refactor(ecstore): add mmap copy disk read name (#4061)

crates/ecstore/docs/internode-transport/internode-transport-adapter-rfc.md

@@ -171,7 +171,7 @@ Classification:
 | Remote shard read stream | `crates/ecstore/src/rpc/remote_disk.rs::RemoteDisk::read_file_stream`; `crates/ecstore/src/rpc/internode_data_transport.rs::InternodeDataTransport::open_read`; `crates/ecstore/src/bitrot.rs::create_bitrot_reader` | `rustfs/src/storage/rpc/http_service.rs::handle_read_file` | Covered by `InternodeDataTransport` | Object GET, repair reads, and erasure decode use this path for remote shard bytes. |
 | Remote shard write stream | `RemoteDisk::create_file`; `RemoteDisk::append_file`; `InternodeDataTransport::open_write`; `crates/ecstore/src/bitrot.rs::create_bitrot_writer` | `rustfs/src/storage/rpc/http_service.rs::handle_put_file` | Covered by `InternodeDataTransport` | Object PUT and multipart part upload use this path for remote shard bytes. |
 | Remote namespace walk stream | `RemoteDisk::walk_dir`; `InternodeDataTransport::open_walk_dir`; `crates/ecstore/src/cache_value/metacache_set.rs` walk producers | `rustfs/src/storage/rpc/http_service.rs::handle_walk_dir` | Covered by `InternodeDataTransport` | High-volume listing/scanner/heal metadata stream. It is not object byte data, but it is a large internode stream. |
-| Remote zero-copy read fallback | `RemoteDisk::read_file_zero_copy` | same as remote shard read stream | Covered by `InternodeDataTransport` through `read_file_stream` | The remote path buffers the stream into `Bytes`; true zero-copy is not guaranteed for remote disks. |
+| Remote mmap-copy read fallback | `RemoteDisk::read_file_mmap_copy` | same as remote shard read stream | Covered by `InternodeDataTransport` through `read_file_stream` | The remote path buffers the stream into `Bytes`; true zero-copy is not guaranteed for remote disks. |
 
 ### Still Direct TCP/HTTP/gRPC
 
@@ -210,7 +210,7 @@ Classification:
 | Medium | `ReadAll` and `WriteAll` still carry unary `bytes` over gRPC. They appear metadata-oriented today, but there is no size threshold or routing policy. |
 | Medium | `ReadMultiple` can aggregate many metadata files into one gRPC response. |
 | Low | Legacy gRPC `WalkDir` remains implemented while `RemoteDisk::walk_dir` uses HTTP through the transport. |
-| Medium | Remote `read_file_zero_copy` is a buffered read over the transport, not a remote zero-copy contract. |
+| Medium | Remote `read_file_mmap_copy` is a buffered read over the transport, not a remote zero-copy contract. |
 | Medium | Server-side TCP HTTP route handling is outside the client-side trait. |
 
 ## Current Object Write Path
@@ -235,7 +235,7 @@ This is the primary write data-plane candidate.
 For object GETs and repair reads in distributed erasure mode, the relevant flow is:
 
 1. `SetDisks` prepares shard readers for the selected disks.
-2. `create_bitrot_reader` uses local zero-copy only when `disk.is_local()`.
+2. `create_bitrot_reader` uses local mmap-copy reads only when `disk.is_local()`.
 3. For a remote disk, it calls `disk.read_file_stream(...)`.
 4. `RemoteDisk::read_file_stream` delegates to
    `InternodeDataTransport::open_read`.
@@ -385,7 +385,7 @@ The initial TCP backend can keep the current signed HTTP URLs internally.
 `RemoteDisk` delegates only these methods to the data transport:
 
