stratisd 3.5.0

// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.

//! Management of devices which are known to stratisd but not in a pool.

use std::{
    collections::{HashMap, HashSet},
    path::PathBuf,
};

use chrono::{DateTime, Utc};
use either::Either;
use serde_json::{Map, Value};

use crate::{
    engine::{
        engine::{DumpState, Pool, StateDiff},
        strat_engine::{
            backstore::{
                find_stratis_devs_by_uuid, CryptActivationHandle, CryptHandle, StratBlockDev,
            },
            liminal::{
                device_info::{
                    reconstruct_stratis_infos, split_stratis_infos, stratis_infos_ref, DeviceSet,
                    LInfo, LLuksInfo, LStratisDevInfo, LStratisInfo,
                },
                identify::{
                    bda_wrapper, identify_block_device, DeviceInfo, LuksInfo, StratisDevInfo,
                    StratisInfo,
                },
                setup::{get_blockdevs, get_metadata},
            },
            metadata::{StratisIdentifiers, BDA},
            pool::StratPool,
            serde_structs::PoolSave,
            shared::tiers_to_bdas,
            types::BDARecordResult,
        },
        structures::Table,
        types::{
            DevUuid, LockedPoolsInfo, MaybeInconsistent, Name, PoolEncryptionInfo, PoolIdentifier,
            PoolUuid, StoppedPoolsInfo, StratBlockDevDiff, UdevEngineEvent, UnlockMethod,
            UuidOrConflict,
        },
        BlockDevTier,
    },
    stratis::{StratisError, StratisResult},
};

/// Devices which stratisd has discovered but which have not been assembled
/// into pools.
#[derive(Debug, Default, Eq, PartialEq)]
pub struct LiminalDevices {
    /// Lookup data structure for pool and device UUIDs corresponding with
    /// a path where the superblock was either removed or the device was removed.
    uuid_lookup: HashMap<PathBuf, (PoolUuid, DevUuid)>,
    /// Devices that have not yet been set up or have been stopped.
    stopped_pools: HashMap<PoolUuid, DeviceSet>,
    /// Lookup data structure for name to UUID mapping for starting pools by name.
    name_to_uuid: HashMap<Name, UuidOrConflict>,
}

impl LiminalDevices {
    #[allow(dead_code)]
    fn invariant(&self) {
        assert!(
            self.stopped_pools
                .keys()
                .cloned()
                .collect::<HashSet<_>>()
                .difference(
                    &self
                        .uuid_lookup
                        .iter()
                        .map(|(_, (u, _))| *u)
                        .collect::<HashSet<_>>()
                )
                .count()
                == 0
        );
    }

    /// Unlock the liminal encrypted devices that correspond to the given pool UUID.
    pub fn unlock_pool(
        &mut self,
        pools: &Table<PoolUuid, StratPool>,
        pool_uuid: PoolUuid,
        unlock_method: UnlockMethod,
    ) -> StratisResult<Vec<(DevUuid, CryptHandle)>> {
        fn handle_luks(
            luks_info: &LLuksInfo,
            unlock_method: UnlockMethod,
        ) -> StratisResult<CryptHandle> {
            if let Some(h) =
                CryptActivationHandle::setup(&luks_info.dev_info.devnode, unlock_method)?
            {
                Ok(h)
            } else {
                Err(StratisError::Msg(format!(
                    "Block device {} does not appear to be formatted with
                        the proper Stratis LUKS2 metadata.",
                    luks_info.dev_info.devnode.display(),
                )))
            }
        }

        let unlocked = match self.stopped_pools.get(&pool_uuid) {
            Some(map) => {
                let encryption_info = map.encryption_info();
                if let Ok(None) = encryption_info {
                    return Err(StratisError::Msg(
                        format!(
                            "Attempted to unlock set of devices belonging to an unencrypted pool with UUID {}",
                            pool_uuid,
                        ),
                    ));
                } else if let Err(e) = encryption_info {
                    return Err(StratisError::Chained(
                        format!(
                            "Error in the encryption information for pool with UUID {}",
                            pool_uuid,
                        ),
                        Box::new(e),
                    ));
                }

                let mut unlocked = Vec::new();
                for (dev_uuid, info) in map.iter() {
                    match info {
                        LInfo::Stratis(_) => (),
                        LInfo::Luks(ref luks_info) => match handle_luks(luks_info, unlock_method) {
                            Ok(handle) => unlocked.push((*dev_uuid, handle)),
                            Err(e) => {
                                return Err(handle_unlock_rollback(
                                    e,
                                    unlocked
                                        .into_iter()
                                        .map(|(_, handle)| handle)
                                        .collect::<Vec<_>>(),
                                ));
                            }
                        },
                    }
                }
                unlocked
            }
            None => match pools.get_by_uuid(pool_uuid) {
                Some((_, pool)) => {
                    if pool.is_encrypted() {
                        vec![]
                    } else {
                        return Err(StratisError::Msg(format!(
                            "Pool with UUID {} is not encrypted and cannot be unlocked.",
                            pool_uuid,
                        )));
                    }
                }
                None => {
                    return Err(StratisError::Msg(format!(
                        "No devices with UUID {} have been registered with stratisd.",
                        pool_uuid,
                    )))
                }
            },
        };

