mod file_attr; mod inode_tracker; mod inodes; #[cfg(feature = "fuse")] pub mod fuse; #[cfg(test)] mod tests; use crate::pathinfoservice::PathInfoService; use fuse_backend_rs::api::filesystem::{Context, FileSystem, FsOptions, ROOT_ID}; use futures::StreamExt; use nix_compat::store_path::StorePath; use parking_lot::RwLock; use std::{ collections::HashMap, io, str::FromStr, sync::atomic::AtomicU64, sync::{atomic::Ordering, Arc}, time::Duration, }; use tokio::{ io::{AsyncBufReadExt, AsyncSeekExt}, sync::mpsc, }; use tracing::{debug, info_span, warn}; use tvix_castore::{ blobservice::{BlobReader, BlobService}, directoryservice::DirectoryService, proto::{node::Node, NamedNode}, B3Digest, Error, }; use self::{ file_attr::{gen_file_attr, ROOT_FILE_ATTR}, inode_tracker::InodeTracker, inodes::{DirectoryInodeData, InodeData}, }; /// This implements a read-only FUSE filesystem for a tvix-store /// with the passed [BlobService], [DirectoryService] and [PathInfoService]. /// /// We don't allow listing on the root mountpoint (inode 0). /// In the future, this might be made configurable once a listing method is /// added to [self.path_info_service], and then show all store paths in that /// store. /// /// Linux uses inodes in filesystems. When implementing FUSE, most calls are /// *for* a given inode. /// /// This means, we need to have a stable mapping of inode numbers to the /// corresponding store nodes. /// /// We internally delegate all inode allocation and state keeping to the /// inode tracker, and store the currently "explored" store paths together with /// root inode of the root. /// /// There's some places where inodes are allocated / data inserted into /// the inode tracker, if not allocated before already: /// - Processing a `lookup` request, either in the mount root, or somewhere /// deeper /// - Processing a `readdir` request /// /// Things pointing to the same contents get the same inodes, irrespective of /// their own location. /// This means: /// - Symlinks with the same target will get the same inode. /// - Regular/executable files with the same contents will get the same inode /// - Directories with the same contents will get the same inode. /// /// Due to the above being valid across the whole store, and considering the /// merkle structure is a DAG, not a tree, this also means we can't do "bucketed /// allocation", aka reserve Directory.size inodes for each PathInfo. pub struct TvixStoreFs { blob_service: Arc, directory_service: Arc, path_info_service: Arc, /// Whether to (try) listing elements in the root. list_root: bool, /// This maps a given StorePath to the inode we allocated for the root inode. store_paths: RwLock>, /// This keeps track of inodes and data alongside them. inode_tracker: RwLock, /// This holds all open file handles file_handles: RwLock>>>>, next_file_handle: AtomicU64, tokio_handle: tokio::runtime::Handle, } impl TvixStoreFs { pub fn new( blob_service: Arc, directory_service: Arc, path_info_service: Arc, list_root: bool, ) -> Self { Self { blob_service, directory_service, path_info_service, list_root, store_paths: RwLock::new(HashMap::default()), inode_tracker: RwLock::new(Default::default()), file_handles: RwLock::new(Default::default()), next_file_handle: AtomicU64::new(1), tokio_handle: tokio::runtime::Handle::current(), } } /// This will turn a lookup request for [std::ffi::OsStr] in the root to /// a ino and [InodeData]. /// It will peek in [self.store_paths], and then either look it up from /// [self.inode_tracker], /// or otherwise fetch from [self.path_info_service], and then insert into /// [self.inode_tracker]. fn name_in_root_to_ino_and_data( &self, name: &std::ffi::CStr, ) -> Result)>, Error> { // parse the name into a [StorePath]. let store_path = if let Some(name) = name.to_str().ok() { match StorePath::from_str(name) { Ok(store_path) => store_path, Err(e) => { debug!