linux-kernel - [ANNOUNCE] v5.15-rt17

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Date:   Tue, 2 Nov 2021 12:05:40 +0100
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        linux-rt-users@...r.kernel.org,
        Steven Rostedt <rostedt@...dmis.org>
Subject: [ANNOUNCE] v5.15-rt17

Dear RT folks!

I'm pleased to announce the v5.15-rt17 patch set. 

Changes since v5.15-rt16:

  - Remove put_cpu_var() in fscache which removal was overseen in the
    last release.

  - Redo the fs/dcache/start_dir_add() related patch and its
    description.

  - Drop preempt_disable_rt(), no more users.

Known issues
     - netconsole triggers WARN.

     - The "Memory controller" (CONFIG_MEMCG) has been disabled.

     - Valentin Schneider reported a few splats on ARM64, see
          https://lkml.kernel.org/r/20210810134127.1394269-1-valentin.schneider@arm.com

The delta patch against v5.15-rt16 is appended below and can be found here:
 
     https://cdn.kernel.org/pub/linux/kernel/projects/rt/5.15/incr/patch-5.15-rt16-rt17.patch.xz

You can get this release via the git tree at:

    git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git v5.15-rt17

The RT patch against v5.15 can be found here:

    https://cdn.kernel.org/pub/linux/kernel/projects/rt/5.15/older/patch-5.15-rt17.patch.xz

The split quilt queue is available at:

    https://cdn.kernel.org/pub/linux/kernel/projects/rt/5.15/older/patches-5.15-rt17.tar.xz

Sebastian

diff --git a/fs/dcache.c b/fs/dcache.c
index f34344ceece70..02db80f2817fc 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -2537,11 +2537,16 @@ EXPORT_SYMBOL(d_rehash);
 
 static inline unsigned start_dir_add(struct inode *dir)
 {
-
-	preempt_disable_rt();
+	/*
+	 * The caller has a spinlock_t (dentry::d_lock) acquired which disables
+	 * preemption on !PREEMPT_RT. On PREEMPT_RT the lock does not disable
+	 * preemption and it has be done explicitly.
+	 */
+	if (IS_ENABLED(CONFIG_PREEMPT_RT))
+		preempt_disable();
 	for (;;) {
-		unsigned n = dir->__i_dir_seq;
-		if (!(n & 1) && cmpxchg(&dir->__i_dir_seq, n, n + 1) == n)
+		unsigned n = dir->i_dir_seq;
+		if (!(n & 1) && cmpxchg(&dir->i_dir_seq, n, n + 1) == n)
 			return n;
 		cpu_relax();
 	}
@@ -2549,8 +2554,9 @@ static inline unsigned start_dir_add(struct inode *dir)
 
 static inline void end_dir_add(struct inode *dir, unsigned n)
 {
-	smp_store_release(&dir->__i_dir_seq, n + 2);
-	preempt_enable_rt();
+	smp_store_release(&dir->i_dir_seq, n + 2);
+	if (IS_ENABLED(CONFIG_PREEMPT_RT))
+		preempt_enable();
 }
 
 static void d_wait_lookup(struct dentry *dentry)
@@ -2586,7 +2592,7 @@ struct dentry *d_alloc_parallel(struct dentry *parent,
 
 retry:
 	rcu_read_lock();
-	seq = smp_load_acquire(&parent->d_inode->__i_dir_seq);
+	seq = smp_load_acquire(&parent->d_inode->i_dir_seq);
 	r_seq = read_seqbegin(&rename_lock);
 	dentry = __d_lookup_rcu(parent, name, &d_seq);
 	if (unlikely(dentry)) {
@@ -2614,7 +2620,7 @@ struct dentry *d_alloc_parallel(struct dentry *parent,
 	}
 
 	hlist_bl_lock(b);
-	if (unlikely(READ_ONCE(parent->d_inode->__i_dir_seq) != seq)) {
+	if (unlikely(READ_ONCE(parent->d_inode->i_dir_seq) != seq)) {
 		hlist_bl_unlock(b);
 		rcu_read_unlock();
 		goto retry;
diff --git a/fs/fscache/object.c b/fs/fscache/object.c
index 78f332f2e98c8..7a972d144b546 100644
--- a/fs/fscache/object.c
+++ b/fs/fscache/object.c
@@ -814,8 +814,6 @@ void fscache_enqueue_object(struct fscache_object *object)
 				wake_up(&fscache_object_cong_wait);
 		} else
 			fscache_put_object(object, fscache_obj_put_queue);
-
-		put_cpu_var(fscache_object_cong_wait);
 	}
 }
 
diff --git a/fs/inode.c b/fs/inode.c
index 0c46c1a98c2ac..ed0cab8a32db1 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -157,7 +157,7 @@ int inode_init_always(struct super_block *sb, struct inode *inode)
 	inode->i_pipe = NULL;
 	inode->i_cdev = NULL;
 	inode->i_link = NULL;
-	inode->__i_dir_seq = 0;
+	inode->i_dir_seq = 0;
 	inode->i_rdev = 0;
 	inode->dirtied_when = 0;
 
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 5ff6117d59f54..e7a633353fd20 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -711,7 +711,7 @@ struct inode {
 		struct pipe_inode_info	*i_pipe;
 		struct cdev		*i_cdev;
 		char			*i_link;
-		unsigned		__i_dir_seq;
+		unsigned		i_dir_seq;
 	};
 
 	__u32			i_generation;
diff --git a/include/linux/preempt.h b/include/linux/preempt.h
index dc8158a459859..3da73c9682119 100644
--- a/include/linux/preempt.h
+++ b/include/linux/preempt.h
@@ -331,14 +331,6 @@ do { \
 		set_preempt_need_resched(); \
 } while (0)
 
-#ifdef CONFIG_PREEMPT_RT
-# define preempt_disable_rt()		preempt_disable()
-# define preempt_enable_rt()		preempt_enable()
-#else
-# define preempt_disable_rt()		barrier()
-# define preempt_enable_rt()		barrier()
-#endif
-
 #ifdef CONFIG_PREEMPT_NOTIFIERS
 
 struct preempt_notifier;
diff --git a/localversion-rt b/localversion-rt
index 1199ebade17b4..1e584b47c987e 100644
--- a/localversion-rt
+++ b/localversion-rt
@@ -1 +1 @@
--rt16
+-rt17