        Ok(unlocked)
    }

    /// Start a pool, create the devicemapper devices, and return the fully constructed
    /// pool.
    pub fn start_pool(
        &mut self,
        pools: &Table<PoolUuid, StratPool>,
        id: PoolIdentifier<PoolUuid>,
        unlock_method: Option<UnlockMethod>,
    ) -> StratisResult<(Name, PoolUuid, StratPool)> {
        let pool_uuid = match id {
            PoolIdentifier::Uuid(u) => u,
            PoolIdentifier::Name(n) => self
                .name_to_uuid
                .get(&n)
                .ok_or_else(|| StratisError::Msg(format!("Could not find a pool with name {}", n)))
                .and_then(|uc| uc.to_result())?,
        };
        let encryption_info = self
            .stopped_pools
            .get(&pool_uuid)
            .ok_or_else(|| {
                StratisError::Msg(format!(
                    "Requested pool with UUID {} was not found in stopped pools",
                    pool_uuid
                ))
            })?
            .encryption_info();
        let unlocked_devices = match (encryption_info, unlock_method) {
            (Ok(Some(_)), None) => {
                return Err(StratisError::Msg(format!(
                    "Pool with UUID {} is encrypted but no unlock method was provided",
                    pool_uuid,
                )));
            }
            (Ok(None), None) => Vec::new(),
            (Ok(Some(_)), Some(method)) => self.unlock_pool(pools, pool_uuid, method)?,
            (Ok(None), Some(_)) => {
                return Err(StratisError::Msg(format!(
                    "Pool with UUID {} is not encrypted but an unlock method was provided",
                    pool_uuid,
                )));
            }
            (Err(e), _) => return Err(e),
        };

        let uuids = unlocked_devices
            .iter()
            .map(|(dev_uuid, _)| *dev_uuid)
            .collect::<Vec<_>>();
        let handles = unlocked_devices
            .into_iter()
            .map(|(_, h)| h)
            .collect::<Vec<_>>();

        let mut stopped_pool = self
            .stopped_pools
            .remove(&pool_uuid)
            .expect("Checked above");
        match find_stratis_devs_by_uuid(pool_uuid, uuids) {
            Ok(infos) => infos.into_iter().for_each(|(dev_uuid, (path, devno))| {
                if let Ok(Ok(Some(bda))) = bda_wrapper(&path) {
                    self.uuid_lookup
                        .insert(path.to_path_buf(), (pool_uuid, dev_uuid));

                    stopped_pool.process_info_add(DeviceInfo::Stratis(StratisInfo {
                        dev_info: StratisDevInfo {
                            device_number: devno,
                            devnode: path.to_path_buf(),
                        },
                        bda,
                    }));
                } else {
                    warn!(
                        "Failed to read BDA of device with pool UUID {}, dev UUID, {}; ignoring",
                        pool_uuid, dev_uuid
                    );
                }
            }),
            Err(e) => {
                warn!("Failed to scan for newly unlocked Stratis devices: {}", e);
                self.stopped_pools.insert(pool_uuid, stopped_pool);
                return Err(handle_unlock_rollback(e, handles));
            }
        };

        match self.try_setup_pool(pools, pool_uuid, stopped_pool) {
            Ok((name, pool)) => Ok((name, pool_uuid, pool)),
            Err(e) => Err(handle_unlock_rollback(e, handles)),
        }
    }