(e=?e, "unable to parse as store path"); // This is not an error, but a "ENOENT", as someone can stat // a file inside the root that's no valid store path return Ok(None); } } } else { debug!("{name:?} is not a valid utf-8 string"); // same here. return Ok(None); }; let ino = { // This extra scope makes sure we drop the read lock // immediately after reading, to prevent deadlocks. let store_paths = self.store_paths.read(); store_paths.get(&store_path).cloned() }; if let Some(ino) = ino { // If we already have that store path, lookup the inode from // self.store_paths and then get the data from [self.inode_tracker], // which in the case of a [InodeData::Directory] will be fully // populated. Ok(Some(( ino, self.inode_tracker.read().get(ino).expect("must exist"), ))) } else { // If we don't have it, look it up in PathInfoService. let path_info_service = self.path_info_service.clone(); let task = self .tokio_handle .spawn(async move { path_info_service.get(store_path.digest).await }); match self.tokio_handle.block_on(task).unwrap()? { // the pathinfo doesn't exist, so the file doesn't exist. None => Ok(None), Some(path_info) => { // The pathinfo does exist, so there must be a root node let root_node = path_info.node.unwrap().node.unwrap(); // The name must match what's passed in the lookup, otherwise we return nothing. if root_node.get_name() != store_path.to_string().as_bytes() { return Ok(None); } // Let's check if someone else beat us to updating the inode tracker and // store_paths map. let mut store_paths = self.store_paths.write(); if let Some(ino) = store_paths.get(&store_path).cloned() { return Ok(Some(( ino, self.inode_tracker.read().get(ino).expect("must exist"), ))); } // insert the (sparse) inode data and register in // self.store_paths. // FUTUREWORK: change put to return the data after // inserting, so we don't need to lookup a second // time? let (ino, inode) = { let mut inode_tracker = self.inode_tracker.write(); let ino = inode_tracker.put((&root_node).into()); (ino, inode_tracker.get(ino).unwrap()) }; store_paths.insert(store_path, ino); Ok(Some((ino, inode))) } } } } /// This will lookup a directory by digest, and will turn it into a /// [InodeData::Directory(DirectoryInodeData::Populated(..))]. /// This is both used to initially insert the root node of a store path, /// as well as when looking up an intermediate DirectoryNode. fn fetch_directory_inode_data(&self, directory_digest: &B3Digest) -> Result { let directory_service = self.directory_service.clone(); let directory_digest_clone = directory_digest.clone(); let task = self .tokio_handle .spawn(async move { directory_service.get(&directory_digest_clone).await }); match self.tokio_handle.block_on(task).unwrap() { Err(e) => { warn!(e = e.to_string(), directory.digest=%directory_digest, "failed to get directory"); Err(e) } // If the Directory can't be found, this is a hole, bail out. Ok(None) => { tracing::error!(directory.digest=%directory_digest, "directory not found in directory service"); Err(Error::StorageError(format!( "directory {} not found", directory_digest ))) } Ok(Some(directory)) => Ok(directory.into()), } } } impl FileSystem for TvixStoreFs { type Inode = u64; type Handle = u64; fn init(&self, _capable: FsOptions) -> io::Result { Ok(FsOptions::empty()) } #[tracing::instrument(skip_all, fields(rq.inode = inode))] fn getattr( &self, _ctx: &Context, inode: Self::Inode, _handle: Option, ) -> io::Result<(libc::stat64, Duration)> { if inode == ROOT_ID { return Ok((ROOT_FILE_ATTR.into(), Duration::MAX)); } match self.inode_tracker.read().get(inode) { None => return Err(io::Error::from_raw_os_error(libc::ENOENT)), Some(node) => { debug!(node = ?node, "found node"); Ok((gen_file_attr(&node, inode).into(), Duration::MAX)) } } } #[tracing::instrument(skip_all, fields(rq.parent_inode = parent, rq.name = ?name))] fn lookup( &self, _ctx: &Context, parent: Self::Inode, name: &std::ffi::CStr, ) -> io::Result { debug!