| //! This module manages how the incremental compilation cache is represented in |
| //! the file system. |
| //! |
| //! Incremental compilation caches are managed according to a copy-on-write |
| //! strategy: Once a complete, consistent cache version is finalized, it is |
| //! never modified. Instead, when a subsequent compilation session is started, |
| //! the compiler will allocate a new version of the cache that starts out as |
| //! a copy of the previous version. Then only this new copy is modified and it |
| //! will not be visible to other processes until it is finalized. This ensures |
| //! that multiple compiler processes can be executed concurrently for the same |
| //! crate without interfering with each other or blocking each other. |
| //! |
| //! More concretely this is implemented via the following protocol: |
| //! |
| //! 1. For a newly started compilation session, the compiler allocates a |
| //! new `session` directory within the incremental compilation directory. |
| //! This session directory will have a unique name that ends with the suffix |
| //! "-working" and that contains a creation timestamp. |
| //! 2. Next, the compiler looks for the newest finalized session directory, |
| //! that is, a session directory from a previous compilation session that |
| //! has been marked as valid and consistent. A session directory is |
| //! considered finalized if the "-working" suffix in the directory name has |
| //! been replaced by the SVH of the crate. |
| //! 3. Once the compiler has found a valid, finalized session directory, it will |
| //! hard-link/copy its contents into the new "-working" directory. If all |
| //! goes well, it will have its own, private copy of the source directory and |
| //! subsequently not have to worry about synchronizing with other compiler |
| //! processes. |
| //! 4. Now the compiler can do its normal compilation process, which involves |
| //! reading and updating its private session directory. |
| //! 5. When compilation finishes without errors, the private session directory |
| //! will be in a state where it can be used as input for other compilation |
| //! sessions. That is, it will contain a dependency graph and cache artifacts |
| //! that are consistent with the state of the source code it was compiled |
| //! from, with no need to change them ever again. At this point, the compiler |
| //! finalizes and "publishes" its private session directory by renaming it |
| //! from "s-{timestamp}-{random}-working" to "s-{timestamp}-{SVH}". |
| //! 6. At this point the "old" session directory that we copied our data from |
| //! at the beginning of the session has become obsolete because we have just |
| //! published a more current version. Thus the compiler will delete it. |
| //! |
| //! ## Garbage Collection |
| //! |
| //! Naively following the above protocol might lead to old session directories |
| //! piling up if a compiler instance crashes for some reason before its able to |
| //! remove its private session directory. In order to avoid wasting disk space, |
| //! the compiler also does some garbage collection each time it is started in |
| //! incremental compilation mode. Specifically, it will scan the incremental |
| //! compilation directory for private session directories that are not in use |
| //! any more and will delete those. It will also delete any finalized session |
| //! directories for a given crate except for the most recent one. |
| //! |
| //! ## Synchronization |
| //! |
| //! There is some synchronization needed in order for the compiler to be able to |
| //! determine whether a given private session directory is not in use any more. |
| //! This is done by creating a lock file for each session directory and |
| //! locking it while the directory is still being used. Since file locks have |
| //! operating system support, we can rely on the lock being released if the |
| //! compiler process dies for some unexpected reason. Thus, when garbage |
| //! collecting private session directories, the collecting process can determine |
| //! whether the directory is still in use by trying to acquire a lock on the |
| //! file. If locking the file fails, the original process must still be alive. |