    /// Stop a pool, tear down the devicemapper devices, and store the pool information
    /// in an internal data structure for later starting.
    pub fn stop_pool(
        &mut self,
        pool_name: &Name,
        pool_uuid: PoolUuid,
        pool: &mut StratPool,
    ) -> StratisResult<()> {
        let devices = pool.stop(pool_name)?;
        for (_, device) in devices.iter() {
            match device {
                LInfo::Luks(l) => {
                    self.uuid_lookup.insert(
                        l.dev_info.devnode.clone(),
                        (l.identifiers.pool_uuid, l.identifiers.device_uuid),
                    );
                }
                LInfo::Stratis(s) => {
                    self.uuid_lookup.insert(
                        s.dev_info.devnode.clone(),
                        (
                            s.bda.identifiers().pool_uuid,
                            s.bda.identifiers().device_uuid,
                        ),
                    );
                }
            }
        }
        self.stopped_pools.insert(pool_uuid, devices);
        if let Some(maybe_conflict) = self.name_to_uuid.get_mut(pool_name) {
            maybe_conflict.add(pool_uuid);
            if let UuidOrConflict::Conflict(set) = maybe_conflict {
                warn!("Found conflicting names for stopped pools; UUID will be required to start pools with UUIDs {}", set.iter().map(|u| u.to_string()).collect::<Vec<_>>().join(", "));
            }
        } else {
            self.name_to_uuid
                .insert(pool_name.clone(), UuidOrConflict::Uuid(pool_uuid));
        }
        Ok(())
    }

    /// Get a mapping of pool UUIDs from all of the LUKS2 devices that are currently
    /// locked to their encryption info in the set of pools that are not yet set up.
    pub fn locked_pools(&self) -> LockedPoolsInfo {
        LockedPoolsInfo {
            name_to_uuid: self
                .name_to_uuid
                .iter()
                .filter_map(|(name, maybe_conflict)| {
                    maybe_conflict
                        .to_result()
                        .ok()
                        .map(|uuid| (name.clone(), uuid))
                })
                .collect::<HashMap<_, _>>(),
            uuid_to_name: self
                .name_to_uuid
                .iter()
                .filter_map(|(name, maybe_conflict)| {
                    maybe_conflict
                        .to_result()
                        .ok()
                        .map(|uuid| (uuid, name.clone()))
                })
                .collect::<HashMap<_, _>>(),
            locked: self
                .stopped_pools
                .iter()
                .filter_map(|(pool_uuid, map)| {
                    map.locked_pool_info().map(|info| (*pool_uuid, info))
                })
                .collect(),
        }
    }

    /// Get a mapping of pool UUIDs to device sets for all stopped pools.
    pub fn stopped_pools(&self) -> StoppedPoolsInfo {
        StoppedPoolsInfo {
            name_to_uuid: self
                .name_to_uuid
                .iter()
                .filter_map(|(name, maybe_conflict)| {
                    maybe_conflict
                        .to_result()
                        .ok()
                        .map(|uuid| (name.clone(), uuid))
                })
                .collect::<HashMap<_, _>>(),
            uuid_to_name: self
                .name_to_uuid
                .iter()
                .filter_map(|(name, maybe_conflict)| {
                    maybe_conflict
                        .to_result()
                        .ok()
                        .map(|uuid| (uuid, name.clone()))
                })
                .collect::<HashMap<_, _>>(),
            stopped: self
                .stopped_pools
                .iter()
                .filter_map(|(pool_uuid, map)| {
                    map.stopped_pool_info().map(|info| (*pool_uuid, info))
                })
                .collect(),
        }
    }

    /// Calculate whether block device size has changed.
    fn handle_size_change(
        tier: BlockDevTier,
        dev_uuid: DevUuid,
        dev: &mut StratBlockDev,
    ) -> Option<(DevUuid, StratBlockDevDiff)> {
        if tier == BlockDevTier::Data {
            let orig = dev.cached();
            match dev.calc_new_size() {
                Ok(Some(s)) => Some((dev_uuid, orig.diff(&dev.dump(s)))),
                Err(e) => {
                    warn!(
                        "Failed to determine device size for {}: {}",
                        dev.devnode().display(),
                        e
                    );
                    None
                }
                _ => None,
            }
        } else {
            None
        }
    }

    /// Take maps of pool UUIDs to sets of devices and return a list of
    /// information about created pools.
    ///
    /// Precondition: No pools have yet been set up, i.e., it is unnecessary
    /// to check for membership in any of the existing categories of device
    /// sets.
    pub fn setup_pools(
        &mut self,
        all_devices: (
            HashMap<PoolUuid, Vec<LuksInfo>>,
            HashMap<PoolUuid, Vec<StratisInfo>>,
        ),
    ) -> Vec<(Name, PoolUuid, StratPool)> {
        let table = Table::default();
        let (mut luks_devices, mut stratis_devices) = all_devices;

        let pool_uuids: HashSet<PoolUuid> = luks_devices
            .keys()
            .cloned()
            .collect::<HashSet<PoolUuid>>()
            .union(&stratis_devices.keys().cloned().collect())
            .cloned()
            .collect();

