Return-Path: Received: from mail-yk0-f180.google.com ([209.85.160.180]:34714 "EHLO mail-yk0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753310AbbINNqD (ORCPT ); Mon, 14 Sep 2015 09:46:03 -0400 Received: by ykdg206 with SMTP id g206so152582371ykd.1 for ; Mon, 14 Sep 2015 06:46:02 -0700 (PDT) From: Jeff Layton To: Al Viro Cc: bfields@fieldses.org, linux-nfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH 1/4] fs: have flush_delayed_fput flush the workqueue job Date: Mon, 14 Sep 2015 09:45:52 -0400 Message-Id: <1442238355-8203-2-git-send-email-jeff.layton@primarydata.com> In-Reply-To: <1442238355-8203-1-git-send-email-jeff.layton@primarydata.com> References: <1442238355-8203-1-git-send-email-jeff.layton@primarydata.com> Sender: linux-nfs-owner@vger.kernel.org List-ID: I think there's a potential race in flush_delayed_fput. A kthread does an fput() and that file gets added to the list and the delayed work is scheduled. More than 1 jiffy passes, and the workqueue thread picks up the work and starts running it. Then the kthread calls flush_delayed_work. It sees that the list is empty and returns immediately, even though the __fput for its file may not have run yet. Close this by making flush_delayed_fput use flush_delayed_work instead, which should immediately schedule the work to run if it's not already, and block until the workqueue job completes. Signed-off-by: Jeff Layton --- fs/file_table.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/fs/file_table.c b/fs/file_table.c index 7f9d407c7595..f4833af62eae 100644 --- a/fs/file_table.c +++ b/fs/file_table.c @@ -243,6 +243,8 @@ static void ____fput(struct callback_head *work) __fput(container_of(work, struct file, f_u.fu_rcuhead)); } +static DECLARE_DELAYED_WORK(delayed_fput_work, delayed_fput); + /* * If kernel thread really needs to have the final fput() it has done * to complete, call this. The only user right now is the boot - we @@ -255,11 +257,9 @@ static void ____fput(struct callback_head *work) */ void flush_delayed_fput(void) { - delayed_fput(NULL); + flush_delayed_work(&delayed_fput_work); } -static DECLARE_DELAYED_WORK(delayed_fput_work, delayed_fput); - void fput(struct file *file) { if (atomic_long_dec_and_test(&file->f_count)) { -- 2.4.3