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; pub use self::root_nodes::RootNodes; use self::{ file_attr::ROOT_FILE_ATTR, inode_tracker::InodeTracker, inodes::{DirectoryInodeData, InodeData}, }; use crate::proto as castorepb; use crate::{ blobservice::{BlobReader, BlobService}, directoryservice::DirectoryService, proto::{node::Node, NamedNode}, B3Digest, }; use bstr::ByteVec; use bytes::Bytes; use fuse_backend_rs::abi::fuse_abi::{stat64, OpenOptions}; use fuse_backend_rs::api::filesystem::{ Context, FileSystem, FsOptions, GetxattrReply, ListxattrReply, ROOT_ID, }; use futures::StreamExt; use parking_lot::RwLock; use std::ffi::CStr; use std::sync::Mutex; use std::{ collections::HashMap, io, sync::atomic::AtomicU64, sync::{atomic::Ordering, Arc}, time::Duration, }; use tokio::{ io::{AsyncReadExt, AsyncSeekExt}, sync::mpsc, }; use tracing::{debug, instrument, warn, Span}; /// 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. /// Tests for this live in the tvix-store crate. pub struct TvixStoreFs { blob_service: BS, directory_service: DS, root_nodes_provider: RN, /// Whether to (try) listing elements in the root. list_root: bool, /// Whether to expose blob and directory digests as extended attributes. show_xattr: bool, /// This maps a given basename in the root to the inode we allocated for the node. root_nodes: RwLock>, /// This keeps track of inodes and data alongside them. inode_tracker: RwLock, // FUTUREWORK: have a generic container type for dir/file handles and handle // allocation. /// Maps from the handle returned from an opendir to /// This holds all opendir handles (for the root inode) /// They point to the rx part of the channel producing the listing. #[allow(clippy::type_complexity)] dir_handles: RwLock< HashMap< u64, ( Span, Arc)>>>, ), >, >, next_dir_handle: AtomicU64, /// This holds all open file handles #[allow(clippy::type_complexity)] file_handles: RwLock>>)>>, next_file_handle: AtomicU64, tokio_handle: tokio::runtime::Handle, } impl TvixStoreFs where BS: AsRef + Clone + Send, DS: AsRef + Clone + Send + 'static, RN: RootNodes + Clone + 'static, { pub fn new( blob_service: BS, directory_service: DS, root_nodes_provider: RN, list_root: bool, show_xattr: bool, ) -> Self { Self { blob_service, directory_service, root_nodes_provider, list_root, show_xattr, root_nodes: RwLock::new(HashMap::default()), inode_tracker: RwLock::new(Default::default()), dir_handles: RwLock::new(Default::default()), next_dir_handle: AtomicU64::new(1), 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 { 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({ let directory_service = self.directory_service.clone(); let parent_digest = parent_digest.to_owned(); async move { directory_service.as_ref().get(&parent_digest).await } })? .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. // FUTUREWORK: there's a bunch of cloning going on here, which we can probably avoid. let children = { let mut inode_tracker = self.inode_tracker.write(); let children: Vec<(u64, castorepb::node::Node)> = directory .nodes() .map(|child_node| { let (inode_data, _) = InodeData::from_node(child_node.clone()); let child_ino = inode_tracker.put(inode_data); (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)> { // 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, name) = InodeData::from_node(root_node); let ino = inode_tracker.put(inode_data.clone()); root_nodes.insert(name, ino); Ok((ino, Arc::new(inode_data))) } } } } /// Buffer size of the channel providing nodes in the mount root const ROOT_NODES_BUFFER_SIZE: usize = 16; const XATTR_NAME_DIRECTORY_DIGEST: &[u8] = b"user.tvix.castore.directory.digest"; const XATTR_NAME_BLOB_DIGEST: &[u8] = b"user.tvix.castore.blob.digest"; impl FileSystem for TvixStoreFs where BS: AsRef + Clone + Send + 'static, DS: AsRef + Send + Clone + 'static, RN: RootNodes + Clone + 'static, { type Handle = u64; type Inode = 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<(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(inode_data) => { debug!(inode_data = ?inode_data, "found node"); Ok((inode_data.as_fuse_file_attr(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.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(inode_data.as_fuse_entry(ino)); } // 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)?; Span::current().record("directory.digest", parent_digest.to_string()); // 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(child_inode_data.as_fuse_entry(*child_ino)) } else { // Child not found, return ENOENT. Err(io::Error::from_raw_os_error(libc::ENOENT)) } } #[tracing::instrument(skip_all, fields(rq.inode = inode))] fn opendir( &self, _ctx: &Context, inode: Self::Inode, _flags: u32, ) -> io::Result<(Option, OpenOptions)> { // In case opendir on the root is called, we provide the handle, as re-entering that listing is expensive. // For all other directory inodes we just let readdir take care of it. if inode == ROOT_ID { if !self.list_root { return Err(io::Error::from_raw_os_error(libc::EPERM)); // same error code as ipfs/kubo } let root_nodes_provider = self.root_nodes_provider.clone(); let (tx, rx) = mpsc::channel(ROOT_NODES_BUFFER_SIZE); // 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().