dirstate-v2: don't mmap the data file when on NFS
`mmap` on NFS will trigger a SIGBUS when the mmap'ed file is deleted, which
wouldn't work in our case. Also, the performance advantage of using mmap on
NFS is debatable at best.
--- a/rust/hg-core/src/repo.rs Thu Dec 08 16:38:39 2022 +0100
+++ b/rust/hg-core/src/repo.rs Mon Nov 28 12:33:20 2022 +0100
@@ -320,7 +320,14 @@
.set(Some(docket.uuid.to_owned()));
let data_size = docket.data_size();
let metadata = docket.tree_metadata();
- if let Some(data_mmap) = self
+ if crate::vfs::is_on_nfs_mount(docket.data_filename()) {
+ // Don't mmap on NFS to prevent `SIGBUS` error on deletion
+ OwningDirstateMap::new_v2(
+ self.hg_vfs().read(docket.data_filename())?,
+ data_size,
+ metadata,
+ )
+ } else if let Some(data_mmap) = self
.hg_vfs()
.mmap_open(docket.data_filename())
.io_not_found_as_none()?
--- a/rust/hg-core/src/vfs.rs Thu Dec 08 16:38:39 2022 +0100
+++ b/rust/hg-core/src/vfs.rs Mon Nov 28 12:33:20 2022 +0100
@@ -172,3 +172,24 @@
pub(crate) fn is_file(path: impl AsRef<Path>) -> Result<bool, HgError> {
Ok(fs_metadata(path)?.map_or(false, |meta| meta.is_file()))
}
+
+/// Returns whether the given `path` is on a network file system.
+/// Taken from `cargo`'s codebase.
+#[cfg(target_os = "linux")]
+pub(crate) fn is_on_nfs_mount(path: impl AsRef<Path>) -> bool {
+ use std::ffi::CString;
+ use std::mem;
+ use std::os::unix::prelude::*;
+
+ let path = match CString::new(path.as_ref().as_os_str().as_bytes()) {
+ Ok(path) => path,
+ Err(_) => return false,
+ };
+
+ unsafe {
+ let mut buf: libc::statfs = mem::zeroed();
+ let r = libc::statfs(path.as_ptr(), &mut buf);
+
+ r == 0 && buf.f_type as u32 == libc::NFS_SUPER_MAGIC as u32
+ }
+}