* [Ocfs2-devel] [PATCH v2] ocfs2/dlm: fix race between purge and get lock resource
@ 2015-04-25 10:44 Joseph Qi
2015-04-30 6:16 ` Junxiao Bi
0 siblings, 1 reply; 4+ messages in thread
From: Joseph Qi @ 2015-04-25 10:44 UTC (permalink / raw)
To: ocfs2-devel
There is a race between purge and get lock resource, which will lead to
ast unfinished and system hung. The case is described below:
mkdir dlm_thread
-----------------------------------------------------------------------
o2cb_dlm_lock |
-> dlmlock |
-> dlm_get_lock_resource |
-> __dlm_lookup_lockres_full |
-> spin_unlock(&dlm->spinlock) |
| dlm_run_purge_list
| -> dlm_purge_lockres
| -> dlm_drop_lockres_ref
| -> spin_lock(&dlm->spinlock)
| -> spin_lock(&res->spinlock)
| -> ~DLM_LOCK_RES_DROPPING_REF
| -> spin_unlock(&res->spinlock)
| -> spin_unlock(&dlm->spinlock)
-> spin_lock(&tmpres->spinlock)|
DLM_LOCK_RES_DROPPING_REF cleared |
-> spin_unlock(&tmpres->spinlock) |
return the purged lockres |
So after this, once ast comes, it will ignore the ast because the
lockres cannot be found anymore. Thus the OCFS2_LOCK_BUSY won't be
cleared and corresponding thread hangs.
The &dlm->spinlock was hold when checking DLM_LOCK_RES_DROPPING_REF at
the very beginning. And commit 7b791d68562e ("ocfs2/dlm: Fix race during
lockres mastery") moved it up because of the possible wait.
So take the &dlm->spinlock and introduce a new wait function to fix the
race.
Signed-off-by: Joseph Qi <joseph.qi@huawei.com>
Reviewed-by: joyce.xue <xuejiufei@huawei.com>
Cc: <stable@vger.kernel.org>
---
fs/ocfs2/dlm/dlmcommon.h | 2 ++
fs/ocfs2/dlm/dlmmaster.c | 13 +++++++++----
fs/ocfs2/dlm/dlmthread.c | 23 +++++++++++++++++++++++
3 files changed, 34 insertions(+), 4 deletions(-)
diff --git a/fs/ocfs2/dlm/dlmcommon.h b/fs/ocfs2/dlm/dlmcommon.h
index e88ccf8..c6b76f4 100644
--- a/fs/ocfs2/dlm/dlmcommon.h
+++ b/fs/ocfs2/dlm/dlmcommon.h
@@ -1014,6 +1014,8 @@ void dlm_move_lockres_to_recovery_list(struct dlm_ctxt *dlm,
/* will exit holding res->spinlock, but may drop in function */
void __dlm_wait_on_lockres_flags(struct dlm_lock_resource *res, int flags);
+void __dlm_wait_on_lockres_flags_new(struct dlm_ctxt *dlm,
+ struct dlm_lock_resource *res, int flags);
/* will exit holding res->spinlock, but may drop in function */
static inline void __dlm_wait_on_lockres(struct dlm_lock_resource *res)
diff --git a/fs/ocfs2/dlm/dlmmaster.c b/fs/ocfs2/dlm/dlmmaster.c
index a6944b2..9a5f45d 100644
--- a/fs/ocfs2/dlm/dlmmaster.c
+++ b/fs/ocfs2/dlm/dlmmaster.c
@@ -755,13 +755,16 @@ lookup:
spin_lock(&dlm->spinlock);
tmpres = __dlm_lookup_lockres_full(dlm, lockid, namelen, hash);
if (tmpres) {
- spin_unlock(&dlm->spinlock);
spin_lock(&tmpres->spinlock);
/* Wait on the thread that is mastering the resource */
if (tmpres->owner == DLM_LOCK_RES_OWNER_UNKNOWN) {
- __dlm_wait_on_lockres(tmpres);
+ __dlm_wait_on_lockres_flags_new(dlm, tmpres,
+ (DLM_LOCK_RES_IN_PROGRESS|
+ DLM_LOCK_RES_RECOVERING|
+ DLM_LOCK_RES_MIGRATING));
BUG_ON(tmpres->owner == DLM_LOCK_RES_OWNER_UNKNOWN);
