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src/tools.rs: implement file_set_contents_full()

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This commit is contained in:
Dietmar Maurer
2019-04-06 13:53:43 +02:00
parent 0f778e0652
commit eea8131952
3 changed files with 273 additions and 3 deletions
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44
src/tools.rs
View File

@ -149,13 +149,25 @@ pub fn file_get_json<P: AsRef<Path>>(path: P, default: Option<Value>) -> Result<
}).map_err(|err: Error| format_err!("unable to parse json from {:?} - {}", path, err))
}
/// Atomically write a file. We first create a temporary file, which
/// is then renamed.
/// Atomically write a file
///
/// We first create a temporary file, which is then renamed.
pub fn file_set_contents<P: AsRef<Path>>(
path: P,
data: &[u8],
perm: Option<stat::Mode>,
) -> Result<(), Error> {
file_set_contents_full(path, data, perm, None, None)
}
/// Atomically write a file with owner and group
pub fn file_set_contents_full<P: AsRef<Path>>(
path: P,
data: &[u8],
perm: Option<stat::Mode>,
owner: Option<nix::unistd::Uid>,
group: Option<nix::unistd::Gid>,
) -> Result<(), Error> {
let path = path.as_ref();
@ -180,6 +192,13 @@ pub fn file_set_contents<P: AsRef<Path>>(
bail!("fchmod {:?} failed: {}", tmp_path, err);
}
if owner != None || group != None {
if let Err(err) = fchown(fd, owner, group) {
let _ = unistd::unlink(tmp_path);
bail!("fchown {:?} failed: {}", tmp_path, err);
}
}
use std::os::unix::io::FromRawFd;
let mut file = unsafe { File::from_raw_fd(fd) };
@ -320,7 +339,7 @@ pub fn file_chunker<C, R>(
Ok(())
}
// Returns the Unix uid/gid for the sepcified system user.
/// Returns the Unix uid/gid for the sepcified system user.
pub fn getpwnam_ugid(username: &str) -> Result<(libc::uid_t,libc::gid_t), Error> {
let info = unsafe { libc::getpwnam(std::ffi::CString::new(username).unwrap().as_ptr()) };
if info == std::ptr::null_mut() {
@ -332,6 +351,25 @@ pub fn getpwnam_ugid(username: &str) -> Result<(libc::uid_t,libc::gid_t), Error>
Ok((info.pw_uid, info.pw_gid))
}
/// Change ownership of an open file handle
pub fn fchown(
fd: RawFd,
owner: Option<nix::unistd::Uid>,
group: Option<nix::unistd::Gid>
) -> Result<(), Error> {
// According to the POSIX specification, -1 is used to indicate that owner and group
// are not to be changed. Since uid_t and gid_t are unsigned types, we have to wrap
// around to get -1 (copied fron nix crate).
let uid = owner.map(Into::into).unwrap_or((0 as libc::uid_t).wrapping_sub(1));
let gid = group.map(Into::into).unwrap_or((0 as libc::gid_t).wrapping_sub(1));
let res = unsafe { libc::fchown(fd, uid, gid) };
nix::errno::Errno::result(res)?;
Ok(())
}
// Returns the hosts node name (UTS node name)
pub fn nodename() -> &'static str {

