create common entry point for Rust commands

The bcachefs sub-commands that are implemented in Rust (completions,
list, and mount) had separate entrypoints and thus had some differences
in behavior.

This introduces a common entry point for the Rust sub-commands. This
reduces duplicate boilerplate code like parsing argv and setting up
logging, and will facilitate converting more sub-commands to Rust in
the future.

An immediate benefit is that this fixes an issue with `bcachefs list`
not reporting errors:

before:

$ bcachefs list /dev/typo
$ echo $?
0

after:

$ bcachefs list /dev/typo
ERROR - bcachefs_rust::cmd_list: Fatal error: "No such file or directory"
$ echo $?
1

Signed-off-by: Thomas Bertschinger <tahbertschinger@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

1 files changed, 34 insertions, 0 deletions

diff --git a/rust-src/src/cmd_main.rs b/rust-src/src/cmd_main.rs
new file mode 100644
index 00000000..baedc851
--- /dev/null
+++ b/rust-src/src/cmd_main.rs
@@ -0,0 +1,34 @@
+use log::{error, LevelFilter};
+use std::ffi::{CStr, c_int, c_char};
+use crate::transform_c_args;
+use crate::logger::SimpleLogger;
+use crate::cmd_completions::cmd_completions;
+use crate::cmd_list::cmd_list;
+use crate::cmd_mount::cmd_mount;
+
+#[no_mangle]
+pub extern "C" fn rust_main(argc: c_int, argv: *const *const c_char, cmd: *const c_char) -> c_int {
+    transform_c_args!(argv, argc, argv);
+
+    log::set_boxed_logger(Box::new(SimpleLogger)).unwrap();
+    log::set_max_level(LevelFilter::Warn);
+
+    let cmd: &CStr = unsafe { CStr::from_ptr(cmd) };
+    let cmd = match cmd.to_str() {
+        Ok(c) => c,
+        Err(e) => {
+            error!("could not parse command: {}", e);
+            return 1;
+        }
+    };
+
+    match cmd {
+        "completions" => cmd_completions(argv),
+        "list" => cmd_list(argv),
+        "mount" => cmd_mount(argv),
+        _ => {
+            error!("unknown command: {}", cmd);
+            1
+        }
+    }
+}