forked from rrcarlosr/Jetpack
133 lines
4.2 KiB
Diff
133 lines
4.2 KiB
Diff
From 68c3b66eaa763a5cd8417107b415373341c8eb58 Mon Sep 17 00:00:00 2001
|
|
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
|
|
Date: Fri, 20 Oct 2017 11:29:53 +0200
|
|
Subject: [PATCH 328/352] fs/dcache: disable preemption on i_dir_seq's write
|
|
side
|
|
|
|
i_dir_seq is an opencoded seqcounter. Based on the code it looks like we
|
|
could have two writers in parallel despite the fact that the d_lock is
|
|
held. The problem is that during the write process on RT the preemption
|
|
is still enabled and if this process is interrupted by a reader with RT
|
|
priority then we lock up.
|
|
To avoid that lock up I am disabling the preemption during the update.
|
|
The rename of i_dir_seq is here to ensure to catch new write sides in
|
|
future.
|
|
|
|
Cc: stable-rt@vger.kernel.org
|
|
Reported-by: Oleg.Karfich@wago.com
|
|
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
|
|
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
|
|
---
|
|
fs/dcache.c | 12 +++++++-----
|
|
fs/inode.c | 2 +-
|
|
fs/libfs.c | 6 ++++--
|
|
include/linux/fs.h | 2 +-
|
|
4 files changed, 13 insertions(+), 9 deletions(-)
|
|
|
|
diff --git a/fs/dcache.c b/fs/dcache.c
|
|
index 18581a9..1b81ea5 100644
|
|
--- a/fs/dcache.c
|
|
+++ b/fs/dcache.c
|
|
@@ -2443,9 +2443,10 @@ EXPORT_SYMBOL(d_rehash);
|
|
static inline unsigned start_dir_add(struct inode *dir)
|
|
{
|
|
|
|
+ preempt_disable_rt();
|
|
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();
|
|
}
|
|
@@ -2453,7 +2454,8 @@ 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);
|
|
+ smp_store_release(&dir->__i_dir_seq, n + 2);
|
|
+ preempt_enable_rt();
|
|
}
|
|
|
|
static void d_wait_lookup(struct dentry *dentry)
|
|
@@ -2489,7 +2491,7 @@ 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)) {
|
|
@@ -2517,7 +2519,7 @@ 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/inode.c b/fs/inode.c
|
|
index 1d1a957..99b9bae 100644
|
|
--- a/fs/inode.c
|
|
+++ b/fs/inode.c
|
|
@@ -153,7 +153,7 @@ int inode_init_always(struct super_block *sb, struct inode *inode)
|
|
inode->i_bdev = 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/fs/libfs.c b/fs/libfs.c
|
|
index 9588780a..9b37abd 100644
|
|
--- a/fs/libfs.c
|
|
+++ b/fs/libfs.c
|
|
@@ -89,7 +89,7 @@ static struct dentry *next_positive(struct dentry *parent,
|
|
struct list_head *from,
|
|
int count)
|
|
{
|
|
- unsigned *seq = &parent->d_inode->i_dir_seq, n;
|
|
+ unsigned *seq = &parent->d_inode->__i_dir_seq, n;
|
|
struct dentry *res;
|
|
struct list_head *p;
|
|
bool skipped;
|
|
@@ -122,8 +122,9 @@ static struct dentry *next_positive(struct dentry *parent,
|
|
static void move_cursor(struct dentry *cursor, struct list_head *after)
|
|
{
|
|
struct dentry *parent = cursor->d_parent;
|
|
- unsigned n, *seq = &parent->d_inode->i_dir_seq;
|
|
+ unsigned n, *seq = &parent->d_inode->__i_dir_seq;
|
|
spin_lock(&parent->d_lock);
|
|
+ preempt_disable_rt();
|
|
for (;;) {
|
|
n = *seq;
|
|
if (!(n & 1) && cmpxchg(seq, n, n + 1) == n)
|
|
@@ -136,6 +137,7 @@ static void move_cursor(struct dentry *cursor, struct list_head *after)
|
|
else
|
|
list_add_tail(&cursor->d_child, &parent->d_subdirs);
|
|
smp_store_release(seq, n + 2);
|
|
+ preempt_enable_rt();
|
|
spin_unlock(&parent->d_lock);
|
|
}
|
|
|
|
diff --git a/include/linux/fs.h b/include/linux/fs.h
|
|
index e22a270..7d8f1b8 100644
|
|
--- a/include/linux/fs.h
|
|
+++ b/include/linux/fs.h
|
|
@@ -708,7 +708,7 @@ struct inode {
|
|
struct block_device *i_bdev;
|
|
struct cdev *i_cdev;
|
|
char *i_link;
|
|
- unsigned i_dir_seq;
|
|
+ unsigned __i_dir_seq;
|
|
};
|
|
|
|
__u32 i_generation;
|
|
--
|
|
2.7.4
|
|
|