##// END OF EJS Templates
revlog: add a mechanism to verify expected file position before appending...
revlog: add a mechanism to verify expected file position before appending If someone uses `hg debuglocks`, or some non-hg process writes to the .hg directory without respecting the locks, or if the repo's on a networked filesystem, it's possible for the revlog code to write out corrupted data. The form of this corruption can vary depending on what data was written and how that happened. We are in the "networked filesystem" case (though I've had users also do this to themselves with the "`hg debuglocks`" scenario), and most often see this with the changelog. What ends up happening is we produce two items (let's call them rev1 and rev2) in the .i file that have the same linkrev, baserev, and offset into the .d file, while the data in the .d file is appended properly. rev2's compressed_size is accurate for rev2, but when we go to decompress the data in the .d file, we use the offset that's recorded in the index file, which is the same as rev1, and attempt to decompress rev2.compressed_size bytes of rev1's data. This usually does not succeed. :) When using inline data, this also fails, though I haven't investigated why too closely. This shows up as a "patch decode" error. I believe what's happening there is that we're basically ignoring the offset field, getting the data properly, but since baserev != rev, it thinks this is a delta based on rev (instead of a full text) and can't actually apply it as such. For now, I'm going to make this an optional component and default it to entirely off. I may increase the default severity of this in the future, once I've enabled it for my users and we gain more experience with it. Luckily, most of my users have a versioned filesystem and can roll back to before the corruption has been written, it's just a hassle to do so and not everyone knows how (so it's a support burden). Users on other filesystems will not have that luxury, and this can cause them to have a corrupted repository that they are unlikely to know how to resolve, and they'll see this as a data-loss event. Refusing to create the corruption is a much better user experience. This mechanism is not perfect. There may be false-negatives (racy writes that are not detected). There should not be any false-positives (non-racy writes that are detected as such). This is not a mechanism that makes putting a repo on a networked filesystem "safe" or "supported", just *less* likely to cause corruption. Differential Revision: https://phab.mercurial-scm.org/D9952

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lib.rs
121 lines | 3.7 KiB | application/rls-services+xml | RustLexer
// Copyright 2018-2020 Georges Racinet <georges.racinet@octobus.net>
// and Mercurial contributors
//
// This software may be used and distributed according to the terms of the
// GNU General Public License version 2 or any later version.
mod ancestors;
pub mod dagops;
pub mod errors;
pub use ancestors::{AncestorsIterator, LazyAncestors, MissingAncestors};
mod dirstate;
pub mod discovery;
pub mod requirements;
pub mod testing; // unconditionally built, for use from integration tests
pub use dirstate::{
dirs_multiset::{DirsMultiset, DirsMultisetIter},
dirstate_map::DirstateMap,
parsers::{pack_dirstate, parse_dirstate, PARENT_SIZE},
status::{
status, BadMatch, BadType, DirstateStatus, StatusError, StatusOptions,
},
CopyMap, CopyMapIter, DirstateEntry, DirstateParents, EntryState,
StateMap, StateMapIter,
};
pub mod copy_tracing;
mod filepatterns;
pub mod matchers;
pub mod repo;
pub mod revlog;
pub use revlog::*;
pub mod config;
pub mod logging;
pub mod operations;
pub mod revset;
pub mod utils;
use crate::utils::hg_path::{HgPathBuf, HgPathError};
pub use filepatterns::{
parse_pattern_syntax, read_pattern_file, IgnorePattern,
PatternFileWarning, PatternSyntax,
};
use std::collections::HashMap;
use std::fmt;
use twox_hash::RandomXxHashBuilder64;
/// This is a contract between the `micro-timer` crate and us, to expose
/// the `log` crate as `crate::log`.
use log;
pub type LineNumber = usize;
/// Rust's default hasher is too slow because it tries to prevent collision
/// attacks. We are not concerned about those: if an ill-minded person has
/// write access to your repository, you have other issues.
pub type FastHashMap<K, V> = HashMap<K, V, RandomXxHashBuilder64>;
#[derive(Debug, PartialEq)]
pub enum DirstateMapError {
PathNotFound(HgPathBuf),
EmptyPath,
InvalidPath(HgPathError),
}
impl fmt::Display for DirstateMapError {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
match self {
DirstateMapError::PathNotFound(_) => {
f.write_str("expected a value, found none")
}
DirstateMapError::EmptyPath => {
f.write_str("Overflow in dirstate.")
}
DirstateMapError::InvalidPath(path_error) => path_error.fmt(f),
}
}
}
#[derive(Debug, derive_more::From)]
pub enum DirstateError {
Map(DirstateMapError),
Common(errors::HgError),
}
#[derive(Debug, derive_more::From)]
pub enum PatternError {
#[from]
Path(HgPathError),
UnsupportedSyntax(String),
UnsupportedSyntaxInFile(String, String, usize),
TooLong(usize),
#[from]
IO(std::io::Error),
/// Needed a pattern that can be turned into a regex but got one that
/// can't. This should only happen through programmer error.
NonRegexPattern(IgnorePattern),
}
impl fmt::Display for PatternError {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
match self {
PatternError::UnsupportedSyntax(syntax) => {
write!(f, "Unsupported syntax {}", syntax)
}
PatternError::UnsupportedSyntaxInFile(syntax, file_path, line) => {
write!(
f,
"{}:{}: unsupported syntax {}",
file_path, line, syntax
)
}
PatternError::TooLong(size) => {
write!(f, "matcher pattern is too long ({} bytes)", size)
}
PatternError::IO(error) => error.fmt(f),
PatternError::Path(error) => error.fmt(f),
PatternError::NonRegexPattern(pattern) => {
write!(f, "'{:?}' cannot be turned into a regex", pattern)
}
}
}
}