require target_os=linux for direct io path

Signed-off-by: Yuchen Liang <yuchen@neon.tech>

libs/pageserver_api/src/models.rs

@@ -974,16 +974,28 @@ pub mod virtual_file {
         serde_with::DeserializeFromStr,
         serde_with::SerializeDisplay,
         Debug,
-        Default,
     )]
     #[strum(serialize_all = "kebab-case")]
     pub enum IoModeKind {
         /// Uses buffered IO.
-        #[default]
         Buffered,
         /// Uses direct IO, error out if the operation fails.
+        #[cfg(target_os = "linux")]
         Direct,
     }
+
+    impl IoModeKind {
+        // TODO(yuchen): change to [`Self::Direct`] once finish rollout.
+        #[cfg(target_os = "linux")]
+        pub const fn preferred() -> Self {
+            Self::Buffered
+        }
+
+        #[cfg(target_os = "macos")]
+        pub const fn preferred() -> Self {
+            Self::Buffered
+        }
+    }
 }
 
 #[derive(Debug, Clone, Serialize, Deserialize)]

pageserver/ctl/src/layer_map_analyzer.rs

@@ -137,7 +137,7 @@ pub(crate) async fn main(cmd: &AnalyzeLayerMapCmd) -> Result<()> {
     pageserver::virtual_file::init(
         10,
         virtual_file::api::IoEngineKind::StdFs,
-        IoModeKind::default(),
+        IoModeKind::preferred(),
     );
     pageserver::page_cache::init(100);
 

pageserver/ctl/src/layers.rs

@@ -50,7 +50,7 @@ async fn read_delta_file(path: impl AsRef<Path>, ctx: &RequestContext) -> Result
     virtual_file::init(
         10,
         virtual_file::api::IoEngineKind::StdFs,
-        IoModeKind::default(),
+        IoModeKind::preferred(),
     );
     page_cache::init(100);
     let path = Utf8Path::from_path(path.as_ref()).expect("non-Unicode path");
@@ -64,7 +64,7 @@ async fn read_image_file(path: impl AsRef<Path>, ctx: &RequestContext) -> Result
     virtual_file::init(
         10,
         virtual_file::api::IoEngineKind::StdFs,
-        IoModeKind::default(),
+        IoModeKind::preferred(),
     );
     page_cache::init(100);
     let path = Utf8Path::from_path(path.as_ref()).expect("non-Unicode path");
@@ -170,7 +170,7 @@ pub(crate) async fn main(cmd: &LayerCmd) -> Result<()> {
             pageserver::virtual_file::init(
                 10,
                 virtual_file::api::IoEngineKind::StdFs,
-                IoModeKind::default(),
+                IoModeKind::preferred(),
             );
             pageserver::page_cache::init(100);
 

pageserver/ctl/src/main.rs

@@ -208,7 +208,7 @@ async fn print_layerfile(path: &Utf8Path) -> anyhow::Result<()> {
     virtual_file::init(
         10,
         virtual_file::api::IoEngineKind::StdFs,
-        IoModeKind::default(),
+        IoModeKind::preferred(),
     );
     page_cache::init(100);
     let ctx = RequestContext::new(TaskKind::DebugTool, DownloadBehavior::Error);

pageserver/src/config.rs

@@ -416,7 +416,7 @@ impl PageServerConf {
                 .map(crate::l0_flush::L0FlushConfig::from)
                 .unwrap_or_default(),
             virtual_file_io_mode: virtual_file_io_mode
-                .unwrap_or(virtual_file::IoModeKind::default()),
+                .unwrap_or(virtual_file::IoModeKind::preferred()),
             no_sync: no_sync.unwrap_or(false),
         };
 

pageserver/src/virtual_file.rs

@@ -146,6 +146,7 @@ impl VirtualFile {
                     _mode: IoMode::Buffered,
                 }
             }
+            #[cfg(target_os = "linux")]
             IoMode::Direct => {
                 let inner = VirtualFileInner::open_with_options(
                     path,
@@ -1375,6 +1376,7 @@ pub(crate) type IoPageSlice<'a> =
 pub(crate) enum IoMode {
     NotSet,
     Buffered,
+    #[cfg(target_os = "linux")]
     Direct,
 }
 
@@ -1385,6 +1387,7 @@ impl TryFrom<u8> for IoMode {
         Ok(match value {
             v if v == (IoMode::NotSet as u8) => IoMode::NotSet,
             v if v == (IoMode::Buffered as u8) => IoMode::Buffered,
+            #[cfg(target_os = "linux")]
             v if v == (IoMode::Direct as u8) => IoMode::Direct,
             x => return Err(x),
         })
@@ -1395,6 +1398,7 @@ impl From<IoModeKind> for IoMode {
     fn from(value: IoModeKind) -> Self {
         match value {
             IoModeKind::Buffered => IoMode::Buffered,
+            #[cfg(target_os = "linux")]
             IoModeKind::Direct => IoMode::Direct,
         }
     }
@@ -1420,7 +1424,7 @@ fn get_io_mode() -> IoMode {
                             panic!("invalid VirtualFile io mode for env var {env_var_name}: {e:#}: {v:?}")
                         }
                     },
-                    Err(std::env::VarError::NotPresent) => IoModeKind::Direct,
+                    Err(std::env::VarError::NotPresent) => IoModeKind::preferred(),
                     Err(std::env::VarError::NotUnicode(_)) => {
                         panic!("env var {env_var_name} is not unicode");
                     }