        pool_uuids
            .iter()
            .filter_map(|pool_uuid| {
                let luks_infos = luks_devices.remove(pool_uuid);
                let stratis_infos = stratis_devices.remove(pool_uuid);
                let infos: Vec<DeviceInfo> = stratis_infos
                    .unwrap_or_default()
                    .drain(..)
                    .map(DeviceInfo::Stratis)
                    .chain(
                        luks_infos
                            .unwrap_or_default()
                            .drain(..)
                            .map(DeviceInfo::Luks),
                    )
                    .collect();

                let mut info_map = DeviceSet::new();
                for info in infos {
                    match &info {
                        DeviceInfo::Luks(l) => {
                            self.uuid_lookup.insert(
                                l.dev_info.devnode.clone(),
                                (l.identifiers.pool_uuid, l.identifiers.device_uuid),
                            );
                        }
                        DeviceInfo::Stratis(s) => {
                            self.uuid_lookup.insert(
                                s.dev_info.devnode.clone(),
                                (s.bda.identifiers().pool_uuid, s.bda.identifiers().device_uuid),
                            );
                        }
                    }

                    info_map.process_info_add(info);
                }

                match info_map.pool_name() {
                    Ok(MaybeInconsistent::No(Some(name))) => {
                        if let Some(maybe_conflict) = self.name_to_uuid.get_mut(&name) {
                            maybe_conflict.add(*pool_uuid);
                            if let UuidOrConflict::Conflict(set) = maybe_conflict {
                                warn!("Found conflicting names for stopped pools; UUID will be required to start pools with UUIDs {}", set.iter().map(|u| u.to_string()).collect::<Vec<_>>().join(", "));
                            }
                        } else {
                            self.name_to_uuid
                                .insert(name, UuidOrConflict::Uuid(*pool_uuid));
                        }
                    },
                    Err(e) => {
                        info!("Error while attempting to determine pool name for pool with UUID {}: {}; this may resolve when more devices appear and are processed", pool_uuid, e);
                    }
                    _ => (),
                }

                self.try_setup_started_pool(&table, *pool_uuid, info_map)
                    .map(|(pool_name, mut pool)| {
                        match pool.blockdevs_mut() {
                            Ok(blockdevs) => {
                                for (dev_uuid, tier, blockdev) in blockdevs {
                                    if let Some(size) =
                                        Self::handle_size_change(tier, dev_uuid, blockdev)
                                            .and_then(|(_, d)| d.size.changed())
                                            .and_then(|c| c)
                                    {
                                        blockdev.set_new_size(size);
                                    }
                                }
                            }
                            Err(e) => {
                                warn!("Failed to check size of block devices in newly set up pool: {}", e);
                            }
                        }
                        (pool_name, *pool_uuid, pool)
                    })
            })
            .collect::<Vec<(Name, PoolUuid, StratPool)>>()
    }

    /// Attempt to set up a pool, starting it if it is not already started.
    ///
    /// See documentation for setup_pool for more information.
    ///
    /// Precondition: pools.get_by_uuid(pool_uuid).is_none() &&
    ///               self.stopped_pools.get(pool_uuid).is_none()
    fn try_setup_pool(
        &mut self,
        pools: &Table<PoolUuid, StratPool>,
        pool_uuid: PoolUuid,
        device_set: DeviceSet,
    ) -> StratisResult<(Name, StratPool)> {
        fn try_setup_pool_failure(
            pools: &Table<PoolUuid, StratPool>,
            pool_uuid: PoolUuid,
            luks_info: StratisResult<(Option<PoolEncryptionInfo>, MaybeInconsistent<Option<Name>>)>,
            infos: &HashMap<DevUuid, LStratisDevInfo>,
            bdas: HashMap<DevUuid, BDA>,
            meta_res: StratisResult<(DateTime<Utc>, PoolSave)>,
        ) -> BDARecordResult<(Name, StratPool)> {
            let (timestamp, metadata) = match meta_res {
                Ok(o) => o,
                Err(e) => return Err((e, bdas)),
            };

            setup_pool(
                pools, pool_uuid, luks_info, infos, bdas, timestamp, metadata,
            )
        }

        assert!(pools.get_by_uuid(pool_uuid).is_none());
        assert!(self.stopped_pools.get(&pool_uuid).is_none());

        let encryption_info = device_set.encryption_info();
        let pool_name = device_set.pool_name();
        let luks_info = encryption_info.and_then(|ei| pool_name.map(|pn| (ei, pn)));
        let infos = match device_set.into_opened_set() {
            Either::Left(i) => i,
            Either::Right(ds) => {
                let err = StratisError::Msg(format!(
                    "Some of the devices in pool with UUID {} are unopened",
                    pool_uuid,
                ));
                info!("Attempt to set up pool failed, but it may be possible to set up the pool later, if the situation changes: {}", err);
                if !ds.is_empty() {
                    self.stopped_pools.insert(pool_uuid, ds);
                }
                return Err(err);
            }
        };

