[Slackbuilds-users] virtiofsd is ready for slk15

[Duncan Roe]

Hi Matteo,

I built virtiofsd 1.13.0 from your repo and it worked fine except it couldn't
mount the root filesystem (/). This is corrected by commit 8e8a375 which I
expect will be in the next release. In the meantime, I ported the fix back to
1.13.0 and it's attached.

How did you build the vendor tarball? If I knew that, I'd be happy to take on
maintainance of virtiofsd for the main repo.

(This email is a re-send with patch as plain text: the .gz didn't make it onto
the list).

Cheers ... Duncan.
-------------- next part --------------
--- /usr/src/virtiofsd/src/sandbox.rs	2025-11-10 14:33:05.981323884 +1100
+++ virtiofsd/src/sandbox.rs	2025-11-10 14:55:54.354217008 +1100
@@ -55,6 +55,10 @@
     OpenNewRoot(io::Error),
     /// Failed to open old root.
     OpenOldRoot(io::Error),
+    /// Failed to stat new root.
+    StatNewRoot(io::Error),
+    /// Failed to stat old root.
+    StatOldRoot(io::Error),
     /// Failed to open `/proc/self`.
     OpenProcSelf(io::Error),
     /// Failed to open `/proc/self/fd`.
@@ -268,30 +272,40 @@
         // Change to new root directory to prepare for `pivot_root` syscall.
         oslib::fchdir(newroot_fd).map_err(Error::ChdirNewRoot)?;
 
-        // Call to `pivot_root` using `.` as both new and old root.
-        let c_current_dir = CString::new(".").unwrap();
-        let ret = unsafe {
-            libc::syscall(
-                libc::SYS_pivot_root,
-                c_current_dir.as_ptr(),
-                c_current_dir.as_ptr(),
-            )
-        };
-        if ret < 0 {
-            return Err(Error::PivotRoot(std::io::Error::last_os_error()));
-        }
+        // Check if we are supposed to switch to our current rootfs
+        let old_st = crate::passthrough::stat::statx(&oldroot_fd, None).map_err(Error::StatOldRoot)?;
+        let new_st = crate::passthrough::stat::statx(&newroot_fd, None).map_err(Error::StatNewRoot)?;
+        let switch_to_current_rootfs = (old_st.mnt_id == new_st.mnt_id)
+            && (old_st.st.st_dev == new_st.st.st_dev)
+            && (old_st.st.st_ino == new_st.st.st_ino);
+
+        if !switch_to_current_rootfs {
+            // Call to `pivot_root` using `.` as both new and old root.
+            let c_current_dir = CString::new(".").unwrap();
+            let ret = unsafe {
+                libc::syscall(
+                    libc::SYS_pivot_root,
+                    c_current_dir.as_ptr(),
+                    c_current_dir.as_ptr(),
+                )
+            };
+            if ret < 0 {
+                return Err(Error::PivotRoot(std::io::Error::last_os_error()));
+            }
 
-        // Change to old root directory to prepare for cleaning up and unmounting it.
-        oslib::fchdir(oldroot_fd).map_err(Error::ChdirOldRoot)?;
+            // Change to old root directory to prepare for cleaning up and unmounting it.
+            oslib::fchdir(oldroot_fd).map_err(Error::ChdirOldRoot)?;
 
-        // Clean up old root to avoid mount namespace propagation.
-        oslib::mount(None, ".", None, libc::MS_SLAVE | libc::MS_REC).map_err(Error::CleanMount)?;
+            // Clean up old root to avoid mount namespace propagation.
+            oslib::mount(None, ".", None, libc::MS_SLAVE | libc::MS_REC)
+                .map_err(Error::CleanMount)?;
 
-        // Lazily unmount old root.
-        oslib::umount2(".", libc::MNT_DETACH).map_err(Error::UmountOldRoot)?;
+            // Lazily unmount old root.
+            oslib::umount2(".", libc::MNT_DETACH).map_err(Error::UmountOldRoot)?;
 
-        // Change to new root.
-        oslib::fchdir(newroot_fd).map_err(Error::ChdirNewRoot)?;
+            // Change to new root.
+            oslib::fchdir(newroot_fd).map_err(Error::ChdirNewRoot)?;
+        }
 
         // We no longer need these file descriptors, so close them.
         unsafe { libc::close(newroot_fd) };