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>

5 files changed, 45 insertions, 21 deletions

diff --git a/rust-src/src/cmd_completions.rs b/rust-src/src/cmd_completions.rs
index 51859696..3e839fe8 100644
--- a/rust-src/src/cmd_completions.rs
+++ b/rust-src/src/cmd_completions.rs
@@ -1,7 +1,6 @@
-use crate::transform_c_args;
 use clap::{Command, CommandFactory, Parser};
 use clap_complete::{generate, Generator, Shell};
-use std::ffi::{c_char, c_int};
+use std::ffi::{c_int, OsStr};
 use std::io;
 
 /// Generate shell completions
@@ -14,10 +13,7 @@ fn print_completions<G: Generator>(gen: G, cmd: &mut Command) {
     generate(gen, cmd, cmd.get_name().to_string(), &mut io::stdout());
 }
 
-#[no_mangle]
-#[allow(clippy::not_unsafe_ptr_arg_deref)]
-pub extern "C" fn cmd_completions(argc: c_int, argv: *const *const c_char) -> c_int {
-    transform_c_args!(argv, argc, argv);
+pub fn cmd_completions(argv: Vec<&OsStr>) -> c_int {
     let cli = Cli::parse_from(argv);
     print_completions(cli.shell, &mut super::Cli::command());
     0
diff --git a/rust-src/src/cmd_list.rs b/rust-src/src/cmd_list.rs
index 5540514e..fa9c2f2f 100644
--- a/rust-src/src/cmd_list.rs
+++ b/rust-src/src/cmd_list.rs
@@ -9,8 +9,7 @@ use bch_bindgen::btree::BtreeIter;
 use bch_bindgen::btree::BtreeNodeIter;
 use bch_bindgen::btree::BtreeIterFlags;
 use clap::{Parser};
-use std::ffi::{c_int, c_char};
-use crate::transform_c_args;
+use std::ffi::{c_int, OsStr};
 
 fn list_keys(fs: &Fs, opt: Cli) -> anyhow::Result<()> {
     let trans = BtreeTrans::new(fs);
@@ -158,13 +157,13 @@ fn cmd_list_inner(opt: Cli) -> anyhow::Result<()> {
     }
 }
 
-#[no_mangle]
-#[allow(clippy::not_unsafe_ptr_arg_deref)]
-pub extern "C" fn cmd_list(argc: c_int, argv: *const *const c_char) {
-    transform_c_args!(argv, argc, argv);
+pub fn cmd_list(argv: Vec<&OsStr>) -> c_int {
     let opt = Cli::parse_from(argv);
     colored::control::set_override(opt.colorize);
     if let Err(e) = cmd_list_inner(opt) {
         error!("Fatal error: {}", e);
+        1
+    } else {
+        0
     }
 }
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
+        }
+    }
+}
diff --git a/rust-src/src/cmd_mount.rs b/rust-src/src/cmd_mount.rs
index a75dd21f..3f8253f5 100644
--- a/rust-src/src/cmd_mount.rs
+++ b/rust-src/src/cmd_mount.rs
@@ -4,10 +4,9 @@ use log::{info, debug, error, LevelFilter};
 use clap::{Parser};
 use uuid::Uuid;
 use std::path::PathBuf;
-use crate::{key, transform_c_args};
+use crate::key;
 use crate::key::KeyLocation;
-use crate::logger::SimpleLogger;
-use std::ffi::{CString, c_int, c_char, c_void};
+use std::ffi::{CString, c_int, c_char, c_void, OsStr};
 use std::os::unix::ffi::OsStrExt;
 
 fn mount_inner(
@@ -222,14 +221,9 @@ fn cmd_mount_inner(opt: Cli) -> anyhow::Result<()> {
     Ok(())
 }
 
-#[no_mangle]
-#[allow(clippy::not_unsafe_ptr_arg_deref)]
-pub extern "C" fn cmd_mount(argc: c_int, argv: *const *const c_char) -> c_int {
-    transform_c_args!(argv, argc, argv);
+pub fn cmd_mount(argv: Vec<&OsStr>) -> c_int {
     let opt = Cli::parse_from(argv);
 
-    log::set_boxed_logger(Box::new(SimpleLogger)).unwrap();
-
     // @TODO : more granular log levels via mount option
     log::set_max_level(match opt.verbose {
         0 => LevelFilter::Warn,
diff --git a/rust-src/src/lib.rs b/rust-src/src/lib.rs
index 64297b41..026cca49 100644
--- a/rust-src/src/lib.rs
+++ b/rust-src/src/lib.rs
@@ -2,6 +2,7 @@ use clap::Subcommand;
 
 pub mod key;
 pub mod logger;
+pub mod cmd_main;
 pub mod cmd_mount;
 pub mod cmd_list;
 pub mod cmd_completions;