Michael Stapelberg
942a8faaca
This regressed with commit 64f7f697df.
Thanks to https://github.com/emcfarlane for the report.
related to https://github.com/gokrazy/gokrazy/issues/22
40 lines
1.1 KiB
Go
40 lines
1.1 KiB
Go
package packer
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import (
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"errors"
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"log"
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"os"
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"golang.org/x/sys/unix"
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)
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const (
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// On macOS, sys/disk.h declares DKIOCSYNCHRONIZECACHE.
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// macOS disk drivers like IOMediaBSDClient handle this ioctl
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// by flushing the device write cache.
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DKIOCSYNCHRONIZECACHE = 0x20006416 // _IO('d', 22)
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)
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func syncFile(f *os.File) error {
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// Go’s f.Sync is fcntl(F_FULLFSYNC) on macOS,
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// which works for files, but not device nodes (like /dev/diskN),
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// where macOS returns ENOTTY.
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err := f.Sync()
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if !errors.Is(err, unix.ENOTTY) {
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return err
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}
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// Encountered ENOTTY, fall back to fsync(2)
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// to write all buffered data to the driver (e.g. SD card driver).
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if err := unix.Fsync(int(f.Fd())); err != nil {
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return err
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}
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// Flush the device’s cache as well,
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// which may or may not have any effect,
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// depending on the device, e.g. USB card readers.
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// This is what macOS does when ejecting the device.
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if _, _, errno := unix.Syscall(unix.SYS_IOCTL, f.Fd(), DKIOCSYNCHRONIZECACHE, 0); errno != 0 {
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log.Printf("flushing write cache of %s: %v", f.Name(), errno)
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}
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return nil
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}
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