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Commit 7c3f654d authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

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: default avatarOleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarPeter 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: default avatarIngo Molnar <mingo@kernel.org>
parent aba37660

fs/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -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

fs/locks.c

+29 −18
Original line number Diff line number Diff line
@@ -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;

}