("lookup"); // This goes from a parent inode to a node. // - If the parent is [ROOT_ID], we need to check // [self.store_paths] (fetching from PathInfoService if needed) // - Otherwise, lookup the parent in [self.inode_tracker] (which must be // a [InodeData::Directory]), and find the child with that name. if parent == ROOT_ID { return match self.name_in_root_to_ino_and_data(name) { Err(e) => { warn!("{}", e); Err(io::Error::from_raw_os_error(libc::ENOENT)) } Ok(None) => Err(io::Error::from_raw_os_error(libc::ENOENT)), Ok(Some((ino, inode_data))) => { debug!(inode_data=?&inode_data, ino=ino, "Some"); Ok(fuse_backend_rs::api::filesystem::Entry { inode: ino, attr: gen_file_attr(&inode_data, ino).into(), attr_timeout: Duration::MAX, entry_timeout: Duration::MAX, ..Default::default() }) } }; } // This is the "lookup for "a" inside inode 42. // We already know that inode 42 must be a directory. // It might not be populated yet, so if it isn't, we do (by // fetching from [self.directory_service]), and save the result in // [self.inode_tracker]. // Now it for sure is populated, so we search for that name in the // list of children and return the FileAttrs. // TODO: Reduce the critical section of this write lock. let mut inode_tracker = self.inode_tracker.write(); let parent_data = inode_tracker.get(parent).unwrap(); let parent_data = match *parent_data { InodeData::Regular(..) | InodeData::Symlink(_) => { // if the parent inode was not a directory, this doesn't make sense return Err(io::Error::from_raw_os_error(libc::ENOTDIR)); } InodeData::Directory(DirectoryInodeData::Sparse(ref parent_digest, _)) => { match self.fetch_directory_inode_data(parent_digest) { Ok(new_data) => { // update data in [self.inode_tracker] with populated variant. // FUTUREWORK: change put to return the data after // inserting, so we don't need to lookup a second // time? let ino = inode_tracker.put(new_data); inode_tracker.get(ino).unwrap() } Err(_e) => { return Err(io::Error::from_raw_os_error(libc::EIO)); } } } InodeData::Directory(DirectoryInodeData::Populated(..)) => parent_data, }; // now parent_data can only be a [InodeData::Directory(DirectoryInodeData::Populated(..))]. let (parent_digest, children) = if let InodeData::Directory( DirectoryInodeData::Populated(ref parent_digest, ref children), ) = *parent_data { (parent_digest, children) } else { panic!("unexpected type") }; let span = info_span!("lookup", directory.digest = %parent_digest); let _enter = span.enter(); // in the children, find the one with the desired name. if let Some((child_ino, _)) = children.iter().find(|e| e.1.get_name() == name.to_bytes()) { // lookup the child [InodeData] in [self.inode_tracker]. // We know the inodes for children have already been allocated. let child_inode_data = inode_tracker.get(*child_ino).unwrap(); // Reply with the file attributes for the child. // For child directories, we still have all data we need to reply. Ok(fuse_backend_rs::api::filesystem::Entry { inode: *child_ino, attr: gen_file_attr(&child_inode_data, *child_ino).into(), attr_timeout: Duration::MAX, entry_timeout: Duration::MAX, ..Default::default() }) } else { // Child not found, return ENOENT. Err(io::Error::from_raw_os_error(libc::ENOENT)) } } // TODO: readdirplus? #[tracing::instrument(skip_all, fields(rq.inode = inode, rq.offset = offset))] fn readdir( &self, _ctx: &Context, inode: Self::Inode, _handle: Self::Handle, _size: u32, offset: u64, add_entry: &mut dyn FnMut(fuse_backend_rs::api::filesystem::DirEntry) -> io::Result, ) -> io::Result<()> { debug!("readdir"); if inode == ROOT_ID { if !self.list_root { return Err(io::Error::from_raw_os_error(libc::EPERM)); // same error code as ipfs/kubo } else { let path_info_service = self.path_info_service.clone(); let (tx, mut rx) = mpsc::channel(16); // This task will run in the background immediately and will exit // after the stream ends or if we no longer want any more entries. self.tokio_handle.spawn(async move { let mut stream = path_info_service.list().skip(offset as usize).enumerate(); while let Some(path_info) = stream.next().await { if tx.send(path_info).await.is_err() { // If we get a send error, it means the sync code // doesn't want any more entries. break; } } }); while let Some((i, path_info)) = rx.blocking_recv() { let path_info = match path_info { Err(e) => { warn!