[RFC v1 4/5] locks: Use percpu spinlocks to protect file_lock_list

From: Daniel Wagner
Date: Fri Feb 20 2015 - 09:40:09 EST


Replace the lglock with percpu spinlocks. That allows us to iterate in
the seqfile ops without taking all underlyng spinlocks with the
lg_global_lock().

Signed-off-by: Daniel Wagner <daniel.wagner@xxxxxxxxxxxx>
Cc: Jeff Layton <jlayton@xxxxxxxxxxxxxxx>
Cc: "J. Bruce Fields" <bfields@xxxxxxxxxxxx>
Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
---
fs/locks.c | 30 ++++++++++++++++--------------
1 file changed, 16 insertions(+), 14 deletions(-)

diff --git a/fs/locks.c b/fs/locks.c
index 142e4fd..20ed00a 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -128,7 +128,6 @@
#include <linux/pid_namespace.h>
#include <linux/hashtable.h>
#include <linux/percpu.h>
-#include <linux/lglock.h>

#define CREATE_TRACE_POINTS
#include <trace/events/filelock.h>
@@ -160,10 +159,10 @@ int lease_break_time = 45;
/*
* The global file_lock_list is only used for displaying /proc/locks, so we
* keep a list on each CPU, with each list protected by its own spinlock via
- * the file_lock_lglock. Note that alterations to the list also require that
+ * the file_lock_lock. Note that alterations to the list also require that
* the relevant flc_lock is held.
*/
-DEFINE_STATIC_LGLOCK(file_lock_lglock);
+static DEFINE_PER_CPU(spinlock_t, file_lock_lock);
static DEFINE_PER_CPU(struct hlist_head, file_lock_list);

/*
@@ -561,10 +560,10 @@ static int posix_same_owner(struct file_lock *fl1, struct file_lock *fl2)
/* Must be called with the flc_lock held! */
static void locks_insert_global_locks(struct file_lock *fl)
{
- lg_local_lock(&file_lock_lglock);
+ spin_lock(this_cpu_ptr(&file_lock_lock));
fl->fl_link_cpu = smp_processor_id();
hlist_add_head(&fl->fl_link, this_cpu_ptr(&file_lock_list));
- lg_local_unlock(&file_lock_lglock);
+ spin_unlock(this_cpu_ptr(&file_lock_lock));
}

/* Must be called with the flc_lock held! */
@@ -577,9 +576,9 @@ static void locks_delete_global_locks(struct file_lock *fl)
*/
if (hlist_unhashed(&fl->fl_link))
return;
- lg_local_lock_cpu(&file_lock_lglock, fl->fl_link_cpu);
+ spin_lock(per_cpu_ptr(&file_lock_lock, fl->fl_link_cpu));
hlist_del_init(&fl->fl_link);
- lg_local_unlock_cpu(&file_lock_lglock, fl->fl_link_cpu);
+ spin_unlock(per_cpu_ptr(&file_lock_lock, fl->fl_link_cpu));
}

static unsigned long
@@ -2628,9 +2627,9 @@ static void *locks_start(struct seq_file *f, loff_t *pos)
struct locks_iterator *iter = f->private;

iter->li_pos = *pos + 1;
- lg_global_lock(&file_lock_lglock);
spin_lock(&blocked_lock_lock);
- return seq_hlist_start_percpu(&file_lock_list, &iter->li_cpu, *pos);
+ return seq_hlist_start_percpu_locked(&file_lock_list, &file_lock_lock,
+ &iter->li_cpu, *pos);
}

static void *locks_next(struct seq_file *f, void *v, loff_t *pos)
@@ -2638,14 +2637,17 @@ static void *locks_next(struct seq_file *f, void *v, loff_t *pos)
struct locks_iterator *iter = f->private;

++iter->li_pos;
- return seq_hlist_next_percpu(v, &file_lock_list, &iter->li_cpu, pos);
+ return seq_hlist_next_percpu_locked(v, &file_lock_list, &file_lock_lock,
+ &iter->li_cpu, pos);
}

static void locks_stop(struct seq_file *f, void *v)
__releases(&blocked_lock_lock)
{
+ struct locks_iterator *iter = f->private;
+
+ seq_hlist_stop_percpu_locked(v, &file_lock_lock, &iter->li_cpu);
spin_unlock(&blocked_lock_lock);
- lg_global_unlock(&file_lock_lglock);
}

static const struct seq_operations locks_seq_operations = {
@@ -2686,10 +2688,10 @@ static int __init filelock_init(void)
filelock_cache = kmem_cache_create("file_lock_cache",
sizeof(struct file_lock), 0, SLAB_PANIC, NULL);

- lg_lock_init(&file_lock_lglock, "file_lock_lglock");
-
- for_each_possible_cpu(i)
+ for_each_possible_cpu(i) {
INIT_HLIST_HEAD(per_cpu_ptr(&file_lock_list, i));
+ spin_lock_init(per_cpu_ptr(&file_lock_lock, i));
+ }

return 0;
}
--
2.1.0

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