get_or_split_cmdline_devs() now scans for component devices

Fix accidental splitbrain issues caused by writing to only some of a
filesystem's devices: now, all subcommands that take member devices will
scan for all members before opening.

Fixes: https://github.com/koverstreet/bcachefs/issues/924
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

2 files changed, 30 insertions, 0 deletions

diff --git a/src/device_scan.rs b/src/device_scan.rs
index 4bed2d13..fda2d460 100644
--- a/src/device_scan.rs
+++ b/src/device_scan.rs
@@ -1,4 +1,5 @@
 use std::{
+    ffi::{CStr, CString, c_char},
     collections::HashMap,
     env,
     path::{Path, PathBuf},
@@ -171,3 +172,26 @@ pub fn joined_device_str(sbs: &Vec<(PathBuf, bch_sb_handle)>) -> String {
         .collect::<Vec<_>>()
         .join(":")
 }
+
+pub fn scan_devices(device: &String, opts: &bch_opts) -> Result<String> {
+    let mut sbs = scan_sbs(device, opts)?;
+
+    for sb in &mut sbs {
+        unsafe {
+            bch_bindgen::sb_io::bch2_free_super(&mut sb.1);
+        }
+    }
+
+    Ok(joined_device_str(&sbs))
+}
+
+#[no_mangle]
+pub extern "C" fn bch2_scan_devices(device: *const c_char) -> *mut c_char {
+    let device = unsafe { CStr::from_ptr(device) };
+    let device = device.to_str().unwrap().to_string();
+
+    let opts = bch_bindgen::opts::parse_mount_opts(None, None, true)
+        .unwrap_or_default();
+
+    CString::new(scan_devices(&device, &opts).unwrap()).unwrap().into_raw()
+}
diff --git a/src/rust_to_c.h b/src/rust_to_c.h
new file mode 100644
index 00000000..4f23e1dd
--- /dev/null
+++ b/src/rust_to_c.h
@@ -0,0 +1,6 @@
+#ifndef _BCACHEFS_TOOLS_RUST_TO_C_H
+#define _BCACHEFS_TOOLS_RUST_TO_C_H
+
+char *bch2_scan_devices(char *);
+
+#endif /* _BCACHEFS_TOOLS_RUST_TO_C_H */