Move save_metadata function.

`timeline.rs` seems like a better home for it.

pageserver/src/layered_repository.rs

@@ -69,7 +69,7 @@ pub use timeline::Timeline;
 pub use crate::layered_repository::ephemeral_file::writeback as writeback_ephemeral_file;
 
 // re-export for use in storage_sync.rs
-pub use crate::layered_repository::timeline::save_metadata;
+pub use crate::layered_repository::metadata::save_metadata;
 
 // re-export for use in walreceiver
 pub use crate::layered_repository::timeline::WalReceiverInfo;
@@ -185,7 +185,7 @@ impl Repository {
         crashsafe_dir::create_dir_all(timeline_path)?;
 
         let metadata = TimelineMetadata::new(Lsn(0), None, None, Lsn(0), initdb_lsn, initdb_lsn);
-        timeline::save_metadata(self.conf, timeline_id, self.tenant_id, &metadata, true)?;
+        save_metadata(self.conf, timeline_id, self.tenant_id, &metadata, true)?;
 
         let timeline = Timeline::new(
             self.conf,
@@ -294,7 +294,7 @@ impl Repository {
             src_timeline.initdb_lsn,
         );
         crashsafe_dir::create_dir_all(self.conf.timeline_path(&dst, &self.tenant_id))?;
-        timeline::save_metadata(self.conf, dst, self.tenant_id, &metadata, true)?;
+        save_metadata(self.conf, dst, self.tenant_id, &metadata, true)?;
         timelines.insert(dst, LayeredTimelineEntry::Unloaded { id: dst, metadata });
 
         info!("branched timeline {} from {} at {}", dst, src, start_lsn);

pageserver/src/layered_repository/metadata.rs

@@ -6,10 +6,13 @@
 //!
 //! The module contains all structs and related helper methods related to timeline metadata.
 
+use std::fs::{File, OpenOptions};
+use std::io::Write;
 use std::path::PathBuf;
 
-use anyhow::ensure;
+use anyhow::{bail, ensure, Context};
 use serde::{Deserialize, Serialize};
+use tracing::info_span;
 use utils::{
     bin_ser::BeSer,
     lsn::Lsn,
@@ -17,6 +20,7 @@ use utils::{
 };
 
 use crate::config::PageServerConf;
+use crate::virtual_file::VirtualFile;
 use crate::STORAGE_FORMAT_VERSION;
 
 /// We assume that a write of up to METADATA_MAX_SIZE bytes is atomic.
@@ -65,17 +69,6 @@ struct TimelineMetadataBody {
     initdb_lsn: Lsn,
 }
 
-/// Points to a place in pageserver's local directory,
-/// where certain timeline's metadata file should be located.
-pub fn metadata_path(
-    conf: &'static PageServerConf,
-    timelineid: ZTimelineId,
-    tenantid: ZTenantId,
-) -> PathBuf {
-    conf.timeline_path(&timelineid, &tenantid)
-        .join(METADATA_FILE_NAME)
-}
-
 impl TimelineMetadata {
     pub fn new(
         disk_consistent_lsn: Lsn,
@@ -173,6 +166,53 @@ impl TimelineMetadata {
     }
 }
 
+/// Points to a place in pageserver's local directory,
+/// where certain timeline's metadata file should be located.
+pub fn metadata_path(
+    conf: &'static PageServerConf,
+    timelineid: ZTimelineId,
+    tenantid: ZTenantId,
+) -> PathBuf {
+    conf.timeline_path(&timelineid, &tenantid)
+        .join(METADATA_FILE_NAME)
+}
+
+/// Save timeline metadata to file
+pub fn save_metadata(
+    conf: &'static PageServerConf,
+    timelineid: ZTimelineId,
+    tenantid: ZTenantId,
+    data: &TimelineMetadata,
+    first_save: bool,
+) -> anyhow::Result<()> {
+    let _enter = info_span!("saving metadata").entered();
+    let path = metadata_path(conf, timelineid, tenantid);
+    // use OpenOptions to ensure file presence is consistent with first_save
+    let mut file = VirtualFile::open_with_options(
+        &path,
+        OpenOptions::new().write(true).create_new(first_save),
+    )?;
+
+    let metadata_bytes = data.to_bytes().context("Failed to get metadata bytes")?;
+
+    if file.write(&metadata_bytes)? != metadata_bytes.len() {
+        bail!("Could not write all the metadata bytes in a single call");
+    }
+    file.sync_all()?;
+
+    // fsync the parent directory to ensure the directory entry is durable
+    if first_save {
+        let timeline_dir = File::open(
+            &path
+                .parent()
+                .expect("Metadata should always have a parent dir"),
+        )?;
+        timeline_dir.sync_all()?;
+    }
+
+    Ok(())
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;

pageserver/src/layered_repository/timeline.rs

@@ -11,8 +11,6 @@ use tracing::*;
 use std::cmp::{max, min, Ordering};
 use std::collections::{HashMap, HashSet};
 use std::fs;
-use std::fs::{File, OpenOptions};
-use std::io::Write;
 use std::ops::{Deref, Range};
 use std::path::PathBuf;
 use std::sync::atomic::{self, AtomicBool, AtomicI64, Ordering as AtomicOrdering};
@@ -32,7 +30,7 @@ use crate::layered_repository::{
     image_layer::{ImageLayer, ImageLayerWriter},
     inmemory_layer::InMemoryLayer,
     layer_map::{LayerMap, SearchResult},
-    metadata::{metadata_path, TimelineMetadata, METADATA_FILE_NAME},
+    metadata::{save_metadata, TimelineMetadata, METADATA_FILE_NAME},
     par_fsync,
     storage_layer::{Layer, ValueReconstructResult, ValueReconstructState},
 };
@@ -54,7 +52,6 @@ use utils::{
 use crate::repository::{GcResult, RepositoryTimeline};
 use crate::repository::{Key, Value};
 use crate::thread_mgr;
-use crate::virtual_file::VirtualFile;
 use crate::walreceiver::IS_WAL_RECEIVER;
 use crate::walredo::WalRedoManager;
 use crate::CheckpointConfig;
@@ -2342,39 +2339,3 @@ fn rename_to_backup(path: PathBuf) -> anyhow::Result<()> {
 
     bail!("couldn't find an unused backup number for {:?}", path)
 }
-
-/// Save timeline metadata to file
-pub fn save_metadata(
-    conf: &'static PageServerConf,
-    timelineid: ZTimelineId,
-    tenantid: ZTenantId,
-    data: &TimelineMetadata,
-    first_save: bool,
-) -> Result<()> {
-    let _enter = info_span!("saving metadata").entered();
-    let path = metadata_path(conf, timelineid, tenantid);
-    // use OpenOptions to ensure file presence is consistent with first_save
-    let mut file = VirtualFile::open_with_options(
-        &path,
-        OpenOptions::new().write(true).create_new(first_save),
-    )?;
-
-    let metadata_bytes = data.to_bytes().context("Failed to get metadata bytes")?;
-
-    if file.write(&metadata_bytes)? != metadata_bytes.len() {
-        bail!("Could not write all the metadata bytes in a single call");
-    }
-    file.sync_all()?;
-
-    // fsync the parent directory to ensure the directory entry is durable
-    if first_save {
-        let timeline_dir = File::open(
-            &path
-                .parent()
-                .expect("Metadata should always have a parent dir"),
-        )?;
-        timeline_dir.sync_all()?;
-    }
-
-    Ok(())
-}