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chore(tvix): move store/fs to castore/fs

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With the recent introduction of the RootNodes trait, there's nothing in
the fs module pulling in tvix-store dependencies, so it can live in
tvix-castore.

This allows other crates to make use of TvixStoreFS, without having to
pull in tvix-store.

For example, a tvix-build using a fuse mountpoint at /nix/store doesn't
need a PathInfoService to hold the root nodes that should be present,
but just a list.

tvix-store now has a pathinfoservice/fs module, which contains the
necessary glue logic to implement the RootNodes trait for a
PathInfoService.

To satisfy Rust orphan rules for trait implementations, we had to add a
small wrapper struct. It's mostly hidden away by the make_fs helper
function returning a TvixStoreFs.

It can't be entirely private, as its still leaking into the concrete
type of TvixStoreFS.

tvix-store still has `fuse` and `virtiofs` features, but they now simply
enable these features in the `tvix-castore` crate they depend on.

The tests for the fuse functionality stay in tvix-store for now, as
they populate the root nodes through a PathInfoService.

Once above mentioned "list of root nodes" implementation exists, we
might want to shuffle this around one more time.

Fixes b/341.

Change-Id: I989f664827a5a361b23b34368d242d10c157c756
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10378
Autosubmit: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
This commit is contained in:
Florian Klink 2023-12-17 00:16:22 +02:00 • committed by flokli
parent 52cad86195
commit a5167c508c
18 changed files with 257 additions and 199 deletions
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629
tvix/store/src/fs/mod.rs
View file

