From fe69dd9a4035ac8b9972edc44d9c859877f45b83 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Arpad=20M=C3=BCller?= <arpad@neon.tech>
Date: Thu, 31 Aug 2023 12:34:50 +0200
Subject: [PATCH] Add write_and_fsync function

---
 pageserver/src/virtual_file.rs | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/pageserver/src/virtual_file.rs b/pageserver/src/virtual_file.rs
index 65d769e8e7..5f3f7a5fef 100644
--- a/pageserver/src/virtual_file.rs
+++ b/pageserver/src/virtual_file.rs
@@ -389,6 +389,20 @@ impl VirtualFile {
         Ok(())
     }
 
+    /// Write the given buffer (which has to be below the kernel's internal page size) and fsync
+    ///
+    /// This ensures some level of atomicity (not a good one, but it's the best we have).
+    pub async fn write_and_fsync(&mut self, buf: &[u8]) -> Result<(), Error> {
+        if self.write(buf)? != buf.len() {
+            return Err(Error::new(
+                std::io::ErrorKind::Other,
+                "Could not write all the bytes in a single call",
+            ));
+        }
+        self.sync_all()?;
+        Ok(())
+    }
+
     pub fn read_at(&self, buf: &mut [u8], offset: u64) -> Result<usize, Error> {
         let result = self.with_file("read", |file| file.read_at(buf, offset))?;
         if let Ok(size) = result {