From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from m12-12.163.com ([220.181.12.12]:33072 "EHLO m12-12.163.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751427AbdFEIyF (ORCPT ); Mon, 5 Jun 2017 04:54:05 -0400 Message-ID: <59351CB4.1010100@163.com> Date: Mon, 05 Jun 2017 16:56:20 +0800 From: Jia-Ju Bai MIME-Version: 1.0 Subject: Re: [PATCH] fs: xfs: Fix a lock-twice and sleep-in-atomic bug in xfs_iget References: <1496650649-2296-1-git-send-email-baijiaju1990@163.com> <43a9b80f-fd7d-2df3-f726-207742c7924f@oracle.com> In-Reply-To: <43a9b80f-fd7d-2df3-f726-207742c7924f@oracle.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-xfs-owner@vger.kernel.org List-ID: List-Id: xfs To: Shan Hai Cc: darrick.wong@oracle.com, linux-xfs@vger.kernel.org, linux-kernel@vger.kernel.org On 06/05/2017 04:32 PM, Shan Hai wrote: > > > On 2017年06月05日 16:17, Jia-Ju Bai wrote: >> The driver may sleep under a read rcu lock, and function call path is: >> xfs_iget (acquire the lock by rcu_read_lock) >> "goto out_error_or_again" after xfs_iget_cache_hit >> delay >> schedule_timeout_uninterruptible --> may sleep >> Meanwhile, the rcu_read_lock will be called twice in this situation. >> >> To fix it, the lock is released before "goto". >> >> Signed-off-by: Jia-Ju Bai >> --- >> fs/xfs/xfs_icache.c | 4 +++- >> 1 file changed, 3 insertions(+), 1 deletion(-) >> >> diff --git a/fs/xfs/xfs_icache.c b/fs/xfs/xfs_icache.c >> index f61c84f8..c2a4722 100644 >> --- a/fs/xfs/xfs_icache.c >> +++ b/fs/xfs/xfs_icache.c >> @@ -600,8 +600,10 @@ struct xfs_inode * >> if (ip) { >> error = xfs_iget_cache_hit(pag, ip, ino, flags, lock_flags); >> - if (error) >> + if (error) { >> + rcu_read_unlock(); > > Seems you are going to double unlock by doing this, since it is > unlocked in the xfs_iget_cache_hit. > > Thanks > Shan Hai > >> goto out_error_or_again; >> + } >> } else { >> rcu_read_unlock(); >> XFS_STATS_INC(mp, xs_ig_missed); > I think you are right. Please ignore my patch. Thanks, Jia-Ju Bai