mirror of
https://github.com/versity/versitygw.git
synced 2026-09-23 16:34:18 +00:00
Ben McClelland
062bf0bf47
This change introduces an opt-in O_DIRECT mode for POSIX object data paths while keeping behavior safe and predictable across different filesystems and kernel constraints. We now use direct I/O when available and beneficial, but preserve correctness by falling back to buffered I/O when runtime read behavior indicates alignment or capability mismatches. The implementation keeps fast paths available for full-object reads and descriptor-to-descriptor copy operations so kernel-level optimizations can still be used where possible. At the same time, it avoids global assumptions from single runtime failures and performs fallback at the stream level so requests can continue successfully without broad feature disablement.
110 lines
2.9 KiB
Go
110 lines
2.9 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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package posix
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import (
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"errors"
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"fmt"
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"io"
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"math/rand"
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"os"
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"strconv"
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"syscall"
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"time"
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)
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const odirectMinWriteAlign = 512
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func (tmp *tmpfile) Write(b []byte) (int, error) {
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if int64(len(b)) > tmp.size {
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return 0, fmt.Errorf("write exceeds content length %v", tmp.size)
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}
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if tmp.useODirect && !isODirectLenAligned(len(b)) {
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if err := tmp.switchToBufferedAtCurrentOffset(fmt.Sprintf("unaligned write length: len=%d len%%512=%d", len(b), len(b)%odirectMinWriteAlign)); err != nil {
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return 0, err
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}
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}
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n, err := tmp.f.Write(b)
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if err != nil && n == 0 && tmp.useODirect && isODirectRuntimeFallbackErr(err) {
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warnODirectUnsupportedOnce("tmpfile.Write", err)
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if fallbackErr := tmp.switchToBufferedAtCurrentOffset("O_DIRECT write failure"); fallbackErr != nil {
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return 0, fallbackErr
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}
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n, err = tmp.f.Write(b)
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}
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tmp.size -= int64(n)
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return n, err
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}
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func (tmp *tmpfile) switchToBufferedAtCurrentOffset(reason string) error {
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offset, seekErr := tmp.f.Seek(0, io.SeekCurrent)
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if seekErr != nil {
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return fmt.Errorf("capture write offset before fallback reopen: %w", seekErr)
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}
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name := tmp.f.Name()
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f, openErr := os.OpenFile(name, os.O_RDWR, 0)
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if openErr != nil {
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return fmt.Errorf("reopen temp file in buffered mode after O_DIRECT fallback (%s): %w", reason, openErr)
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}
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if _, seekErr = f.Seek(offset, io.SeekStart); seekErr != nil {
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f.Close()
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return fmt.Errorf("restore write offset after fallback reopen: %w", seekErr)
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}
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if closeErr := tmp.f.Close(); closeErr != nil {
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f.Close()
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return fmt.Errorf("close O_DIRECT temp file after fallback reopen: %w", closeErr)
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}
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tmp.f = f
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if tmp.isOTmp {
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tmp.procFDName = strconv.Itoa(int(f.Fd()))
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}
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tmp.useODirect = false
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return nil
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}
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func isODirectLenAligned(n int) bool {
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return n%odirectMinWriteAlign == 0
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}
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func isODirectRuntimeFallbackErr(err error) bool {
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return errors.Is(err, syscall.EINVAL) ||
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errors.Is(err, syscall.EOPNOTSUPP) ||
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errors.Is(err, syscall.ENOTSUP)
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}
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func (tmp *tmpfile) File() *os.File {
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return tmp.f
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}
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func sleepWithJitter(backoffMs int) {
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if backoffMs <= 1 {
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time.Sleep(1 * time.Millisecond)
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return
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}
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maxJitter := max(1, backoffMs/4)
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jitter := rand.Intn((maxJitter*2)+1) - maxJitter
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sleepMs := max(backoffMs+jitter, 1)
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time.Sleep(time.Duration(sleepMs) * time.Millisecond)
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}
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