@ -1,629 +0,0 @@
mod file_attr;
mod inode_tracker;
mod inodes;
mod root_nodes;
#[cfg(feature = "fuse")]
pub mod fuse;
#[cfg(feature = "virtiofs")]
pub mod virtiofs;
#[cfg(test)]
mod tests;
use fuse_backend_rs::abi::fuse_abi::stat64;
use fuse_backend_rs::api::filesystem::{Context, FileSystem, FsOptions, ROOT_ID};
use futures::StreamExt;
use parking_lot::RwLock;
use std::ops::Deref;
use std::{
collections::HashMap,
io,
sync::atomic::AtomicU64,
sync::{atomic::Ordering, Arc},
time::Duration,
};
use tokio::{
io::{AsyncReadExt, AsyncSeekExt},
sync::mpsc,
};
use tracing::{debug, info_span, instrument, warn};
use tvix_castore::proto as castorepb;
use tvix_castore::{
blobservice::{BlobReader, BlobService},
directoryservice::DirectoryService,
proto::{node::Node, NamedNode},
B3Digest,
};
use self::root_nodes::RootNodes;
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 [RootNodes].
///
/// 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.
/// We store a mapping from currently "explored" names in the root to their
/// inode.
///
/// 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 directory node we
/// explore.
pub struct TvixStoreFs<BS, DS, RN> {
blob_service: BS,
directory_service: DS,
root_nodes_provider: RN,
/// Whether to (try) listing elements in the root.
list_root: bool,
/// This maps a given basename in the root to the inode we allocated for the node.
root_nodes: RwLock<HashMap<Vec<u8>, u64>>,
/// This keeps track of inodes and data alongside them.
inode_tracker: RwLock<InodeTracker>,
/// This holds all open file handles
#[allow(clippy::type_complexity)]
file_handles: RwLock<HashMap<u64, Arc<tokio::sync::Mutex<Box<dyn BlobReader>>>>>,
next_file_handle: AtomicU64,
tokio_handle: tokio::runtime::Handle,
}
impl<BS, DS, RN> TvixStoreFs<BS, DS, RN>
where
BS: Deref<Target = dyn BlobService> + Clone + Send,
DS: Deref<Target = dyn DirectoryService> + Clone + Send + 'static,
RN: RootNodes + Clone + 'static,
{
pub fn new(
blob_service: BS,
directory_service: DS,
root_nodes_provider: RN,
list_root: bool,
) -> Self {
Self {
blob_service,
directory_service,
root_nodes_provider,
list_root,
root_nodes: 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(),
}
}
/// Retrieves the inode for a given root node basename, if present.
/// This obtains a read lock on self.root_nodes.
fn get_inode_for_root_name(&self, name: &[u8]) -> Option<u64> {
self.root_nodes.read().get(name).cloned()
}
/// For a given inode, look up the given directory behind it (from
/// self.inode_tracker), and return its children.
/// The inode_tracker MUST know about this inode already, and it MUST point
/// to a [InodeData::Directory].
/// It is ok if it's a [DirectoryInodeData::Sparse] - in that case, a lookup
/// in self.directory_service is performed, and self.inode_tracker is updated with the
/// [DirectoryInodeData::Populated].
#[instrument(skip(self), err)]
fn get_directory_children(&self, ino: u64) -> io::Result<(B3Digest, Vec<(u64, Node)>)> {
let data = self.inode_tracker.read().get(ino).unwrap();
match *data {
// if it's populated already, return children.
InodeData::Directory(DirectoryInodeData::Populated(
ref parent_digest,
ref children,
)) => Ok((parent_digest.clone(), children.clone())),
// if it's sparse, fetch data using directory_service, populate child nodes
// and update it in [self.inode_tracker].
InodeData::Directory(DirectoryInodeData::Sparse(ref parent_digest, _)) => {
let directory = self
.tokio_handle
.block_on(self.tokio_handle.spawn({
let directory_service = self.directory_service.clone();
let parent_digest = parent_digest.to_owned();
async move { directory_service.get(&parent_digest).await }
}))
.unwrap()?
.ok_or_else(|| {
warn!(directory.digest=%parent_digest, "directory not found");
// If the Directory can't be found, this is a hole, bail out.
io::Error::from_raw_os_error(libc::EIO)
})?;
// Turn the retrieved directory into a InodeData::Directory(DirectoryInodeData::Populated(..)),
// allocating inodes for the children on the way.
let children = {
let mut inode_tracker = self.inode_tracker.write();
let children: Vec<(u64, castorepb::node::Node)> = directory
.nodes()
.map(|child_node| {
let child_ino = inode_tracker.put((&child_node).into());
(child_ino, child_node)
})
.collect();
// replace.
inode_tracker.replace(
ino,
Arc::new(InodeData::Directory(DirectoryInodeData::Populated(
parent_digest.clone(),
children.clone(),
))),
);
children
};
Ok((parent_digest.clone(), children))
}
// if the parent inode was not a directory, this doesn't make sense
InodeData::Regular(..) | InodeData::Symlink(_) => {
Err(io::Error::from_raw_os_error(libc::ENOTDIR))
}
}
}
/// This will turn a lookup request for a name in the root to a ino and
/// [InodeData].
/// It will peek in [self.root_nodes], and then either look it up from
/// [self.inode_tracker],
/// or otherwise fetch from [self.root_nodes], and then insert into
/// [self.inode_tracker].
/// In the case the name can't be found, a libc::ENOENT is returned.
fn name_in_root_to_ino_and_data(
&self,
name: &std::ffi::CStr,
) -> io::Result<(u64, Arc<InodeData>)> {
// Look up the inode for that root node.
// If there's one, [self.inode_tracker] MUST also contain the data,
// which we can then return.
if let Some(inode) = self.get_inode_for_root_name(name.to_bytes()) {
return Ok((
inode,
self.inode_tracker
.read()
.get(inode)
.expect("must exist")
.to_owned(),
));
}
// We don't have it yet, look it up in [self.root_nodes].
match self.tokio_handle.block_on({