        let res = load_stratis_metadata(pool_uuid, stratis_infos_ref(&infos));
        let (infos, bdas) = split_stratis_infos(infos);
        match try_setup_pool_failure(pools, pool_uuid, luks_info, &infos, bdas, res) {
            Ok((name, pool)) => {
                self.uuid_lookup = self
                    .uuid_lookup
                    .drain()
                    .filter(|(_, (p, _))| *p != pool_uuid)
                    .collect();
                self.name_to_uuid = self
                    .name_to_uuid
                    .drain()
                    .filter_map(|(n, mut maybe_conflict)| {
                        if maybe_conflict.remove(&pool_uuid) {
                            None
                        } else {
                            Some((n, maybe_conflict))
                        }
                    })
                    .collect();
                info!(
                    "Pool with name \"{}\" and UUID \"{}\" set up",
                    name, pool_uuid
                );
                Ok((name, pool))
            }
            Err((err, bdas)) => {
                info!("Attempt to set up pool failed, but it may be possible to set up the pool later, if the situation changes: {}", err);
                let device_set = reconstruct_stratis_infos(infos, bdas);
                if !device_set.is_empty() {
                    self.stopped_pools.insert(pool_uuid, device_set);
                }
                Err(err)
            }
        }
    }

    /// Variation on try_setup_pool that returns None if the pool is marked
    /// as stopped in its metadata.
    ///
    /// Precondition: pools.get_by_uuid(pool_uuid).is_none() &&
    ///               self.stopped_pools.get(pool_uuid).is_none()
    fn try_setup_started_pool(
        &mut self,
        pools: &Table<PoolUuid, StratPool>,
        pool_uuid: PoolUuid,
        device_set: DeviceSet,
    ) -> Option<(Name, StratPool)> {
        fn try_setup_started_pool_failure(
            pools: &Table<PoolUuid, StratPool>,
            pool_uuid: PoolUuid,
            luks_info: StratisResult<(Option<PoolEncryptionInfo>, MaybeInconsistent<Option<Name>>)>,
            infos: &HashMap<DevUuid, LStratisDevInfo>,
            bdas: HashMap<DevUuid, BDA>,
            meta_res: StratisResult<(DateTime<Utc>, PoolSave)>,
        ) -> BDARecordResult<Either<(Name, StratPool), HashMap<DevUuid, BDA>>> {
            let (timestamp, metadata) = match meta_res {
                Ok(o) => o,
                Err(e) => return Err((e, bdas)),
            };
            if let Some(true) | None = metadata.started {
                setup_pool(
                    pools, pool_uuid, luks_info, infos, bdas, timestamp, metadata,
                )
                .map(Either::Left)
            } else {
                Ok(Either::Right(bdas))
            }
        }

        assert!(pools.get_by_uuid(pool_uuid).is_none());
        assert!(self.stopped_pools.get(&pool_uuid).is_none());

        let encryption_info = device_set.encryption_info();
        let pool_name = device_set.pool_name();
        let luks_info = encryption_info.and_then(|ei| pool_name.map(|pn| (ei, pn)));
        let infos = match device_set.into_opened_set() {
            Either::Left(i) => i,
            Either::Right(ds) => {
                let err = StratisError::Msg(format!(
                    "Some of the devices in pool with UUID {} are unopened",
                    pool_uuid,
                ));
                info!("Attempt to set up pool failed, but it may be possible to set up the pool later, if the situation changes: {}", err);
                if !ds.is_empty() {
                    self.stopped_pools.insert(pool_uuid, ds);
                }
                return None;
            }
        };

        let res = load_stratis_metadata(pool_uuid, stratis_infos_ref(&infos));
        let (infos, bdas) = split_stratis_infos(infos);
        match try_setup_started_pool_failure(pools, pool_uuid, luks_info, &infos, bdas, res) {
            Ok(Either::Left((name, pool))) => {
                self.uuid_lookup = self
                    .uuid_lookup
                    .drain()
                    .filter(|(_, (p, _))| *p != pool_uuid)
                    .collect();
                self.name_to_uuid = self
                    .name_to_uuid
                    .drain()
                    .filter_map(|(n, mut maybe_conflict)| {
                        if maybe_conflict.remove(&pool_uuid) {
                            None
                        } else {
                            Some((n, maybe_conflict))
                        }
                    })
                    .collect();
                info!(
                    "Pool with name \"{}\" and UUID \"{}\" set up",
                    name, pool_uuid
                );
                Some((name, pool))
            }
            Ok(Either::Right(bdas)) => {
                let device_set = reconstruct_stratis_infos(infos, bdas);
                if !device_set.is_empty() {
                    self.stopped_pools.insert(pool_uuid, device_set);
                }
                None
            }
            Err((err, bdas)) => {
                info!("Attempt to set up pool failed, but it may be possible to set up the pool later, if the situation changes: {}", err);
                let device_set = reconstruct_stratis_infos(infos, bdas);
                if !device_set.is_empty() {
                    self.stopped_pools.insert(pool_uuid, device_set);
                }
                None
            }
        }
    }

