[pbs-devel] [PATCH proxmox-backup v14 05/25] api: admin: add (un)mount endpoint for removable datastores

[Hannes Laimer <h.laimer@proxmox.com>]

Removable datastores can be mounted unless
 - they are already
 - their device is not present
For unmounting the maintenance mode is set to `unmount`,
which prohibits the starting of any new tasks envolving any
IO, this mode is unset either
 - on completion of the unmount
 - on abort of the unmount tasks
If the unmounting itself should fail, the maintenance mode stays in
place and requires manual intervention by unsetting it in the config
file directly. This is intentional, as unmounting should not fail,
and if it should the situation should be looked at.

Signed-off-by: Hannes Laimer <h.laimer@proxmox.com>
---
changes since v13:
 * improve logging
 * fix racy unmount
 * (manually) changing maintenance during unmount will prevent unmounting and
    result in failed unmount task

 src/api2/admin/datastore.rs | 294 ++++++++++++++++++++++++++++++++++--
 1 file changed, 283 insertions(+), 11 deletions(-)

diff --git a/src/api2/admin/datastore.rs b/src/api2/admin/datastore.rs
index 3b863c06b..85522345e 100644
--- a/src/api2/admin/datastore.rs
+++ b/src/api2/admin/datastore.rs
@@ -4,7 +4,7 @@ use std::collections::HashSet;
 use std::ffi::OsStr;
 use std::ops::Deref;
 use std::os::unix::ffi::OsStrExt;
-use std::path::PathBuf;
+use std::path::{Path, PathBuf};
 use std::sync::Arc;
 
 use anyhow::{bail, format_err, Error};
@@ -14,7 +14,7 @@ use hyper::{header, Body, Response, StatusCode};
 use serde::Deserialize;
 use serde_json::{json, Value};
 use tokio_stream::wrappers::ReceiverStream;
-use tracing::{info, warn};
+use tracing::{debug, info, warn};
 
 use proxmox_async::blocking::WrappedReaderStream;
 use proxmox_async::{io::AsyncChannelWriter, stream::AsyncReaderStream};
@@ -30,6 +30,7 @@ use proxmox_sys::fs::{
     file_read_firstline, file_read_optional_string, replace_file, CreateOptions,
 };
 use proxmox_time::CalendarEvent;
+use proxmox_worker_task::WorkerTaskContext;
 
 use pxar::accessor::aio::Accessor;
 use pxar::EntryKind;
@@ -38,13 +39,13 @@ use pbs_api_types::{
     print_ns_and_snapshot, print_store_and_ns, ArchiveType, Authid, BackupArchiveName,
     BackupContent, BackupGroupDeleteStats, BackupNamespace, BackupType, Counts, CryptMode,
     DataStoreConfig, DataStoreListItem, DataStoreStatus, GarbageCollectionJobStatus, GroupListItem,
-    JobScheduleStatus, KeepOptions, Operation, PruneJobOptions, SnapshotListItem,
-    SnapshotVerifyState, BACKUP_ARCHIVE_NAME_SCHEMA, BACKUP_ID_SCHEMA, BACKUP_NAMESPACE_SCHEMA,
-    BACKUP_TIME_SCHEMA, BACKUP_TYPE_SCHEMA, CATALOG_NAME, CLIENT_LOG_BLOB_NAME, DATASTORE_SCHEMA,
-    IGNORE_VERIFIED_BACKUPS_SCHEMA, MANIFEST_BLOB_NAME, MAX_NAMESPACE_DEPTH, NS_MAX_DEPTH_SCHEMA,
-    PRIV_DATASTORE_AUDIT, PRIV_DATASTORE_BACKUP, PRIV_DATASTORE_MODIFY, PRIV_DATASTORE_PRUNE,
-    PRIV_DATASTORE_READ, PRIV_DATASTORE_VERIFY, UPID, UPID_SCHEMA,
-    VERIFICATION_OUTDATED_AFTER_SCHEMA,
+    JobScheduleStatus, KeepOptions, MaintenanceMode, MaintenanceType, Operation, PruneJobOptions,
+    SnapshotListItem, SnapshotVerifyState, BACKUP_ARCHIVE_NAME_SCHEMA, BACKUP_ID_SCHEMA,
+    BACKUP_NAMESPACE_SCHEMA, BACKUP_TIME_SCHEMA, BACKUP_TYPE_SCHEMA, CATALOG_NAME,
+    CLIENT_LOG_BLOB_NAME, DATASTORE_SCHEMA, IGNORE_VERIFIED_BACKUPS_SCHEMA, MANIFEST_BLOB_NAME,
+    MAX_NAMESPACE_DEPTH, NS_MAX_DEPTH_SCHEMA, PRIV_DATASTORE_AUDIT, PRIV_DATASTORE_BACKUP,
+    PRIV_DATASTORE_MODIFY, PRIV_DATASTORE_PRUNE, PRIV_DATASTORE_READ, PRIV_DATASTORE_VERIFY, UPID,
+    UPID_SCHEMA, VERIFICATION_OUTDATED_AFTER_SCHEMA,
 };
 use pbs_client::pxar::{create_tar, create_zip};
 use pbs_config::CachedUserInfo;
@@ -59,8 +60,8 @@ use pbs_datastore::index::IndexFile;
 use pbs_datastore::manifest::BackupManifest;
 use pbs_datastore::prune::compute_prune_info;
 use pbs_datastore::{
-    check_backup_owner, task_tracking, BackupDir, BackupGroup, DataStore, LocalChunkReader,
-    StoreProgress,
+    check_backup_owner, ensure_datastore_is_mounted, task_tracking, BackupDir, BackupGroup,
+    DataStore, LocalChunkReader, StoreProgress,
 };
 use pbs_tools::json::required_string_param;
 use proxmox_rest_server::{formatter, WorkerTask};
@@ -2394,6 +2395,275 @@ pub async fn set_backup_owner(
     .await?
 }
 
