From 521da324abc6fb110ec59704595d2e6a969f9812 Mon Sep 17 00:00:00 2001
From: Christian Schwarz <christian@neon.tech>
Date: Tue, 20 Aug 2024 10:07:07 +0000
Subject: [PATCH] Revert "try a closure approach, also has same error "Send is
 not general enough""

This reverts commit ef2b384cf8be44f7433baae633031dfb039a971b.
---
 .../tenant/storage_layer/inmemory_layer.rs    | 14 +++++++++-
 .../inmemory_layer/vectored_dio_read.rs       | 26 +++++++++++++------
 2 files changed, 31 insertions(+), 9 deletions(-)

diff --git a/pageserver/src/tenant/storage_layer/inmemory_layer.rs b/pageserver/src/tenant/storage_layer/inmemory_layer.rs
index 2fdedc4230..288d96a0d8 100644
--- a/pageserver/src/tenant/storage_layer/inmemory_layer.rs
+++ b/pageserver/src/tenant/storage_layer/inmemory_layer.rs
@@ -319,10 +319,11 @@ impl InMemoryLayer {
 
         // Execute the read.
         vectored_dio_read::execute(
-            |_, _| async move { todo!() },
+            &inner.file,
             reads
                 .iter()
                 .flat_map(|(_, value_reads)| value_reads.iter().map(|v| &v.read)),
+            &ctx,
         )
         .await;
 
@@ -359,6 +360,17 @@ impl InMemoryLayer {
     }
 }
 
+impl vectored_dio_read::File for EphemeralFile {
+    async fn read_at_to_end<'a, 'b, B: tokio_epoll_uring::IoBufMut + Send>(
+        &'b self,
+        start: u32,
+        dst: tokio_epoll_uring::Slice<B>,
+        ctx: &'a RequestContext,
+    ) -> std::io::Result<(tokio_epoll_uring::Slice<B>, usize)> {
+        EphemeralFile::read_at_to_end(self, start, dst, ctx).await
+    }
+}
+
 fn inmem_layer_display(mut f: impl Write, start_lsn: Lsn, end_lsn: Lsn) -> std::fmt::Result {
     write!(f, "inmem-{:016X}-{:016X}", start_lsn.0, end_lsn.0)
 }
diff --git a/pageserver/src/tenant/storage_layer/inmemory_layer/vectored_dio_read.rs b/pageserver/src/tenant/storage_layer/inmemory_layer/vectored_dio_read.rs
index cfff2b4097..7ffa46460d 100644
--- a/pageserver/src/tenant/storage_layer/inmemory_layer/vectored_dio_read.rs
+++ b/pageserver/src/tenant/storage_layer/inmemory_layer/vectored_dio_read.rs
@@ -8,6 +8,15 @@ use tokio_epoll_uring::{BoundedBuf, IoBufMut, Slice};
 
 use crate::context::RequestContext;
 
+pub trait File {
+    async fn read_at_to_end<'a, 'b, B: IoBufMut + Send>(
+        &'b self,
+        start: u32,
+        dst: Slice<B>,
+        ctx: &'a RequestContext,
+    ) -> std::io::Result<(Slice<B>, usize)>;
+}
+
 trait Sealed {}
 
 pub trait Buffer: Sealed + std::ops::Deref<Target = [u8]> {
@@ -71,11 +80,10 @@ impl Buffer for Vec<u8> {
     }
 }
 
-pub async fn execute<'a, 'b, I, F, Fut, B>(file: F, reads: I)
+pub async fn execute<'a, 'b, 'c, I, F, B>(file: &'c F, reads: I, ctx: &'b RequestContext)
 where
     I: IntoIterator<Item = &'a ValueRead<B>> + Send,
-    F: Fn(u32, Slice<Vec<u8>>) -> Fut + Send,
-    Fut: std::future::Future<Output = Result<(Slice<Vec<u8>>, usize), Arc<std::io::Error>>> + Send,
+    F: File + Send,
     B: Buffer + IoBufMut + Send,
 {
     const DIO_CHUNK_SIZE: usize = 512;
@@ -198,11 +206,13 @@ where
         if all_done {
             continue;
         }
-        let (merged_read_buf_slice, nread) = match file(
-            start_chunk_no * DIO_CHUNK_SIZE as u32,
-            get_chunk_buf(nchunks).slice_full(),
-        )
-        .await
+        let (merged_read_buf_slice, nread) = match file
+            .read_at_to_end(
+                start_chunk_no * DIO_CHUNK_SIZE as u32,
+                get_chunk_buf(nchunks).slice_full(),
+                ctx,
+            )
+            .await
         {
             Ok(t) => t,
             Err(e) => {