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fs/locks: Replace lg_local with a per-cpu spinlock 

As Oleg suggested, replace file_lock_list with a structure containing
the hlist head and a spinlock.

This completely removes the lglock from fs/locks.

Suggested-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dave@stgolabs.net
Cc: der.herr@hofr.at
Cc: paulmck@linux.vnet.ibm.com
Cc: riel@redhat.com
Cc: tj@kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2015-06-22 14:16:34 +02:00 committed by Ingo Molnar
parent aba3766073
commit 7c3f654d8e
2 changed files with 30 additions and 18 deletions
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1
fs/Kconfig
View File

@ -79,6 +79,7 @@ config EXPORTFS_BLOCK_OPS
config FILE_LOCKING
bool "Enable POSIX file locking API" if EXPERT
default y
select PERCPU_RWSEM
help
This option enables standard file locking support, required
for filesystems like NFS and for the flock() system

47
fs/locks.c
View File

@ -127,7 +127,6 @@
#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>
@ -158,12 +157,17 @@ 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 relevant flc_lock is held.
* keep a list on each CPU, with each list protected by its own spinlock.
* Global serialization is done using file_rwsem.
*
* 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(struct hlist_head, file_lock_list);
struct file_lock_list_struct {
spinlock_t lock;
struct hlist_head hlist;
};
static DEFINE_PER_CPU(struct file_lock_list_struct, file_lock_list);
DEFINE_STATIC_PERCPU_RWSEM(file_rwsem);
/*
@ -588,17 +592,21 @@ 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)
{
struct file_lock_list_struct *fll = this_cpu_ptr(&file_lock_list);
percpu_rwsem_assert_held(&file_rwsem);
lg_local_lock(&file_lock_lglock);
spin_lock(&fll->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);
hlist_add_head(&fl->fl_link, &fll->hlist);
spin_unlock(&fll->lock);
}
/* Must be called with the flc_lock held! */
static void locks_delete_global_locks(struct file_lock *fl)
{
struct file_lock_list_struct *fll;
percpu_rwsem_assert_held(&file_rwsem);
/*
@ -608,9 +616,11 @@ 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);
fll = per_cpu_ptr(&file_lock_list, fl->fl_link_cpu);
spin_lock(&fll->lock);
hlist_del_init(&fl->fl_link);
lg_local_unlock_cpu(&file_lock_lglock, fl->fl_link_cpu);
spin_unlock(&fll->lock);
}
static unsigned long
@ -2723,9 +2733,8 @@ static void *locks_start(struct seq_file *f, loff_t *pos)
iter->li_pos = *pos + 1;
percpu_down_write(&file_rwsem);
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(&file_lock_list.hlist, &iter->li_cpu, *pos);
}
static void *locks_next(struct seq_file *f, void *v, loff_t *pos)
@ -2733,14 +2742,13 @@ 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(v, &file_lock_list.hlist, &iter->li_cpu, pos);
}
static void locks_stop(struct seq_file *f, void *v)
__releases(&blocked_lock_lock)
{
spin_unlock(&blocked_lock_lock);
lg_global_unlock(&file_lock_lglock);
percpu_up_write(&file_rwsem);
}
@ -2782,10 +2790,13 @@ 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)
INIT_HLIST_HEAD(per_cpu_ptr(&file_lock_list, i));
for_each_possible_cpu(i) {
struct file_lock_list_struct *fll = per_cpu_ptr(&file_lock_list, i);
spin_lock_init(&fll->lock);
INIT_HLIST_HEAD(&fll->hlist);
}
return 0;
}