mirror of
https://github.com/versity/versitygw.git
synced 2026-09-22 07:54:14 +00:00
Ben McClelland
9c363b280a
Conditional PUTs require a lock primitive that excludes competing gateway processes sharing a backend filesystem. A successful flock call does not prove that property: some clustered filesystem configurations accept flock but scope it to one node, silently leaving cross-gateway check-and-publish races open. Add an object-lock mode that lets operators select flock or fcntl for filesystems where that primitive is cluster-coherent, local for the existing per-process behavior, or none to reject conditional writes with NotImplemented. Keep the legacy disable flag as an alias for local. Shared lock modes now verify the selected primitive on the root lock filesystem during startup and fail closed if it cannot be used. Runtime lock failures no longer silently downgrade to process-local exclusion. The startup check cannot establish cross-node coherence, so that remains an explicit operator requirement. ScoutFS defaults to none since posix locks are not cluster consistent, but allow setting local for single node deployments. Fixes #2351
64 lines
1.8 KiB
Go
64 lines
1.8 KiB
Go
// Copyright 2026 Versity Software
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// This file is licensed under the Apache License, Version 2.0
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// (the "License"); you may not use this file except in compliance
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// with the License. You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing,
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// software distributed under the License is distributed on an
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// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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// KIND, either express or implied. See the License for the
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// specific language governing permissions and limitations
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// under the License.
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//go:build windows
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package posix
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import (
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"context"
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"errors"
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"fmt"
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"os"
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"time"
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"golang.org/x/sys/windows"
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)
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// lockFileExclusive takes an exclusive lock on f via LockFileEx, polling with
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// backoff so that context cancellation is honored while waiting. The lock is
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// released when f is closed or the process exits.
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func lockFileExclusive(ctx context.Context, f *os.File, mode ObjectLockMode) error {
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if mode != ObjectLockModeFlock {
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return errors.New("object lock mode fcntl is not supported on Windows")
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}
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backoff := objLockInitialBackoff
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for {
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ol := new(windows.Overlapped)
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err := windows.LockFileEx(windows.Handle(f.Fd()),
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windows.LOCKFILE_EXCLUSIVE_LOCK|windows.LOCKFILE_FAIL_IMMEDIATELY,
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0, 1, 0, ol)
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if err == nil {
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return nil
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}
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if !errors.Is(err, windows.ERROR_LOCK_VIOLATION) {
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return err
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}
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select {
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case <-ctx.Done():
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return ctx.Err()
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case <-time.After(backoff):
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}
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backoff = min(backoff*2, objLockMaxBackoff)
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}
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}
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func validateObjectLockMode(mode ObjectLockMode) error {
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if mode == ObjectLockModeFcntl {
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return fmt.Errorf("object lock mode %q is not supported on Windows; use flock, local, or none", mode)
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}
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return nil
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}
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