refactor(tvix/store/fs): Separate FUSE and filesystem code
In prepration for adding virtiofs support, I thought it would make sense to split out the filesystem implementation from FUSE itself. The `fs` module holds the tvix-store filesystem implemetation and the `fuse` module holds the code to spawn a FUSE daemon backed by multiple threads. Change-Id: I8c58447b8c3aa016a613068f8e7ec166554e237c Reviewed-on: https://cl.tvl.fyi/c/depot/+/9343 Reviewed-by: flokli <flokli@flokli.de> Tested-by: BuildkiteCI Autosubmit: Connor Brewster <cbrewster@hey.com>
This commit is contained in:
Connor Brewster
clbot
parent
6b7c936bc5
commit
7e737fde34
10 changed files with 141 additions and 133 deletions
660
tvix/store/src/fs/mod.rs
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660
tvix/store/src/fs/mod.rs
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@ -0,0 +1,660 @@
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mod file_attr;
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mod inode_tracker;
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mod inodes;
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#[cfg(feature = "fuse")]
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pub mod fuse;
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#[cfg(test)]
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mod tests;
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use crate::{
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blobservice::{BlobReader, BlobService},
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directoryservice::DirectoryService,
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pathinfoservice::PathInfoService,
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proto::{node::Node, NamedNode},
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B3Digest, Error,
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};
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use fuse_backend_rs::api::filesystem::{Context, FileSystem, FsOptions, ROOT_ID};
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use nix_compat::store_path::StorePath;
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use parking_lot::RwLock;
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use std::{
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collections::HashMap,
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io,
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str::FromStr,
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sync::atomic::AtomicU64,
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sync::{atomic::Ordering, Arc},
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time::Duration,
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};
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use tokio::io::{AsyncBufReadExt, AsyncSeekExt};
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use tracing::{debug, info_span, warn};
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use self::{
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file_attr::{gen_file_attr, ROOT_FILE_ATTR},
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inode_tracker::InodeTracker,
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inodes::{DirectoryInodeData, InodeData},
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};
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/// This implements a read-only FUSE filesystem for a tvix-store
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/// with the passed [BlobService], [DirectoryService] and [PathInfoService].
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///
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/// We don't allow listing on the root mountpoint (inode 0).
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/// In the future, this might be made configurable once a listing method is
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/// added to [self.path_info_service], and then show all store paths in that
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/// store.
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///
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/// Linux uses inodes in filesystems. When implementing FUSE, most calls are
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/// *for* a given inode.
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///
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/// This means, we need to have a stable mapping of inode numbers to the
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/// corresponding store nodes.
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///
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/// We internally delegate all inode allocation and state keeping to the
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/// inode tracker, and store the currently "explored" store paths together with
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/// root inode of the root.
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///
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/// There's some places where inodes are allocated / data inserted into
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/// the inode tracker, if not allocated before already:
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/// - Processing a `lookup` request, either in the mount root, or somewhere
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/// deeper
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/// - Processing a `readdir` request
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///
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/// Things pointing to the same contents get the same inodes, irrespective of
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/// their own location.
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/// This means:
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/// - Symlinks with the same target will get the same inode.
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/// - Regular/executable files with the same contents will get the same inode
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/// - Directories with the same contents will get the same inode.
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///
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/// Due to the above being valid across the whole store, and considering the
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/// merkle structure is a DAG, not a tree, this also means we can't do "bucketed
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/// allocation", aka reserve Directory.size inodes for each PathInfo.
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pub struct TvixStoreFs {
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blob_service: Arc<dyn BlobService>,
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directory_service: Arc<dyn DirectoryService>,
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path_info_service: Arc<dyn PathInfoService>,
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/// Whether to (try) listing elements in the root.
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list_root: bool,
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/// This maps a given StorePath to the inode we allocated for the root inode.
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store_paths: RwLock<HashMap<StorePath, u64>>,
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/// This keeps track of inodes and data alongside them.
