ArtifactError> {
+        let final_root = open_existing_dir(root.fd.as_raw_fd(), namespace_name(FINAL_NAMESPACE))?;
+        let final_shard = open_existing_dir(final_root.as_raw_fd(), candidate.shard.as_bytes())?;
+        let quarantine_root = match open_existing_dir(root.fd.as_raw_fd(), QUARANTINE_DIR) {
+            Ok(fd) => fd,
+            Err(ArtifactError::NotFound) => return Err(ArtifactError::NotFound),
+            Err(error) => return Err(error),
+        };
+        let shard = match open_existing_dir(quarantine_root.as_raw_fd(), candidate.shard.as_bytes())
+        {
+            Ok(fd) => fd,
+            Err(ArtifactError::NotFound) => return Err(ArtifactError::NotFound),
+            Err(error) => return Err(error),
+        };
+        revalidate_moved_candidate(candidate, shard.as_raw_fd())?;
+        match fsync_quarantine_dirs(&final_shard, &shard) {
+            Ok(()) => Ok(ReconciliationMutation::AlreadyQuarantined),
+            Err(_) => Ok(ReconciliationMutation::Retryable),
+        }
+    }
     /// Streams temporary entries, reading at most `scan_budget` directory
     /// entries and returning at most `result_limit` stale capabilities.
     pub fn scan_stale_temps(
@@ -147,6 +453,187 @@ impl ArtifactStore {
     }
 }
 
