From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751281Ab3IFSY1 (ORCPT ); Fri, 6 Sep 2013 14:24:27 -0400 Received: from mga02.intel.com ([134.134.136.20]:32430 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750838Ab3IFSY0 (ORCPT ); Fri, 6 Sep 2013 14:24:26 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.90,855,1371106800"; d="scan'208";a="399510778" Subject: [PATCH 1/2] fs/superblock: Unregister sb shrinker before ->kill_sb() From: Tim Chen To: Dave Chinner , Jan Kara , Alexander Viro Cc: Dave Hansen , Andi Kleen , Matthew Wilcox , linux-fsdevel , linux-kernel , "Kirill A. Shutemov" Content-Type: text/plain; charset="UTF-8" Date: Fri, 06 Sep 2013 11:24:22 -0700 Message-ID: <1378491862.3467.6.camel@schen9-DESK> Mime-Version: 1.0 X-Mailer: Evolution 2.32.3 (2.32.3-1.fc14) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Dave, I've created the two patches we've discussed on the mail thread regarding avoiding grab_super_passive during memory reclaim. Tim From: Dave Chinner We will like to unregister the sb shrinker before ->kill_sb(). This will allow cached objects to be counted without call to grab_super_passive() to update ref count on sb. We want to avoid locking during memory reclamation especially when we are skipping the memory reclaim when we are out of cached objects. This is safe because grab_super_passive does a try-lock on the sb->s_umount now, and so if we are in the unmount process, it won't ever block. That means what used to be a deadlock and races we were avoiding by using grab_super_passive() is now: shrinker umount down_read(shrinker_rwsem) down_write(sb->s_umount) shrinker_unregister down_write(shrinker_rwsem) grab_super_passive(sb) down_read_trylock(sb->s_umount) .... up_read(shrinker_rwsem) up_write(shrinker_rwsem) ->kill_sb() .... So it is safe to deregister the shrinker before ->kill_sb(). Signed-off-by: Tim Chen --- fs/super.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/super.c b/fs/super.c index 73d0952..b724f35 100644 --- a/fs/super.c +++ b/fs/super.c @@ -324,10 +324,10 @@ void deactivate_locked_super(struct super_block *s) struct file_system_type *fs = s->s_type; if (atomic_dec_and_test(&s->s_active)) { cleancache_invalidate_fs(s); + unregister_shrinker(&s->s_shrink); fs->kill_sb(s); /* caches are now gone, we can safely kill the shrinker now */ - unregister_shrinker(&s->s_shrink); list_lru_destroy(&s->s_dentry_lru); list_lru_destroy(&s->s_inode_lru); -- 1.7.11.7