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; } } }); // Put the rx part into [self.dir_handles]. // 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 dh = self.next_dir_handle.fetch_add(1, Ordering::SeqCst); self.dir_handles .write() .insert(dh, (Span::current(), Arc::new(Mutex::new(rx)))); return Ok(( Some(dh), fuse_backend_rs::api::filesystem::OpenOptions::empty(), // TODO: non-seekable )); } Ok((None, OpenOptions::empty())) } #[tracing::instrument(skip_all, fields(rq.inode = inode, rq.handle = handle, rq.offset = offset), parent = self.dir_handles.read().get(&handle).and_then(|x| x.0.id()))] 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 } // get the handle from [self.dir_handles] let (_span, rx) = match self.dir_handles.read().get(&handle) { Some(rx) => rx.clone(), None => { warn!("dir handle {} unknown", handle); return Err(io::Error::from_raw_os_error(libc::EIO)); } }; let mut rx = rx .lock() .map_err(|_| crate::Error::StorageError("mutex poisoned".into()))?; while let Some((i, n)) = rx.blocking_recv() { let root_node = n.map_err(|e| { warn!("failed to retrieve root node: {}", e); io::Error::from_raw_os_error(libc::EIO) })?; let (inode_data, name) = InodeData::from_node(root_node); // 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(inode_data.clone()); self.root_nodes.write().insert(name.clone(), ino); ino }); let written = add_entry(fuse_backend_rs::api::filesystem::DirEntry { ino, offset: offset + (i as u64) + 1, type_: inode_data.as_fuse_type(), name: &name, })?; // If the buffer is full, add_entry will return `Ok(0)`. if written == 0 { break; } } return Ok(()); } // Non root-node case: lookup the children, or return an error if it's not a directory. let (parent_digest, children) = self.get_directory_children(inode)?; Span::current().record("directory.digest", parent_digest.to_string()); for (i, (ino, child_node)) in children.into_iter().skip(offset as usize).enumerate() { let (inode_data, name) = InodeData::from_node(child_node); // the second parameter will become the "offset" parameter on the next call. let written = add_entry(fuse_backend_rs::api::filesystem::DirEntry { ino, offset: offset + (i as u64) + 1, type_: inode_data.as_fuse_type(), name: &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, rq.handle = handle), parent = self.dir_handles.read().get(&handle).and_then(|x| x.0.id()))] fn readdirplus( &self, _ctx: &Context, inode: Self::Inode, handle: Self::Handle, _size: u32, offset: u64, add_entry: &mut dyn FnMut( fuse_backend_rs::api::filesystem::DirEntry, fuse_backend_rs::api::filesystem::Entry, ) -> io::Result, ) -> io::Result<()> { debug!("readdirplus"); if inode == ROOT_ID { if !self.list_root { return Err(io::Error::from_raw_os_error(libc::EPERM)); // same error code as ipfs/kubo } // get the handle from [self.dir_handles] let (_span, rx) = match self.dir_handles.read().get(&handle) { Some(rx) => rx.clone(), None => { warn!("dir handle {} unknown", handle); return Err(io::Error::from_raw_os_error(libc::EIO)); } }; let mut rx = rx .lock() .map_err(|_| crate::Error::StorageError("mutex poisoned".into()))?; while let Some((i, n)) = rx.blocking_recv() { let root_node = n.map_err(|e| { warn!("failed to retrieve root node: {}", e); io::Error::from_raw_os_error(libc::EPERM) })?; let (inode_data, name) = InodeData::from_node(root_node); // 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(inode_data.clone()); self.root_nodes.write().insert(name.clone(), ino); ino }); let written = add_entry( fuse_backend_rs::api::filesystem::DirEntry { ino, offset: offset + (i as u64) + 1, type_: inode_data.as_fuse_type(), name: &name, }, inode_data.as_fuse_entry(ino), )?; // If the buffer is full, add_entry will return `Ok(0)`. if written == 0 { break; } } return Ok(()); } // Non root-node case: lookup the children, or return an error if it's not a directory. let (parent_digest, children) = self.get_directory_children(inode)?; Span::current().record("directory.digest", parent_digest.to_string()); for (i, (ino, child_node)) in children.into_iter().skip(offset as usize).enumerate() { let (inode_data, name) = InodeData::from_node(child_node); // the second parameter will become the "offset" parameter on the next call. let written = add_entry( fuse_backend_rs::api::filesystem::DirEntry { ino, offset: offset + (i as u64) + 1, type_: inode_data.as_fuse_type(), name: &name, }, inode_data.as_fuse_entry(ino), )?; // If the buffer is full, add_entry will return `Ok(0)`. if written == 0 { break; } } Ok(()) } #[tracing::instrument(skip_all, fields(rq.inode = inode, rq.handle = handle), parent = self.dir_handles.read().get(&handle).and_then(|x| x.0.id()))] fn releasedir( &self, _ctx: &Context, inode: Self::Inode, _flags: u32, handle: Self::Handle, ) -> io::Result<()> { if inode == ROOT_ID { // drop the rx part of the channel. match self.dir_handles.write().remove(&handle) { // drop it, which will close it. Some(rx) => drop(rx), None => { warn!