spin_unlock(&tmpres->spinlock);
+ spin_unlock(&dlm->spinlock);
dlm_lockres_put(tmpres);
tmpres = NULL;
goto lookup;
@@ -770,9 +773,10 @@ lookup:
/* Wait on the resource purge to complete before continuing */
if (tmpres->state & DLM_LOCK_RES_DROPPING_REF) {
BUG_ON(tmpres->owner == dlm->node_num);
- __dlm_wait_on_lockres_flags(tmpres,
- DLM_LOCK_RES_DROPPING_REF);
+ __dlm_wait_on_lockres_flags_new(dlm, tmpres,
+ DLM_LOCK_RES_DROPPING_REF);
spin_unlock(&tmpres->spinlock);
+ spin_unlock(&dlm->spinlock);
dlm_lockres_put(tmpres);
tmpres = NULL;
goto lookup;
@@ -782,6 +786,7 @@ lookup:
dlm_lockres_grab_inflight_ref(dlm, tmpres);
spin_unlock(&tmpres->spinlock);
+ spin_unlock(&dlm->spinlock);
if (res)
dlm_lockres_put(res);
res = tmpres;
diff --git a/fs/ocfs2/dlm/dlmthread.c b/fs/ocfs2/dlm/dlmthread.c
index 69aac6f..505730a 100644
--- a/fs/ocfs2/dlm/dlmthread.c
+++ b/fs/ocfs2/dlm/dlmthread.c
@@ -77,6 +77,29 @@ repeat:
__set_current_state(TASK_RUNNING);
}
+void __dlm_wait_on_lockres_flags_new(struct dlm_ctxt *dlm,
+ struct dlm_lock_resource *res, int flags)
+{
+ DECLARE_WAITQUEUE(wait, current);
+
+ assert_spin_locked(&dlm->spinlock);
+ assert_spin_locked(&res->spinlock);
+
+ add_wait_queue(&res->wq, &wait);
+repeat:
+ set_current_state(TASK_UNINTERRUPTIBLE);
+ if (res->state & flags) {
+ spin_unlock(&res->spinlock);
+ spin_unlock(&dlm->spinlock);
+ schedule();
+ spin_lock(&dlm->spinlock);
+ spin_lock(&res->spinlock);
+ goto repeat;
+ }
+ remove_wait_queue(&res->wq, &wait);
+ __set_current_state(TASK_RUNNING);
+}
+
int __dlm_lockres_has_locks(struct dlm_lock_resource *res)
{
if (list_empty(&res->granted) &&
--
1.8.4.3
^ permalink raw reply related [flat|nested] 4+ messages in thread
* [Ocfs2-devel] [PATCH v2] ocfs2/dlm: fix race between purge and get lock resource
2015-04-25 10:44 [Ocfs2-devel] [PATCH v2] ocfs2/dlm: fix race between purge and get lock resource Joseph Qi
@ 2015-04-30 6:16 ` Junxiao Bi
2015-04-30 7:04 ` Joseph Qi
0 siblings, 1 reply; 4+ messages in thread
From: Junxiao Bi @ 2015-04-30 6:16 UTC (permalink / raw)
To: ocfs2-devel
On 04/25/2015 06:44 PM, Joseph Qi wrote:
> There is a race between purge and get lock resource, which will lead to
> ast unfinished and system hung. The case is described below:
>
> mkdir dlm_thread
> -----------------------------------------------------------------------
> o2cb_dlm_lock |
> -> dlmlock |
> -> dlm_get_lock_resource |
> -> __dlm_lookup_lockres_full |
> -> spin_unlock(&dlm->spinlock) |
> | dlm_run_purge_list
> | -> dlm_purge_lockres
> | -> dlm_drop_lockres_ref
> | -> spin_lock(&dlm->spinlock)
> | -> spin_lock(&res->spinlock)
> | -> ~DLM_LOCK_RES_DROPPING_REF
> | -> spin_unlock(&res->spinlock)
> | -> spin_unlock(&dlm->spinlock)
> -> spin_lock(&tmpres->spinlock)|
> DLM_LOCK_RES_DROPPING_REF cleared |
> -> spin_unlock(&tmpres->spinlock) |
> return the purged lockres |
>
> So after this, once ast comes, it will ignore the ast because the
> lockres cannot be found anymore. Thus the OCFS2_LOCK_BUSY won't be
> cleared and corresponding thread hangs.
