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Message-ID: <f40f07f4-27b8-5308-80f6-9d2904c8dd52@huawei.com>
Date: Tue, 28 Apr 2020 21:54:38 +0800
From: Wu Bo <wubo40@...wei.com>
To: "Yan, Zheng" <ukernel@...il.com>
CC: Jeff Layton <jlayton@...nel.org>, Sage Weil <sage@...hat.com>,
"Ilya Dryomov" <idryomov@...il.com>,
ceph-devel <ceph-devel@...r.kernel.org>,
"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
<liuzhiqiang26@...wei.com>, <linfeilong@...wei.com>
Subject: Re: [PATCH] fs/ceph:fix double unlock in handle_cap_export()
On 2020/4/28 21:41, Yan, Zheng wrote:
> On Tue, Apr 28, 2020 at 8:50 PM Wu Bo <wubo40@...wei.com> wrote:
>>
>> If the ceph_mdsc_open_export_target_session() return fails,
>> should add a lock to avoid twice unlocking.
>> Because the lock will be released at the retry or out_unlock tag.
>>
>
> at retry label, i_ceph_lock get locked. I don't see how i_ceph_lock
> can get double unlock
>sorry, maybe I didn't describe it clearly enough, not i_ceph_lock, but
session->s_mutex.
Thanks.
Wu Bo
>> Signed-off-by: Wu Bo <wubo40@...wei.com>
>> ---
>> fs/ceph/caps.c | 26 ++++++++++++++------------
>> 1 file changed, 14 insertions(+), 12 deletions(-)
>>
>> diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
>> index 185db76..b5a62a8 100644
>> --- a/fs/ceph/caps.c
>> +++ b/fs/ceph/caps.c
>> @@ -3731,22 +3731,24 @@ static void handle_cap_export(struct inode *inode, struct ceph_mds_caps *ex,
>>
>> /* open target session */
>> tsession = ceph_mdsc_open_export_target_session(mdsc, target);
>> - if (!IS_ERR(tsession)) {
>> - if (mds > target) {
>> - mutex_lock(&session->s_mutex);
>> - mutex_lock_nested(&tsession->s_mutex,
>> - SINGLE_DEPTH_NESTING);
>> - } else {
>> - mutex_lock(&tsession->s_mutex);
>> - mutex_lock_nested(&session->s_mutex,
>> - SINGLE_DEPTH_NESTING);
>> - }
>> - new_cap = ceph_get_cap(mdsc, NULL);
>> - } else {
>> + if (IS_ERR(tsession)) {
>> WARN_ON(1);
>> tsession = NULL;
>> target = -1;
>> + mutex_lock(&session->s_mutex);
>> + goto out_unlock;
>> + }
>> +
>> + if (mds > target) {
>> + mutex_lock(&session->s_mutex);
>> + mutex_lock_nested(&tsession->s_mutex,
>> + SINGLE_DEPTH_NESTING);
>> + } else {
>> + mutex_lock(&tsession->s_mutex);
>> + mutex_lock_nested(&session->s_mutex,
>> + SINGLE_DEPTH_NESTING);
>> }
>> + new_cap = ceph_get_cap(mdsc, NULL);
>> goto retry;
>>
>> out_unlock:
>> --
>> 1.8.3.1
>>
>
> .
>
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