From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: linux-nfs-owner@vger.kernel.org Received: from mx1.redhat.com ([209.132.183.28]:58048 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752292Ab3FQPOg (ORCPT ); Mon, 17 Jun 2013 11:14:36 -0400 From: Jeff Layton To: viro@zeniv.linux.org.uk, matthew@wil.cx, bfields@fieldses.org Cc: dhowells@redhat.com, sage@inktank.com, smfrench@gmail.com, swhiteho@redhat.com, Trond.Myklebust@netapp.com, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-afs@lists.infradead.org, ceph-devel@vger.kernel.org, linux-cifs@vger.kernel.org, samba-technical@lists.samba.org, cluster-devel@redhat.com, linux-nfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, piastryyy@gmail.com Subject: [PATCH v3 07/13] locks: avoid taking global lock if possible when waking up blocked waiters Date: Mon, 17 Jun 2013 11:13:50 -0400 Message-Id: <1371482036-15958-8-git-send-email-jlayton@redhat.com> In-Reply-To: <1371482036-15958-1-git-send-email-jlayton@redhat.com> References: <1371482036-15958-1-git-send-email-jlayton@redhat.com> Sender: linux-nfs-owner@vger.kernel.org List-ID: Since we always hold the i_lock when inserting a new waiter onto the fl_block list, we can avoid taking the global lock at all if we find that it's empty when we go to wake up blocked waiters. Signed-off-by: Jeff Layton --- fs/locks.c | 17 ++++++++++++++--- 1 files changed, 14 insertions(+), 3 deletions(-) diff --git a/fs/locks.c b/fs/locks.c index 8f56651..a8f3b33 100644 --- a/fs/locks.c +++ b/fs/locks.c @@ -532,7 +532,10 @@ static void locks_delete_block(struct file_lock *waiter) * the order they blocked. The documentation doesn't require this but * it seems like the reasonable thing to do. * - * Must be called with file_lock_lock held! + * Must be called with both the i_lock and file_lock_lock held. The fl_block + * list itself is protected by the file_lock_list, but by ensuring that the + * i_lock is also held on insertions we can avoid taking the file_lock_lock + * in some cases when we see that the fl_block list is empty. */ static void __locks_insert_block(struct file_lock *blocker, struct file_lock *waiter) @@ -560,8 +563,16 @@ static void locks_insert_block(struct file_lock *blocker, */ static void locks_wake_up_blocks(struct file_lock *blocker) { + /* + * Avoid taking global lock if list is empty. This is safe since new + * blocked requests are only added to the list under the i_lock, and + * the i_lock is always held here. + */ + if (list_empty(&blocker->fl_block)) + return; + spin_lock(&file_lock_lock); - while (!list_empty(&blocker->fl_block)) { + do { struct file_lock *waiter; waiter = list_first_entry(&blocker->fl_block, @@ -571,7 +582,7 @@ static void locks_wake_up_blocks(struct file_lock *blocker) waiter->fl_lmops->lm_notify(waiter); else wake_up(&waiter->fl_wait); - } + } while (!list_empty(&blocker->fl_block)); spin_unlock(&file_lock_lock); } -- 1.7.1