| //! If locking the file succeeds, we know that the owning process is not alive |
| //! any more and we can safely delete the directory. |
| //! There is still a small time window between the original process creating the |
| //! lock file and actually locking it. In order to minimize the chance that |
| //! another process tries to acquire the lock in just that instance, only |
| //! session directories that are older than a few seconds are considered for |
| //! garbage collection. |
| //! |
| //! Another case that has to be considered is what happens if one process |
| //! deletes a finalized session directory that another process is currently |
| //! trying to copy from. This case is also handled via the lock file. Before |
| //! a process starts copying a finalized session directory, it will acquire a |
| //! shared lock on the directory's lock file. Any garbage collecting process, |
| //! on the other hand, will acquire an exclusive lock on the lock file. |
| //! Thus, if a directory is being collected, any reader process will fail |
| //! acquiring the shared lock and will leave the directory alone. Conversely, |
| //! if a collecting process can't acquire the exclusive lock because the |
| //! directory is currently being read from, it will leave collecting that |
| //! directory to another process at a later point in time. |
| //! The exact same scheme is also used when reading the metadata hashes file |
| //! from an extern crate. When a crate is compiled, the hash values of its |
| //! metadata are stored in a file in its session directory. When the |
| //! compilation session of another crate imports the first crate's metadata, |
| //! it also has to read in the accompanying metadata hashes. It thus will access |
| //! the finalized session directory of all crates it links to and while doing |
| //! so, it will also place a read lock on that the respective session directory |
| //! so that it won't be deleted while the metadata hashes are loaded. |
| //! |
| //! ## Preconditions |
| //! |
| //! This system relies on two features being available in the file system in |
| //! order to work really well: file locking and hard linking. |
| //! If hard linking is not available (like on FAT) the data in the cache |
| //! actually has to be copied at the beginning of each session. |
| //! If file locking does not work reliably (like on NFS), some of the |
| //! synchronization will go haywire. |
| //! In both cases we recommend to locate the incremental compilation directory |
| //! on a file system that supports these things. |
| //! It might be a good idea though to try and detect whether we are on an |
| //! unsupported file system and emit a warning in that case. This is not yet |
| //! implemented. |
| |
| use std::fs as std_fs; |
| use std::io::{self, ErrorKind}; |
| use std::path::{Path, PathBuf}; |
| use std::time::{Duration, SystemTime, UNIX_EPOCH}; |
| |
| use rand::{RngCore, rng}; |
| use rustc_data_structures::base_n::{BaseNString, CASE_INSENSITIVE, ToBaseN}; |
| use rustc_data_structures::fx::{FxHashSet, FxIndexSet}; |
| use rustc_data_structures::svh::Svh; |
| use rustc_data_structures::unord::{UnordMap, UnordSet}; |
| use rustc_data_structures::{base_n, flock}; |
| use rustc_fs_util::{LinkOrCopy, link_or_copy, try_canonicalize}; |
| use rustc_middle::bug; |
| use rustc_session::config::CrateType; |
| use rustc_session::output::collect_crate_types; |
| use rustc_session::{Session, StableCrateId}; |
| use rustc_span::Symbol; |
| use tracing::debug; |
| |
| use crate::errors; |
| |
| #[cfg(test)] |
| mod tests; |
| |
| const LOCK_FILE_EXT: &str = ".lock"; |
| const DEP_GRAPH_FILENAME: &str = "dep-graph.bin"; |
| const STAGING_DEP_GRAPH_FILENAME: &str = "dep-graph.part.bin"; |
| const WORK_PRODUCTS_FILENAME: &str = "work-products.bin"; |
| const QUERY_CACHE_FILENAME: &str = "query-cache.bin"; |
| |
| // We encode integers using the following base, so they are shorter than decimal |
| // or hexadecimal numbers (we want short file and directory names). Since these |
| // numbers will be used in file names, we choose an encoding that is not |
| // case-sensitive (as opposed to base64, for example). |
| const INT_ENCODE_BASE: usize = base_n::CASE_INSENSITIVE; |
| |
| /// Returns the path to a session's dependency graph. |