("dir handle not found"); } } } 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"); Err(io::Error::from_raw_os_error(libc::EISDIR)) } InodeData::Regular(ref blob_digest, _blob_size, _) => { Span::current().record("blob.digest", blob_digest.to_string()); match self.tokio_handle.block_on({ let blob_service = self.blob_service.clone(); let blob_digest = blob_digest.clone(); async move { blob_service.as_ref().open_read(&blob_digest).await } }) { 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); self.file_handles .write() .insert(fh, (Span::current(), Arc::new(Mutex::new(blob_reader)))); Ok(( Some(fh), fuse_backend_rs::api::filesystem::OpenOptions::empty(), )) } } } } } #[tracing::instrument(skip_all, fields(rq.inode = inode, rq.handle = handle), parent = self.file_handles.read().get(&handle).and_then(|x| x.0.id()))] fn release( &self, _ctx: &Context, inode: Self::Inode, _flags: u32, handle: Self::Handle, _flush: bool, _flock_release: bool, _lock_owner: Option, ) -> io::Result<()> { match self.file_handles.write().remove(&handle) { // drop the blob reader, which will close it. Some(blob_reader) => drop(blob_reader), None => { // These might already be dropped if a read error occured. warn!("file handle not found"); } } Ok(()) } #[tracing::instrument(skip_all, fields(rq.inode = inode, rq.offset = offset, rq.size = size), parent = self.file_handles.read().get(&handle).and_then(|x| x.0.id()))] 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 (_span, blob_reader) = self .file_handles .read() .get(&handle) .ok_or_else(|| { warn!("file handle {} unknown", handle); io::Error::from_raw_os_error(libc::EIO) }) .cloned()?; let mut blob_reader = blob_reader .lock() .map_err(|_| crate::Error::StorageError("mutex poisoned".into()))?; let buf = self.tokio_handle.block_on(async move { // seek to the offset specified, which is relative to the start of the file. let pos = blob_reader .seek(io::SeekFrom::Start(offset)) .await .map_err(|e| { warn!("failed to seek to offset {}: {}", offset, e); io::Error::from_raw_os_error(libc::EIO) })?; debug_assert_eq!(offset, pos); // 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); // 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::<_, std::io::Error>(buf) })?; 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()), } } #[tracing::instrument(skip_all, fields(rq.inode = inode, name=?name))] fn getxattr( &self, _ctx: &Context, inode: Self::Inode, name: &CStr, size: u32, ) -> io::Result { if !self.show_xattr { return Err(io::Error::from_raw_os_error(libc::ENOSYS)); } // Peek at the inode requested, and construct the response. let digest_str = match *self .inode_tracker .read() .get(inode) .ok_or_else(|| io::Error::from_raw_os_error(libc::ENODATA))? { InodeData::Directory(DirectoryInodeData::Sparse(ref digest, _)) | InodeData::Directory(DirectoryInodeData::Populated(ref digest, _)) if name.to_bytes() == XATTR_NAME_DIRECTORY_DIGEST => { digest.to_string() } InodeData::Regular(ref digest, _, _) if name.to_bytes() == XATTR_NAME_BLOB_DIGEST => { digest.to_string() } _ => { return Err(io::Error::from_raw_os_error(libc::ENODATA)); } }; if size == 0 { Ok(GetxattrReply::Count(digest_str.len() as u32)) } else if size < digest_str.len() as u32 { Err(io::Error::from_raw_os_error(libc::ERANGE)) } else { Ok(GetxattrReply::Value(digest_str.into_bytes())) } } #[tracing::instrument(skip_all, fields(rq.inode = inode))] fn listxattr( &self, _ctx: &Context, inode: Self::Inode, size: u32, ) -> io::Result { if !self.show_xattr { return Err(io::Error::from_raw_os_error(libc::ENOSYS)); } // determine the (\0-terminated list) to of xattr keys present, depending on the type of the inode. let xattrs_names = { let mut out = Vec::new(); if let Some(inode_data) = self.inode_tracker.read().get(inode) { match *inode_data { InodeData::Directory(_) => { out.extend_from_slice(XATTR_NAME_DIRECTORY_DIGEST); out.push_byte(b'\x00'); } InodeData::Regular(..) => { out.extend_from_slice(XATTR_NAME_BLOB_DIGEST); out.push_byte(b'\x00'); } _ => {} } } out }; if size == 0 { Ok(ListxattrReply::Count(xattrs_names.len() as u32)) } else if size < xattrs_names.len() as u32 { Err(io::Error::from_raw_os_error(libc::ERANGE)) } else { Ok(ListxattrReply::Names(xattrs_names.to_vec())) } } }