diff options
Diffstat (limited to 'compiler/rustc_data_structures')
| -rw-r--r-- | compiler/rustc_data_structures/src/memmap.rs | 10 |
1 files changed, 8 insertions, 2 deletions
diff --git a/compiler/rustc_data_structures/src/memmap.rs b/compiler/rustc_data_structures/src/memmap.rs index 30403a61442..c7f66b2fee8 100644 --- a/compiler/rustc_data_structures/src/memmap.rs +++ b/compiler/rustc_data_structures/src/memmap.rs @@ -18,8 +18,14 @@ impl Mmap { /// However in practice most callers do not ensure this, so uses of this function are likely unsound. #[inline] pub unsafe fn map(file: File) -> io::Result<Self> { - // Safety: the caller must ensure that this is safe. - unsafe { memmap2::Mmap::map(&file).map(Mmap) } + // By default, memmap2 creates shared mappings, implying that we could see updates to the + // file through the mapping. That would violate our precondition; so by requesting a + // map_copy_read_only we do not lose anything. + // This mapping mode also improves our support for filesystems such as cacheless virtiofs. + // For more details see https://github.com/rust-lang/rust/issues/122262 + // + // SAFETY: The caller must ensure that this is safe. + unsafe { memmap2::MmapOptions::new().map_copy_read_only(&file).map(Mmap) } } } |