let root_nodes_provider = self.root_nodes_provider.clone();
async move { root_nodes_provider.get_by_basename(name.to_bytes()).await }
}) {
// if there was an error looking up the root node, propagate up an IO error.
Err(_e) => Err(io::Error::from_raw_os_error(libc::EIO)),
// the root node doesn't exist, so the file doesn't exist.
Ok(None) => Err(io::Error::from_raw_os_error(libc::ENOENT)),
// The root node does exist
Ok(Some(root_node)) => {
// The name must match what's passed in the lookup, otherwise this is also a ENOENT.
if root_node.get_name() != name.to_bytes() {
debug!(root_node.name=?root_node.get_name(), found_node.name=%name.to_string_lossy(), "node name mismatch");
return Err(io::Error::from_raw_os_error(libc::ENOENT));
}
// Let's check if someone else beat us to updating the inode tracker and
// root_nodes map. This avoids locking inode_tracker for writing.
if let Some(ino) = self.root_nodes.read().get(name.to_bytes()) {
return Ok((
*ino,
self.inode_tracker.read().get(*ino).expect("must exist"),
));
}
// Only in case it doesn't, lock [self.root_nodes] and
// [self.inode_tracker] for writing.
let mut root_nodes = self.root_nodes.write();
let mut inode_tracker = self.inode_tracker.write();
// insert the (sparse) inode data and register in
// self.root_nodes.
let inode_data: InodeData = (&root_node).into();
let ino = inode_tracker.put(inode_data.clone());
root_nodes.insert(name.to_bytes().into(), ino);
Ok((ino, Arc::new(inode_data)))
}
}
}
}
impl<BS, DS, RN> FileSystem for TvixStoreFs<BS, DS, RN>
where
BS: Deref<Target = dyn BlobService> + Clone + Send + 'static,
DS: Deref<Target = dyn DirectoryService> + Send + Clone + 'static,
RN: RootNodes + Clone + 'static,
{
type Handle = u64;
type Inode = u64;
fn init(&self, _capable: FsOptions) -> io::Result<FsOptions> {
Ok(FsOptions::empty())
}
#[tracing::instrument(skip_all, fields(rq.inode = inode))]
fn getattr(
&self,
_ctx: &Context,
inode: Self::Inode,
_handle: Option<Self::Handle>,
) -> io::Result<(stat64, Duration)> {
if inode == ROOT_ID {
return Ok((ROOT_FILE_ATTR.into(), Duration::MAX));
}
match self.inode_tracker.read().get(inode) {
None => 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<fuse_backend_rs::api::filesystem::Entry> {
debug!("lookup");
// This goes from a parent inode to a node.
// - If the parent is [ROOT_ID], we need to check
// [self.root_nodes] (fetching from a [RootNode] provider 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 {
let (ino, inode_data) = self.name_in_root_to_ino_and_data(name)?;
debug!(inode_data=?&inode_data, ino=ino, "Some");
return 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.
let (parent_digest, children) = self.get_directory_children(parent)?;
let span = info_span!("lookup", directory.digest = %parent_digest);
let _enter = span.enter();
// Search for that name in the list of children and return the FileAttrs.
// 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 = self.inode_tracker.read().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<usize>,
) -> 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 root_nodes_provider = self.root_nodes_provider.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 = root_nodes_provider.list().skip(offset as usize).enumerate();
while let Some(node) = stream.next().await {
if tx.send(node).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, root_node)) = rx.blocking_recv() {
let root_node = match root_node {
Err(e) => {
warn!("failed to retrieve pathinfo: {}", e);
return Err(io::Error::from_raw_os_error(libc::EPERM));
}
Ok(root_node) => root_node,
};
let name = root_node.get_name();
// obtain the inode, or allocate a new one.
let ino = self.get_inode_for_root_name(name).unwrap_or_else(|| {
// insert the (sparse) inode data and register in
// self.root_nodes.
let ino = self.inode_tracker.write().put((&root_node).into());
self.root_nodes.write().insert(name.into(), 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,
})?;
// If the buffer is full, add_entry will return `Ok(0)`.
if written == 0 {
break;
}
}
return Ok(());
}
}
// lookup the children, or return an error if it's not a directory.
let (parent_digest, children) = self.get_directory_children(inode)?;
let span = info_span!("lookup", directory.digest = %parent_digest);
let _enter = span.enter();
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 {
#[allow(clippy::unnecessary_cast)]
// libc::S_IFDIR is u32 on Linux and u16 on MacOS
Node::Directory(_) => libc::S_IFDIR as u32,
#[allow(clippy::unnecessary_cast)]
// libc::S_IFDIR is u32 on Linux and u16 on MacOS
Node::File(_) => libc::S_IFREG as u32,
#[allow(clippy::unnecessary_cast)]
// libc::S_IFDIR is u32 on Linux and u16 on MacOS
Node::Symlink(_) => libc::S_IFLNK as u32,
},
name: child_node.get_name(),
})?;
// If the buffer is full, add_entry will return `Ok(0)`.
if written == 0 {
break;
}
}
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");
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");
Err(io::Error::from_raw_os_error(libc::EIO))
}
Err(e) => {
warn!(e=?e, "error opening blob");
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)).await;
match resp {
Ok(pos) => {
debug_assert_eq!(offset, 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);
// copy things from the internal buffer into buf to fill it till up until size
tokio::io::copy(&mut blob_reader.as_mut().take(size as u64), &mut buf).await?;
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()),
}
}
}