From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from firstgate.proxmox.com (firstgate.proxmox.com [212.224.123.68]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by lists.proxmox.com (Postfix) with ESMTPS id C2A36CF2B for ; Wed, 13 Apr 2022 11:12:29 +0200 (CEST) Received: from firstgate.proxmox.com (localhost [127.0.0.1]) by firstgate.proxmox.com (Proxmox) with ESMTP id B5E05207A9 for ; Wed, 13 Apr 2022 11:11:59 +0200 (CEST) Received: from proxmox-new.maurer-it.com (proxmox-new.maurer-it.com [94.136.29.106]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by firstgate.proxmox.com (Proxmox) with ESMTPS id 55D582076B for ; Wed, 13 Apr 2022 11:11:57 +0200 (CEST) Received: from proxmox-new.maurer-it.com (localhost.localdomain [127.0.0.1]) by proxmox-new.maurer-it.com (Proxmox) with ESMTP id 2B879414B1 for ; Wed, 13 Apr 2022 11:11:57 +0200 (CEST) From: Stefan Sterz To: pbs-devel@lists.proxmox.com Date: Wed, 13 Apr 2022 11:11:49 +0200 Message-Id: <20220413091151.150019-3-s.sterz@proxmox.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20220413091151.150019-1-s.sterz@proxmox.com> References: <20220413091151.150019-1-s.sterz@proxmox.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-SPAM-LEVEL: Spam detection results: 0 AWL -0.022 Adjusted score from AWL reputation of From: address BAYES_00 -1.9 Bayes spam probability is 0 to 1% KAM_DMARC_STATUS 0.01 Test Rule for DKIM or SPF Failure with Strict Alignment SPF_HELO_NONE 0.001 SPF: HELO does not publish an SPF Record SPF_PASS -0.001 SPF: sender matches SPF record T_SCC_BODY_TEXT_LINE -0.01 - Subject: [pbs-devel] [PATCH proxmox-backup v2 2/4] fix #3935: datastore/api/backup: move datastore locking to '/run' X-BeenThere: pbs-devel@lists.proxmox.com X-Mailman-Version: 2.1.29 Precedence: list List-Id: Proxmox Backup Server development discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 13 Apr 2022 09:12:29 -0000 to avoid issues when removing a group or snapshot directory where two threads hold a lock to the same directory, move locking to the tmpfs backed '/run' directory and use a flat file structure. also adds double stat'ing to make it possible to remove locks without certain race condition issues. Signed-off-by: Stefan Sterz --- pbs-config/src/lib.rs | 7 ++ pbs-datastore/src/datastore.rs | 126 +++++++++++++++++++++------ pbs-datastore/src/snapshot_reader.rs | 24 ++++- src/api2/backup/environment.rs | 4 +- src/backup/verify.rs | 4 +- 5 files changed, 131 insertions(+), 34 deletions(-) diff --git a/pbs-config/src/lib.rs b/pbs-config/src/lib.rs index 118030bc..81a7b243 100644 --- a/pbs-config/src/lib.rs +++ b/pbs-config/src/lib.rs @@ -21,6 +21,7 @@ pub use config_version_cache::ConfigVersionCache; use anyhow::{format_err, Error}; use nix::unistd::{Gid, Group, Uid, User}; +use std::os::unix::prelude::AsRawFd; pub use pbs_buildcfg::{BACKUP_USER_NAME, BACKUP_GROUP_NAME}; @@ -46,6 +47,12 @@ pub fn backup_group() -> Result { pub struct BackupLockGuard(Option); +impl AsRawFd for BackupLockGuard { + fn as_raw_fd(&self) -> i32 { + self.0.as_ref().map_or(-1, |f| f.as_raw_fd()) + } +} + #[doc(hidden)] /// Note: do not use for production code, this is only intended for tests pub unsafe fn create_mocked_lock() -> BackupLockGuard { diff --git a/pbs-datastore/src/datastore.rs b/pbs-datastore/src/datastore.rs index 3895688d..92d544e5 100644 --- a/pbs-datastore/src/datastore.rs +++ b/pbs-datastore/src/datastore.rs @@ -1,5 +1,6 @@ use std::collections::{HashSet, HashMap}; use std::io::{self, Write}; +use std::os::unix::prelude::AsRawFd; use std::path::{Path, PathBuf}; use std::sync::{Arc, Mutex}; use std::convert::TryFrom; @@ -11,14 +12,13 @@ use lazy_static::lazy_static; use proxmox_schema::ApiType; -use proxmox_sys::fs::{ - file_read_optional_string, lock_dir_noblock, lock_dir_noblock_shared, replace_file, - CreateOptions, DirLockGuard, -}; +use proxmox_sys::fs::{file_read_optional_string, replace_file, CreateOptions}; use proxmox_sys::process_locker::ProcessLockSharedGuard; use proxmox_sys::WorkerTaskContext; use proxmox_sys::{task_log, task_warn}; +use proxmox_sys::systemd::escape_unit; + use pbs_api_types::{ UPID, DataStoreConfig, Authid, GarbageCollectionStatus, HumanByte, ChunkOrder, DatastoreTuning, Operation, @@ -42,6 +42,8 @@ lazy_static! { static ref DATASTORE_MAP: Mutex>> = Mutex::new(HashMap::new()); } +pub const DATASTORE_LOCKS_DIR: &str = "/run/proxmox-backup/locks"; + /// checks if auth_id is owner, or, if owner is a token, if /// auth_id is the user of the token pub fn check_backup_owner( @@ -368,6 +370,8 @@ impl DataStore { err, ) })?; + + let _ = std::fs::remove_file( self.group_lock_path(backup_group)); } Ok(removed_all) @@ -404,6 +408,8 @@ impl DataStore { let _ = std::fs::remove_file(path); } + let _ = std::fs::remove_file(self.snapshot_lock_path(backup_dir)); + Ok(()) } @@ -479,7 +485,7 @@ impl DataStore { &self, backup_group: &BackupGroup, auth_id: &Authid, - ) -> Result<(Authid, DirLockGuard), Error> { + ) -> Result<(Authid, BackupLockGuard), Error> { // create intermediate path first: let mut full_path = self.base_path(); full_path.push(backup_group.backup_type()); @@ -508,7 +514,7 @@ impl DataStore { /// /// The BackupGroup directory needs to exist. pub fn create_locked_backup_dir(&self, backup_dir: &BackupDir) - -> Result<(PathBuf, bool, DirLockGuard), Error> + -> Result<(PathBuf, bool, BackupLockGuard), Error> { let relative_path = backup_dir.relative_path(); let mut full_path = self.base_path(); @@ -1002,30 +1008,96 @@ impl DataStore { Ok(chunk_list) } - /// Lock a snapshot exclusively - pub fn lock_snapshot(&self, backup_dir: &BackupDir) -> Result { - lock_dir_noblock( - &self.snapshot_path(backup_dir), - "snapshot", - "possibly running or in use", - ) + /// Encodes a string so it can be used as a lock file name. + /// + /// The first 64 characters will be the sha256 hash of `path` then + /// a hyphen followed by up to 100 characters of the unit encoded + /// version of `path`. + fn lock_file_name_helper(&self, path: &str) -> String { + let enc = escape_unit(path, true); + let from = enc.len().checked_sub(100).unwrap_or(0); + let hash = hex::encode(openssl::sha::sha256(path.as_bytes())); + + format!("{}-{}", hash, enc[from..].to_string()) + } + + /// Returns a file name for locking a snapshot. + /// + /// The lock file will be located in: + /// `${DATASTORE_LOCKS_DIR}/${datastore name}/${lock_file_name_helper(rpath)}` + /// where `rpath` is the relative path of the snapshot. + fn snapshot_lock_path(&self, backup_dir: &BackupDir) -> PathBuf { + let path = Path::new(DATASTORE_LOCKS_DIR).join(self.name()); + + let rpath = format!( + "{}/{}/{}", + backup_dir.group().backup_type(), + backup_dir.group().backup_id(), + backup_dir.backup_time_string(), + ); + + path.join(self.lock_file_name_helper(&rpath)) + } + + /// Returns a file name for locking a group. + /// + /// The lock file will be located in: + /// `${DATASTORE_LOCKS_DIR}/${datastore name}/${lock_file_name_helper(rpath)}` + /// where `rpath` is the relative path of the group. + fn group_lock_path(&self, group: &BackupGroup) -> PathBuf { + let path = Path::new(DATASTORE_LOCKS_DIR).join(self.name()); + + let rpath = format!("{}/{}", group.backup_type(), group.backup_id()); + + path.join(self.lock_file_name_helper(&rpath)) + } + + /// Helps implement the double stat'ing procedure. It avoids + /// certain race conditions upon lock deletion. + /// + /// It also creates the base directory for lock files. + fn lock_helper(&self, path: &std::path::Path, lock_fn: F) -> Result + where + F: Fn(&std::path::Path) -> Result, + { + let lock_dir = Path::new(DATASTORE_LOCKS_DIR).join(self.name()); + std::fs::create_dir_all(&lock_dir)?; + + let lock = lock_fn(path)?; + + let stat = nix::sys::stat::fstat(lock.as_raw_fd())?.st_ino; + + if nix::sys::stat::stat(path).map_or(true, |st| stat != st.st_ino) { + bail!("could not acquire lock, another thread modified the lock file"); + } + + Ok(lock) + } + + /// Locks a snapshot exclusively. + pub fn lock_snapshot(&self, backup_dir: &BackupDir) -> Result { + self.lock_helper(&self.snapshot_lock_path(backup_dir), |p| { + open_backup_lockfile(p, Some(Duration::from_secs(0)), true).map_err(|err| { + format_err!("unable to acquire snapshot lock {:?