+fn reconciliation_cursor(
+    root_dev: u64,
+    root_ino: u64,
+    namespace: u8,
+    shard: u8,
+    position: i64,
+) -> ReconciliationCursor {
+    ReconciliationCursor {
+        root_dev,
+        root_ino,
+        namespace,
+        shard,
+        position,
+    }
+}
+
+fn namespace_name(namespace: u8) -> &'static [u8] {
+    match namespace {
+        FINAL_NAMESPACE => b"sha256",
+        QUARANTINE_NAMESPACE => QUARANTINE_DIR,
+        _ => unreachable!("validated reconciliation namespace"),
+    }
+}
+
+fn advance_shard(cursor: &mut ReconciliationCursor) {
+    debug_assert_ne!(cursor.shard, u8::MAX);
+    cursor.shard += 1;
+    cursor.position = 0;
+}
+
+fn advance_namespace(cursor: &mut ReconciliationCursor) {
+    cursor.namespace = cursor.namespace.saturating_add(1);
+    cursor.shard = 0;
+    cursor.position = 0;
+}
+
+fn consume_scan_work(report: &mut ReconciliationScan, remaining: &mut usize) {
+    debug_assert!(*remaining > 0);
+    *remaining -= 1;
+    report.scanned += 1;
+}
+
+fn ensure_reconciliation_root(
+    root: &crate::store::Root,
+    candidate: &ReconciliationCandidate,
+) -> Result<(), ArtifactError> {
+    ensure_root_unchanged(root)?;
+    if candidate.root_dev != root.dev
+        || candidate.root_ino != root.ino
+        || candidate.shard.len() != 2
+        || !candidate.shard.bytes().all(is_lower_hex)
+        || !valid_final_name(&candidate.name, &candidate.shard)
+    {
+        return Err(ArtifactError::UnsafeRoot);
+    }
+    Ok(())
+}
+
+fn revalidate_candidate(
+    candidate: &ReconciliationCandidate,
+    shard: i32,
+) -> Result<(), ArtifactError> {
+    let shard_stat = stat_fd(shard)?;
+    if shard_stat.st_dev != candidate.shard_dev || shard_stat.st_ino != candidate.shard_ino {
+        return Err(ArtifactError::UnsafeRoot);
+    }
+    let stat = nofollow_stat(shard, &candidate.name)?;
+    if stat.st_dev != candidate.dev
+        || stat.st_ino != candidate.ino
+        || stat.st_mtime != candidate.modified_seconds
+        || stat.st_mtime_nsec != candidate.modified_nanoseconds
+    {
+        return Err(ArtifactError::UnsafeRoot);
+    }
+    check_file(&stat).map_err(|_| ArtifactError::UnsafeRoot)
+}
+
+/// Recovery follows a successful cross-directory rename. The candidate remains
+/// bound to the original final shard, so the quarantine shard identity cannot
+/// equal its recorded shard identity; only the canonical name and inode are
+/// revalidated here.
+fn revalidate_moved_candidate(
+    candidate: &ReconciliationCandidate,
+    shard: i32,
+) -> Result<(), ArtifactError> {
+    let stat = nofollow_stat(shard, &candidate.name)?;
+    if stat.st_dev != candidate.dev
+        || stat.st_ino != candidate.ino
+        || stat.st_mtime != candidate.modified_seconds
+        || stat.st_mtime_nsec != candidate.modified_nanoseconds
+    {
+        return Err(ArtifactError::UnsafeRoot);
+    }
+    check_file(&stat).map_err(|_| ArtifactError::UnsafeRoot)
+}
+
+fn fsync_mutation(
+    shard: &std::os::fd::OwnedFd,
+    success: ReconciliationMutation,
+) -> Result<ReconciliationMutation, ArtifactError> {
+    match checkpointed("reconciliation_delete_fsync", || {
+        fsync_fd(shard.as_raw_fd())
+    }) {
+        Ok(()) => Ok(success),
+        Err(_) => Ok(ReconciliationMutation::Retryable),
+    }
+}
+
+/// Persist both directory entry changes even if the first fsync reports an
+/// error.  Either failure remains an ambiguity, but skipping the second fsync
+/// would needlessly enlarge the crash window.
+fn fsync_quarantine_dirs(
+    final_shard: &std::os::fd::OwnedFd,
+    quarantine_shard: &std::os::fd::OwnedFd,
+) -> Result<(), ArtifactError> {
+    let source = checkpointed("reconciliation_quarantine_source_fsync", || {
+        fsync_fd(final_shard.as_raw_fd())
+    });
+    let destination = checkpointed("reconciliation_quarantine_destination_fsync", || {
+        fsync_fd(quarantine_shard.as_raw_fd())
+    });
+    source.and(destination)
+}
+
+fn valid_final_name(name: &str, shard: &str) -> bool {
+    name.len() == 64 && name.starts_with(shard) && name.bytes().all(is_lower_hex)
+}
+
+struct DirectoryStream {
+    directory: *mut libc::DIR,
+}
+
+impl DirectoryStream {
+    fn open(parent: i32, position: i64) -> Result<Self, ArtifactError> {
+        let duplicate = crate::store::duplicate_fd(parent)?;
+        let raw = std::os::fd::IntoRawFd::into_raw_fd(duplicate);
+        let directory = unsafe { libc::fdopendir(raw) };
+        if directory.is_null() {
+            unsafe {
+                libc::close(raw);
+            }
+            return Err(ArtifactError::Storage);
+        }
+        if position != 0 {
+            unsafe {
+                libc::seekdir(directory, position as libc::c_long);
+            }
+        }
+        Ok(Self { directory })
+    }
+
+    fn next(&mut self) -> Result<Option<(Vec<u8>, i64)>, ArtifactError> {
+        loop {
+            unsafe {
+                *libc::__errno_location() = 0;
+            }
+            let entry = unsafe { libc::readdir(self.directory) };
+            if entry.is_null() {
+                if unsafe { *libc::__errno_location() } != 0 {
+                    return Err(ArtifactError::Storage);
+                }
+                return Ok(None);
+            }
+            let after = unsafe { libc::telldir(self.directory) } as i64;
+            let name = unsafe { std::ffi::CStr::from_ptr((*entry).d_name.as_ptr()) }.to_bytes();
+            if name == b"." || name == b".." {
+                continue;
+            }
+            return Ok(Some((name.to_vec(), after)));
+        }
+    }
+}
+
+impl Drop for DirectoryStream {
+    fn drop(&mut self) {
+        unsafe {
+            libc::closedir(self.directory);
+        }
+    }
+}
+
 fn list_names(
     parent: i32,
     remaining: &mut usize,

crates/crank-artifacts/src/lib.rs

@@ -18,8 +18,9 @@ mod store;
 pub mod test_support;
 
 pub use error::ArtifactError;
-pub use housekeeping::{StaleTemp, TempScan};
+pub use housekeeping::{ReconciliationCandidate, ReconciliationCursor, StaleTemp, TempScan};
 pub use model::{
-    ArtifactRef, MAX_ARTIFACT_BYTES, MAX_SOURCE_BYTES, RegisteredArtifact, StoredArtifact,
+    ArtifactRef, MAX_ARTIFACT_BYTES, MAX_SOURCE_BYTES, ReconciliationMutation,
+    ReconciliationNamespace, ReconciliationScan, RegisteredArtifact, StoredArtifact,
 };
 pub use store::ArtifactStore;

crates/crank-artifacts/src/model.rs

@@ -77,6 +77,55 @@ pub struct RegisteredArtifact {
     pub(crate) size_bytes: usize,
 }
 
