[Ocfs2-devel] [PATCH] ocfs2: Fix locking for res->tracking and dlm->tracking_list
Changwei Ge
gechangwei at live.cn
Thu Jun 21 18:33:04 PDT 2018
On 2018/6/22 8:34, piaojun wrote:
> Hi Ashish,
>
> I think we should get 'res->spinlock' before getting 'dlm->track_lock'
> such as in __dlm_do_purge_lockres(). But your patch reverse the locking
> sequence as we will get 'res->spinlock' in dlm_print_one_lock_resource()
> which may cause 'ABBA' deadlock.
Agree. This patch could introduce dead lock issue.
> thanks,
> Jun
>
> On 2018/6/22 7:57, Ashish Samant wrote:
>> In dlm_init_lockres() and dlm_unregister_domain() we access and modify
>> res->tracking and dlm->tracking_list without holding dlm->track_lock.
>> This can cause list corruptions and can end up in kernel panic.
>>
>> Fix this by locking res->tracking and dlm->tracking_list with
>> dlm->track_lock at all places.
>>
>> Signed-off-by: Ashish Samant <ashish.samant at oracle.com>
>> ---
>> fs/ocfs2/dlm/dlmdomain.c | 2 ++
>> fs/ocfs2/dlm/dlmmaster.c | 4 ++--
>> 2 files changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/fs/ocfs2/dlm/dlmdomain.c b/fs/ocfs2/dlm/dlmdomain.c
>> index 2acd58b..cfb1edd 100644
>> --- a/fs/ocfs2/dlm/dlmdomain.c
>> +++ b/fs/ocfs2/dlm/dlmdomain.c
>> @@ -723,6 +723,7 @@ void dlm_unregister_domain(struct dlm_ctxt *dlm)
>> mlog(0, "%s: more migration to do\n", dlm->name);
>> }
>>
>> + spin_lock(&dlm->track_lock);
>> /* This list should be empty. If not, print remaining lockres */
>> if (!list_empty(&dlm->tracking_list)) {
>> mlog(ML_ERROR, "Following lockres' are still on the "
>> @@ -730,6 +731,7 @@ void dlm_unregister_domain(struct dlm_ctxt *dlm)
>> list_for_each_entry(res, &dlm->tracking_list, tracking)
>> dlm_print_one_lock_resource(res);
>> }
>> + spin_unlock(&dlm->track_lock);
As Jun's comment, above fix is not proper. But the issue Ashish points
to truly exists.
>>
>> dlm_mark_domain_leaving(dlm);
>> dlm_leave_domain(dlm);
>> diff --git a/fs/ocfs2/dlm/dlmmaster.c b/fs/ocfs2/dlm/dlmmaster.c
>> index aaca094..826f056 100644
>> --- a/fs/ocfs2/dlm/dlmmaster.c
>> +++ b/fs/ocfs2/dlm/dlmmaster.c
>> @@ -584,9 +584,9 @@ static void dlm_init_lockres(struct dlm_ctxt *dlm,
>>
>> res->last_used = 0;
>>
>> - spin_lock(&dlm->spinlock);
>> + spin_lock(&dlm->track_lock);
>> list_add_tail(&res->tracking, &dlm->tracking_list);
>> - spin_unlock(&dlm->spinlock);
>> + spin_unlock(&dlm->track_lock);
Yet, this fix makes sense.
Thanks,
Changwei
>>
>> memset(res->lvb, 0, DLM_LVB_LEN);
>> memset(res->refmap, 0, sizeof(res->refmap));
>>
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