From 3b60a079a7c6809624dcedde0730de11141b6441 Mon Sep 17 00:00:00 2001
From: Sebastian Thiel <sebastian.thiel@icloud.com>
Date: Sat, 9 Mar 2024 19:10:08 +0100
Subject: [PATCH] fix: assure memory maps are created with `MAP_PRIVATE`
 (#1312)

That way, the mmap process should work under more circumstances.
---
 gix-commitgraph/src/file/init.rs   | 6 ++----
 gix-index/src/file/init.rs         | 4 +---
 gix-pack/src/lib.rs                | 2 +-
 gix-pack/tests/pack/index.rs       | 2 +-
 gix-ref/src/store/packed/buffer.rs | 3 +--
 5 files changed, 6 insertions(+), 11 deletions(-)

diff --git a/gix-commitgraph/src/file/init.rs b/gix-commitgraph/src/file/init.rs
index 51c2739501f..78e621ab0ae 100644
--- a/gix-commitgraph/src/file/init.rs
+++ b/gix-commitgraph/src/file/init.rs
@@ -4,9 +4,6 @@ use std::{
     path::Path,
 };
 
-use bstr::ByteSlice;
-use memmap2::Mmap;
-
 use crate::{
     file::{
         ChunkId, BASE_GRAPHS_LIST_CHUNK_ID, COMMIT_DATA_CHUNK_ID, COMMIT_DATA_ENTRY_SIZE_SANS_HASH,
@@ -14,6 +11,7 @@ use crate::{
     },
     File,
 };
+use bstr::ByteSlice;
 
 /// The error used in [`File::at()`].
 #[derive(thiserror::Error, Debug)]
@@ -246,7 +244,7 @@ impl TryFrom<&Path> for File {
                 // SAFETY: we have to take the risk of somebody changing the file underneath. Git never writes into the same file.
                 #[allow(unsafe_code)]
                 unsafe {
-                    Mmap::map(&file)
+                    memmap2::MmapOptions::new().map_copy_read_only(&file)
                 }
             })
             .map_err(|e| Error::Io {
diff --git a/gix-index/src/file/init.rs b/gix-index/src/file/init.rs
index 88dd86af9ac..10c01015fcb 100644
--- a/gix-index/src/file/init.rs
+++ b/gix-index/src/file/init.rs
@@ -2,8 +2,6 @@
 
 use std::path::{Path, PathBuf};
 
-use memmap2::Mmap;
-
 use crate::{decode, extension, File, State};
 
 mod error {
@@ -64,7 +62,7 @@ impl File {
             let mut file = std::fs::File::open(&path)?;
             // SAFETY: we have to take the risk of somebody changing the file underneath. Git never writes into the same file.
             #[allow(unsafe_code)]
-            let data = unsafe { Mmap::map(&file)? };
+            let data = unsafe { memmap2::MmapOptions::new().map_copy_read_only(&file)? };
 
             if !skip_hash {
                 // Note that even though it's trivial to offload this into a thread, which is worth it for all but the smallest
diff --git a/gix-pack/src/lib.rs b/gix-pack/src/lib.rs
index b56d1fe983e..ae6f3ffe99c 100755
--- a/gix-pack/src/lib.rs
+++ b/gix-pack/src/lib.rs
@@ -55,7 +55,7 @@ mod mmap {
         // SAFETY: we have to take the risk of somebody changing the file underneath. Git never writes into the same file.
         #[allow(unsafe_code)]
         unsafe {
-            memmap2::Mmap::map(&file)
+            memmap2::MmapOptions::new().map_copy_read_only(&file)
         }
     }
 }
diff --git a/gix-pack/tests/pack/index.rs b/gix-pack/tests/pack/index.rs
index 1a168b28e79..ddc90cc87c0 100644
--- a/gix-pack/tests/pack/index.rs
+++ b/gix-pack/tests/pack/index.rs
@@ -148,7 +148,7 @@ mod version {
                     desired_kind,
                     || {
                         let file = std::fs::File::open(fixture_path(data_path))?;
-                        let map = unsafe { memmap2::Mmap::map(&file)? };
+                        let map = unsafe { memmap2::MmapOptions::map_copy_read_only(&file)? };
                         Ok((slice_map, map))
                     },
                     pack_iter,
diff --git a/gix-ref/src/store/packed/buffer.rs b/gix-ref/src/store/packed/buffer.rs
index 40fbf88e24a..2283cf9873b 100644
--- a/gix-ref/src/store/packed/buffer.rs
+++ b/gix-ref/src/store/packed/buffer.rs
@@ -19,7 +19,6 @@ impl AsRef<[u8]> for packed::Backing {
 pub mod open {
     use std::path::PathBuf;
 
-    use memmap2::Mmap;
     use winnow::{prelude::*, stream::Offset};
 
     use crate::store_impl::packed;
@@ -81,7 +80,7 @@ pub mod open {
                     // SAFETY: we have to take the risk of somebody changing the file underneath. Git never writes into the same file.
                     #[allow(unsafe_code)]
                     unsafe {
-                        Mmap::map(&std::fs::File::open(&path)?)?
+                        memmap2::MmapOptions::new().map_copy_read_only(&std::fs::File::open(&path)?)?
                     },
                 )
             };