+/// Here we
+///
+/// 1. mount the removable device to `<PBS_RUN_DIR>/mount/<RANDOM_UUID>`
+/// 2. bind mount `<PBS_RUN_DIR>/mount/<RANDOM_UUID>/<datastore.path>` to `/mnt/datastore/<datastore.name>`
+/// 3. unmount `<PBS_RUN_DIR>/mount/<RANDOM_UUID>`
+///
+/// leaving us with the datastore being mounted directly with its name under /mnt/datastore/...
+///
+/// The reason for the randomized device mounting paths is to avoid two tasks trying to mount to
+/// the same path, this is *very* unlikely since the device is only mounted really shortly, but
+/// technically possible.
+pub fn do_mount_device(datastore: DataStoreConfig) -> Result<(), Error> {
+    if let Some(uuid) = datastore.backing_device.as_ref() {
+        let mount_point = datastore.absolute_path();
+        if pbs_datastore::get_datastore_mount_status(&datastore) == Some(true) {
+            bail!("device is already mounted at '{}'", mount_point);
+        }
+        let tmp_mount_path = format!(
+            "{}/{:x}",
+            pbs_buildcfg::rundir!("/mount"),
+            proxmox_uuid::Uuid::generate()
+        );
+
+        let default_options = proxmox_sys::fs::CreateOptions::new();
+        proxmox_sys::fs::create_path(
+            &tmp_mount_path,
+            Some(default_options.clone()),
+            Some(default_options.clone()),
+        )?;
+
+        info!("temporarily mounting '{uuid}' to '{}'", tmp_mount_path);
+        crate::tools::disks::mount_by_uuid(uuid, Path::new(&tmp_mount_path))
+            .map_err(|e| format_err!("mounting to tmp path failed: {e}"))?;
+
+        let full_store_path = format!(
+            "{tmp_mount_path}/{}",
+            datastore.path.trim_start_matches('/')
+        );
+        let backup_user = pbs_config::backup_user()?;
+        let options = CreateOptions::new()
+            .owner(backup_user.uid)
+            .group(backup_user.gid);
+
+        proxmox_sys::fs::create_path(
+            &mount_point,
+            Some(default_options.clone()),
+            Some(options.clone()),
+        )
+        .map_err(|e| format_err!("creating mountpoint '{mount_point}' failed: {e}"))?;
+
+        // can't be created before it is mounted, so we have to do it here
+        proxmox_sys::fs::create_path(
+            &full_store_path,
+            Some(default_options.clone()),
+            Some(options.clone()),
+        )
+        .map_err(|e| format_err!("creating datastore path '{full_store_path}' failed: {e}"))?;
+
+        info!(
+            "bind mount '{}'({}) to '{}'",
+            datastore.name, datastore.path, mount_point
+        );
+        if let Err(err) =
+            crate::tools::disks::bind_mount(Path::new(&full_store_path), Path::new(&mount_point))
+        {
+            debug!("unmounting '{}'", tmp_mount_path);
+            let _ = crate::tools::disks::unmount_by_mountpoint(Path::new(&tmp_mount_path))
+                .inspect_err(|e| warn!("unmounting from tmp path '{tmp_mount_path} failed: {e}'"));
+            let _ = std::fs::remove_dir(std::path::Path::new(&tmp_mount_path))
+                .inspect_err(|e| warn!("removing tmp path '{tmp_mount_path} failed: {e}'"));
+            return Err(format_err!(
+                "Datastore '{}' cound not be mounted: {}.",
+                datastore.name,
+                err
+            ));
+        }
+
+        debug!("unmounting '{}'", tmp_mount_path);
+        let _ = crate::tools::disks::unmount_by_mountpoint(Path::new(&tmp_mount_path))
+            .map_err(|e| format_err!("unmounting from tmp path '{tmp_mount_path} failed: {e}'"));