 - `read_file_stream`
-- `read_file_zero_copy` as the current wrapper over `read_file_stream`
+- `read_file_mmap_copy` as the current wrapper over `read_file_stream`
 - `append_file`
 - `create_file`
 - `walk_dir`

crates/ecstore/docs/internode-transport/transport-buffer-lifecycle.md

@@ -54,7 +54,7 @@ through `ParallelReader` in `crates/ecstore/src/erasure_coding/decode.rs` and
 | Bitrot verification | `BitrotReader::read` | caller `&mut [u8]`, `hash_buf: Vec<u8>` | No additional payload copy | The bitrot reader reads hash bytes into `hash_buf` and payload bytes directly into the supplied output slice. Hash calculation reads the slice. |
 | Erasure shard read | `ParallelReader::read` | `Vec<u8>` per shard | Yes | Each shard read allocates `vec![0u8; shard_size]`; data is filled there before decode/reconstruction. |
 | Object response write | `write_data_blocks` | slices of shard `Vec<u8>` | No extra staging copy | Decoded data block slices are written to the target writer with `write_all`; the target may copy internally. |
-| Remote zero-copy helper | `RemoteDisk::read_file_zero_copy` | `Vec<u8>` then `Bytes` | Yes | The remote implementation reads the full stream into a `Vec` and converts it into `Bytes`. It is a convenience fallback, not network zero-copy. |
+| Remote mmap-copy helper | `RemoteDisk::read_file_mmap_copy` | `Vec<u8>` then `Bytes` | Yes | The remote implementation reads the full stream into a `Vec` and converts it into `Bytes`. It is a convenience fallback, not network zero-copy. |
 
 ## Write Stream
 
@@ -90,7 +90,7 @@ through `ParallelReader` in `crates/ecstore/src/erasure_coding/decode.rs` and
 | 3 | `ParallelReader::read` shard buffers | High on read path | Each shard read allocates and fills a `Vec<u8>` before decode can proceed. This is also where degraded reads wait on quorum. |
 | 4 | `ReaderStream::with_capacity` plus `StreamReader` | Medium on read path | Server file reads create `Bytes` chunks, then client `AsyncRead` copies those chunks into the caller's `ReadBuf`. |
 | 5 | `Erasure::encode` block and shard materialization | Medium on write path | Source data is first read into a block `Vec<u8>`, then encoded into per-shard `Bytes`. This is necessary for the current erasure API. |
-| 6 | `RemoteDisk::read_file_zero_copy` | Medium when used | Remote zero-copy reads buffer the whole stream into memory. The name does not mean zero-copy over the network. |
+| 6 | `RemoteDisk::read_file_mmap_copy` | Medium when used | Remote mmap-copy reads buffer the whole stream into memory. The name does not mean zero-copy over the network. |
 | 7 | URL/query/header/JSON serialization | Low | Metadata copies are small and not on the large payload hot path. |
 
 ## Adapter Ownership Gaps
@@ -117,6 +117,6 @@ through `ParallelReader` in `crates/ecstore/src/erasure_coding/decode.rs` and
 7. The HTTP auth and URL construction boundary is part of the current TCP/HTTP
    backend. A non-HTTP backend would need equivalent peer authentication and
    disk addressing without assuming URL query parameters.
-8. Local disk zero-copy exists only for local reads via `read_file_zero_copy`.
+8. Local disk mmap-copy reads exist only for local reads via `read_file_mmap_copy`.
    Remote disks deliberately fall back to network streaming and full-buffer
-   collection for the zero-copy helper.
+   collection for the legacy zero-copy helper.

