src/storage/lib/fs_inspect/src/lib.rs

// Copyright 2022 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

//! This module contains the `FsInspect` trait which filesystems can implement in order to expose
//! Inspect metrics in a standardized hierarchy. Once `FsInspect` has been implemented, a
//! filesystem can attach itself to a root node via `FsInspectTree::new`.
//!
//! A filesystem's inspect tree can be tested via `fs_test` by enabling the `supports_inspect`
//! option. This will validate that the inspect tree hierarchy is consistent and that basic
//! information is reported correctly. See `src/storage/fs_test/inspect.cc` for details.

use async_trait::async_trait;
use fuchsia_inspect::{LazyNode, Node};
use futures::FutureExt;
use std::collections::hash_map::HashMap;
use std::sync::{Arc, Mutex, Weak};

const INFO_NODE_NAME: &'static str = "fs.info";
const USAGE_NODE_NAME: &'static str = "fs.usage";
const VOLUMES_NODE_NAME: &'static str = "fs.volumes";

/// Trait that Rust filesystems should implement to expose required Inspect data.
///
/// Once implemented, a filesystem can attach the Inspect data to a given root node by calling
/// `FsInspectTree::new` which will return ownership of the attached nodes/properties.
#[async_trait]
pub trait FsInspect {
    fn get_info_data(&self) -> InfoData;
    async fn get_usage_data(&self) -> UsageData;
}

/// Trait that Rust filesystems which are multi-volume should implement for each volume.
#[async_trait]
pub trait FsInspectVolume {
    async fn get_volume_data(&self) -> VolumeData;
}

/// Maintains ownership of the various inspect nodes/properties. Will be removed from the root node
/// they were attached to when dropped.
pub struct FsInspectTree {
    _info: LazyNode,
    _usage: LazyNode,
    _volumes: LazyNode,
    volumes_tracker: Arc<Mutex<HashMap<String, Weak<dyn FsInspectVolume + Send + Sync + 'static>>>>,
}

impl FsInspectTree {
    /// Attaches Inspect nodes following a standard hierarchy, returning ownership of the newly
    /// created LazyNodes.
    pub fn new(fs: Weak<dyn FsInspect + Send + Sync + 'static>, root: &Node) -> FsInspectTree {
        let fs_clone = fs.clone();
        let info_node = root.create_lazy_child(INFO_NODE_NAME, move || {
            let fs_clone = fs_clone.clone();
            async move {
                let inspector = fuchsia_inspect::Inspector::default();
                if let Some(fs) = fs_clone.upgrade() {
                    fs.get_info_data().record_into(inspector.root());
                }
                Ok(inspector)
            }
            .boxed()
        });

        let fs_clone = fs.clone();
        let usage_node = root.create_lazy_child(USAGE_NODE_NAME, move || {
            let fs_clone = fs_clone.clone();
            async move {
                let inspector = fuchsia_inspect::Inspector::default();
                if let Some(fs) = fs_clone.upgrade() {
                    fs.get_usage_data().await.record_into(inspector.root());
                }
                Ok(inspector)
            }
            .boxed()
        });

        let volumes_tracker = Arc::new(Mutex::new(HashMap::<
            String,
            Weak<dyn FsInspectVolume + Send + Sync + 'static>,
        >::new()));
        let tracker_weak = Arc::downgrade(&volumes_tracker);
        let volumes_node = root.create_lazy_child(VOLUMES_NODE_NAME, move || {
            let tracker_ref = tracker_weak.clone();
            async move {
                let inspector = fuchsia_inspect::Inspector::default();
                let root = inspector.root();
                let tracker = match tracker_ref.upgrade() {
                    Some(tracker) => tracker,
                    // This probably shouldn't happen, but if it does then it would be during a
                    // shutdown race, so just return empty.
                    None => return Ok(inspector),
                };
                let volumes = {
                    let tracker = tracker.lock().unwrap();
                    let mut volumes = Vec::with_capacity(tracker.len());
                    for (name, volume) in tracker.iter() {
                        volumes.push((name.clone(), volume.clone()));
                    }
                    volumes
                };
                for (name, volume_weak) in volumes {
                    let volume = match volume_weak.upgrade() {
                        Some(v) => v,
                        None => continue,
                    };
                    let child = root.create_child(name.clone());
                    volume.get_volume_data().await.record_into(&child);
                    root.record(child);
                }
                Ok(inspector)
            }
            .boxed()
        });

        FsInspectTree {
            _info: info_node,
            _usage: usage_node,
            _volumes: volumes_node,
            volumes_tracker,
        }
    }

    /// Registers a provider for per-volume data.  If `volume` is dropped, the node will remain
    /// present in the inspect tree but yield no data, until `Self::unregister_volume` is called.
    pub fn register_volume(
        self: &Arc<Self>,
        name: String,
        volume: Weak<dyn FsInspectVolume + Send + Sync + 'static>,
    ) {
        self.volumes_tracker.lock().unwrap().insert(name, volume);
    }

    pub fn unregister_volume(&self, name: String) {
        self.volumes_tracker.lock().unwrap().remove(&name);
    }
}

/// fs.info Properties
pub struct InfoData {
    pub id: u64,
    pub fs_type: u64,
    pub name: String,
    pub version_major: u64,
    pub version_minor: u64,
    pub block_size: u64,
    pub max_filename_length: u64,
    pub oldest_version: Option<String>,
}

impl InfoData {
    fn record_into(self, node: &Node) {
        node.record_uint("id", self.id);
        node.record_uint("type", self.fs_type);
        node.record_string("name", self.name);
        node.record_uint("version_major", self.version_major);
        node.record_uint("version_minor", self.version_minor);
        node.record_string(
            "current_version",
            format!("{}.{}", self.version_major, self.version_minor),
        );
        node.record_uint("block_size", self.block_size);
        node.record_uint("max_filename_length", self.max_filename_length);
        if self.oldest_version.is_some() {
            node.record_string("oldest_version", self.oldest_version.as_ref().unwrap());
        }
    }
}

/// fs.usage Properties
pub struct UsageData {
    pub total_bytes: u64,
    pub used_bytes: u64,
    pub total_nodes: u64,
    pub used_nodes: u64,
}

impl UsageData {
    fn record_into(self, node: &Node) {
        node.record_uint("total_bytes", self.total_bytes);
        node.record_uint("used_bytes", self.used_bytes);
        node.record_uint("total_nodes", self.total_nodes);
        node.record_uint("used_nodes", self.used_nodes);
    }
}

/// fs.volume/{name} roperties
pub struct VolumeData {
    pub used_bytes: u64,
    pub bytes_limit: Option<u64>,
    pub used_nodes: u64,
    pub encrypted: bool,
}

impl VolumeData {
    fn record_into(self, node: &Node) {
        node.record_uint("used_bytes", self.used_bytes);
        if let Some(bytes_limit) = self.bytes_limit {
            node.record_uint("bytes_limit", bytes_limit);
        }
        node.record_uint("used_nodes", self.used_nodes);
        node.record_bool("encrypted", self.encrypted);
    }
}