> The &dlm->spinlock was hold when checking DLM_LOCK_RES_DROPPING_REF at
> the very beginning. And commit 7b791d68562e ("ocfs2/dlm: Fix race during
> lockres mastery") moved it up because of the possible wait.
> So take the &dlm->spinlock and introduce a new wait function to fix the
> race.
The fix to this issue seemed a little complicated.
Indeed this is a similar issue with commit
cb79662bc2f83f7b3b60970ad88df43085f96514 ("ocfs2: o2dlm: fix a race
between purge and master query"), we can reference that fix. How about
the following fix?
diff --git a/fs/ocfs2/dlm/dlmmaster.c b/fs/ocfs2/dlm/dlmmaster.c
index a6944b2..25314d2 100644
--- a/fs/ocfs2/dlm/dlmmaster.c
+++ b/fs/ocfs2/dlm/dlmmaster.c
@@ -757,6 +757,18 @@ lookup:
if (tmpres) {
spin_unlock(&dlm->spinlock);
spin_lock(&tmpres->spinlock);
+
+ /*
+ * Right after dlm spinlock was released, dlm_thread
could have
+ * purged the lockres. Check if lockres got unhashed. If so
+ * start over.
+ */
+ if (hlist_unhashed(&tmpres->hash_node)) {
+ spin_unlock(&tmpres->spinlock);
+ dlm_lockres_put(tmpres);
+ goto lookup;
+ }
+
/* Wait on the thread that is mastering the resource */
if (tmpres->owner == DLM_LOCK_RES_OWNER_UNKNOWN) {
__dlm_wait_on_lockres(tmpres);
Thanks,
Junxiao.
>
> Signed-off-by: Joseph Qi <joseph.qi@huawei.com>
> Reviewed-by: joyce.xue <xuejiufei@huawei.com>
> Cc: <stable@vger.kernel.org>
> ---
> fs/ocfs2/dlm/dlmcommon.h | 2 ++
> fs/ocfs2/dlm/dlmmaster.c | 13 +++++++++----
> fs/ocfs2/dlm/dlmthread.c | 23 +++++++++++++++++++++++
> 3 files changed, 34 insertions(+), 4 deletions(-)
>
> diff --git a/fs/ocfs2/dlm/dlmcommon.h b/fs/ocfs2/dlm/dlmcommon.h
> index e88ccf8..c6b76f4 100644
> --- a/fs/ocfs2/dlm/dlmcommon.h
> +++ b/fs/ocfs2/dlm/dlmcommon.h
> @@ -1014,6 +1014,8 @@ void dlm_move_lockres_to_recovery_list(struct dlm_ctxt *dlm,
>
> /* will exit holding res->spinlock, but may drop in function */
> void __dlm_wait_on_lockres_flags(struct dlm_lock_resource *res, int flags);
> +void __dlm_wait_on_lockres_flags_new(struct dlm_ctxt *dlm,
> + struct dlm_lock_resource *res, int flags);
>
> /* will exit holding res->spinlock, but may drop in function */
> static inline void __dlm_wait_on_lockres(struct dlm_lock_resource *res)
> diff --git a/fs/ocfs2/dlm/dlmmaster.c b/fs/ocfs2/dlm/dlmmaster.c
> index a6944b2..9a5f45d 100644
> --- a/fs/ocfs2/dlm/dlmmaster.c
> +++ b/fs/ocfs2/dlm/dlmmaster.c
> @@ -755,13 +755,16 @@ lookup:
> spin_lock(&dlm->spinlock);
> tmpres = __dlm_lookup_lockres_full(dlm, lockid, namelen, hash);
> if (tmpres) {
> - spin_unlock(&dlm->spinlock);
> spin_lock(&tmpres->spinlock);
> /* Wait on the thread that is mastering the resource */
> if (tmpres->owner == DLM_LOCK_RES_OWNER_UNKNOWN) {
> - __dlm_wait_on_lockres(tmpres);
> + __dlm_wait_on_lockres_flags_new(dlm, tmpres,
> + (DLM_LOCK_RES_IN_PROGRESS|
> + DLM_LOCK_RES_RECOVERING|
> + DLM_LOCK_RES_MIGRATING));
> BUG_ON(tmpres->owner == DLM_LOCK_RES_OWNER_UNKNOWN);
> spin_unlock(&tmpres->spinlock);
> + spin_unlock(&dlm->spinlock);
> dlm_lockres_put(tmpres);
> tmpres = NULL;