    /// On udev events, stratisd checks whether block devices have changed in size.
    /// This allows us to update the user with the new size if it has changed.
    /// This method runs a check on device size on each udev change or add event
    /// to determine whether the size has indeed changed so we can update it in
    /// our internal data structures.
    pub fn block_evaluate_size(
        pools: &mut Table<PoolUuid, StratPool>,
        event: &UdevEngineEvent,
    ) -> StratisResult<Option<(DevUuid, StratBlockDevDiff)>> {
        let mut ret = None;

        let event_type = event.event_type();
        let device_path = match event.device().devnode() {
            Some(d) => d,
            None => return Ok(None),
        };
        let device_info = match event_type {
            libudev::EventType::Add | libudev::EventType::Change => {
                if device_path.exists() {
                    identify_block_device(event)
                } else {
                    None
                }
            }
            _ => None,
        };

        if event_type == libudev::EventType::Add || event_type == libudev::EventType::Change {
            if let Some(di) = device_info {
                let pool_uuid = di.stratis_identifiers().pool_uuid;
                let dev_uuid = di.stratis_identifiers().device_uuid;
                if let Some((_, pool)) = pools.get_mut_by_uuid(pool_uuid) {
                    if let Some((tier, dev)) = pool.get_mut_strat_blockdev(dev_uuid)? {
                        ret = Self::handle_size_change(tier, dev_uuid, dev);
                    }
                }
            }
        }

        Ok(ret)
    }

    /// Given some information gathered about a single Stratis device, determine
    /// whether or not a pool can be constructed, and if it can, construct the
    /// pool and return the newly constructed pool. If the device appears to
    /// belong to a pool that has already been set up assume that no further
    /// processing is required and return None. If there is an error
    /// constructing the pool, retain the set of devices.
    pub fn block_evaluate(
        &mut self,
        pools: &Table<PoolUuid, StratPool>,
        event: &UdevEngineEvent,
    ) -> Option<(Name, PoolUuid, StratPool)> {
        let event_type = event.event_type();
        let device_path = match event.device().devnode() {
            Some(d) => d,
            None => return None,
        };
        let device_info = match event_type {
            libudev::EventType::Add | libudev::EventType::Change => {
                if device_path.exists() {
                    identify_block_device(event)
                } else {
                    None
                }
            }
            _ => None,
        };

        if event_type == libudev::EventType::Add
            || (event_type == libudev::EventType::Change && device_info.is_some())
        {
            if let Some(info) = device_info {
                let stratis_identifiers = info.stratis_identifiers();
                let pool_uuid = stratis_identifiers.pool_uuid;
                let device_uuid = stratis_identifiers.device_uuid;
                if let Some((_, pool)) = pools.get_by_uuid(pool_uuid) {
                    if pool.get_strat_blockdev(device_uuid).is_none() {
                        warn!("Found a device with {} that identifies itself as belonging to pool with UUID {}, but that pool is already up and running and does not appear to contain the device",
                              info,
                              pool_uuid);
                    }
                    // FIXME: There might be something to check if the device is
                    // included in the pool, but that is less clear.
                    None
                } else {
                    let mut devices = self
                        .stopped_pools
                        .remove(&pool_uuid)
                        .unwrap_or_else(DeviceSet::new);

                    self.uuid_lookup
                        .insert(device_path.to_path_buf(), (pool_uuid, device_uuid));