("failed to retrieve pathinfo: {}", e); return Err(io::Error::from_raw_os_error(libc::EPERM)); } Ok(path_info) => path_info, }; // We know the root node exists and the store_path can be parsed because clients MUST validate. let root_node = path_info.node.unwrap().node.unwrap(); let store_path = StorePath::from_bytes(root_node.get_name()).unwrap(); let ino = { // This extra scope makes sure we drop the read lock // immediately after reading, to prevent deadlocks. let store_paths = self.store_paths.read(); store_paths.get(&store_path).cloned() }; let ino = match ino { Some(ino) => ino, None => { // insert the (sparse) inode data and register in // self.store_paths. let ino = self.inode_tracker.write().put((&root_node).into()); self.store_paths.write().insert(store_path.clone(), ino); ino } }; let ty = match root_node { Node::Directory(_) => libc::S_IFDIR, Node::File(_) => libc::S_IFREG, Node::Symlink(_) => libc::S_IFLNK, }; let written = add_entry(fuse_backend_rs::api::filesystem::DirEntry { ino, offset: offset + i as u64 + 1, type_: ty, name: store_path.to_string().as_bytes(), })?; // If the buffer is full, add_entry will return `Ok(0)`. if written == 0 { break; } } return Ok(()); } } // lookup the inode data. let mut inode_tracker = self.inode_tracker.write(); let dir_inode_data = inode_tracker.get(inode).unwrap(); let dir_inode_data = match *dir_inode_data { InodeData::Regular(..) | InodeData::Symlink(..) => { warn!("Not a directory"); return Err(io::Error::from_raw_os_error(libc::ENOTDIR)); } InodeData::Directory(DirectoryInodeData::Sparse(ref directory_digest, _)) => { match self.fetch_directory_inode_data(directory_digest) { Ok(new_data) => { // update data in [self.inode_tracker] with populated variant. // FUTUREWORK: change put to return the data after // inserting, so we don't need to lookup a second // time? let ino = inode_tracker.put(new_data.clone()); inode_tracker.get(ino).unwrap() } Err(_e) => { return Err(io::Error::from_raw_os_error(libc::EIO)); } } } InodeData::Directory(DirectoryInodeData::Populated(..)) => dir_inode_data, }; // now parent_data can only be InodeData::Directory(DirectoryInodeData::Populated(..)) if let InodeData::Directory(DirectoryInodeData::Populated(ref _digest, ref children)) = *dir_inode_data { for (i, (ino, child_node)) in children.iter().skip(offset as usize).enumerate() { // the second parameter will become the "offset" parameter on the next call. let written = add_entry(fuse_backend_rs::api::filesystem::DirEntry { ino: *ino, offset: offset + i as u64 + 1, type_: match child_node { Node::Directory(_) => libc::S_IFDIR, Node::File(_) => libc::S_IFREG, Node::Symlink(_) => libc::S_IFLNK, }, name: child_node.get_name(), })?; // If the buffer is full, add_entry will return `Ok(0)`. if written == 0 { break; } } } else { panic!("unexpected type") } Ok(()) } #[tracing::instrument(skip_all, fields(rq.inode = inode))] fn open( &self, _ctx: &Context, inode: Self::Inode, _flags: u32, _fuse_flags: u32, ) -> io::Result<( Option, fuse_backend_rs::api::filesystem::OpenOptions, )> { if inode == ROOT_ID { return Err(io::Error::from_raw_os_error(libc::ENOSYS)); } // lookup the inode match *self.inode_tracker.read().get(inode).unwrap() { // read is invalid on non-files. InodeData::Directory(..) | InodeData::Symlink(_) => { warn!("is directory"); return Err(io::Error::from_raw_os_error(libc::EISDIR)); } InodeData::Regular(ref blob_digest, _blob_size, _) => { let span = info_span!