+        let _ = std::fs::remove_dir(std::path::Path::new(&tmp_mount_path))
+            .map_err(|e| format_err!("removing tmp path '{tmp_mount_path} failed: {e}'"));
+
+        Ok(())
+    } else {
+        Err(format_err!(
+            "Datastore '{}' cannot be mounted because it is not removable.",
+            datastore.name
+        ))
+    }
+}
+
+#[api(
+    protected: true,
+    input: {
+        properties: {
+            store: {
+                schema: DATASTORE_SCHEMA,
+            },
+        }
+    },
+    returns: {
+        schema: UPID_SCHEMA,
+    },
+    access: {
+        permission: &Permission::Privilege(&["datastore", "{store}"], PRIV_DATASTORE_AUDIT, false),
+    },
+)]
+/// Mount removable datastore.
+pub fn mount(store: String, rpcenv: &mut dyn RpcEnvironment) -> Result<Value, Error> {
+    let (section_config, _digest) = pbs_config::datastore::config()?;
+    let datastore: DataStoreConfig = section_config.lookup("datastore", &store)?;
+
+    if datastore.backing_device.is_none() {
+        bail!("datastore '{store}' is not removable");
+    }
+
+    let auth_id: Authid = rpcenv.get_auth_id().unwrap().parse()?;
+    let to_stdout = rpcenv.env_type() == RpcEnvironmentType::CLI;
+
+    let upid = WorkerTask::new_thread(
+        "mount-device",
+        Some(store),
+        auth_id.to_string(),
+        to_stdout,
+        move |_worker| do_mount_device(datastore),
+    )?;
+
+    Ok(json!(upid))
+}
+
+fn expect_maintanance_unmounting(
+    store: &str,
+) -> Result<(pbs_config::BackupLockGuard, DataStoreConfig), Error> {
+    let lock = pbs_config::datastore::lock_config()?;
+    let (section_config, _digest) = pbs_config::datastore::config()?;
+    let store_config: DataStoreConfig = section_config.lookup("datastore", store)?;
+
+    if store_config
+        .get_maintenance_mode()
+        .map_or(true, |m| m.ty != MaintenanceType::Unmount)
+    {
+        bail!("maintenance mode is not 'Unmount'");
+    }
+
+    Ok((lock, store_config))
+}
+
+fn unset_maintenance(
+    _lock: pbs_config::BackupLockGuard,
+    mut config: DataStoreConfig,
+) -> Result<(), Error> {
+    let (mut section_config, _digest) = pbs_config::datastore::config()?;
+    config.maintenance_mode = None;
+    section_config.set_data(&config.name, "datastore", &config)?;
+    pbs_config::datastore::save_config(&section_config)?;
+    Ok(())
+}
+
+fn do_unmount_device(
+    datastore: DataStoreConfig,
+    worker: Option<&dyn WorkerTaskContext>,
+) -> Result<(), Error> {
+    if datastore.backing_device.is_none() {
+        bail!("can't unmount non-removable datastore");
+    }
+    let mount_point = datastore.absolute_path();
+
+    let mut active_operations = task_tracking::get_active_operations(&datastore.name)?;
+    let mut old_status = String::new();
+    let mut aborted = false;
+    while active_operations.read + active_operations.write > 0 {
+        if let Some(worker) = worker {
+            if worker.abort_requested() {
+                aborted = true;
+                break;
+            }
+            let status = format!(
+                "cannot unmount yet, still {} read and {} write operations active",
+                active_operations.read, active_operations.write
+            );
+            if status != old_status {
+                info!("{status}");
+                old_status = status;
+            }
+        }
+        std::thread::sleep(std::time::Duration::from_secs(1));