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inode_tracker: RwLock<InodeTracker>,
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/// This holds all open file handles
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file_handles: RwLock<HashMap<u64, Arc<tokio::sync::Mutex<Box<dyn BlobReader>>>>>,
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next_file_handle: AtomicU64,
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tokio_handle: tokio::runtime::Handle,
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}
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impl TvixStoreFs {
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pub fn new(
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blob_service: Arc<dyn BlobService>,
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directory_service: Arc<dyn DirectoryService>,
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path_info_service: Arc<dyn PathInfoService>,
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list_root: bool,
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) -> Self {
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Self {
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blob_service,
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directory_service,
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path_info_service,
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list_root,
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store_paths: RwLock::new(HashMap::default()),
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inode_tracker: RwLock::new(Default::default()),
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file_handles: RwLock::new(Default::default()),
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next_file_handle: AtomicU64::new(1),
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tokio_handle: tokio::runtime::Handle::current(),
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}
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}
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/// This will turn a lookup request for [std::ffi::OsStr] in the root to
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/// a ino and [InodeData].
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/// It will peek in [self.store_paths], and then either look it up from
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/// [self.inode_tracker],
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/// or otherwise fetch from [self.path_info_service], and then insert into
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/// [self.inode_tracker].
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fn name_in_root_to_ino_and_data(
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&self,
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name: &std::ffi::CStr,
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) -> Result<Option<(u64, Arc<InodeData>)>, Error> {
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// parse the name into a [StorePath].
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let store_path = if let Some(name) = name.to_str().ok() {
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match StorePath::from_str(name) {
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Ok(store_path) => store_path,
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Err(e) => {
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debug!(e=?e, "unable to parse as store path");
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// This is not an error, but a "ENOENT", as someone can stat
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// a file inside the root that's no valid store path
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return Ok(None);
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}
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}
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} else {
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debug!("{name:?} is not a valid utf-8 string");
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// same here.
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return Ok(None);
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};
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let ino = {
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// This extra scope makes sure we drop the read lock
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// immediately after reading, to prevent deadlocks.
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let store_paths = self.store_paths.read();
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store_paths.get(&store_path).cloned()
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};
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if let Some(ino) = ino {
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// If we already have that store path, lookup the inode from
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// self.store_paths and then get the data from [self.inode_tracker],
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// which in the case of a [InodeData::Directory] will be fully
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// populated.
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Ok(Some((
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ino,
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self.inode_tracker.read().get(ino).expect("must exist"),
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)))
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} else {
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// If we don't have it, look it up in PathInfoService.
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match self.path_info_service.get(store_path.digest)? {
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// the pathinfo doesn't exist, so the file doesn't exist.
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None => Ok(None),
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Some(path_info) => {
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// The pathinfo does exist, so there must be a root node
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let root_node = path_info.node.unwrap().node.unwrap();
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// The name must match what's passed in the lookup, otherwise we return nothing.
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if root_node.get_name() != store_path.to_string().as_bytes() {
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return Ok(None);
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}
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// Let's check if someone else beat us to updating the inode tracker and
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// store_paths map.
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let mut store_paths = self.store_paths.write();
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if let Some(ino) = store_paths.get(&store_path).cloned() {
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return Ok(Some((
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ino,
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self.inode_tracker.read().get(ino).expect("must exist"),
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)));
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}
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// insert the (sparse) inode data and register in
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// self.store_paths.
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// FUTUREWORK: change put to return the data after
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// inserting, so we don't need to lookup a second
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// time?
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let (ino, inode) = {
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let mut inode_tracker = self.inode_tracker.write();
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let ino = inode_tracker.put((&root_node).into());
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(ino, inode_tracker.get(ino).unwrap())
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};
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store_paths.insert(store_path, ino);
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Ok(Some((ino, inode)))
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}
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}
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}
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}
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/// This will lookup a directory by digest, and will turn it into a
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/// [InodeData::Directory(DirectoryInodeData::Populated(..))].
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/// This is both used to initially insert the root node of a store path,
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/// as well as when looking up an intermediate DirectoryNode.
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fn fetch_directory_inode_data(&self, directory_digest: &B3Digest) -> Result<InodeData, Error> {
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match self.directory_service.get(directory_digest) {
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Err(e) => {
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warn!(e = e.to_string(), directory.digest=%directory_digest, "failed to get directory");
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Err(e)
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}
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// If the Directory can't be found, this is a hole, bail out.