> goto lookup;
> @@ -770,9 +773,10 @@ lookup:
> /* Wait on the resource purge to complete before continuing */
> if (tmpres->state & DLM_LOCK_RES_DROPPING_REF) {
> BUG_ON(tmpres->owner == dlm->node_num);
> - __dlm_wait_on_lockres_flags(tmpres,
> - DLM_LOCK_RES_DROPPING_REF);
> + __dlm_wait_on_lockres_flags_new(dlm, tmpres,
> + DLM_LOCK_RES_DROPPING_REF);
> spin_unlock(&tmpres->spinlock);
> + spin_unlock(&dlm->spinlock);
> dlm_lockres_put(tmpres);
> tmpres = NULL;
> goto lookup;
> @@ -782,6 +786,7 @@ lookup:
> dlm_lockres_grab_inflight_ref(dlm, tmpres);
>
> spin_unlock(&tmpres->spinlock);
> + spin_unlock(&dlm->spinlock);
> if (res)
> dlm_lockres_put(res);
> res = tmpres;
> diff --git a/fs/ocfs2/dlm/dlmthread.c b/fs/ocfs2/dlm/dlmthread.c
> index 69aac6f..505730a 100644
> --- a/fs/ocfs2/dlm/dlmthread.c
> +++ b/fs/ocfs2/dlm/dlmthread.c
> @@ -77,6 +77,29 @@ repeat:
> __set_current_state(TASK_RUNNING);
> }
>
> +void __dlm_wait_on_lockres_flags_new(struct dlm_ctxt *dlm,
> + struct dlm_lock_resource *res, int flags)
> +{
> + DECLARE_WAITQUEUE(wait, current);
> +
> + assert_spin_locked(&dlm->spinlock);
> + assert_spin_locked(&res->spinlock);
> +
> + add_wait_queue(&res->wq, &wait);
> +repeat:
> + set_current_state(TASK_UNINTERRUPTIBLE);
> + if (res->state & flags) {
> + spin_unlock(&res->spinlock);
> + spin_unlock(&dlm->spinlock);
> + schedule();
> + spin_lock(&dlm->spinlock);
> + spin_lock(&res->spinlock);
> + goto repeat;
> + }
> + remove_wait_queue(&res->wq, &wait);
> + __set_current_state(TASK_RUNNING);
> +}
> +
> int __dlm_lockres_has_locks(struct dlm_lock_resource *res)
> {
> if (list_empty(&res->granted) &&
^ permalink raw reply related [flat|nested] 4+ messages in thread
* [Ocfs2-devel] [PATCH v2] ocfs2/dlm: fix race between purge and get lock resource
2015-04-30 6:16 ` Junxiao Bi
@ 2015-04-30 7:04 ` Joseph Qi
2015-04-30 14:30 ` Junxiao Bi
0 siblings, 1 reply; 4+ messages in thread
From: Joseph Qi @ 2015-04-30 7:04 UTC (permalink / raw)
To: ocfs2-devel
Hi Junxiao,
On 2015/4/30 14:16, Junxiao Bi wrote:
> On 04/25/2015 06:44 PM, Joseph Qi wrote:
>> There is a race between purge and get lock resource, which will lead to
>> ast unfinished and system hung. The case is described below:
>>
>> mkdir dlm_thread
>> -----------------------------------------------------------------------
>> o2cb_dlm_lock |
>> -> dlmlock |
>> -> dlm_get_lock_resource |
>> -> __dlm_lookup_lockres_full |
>> -> spin_unlock(&dlm->spinlock) |
>> | dlm_run_purge_list
>> | -> dlm_purge_lockres
>> | -> dlm_drop_lockres_ref
>> | -> spin_lock(&dlm->spinlock)
>> | -> spin_lock(&res->spinlock)
>> | -> ~DLM_LOCK_RES_DROPPING_REF
>> | -> spin_unlock(&res->spinlock)
>> | -> spin_unlock(&dlm->spinlock)
>> -> spin_lock(&tmpres->spinlock)|
>> DLM_LOCK_RES_DROPPING_REF cleared |
>> -> spin_unlock(&tmpres->spinlock) |
>> return the purged lockres |
>>
>> So after this, once ast comes, it will ignore the ast because the
>> lockres cannot be found anymore. Thus the OCFS2_LOCK_BUSY won't be
>> cleared and corresponding thread hangs.