+        active_operations = task_tracking::get_active_operations(&datastore.name)?;
+    }
+
+    if aborted {
+        let _ = expect_maintanance_unmounting(&datastore.name)
+            .inspect_err(|e| warn!("maintenance mode was not as expected: {e}"))
+            .and_then(|(lock, config)| {
+                unset_maintenance(lock, config)
+                    .inspect_err(|e| warn!("could not reset maintenance mode: {e}"))
+            });
+        bail!("aborted, due to user request");
+    } else {
+        let (lock, config) = expect_maintanance_unmounting(&datastore.name)?;
+        crate::tools::disks::unmount_by_mountpoint(Path::new(&mount_point))?;
+        let _ = unset_maintenance(lock, config)
+            .inspect_err(|e| warn!("could not reset maintenance mode: {e}"));
+    }
+    Ok(())
+}
+
+#[api(
+    protected: true,
+    input: {
+        properties: {
+            store: { schema: DATASTORE_SCHEMA },
+        },
+    },
+    returns: {
+        schema: UPID_SCHEMA,
+    },
+    access: {
+        permission: &Permission::Privilege(&["datastore", "{store}"], PRIV_DATASTORE_MODIFY, true),
+    }
+)]
+/// Unmount a removable device that is associated with the datastore
+pub async fn unmount(store: String, rpcenv: &mut dyn RpcEnvironment) -> Result<Value, Error> {
+    let _lock = pbs_config::datastore::lock_config()?;
+    let (mut section_config, _digest) = pbs_config::datastore::config()?;
+    let mut datastore: DataStoreConfig = section_config.lookup("datastore", &store)?;
+
+    if datastore.backing_device.is_none() {
+        bail!("datastore '{store}' is not removable");
+    }
+
+    ensure_datastore_is_mounted(&datastore)?;
+
+    datastore.set_maintenance_mode(Some(MaintenanceMode {
+        ty: MaintenanceType::Unmount,
+        message: None,
+    }))?;
+    section_config.set_data(&store, "datastore", &datastore)?;
+    pbs_config::datastore::save_config(&section_config)?;
+
+    drop(_lock);
+
+    let auth_id: Authid = rpcenv.get_auth_id().unwrap().parse()?;
+    let to_stdout = rpcenv.env_type() == RpcEnvironmentType::CLI;
+
+    if let Ok(proxy_pid) = proxmox_rest_server::read_pid(pbs_buildcfg::PROXMOX_BACKUP_PROXY_PID_FN)
+    {
+        let sock = proxmox_daemon::command_socket::path_from_pid(proxy_pid);
+        let _ = proxmox_daemon::command_socket::send_raw(
+            sock,
+            &format!(
+                "{{\"command\":\"update-datastore-cache\",\"args\":\"{}\"}}\n",
+                &store
+            ),
+        )
+        .await;
+    }
+
+    let upid = WorkerTask::new_thread(
+        "unmount-device",
+        Some(store),
+        auth_id.to_string(),
+        to_stdout,
+        move |worker| do_unmount_device(datastore, Some(&worker)),
+    )?;
+
+    Ok(json!(upid))
+}
+
 #[sortable]
 const DATASTORE_INFO_SUBDIRS: SubdirMap = &[
     (
@@ -2432,6 +2702,7 @@ const DATASTORE_INFO_SUBDIRS: SubdirMap = &[
             .get(&API_METHOD_LIST_GROUPS)
             .delete(&API_METHOD_DELETE_GROUP),
     ),
+    ("mount", &Router::new().post(&API_METHOD_MOUNT)),
     (
         "namespace",
         // FIXME: move into datastore:: sub-module?!
@@ -2466,6 +2737,7 @@ const DATASTORE_INFO_SUBDIRS: SubdirMap = &[
             .delete(&API_METHOD_DELETE_SNAPSHOT),
     ),
     ("status", &Router::new().get(&API_METHOD_STATUS)),
+    ("unmount", &Router::new().post(&API_METHOD_UNMOUNT)),
     (
         "upload-backup-log",
         &Router::new().upload(&API_METHOD_UPLOAD_BACKUP_LOG),
-- 
2.39.5



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