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proxmox/tools/fs: create tmpfile helper

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by factoring out the code we had in 'replace_file'

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
This commit is contained in:
Dominik Csapak 2020-09-25 16:13:15 +02:00 committed by Dietmar Maurer
parent 115f003742
commit 5440c65787
1 changed files with 24 additions and 15 deletions
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39
proxmox/src/tools/fs.rs
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@ -4,7 +4,7 @@ use std::ffi::CStr;
use std::fs::{File, OpenOptions};
use std::io::{self, BufRead, BufReader, Write};
use std::os::unix::io::{AsRawFd, FromRawFd, RawFd};
use std::path::Path;
use std::path::{Path, PathBuf};
use std::time::Duration;
use anyhow::{bail, format_err, Error};
@ -121,14 +121,12 @@ pub fn file_read_firstline<P: AsRef<Path>>(path: P) -> Result<String, Error> {
.map_err(|err: Error| format_err!("unable to read {:?} - {}", path, err))
}
/// Atomically replace a file.
///
/// This first creates a temporary file and then rotates it in place.
pub fn replace_file<P: AsRef<Path>>(
/// Takes a Path and CreateOptions, creates a tmpfile from it and returns
/// a RawFd and PathBuf for it
pub fn make_tmp_file<P: AsRef<Path>>(
path: P,
data: &[u8],
options: CreateOptions,
) -> Result<(), Error> {
) -> Result<(RawFd, PathBuf), Error> {
let path = path.as_ref();
// Note: we use mkstemp heŕe, because this worka with different
@ -140,8 +138,6 @@ pub fn replace_file<P: AsRef<Path>>(
Err(err) => bail!("mkstemp {:?} failed: {}", template, err),
};
let tmp_path = tmp_path.as_path();
// clippy bug?: from_bits_truncate is actually a const fn...
#[allow(clippy::or_fun_call)]
let mode: stat::Mode = options
@ -149,27 +145,40 @@ pub fn replace_file<P: AsRef<Path>>(
.unwrap_or(stat::Mode::from_bits_truncate(0o644));
if let Err(err) = stat::fchmod(fd, mode) {
let _ = unistd::unlink(tmp_path);
let _ = unistd::unlink(&tmp_path);
bail!("fchmod {:?} failed: {}", tmp_path, err);
}
if options.owner.is_some() || options.group.is_some() {
if let Err(err) = fchown(fd, options.owner, options.group) {
let _ = unistd::unlink(tmp_path);
let _ = unistd::unlink(&tmp_path);
bail!("fchown {:?} failed: {}", tmp_path, err);
}
}
Ok((fd, tmp_path))
}
/// Atomically replace a file.
///
/// This first creates a temporary file and then rotates it in place.
pub fn replace_file<P: AsRef<Path>>(
path: P,
data: &[u8],
options: CreateOptions,
) -> Result<(), Error> {
let (fd, tmp_path) = make_tmp_file(&path, options)?;
let mut file = unsafe { File::from_raw_fd(fd) };
if let Err(err) = file.write_all(data) {
let _ = unistd::unlink(tmp_path);
let _ = unistd::unlink(&tmp_path);
bail!("write failed: {}", err);
}
if let Err(err) = std::fs::rename(tmp_path, path) {
let _ = unistd::unlink(tmp_path);
bail!("Atomic rename failed for file {:?} - {}", path, err);
if let Err(err) = std::fs::rename(&tmp_path, &path) {
let _ = unistd::unlink(&tmp_path);
bail!("Atomic rename failed for file {:?} - {}", path.as_ref(), err);
}
Ok(())