>> The &dlm->spinlock was hold when checking DLM_LOCK_RES_DROPPING_REF at
>> the very beginning. And commit 7b791d68562e ("ocfs2/dlm: Fix race during
>> lockres mastery") moved it up because of the possible wait.
>> So take the &dlm->spinlock and introduce a new wait function to fix the
>> race.
> The fix to this issue seemed a little complicated.
>
> Indeed this is a similar issue with commit cb79662bc2f83f7b3b60970ad88df43085f96514 ("ocfs2: o2dlm: fix a race between purge and master query"), we can reference that fix. How about the following fix?
>
> diff --git a/fs/ocfs2/dlm/dlmmaster.c b/fs/ocfs2/dlm/dlmmaster.c
> index a6944b2..25314d2 100644
> --- a/fs/ocfs2/dlm/dlmmaster.c
> +++ b/fs/ocfs2/dlm/dlmmaster.c
> @@ -757,6 +757,18 @@ lookup:
> if (tmpres) {
> spin_unlock(&dlm->spinlock);
> spin_lock(&tmpres->spinlock);
> +
> + /*
> + * Right after dlm spinlock was released, dlm_thread could have
> + * purged the lockres. Check if lockres got unhashed. If so
> + * start over.
> + */
> + if (hlist_unhashed(&tmpres->hash_node)) {
> + spin_unlock(&tmpres->spinlock);
> + dlm_lockres_put(tmpres);
> + goto lookup;
> + }
> +
> /* Wait on the thread that is mastering the resource */
> if (tmpres->owner == DLM_LOCK_RES_OWNER_UNKNOWN) {
> __dlm_wait_on_lockres(tmpres);
>
> Thanks,
> Junxiao.
Thanks very much for the above fix.
It looks good to me and much simpler than my fix.
A small suggestion is setting tmpres to NULL after dlm_lockres_put to keep
consistency.
Could you please send a new version?
>>
>> Signed-off-by: Joseph Qi <joseph.qi@huawei.com>
>> Reviewed-by: joyce.xue <xuejiufei@huawei.com>
>> Cc: <stable@vger.kernel.org>
>> ---
>> fs/ocfs2/dlm/dlmcommon.h | 2 ++
>> fs/ocfs2/dlm/dlmmaster.c | 13 +++++++++----
>> fs/ocfs2/dlm/dlmthread.c | 23 +++++++++++++++++++++++
>> 3 files changed, 34 insertions(+), 4 deletions(-)
>>
>> diff --git a/fs/ocfs2/dlm/dlmcommon.h b/fs/ocfs2/dlm/dlmcommon.h
>> index e88ccf8..c6b76f4 100644
>> --- a/fs/ocfs2/dlm/dlmcommon.h
>> +++ b/fs/ocfs2/dlm/dlmcommon.h
>> @@ -1014,6 +1014,8 @@ void dlm_move_lockres_to_recovery_list(struct dlm_ctxt *dlm,
>>
>> /* will exit holding res->spinlock, but may drop in function */
>> void __dlm_wait_on_lockres_flags(struct dlm_lock_resource *res, int flags);
>> +void __dlm_wait_on_lockres_flags_new(struct dlm_ctxt *dlm,
>> + struct dlm_lock_resource *res, int flags);
>>
>> /* will exit holding res->spinlock, but may drop in function */
>> static inline void __dlm_wait_on_lockres(struct dlm_lock_resource *res)
>> diff --git a/fs/ocfs2/dlm/dlmmaster.c b/fs/ocfs2/dlm/dlmmaster.c
>> index a6944b2..9a5f45d 100644
>> --- a/fs/ocfs2/dlm/dlmmaster.c
>> +++ b/fs/ocfs2/dlm/dlmmaster.c
>> @@ -755,13 +755,16 @@ lookup:
>> spin_lock(&dlm->spinlock);
>> tmpres = __dlm_lookup_lockres_full(dlm, lockid, namelen, hash);
>> if (tmpres) {
>> - spin_unlock(&dlm->spinlock);
>> spin_lock(&tmpres->spinlock);
>> /* Wait on the thread that is mastering the resource */
>> if (tmpres->owner == DLM_LOCK_RES_OWNER_UNKNOWN) {
>> - __dlm_wait_on_lockres(tmpres);