| pub(crate) fn dep_graph_path(sess: &Session) -> PathBuf { |
| in_incr_comp_dir_sess(sess, DEP_GRAPH_FILENAME) |
| } |
| |
| /// Returns the path to a session's staging dependency graph. |
| /// |
| /// On the difference between dep-graph and staging dep-graph, |
| /// see `build_dep_graph`. |
| pub(crate) fn staging_dep_graph_path(sess: &Session) -> PathBuf { |
| in_incr_comp_dir_sess(sess, STAGING_DEP_GRAPH_FILENAME) |
| } |
| |
| pub(crate) fn work_products_path(sess: &Session) -> PathBuf { |
| in_incr_comp_dir_sess(sess, WORK_PRODUCTS_FILENAME) |
| } |
| |
| /// Returns the path to a session's query cache. |
| pub(crate) fn query_cache_path(sess: &Session) -> PathBuf { |
| in_incr_comp_dir_sess(sess, QUERY_CACHE_FILENAME) |
| } |
| |
| /// Locks a given session directory. |
| fn lock_file_path(session_dir: &Path) -> PathBuf { |
| let crate_dir = session_dir.parent().unwrap(); |
| |
| let directory_name = session_dir |
| .file_name() |
| .unwrap() |
| .to_str() |
| .expect("malformed session dir name: contains non-Unicode characters"); |
| |
| let dash_indices: Vec<_> = directory_name.match_indices('-').map(|(idx, _)| idx).collect(); |
| if dash_indices.len() != 3 { |
| bug!( |
| "Encountered incremental compilation session directory with \ |
| malformed name: {}", |
| session_dir.display() |
| ) |
| } |
| |
| crate_dir.join(&directory_name[0..dash_indices[2]]).with_extension(&LOCK_FILE_EXT[1..]) |
| } |
| |
| /// Returns the path for a given filename within the incremental compilation directory |
| /// in the current session. |
| pub fn in_incr_comp_dir_sess(sess: &Session, file_name: &str) -> PathBuf { |
| in_incr_comp_dir(&sess.incr_comp_session_dir(), file_name) |
| } |
| |
| /// Returns the path for a given filename within the incremental compilation directory, |
| /// not necessarily from the current session. |
| /// |
| /// To ensure the file is part of the current session, use [`in_incr_comp_dir_sess`]. |
| pub fn in_incr_comp_dir(incr_comp_session_dir: &Path, file_name: &str) -> PathBuf { |
| incr_comp_session_dir.join(file_name) |
| } |
| |
| /// Allocates the private session directory. |
| /// |
| /// If the result of this function is `Ok`, we have a valid incremental |
| /// compilation session directory. A valid session |
| /// directory is one that contains a locked lock file. It may or may not contain |
| /// a dep-graph and work products from a previous session. |
| /// |
| /// This always attempts to load a dep-graph from the directory. |
| /// If loading fails for some reason, we fallback to a disabled `DepGraph`. |
| /// See [`rustc_interface::queries::dep_graph`]. |
| /// |
| /// If this function returns an error, it may leave behind an invalid session directory. |
| /// The garbage collection will take care of it. |
| /// |
| /// [`rustc_interface::queries::dep_graph`]: ../../rustc_interface/struct.Queries.html#structfield.dep_graph |
| pub(crate) fn prepare_session_directory(sess: &Session, crate_name: Symbol) { |
| if sess.opts.incremental.is_none() { |
| return; |
| } |
| |
| let _timer = sess.timer("incr_comp_prepare_session_directory"); |
| |
| debug!("prepare_session_directory"); |
| |
| // {incr-comp-dir}/{crate-name-and-disambiguator} |
| let crate_dir = crate_path(sess, crate_name); |
| debug!("crate-dir: {}", crate_dir.display()); |
| create_dir(sess, &crate_dir, "crate"); |
| |
| // Hack: canonicalize the path *after creating the directory* |
| // because, on windows, long paths can cause problems; |
| // canonicalization inserts this weird prefix that makes windows |
| // tolerate long paths. |
| let crate_dir = match try_canonicalize(&crate_dir) { |
| Ok(v) => v, |
| Err(err) => { |
| sess.dcx().emit_fatal(errors::CanonicalizePath { path: crate_dir, err }); |
| } |
| }; |
| |
| let mut source_directories_already_tried = FxHashSet::default(); |
| |
| loop { |
| // Generate a session directory of the form: |
| // |
| // {incr-comp-dir}/{crate-name-and-disambiguator}/s-{timestamp}-{random}-working |
| let session_dir = generate_session_dir_path(&crate_dir); |
| debug!("session-dir: {}", session_dir.display()); |
| |
| // Lock the new session directory. If this fails, return an |
| // error without retrying |
| let (directory_lock, lock_file_path) = lock_directory(sess, &session_dir); |
