Merge 'Rename IO backends to support Linux platforms without io_uring…

…' from Jorge López Tello

As was suggested in #502 I have renamed the IO backends from `darwin` to
`unix` and from `linux` to `io_uring`. The `unix` backend is now
available to Linux platforms without io_uring.

On the topic of letting platforms disable io_uring support, the primary
example is Google, which posted this
[blog](https://security.googleblog.com/2023/06/learnings-from-kctf-
vrps-42-linux.html) in 2023 about disabling io_uring by default in most
of their servers/platforms, including Android (prime candidate user for
a SQLite rewrite).

Closes #628

core/Cargo.toml

@@ -14,19 +14,20 @@ name = "limbo_core"
 path = "lib.rs"
 
 [features]
-default = ["fs", "json", "uuid"]
+default = ["fs", "json", "uuid", "io_uring"]
 fs = []
 json = [
     "dep:jsonb",
     "dep:pest",
     "dep:pest_derive",
 ]
 uuid = ["dep:uuid"]
+io_uring = ["dep:io-uring"]
 
 [target.'cfg(target_os = "linux")'.dependencies]
-io-uring = "0.6.1"
+io-uring = { version = "0.6.1", optional = true }
 
-[target.'cfg(target_os = "macos")'.dependencies]
+[target.'cfg(target_family = "unix")'.dependencies]
 polling = "3.7.2"
 rustix = "0.38.34"
 

core/error.rs

@@ -19,12 +19,12 @@ pub enum LimboError {
     EnvVarError(#[from] std::env::VarError),
     #[error("I/O error: {0}")]
     IOError(#[from] std::io::Error),
-    #[cfg(target_os = "linux")]
+    #[cfg(all(target_os = "linux", feature = "io_uring"))]
     #[error("I/O error: {0}")]
-    LinuxIOError(String),
+    UringIOError(String),
     #[error("Locking error: {0}")]
     LockingError(String),
-    #[cfg(target_os = "macos")]
+    #[cfg(target_family = "unix")]
     #[error("I/O error: {0}")]
     RustixIOError(#[from] rustix::io::Errno),
     #[error("Parse error: {0}")]

core/io/linux.rs → core/io/io_uring.rs

@@ -14,15 +14,15 @@ const MAX_IOVECS: usize = 128;
 const SQPOLL_IDLE: u32 = 1000;
 
 #[derive(Debug, Error)]
-enum LinuxIOError {
+enum UringIOError {
     IOUringCQError(i32),
 }
 
 // Implement the Display trait to customize error messages
-impl fmt::Display for LinuxIOError {
+impl fmt::Display for UringIOError {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
-            LinuxIOError::IOUringCQError(code) => write!(
+            UringIOError::IOUringCQError(code) => write!(
                 f,
                 "IOUring completion queue error occurred with code {}",
                 code
@@ -31,8 +31,8 @@ impl fmt::Display for LinuxIOError {
     }
 }
 
-pub struct LinuxIO {
-    inner: Rc<RefCell<InnerLinuxIO>>,
+pub struct UringIO {
+    inner: Rc<RefCell<InnerUringIO>>,
 }
 
 struct WrappedIOUring {
@@ -42,13 +42,13 @@ struct WrappedIOUring {
     key: u64,
 }
 
-struct InnerLinuxIO {
+struct InnerUringIO {
     ring: WrappedIOUring,
     iovecs: [iovec; MAX_IOVECS],
     next_iovec: usize,
 }
 
-impl LinuxIO {
+impl UringIO {
     pub fn new() -> Result<Self> {
         let ring = match io_uring::IoUring::builder()
             .setup_sqpoll(SQPOLL_IDLE)
@@ -57,7 +57,7 @@ impl LinuxIO {
             Ok(ring) => ring,
             Err(_) => io_uring::IoUring::new(MAX_IOVECS as u32)?,
         };
-        let inner = InnerLinuxIO {
+        let inner = InnerUringIO {
             ring: WrappedIOUring {
                 ring,
                 pending_ops: 0,
@@ -76,7 +76,7 @@ impl LinuxIO {
     }
 }
 
-impl InnerLinuxIO {
+impl InnerUringIO {
     pub fn get_iovec(&mut self, buf: *const u8, len: usize) -> &iovec {
         let iovec = &mut self.iovecs[self.next_iovec];
         iovec.iov_base = buf as *mut std::ffi::c_void;
@@ -125,7 +125,7 @@ impl WrappedIOUring {
     }
 }
 
-impl IO for LinuxIO {
+impl IO for UringIO {
     fn open_file(&self, path: &str, flags: OpenFlags, direct: bool) -> Result<Rc<dyn File>> {
         trace!("open_file(path = {})", path);
         let file = std::fs::File::options()
@@ -142,14 +142,14 @@ impl IO for LinuxIO {
                 Err(error) => debug!("Error {error:?} returned when setting O_DIRECT flag to read file. The performance of the system may be affected"),
             };
         }
-        let linux_file = Rc::new(LinuxFile {
+        let uring_file = Rc::new(UringFile {
             io: self.inner.clone(),
             file,
         });
         if std::env::var(common::ENV_DISABLE_FILE_LOCK).is_err() {
-            linux_file.lock_file(true)?;
+            uring_file.lock_file(true)?;
         }
-        Ok(linux_file)
+        Ok(uring_file)
     }
 
     fn run_once(&self) -> Result<()> {
@@ -165,9 +165,9 @@ impl IO for LinuxIO {
         while let Some(cqe) = ring.get_completion() {
             let result = cqe.result();
             if result < 0 {
-                return Err(LimboError::LinuxIOError(format!(
+                return Err(LimboError::UringIOError(format!(
                     "{} cqe: {:?}",
-                    LinuxIOError::IOUringCQError(result),
+                    UringIOError::IOUringCQError(result),
                     cqe
                 )));
             }
@@ -191,12 +191,12 @@ impl IO for LinuxIO {
     }
 }
 