185
src/tools/process_locker.rs~ Normal file
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@ -0,0 +1,185 @@
use failure::*;
use std::thread;
use std::sync::{Arc, Mutex};
use std::os::unix::io::AsRawFd;
//use proxmox_backup::tools;
// fixme: use F_OFD_ locks when implemented with nix::fcntl
// flock lock conversion is not atomic, so we need to use fcntl
struct ProcessLocker {
file: std::fs::File,
exclusive: bool,
writers: usize,
}
struct SharedLock {
locker: Arc<Mutex<ProcessLocker>>,
}
impl Drop for SharedLock {
fn drop(&mut self) {
let tid = std::thread::current().id();
let pid = std::process::id();
println!("{:?}:{:?}: Drop Writerlock", pid, tid);
let mut data = self.locker.lock().unwrap();
if data.writers == 0 { panic!("unexpected ProcessLocker state"); }
if data.writers == 1 && !data.exclusive {
let op = libc::flock {
l_type: libc::F_UNLCK as i16,
l_whence: libc::SEEK_SET as i16,
l_start: 0,
l_len: 0,
l_pid: 0,
};
if let Err(err) = nix::fcntl::fcntl(data.file.as_raw_fd(), nix::fcntl::FcntlArg::F_SETLKW(&op)) {
panic!("unable to drop writer lock - {}", err);
}
data.writers = 0;
}
}
}
struct ExclusiveLock {
locker: Arc<Mutex<ProcessLocker>>,
}
impl Drop for ExclusiveLock {
fn drop(&mut self) {
let tid = std::thread::current().id();
let pid = std::process::id();
println!("{:?}:{:?}: Drop Exclusive lock", pid, tid);
let mut data = self.locker.lock().unwrap();
if !data.exclusive { panic!("unexpected ProcessLocker state"); }
let ltype = if data.writers != 0 { libc::F_RDLCK } else { libc::F_UNLCK };
let op = libc::flock {
l_type: ltype as i16,
l_whence: libc::SEEK_SET as i16,
l_start: 0,
l_len: 0,
l_pid: 0,
};
if let Err(err) = nix::fcntl::fcntl(data.file.as_raw_fd(), nix::fcntl::FcntlArg::F_SETLKW(&op)) {
panic!("unable to drop exclusive lock - {}", err);
}
data.exclusive = false;
}
}
impl ProcessLocker {
pub fn new(lockfile: &str) -> Result<Arc<Mutex<Self>>, Error> {
let file = std::fs::OpenOptions::new()
.create(true)
.read(true)
.write(true)
.open(lockfile)?;
Ok(Arc::new(Mutex::new(Self {
file: file,
exclusive: false,
writers: 0,
})))
}
pub fn try_shared_lock(locker: Arc<Mutex<Self>>) -> Result<SharedLock, Error> {
let mut data = locker.lock().unwrap();
if data.writers == 0 && !data.exclusive {
let op = libc::flock {
l_type: libc::F_RDLCK as i16,
l_whence: libc::SEEK_SET as i16,
l_start: 0,
l_len: 0,
l_pid: 0,
};
if let Err(err) = nix::fcntl::fcntl(data.file.as_raw_fd(), nix::fcntl::FcntlArg::F_SETLK(&op)) {
bail!("unable to get shared lock - {}", err);
}
}
data.writers += 1;
Ok(SharedLock { locker: locker.clone() })
}
pub fn try_exclusive_lock(locker: Arc<Mutex<Self>>) -> Result<ExclusiveLock, Error> {
let mut data = locker.lock().unwrap();
if data.exclusive {
bail!("already locked exclusively");
}
let op = libc::flock {
l_type: libc::F_WRLCK as i16,
l_whence: libc::SEEK_SET as i16,
l_start: 0,
l_len: 0,
l_pid: 0,
};
if let Err(err) = nix::fcntl::fcntl(data.file.as_raw_fd(), nix::fcntl::FcntlArg::F_SETLK(&op)) {
bail!("unable to get exclusive lock - {}", err);
}
data.exclusive = true;
return Ok(ExclusiveLock { locker: locker.clone() });
}
}
fn run_test() -> Result<(), Error>
{
let tid = std::thread::current().id();
let pid = std::process::id();
let locker = ProcessLocker::new("test.flock")?;
println!("{:?}:{:?}: try to get shared lock", pid, tid);
let l1 = ProcessLocker::try_shared_lock(locker.clone())?;
println!("{:?}:{:?}: got shared lock", pid, tid);
println!("{:?}:{:?}: try to get exclusive lock", pid, tid);
let l2 = ProcessLocker::try_exclusive_lock(locker.clone())?;
println!("{:?}:{:?}: got exclusive lock", pid, tid);
println!("{:?}:{:?}: try to get shared lock", pid, tid);
let l3 = ProcessLocker::try_shared_lock(locker.clone())?;
println!("{:?}:{:?}: got shared lock", pid, tid);
Ok(())
}
fn main() -> Result<(), Error>
{
if let Err(err) = run_test() {
println!("ERROR: {}", err);
}
let tid = std::thread::current().id();
let pid = std::process::id();
println!("{:?}:{:?}: Exit", pid, tid);
Ok(())
}

47
src/tools/procfs.rs~ Normal file
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@ -0,0 +1,47 @@
use failure::*;
use crate::tools;
use lazy_static::lazy_static;
use regex::Regex;
pub struct ProcFsPidStat {
pub status: u8,
pub utime: u64,
pub stime: u64,
pub starttime: u64,
pub vsize: u64,
pub rss: i64,
}
pub fn read_proc_pid_stat(pid: nix::unistd::Pid) -> Result<ProcFsPidStat, Error> {
let statstr = tools::file_read_firstline(format!("/proc/{}/stat", pid))?;
lazy_static! {
static ref REGEX: Regex = Regex::new(r"^(?P<pid>\d+) \(?:.*\) (?P<status>\S) -?\d+ -?\d+ -?\d+ -?\d+ -?\d+ \d+ \d+ \d+ \d+ \d+ (?P<utime>\d+) (?P<stime>\d+) -?\d+ -?\d+ -?\d+ -?\d+ -?\d+ 0 (?P<starttime>\d+) (?P<vsize>\d+) (?P<rss>-?\d+) \d+ \d+ \d+ \d+ \d+ \d+ \d+ \d+ \d+ \d+ \d+ \d+ \d+ -?\d+ -?\d+ \d+ \d+ \d+").unwrap();
}
if let Some(cap) = REGEX.captures(&statstr) {
if pid != nix::unistd::Pid::from_raw(cap["pid"].parse::<i32>().unwrap()) {
bail!("unable to read pid stat for process '{}' - got wrong pid", pid);
}
return Ok(ProcFsPidStat {
status: cap["status"].parse::<u8>().unwrap(),
utime: cap["utime"].parse::<u64>().unwrap(),
stime: cap["stime"].parse::<u64>().unwrap(),
starttime: cap["starttime"].parse::<u64>().unwrap(),
vsize: cap["vsize"].parse::<u64>().unwrap(),
rss: cap["rss"].parse::<i64>().unwrap() * 4096,
});
}
bail!("unable to read pid stat for process '{}'", pid);
}
pub fn read_proc_starttime(pid: nix::unistd::Pid) -> Result<u64, Error> {
let info = read_proc_pid_stat(pid)?;
Ok(info.starttime)
}