                    devices.process_info_add(info);
                    match devices.pool_name() {
                        Ok(MaybeInconsistent::No(Some(name))) => {
                            if let Some(maybe_conflict) = self.name_to_uuid.get_mut(&name) {
                                maybe_conflict.add(pool_uuid);
                                if let UuidOrConflict::Conflict(set) = maybe_conflict {
                                    warn!("Found conflicting names for stopped pools; UUID will be required to start pools with UUIDs {}", set.iter().map(|u| u.to_string()).collect::<Vec<_>>().join(", "));
                                }
                            } else {
                                self.name_to_uuid
                                    .insert(name.clone(), UuidOrConflict::Uuid(pool_uuid));
                            }
                        }
                        Err(e) => {
                            info!("Error while attempting to determine pool name for pool with UUID {}: {}; this may resolve when more devices appear and are processed", pool_uuid, e);
                        }
                        _ => (),
                    }
                    self.try_setup_started_pool(pools, pool_uuid, devices)
                        .map(|(name, pool)| (name, pool_uuid, pool))
                }
            } else {
                None
            }
        } else if (event_type == libudev::EventType::Change && device_info.is_none())
            || event_type == libudev::EventType::Remove
        {
            let (pool_uuid, dev_uuid) =
                if let Some((pool_uuid, dev_uuid)) = self.uuid_lookup.get(device_path) {
                    (*pool_uuid, *dev_uuid)
                } else {
                    return None;
                };
            if self.stopped_pools.get(&pool_uuid).is_some() {
                let mut devices = self
                    .stopped_pools
                    .remove(&pool_uuid)
                    .unwrap_or_else(DeviceSet::new);

                devices.process_info_remove(device_path, pool_uuid, dev_uuid);
                self.uuid_lookup.remove(device_path);
                match devices.pool_name() {
                    Ok(MaybeInconsistent::No(Some(name))) => {
                        if let Some(maybe_conflict) = self.name_to_uuid.get_mut(&name) {
                            maybe_conflict.add(pool_uuid);
                            if let UuidOrConflict::Conflict(set) = maybe_conflict {
                                warn!("Found conflicting names for stopped pools; UUID will be required to start pools with UUIDs {}", set.iter().map(|u| u.to_string()).collect::<Vec<_>>().join(", "));
                            }
                        } else {
                            self.name_to_uuid
                                .insert(name, UuidOrConflict::Uuid(pool_uuid));
                        }
                    }
                    _ => {
                        self.name_to_uuid = self
                            .name_to_uuid
                            .drain()
                            .filter_map(|(n, mut maybe_conflict)| {
                                if maybe_conflict.remove(&pool_uuid) {
                                    None
                                } else {
                                    Some((n, maybe_conflict))
                                }
                            })
                            .collect();
                    }
                }

                if !devices.is_empty() {
                    self.stopped_pools.insert(pool_uuid, devices);
                }
            }
            None
        } else {
            None
        }
    }
}

impl<'a> Into<Value> for &'a LiminalDevices {
    fn into(self) -> Value {
        json!({
            "stopped_pools": Value::Array(
                self.stopped_pools
                    .iter()
                    .map(|(uuid, set)| {
                        json!({
                            "pool_uuid": uuid.to_string(),
                            "devices": <&DeviceSet as Into<Value>>::into(set),
                        })
                    })
                    .collect()
            ),
            "path_to_ids_map": Value::Object(
                self.uuid_lookup
                    .iter()
                    .map(|(path, (pool_uuid, dev_uuid))| {
                        (
                            path.display().to_string(),
                            Value::Array(vec![
                                Value::from(pool_uuid.to_string()),
                                Value::from(dev_uuid.to_string()),
                            ]),
                        )
                    })
                    .collect::<Map<_, _>>()
            ),
            "name_to_pool_uuid_map": Value::Object(
                self.name_to_uuid
                    .iter()
                    .map(|(name, maybe_conflict)| {
                        (
                            name.to_string(),
                            match maybe_conflict {
                                UuidOrConflict::Uuid(u) => Value::from(u.to_string()),
                                UuidOrConflict::Conflict(set) => Value::from(set.iter().map(|u| Value::from(u.to_string())).collect::<Vec<_>>())
                            },
                        )
                    })
                    .collect::<Map<_, _>>()
            )
        })
    }
}

/// Read the BDA and MDA information for a set of devices that has been
/// determined to be a part of the same pool.
fn load_stratis_metadata(
    pool_uuid: PoolUuid,
    infos: HashMap<DevUuid, &LStratisInfo>,
) -> StratisResult<(DateTime<Utc>, PoolSave)> {
    if let Some((dev_uuid, info)) = infos.iter().find(|(dev_uuid, info)| {
        **dev_uuid != info.bda.dev_uuid() || pool_uuid != info.bda.pool_uuid()
    }) {
        return Err(
            StratisError::Msg(format!(
                "Mismatch between Stratis identifiers previously read and those found on some BDA: {} != {}",
                StratisIdentifiers::new(pool_uuid, *dev_uuid),
                StratisIdentifiers::new(info.bda.pool_uuid(), info.bda.dev_uuid())
            )));
    }

    match get_metadata(infos) {
        Ok(opt) => opt
            .ok_or_else(|| {
                StratisError::Msg(format!(
                    "No metadata found on devices associated with pool UUID {}",
                    pool_uuid
                ))
            }),
        Err(err) => Err(StratisError::Chained(
            format!(
                "There was an error encountered when reading the metadata for the devices found for pool with UUID {}",
                pool_uuid,
            ),
            Box::new(err),
        ))
    }
}