+/// Namespace in which reconciliation observed an artifact inode.  It does not
+/// disclose the artifact's digest or filesystem location.
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub enum ReconciliationNamespace {
+    Final,
+    Quarantine,
+}
+
+/// Bounded, redacted progress report from a reconciliation page.
+///
+/// `continuation` is opaque evidence for resuming an unchanged namespace. It
+/// intentionally cannot be created from a caller-supplied path or digest.
+#[derive(Debug)]
+pub struct ReconciliationScan {
+    pub scanned: usize,
+    pub malformed: usize,
+    pub unsafe_entries: usize,
+    pub final_entries: usize,
+    pub quarantined_entries: usize,
+    pub continuation: Option<crate::ReconciliationCursor>,
+}
+
+impl ReconciliationScan {
+    pub(crate) fn empty(continuation: Option<crate::ReconciliationCursor>) -> Self {
+        Self {
+            scanned: 0,
+            malformed: 0,
+            unsafe_entries: 0,
+            final_entries: 0,
+            quarantined_entries: 0,
+            continuation,
+        }
+    }
+}
+
+/// The durable/retryable result of a reconciliation mutation.
+///
+/// A successful rename or unlink followed by an fsync failure is intentionally
+/// reported as `Retryable`: a subsequent bounded scan determines the durable
+/// state without treating the operation as a failed no-op.
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub enum ReconciliationMutation {
+    Quarantined,
+    AlreadyQuarantined,
+    Deleted,
+    AlreadyAbsent,
+    Retryable,
+}
+
 impl RegisteredArtifact {
     pub fn artifact_ref(&self) -> &ArtifactRef {
         &self.artifact_ref

crates/crank-artifacts/src/store.rs

@@ -16,6 +16,7 @@ use sha2::{Digest, Sha256};
 use crate::{ArtifactError, ArtifactRef, MAX_ARTIFACT_BYTES, RegisteredArtifact, StoredArtifact};
 
 const SHA_DIR: &[u8] = b"sha256";
+pub(crate) const QUARANTINE_DIR: &[u8] = b"quarantine";
 const TEMP_PREFIX: &str = ".crank-artifact-tmp-v1-";
 const RESOLVE_NO_SYMLINKS: u64 = 0x04;
 static TEMP_SEQUENCE: AtomicU64 = AtomicU64::new(0);
@@ -382,7 +383,7 @@ fn check_private_dir(stat: &libc::stat) -> Result<(), ArtifactError> {
     }
     Ok(())
 }
-fn stat_fd(fd: i32) -> Result<libc::stat, ArtifactError> {
+pub(crate) fn stat_fd(fd: i32) -> Result<libc::stat, ArtifactError> {
     let mut stat = unsafe { std::mem::zeroed() };
     if unsafe { libc::fstat(fd, &mut stat) } != 0 {
         Err(ArtifactError::Storage)
@@ -390,7 +391,7 @@ fn stat_fd(fd: i32) -> Result<libc::stat, ArtifactError> {
         Ok(stat)
     }
 }
-fn check_file(stat: &libc::stat) -> Result<(), ArtifactError> {
+pub(crate) fn check_file(stat: &libc::stat) -> Result<(), ArtifactError> {
     if (stat.st_mode & libc::S_IFMT) != libc::S_IFREG
         || stat.st_uid != unsafe { libc::geteuid() }
         || stat.st_nlink != 1
@@ -508,7 +509,7 @@ fn write_all(fd: &OwnedFd, bytes: &[u8]) -> Result<(), ArtifactError> {
 
 /// Debug/test-only fault seam coupled to one syscall wrapper. `Fail` models a
 /// syscall that did not run; crash/hold actions happen only after success.
-fn checkpointed<T>(
+pub(crate) fn checkpointed<T>(
     stage: &str,
     operation: impl FnOnce() -> Result<T, ArtifactError>,
 ) -> Result<T, ArtifactError> {
@@ -608,14 +609,22 @@ fn chmod_read_only(fd: i32) -> Result<(), ArtifactError> {
     }
 }
 fn rename_no_replace(parent: i32, old: &[u8], new: &[u8]) -> Result<bool, ArtifactError> {
+    rename_no_replace_at(parent, old, parent, new)
+}
+pub(crate) fn rename_no_replace_at(
+    old_parent: i32,
+    old: &[u8],
+    new_parent: i32,
+    new: &[u8],
+) -> Result<bool, ArtifactError> {
     let old = c_name(old)?;
     let new = c_name(new)?;
     let result = unsafe {
         libc::syscall(
             libc::SYS_renameat2,
-            parent,
+            old_parent,
             old.as_ptr(),
-            parent,
+            new_parent,
             new.as_ptr(),
             libc::RENAME_NOREPLACE,
         )