| |
| // Now that we have the lock, we can actually create the session |
| // directory |
| create_dir(sess, &session_dir, "session"); |
| |
| // Find a suitable source directory to copy from. Ignore those that we |
| // have already tried before. |
| let source_directory = find_source_directory(&crate_dir, &source_directories_already_tried); |
| |
| let Some(source_directory) = source_directory else { |
| // There's nowhere to copy from, we're done |
| debug!( |
| "no source directory found. Continuing with empty session \ |
| directory." |
| ); |
| |
| sess.init_incr_comp_session(session_dir, directory_lock); |
| return; |
| }; |
| |
| debug!("attempting to copy data from source: {}", source_directory.display()); |
| |
| // Try copying over all files from the source directory |
| if let Ok(allows_links) = copy_files(sess, &session_dir, &source_directory) { |
| debug!("successfully copied data from: {}", source_directory.display()); |
| |
| if !allows_links { |
| sess.dcx().emit_warn(errors::HardLinkFailed { path: &session_dir }); |
| } |
| |
| sess.init_incr_comp_session(session_dir, directory_lock); |
| return; |
| } else { |
| debug!("copying failed - trying next directory"); |
| |
| // Something went wrong while trying to copy/link files from the |
| // source directory. Try again with a different one. |
| source_directories_already_tried.insert(source_directory); |
| |
| // Try to remove the session directory we just allocated. We don't |
| // know if there's any garbage in it from the failed copy action. |
| if let Err(err) = std_fs::remove_dir_all(&session_dir) { |
| sess.dcx().emit_warn(errors::DeletePartial { path: &session_dir, err }); |
| } |
| |
| delete_session_dir_lock_file(sess, &lock_file_path); |
| drop(directory_lock); |
| } |
| } |
| } |
| |
| /// This function finalizes and thus 'publishes' the session directory by |
| /// renaming it to `s-{timestamp}-{svh}` and releasing the file lock. |
| /// If there have been compilation errors, however, this function will just |
| /// delete the presumably invalid session directory. |
| pub fn finalize_session_directory(sess: &Session, svh: Option<Svh>) { |
| if sess.opts.incremental.is_none() { |
| return; |
| } |
| // The svh is always produced when incr. comp. is enabled. |
| let svh = svh.unwrap(); |
| |
| let _timer = sess.timer("incr_comp_finalize_session_directory"); |
| |
| let incr_comp_session_dir: PathBuf = sess.incr_comp_session_dir().clone(); |
| |
| if sess.dcx().has_errors_or_delayed_bugs().is_some() { |
| // If there have been any errors during compilation, we don't want to |
| // publish this session directory. Rather, we'll just delete it. |
| |
| debug!( |
| "finalize_session_directory() - invalidating session directory: {}", |
| incr_comp_session_dir.display() |
| ); |
| |
| if let Err(err) = std_fs::remove_dir_all(&*incr_comp_session_dir) { |
| sess.dcx().emit_warn(errors::DeleteFull { path: &incr_comp_session_dir, err }); |
| } |
| |
| let lock_file_path = lock_file_path(&*incr_comp_session_dir); |
| delete_session_dir_lock_file(sess, &lock_file_path); |
| sess.mark_incr_comp_session_as_invalid(); |
| } |
| |
| debug!("finalize_session_directory() - session directory: {}", incr_comp_session_dir.display()); |
| |
| let mut sub_dir_name = incr_comp_session_dir |
| .file_name() |
| .unwrap() |
| .to_str() |
| .expect("malformed session dir name: contains non-Unicode characters") |
| .to_string(); |
| |
| // Keep the 's-{timestamp}-{random-number}' prefix, but replace "working" with the SVH of the crate |
| sub_dir_name.truncate(sub_dir_name.len() - "working".len()); |
| // Double-check that we kept this: "s-{timestamp}-{random-number}-" |
| assert!(sub_dir_name.ends_with('-'), "{:?}", sub_dir_name); |
| assert!(sub_dir_name.as_bytes().iter().filter(|b| **b == b'-').count() == 3); |
| |
| // Append the SVH |
| sub_dir_name.push_str(&svh.as_u128().to_base_fixed_len(CASE_INSENSITIVE)); |
| |
| // Create the full path |
| let new_path = incr_comp_session_dir.parent().unwrap().join(&*sub_dir_name); |
| debug!("finalize_session_directory() - new path: {}", new_path.display()); |
| |
| match rename_path_with_retry(&*incr_comp_session_dir, &new_path, 3) { |
| Ok(_) => { |
| debug!("finalize_session_directory() - directory renamed successfully"); |
| |
| // This unlocks the directory |
| sess.finalize_incr_comp_session(new_path); |
| } |
| Err(e) => { |
| // Warn about the error. However, no need to abort compilation now. |
| sess.dcx().emit_warn(errors::Finalize { path: &incr_comp_session_dir, err: e }); |
| |
| debug!("finalize_session_directory() - error, marking as invalid"); |
| // Drop the file lock, so we can garage collect |
| sess.mark_incr_comp_session_as_invalid(); |
| } |
| } |
| |
| let _ = garbage_collect_session_directories(sess); |
| } |
| |
| pub(crate) fn delete_all_session_dir_contents(sess: &Session) -> io::Result<()> { |
| let sess_dir_iterator = sess.incr_comp_session_dir().read_dir()?; |
| for entry in sess_dir_iterator { |
| let entry = entry?; |
| safe_remove_file(&entry.path())? |
| } |
| Ok(()) |
| } |
| |
| fn copy_files(sess: &Session, target_dir: &Path, source_dir: &Path) -> Result<bool, ()> { |
| // We acquire a shared lock on the lock file of the directory, so that |
| // nobody deletes it out from under us while we are reading from it. |
| let lock_file_path = lock_file_path(source_dir); |
| |
| // not exclusive |
| let Ok(_lock) = flock::Lock::new( |
| &lock_file_path, |
| false, // don't wait, |
| false, // don't create |
| false, |
| ) else { |
| // Could not acquire the lock, don't try to copy from here |
| return Err(()); |
| }; |
| |
| let Ok(source_dir_iterator) = source_dir.read_dir() else { |
| return Err(()); |
| }; |
| |
| let mut files_linked = 0; |
| let mut files_copied = 0; |
| |
| for entry in source_dir_iterator { |
| match entry { |
| Ok(entry) => { |
| let file_name = entry.file_name(); |
| |
| let target_file_path = target_dir.join(file_name); |
| let source_path = entry.path(); |
| |
| debug!("copying into session dir: {}", source_path.display()); |
| match link_or_copy(source_path, target_file_path) { |
| Ok(LinkOrCopy::Link) => files_linked += 1, |
| Ok(LinkOrCopy::Copy) => files_copied += 1, |
| Err(_) => return Err(()), |
| } |
| } |
| Err(_) => return Err(()), |
| } |
| } |
| |
| if sess.opts.unstable_opts.incremental_info { |
| eprintln!( |
| "[incremental] session directory: \ |
| {files_linked} files hard-linked" |
| ); |
| eprintln!( |
| "[incremental] session directory: \ |
| {files_copied} files copied" |
| ); |
| } |
| |
| Ok(files_linked > 0 || files_copied == 0) |
| } |
| |
| /// Generates unique directory path of the form: |
| /// {crate_dir}/s-{timestamp}-{random-number}-working |
| fn generate_session_dir_path(crate_dir: &Path) -> PathBuf { |
| let timestamp = timestamp_to_string(SystemTime::now()); |
| debug!("generate_session_dir_path: timestamp = {}", timestamp); |
| let random_number = rng().next_u32(); |
| debug!("generate_session_dir_path: random_number = {}", random_number); |
| |
| // Chop the first 3 characters off the timestamp. Those 3 bytes will be zero for a while. |
| let (zeroes, timestamp) = timestamp.split_at(3); |
| assert_eq!(zeroes, "000"); |
| let directory_name = |
| format!("s-{}-{}-working", timestamp, random_number.to_base_fixed_len(CASE_INSENSITIVE)); |
| debug!("generate_session_dir_path: directory_name = {}", directory_name); |
| let directory_path = crate_dir.join(directory_name); |
| debug!("generate_session_dir_path: directory_path = {}", directory_path.display()); |
| directory_path |
| } |
| |
| fn create_dir(sess: &Session, path: &Path, dir_tag: &str) { |
| match std_fs::create_dir_all(path) { |
| Ok(()) => { |
| debug!("{} directory created successfully", dir_tag); |
| } |
| Err(err) => sess.dcx().emit_fatal(errors::CreateIncrCompDir { tag: dir_tag, path, err }), |
| } |
| } |
| |
| /// Allocate the lock-file and lock it. |
| fn lock_directory(sess: &Session, session_dir: &Path) -> (flock::Lock, PathBuf) { |
| let lock_file_path = lock_file_path(session_dir); |
| debug!("lock_directory() - lock_file: {}", lock_file_path.display()); |
| |
| match flock::Lock::new( |
| &lock_file_path, |
| false, // don't wait |
| true, // create the lock file |
| true, |
| ) { |
| // the lock should be exclusive |
| Ok(lock) => (lock, lock_file_path), |
| Err(lock_err) => { |
| let is_unsupported_lock = flock::Lock::error_unsupported(&lock_err); |
| sess.dcx().emit_fatal(errors::CreateLock { |
| lock_err, |
| session_dir, |
| is_unsupported_lock, |
| is_cargo: rustc_session::utils::was_invoked_from_cargo(), |
| }); |
| } |
| } |
| } |
| |
| fn delete_session_dir_lock_file(sess: &Session, lock_file_path: &Path) { |
| if let Err(err) = safe_remove_file(lock_file_path) { |
| sess.dcx().emit_warn(errors::DeleteLock { path: lock_file_path, err }); |
| } |
| } |
| |
| /// Finds the most recent published session directory that is not in the |
| /// ignore-list. |
| fn find_source_directory( |
| crate_dir: &Path, |
| source_directories_already_tried: &FxHashSet<PathBuf>, |
| ) -> Option<PathBuf> { |
| let iter = crate_dir |
| .read_dir() |
| .unwrap() // FIXME |
| .filter_map(|e| e.ok().map(|e| e.path())); |
| |
| find_source_directory_in_iter(iter, source_directories_already_tried) |
| } |
| |
| fn find_source_directory_in_iter<I>( |
| iter: I, |
| source_directories_already_tried: &FxHashSet<PathBuf>, |
| ) -> Option<PathBuf> |
| where |
| I: Iterator<Item = PathBuf>, |
| { |
| let mut best_candidate = (UNIX_EPOCH, None); |
| |
| for session_dir in iter { |
| debug!("find_source_directory_in_iter - inspecting `{}`", session_dir.display()); |
| |
| let Some(directory_name) = session_dir.file_name().unwrap().to_str() else { |
| debug!("find_source_directory_in_iter - ignoring"); |
| continue; |
| }; |
| |
| if source_directories_already_tried.contains(&session_dir) |
| || !is_session_directory(&directory_name) |
| || !is_finalized(&directory_name) |
| { |
| debug!("find_source_directory_in_iter - ignoring"); |
| continue; |
| } |
| |
| let timestamp = match extract_timestamp_from_session_dir(&directory_name) { |
| Ok(timestamp) => timestamp, |
| Err(e) => { |
| debug!("unexpected incr-comp session dir: {}: {}", session_dir.display(), e); |
| continue; |
| } |
| }; |
| |
| if timestamp > best_candidate.0 { |
| best_candidate = (timestamp, Some(session_dir.clone())); |
| } |
| } |
| |
| best_candidate.1 |
| } |
| |
| fn is_finalized(directory_name: &str) -> bool { |
| !directory_name.ends_with("-working") |
| } |
| |
| fn is_session_directory(directory_name: &str) -> bool { |
| directory_name.starts_with("s-") && !directory_name.ends_with(LOCK_FILE_EXT) |
| } |
| |
| fn is_session_directory_lock_file(file_name: &str) -> bool { |
| file_name.starts_with("s-") && file_name.ends_with(LOCK_FILE_EXT) |
| } |
| |
| fn extract_timestamp_from_session_dir(directory_name: &str) -> Result<SystemTime, &'static str> { |
| if !is_session_directory(directory_name) { |
| return Err("not a directory"); |
| } |
| |
| let dash_indices: Vec<_> = directory_name.match_indices('-').map(|(idx, _)| idx).collect(); |
| if dash_indices.len() != 3 { |
| return Err("not three dashes in name"); |
| } |
| |
| string_to_timestamp(&directory_name[dash_indices[0] + 1..dash_indices[1]]) |
| } |
| |
| fn timestamp_to_string(timestamp: SystemTime) -> BaseNString { |
| let duration = timestamp.duration_since(UNIX_EPOCH).unwrap(); |
| let micros: u64 = duration.as_micros().try_into().unwrap(); |
| micros.to_base_fixed_len(CASE_INSENSITIVE) |
| } |
| |
| fn string_to_timestamp(s: &str) -> Result<SystemTime, &'static str> { |
| let micros_since_unix_epoch = match u64::from_str_radix(s, INT_ENCODE_BASE as u32) { |
| Ok(micros) => micros, |
| Err(_) => return Err("timestamp not an int"), |
| }; |
| |
| let duration = Duration::from_micros(micros_since_unix_epoch); |
| Ok(UNIX_EPOCH + duration) |
| } |
| |
| fn crate_path(sess: &Session, crate_name: Symbol) -> PathBuf { |
| let incr_dir = sess.opts.incremental.as_ref().unwrap().clone(); |
| |
| let crate_types = collect_crate_types(sess, &[]); |
| let stable_crate_id = StableCrateId::new( |
| crate_name, |
| crate_types.contains(&CrateType::Executable), |
| sess.opts.cg.metadata.clone(), |
| sess.cfg_version, |
| ); |
| |
| let crate_name = |
| format!("{crate_name}-{}", stable_crate_id.as_u64().to_base_fixed_len(CASE_INSENSITIVE)); |
| incr_dir.join(crate_name) |
| } |
| |
| fn is_old_enough_to_be_collected(timestamp: SystemTime) -> bool { |
| timestamp < SystemTime::now() - Duration::from_secs(10) |
| } |
| |
| /// Runs garbage collection for the current session. |
| pub(crate) fn garbage_collect_session_directories(sess: &Session) -> io::Result<()> { |
| debug!("garbage_collect_session_directories() - begin"); |
| |
| let session_directory = sess.incr_comp_session_dir(); |
| debug!( |
| "garbage_collect_session_directories() - session directory: {}", |
| session_directory.display() |
| ); |
| |
| let crate_directory = session_directory.parent().unwrap(); |
| debug!( |
| "garbage_collect_session_directories() - crate directory: {}", |
| crate_directory.display() |
| ); |
| |
| // First do a pass over the crate directory, collecting lock files and |
| // session directories |
| let mut session_directories = FxIndexSet::default(); |
| let mut lock_files = UnordSet::default(); |
| |
| for dir_entry in crate_directory.read_dir()? { |
| let Ok(dir_entry) = dir_entry else { |
| // Ignore any errors |
| continue; |
| }; |
| |
| let entry_name = dir_entry.file_name(); |
| let Some(entry_name) = entry_name.to_str() else { |
| continue; |
| }; |
| |
| if is_session_directory_lock_file(&entry_name) { |
| lock_files.insert(entry_name.to_string()); |
| } else if is_session_directory(&entry_name) { |
| session_directories.insert(entry_name.to_string()); |
| } else { |
| // This is something we don't know, leave it alone |
| } |
| } |
| session_directories.sort(); |
| |
| // Now map from lock files to session directories |
| let lock_file_to_session_dir: UnordMap<String, Option<String>> = lock_files |
| .into_items() |
| .map(|lock_file_name| { |
| assert!(lock_file_name.ends_with(LOCK_FILE_EXT)); |
| let dir_prefix_end = lock_file_name.len() - LOCK_FILE_EXT.len(); |
| let session_dir = { |
| let dir_prefix = &lock_file_name[0..dir_prefix_end]; |
| session_directories.iter().find(|dir_name| dir_name.starts_with(dir_prefix)) |
| }; |
| (lock_file_name, session_dir.map(String::clone)) |
| }) |
| .into(); |
| |
| // Delete all lock files, that don't have an associated directory. They must |
| // be some kind of leftover |
| for (lock_file_name, directory_name) in |
| lock_file_to_session_dir.items().into_sorted_stable_ord() |
| { |
| if directory_name.is_none() { |
| let Ok(timestamp) = extract_timestamp_from_session_dir(lock_file_name) else { |
| debug!( |
| "found lock-file with malformed timestamp: {}", |
| crate_directory.join(&lock_file_name).display() |
| ); |
| // Ignore it |
| continue; |
| }; |
| |
| let lock_file_path = crate_directory.join(&*lock_file_name); |
| |
| if is_old_enough_to_be_collected(timestamp) { |
| debug!( |
| "garbage_collect_session_directories() - deleting \ |
| garbage lock file: {}", |
| lock_file_path.display() |
| ); |
| delete_session_dir_lock_file(sess, &lock_file_path); |
| } else { |
| debug!( |
| "garbage_collect_session_directories() - lock file with \ |
| no session dir not old enough to be collected: {}", |
| lock_file_path.display() |
| ); |
| } |
| } |
| } |
| |
| // Filter out `None` directories |
| let lock_file_to_session_dir: UnordMap<String, String> = lock_file_to_session_dir |
| .into_items() |
| .filter_map(|(lock_file_name, directory_name)| directory_name.map(|n| (lock_file_name, n))) |
| .into(); |
| |
| // Delete all session directories that don't have a lock file. |
| for directory_name in session_directories { |
| if !lock_file_to_session_dir.items().any(|(_, dir)| *dir == directory_name) { |
| let path = crate_directory.join(directory_name); |
| if let Err(err) = std_fs::remove_dir_all(&path) { |
| sess.dcx().emit_warn(errors::InvalidGcFailed { path: &path, err }); |
| } |
| } |
| } |
| |
| // Now garbage collect the valid session directories. |
| let deletion_candidates = |
| lock_file_to_session_dir.items().filter_map(|(lock_file_name, directory_name)| { |
| debug!("garbage_collect_session_directories() - inspecting: {}", directory_name); |
| |
| let Ok(timestamp) = extract_timestamp_from_session_dir(directory_name) else { |
| debug!( |
| "found session-dir with malformed timestamp: {}", |
| crate_directory.join(directory_name).display() |
| ); |
| // Ignore it |
| return None; |
| }; |
| |
| if is_finalized(directory_name) { |
| let lock_file_path = crate_directory.join(lock_file_name); |
| match flock::Lock::new( |
| &lock_file_path, |
| false, // don't wait |
| false, // don't create the lock-file |
| true, |
| ) { |
| // get an exclusive lock |
| Ok(lock) => { |
| debug!( |
| "garbage_collect_session_directories() - \ |
| successfully acquired lock" |
| ); |
| debug!( |
| "garbage_collect_session_directories() - adding \ |