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Ok(None) => {
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tracing::error!(directory.digest=%directory_digest, "directory not found in directory service");
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Err(Error::StorageError(format!(
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"directory {} not found",
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directory_digest
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)))
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}
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Ok(Some(directory)) => Ok(directory.into()),
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}
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}
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}
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impl FileSystem for TvixStoreFs {
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type Inode = u64;
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type Handle = u64;
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fn init(&self, _capable: FsOptions) -> io::Result<FsOptions> {
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Ok(FsOptions::empty())
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}
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#[tracing::instrument(skip_all, fields(rq.inode = inode))]
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fn getattr(
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&self,
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_ctx: &Context,
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inode: Self::Inode,
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_handle: Option<Self::Handle>,
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) -> io::Result<(libc::stat64, Duration)> {
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if inode == ROOT_ID {
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return Ok((ROOT_FILE_ATTR.into(), Duration::MAX));
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}
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match self.inode_tracker.read().get(inode) {
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None => return Err(io::Error::from_raw_os_error(libc::ENOENT)),
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Some(node) => {
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debug!(node = ?node, "found node");
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Ok((gen_file_attr(&node, inode).into(), Duration::MAX))
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}
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}
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}
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#[tracing::instrument(skip_all, fields(rq.parent_inode = parent, rq.name = ?name))]
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fn lookup(
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&self,
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_ctx: &Context,
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parent: Self::Inode,
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name: &std::ffi::CStr,
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) -> io::Result<fuse_backend_rs::api::filesystem::Entry> {
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debug!("lookup");
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// This goes from a parent inode to a node.
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// - If the parent is [ROOT_ID], we need to check
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// [self.store_paths] (fetching from PathInfoService if needed)
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// - Otherwise, lookup the parent in [self.inode_tracker] (which must be
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// a [InodeData::Directory]), and find the child with that name.
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if parent == ROOT_ID {
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return match self.name_in_root_to_ino_and_data(name) {
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Err(e) => {
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warn!("{}", e);
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Err(io::Error::from_raw_os_error(libc::ENOENT))
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}
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Ok(None) => Err(io::Error::from_raw_os_error(libc::ENOENT)),
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Ok(Some((ino, inode_data))) => {
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debug!(inode_data=?&inode_data, ino=ino, "Some");
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Ok(fuse_backend_rs::api::filesystem::Entry {
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inode: ino,
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attr: gen_file_attr(&inode_data, ino).into(),
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attr_timeout: Duration::MAX,
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entry_timeout: Duration::MAX,
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..Default::default()
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})
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}
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};
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}
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// This is the "lookup for "a" inside inode 42.
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// We already know that inode 42 must be a directory.
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// It might not be populated yet, so if it isn't, we do (by
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// fetching from [self.directory_service]), and save the result in
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// [self.inode_tracker].
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// Now it for sure is populated, so we search for that name in the
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// list of children and return the FileAttrs.
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// TODO: Reduce the critical section of this write lock.
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let mut inode_tracker = self.inode_tracker.write();
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let parent_data = inode_tracker.get(parent).unwrap();
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let parent_data = match *parent_data {
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InodeData::Regular(..) | InodeData::Symlink(_) => {
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// if the parent inode was not a directory, this doesn't make sense
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return Err(io::Error::from_raw_os_error(libc::ENOTDIR));
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}
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InodeData::Directory(DirectoryInodeData::Sparse(ref parent_digest, _)) => {
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match self.fetch_directory_inode_data(parent_digest) {
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Ok(new_data) => {
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// update data in [self.inode_tracker] with populated variant.
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// FUTUREWORK: change put to return the data after
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// inserting, so we don't need to lookup a second
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// time?
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let ino = inode_tracker.put(new_data);
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inode_tracker.get(ino).unwrap()
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}
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Err(_e) => {
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return Err(io::Error::from_raw_os_error(libc::EIO));
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}
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}
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}
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InodeData::Directory(DirectoryInodeData::Populated(..)) => parent_data,
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};
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// now parent_data can only be a [InodeData::Directory(DirectoryInodeData::Populated(..))].
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let (parent_digest, children) = if let InodeData::Directory(
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DirectoryInodeData::Populated(ref parent_digest, ref children),
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) = *parent_data
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{
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(parent_digest, children)
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} else {
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panic!("unexpected type")
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};
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let span = info_span!("lookup", directory.digest = %parent_digest);
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let _enter = span.enter();
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// in the children, find the one with the desired name.
