linux-kernel - [PATCH v2 2/8] dentry: Use preempt_[dis|en]able

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Date:   Thu, 25 Aug 2022 18:41:25 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     linux-kernel@...r.kernel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Matthew Wilcox <willy@...radead.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        linux-fsdevel@...r.kernel.org,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Subject: [PATCH v2 2/8] dentry: Use preempt_[dis|en]able_nested()

From: Thomas Gleixner <tglx@...utronix.de>

Replace the open coded CONFIG_PREEMPT_RT conditional
preempt_disable/enable() with the new helper.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Cc: Alexander Viro <viro@...iv.linux.org.uk>
Cc: linux-fsdevel@...r.kernel.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 fs/dcache.c | 13 ++-----------
 1 file changed, 2 insertions(+), 11 deletions(-)

diff --git a/fs/dcache.c b/fs/dcache.c
index bb0c4d0038dbd..2ee8636016ee9 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -2597,15 +2597,7 @@ EXPORT_SYMBOL(d_rehash);
 
 static inline unsigned start_dir_add(struct inode *dir)
 {
-	/*
-	 * The caller holds a spinlock (dentry::d_lock). On !PREEMPT_RT
-	 * kernels spin_lock() implicitly disables preemption, but not on
-	 * PREEMPT_RT.  So for RT it has to be done explicitly to protect
-	 * the sequence count write side critical section against a reader
-	 * or another writer preempting, which would result in a live lock.
-	 */
-	if (IS_ENABLED(CONFIG_PREEMPT_RT))
-		preempt_disable();
+	preempt_disable_nested();
 	for (;;) {
 		unsigned n = dir->i_dir_seq;
 		if (!(n & 1) && cmpxchg(&dir->i_dir_seq, n, n + 1) == n)
@@ -2618,8 +2610,7 @@ static inline void end_dir_add(struct inode *dir, unsigned int n,
 			       wait_queue_head_t *d_wait)
 {
 	smp_store_release(&dir->i_dir_seq, n + 2);
-	if (IS_ENABLED(CONFIG_PREEMPT_RT))
-		preempt_enable();
+	preempt_enable_nested();
 	wake_up_all(d_wait);
 }
 
-- 
2.37.2