} - {}", &p, err) + }) + }) } - /// Acquire a shared lock on a snapshot - pub fn lock_snapshot_shared(&self, backup_dir: &BackupDir) -> Result { - lock_dir_noblock_shared( - &self.snapshot_path(backup_dir), - "snapshot", - "possibly running or in use", - ) + /// Acquires a shared lock on a snapshot. + pub fn lock_snapshot_shared(&self, backup_dir: &BackupDir) -> Result { + self.lock_helper(&self.snapshot_lock_path(backup_dir), |p| { + open_backup_lockfile(p, Some(Duration::from_secs(0)), false).map_err(|err| { + format_err!("unable to acquire shared snapshot lock {:?} - {}", &p, err) + }) + }) } - /// Lock a group exclusively - pub fn lock_group(&self, group: &BackupGroup) -> Result { - lock_dir_noblock( - &self.group_path(group), - "backup group", - "possible running backup", - ) + /// Locks a group exclusively. + pub fn lock_group(&self, group: &BackupGroup) -> Result { + self.lock_helper(&self.group_lock_path(group), |p| { + open_backup_lockfile(p, Some(Duration::from_secs(0)), true).map_err(|err| { + format_err!("unable to acquire backup group lock {:?} - {}", &p, err) + }) + }) } } diff --git a/pbs-datastore/src/snapshot_reader.rs b/pbs-datastore/src/snapshot_reader.rs index 0eddac14..7fde3238 100644 --- a/pbs-datastore/src/snapshot_reader.rs +++ b/pbs-datastore/src/snapshot_reader.rs @@ -3,8 +3,11 @@ use std::sync::Arc; use std::os::unix::io::{AsRawFd, FromRawFd}; use std::fs::File; -use anyhow::{bail, Error}; +use anyhow::{bail, format_err, Error}; use nix::dir::Dir; +use nix::sys::stat::Mode; +use nix::fcntl::OFlag; +use pbs_config::BackupLockGuard; use crate::backup_info::BackupDir; use crate::index::IndexFile; @@ -22,13 +25,22 @@ pub struct SnapshotReader { datastore_name: String, file_list: Vec, locked_dir: Dir, + + // while this is never read, the lock needs to be kept until the + // reader is dropped to ensure valid locking semantics + _lock: BackupLockGuard, } impl SnapshotReader { /// Lock snapshot, reads the manifest and returns a new instance pub fn new(datastore: Arc, snapshot: BackupDir) -> Result { - let locked_dir = datastore.lock_snapshot_shared(&snapshot)?; + let lock = datastore.lock_snapshot_shared(&snapshot)?; + + let path = datastore.snapshot_path(&snapshot); + + let locked_dir = Dir::open(&path, OFlag::O_RDONLY, Mode::empty()) + .map_err(|err| format_err!("unable to open snapshot directory {:?} - {}", path, err))?; let datastore_name = datastore.name().to_string(); @@ -50,7 +62,13 @@ impl SnapshotReader { file_list.push(CLIENT_LOG_BLOB_NAME.to_string()); } - Ok(Self { snapshot, datastore_name, file_list, locked_dir }) + Ok(Self { + snapshot, + datastore_name, + file_list, + locked_dir, + _lock: lock, + }) } /// Return the snapshot directory diff --git a/src/api2/backup/environment.rs b/src/api2/backup/environment.rs index 3e23840f..b4557d42 100644 --- a/src/api2/backup/environment.rs +++ b/src/api2/backup/environment.rs @@ -1,7 +1,7 @@ use anyhow::{bail, format_err, Error}; +use pbs_config::BackupLockGuard; use std::sync::{Arc, Mutex}; use std::collections::HashMap; -use nix::dir::Dir; use ::serde::{Serialize}; use serde_json::{json, Value}; @@ -501,7 +501,7 @@ impl BackupEnvironment { /// If verify-new is set on the datastore, this will run a new verify task /// for the backup. If not, this will return and also drop the passed lock /// immediately. - pub fn verify_after_complete(&self, snap_lock: Dir) -> Result<(), Error> { + pub fn verify_after_complete(&self, snap_lock: BackupLockGuard) -> Result<(), Error> { self.ensure_finished()?; if !self.datastore.verify_new() { diff --git a/src/backup/verify.rs b/src/backup/verify.rs index eea0e15d..f4375daa 100644 --- a/src/backup/verify.rs +++ b/src/backup/verify.rs @@ -1,4 +1,4 @@ -use nix::dir::Dir; +use pbs_config::BackupLockGuard; use std::collections::HashSet; use std::sync::atomic::{AtomicUsize, Ordering}; use std::sync::{Arc, Mutex}; @@ -324,7 +324,7 @@ pub fn verify_backup_dir_with_lock( backup_dir: &BackupDir, upid: UPID, filter: Option<&dyn Fn(&BackupManifest) -> bool>, - _snap_lock: Dir, + _snap_lock: BackupLockGuard, ) -> Result { let manifest = match verify_worker.datastore.load_manifest(backup_dir) { Ok((manifest, _)) => manifest, -- 2.30.2