From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id F38E641C76; Fri, 24 May 2024 18:55:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1716576957; cv=none; b=C/9XpInd+8S9yQVKSUj5qN7SnZ302IsHtrIh6KYvAfx+End0GnqVjH5G/Pq2Y3MgI6TTm2Q5kvwr+RYXRdjcWyMvtutkXyQ67K5F6eTBhtwv0SmnY38JhZmah7gXt8jEvFor0tSM6edYwWeYNiKYqH3pkQSJ6ZUXUZyXF6r6L0g= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1716576957; c=relaxed/simple; bh=YzLaJ0iMmmUvgOgOJn6peoHdRWTb2pH+XkvrahDGkLQ=; h=Date:To:From:Subject:Message-Id; b=VDqd3JbdDUpve/5FY84sRUVexzu8/PKQuN7HXet6KQxKUzgfj+rsV4SWzLZtj/ivaxkQYCTuvZAnd113e0obuCVIS5LO0d/S4aVT3rn8kOopiS8/4f9rYGnTAZJ2mMi72jwc0jZ53RZeWMd2Rx4wib+2gT78rP0MjwqqRU+HF9M= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=xHlUqxth; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="xHlUqxth" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 70AD5C2BBFC; Fri, 24 May 2024 18:55:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1716576956; bh=YzLaJ0iMmmUvgOgOJn6peoHdRWTb2pH+XkvrahDGkLQ=; h=Date:To:From:Subject:From; b=xHlUqxthyZoSZGcP1JGoVb5e0DBrz3CLbt31rrEJTzVCrc1iCeTekf7Lgy20PKPGz FZn46vMd51m1nh8fbNsADqFtoEaYM/ND9wt8fVE7ofpazZgU62kywndTcaIv2j6jkn OKLXdXYny8XG2Aju3KYd651IwzTOSagArOqp7r7I= Date: Fri, 24 May 2024 11:55:55 -0700 To: mm-commits@vger.kernel.org,stable@vger.kernel.org,sjb7183@psu.edu,konishi.ryusuke@gmail.com,akpm@linux-foundation.org From: Andrew Morton Subject: [merged mm-hotfixes-stable] nilfs2-fix-potential-hang-in-nilfs_detach_log_writer.patch removed from -mm tree Message-Id: <20240524185556.70AD5C2BBFC@smtp.kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The quilt patch titled Subject: nilfs2: fix potential hang in nilfs_detach_log_writer() has been removed from the -mm tree. Its filename was nilfs2-fix-potential-hang-in-nilfs_detach_log_writer.patch This patch was dropped because it was merged into the mm-hotfixes-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm ------------------------------------------------------ From: Ryusuke Konishi Subject: nilfs2: fix potential hang in nilfs_detach_log_writer() Date: Mon, 20 May 2024 22:26:21 +0900 Syzbot has reported a potential hang in nilfs_detach_log_writer() called during nilfs2 unmount. Analysis revealed that this is because nilfs_segctor_sync(), which synchronizes with the log writer thread, can be called after nilfs_segctor_destroy() terminates that thread, as shown in the call trace below: nilfs_detach_log_writer nilfs_segctor_destroy nilfs_segctor_kill_thread --> Shut down log writer thread flush_work nilfs_iput_work_func nilfs_dispose_list iput nilfs_evict_inode nilfs_transaction_commit nilfs_construct_segment (if inode needs sync) nilfs_segctor_sync --> Attempt to synchronize with log writer thread *** DEADLOCK *** Fix this issue by changing nilfs_segctor_sync() so that the log writer thread returns normally without synchronizing after it terminates, and by forcing tasks that are already waiting to complete once after the thread terminates. The skipped inode metadata flushout will then be processed together in the subsequent cleanup work in nilfs_segctor_destroy(). Link: https://lkml.kernel.org/r/20240520132621.4054-4-konishi.ryusuke@gmail.com Signed-off-by: Ryusuke Konishi Reported-by: syzbot+e3973c409251e136fdd0@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=e3973c409251e136fdd0 Tested-by: Ryusuke Konishi Cc: Cc: "Bai, Shuangpeng" Signed-off-by: Andrew Morton --- fs/nilfs2/segment.c | 21 ++++++++++++++++++--- 1 file changed, 18 insertions(+), 3 deletions(-) --- a/fs/nilfs2/segment.c~nilfs2-fix-potential-hang-in-nilfs_detach_log_writer +++ a/fs/nilfs2/segment.c @@ -2190,6 +2190,14 @@ static int nilfs_segctor_sync(struct nil for (;;) { set_current_state(TASK_INTERRUPTIBLE); + /* + * Synchronize only while the log writer thread is alive. + * Leave flushing out after the log writer thread exits to + * the cleanup work in nilfs_segctor_destroy(). + */ + if (!sci->sc_task) + break; + if (atomic_read(&wait_req.done)) { err = wait_req.err; break; @@ -2205,7 +2213,7 @@ static int nilfs_segctor_sync(struct nil return err; } -static void nilfs_segctor_wakeup(struct nilfs_sc_info *sci, int err) +static void nilfs_segctor_wakeup(struct nilfs_sc_info *sci, int err, bool force) { struct nilfs_segctor_wait_request *wrq, *n; unsigned long flags; @@ -2213,7 +2221,7 @@ static void nilfs_segctor_wakeup(struct spin_lock_irqsave(&sci->sc_wait_request.lock, flags); list_for_each_entry_safe(wrq, n, &sci->sc_wait_request.head, wq.entry) { if (!atomic_read(&wrq->done) && - nilfs_cnt32_ge(sci->sc_seq_done, wrq->seq)) { + (force || nilfs_cnt32_ge(sci->sc_seq_done, wrq->seq))) { wrq->err = err; atomic_set(&wrq->done, 1); } @@ -2362,7 +2370,7 @@ static void nilfs_segctor_notify(struct if (mode == SC_LSEG_SR) { sci->sc_state &= ~NILFS_SEGCTOR_COMMIT; sci->sc_seq_done = sci->sc_seq_accepted; - nilfs_segctor_wakeup(sci, err); + nilfs_segctor_wakeup(sci, err, false); sci->sc_flush_request = 0; } else { if (mode == SC_FLUSH_FILE) @@ -2746,6 +2754,13 @@ static void nilfs_segctor_destroy(struct || sci->sc_seq_request != sci->sc_seq_done); spin_unlock(&sci->sc_state_lock); + /* + * Forcibly wake up tasks waiting in nilfs_segctor_sync(), which can + * be called from delayed iput() via nilfs_evict_inode() and can race + * with the above log writer thread termination. + */ + nilfs_segctor_wakeup(sci, 0, true); + if (flush_work(&sci->sc_iput_work)) flag = true; _ Patches currently in -mm which might be from konishi.ryusuke@gmail.com are