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if let Some((child_ino, _)) = children.iter().find(|e| e.1.get_name() == name.to_bytes()) {
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// lookup the child [InodeData] in [self.inode_tracker].
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// We know the inodes for children have already been allocated.
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let child_inode_data = inode_tracker.get(*child_ino).unwrap();
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// Reply with the file attributes for the child.
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// For child directories, we still have all data we need to reply.
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Ok(fuse_backend_rs::api::filesystem::Entry {
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inode: *child_ino,
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attr: gen_file_attr(&child_inode_data, *child_ino).into(),
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attr_timeout: Duration::MAX,
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entry_timeout: Duration::MAX,
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..Default::default()
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})
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} else {
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// Child not found, return ENOENT.
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Err(io::Error::from_raw_os_error(libc::ENOENT))
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}
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}
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// TODO: readdirplus?
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#[tracing::instrument(skip_all, fields(rq.inode = inode, rq.offset = offset))]
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fn readdir(
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&self,
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_ctx: &Context,
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inode: Self::Inode,
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_handle: Self::Handle,
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_size: u32,
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offset: u64,
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add_entry: &mut dyn FnMut(fuse_backend_rs::api::filesystem::DirEntry) -> io::Result<usize>,
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) -> io::Result<()> {
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debug!("readdir");
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if inode == ROOT_ID {
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if !self.list_root {
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return Err(io::Error::from_raw_os_error(libc::EPERM)); // same error code as ipfs/kubo
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} else {
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for (i, path_info) in self
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.path_info_service
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.list()
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.skip(offset as usize)
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.enumerate()
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{
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let path_info = match path_info {
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Err(e) => {
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warn!("failed to retrieve pathinfo: {}", e);
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return Err(io::Error::from_raw_os_error(libc::EPERM));
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}
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Ok(path_info) => path_info,
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};
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// We know the root node exists and the store_path can be parsed because clients MUST validate.
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let root_node = path_info.node.unwrap().node.unwrap();
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let store_path = StorePath::from_bytes(root_node.get_name()).unwrap();
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let ino = {
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// This extra scope makes sure we drop the read lock
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// immediately after reading, to prevent deadlocks.
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let store_paths = self.store_paths.read();
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store_paths.get(&store_path).cloned()
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};
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let ino = match ino {
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Some(ino) => ino,
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None => {
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// insert the (sparse) inode data and register in
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// self.store_paths.
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let ino = self.inode_tracker.write().put((&root_node).into());
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self.store_paths.write().insert(store_path.clone(), ino);
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ino
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}
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};
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let ty = match root_node {
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Node::Directory(_) => libc::S_IFDIR,
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Node::File(_) => libc::S_IFREG,
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Node::Symlink(_) => libc::S_IFLNK,
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};
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let written = add_entry(fuse_backend_rs::api::filesystem::DirEntry {
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ino,
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offset: offset + i as u64 + 1,
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type_: ty,
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name: store_path.to_string().as_bytes(),
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})?;
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// If the buffer is full, add_entry will return `Ok(0)`.
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if written == 0 {
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break;
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}
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}
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return Ok(());
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}
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}
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// lookup the inode data.
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let mut inode_tracker = self.inode_tracker.write();
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let dir_inode_data = inode_tracker.get(inode).unwrap();
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let dir_inode_data = match *dir_inode_data {
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InodeData::Regular(..) | InodeData::Symlink(..) => {
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warn!("Not a directory");
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return Err(io::Error::from_raw_os_error(libc::ENOTDIR));
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}
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InodeData::Directory(DirectoryInodeData::Sparse(ref directory_digest, _)) => {
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match self.fetch_directory_inode_data(directory_digest) {
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Ok(new_data) => {
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// update data in [self.inode_tracker] with populated variant.
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// 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<Self::Handle>,
|
||||
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<u64>,
|
||||
) -> 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<u64>,
|
||||
_flags: u32,
|
||||
) -> io::Result<usize> {
|
||||
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<u8> = 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<Vec<u8>> {
|
||||
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()),
|
||||
}
|
||||
}
|
||||
}
|
||||
Loading…
Add table
Add a link
Reference in a new issue