crates/ecstore/src/cluster/rpc/remote_disk.rs

@@ -1708,11 +1708,10 @@ impl DiskAPI for RemoteDisk {
             .await
     }
 
-    /// Zero-copy read for remote disks falls back to efficient network read.
-    /// Note: True zero-copy is not possible over network, but we avoid extra copies
-    /// by reading directly into Bytes.
+    /// Buffered read for remote disks.
+    /// The transport stream is collected into owned Bytes for caller sharing.
     #[tracing::instrument(level = "debug", skip(self))]
-    async fn read_file_zero_copy(&self, volume: &str, path: &str, offset: usize, length: usize) -> Result<Bytes> {
+    async fn read_file_mmap_copy(&self, volume: &str, path: &str, offset: usize, length: usize) -> Result<Bytes> {
         // For remote disks, use the regular reader and read into Bytes
         let reader = self.read_file_stream(volume, path, offset, length).await?;
 

crates/ecstore/src/disk/disk_store.rs

@@ -1361,9 +1361,9 @@ impl DiskAPI for LocalDiskWrapper {
         .await
     }
 
-    async fn read_file_zero_copy(&self, volume: &str, path: &str, offset: usize, length: usize) -> Result<bytes::Bytes> {
+    async fn read_file_mmap_copy(&self, volume: &str, path: &str, offset: usize, length: usize) -> Result<bytes::Bytes> {
         self.track_disk_health(
-            || async { self.disk.read_file_zero_copy(volume, path, offset, length).await },
+            || async { self.disk.read_file_mmap_copy(volume, path, offset, length).await },
             get_max_timeout_duration(),
         )
         .await

crates/ecstore/src/disk/local.rs

@@ -2750,13 +2750,12 @@ impl DiskAPI for LocalDisk {
         Ok(Box::new(StallTimeoutReader::new(reader, get_object_disk_read_timeout())))
     }
 
-    /// Zero-copy file read using memory mapping (Unix) or efficient read (non-Unix).
-    /// Returns Bytes that can be shared without copying.
+    /// File read using mmap-then-copy on Unix or efficient read on non-Unix.
     // SAFETY: Unix unsafe calls in this function only query page size and mmap
     // a read-only file region after bounds and alignment are validated.
     #[allow(unsafe_code)]
     #[tracing::instrument(level = "debug", skip(self))]
-    async fn read_file_zero_copy(&self, volume: &str, path: &str, offset: usize, length: usize) -> Result<Bytes> {
+    async fn read_file_mmap_copy(&self, volume: &str, path: &str, offset: usize, length: usize) -> Result<Bytes> {
         let volume_dir = self.get_bucket_path(volume)?;
         if !skip_access_checks(volume) {
             access(&volume_dir)
@@ -2784,7 +2783,7 @@ impl DiskAPI for LocalDisk {
                 offset,
                 length,
                 actual_size = meta.len(),
-                reason = "read_file_zero_copy_out_of_bounds",
+                reason = "read_file_mmap_copy_out_of_bounds",
                 "Disk local read fallback failed"
             );
             return Err(DiskError::FileCorrupt);
@@ -4871,7 +4870,26 @@ mod test {
     }
 
     #[tokio::test]
-    async fn test_read_file_zero_copy_rejects_offset_length_overflow() {
+    async fn test_read_file_mmap_copy_rejects_offset_length_overflow() {
+        use tempfile::tempdir;
+
+        let dir = tempdir().expect("operation should succeed");
+        let endpoint =
+            Endpoint::try_from(dir.path().to_str().expect("operation should succeed")).expect("operation should succeed");
+        let disk = LocalDisk::new(&endpoint, false).await.expect("operation should succeed");
+
+        disk.make_volume("test-volume").await.expect("operation should succeed");
+        disk.write_all("test-volume", "test-file.txt", Bytes::from_static(b"test"))
+            .await
+            .expect("operation should succeed");
+
+        let result = disk.read_file_mmap_copy("test-volume", "test-file.txt", usize::MAX, 1).await;
+        assert!(matches!(result, Err(DiskError::FileCorrupt)));
+    }
+
+    #[tokio::test]
+    #[allow(deprecated)]
+    async fn test_read_file_zero_copy_legacy_alias_rejects_offset_length_overflow() {
         use tempfile::tempdir;
 
         let dir = tempdir().expect("operation should succeed");

