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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Sun, 12 Jun 2022 16:27:31 +0200
Subject: [PATCH 3/4] fs/dcache: Use __d_lookup_unhash() in __d_add/move()
__d_add() and __d_move() invoke __d_lookup_done() from within a preemption
disabled region. This violates the PREEMPT_RT constraints as the wake up
acquires wait_queue_head::lock which is a "sleeping" spinlock on RT.
As a preparation for solving this completely, invoke __d_lookup_unhash()
from __d_add/move() and handle the wakeup there.
This allows to move the spin_lock/unlock(dentry::lock) pair into
__d_lookup_done() which debloats the d_lookup_done() inline.
No functional change. Moving the wake up out of the preemption disabled
region on RT will be handled in a subsequent change.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://lkml.kernel.org/r/20220613140712.77932-4-bigeasy@linutronix.de
---
fs/dcache.c | 6 ++++--
include/linux/dcache.h | 7 ++-----
2 files changed, 6 insertions(+), 7 deletions(-)
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -2737,7 +2737,9 @@ static wait_queue_head_t *__d_lookup_unh
void __d_lookup_done(struct dentry *dentry)
{
+ spin_lock(&dentry->d_lock);
wake_up_all(__d_lookup_unhash(dentry));
+ spin_unlock(&dentry->d_lock);
}
EXPORT_SYMBOL(__d_lookup_done);
@@ -2751,7 +2753,7 @@ static inline void __d_add(struct dentry
if (unlikely(d_in_lookup(dentry))) {
dir = dentry->d_parent->d_inode;
n = start_dir_add(dir);
- __d_lookup_done(dentry);
+ wake_up_all(__d_lookup_unhash(dentry));
}
if (inode) {
unsigned add_flags = d_flags_for_inode(inode);
@@ -2940,7 +2942,7 @@ static void __d_move(struct dentry *dent
if (unlikely(d_in_lookup(target))) {
dir = target->d_parent->d_inode;
n = start_dir_add(dir);
- __d_lookup_done(target);
+ wake_up_all(__d_lookup_unhash(target));
}
write_seqcount_begin(&dentry->d_seq);
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -349,7 +349,7 @@ static inline void dont_mount(struct den
spin_unlock(&dentry->d_lock);
}
-extern void __d_lookup_done(struct dentry *);
+extern void __d_lookup_done(struct dentry *dentry);
static inline int d_in_lookup(const struct dentry *dentry)
{
@@ -358,11 +358,8 @@ static inline int d_in_lookup(const stru
static inline void d_lookup_done(struct dentry *dentry)
{
- if (unlikely(d_in_lookup(dentry))) {
- spin_lock(&dentry->d_lock);
+ if (unlikely(d_in_lookup(dentry)))
__d_lookup_done(dentry);
- spin_unlock(&dentry->d_lock);
- }
}
extern void dput(struct dentry *);
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