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bypass auto_da_alloc for metadata files

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This commit is contained in:
The8472 2021-02-13 00:54:17 +01:00
parent 3f5aee2d52
commit 6a679ffc81
2 changed files with 19 additions and 1 deletions
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2
compiler/rustc_interface/src/passes.rs
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@ -983,7 +983,7 @@ fn encode_and_write_metadata(
.unwrap_or_else(|err| tcx.sess.fatal(&format!("couldn't create a temp dir: {}", err)));
let metadata_tmpdir = MaybeTempDir::new(metadata_tmpdir, tcx.sess.opts.cg.save_temps);
let metadata_filename = emit_metadata(tcx.sess, &metadata, &metadata_tmpdir);
if let Err(e) = fs::rename(&metadata_filename, &out_filename) {
if let Err(e) = util::non_durable_rename(&metadata_filename, &out_filename) {
tcx.sess.fatal(&format!("failed to write {}: {}", out_filename.display(), e));
}
if tcx.sess.opts.json_artifact_notifications {

18
compiler/rustc_interface/src/util.rs
View file

@ -670,6 +670,24 @@ pub fn build_output_filenames(
}
}
#[cfg(not(target_os = "linux"))]
pub fn non_durable_rename(src: &Path, dst: &Path) -> std::io::Result<()> {
std::fs::rename(src, dst)
}
/// This function attempts to bypass the auto_da_alloc heuristic implemented by some filesystems
/// such as btrfs and ext4. When renaming over a file that already exists then they will "helpfully"
/// write back the source file before committing the rename in case a developer forgot some of
/// the fsyncs in the open/write/fsync(file)/rename/fsync(dir) dance for atomic file updates.
///
/// To avoid triggering this heuristic we delete the destination first, if it exists.
/// The cost of an extra syscall is much lower than getting descheduled for the sync IO.
#[cfg(target_os = "linux")]
pub fn non_durable_rename(src: &Path, dst: &Path) -> std::io::Result<()> {
let _ = std::fs::remove_file(dst);
std::fs::rename(src, dst)
}
// Note: Also used by librustdoc, see PR #43348. Consider moving this struct elsewhere.
//
// FIXME: Currently the `everybody_loops` transformation is not applied to: