Mercurial > hg
view rust/hg-core/src/dirstate_tree/status.rs @ 47349:7138c863d0a1
dirstate-v2: Skip readdir in status based on directory mtime
When calling `read_dir` during `status` and the directory is found to be
eligible for caching (see code comments), write the directory’s mtime to the
dirstate. The presence of a directory mtime in the dirstate is meaningful
and indicates eligibility.
When an eligible directory mtime is found in the dirstate and `stat()` shows
that the mtime has not changed, `status` can skip calling `read_dir` again
and instead rely on the names of child nodes in the dirstate tree.
The `tempfile` crate is used to create a temporary file in order to use its
modification time as "current time" with the same truncation as other files
and directories would have in their own modification time.
Differential Revision: https://phab.mercurial-scm.org/D10826
author | Simon Sapin <simon.sapin@octobus.net> |
---|---|
date | Fri, 28 May 2021 11:48:59 +0200 |
parents | 73ddcedeaadf |
children | 04d1f17f49e7 |
line wrap: on
line source
use crate::dirstate::status::IgnoreFnType; use crate::dirstate_tree::dirstate_map::BorrowedPath; use crate::dirstate_tree::dirstate_map::ChildNodesRef; use crate::dirstate_tree::dirstate_map::DirstateMap; use crate::dirstate_tree::dirstate_map::NodeData; use crate::dirstate_tree::dirstate_map::NodeRef; use crate::dirstate_tree::on_disk::DirstateV2ParseError; use crate::dirstate_tree::on_disk::Timestamp; use crate::dirstate_tree::path_with_basename::WithBasename; use crate::matchers::get_ignore_function; use crate::matchers::Matcher; use crate::utils::files::get_bytes_from_os_string; use crate::utils::files::get_path_from_bytes; use crate::utils::hg_path::HgPath; use crate::BadMatch; use crate::DirstateStatus; use crate::EntryState; use crate::HgPathBuf; use crate::PatternFileWarning; use crate::StatusError; use crate::StatusOptions; use micro_timer::timed; use rayon::prelude::*; use std::borrow::Cow; use std::io; use std::path::Path; use std::path::PathBuf; use std::sync::Mutex; use std::time::SystemTime; /// Returns the status of the working directory compared to its parent /// changeset. /// /// This algorithm is based on traversing the filesystem tree (`fs` in function /// and variable names) and dirstate tree at the same time. The core of this /// traversal is the recursive `traverse_fs_directory_and_dirstate` function /// and its use of `itertools::merge_join_by`. When reaching a path that only /// exists in one of the two trees, depending on information requested by /// `options` we may need to traverse the remaining subtree. #[timed] pub fn status<'tree, 'on_disk: 'tree>( dmap: &'tree mut DirstateMap<'on_disk>, matcher: &(dyn Matcher + Sync), root_dir: PathBuf, ignore_files: Vec<PathBuf>, options: StatusOptions, ) -> Result<(DirstateStatus<'on_disk>, Vec<PatternFileWarning>), StatusError> { let (ignore_fn, warnings): (IgnoreFnType, _) = if options.list_ignored || options.list_unknown { get_ignore_function(ignore_files, &root_dir)? } else { (Box::new(|&_| true), vec![]) }; let common = StatusCommon { dmap, options, matcher, ignore_fn, outcome: Default::default(), cached_directory_mtimes_to_add: Default::default(), filesystem_time_at_status_start: filesystem_now(&root_dir).ok(), }; let is_at_repo_root = true; let hg_path = &BorrowedPath::OnDisk(HgPath::new("")); let has_ignored_ancestor = false; let root_cached_mtime = None; let root_dir_metadata = None; // If the path we have for the repository root is a symlink, do follow it. // (As opposed to symlinks within the working directory which are not // followed, using `std::fs::symlink_metadata`.) common.traverse_fs_directory_and_dirstate( has_ignored_ancestor, dmap.root.as_ref(), hg_path, &root_dir, root_dir_metadata, root_cached_mtime, is_at_repo_root, )?; let outcome = common.outcome.into_inner().unwrap(); let to_add = common.cached_directory_mtimes_to_add.into_inner().unwrap(); for (path, mtime) in &to_add { let node = DirstateMap::get_or_insert_node( dmap.on_disk, &mut dmap.root, path, WithBasename::to_cow_owned, |_| {}, )?; match &node.data { NodeData::Entry(_) => {} // Don’t overwrite an entry NodeData::CachedDirectory { .. } | NodeData::None => { node.data = NodeData::CachedDirectory { mtime: *mtime } } } } Ok((outcome, warnings)) } /// Bag of random things needed by various parts of the algorithm. Reduces the /// number of parameters passed to functions. struct StatusCommon<'a, 'tree, 'on_disk: 'tree> { dmap: &'tree DirstateMap<'on_disk>, options: StatusOptions, matcher: &'a (dyn Matcher + Sync), ignore_fn: IgnoreFnType<'a>, outcome: Mutex<DirstateStatus<'on_disk>>, cached_directory_mtimes_to_add: Mutex<Vec<(Cow<'on_disk, HgPath>, Timestamp)>>, /// The current time at the start of the `status()` algorithm, as measured /// and possibly truncated by the filesystem. filesystem_time_at_status_start: Option<SystemTime>, } impl<'a, 'tree, 'on_disk> StatusCommon<'a, 'tree, 'on_disk> { fn read_dir( &self, hg_path: &HgPath, fs_path: &Path, is_at_repo_root: bool, ) -> Result<Vec<DirEntry>, ()> { DirEntry::read_dir(fs_path, is_at_repo_root) .map_err(|error| self.io_error(error, hg_path)) } fn io_error(&self, error: std::io::Error, hg_path: &HgPath) { let errno = error.raw_os_error().expect("expected real OS error"); self.outcome .lock() .unwrap() .bad .push((hg_path.to_owned().into(), BadMatch::OsError(errno))) } /// If this returns true, we can get accurate results by only using /// `symlink_metadata` for child nodes that exist in the dirstate and don’t /// need to call `read_dir`. fn can_skip_fs_readdir( &self, directory_metadata: Option<&std::fs::Metadata>, cached_directory_mtime: Option<&Timestamp>, ) -> bool { if !self.options.list_unknown && !self.options.list_ignored { // All states that we care about listing have corresponding // dirstate entries. // This happens for example with `hg status -mard`. return true; } if let Some(cached_mtime) = cached_directory_mtime { // The dirstate contains a cached mtime for this directory, set by // a previous run of the `status` algorithm which found this // directory eligible for `read_dir` caching. if let Some(meta) = directory_metadata { if let Ok(current_mtime) = meta.modified() { if current_mtime == cached_mtime.into() { // The mtime of that directory has not changed since // then, which means that the // results of `read_dir` should also // be unchanged. return true; } } } } false } /// Returns whether the filesystem directory was found to have any entry /// that does not have a corresponding dirstate tree node. fn traverse_fs_directory_and_dirstate( &self, has_ignored_ancestor: bool, dirstate_nodes: ChildNodesRef<'tree, 'on_disk>, directory_hg_path: &BorrowedPath<'tree, 'on_disk>, directory_fs_path: &Path, directory_metadata: Option<&std::fs::Metadata>, cached_directory_mtime: Option<&Timestamp>, is_at_repo_root: bool, ) -> Result<bool, DirstateV2ParseError> { if self.can_skip_fs_readdir(directory_metadata, cached_directory_mtime) { dirstate_nodes .par_iter() .map(|dirstate_node| { let fs_path = directory_fs_path.join(get_path_from_bytes( dirstate_node.base_name(self.dmap.on_disk)?.as_bytes(), )); match std::fs::symlink_metadata(&fs_path) { Ok(fs_metadata) => self.traverse_fs_and_dirstate( &fs_path, &fs_metadata, dirstate_node, has_ignored_ancestor, ), Err(e) if e.kind() == std::io::ErrorKind::NotFound => { self.traverse_dirstate_only(dirstate_node) } Err(error) => { let hg_path = dirstate_node.full_path(self.dmap.on_disk)?; Ok(self.io_error(error, hg_path)) } } }) .collect::<Result<_, _>>()?; // Conservatively don’t let the caller assume that there aren’t // any, since we don’t know. let directory_has_any_fs_only_entry = true; return Ok(directory_has_any_fs_only_entry); } let mut fs_entries = if let Ok(entries) = self.read_dir( directory_hg_path, directory_fs_path, is_at_repo_root, ) { entries } else { // Treat an unreadable directory (typically because of insufficient // permissions) like an empty directory. `self.read_dir` has // already called `self.io_error` so a warning will be emitted. Vec::new() }; // `merge_join_by` requires both its input iterators to be sorted: let dirstate_nodes = dirstate_nodes.sorted(); // `sort_unstable_by_key` doesn’t allow keys borrowing from the value: // https://github.com/rust-lang/rust/issues/34162 fs_entries.sort_unstable_by(|e1, e2| e1.base_name.cmp(&e2.base_name)); // Propagate here any error that would happen inside the comparison // callback below for dirstate_node in &dirstate_nodes { dirstate_node.base_name(self.dmap.on_disk)?; } itertools::merge_join_by( dirstate_nodes, &fs_entries, |dirstate_node, fs_entry| { // This `unwrap` never panics because we already propagated // those errors above dirstate_node .base_name(self.dmap.on_disk) .unwrap() .cmp(&fs_entry.base_name) }, ) .par_bridge() .map(|pair| { use itertools::EitherOrBoth::*; let is_fs_only = pair.is_right(); match pair { Both(dirstate_node, fs_entry) => self .traverse_fs_and_dirstate( &fs_entry.full_path, &fs_entry.metadata, dirstate_node, has_ignored_ancestor, )?, Left(dirstate_node) => { self.traverse_dirstate_only(dirstate_node)? } Right(fs_entry) => self.traverse_fs_only( has_ignored_ancestor, directory_hg_path, fs_entry, ), } Ok(is_fs_only) }) .try_reduce(|| false, |a, b| Ok(a || b)) } fn traverse_fs_and_dirstate( &self, fs_path: &Path, fs_metadata: &std::fs::Metadata, dirstate_node: NodeRef<'tree, 'on_disk>, has_ignored_ancestor: bool, ) -> Result<(), DirstateV2ParseError> { let hg_path = &dirstate_node.full_path_borrowed(self.dmap.on_disk)?; let file_type = fs_metadata.file_type(); let file_or_symlink = file_type.is_file() || file_type.is_symlink(); if !file_or_symlink { // If we previously had a file here, it was removed (with // `hg rm` or similar) or deleted before it could be // replaced by a directory or something else. self.mark_removed_or_deleted_if_file( &hg_path, dirstate_node.state()?, ); } if file_type.is_dir() { if self.options.collect_traversed_dirs { self.outcome .lock() .unwrap() .traversed .push(hg_path.detach_from_tree()) } let is_ignored = has_ignored_ancestor || (self.ignore_fn)(hg_path); let is_at_repo_root = false; let directory_has_any_fs_only_entry = self .traverse_fs_directory_and_dirstate( is_ignored, dirstate_node.children(self.dmap.on_disk)?, hg_path, fs_path, Some(fs_metadata), dirstate_node.cached_directory_mtime(), is_at_repo_root, )?; self.maybe_save_directory_mtime( directory_has_any_fs_only_entry, fs_metadata, dirstate_node, )? } else { if file_or_symlink && self.matcher.matches(hg_path) { if let Some(state) = dirstate_node.state()? { match state { EntryState::Added => self .outcome .lock() .unwrap() .added .push(hg_path.detach_from_tree()), EntryState::Removed => self .outcome .lock() .unwrap() .removed .push(hg_path.detach_from_tree()), EntryState::Merged => self .outcome .lock() .unwrap() .modified .push(hg_path.detach_from_tree()), EntryState::Normal => self .handle_normal_file(&dirstate_node, fs_metadata)?, // This variant is not used in DirstateMap // nodes EntryState::Unknown => unreachable!(), } } else { // `node.entry.is_none()` indicates a "directory" // node, but the filesystem has a file self.mark_unknown_or_ignored(has_ignored_ancestor, hg_path) } } for child_node in dirstate_node.children(self.dmap.on_disk)?.iter() { self.traverse_dirstate_only(child_node)? } } Ok(()) } fn maybe_save_directory_mtime( &self, directory_has_any_fs_only_entry: bool, directory_metadata: &std::fs::Metadata, dirstate_node: NodeRef<'tree, 'on_disk>, ) -> Result<(), DirstateV2ParseError> { if !directory_has_any_fs_only_entry { // All filesystem directory entries from `read_dir` have a // corresponding node in the dirstate, so we can reconstitute the // names of those entries without calling `read_dir` again. if let (Some(status_start), Ok(directory_mtime)) = ( &self.filesystem_time_at_status_start, directory_metadata.modified(), ) { // Although the Rust standard library’s `SystemTime` type // has nanosecond precision, the times reported for a // directory’s (or file’s) modified time may have lower // resolution based on the filesystem (for example ext3 // only stores integer seconds), kernel (see // https://stackoverflow.com/a/14393315/1162888), etc. if &directory_mtime >= status_start { // The directory was modified too recently, don’t cache its // `read_dir` results. // // A timeline like this is possible: // // 1. A change to this directory (direct child was // added or removed) cause its mtime to be set // (possibly truncated) to `directory_mtime` // 2. This `status` algorithm calls `read_dir` // 3. An other change is made to the same directory is // made so that calling `read_dir` agin would give // different results, but soon enough after 1. that // the mtime stays the same // // On a system where the time resolution poor, this // scenario is not unlikely if all three steps are caused // by the same script. } else { // We’ve observed (through `status_start`) that time has // “progressed” since `directory_mtime`, so any further // change to this directory is extremely likely to cause a // different mtime. // // Having the same mtime again is not entirely impossible // since the system clock is not monotonous. It could jump // backward to some point before `directory_mtime`, then a // directory change could potentially happen during exactly // the wrong tick. // // We deem this scenario (unlike the previous one) to be // unlikely enough in practice. let timestamp = directory_mtime.into(); let cached = dirstate_node.cached_directory_mtime(); if cached != Some(×tamp) { let hg_path = dirstate_node .full_path_borrowed(self.dmap.on_disk)? .detach_from_tree(); self.cached_directory_mtimes_to_add .lock() .unwrap() .push((hg_path, timestamp)) } } } } Ok(()) } /// A file with `EntryState::Normal` in the dirstate was found in the /// filesystem fn handle_normal_file( &self, dirstate_node: &NodeRef<'tree, 'on_disk>, fs_metadata: &std::fs::Metadata, ) -> Result<(), DirstateV2ParseError> { // Keep the low 31 bits fn truncate_u64(value: u64) -> i32 { (value & 0x7FFF_FFFF) as i32 } fn truncate_i64(value: i64) -> i32 { (value & 0x7FFF_FFFF) as i32 } let entry = dirstate_node .entry()? .expect("handle_normal_file called with entry-less node"); let hg_path = &dirstate_node.full_path_borrowed(self.dmap.on_disk)?; let mode_changed = || self.options.check_exec && entry.mode_changed(fs_metadata); let size_changed = entry.size != truncate_u64(fs_metadata.len()); if entry.size >= 0 && size_changed && fs_metadata.file_type().is_symlink() { // issue6456: Size returned may be longer due to encryption // on EXT-4 fscrypt. TODO maybe only do it on EXT4? self.outcome .lock() .unwrap() .unsure .push(hg_path.detach_from_tree()) } else if dirstate_node.has_copy_source() || entry.is_from_other_parent() || (entry.size >= 0 && (size_changed || mode_changed())) { self.outcome .lock() .unwrap() .modified .push(hg_path.detach_from_tree()) } else { let mtime = mtime_seconds(fs_metadata); if truncate_i64(mtime) != entry.mtime || mtime == self.options.last_normal_time { self.outcome .lock() .unwrap() .unsure .push(hg_path.detach_from_tree()) } else if self.options.list_clean { self.outcome .lock() .unwrap() .clean .push(hg_path.detach_from_tree()) } } Ok(()) } /// A node in the dirstate tree has no corresponding filesystem entry fn traverse_dirstate_only( &self, dirstate_node: NodeRef<'tree, 'on_disk>, ) -> Result<(), DirstateV2ParseError> { self.mark_removed_or_deleted_if_file( &dirstate_node.full_path_borrowed(self.dmap.on_disk)?, dirstate_node.state()?, ); dirstate_node .children(self.dmap.on_disk)? .par_iter() .map(|child_node| self.traverse_dirstate_only(child_node)) .collect() } /// A node in the dirstate tree has no corresponding *file* on the /// filesystem /// /// Does nothing on a "directory" node fn mark_removed_or_deleted_if_file( &self, hg_path: &BorrowedPath<'tree, 'on_disk>, dirstate_node_state: Option<EntryState>, ) { if let Some(state) = dirstate_node_state { if self.matcher.matches(hg_path) { if let EntryState::Removed = state { self.outcome .lock() .unwrap() .removed .push(hg_path.detach_from_tree()) } else { self.outcome .lock() .unwrap() .deleted .push(hg_path.detach_from_tree()) } } } } /// Something in the filesystem has no corresponding dirstate node fn traverse_fs_only( &self, has_ignored_ancestor: bool, directory_hg_path: &HgPath, fs_entry: &DirEntry, ) { let hg_path = directory_hg_path.join(&fs_entry.base_name); let file_type = fs_entry.metadata.file_type(); let file_or_symlink = file_type.is_file() || file_type.is_symlink(); if file_type.is_dir() { let is_ignored = has_ignored_ancestor || (self.ignore_fn)(&hg_path); let traverse_children = if is_ignored { // Descendants of an ignored directory are all ignored self.options.list_ignored } else { // Descendants of an unknown directory may be either unknown or // ignored self.options.list_unknown || self.options.list_ignored }; if traverse_children { let is_at_repo_root = false; if let Ok(children_fs_entries) = self.read_dir( &hg_path, &fs_entry.full_path, is_at_repo_root, ) { children_fs_entries.par_iter().for_each(|child_fs_entry| { self.traverse_fs_only( is_ignored, &hg_path, child_fs_entry, ) }) } } if self.options.collect_traversed_dirs { self.outcome.lock().unwrap().traversed.push(hg_path.into()) } } else if file_or_symlink && self.matcher.matches(&hg_path) { self.mark_unknown_or_ignored( has_ignored_ancestor, &BorrowedPath::InMemory(&hg_path), ) } } fn mark_unknown_or_ignored( &self, has_ignored_ancestor: bool, hg_path: &BorrowedPath<'_, 'on_disk>, ) { let is_ignored = has_ignored_ancestor || (self.ignore_fn)(&hg_path); if is_ignored { if self.options.list_ignored { self.outcome .lock() .unwrap() .ignored .push(hg_path.detach_from_tree()) } } else { if self.options.list_unknown { self.outcome .lock() .unwrap() .unknown .push(hg_path.detach_from_tree()) } } } } #[cfg(unix)] // TODO fn mtime_seconds(metadata: &std::fs::Metadata) -> i64 { // Going through `Metadata::modified()` would be portable, but would take // care to construct a `SystemTime` value with sub-second precision just // for us to throw that away here. use std::os::unix::fs::MetadataExt; metadata.mtime() } struct DirEntry { base_name: HgPathBuf, full_path: PathBuf, metadata: std::fs::Metadata, } impl DirEntry { /// Returns **unsorted** entries in the given directory, with name and /// metadata. /// /// If a `.hg` sub-directory is encountered: /// /// * At the repository root, ignore that sub-directory /// * Elsewhere, we’re listing the content of a sub-repo. Return an empty /// list instead. fn read_dir(path: &Path, is_at_repo_root: bool) -> io::Result<Vec<Self>> { let mut results = Vec::new(); for entry in path.read_dir()? { let entry = entry?; let metadata = entry.metadata()?; let name = get_bytes_from_os_string(entry.file_name()); // FIXME don't do this when cached if name == b".hg" { if is_at_repo_root { // Skip the repo’s own .hg (might be a symlink) continue; } else if metadata.is_dir() { // A .hg sub-directory at another location means a subrepo, // skip it entirely. return Ok(Vec::new()); } } results.push(DirEntry { base_name: name.into(), full_path: entry.path(), metadata, }) } Ok(results) } } /// Return the `mtime` of a temporary file newly-created in the `.hg` directory /// of the give repository. /// /// This is similar to `SystemTime::now()`, with the result truncated to the /// same time resolution as other files’ modification times. Using `.hg` /// instead of the system’s default temporary directory (such as `/tmp`) makes /// it more likely the temporary file is in the same disk partition as contents /// of the working directory, which can matter since different filesystems may /// store timestamps with different resolutions. /// /// This may fail, typically if we lack write permissions. In that case we /// should continue the `status()` algoritm anyway and consider the current /// date/time to be unknown. fn filesystem_now(repo_root: &Path) -> Result<SystemTime, io::Error> { tempfile::tempfile_in(repo_root.join(".hg"))? .metadata()? .modified() }