package restorer import ( "os" "golang.org/x/sys/unix" ) func preallocateFile(wr *os.File, size int64) error { // try contiguous first fst := unix.Fstore_t{ Flags: unix.F_ALLOCATECONTIG | unix.F_ALLOCATEALL, Posmode: unix.F_PEOFPOSMODE, Offset: 0, Length: size, } err := unix.FcntlFstore(wr.Fd(), unix.F_PREALLOCATE, &fst) if err == nil { return nil } // just take preallocation in any form, but still ask for everything fst.Flags = unix.F_ALLOCATEALL err = unix.FcntlFstore(wr.Fd(), unix.F_PREALLOCATE, &fst) return err }