/// Given a set of devices, try to set up a pool.
/// Return the pool information if a pool is set up. Otherwise, return
/// the pool information to the stopped pools data structure.
/// Do not attempt setup if the pool contains any unopened devices.
///
/// If there is a name conflict between the set of devices in devices
/// and some existing pool, return an error.
fn setup_pool(
    pools: &Table<PoolUuid, StratPool>,
    pool_uuid: PoolUuid,
    luks_info: StratisResult<(Option<PoolEncryptionInfo>, MaybeInconsistent<Option<Name>>)>,
    infos: &HashMap<DevUuid, LStratisDevInfo>,
    bdas: HashMap<DevUuid, BDA>,
    timestamp: DateTime<Utc>,
    metadata: PoolSave,
) -> BDARecordResult<(Name, StratPool)> {
    if let Some((uuid, _)) = pools.get_by_name(&metadata.name) {
        return Err((
            StratisError::Msg(format!(
                "There is a pool name conflict. The devices currently being processed have been identified as belonging to the pool with UUID {} and name {}, but a pool with the same name and UUID {} is already active",
                pool_uuid,
                &metadata.name,
                uuid
            )), bdas));
    }

    let (datadevs, cachedevs) = match get_blockdevs(&metadata.backstore, infos, bdas) {
        Err((err, bdas)) => return Err(
            (StratisError::Chained(
                format!(
                    "There was an error encountered when calculating the block devices for pool with UUID {} and name {}",
                    pool_uuid,
                    &metadata.name,
                ),
                Box::new(err)
            ), bdas)),
        Ok((datadevs, cachedevs)) => (datadevs, cachedevs),
    };

    if datadevs.get(0).is_none() {
        return Err((
            StratisError::Msg(format!(
                "There do not appear to be any data devices in the set with pool UUID {}",
                pool_uuid
            )),
            tiers_to_bdas(datadevs, cachedevs, None),
        ));
    }

    let (pool_einfo, pool_name) = match luks_info {
        Ok(inner) => inner,
        Err(_) => {
            // NOTE: This is not actually a hopeless situation. It may be
            // that a LUKS device owned by Stratis corresponding to a
            // Stratis device has just not been discovered yet. If it
            // is, the appropriate info will be updated, and setup may
            // yet succeed.
            return Err((
                StratisError::Msg(format!(
                        "Some data devices in the set belonging to pool with UUID {} and name {} appear to be encrypted devices managed by Stratis, and some do not",
                        pool_uuid,
                        &metadata.name
                )), tiers_to_bdas(datadevs, cachedevs, None)));
        }
    };

    StratPool::setup(pool_uuid, datadevs, cachedevs, timestamp, &metadata, pool_einfo)
        .map(|(name, mut pool)| {
            if matches!(pool_name, MaybeInconsistent::Yes | MaybeInconsistent::No(None)) || MaybeInconsistent::No(Some(&name)) != pool_name.as_ref() || pool.blockdevs().iter().map(|(_, _, bd)| {
                bd.pool_name()
            }).fold(false, |acc, next| {
                match next {
                    Some(Some(name)) => {
                        if MaybeInconsistent::No(Some(name)) == pool_name.as_ref() {
                            acc
                        } else {
                            true
                        }
                    },
                    Some(None) => true,
                    None => false,
                }
            }) {
                if let Err(e) = pool.rename_pool(&name) {
                    warn!("Pool will not be able to be started by name; pool name metadata in LUKS2 token is not consistent across all devices: {}", e);
                }
            }
            (name, pool)
        })
        .map_err(|(err, bdas)| {
            (StratisError::Chained(
                format!(
                    "An attempt to set up pool with UUID {} from the assembled devices failed",
                    pool_uuid
                ),
                Box::new(err),
            ), bdas)
        })
}

/// Rollback an unlock operation for some or all devices of a pool that have been
/// unlocked prior to the failure occuring.
fn handle_unlock_rollback(causal_error: StratisError, handles: Vec<CryptHandle>) -> StratisError {
    for handle in handles {
        if let Err(e) = handle.deactivate() {
            warn!("Failed to roll back encrypted pool unlock; some previously locked encrypted devices may be left in an unlocked state");
            return StratisError::NoActionRollbackError {
                causal_error: Box::new(causal_error),
                rollback_error: Box::new(StratisError::Chained(
                    "Failed to roll back encrypted pool unlock; some previously locked encrypted devices may be left in an unlocked state".to_string(),
                    Box::new(e),
                )),
            };
        }
    }

    causal_error
}