From patchwork Tue Jul 30 11:24:56 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Thomas Gleixner X-Patchwork-Id: 1138940 Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=linux-ext4-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=linutronix.de Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 45yb1w5mxDz9s3Z for ; Tue, 30 Jul 2019 22:08:52 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729279AbfG3MIr (ORCPT ); Tue, 30 Jul 2019 08:08:47 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:56565 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727561AbfG3MIr (ORCPT ); Tue, 30 Jul 2019 08:08:47 -0400 Received: from localhost ([127.0.0.1] helo=nanos.tec.linutronix.de) by Galois.linutronix.de with esmtp (Exim 4.80) (envelope-from ) id 1hsQuN-0006QO-69; Tue, 30 Jul 2019 14:07:11 +0200 Message-Id: <20190730120321.489374435@linutronix.de> User-Agent: quilt/0.65 Date: Tue, 30 Jul 2019 13:24:56 +0200 From: Thomas Gleixner To: LKML Cc: Peter Zijlstra , Ingo Molnar , Sebastian Siewior , Anna-Maria Gleixner , Steven Rostedt , Julia Cartwright , linux-ext4@vger.kernel.org, "Theodore Tso" , Matthew Wilcox , Jan Kara , Alexander Viro , linux-fsdevel@vger.kernel.org Subject: [patch 4/4] fs: jbd/jbd2: Substitute BH locks for RT and lock debugging References: <20190730112452.871257694@linutronix.de> MIME-Version: 1.0 Sender: linux-ext4-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org Bit spinlocks are problematic if PREEMPT_RT is enabled. They disable preemption, which is undesired for latency reasons and breaks when regular spinlocks are taken within the bit_spinlock locked region because regular spinlocks are converted to 'sleeping spinlocks' on RT. Substitute the BH_State and BH_JournalHead bit spinlocks with regular spinlock for PREEMPT_RT enabled kernels. Bit spinlocks are also not covered by lock debugging, e.g. lockdep. With the spinlock substitution in place, they can be exposed via CONFIG_DEBUG_BIT_SPINLOCKS. Originally-by: Steven Rostedt Signed-off-by: Thomas Gleixner Cc: linux-ext4@vger.kernel.org Cc: "Theodore Ts'o" Cc: Matthew Wilcox Cc: Jan Kara --- include/linux/buffer_head.h | 8 ++++++++ include/linux/jbd2.h | 36 ++++++++++++++++++++++++++++++++++++ 2 files changed, 44 insertions(+) --- a/include/linux/buffer_head.h +++ b/include/linux/buffer_head.h @@ -79,6 +79,10 @@ struct buffer_head { #if defined(CONFIG_PREEMPT_RT) || defined(CONFIG_DEBUG_BIT_SPINLOCKS) spinlock_t b_uptodate_lock; +# if IS_ENABLED(CONFIG_JBD2) + spinlock_t b_state_lock; + spinlock_t b_journal_head_lock; +# endif #endif }; @@ -101,6 +105,10 @@ bh_uptodate_unlock_irqrestore(struct buf static inline void buffer_head_init_locks(struct buffer_head *bh) { spin_lock_init(&bh->b_uptodate_lock); +#if IS_ENABLED(CONFIG_JBD2) + spin_lock_init(&bh->b_state_lock); + spin_lock_init(&bh->b_journal_head_lock); +#endif } #else /* PREEMPT_RT || DEBUG_BIT_SPINLOCKS */ --- a/include/linux/jbd2.h +++ b/include/linux/jbd2.h @@ -342,6 +342,40 @@ static inline struct journal_head *bh2jh return bh->b_private; } +#if defined(CONFIG_PREEMPT_RT) || defined(CONFIG_DEBUG_BIT_SPINLOCKS) + +static inline void jbd_lock_bh_state(struct buffer_head *bh) +{ + spin_lock(&bh->b_state_lock); +} + +static inline int jbd_trylock_bh_state(struct buffer_head *bh) +{ + return spin_trylock(&bh->b_state_lock); +} + +static inline int jbd_is_locked_bh_state(struct buffer_head *bh) +{ + return spin_is_locked(&bh->b_state_lock); +} + +static inline void jbd_unlock_bh_state(struct buffer_head *bh) +{ + spin_unlock(&bh->b_state_lock); +} + +static inline void jbd_lock_bh_journal_head(struct buffer_head *bh) +{ + spin_lock(&bh->b_journal_head_lock); +} + +static inline void jbd_unlock_bh_journal_head(struct buffer_head *bh) +{ + spin_unlock(&bh->b_journal_head_lock); +} + +#else /* PREEMPT_RT || DEBUG_BIT_SPINLOCKS */ + static inline void jbd_lock_bh_state(struct buffer_head *bh) { bit_spin_lock(BH_State, &bh->b_state); @@ -372,6 +406,8 @@ static inline void jbd_unlock_bh_journal bit_spin_unlock(BH_JournalHead, &bh->b_state); } +#endif /* !PREEMPT_RT && !DEBUG_BIT_SPINLOCKS */ + #define J_ASSERT(assert) BUG_ON(!(assert)) #define J_ASSERT_BH(bh, expr) J_ASSERT(expr)