From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from firstgate.proxmox.com (firstgate.proxmox.com [212.224.123.68]) by lore.proxmox.com (Postfix) with ESMTPS id 3A3FB1FF176 for ; Fri, 24 Jan 2025 13:46:57 +0100 (CET) Received: from firstgate.proxmox.com (localhost [127.0.0.1]) by firstgate.proxmox.com (Proxmox) with ESMTP id 1532428CA5; Fri, 24 Jan 2025 13:46:52 +0100 (CET) From: Christian Ebner To: pbs-devel@lists.proxmox.com Date: Fri, 24 Jan 2025 13:46:35 +0100 Message-Id: <20250124124635.291858-1-c.ebner@proxmox.com> X-Mailer: git-send-email 2.39.5 MIME-Version: 1.0 X-SPAM-LEVEL: Spam detection results: 0 AWL 0.035 Adjusted score from AWL reputation of From: address BAYES_00 -1.9 Bayes spam probability is 0 to 1% DMARC_MISSING 0.1 Missing DMARC policy KAM_DMARC_STATUS 0.01 Test Rule for DKIM or SPF Failure with Strict Alignment RCVD_IN_VALIDITY_CERTIFIED_BLOCKED 0.001 ADMINISTRATOR NOTICE: The query to Validity was blocked. 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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 v5 proxmox-backup] client: pxar: fix race in pxar backup stream 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: , Reply-To: Proxmox Backup Server development discussion Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: pbs-devel-bounces@lists.proxmox.com Sender: "pbs-devel" Fixes a race condition where the backup upload stream can miss an error returned by pxar::create_archive, because the error state is only set after the backup stream was already polled. On instantiation, `PxarBackupStream` spawns a future handling the pxar archive creation, which sends the encoded pxar archive stream (or streams in case of split archives) through a channel, received by the pxar backup stream on polling. In case this channel is closed as signaled by returning an error, the poll logic will propagate an eventual error occurred during pxar creation by taking it from the `PxarBackupStream`. As this error might not have been set just yet, this can lead to incorrectly terminating a backup snapshot with success, eventhough an error occurred. To fix this, introduce a dedicated notifier for each stream instance and wait for the archiver to signal it has finished via this notification channel. In addition, extend the `PxarBackupStream` by a `finished` flag to allow early return on subsequent polls, which would otherwise block, waiting for a new notification. In case of premature termination of the pxar backup stream, no additional measures have to been taken, as the abort handle already terminates the archive creation. Signed-off-by: Christian Ebner --- Changes since version 4 (thanks a lot Fabian for comments!): - Drop unneeded shared state, only store error - Use dedicated notification channel instances per stream, so each channel gets notified for sure. - Use `finished` flag per `PxarBackupStream` instance, allowing on early return if the archiver finish has already been seen, avoiding to block again on awaiting a notification. pbs-client/src/pxar_backup_stream.rs | 34 +++++++++++++++++++++++++--- 1 file changed, 31 insertions(+), 3 deletions(-) diff --git a/pbs-client/src/pxar_backup_stream.rs b/pbs-client/src/pxar_backup_stream.rs index 2bfb5cf29..1303e8503 100644 --- a/pbs-client/src/pxar_backup_stream.rs +++ b/pbs-client/src/pxar_backup_stream.rs @@ -11,6 +11,7 @@ use futures::stream::Stream; use nix::dir::Dir; use nix::fcntl::OFlag; use nix::sys::stat::Mode; +use tokio::sync::Notify; use proxmox_async::blocking::TokioWriterAdapter; use proxmox_io::StdChannelWriter; @@ -31,6 +32,8 @@ pub struct PxarBackupStream { pub suggested_boundaries: Option>, handle: Option, error: Arc>>, + finished: bool, + archiver_finished_notification: Arc, } impl Drop for PxarBackupStream { @@ -80,6 +83,10 @@ impl PxarBackupStream { let error = Arc::new(Mutex::new(None)); let error2 = Arc::clone(&error); + let stream_notifier = Arc::new(Notify::new()); + let stream_notification_receiver = stream_notifier.clone(); + let payload_stream_notifier = Arc::new(Notify::new()); + let payload_stream_notification_receiver = payload_stream_notifier.clone(); let handler = async move { if let Err(err) = crate::pxar::create_archive( dir, @@ -101,6 +108,10 @@ impl PxarBackupStream { let mut error = error2.lock().unwrap(); *error = Some(err); } + + // Notify upload streams that archiver is finished (with or without error) + stream_notifier.notify_one(); + payload_stream_notifier.notify_one(); }; let (handle, registration) = AbortHandle::new_pair(); @@ -112,6 +123,8 @@ impl PxarBackupStream { suggested_boundaries: None, handle: Some(handle.clone()), error: Arc::clone(&error), + finished: false, + archiver_finished_notification: stream_notification_receiver, }; let backup_payload_stream = payload_rx.map(|rx| Self { @@ -119,6 +132,8 @@ impl PxarBackupStream { suggested_boundaries: suggested_boundaries_rx, handle: Some(handle), error, + finished: false, + archiver_finished_notification: payload_stream_notification_receiver, }); Ok((backup_stream, backup_payload_stream)) @@ -141,18 +156,31 @@ impl Stream for PxarBackupStream { type Item = Result, Error>; fn poll_next(self: Pin<&mut Self>, _cx: &mut Context) -> Poll> { + let this = self.get_mut(); + if this.finished { + // Channel has already been finished and eventual errors propagated, + // early return to avoid blocking on further archiver finished notifications + // by subsequent polls. + return Poll::Ready(None); + } { // limit lock scope - let mut error = self.error.lock().unwrap(); + let mut error = this.error.lock().unwrap(); if let Some(err) = error.take() { return Poll::Ready(Some(Err(err))); } } - match proxmox_async::runtime::block_in_place(|| self.rx.as_ref().unwrap().recv()) { + match proxmox_async::runtime::block_in_place(|| this.rx.as_ref().unwrap().recv()) { Ok(data) => Poll::Ready(Some(data)), Err(_) => { - let mut error = self.error.lock().unwrap(); + // Wait for archiver to finish + proxmox_async::runtime::block_on(this.archiver_finished_notification.notified()); + // Never block for archiver finished notification on subsequent calls. + // Eventual error will already have been propagated. + this.finished = true; + + let mut error = this.error.lock().unwrap(); if let Some(err) = error.take() { return Poll::Ready(Some(Err(err))); } -- 2.39.5 _______________________________________________ pbs-devel mailing list pbs-devel@lists.proxmox.com https://lists.proxmox.com/cgi-bin/mailman/listinfo/pbs-devel