| deletion candidate: {}", |
| directory_name |
| ); |
| |
| // Note that we are holding on to the lock |
| return Some(( |
| (timestamp, crate_directory.join(directory_name)), |
| Some(lock), |
| )); |
| } |
| Err(_) => { |
| debug!( |
| "garbage_collect_session_directories() - \ |
| not collecting, still in use" |
| ); |
| } |
| } |
| } else if is_old_enough_to_be_collected(timestamp) { |
| // When cleaning out "-working" session directories, i.e. |
| // session directories that might still be in use by another |
| // compiler instance, we only look a directories that are |
| // at least ten seconds old. This is supposed to reduce the |
| // chance of deleting a directory in the time window where |
| // the process has allocated the directory but has not yet |
| // acquired the file-lock on it. |
| |
| // Try to acquire the directory lock. If we can't, it |
| // means that the owning process is still alive and we |
| // leave this directory alone. |
| let lock_file_path = crate_directory.join(lock_file_name); |
| match flock::Lock::new( |
| &lock_file_path, |
| false, // don't wait |
| false, // don't create the lock-file |
| true, |
| ) { |
| // get an exclusive lock |
| Ok(lock) => { |
| debug!( |
| "garbage_collect_session_directories() - \ |
| successfully acquired lock" |
| ); |
| |
| delete_old(sess, &crate_directory.join(directory_name)); |
| |
| // Let's make it explicit that the file lock is released at this point, |
| // or rather, that we held on to it until here |
| drop(lock); |
| } |
| Err(_) => { |
| debug!( |
| "garbage_collect_session_directories() - \ |
| not collecting, still in use" |
| ); |
| } |
| } |
| } else { |
| debug!( |
| "garbage_collect_session_directories() - not finalized, not \ |
| old enough" |
| ); |
| } |
| None |
| }); |
| let deletion_candidates = deletion_candidates.into(); |
| |
| // Delete all but the most recent of the candidates |
| all_except_most_recent(deletion_candidates).into_items().all(|(path, lock)| { |
| debug!("garbage_collect_session_directories() - deleting `{}`", path.display()); |
| |
| if let Err(err) = std_fs::remove_dir_all(&path) { |
| sess.dcx().emit_warn(errors::FinalizedGcFailed { path: &path, err }); |
| } else { |
| delete_session_dir_lock_file(sess, &lock_file_path(&path)); |
| } |
| |
| // Let's make it explicit that the file lock is released at this point, |
| // or rather, that we held on to it until here |
| drop(lock); |
| true |
| }); |
| |
| Ok(()) |
| } |
| |
| fn delete_old(sess: &Session, path: &Path) { |
| debug!("garbage_collect_session_directories() - deleting `{}`", path.display()); |
| |
| if let Err(err) = std_fs::remove_dir_all(path) { |
| sess.dcx().emit_warn(errors::SessionGcFailed { path, err }); |
| } else { |
| delete_session_dir_lock_file(sess, &lock_file_path(path)); |
| } |
| } |
| |
| fn all_except_most_recent( |
| deletion_candidates: UnordMap<(SystemTime, PathBuf), Option<flock::Lock>>, |
| ) -> UnordMap<PathBuf, Option<flock::Lock>> { |
| let most_recent = deletion_candidates.items().map(|(&(timestamp, _), _)| timestamp).max(); |
| |
| if let Some(most_recent) = most_recent { |
| deletion_candidates |
| .into_items() |
| .filter(|&((timestamp, _), _)| timestamp != most_recent) |
| .map(|((_, path), lock)| (path, lock)) |
| .collect() |
| } else { |
| UnordMap::default() |
| } |
| } |
| |
| fn safe_remove_file(p: &Path) -> io::Result<()> { |
| match std_fs::remove_file(p) { |
| Err(err) if err.kind() == io::ErrorKind::NotFound => Ok(()), |
| result => result, |
| } |
| } |
| |
| // On Windows the compiler would sometimes fail to rename the session directory because |
| // the OS thought something was still being accessed in it. So we retry a few times to give |
| // the OS time to catch up. |
| // See https://github.com/rust-lang/rust/issues/86929. |
| fn rename_path_with_retry(from: &Path, to: &Path, mut retries_left: usize) -> std::io::Result<()> { |
| loop { |
| match std_fs::rename(from, to) { |
| Ok(()) => return Ok(()), |
| Err(e) => { |
| if retries_left > 0 && e.kind() == ErrorKind::PermissionDenied { |
| // Try again after a short waiting period. |
| std::thread::sleep(Duration::from_millis(50)); |
| retries_left -= 1; |
| } else { |
| return Err(e); |
| } |
| } |
| } |
| } |
| } |
