efi: add syncfs() and drop() before unmounting ESP

Fix error:
```
umount: /boot/efi: target is busy.

error: unmount after validate: Failed to unmount "/boot/efi":
Child ["umount" "/boot/efi"] exited: exit status: 32
```

Author: HuijingHei

src/efi.rs

@@ -10,6 +10,7 @@ use std::path::{Path, PathBuf};
 use std::process::Command;
 
 use anyhow::{bail, Context, Result};
+use bootc_utils::CommandRunExt;
 use cap_std::fs::Dir;
 use cap_std_ext::cap_std;
 use fn_error_context::context;
@@ -22,7 +23,7 @@ use widestring::U16CString;
 use crate::bootupd::RootContext;
 use crate::model::*;
 use crate::ostreeutil;
-use crate::util::{self, CommandRunExt};
+use crate::util;
 use crate::{blockdev, filetree};
 use crate::{component::*, packagesystem};
 
@@ -266,14 +267,18 @@ impl Component for Efi {
         for esp in esp_devices {
             let destpath = &self.ensure_mounted_esp(rootcxt.path.as_ref(), Path::new(&esp))?;
 
-            let esp = openat::Dir::open(&destpath.join("EFI")).context("opening EFI dir")?;
-            validate_esp_fstype(&esp)?;
+            let efidir = openat::Dir::open(&destpath.join("EFI")).context("opening EFI dir")?;
+            validate_esp_fstype(&efidir)?;
 
             // For adoption, we should only touch files that we know about.
-            let diff = updatef.relative_diff_to(&esp)?;
+            let diff = updatef.relative_diff_to(&efidir)?;
             log::trace!("applying adoption diff: {}", &diff);
-            filetree::apply_diff(&updated, &esp, &diff, None)
+            filetree::apply_diff(&updated, &efidir, &diff, None)
                 .context("applying filesystem changes")?;
+
+            // Do the sync before unmount
+            efidir.syncfs()?;
+            drop(efidir);
             self.unmount().context("unmount after adopt")?;
         }
         Ok(Some(InstalledContent {
@@ -356,6 +361,10 @@ impl Component for Efi {
             log::trace!("applying diff: {}", &diff);
             filetree::apply_diff(&updated, &destdir, &diff, None)
                 .context("applying filesystem changes")?;
+
+            // Do the sync before unmount
+            destdir.syncfs()?;
+            drop(destdir);
             self.unmount().context("unmount after update")?;
         }
 
@@ -422,7 +431,7 @@ impl Component for Efi {
         for esp in esp_devices.iter() {
             let destpath = &self.ensure_mounted_esp(Path::new("/"), Path::new(&esp))?;
 
-            let efidir = &openat::Dir::open(&destpath.join("EFI"))
+            let efidir = openat::Dir::open(&destpath.join("EFI"))
                 .with_context(|| format!("opening EFI dir {}", destpath.display()))?;
             let diff = currentf.relative_diff_to(&efidir)?;
 
@@ -433,6 +442,7 @@ impl Component for Efi {
                 errs.push(format!("Removed: {}", f));
             }
             assert_eq!(diff.additions.len(), 0);
+            drop(efidir);
             self.unmount().context("unmount after validate")?;
         }
 

src/util.rs

@@ -5,6 +5,7 @@ use std::process::Command;
 use anyhow::{bail, Context, Result};
 use openat_ext::OpenatDirExt;
 
+#[allow(dead_code)]
 pub(crate) trait CommandRunExt {
     fn run(&mut self) -> Result<()>;
 }