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// Copyright 2019 Intel Corporation. All Rights Reserved.
//
// Copyright 2017 The Chromium OS Authors. All rights reserved.
//
// SPDX-License-Identifier: BSD-3-Clause
//! Enum and function for dealing with an allocated disk space
//! by [`fallocate`](http://man7.org/linux/man-pages/man2/fallocate.2.html).
use std::os::unix::io::AsRawFd;
use crate::errno::{errno_result, Error, Result};
/// Operation to be performed on a given range when calling [`fallocate`]
///
/// [`fallocate`]: fn.fallocate.html
pub enum FallocateMode {
/// Deallocating file space.
PunchHole,
/// Zeroing file space.
ZeroRange,
}
/// A safe wrapper for [`fallocate`](http://man7.org/linux/man-pages/man2/fallocate.2.html).
///
/// Manipulate the file space with specified operation parameters.
///
/// # Arguments
///
/// * `file`: the file to be manipulate.
/// * `mode`: specify the operation to be performed on the given range.
/// * `keep_size`: file size won't be changed even if `offset` + `len` is greater
/// than the file size.
/// * `offset`: the position that manipulates the file from.
/// * `size`: the bytes of the operation range.
///
/// # Examples
///
/// ```
/// extern crate vmm_sys_util;
/// # use std::fs::OpenOptions;
/// # use std::path::PathBuf;
/// use vmm_sys_util::fallocate::{fallocate, FallocateMode};
/// use vmm_sys_util::tempdir::TempDir;
///
/// let tempdir = TempDir::new_with_prefix("/tmp/fallocate_test").unwrap();
/// let mut path = PathBuf::from(tempdir.as_path());
/// path.push("file");
/// let mut f = OpenOptions::new()
/// .read(true)
/// .write(true)
/// .create(true)
/// .open(&path)
/// .unwrap();
/// fallocate(&f, FallocateMode::PunchHole, true, 0, 1).unwrap();
/// ```
pub fn fallocate(
file: &dyn AsRawFd,
mode: FallocateMode,
keep_size: bool,
offset: u64,
len: u64,
) -> Result<()> {
let offset = if offset > libc::off64_t::max_value() as u64 {
return Err(Error::new(libc::EINVAL));
} else {
offset as libc::off64_t
};
let len = if len > libc::off64_t::max_value() as u64 {
return Err(Error::new(libc::EINVAL));
} else {
len as libc::off64_t
};
let mut mode = match mode {
FallocateMode::PunchHole => libc::FALLOC_FL_PUNCH_HOLE,
FallocateMode::ZeroRange => libc::FALLOC_FL_ZERO_RANGE,
};
if keep_size {
mode |= libc::FALLOC_FL_KEEP_SIZE;
}
// SAFETY: Safe since we pass in a valid fd and fallocate mode, validate offset and len,
// and check the return value.
let ret = unsafe { libc::fallocate64(file.as_raw_fd(), mode, offset, len) };
if ret < 0 {
errno_result()
} else {
Ok(())
}
}
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