From: Stefan Reiter Date: Fri, 16 Oct 2020 07:31:12 +0000 (+0200) Subject: datastore: add manifest locking X-Git-Tag: v0.9.2~112 X-Git-Url: https://git.proxmox.com/?a=commitdiff_plain;h=1a374fcfd6274f3e5403501d89f20532a7c94aca;p=proxmox-backup.git datastore: add manifest locking Avoid races when updating manifest data by flocking a lock file. update_manifest is used to ensure updates always happen with the lock held. Snapshot deletion also acquires the lock, so it cannot interfere with an outstanding manifest write. Signed-off-by: Stefan Reiter --- diff --git a/src/api2/admin/datastore.rs b/src/api2/admin/datastore.rs index de39cd1b..4f15c1cd 100644 --- a/src/api2/admin/datastore.rs +++ b/src/api2/admin/datastore.rs @@ -1481,11 +1481,9 @@ fn set_notes( let allowed = (user_privs & PRIV_DATASTORE_READ) != 0; if !allowed { check_backup_owner(&datastore, backup_dir.group(), &userid)?; } - let (mut manifest, _) = datastore.load_manifest(&backup_dir)?; - - manifest.unprotected["notes"] = notes.into(); - - datastore.store_manifest(&backup_dir, manifest)?; + datastore.update_manifest(&backup_dir,|manifest| { + manifest.unprotected["notes"] = notes.into(); + }).map_err(|err| format_err!("unable to update manifest blob - {}", err))?; Ok(()) } diff --git a/src/api2/backup/environment.rs b/src/api2/backup/environment.rs index f00c2cd3..c4f166df 100644 --- a/src/api2/backup/environment.rs +++ b/src/api2/backup/environment.rs @@ -472,16 +472,11 @@ impl BackupEnvironment { bail!("backup does not contain valid files (file count == 0)"); } - // check manifest - let (mut manifest, _) = self.datastore.load_manifest(&self.backup_dir) - .map_err(|err| format_err!("unable to load manifest blob - {}", err))?; - + // check for valid manifest and store stats let stats = serde_json::to_value(state.backup_stat)?; - - manifest.unprotected["chunk_upload_stats"] = stats; - - self.datastore.store_manifest(&self.backup_dir, manifest) - .map_err(|err| format_err!("unable to store manifest blob - {}", err))?; + self.datastore.update_manifest(&self.backup_dir, |manifest| { + manifest.unprotected["chunk_upload_stats"] = stats; + }).map_err(|err| format_err!("unable to update manifest blob - {}", err))?; if let Some(base) = &self.last_backup { let path = self.datastore.snapshot_path(&base.backup_dir); diff --git a/src/backup/datastore.rs b/src/backup/datastore.rs index 9bd1b769..46039576 100644 --- a/src/backup/datastore.rs +++ b/src/backup/datastore.rs @@ -3,17 +3,19 @@ use std::io::{self, Write}; use std::path::{Path, PathBuf}; use std::sync::{Arc, Mutex}; use std::convert::TryFrom; +use std::time::Duration; +use std::fs::File; use anyhow::{bail, format_err, Error}; use lazy_static::lazy_static; -use proxmox::tools::fs::{replace_file, CreateOptions}; +use proxmox::tools::fs::{replace_file, CreateOptions, open_file_locked}; use super::backup_info::{BackupGroup, BackupDir}; use super::chunk_store::ChunkStore; use super::dynamic_index::{DynamicIndexReader, DynamicIndexWriter}; use super::fixed_index::{FixedIndexReader, FixedIndexWriter}; -use super::manifest::{MANIFEST_BLOB_NAME, CLIENT_LOG_BLOB_NAME, BackupManifest}; +use super::manifest::{MANIFEST_BLOB_NAME, MANIFEST_LOCK_NAME, CLIENT_LOG_BLOB_NAME, BackupManifest}; use super::index::*; use super::{DataBlob, ArchiveType, archive_type}; use crate::config::datastore; @@ -231,9 +233,10 @@ impl DataStore { let full_path = self.snapshot_path(backup_dir); - let _guard; + let (_guard, _manifest_guard); if !force { _guard = lock_dir_noblock(&full_path, "snapshot", "possibly running or in use")?; + _manifest_guard = self.lock_manifest(backup_dir); } log::info!