fix(tvix/castore/blobservice): update bytes_read only on successful read

We previously updated this.pos also in case the underlying read returned
an error.

Also, use the ready! macro to remove the match block, and instrument
errors returned during start_seek.

Change-Id: Ic32e26579d964a76b45687134acc48d72d67c36f
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11421
Reviewed-by: Brian Olsen <me@griff.name>
Reviewed-by: Connor Brewster <cbrewster@hey.com>
Tested-by: BuildkiteCI
Autosubmit: flokli <flokli@flokli.de>

tvix/castore/src/blobservice/chunked_reader.rs

@@ -1,12 +1,12 @@
-use futures::TryStreamExt;
+use futures::{ready, TryStreamExt};
 use pin_project_lite::pin_project;
 use tokio::io::{AsyncRead, AsyncSeekExt};
 use tokio_stream::StreamExt;
 use tokio_util::io::{ReaderStream, StreamReader};
-use tracing::warn;
+use tracing::{instrument, warn};
 
 use crate::B3Digest;
-use std::{cmp::Ordering, pin::Pin, task::Poll};
+use std::{cmp::Ordering, pin::Pin};
 
 use super::{BlobReader, BlobService};
 
@@ -60,15 +60,12 @@ where
         let filled_before = buf.filled().len();
 
         let this = self.project();
-        match this.r.poll_read(cx, buf) {
-            Poll::Ready(a) => {
-                let bytes_read = buf.filled().len() - filled_before;
-                *this.pos += bytes_read as u64;
 
-                Poll::Ready(a)
-            }
-            Poll::Pending => Poll::Pending,
-        }
+        ready!(this.r.poll_read(cx, buf))?;
+        let bytes_read = buf.filled().len() - filled_before;
+        *this.pos += bytes_read as u64;
+
+        Ok(()).into()
     }
 }
 
@@ -76,6 +73,7 @@ impl<BS> tokio::io::AsyncSeek for ChunkedReader<BS>
 where
     BS: AsRef<dyn BlobService> + Clone + Send + 'static,
 {
+    #[instrument(skip(self), err(Debug))]
     fn start_seek(self: Pin<&mut Self>, position: std::io::SeekFrom) -> std::io::Result<()> {
         let total_len = self.chunked_blob.blob_length();
         let current_pos = self.pos;

tvix/castore/src/blobservice/naive_seeker.rs

@@ -1,4 +1,5 @@
 use super::BlobReader;
+use futures::ready;
 use pin_project_lite::pin_project;
 use std::io;
 use std::task::Poll;
@@ -83,18 +84,13 @@ impl<R: tokio::io::AsyncRead> tokio::io::AsyncRead for NaiveSeeker<R> {
         // The amount of data read can be determined by the increase
         // in the length of the slice returned by `ReadBuf::filled`.
         let filled_before = buf.filled().len();
+
         let this = self.project();
-        let pos: &mut u64 = this.pos;
+        ready!(this.r.poll_read(cx, buf))?;
+        let bytes_read = buf.filled().len() - filled_before;
+        *this.pos += bytes_read as u64;
 
-        match this.r.poll_read(cx, buf) {
-            Poll::Ready(a) => {
-                let bytes_read = buf.filled().len() - filled_before;
-                *pos += bytes_read as u64;
-
-                Poll::Ready(a)
-            }
-            Poll::Pending => Poll::Pending,
-        }
+        Ok(()).into()
     }
 }
 
@@ -115,7 +111,7 @@ impl<R: tokio::io::AsyncRead> tokio::io::AsyncBufRead for NaiveSeeker<R> {
 }
 
 impl<R: tokio::io::AsyncRead> tokio::io::AsyncSeek for NaiveSeeker<R> {
-    #[instrument(skip(self))]
+    #[instrument(skip(self), err(Debug))]
     fn start_seek(
         self: std::pin::Pin<&mut Self>,
         position: std::io::SeekFrom,