crates/ecstore/src/disk/mod.rs

@@ -291,10 +291,10 @@ impl DiskAPI for Disk {
     }
 
     #[tracing::instrument(skip(self))]
-    async fn read_file_zero_copy(&self, volume: &str, path: &str, offset: usize, length: usize) -> Result<Bytes> {
+    async fn read_file_mmap_copy(&self, volume: &str, path: &str, offset: usize, length: usize) -> Result<Bytes> {
         match self {
-            Disk::Local(local_disk) => local_disk.read_file_zero_copy(volume, path, offset, length).await,
-            Disk::Remote(remote_disk) => remote_disk.read_file_zero_copy(volume, path, offset, length).await,
+            Disk::Local(local_disk) => local_disk.read_file_mmap_copy(volume, path, offset, length).await,
+            Disk::Remote(remote_disk) => remote_disk.read_file_mmap_copy(volume, path, offset, length).await,
         }
     }
 
@@ -558,11 +558,17 @@ pub trait DiskAPI: Debug + Send + Sync + 'static {
     async fn read_file(&self, volume: &str, path: &str) -> Result<FileReader>;
     async fn read_file_stream(&self, volume: &str, path: &str, offset: usize, length: usize) -> Result<FileReader>;
 
-    /// Zero-copy file read using memory mapping (Unix) or efficient read (non-Unix).
-    /// Returns Bytes that can be shared without copying.
-    /// On Unix, this uses mmap for true zero-copy access.
-    /// On other platforms, falls back to efficient read operations.
-    async fn read_file_zero_copy(&self, volume: &str, path: &str, offset: usize, length: usize) -> Result<Bytes>;
+    /// File read using mmap-then-copy on Unix or an efficient read on non-Unix.
+    async fn read_file_mmap_copy(&self, volume: &str, path: &str, offset: usize, length: usize) -> Result<Bytes>;
+
+    /// Historical name for `read_file_mmap_copy`.
+    #[deprecated(
+        since = "1.0.0-beta.8",
+        note = "use read_file_mmap_copy; this path copies mmap data into owned Bytes"
+    )]
+    async fn read_file_zero_copy(&self, volume: &str, path: &str, offset: usize, length: usize) -> Result<Bytes> {
+        self.read_file_mmap_copy(volume, path, offset, length).await
+    }
 
     async fn append_file(&self, volume: &str, path: &str) -> Result<FileWriter>;
     async fn create_file(&self, origvolume: &str, volume: &str, path: &str, file_size: i64) -> Result<FileWriter>;

crates/ecstore/src/io_support/bitrot.rs

@@ -149,7 +149,7 @@ async fn open_disk_reader(
 ) -> disk::error::Result<FileReader> {
     if use_mmap_read && disk.is_local() {
         let start = Instant::now();
-        match disk.read_file_zero_copy(bucket, path, offset, length).await {
+        match disk.read_file_mmap_copy(bucket, path, offset, length).await {
             Ok(bytes) => {
                 let duration_ms = start.elapsed().as_secs_f64() * 1000.0;
 
@@ -201,7 +201,7 @@ fn bitrot_encoded_range(offset: usize, length: usize, shard_size: usize, checksu
 /// * `shard_size` - Shard size for erasure coding
 /// * `checksum_algo` - Hash algorithm for bitrot verification
 /// * `skip_verify` - If true, skip checksum verification
-/// * `use_mmap_read` - If true, use zero-copy read (mmap on Unix)
+/// * `use_mmap_read` - If true, use mmap-copy read (mmap on Unix)
 #[allow(clippy::too_many_arguments)]
 pub async fn create_bitrot_reader(
     inline_data: Option<&[u8]>,
@@ -360,7 +360,7 @@ mod tests {
         let shard_size = 16;
         let checksum_algo = HashAlgorithm::HighwayHash256S;
 
-        // Test with zero-copy enabled (should work the same for inline data)
+        // Test with mmap-copy enabled (should work the same for inline data)
         let result = create_bitrot_reader(
             Some(test_data),
             None,