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preallocate.go
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preallocate.go
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// Copyright 2015 CoreOS, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// +build linux
package fileutil
import (
"os"
"syscall"
)
// Preallocate tries to allocate the space for given
// file. This operation is only supported on linux by a
// few filesystems (btrfs, ext4, etc.).
// If the operation is unsupported, no error will be returned.
// Otherwise, the error encountered will be returned.
func Preallocate(f *os.File, sizeInBytes int) error {
// use mode = 1 to keep size
// see FALLOC_FL_KEEP_SIZE
err := syscall.Fallocate(int(f.Fd()), 1, 0, int64(sizeInBytes))
if err != nil {
errno, ok := err.(syscall.Errno)
// treat not support as nil error
if ok && errno == syscall.ENOTSUP {
return nil
}
return err
}
return nil
}