("removing backup snapshot {:?}", full_path); @@ -629,8 +632,27 @@ impl DataStore { digest_str, err, )) - } + } + + fn lock_manifest( + &self, + backup_dir: &BackupDir, + ) -> Result { + let mut path = self.base_path(); + path.push(backup_dir.relative_path()); + path.push(&MANIFEST_LOCK_NAME); + + // update_manifest should never take a long time, so if someone else has + // the lock we can simply block a bit and should get it soon + open_file_locked(&path, Duration::from_secs(5), true) + .map_err(|err| { + format_err!( + "unable to acquire manifest lock {:?} - {}", &path, err + ) + }) + } + /// Load the manifest without a lock. Must not be written back. pub fn load_manifest( &self, backup_dir: &BackupDir, @@ -641,11 +663,19 @@ impl DataStore { Ok((manifest, raw_size)) } - pub fn store_manifest( + /// Update the manifest of the specified snapshot. Never write a manifest directly, + /// only use this method - anything else may break locking guarantees. + pub fn update_manifest( &self, backup_dir: &BackupDir, - manifest: BackupManifest, + update_fn: impl FnOnce(&mut BackupManifest), ) -> Result<(), Error> { + + let _guard = self.lock_manifest(backup_dir)?; + let (mut manifest, _) = self.load_manifest(&backup_dir)?; + + update_fn(&mut manifest); + let manifest = serde_json::to_value(manifest)?; let manifest = serde_json::to_string_pretty(&manifest)?; let blob = DataBlob::encode(manifest.as_bytes(), None, true)?; @@ -655,6 +685,7 @@ impl DataStore { path.push(backup_dir.relative_path()); path.push(MANIFEST_BLOB_NAME); + // atomic replace invalidates flock - no other writes past this point! replace_file(&path, raw_data, CreateOptions::new())?; Ok(()) diff --git a/src/backup/manifest.rs b/src/backup/manifest.rs index 609cc998..51980a07 100644 --- a/src/backup/manifest.rs +++ b/src/backup/manifest.rs @@ -8,6 +8,7 @@ use ::serde::{Deserialize, Serialize}; use crate::backup::{BackupDir, CryptMode, CryptConfig}; pub const MANIFEST_BLOB_NAME: &str = "index.json.blob"; +pub const MANIFEST_LOCK_NAME: &str = ".index.json.lck"; pub const CLIENT_LOG_BLOB_NAME: &str = "client.log.blob"; mod hex_csum { diff --git a/src/backup/verify.rs b/src/backup/verify.rs index 05b6ba86..ea3fa760 100644 --- a/src/backup/verify.rs +++ b/src/backup/verify.rs @@ -300,7 +300,7 @@ pub fn verify_backup_dir( return Ok(true); } - let mut manifest = match datastore.load_manifest(&backup_dir) { + let manifest = match datastore.load_manifest(&backup_dir) { Ok((manifest, _)) => manifest, Err(err) => { task_log!( @@ -367,9 +367,10 @@ pub fn verify_backup_dir( state: verify_result, upid, }; - manifest.unprotected["verify_state"] = serde_json::to_value(verify_state)?; - datastore.store_manifest(&backup_dir, manifest) - .map_err(|err| format_err!("unable to store manifest blob - {}", err))?; + let verify_state = serde_json::to_value(verify_state)?; + datastore.update_manifest(&backup_dir, |manifest| { + manifest.unprotected["verify_state"] = verify_state; + }).map_err(|err| format_err!("unable to update manifest blob - {}", err))?; Ok(error_count == 0) }