("read", blob.digest = %blob_digest); let _enter = span.enter(); let blob_service = self.blob_service.clone(); let blob_digest = blob_digest.clone(); let task = self .tokio_handle .spawn(async move { blob_service.open_read(&blob_digest).await }); let blob_reader = self.tokio_handle.block_on(task).unwrap(); match blob_reader { Ok(None) => { warn!("blob not found"); return Err(io::Error::from_raw_os_error(libc::EIO)); } Err(e) => { warn!(e=?e, "error opening blob"); return Err(io::Error::from_raw_os_error(libc::EIO)); } Ok(Some(blob_reader)) => { // get a new file handle // TODO: this will overflow after 2**64 operations, // which is fine for now. // See https://cl.tvl.fyi/c/depot/+/8834/comment/a6684ce0_d72469d1 // for the discussion on alternatives. let fh = self.next_file_handle.fetch_add(1, Ordering::SeqCst); debug!("add file handle {}", fh); self.file_handles .write() .insert(fh, Arc::new(tokio::sync::Mutex::new(blob_reader))); Ok(( Some(fh), fuse_backend_rs::api::filesystem::OpenOptions::empty(), )) } } } } } #[tracing::instrument(skip_all, fields(rq.inode = inode, fh = handle))] fn release( &self, _ctx: &Context, inode: Self::Inode, _flags: u32, handle: Self::Handle, _flush: bool, _flock_release: bool, _lock_owner: Option, ) -> io::Result<()> { // remove and get ownership on the blob reader match self.file_handles.write().remove(&handle) { // drop it, which will close it. Some(blob_reader) => drop(blob_reader), None => { // These might already be dropped if a read error occured. debug!("file_handle {} not found", handle); } } Ok(()) } #[tracing::instrument(skip_all, fields(rq.inode = inode, rq.offset = offset, rq.size = size))] fn read( &self, _ctx: &Context, inode: Self::Inode, handle: Self::Handle, w: &mut dyn fuse_backend_rs::api::filesystem::ZeroCopyWriter, size: u32, offset: u64, _lock_owner: Option, _flags: u32, ) -> io::Result { debug!("read"); // We need to take out the blob reader from self.file_handles, so we can // interact with it in the separate task. // On success, we pass it back out of the task, so we can put it back in self.file_handles. let blob_reader = match self.file_handles.read().get(&handle) { Some(blob_reader) => blob_reader.clone(), None => { warn!("file handle {} unknown", handle); return Err(io::Error::from_raw_os_error(libc::EIO)); } }; let task = self.tokio_handle.spawn(async move { let mut blob_reader = blob_reader.lock().await; // seek to the offset specified, which is relative to the start of the file. let resp = blob_reader.seek(io::SeekFrom::Start(offset as u64)).await; match resp { Ok(pos) => { debug_assert_eq!(offset as u64, pos); } Err(e) => { warn!("failed to seek to offset {}: {}", offset, e); return Err(io::Error::from_raw_os_error(libc::EIO)); } } // As written in the fuse docs, read should send exactly the number // of bytes requested except on EOF or error. let mut buf: Vec = Vec::with_capacity(size as usize); while (buf.len() as u64) < size as u64 { let int_buf = blob_reader.fill_buf().await?; // copy things from the internal buffer into buf to fill it till up until size // an empty buffer signals we reached EOF. if int_buf.is_empty() { break; } // calculate how many bytes we can read from int_buf. // It's either all of int_buf, or the number of bytes missing in buf to reach size. let len_to_copy = std::cmp::min(int_buf.len(), size as usize - buf.len()); // copy these bytes into our buffer buf.extend_from_slice(&int_buf[..len_to_copy]); // and consume them in the buffered reader. blob_reader.consume(len_to_copy); } Ok(buf) }); let buf = self.tokio_handle.block_on(task).unwrap()?; w.write(&buf) } #[tracing::instrument(skip_all, fields(rq.inode = inode))] fn readlink(&self, _ctx: &Context, inode: Self::Inode) -> io::Result> { if inode == ROOT_ID { return Err(io::Error::from_raw_os_error(libc::ENOSYS)); } // lookup the inode match *self.inode_tracker.read().get(inode).unwrap() { InodeData::Directory(..) | InodeData::Regular(..) => { Err(io::Error::from_raw_os_error(libc::EINVAL)) } InodeData::Symlink(ref target) => Ok(target.to_vec()), } } }