-pub struct LinuxFile {
-    io: Rc<RefCell<InnerLinuxIO>>,
+pub struct UringFile {
+    io: Rc<RefCell<InnerUringIO>>,
     file: std::fs::File,
 }
 
-impl File for LinuxFile {
+impl File for UringFile {
     fn lock_file(&self, exclusive: bool) -> Result<()> {
         let fd = self.file.as_raw_fd();
         let flock = flock {
@@ -306,7 +306,7 @@ impl File for LinuxFile {
     }
 }
 
-impl Drop for LinuxFile {
+impl Drop for UringFile {
     fn drop(&mut self) {
         self.unlock_file().expect("Failed to unlock file");
     }
@@ -319,6 +319,6 @@ mod tests {
 
     #[test]
     fn test_multiple_processes_cannot_open_file() {
-        common::tests::test_multiple_processes_cannot_open_file(LinuxIO::new);
+        common::tests::test_multiple_processes_cannot_open_file(UringIO::new);
     }
 }

core/io/mod.rs

@@ -164,14 +164,14 @@ impl Buffer {
 }
 
 cfg_block! {
-    #[cfg(target_os = "linux")] {
-        mod linux;
-        pub use linux::LinuxIO as PlatformIO;
+    #[cfg(all(target_os = "linux", feature = "io_uring"))] {
+        mod io_uring;
+        pub use io_uring::UringIO as PlatformIO;
     }
 
-    #[cfg(target_os = "macos")] {
-        mod darwin;
-        pub use darwin::DarwinIO as PlatformIO;
+    #[cfg(any(all(target_os = "linux",not(feature = "io_uring")), target_os = "macos"))] {
+        mod unix;
+        pub use unix::UnixIO as PlatformIO;
     }
 
     #[cfg(target_os = "windows")] {

core/io/darwin.rs → core/io/unix.rs

@@ -14,13 +14,13 @@ use std::collections::HashMap;
 use std::io::{Read, Seek, Write};
 use std::rc::Rc;
 
-pub struct DarwinIO {
+pub struct UnixIO {
     poller: Rc<RefCell<Poller>>,
     events: Rc<RefCell<Events>>,
     callbacks: Rc<RefCell<HashMap<usize, CompletionCallback>>>,
 }
 
-impl DarwinIO {
+impl UnixIO {
     pub fn new() -> Result<Self> {
         Ok(Self {
             poller: Rc::new(RefCell::new(Poller::new()?)),
@@ -30,7 +30,7 @@ impl DarwinIO {
     }
 }
 
-impl IO for DarwinIO {
+impl IO for UnixIO {
     fn open_file(&self, path: &str, flags: OpenFlags, _direct: bool) -> Result<Rc<dyn File>> {
         trace!("open_file(path = {})", path);
         let file = std::fs::File::options()
@@ -40,15 +40,15 @@ impl IO for DarwinIO {
             .create(matches!(flags, OpenFlags::Create))
             .open(path)?;
 
-        let darwin_file = Rc::new(DarwinFile {
+        let unix_file = Rc::new(UnixFile {
             file: Rc::new(RefCell::new(file)),
             poller: self.poller.clone(),
             callbacks: self.callbacks.clone(),
         });
         if std::env::var(common::ENV_DISABLE_FILE_LOCK).is_err() {
-            darwin_file.lock_file(true)?;
+            unix_file.lock_file(true)?;
         }
-        Ok(darwin_file)
+        Ok(unix_file)
     }
 
     fn run_once(&self) -> Result<()> {
@@ -127,13 +127,13 @@ enum CompletionCallback {
     ),
 }
 
-pub struct DarwinFile {
+pub struct UnixFile {
     file: Rc<RefCell<std::fs::File>>,
     poller: Rc<RefCell<polling::Poller>>,
     callbacks: Rc<RefCell<HashMap<usize, CompletionCallback>>>,
 }
 
-impl File for DarwinFile {
+impl File for UnixFile {
     fn lock_file(&self, exclusive: bool) -> Result<()> {
         let fd = self.file.borrow().as_raw_fd();
         let flock = flock {
@@ -279,7 +279,7 @@ impl File for DarwinFile {
     }
 }
 
-impl Drop for DarwinFile {
+impl Drop for UnixFile {
     fn drop(&mut self) {
         self.unlock_file().expect("Failed to unlock file");
     }
@@ -291,6 +291,6 @@ mod tests {
 
     #[test]
     fn test_multiple_processes_cannot_open_file() {
-        common::tests::test_multiple_processes_cannot_open_file(DarwinIO::new);
+        common::tests::test_multiple_processes_cannot_open_file(UnixIO::new);
     }
 }