install: Fork blockdev --rereadpt instead of internal ioctl

The `ioctl` to reread the partition table was the last thing
pulling in `nix`. Honestly especially in the install path
I have no problem forking external binaries, and since we're
already depending on util-linux-core for other things like
`sfdisk` and `lsblk`, it just makes sense to so here with
the command whose entire role in life is to just issue
that `ioctl`.

This drops out an older verison of `nix` (which is a fine crate, but again
I think `rustix` is nicer). There's a different version
pulled in via libsystemd, but we can get to that later.

Signed-off-by: Colin Walters <[email protected]>

lib/Cargo.toml

@@ -29,8 +29,6 @@ libc = { workspace = true }
 liboverdrop = "0.1.0"
 libsystemd = "0.7"
 openssl = "^0.10.64"
-# TODO drop this in favor of rustix
-nix = { version = "0.29", features = ["ioctl", "sched" ] }
 regex = "1.10.4"
 rustix = { "version" = "0.38.34", features = ["thread", "fs", "system", "process"] }
 schemars = { version = "0.8.17", features = ["chrono"] }

lib/src/blockdev.rs

@@ -1,15 +1,12 @@
 use std::collections::HashMap;
 use std::env;
-use std::fs::File;
-use std::os::unix::io::AsRawFd;
 use std::path::Path;
 use std::process::Command;
 use std::sync::OnceLock;
 
 use anyhow::{anyhow, Context, Result};
 use camino::{Utf8Path, Utf8PathBuf};
 use fn_error_context::context;
-use nix::errno::Errno;
 use regex::Regex;
 use serde::Deserialize;
 
@@ -270,30 +267,6 @@ pub(crate) fn udev_settle() -> Result<()> {
     Ok(())
 }
 
-#[allow(unsafe_code)]
-pub(crate) fn reread_partition_table(file: &mut File, retry: bool) -> Result<()> {
-    let fd = file.as_raw_fd();
-    // Reread sometimes fails inexplicably.  Retry several times before
-    // giving up.
-    let max_tries = if retry { 20 } else { 1 };
-    for retries in (0..max_tries).rev() {
-        let result = unsafe { ioctl::blkrrpart(fd) };
-        match result {
-            Ok(_) => break,
-            Err(err) if retries == 0 && err == Errno::EINVAL => {
-                return Err(err)
-                    .context("couldn't reread partition table: device may not support partitions")
-            }
-            Err(err) if retries == 0 && err == Errno::EBUSY => {
-                return Err(err).context("couldn't reread partition table: device is in use")
-            }
-            Err(err) if retries == 0 => return Err(err).context("couldn't reread partition table"),
-            Err(_) => std::thread::sleep(std::time::Duration::from_millis(100)),
-        }
-    }
-    Ok(())
-}
-
 /// Parse key-value pairs from lsblk --pairs.
 /// Newer versions of lsblk support JSON but the one in CentOS 7 doesn't.
 fn split_lsblk_line(line: &str) -> HashMap<String, String> {
@@ -340,16 +313,6 @@ pub(crate) fn find_parent_devices(device: &str) -> Result<Vec<String>> {
     Ok(parents)
 }
 
-// create unsafe ioctl wrappers
-#[allow(clippy::missing_safety_doc)]
-mod ioctl {
-    use libc::c_int;
-    use nix::{ioctl_none, ioctl_read, ioctl_read_bad, libc, request_code_none};
-    ioctl_none!(blkrrpart, 0x12, 95);
-    ioctl_read_bad!(blksszget, request_code_none!(0x12, 104), c_int);
-    ioctl_read!(blkgetsize64, 0x12, 114, libc::size_t);
-}
-
 /// Parse a string into mibibytes
 pub(crate) fn parse_size_mib(mut s: &str) -> Result<u64> {
     let suffixes = [

lib/src/install/baseline.rs

@@ -315,14 +315,10 @@ pub(crate) fn install_create_rootfs(
     tracing::debug!("Created partition table");
 
     // Reread the partition table
-    {
-        let mut f = std::fs::OpenOptions::new()
-            .write(true)
-            .open(&devpath)
-            .with_context(|| format!("opening {devpath}"))?;
-        crate::blockdev::reread_partition_table(&mut f, true)
-            .context("Rereading partition table")?;
-    }
+    Task::new("Reread partition table", "blockdev")
+        .arg("--rereadpt")
+        .arg(devpath.as_str())
+        .run()?;
 
     // Full udev sync; it'd obviously be better to await just the devices
     // we're targeting, but this is a simple coarse hammer.