>> + __dlm_wait_on_lockres_flags_new(dlm, tmpres,
>> + (DLM_LOCK_RES_IN_PROGRESS|
>> + DLM_LOCK_RES_RECOVERING|
>> + DLM_LOCK_RES_MIGRATING));
>> BUG_ON(tmpres->owner == DLM_LOCK_RES_OWNER_UNKNOWN);
>> spin_unlock(&tmpres->spinlock);
>> + spin_unlock(&dlm->spinlock);
>> dlm_lockres_put(tmpres);
>> tmpres = NULL;
>> goto lookup;
>> @@ -770,9 +773,10 @@ lookup:
>> /* Wait on the resource purge to complete before continuing */
>> if (tmpres->state & DLM_LOCK_RES_DROPPING_REF) {
>> BUG_ON(tmpres->owner == dlm->node_num);
>> - __dlm_wait_on_lockres_flags(tmpres,
>> - DLM_LOCK_RES_DROPPING_REF);
>> + __dlm_wait_on_lockres_flags_new(dlm, tmpres,
>> + DLM_LOCK_RES_DROPPING_REF);
>> spin_unlock(&tmpres->spinlock);
>> + spin_unlock(&dlm->spinlock);
>> dlm_lockres_put(tmpres);
>> tmpres = NULL;
>> goto lookup;
>> @@ -782,6 +786,7 @@ lookup:
>> dlm_lockres_grab_inflight_ref(dlm, tmpres);
>>
>> spin_unlock(&tmpres->spinlock);
>> + spin_unlock(&dlm->spinlock);
>> if (res)
>> dlm_lockres_put(res);
>> res = tmpres;
>> diff --git a/fs/ocfs2/dlm/dlmthread.c b/fs/ocfs2/dlm/dlmthread.c
>> index 69aac6f..505730a 100644
>> --- a/fs/ocfs2/dlm/dlmthread.c
>> +++ b/fs/ocfs2/dlm/dlmthread.c
>> @@ -77,6 +77,29 @@ repeat:
>> __set_current_state(TASK_RUNNING);
>> }
>>
>> +void __dlm_wait_on_lockres_flags_new(struct dlm_ctxt *dlm,
>> + struct dlm_lock_resource *res, int flags)
>> +{
>> + DECLARE_WAITQUEUE(wait, current);
>> +
>> + assert_spin_locked(&dlm->spinlock);
>> + assert_spin_locked(&res->spinlock);
>> +
>> + add_wait_queue(&res->wq, &wait);
>> +repeat:
>> + set_current_state(TASK_UNINTERRUPTIBLE);
>> + if (res->state & flags) {
>> + spin_unlock(&res->spinlock);
>> + spin_unlock(&dlm->spinlock);
>> + schedule();
>> + spin_lock(&dlm->spinlock);
>> + spin_lock(&res->spinlock);
>> + goto repeat;
>> + }
>> + remove_wait_queue(&res->wq, &wait);
>> + __set_current_state(TASK_RUNNING);
>> +}
>> +
>> int __dlm_lockres_has_locks(struct dlm_lock_resource *res)
>> {
>> if (list_empty(&res->granted) &&
>
>
> .
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Ocfs2-devel] [PATCH v2] ocfs2/dlm: fix race between purge and get lock resource
2015-04-30 7:04 ` Joseph Qi
@ 2015-04-30 14:30 ` Junxiao Bi
0 siblings, 0 replies; 4+ messages in thread
From: Junxiao Bi @ 2015-04-30 14:30 UTC (permalink / raw)
To: ocfs2-devel
On 04/30/2015 03:04 PM, Joseph Qi wrote:
> Hi Junxiao,
>
> On 2015/4/30 14:16, Junxiao Bi wrote:
>> On 04/25/2015 06:44 PM, Joseph Qi wrote:
>>> There is a race between purge and get lock resource, which will lead to
>>> ast unfinished and system hung. The case is described below:
>>>
>>> mkdir dlm_thread
>>> -----------------------------------------------------------------------
>>> o2cb_dlm_lock |
>>> -> dlmlock |
>>> -> dlm_get_lock_resource |
>>> -> __dlm_lookup_lockres_full |
>>> -> spin_unlock(&dlm->spinlock) |
>>> | dlm_run_purge_list
>>> | -> dlm_purge_lockres
>>> | -> dlm_drop_lockres_ref
>>> | -> spin_lock(&dlm->spinlock)
>>> | -> spin_lock(&res->spinlock)
>>> | -> ~DLM_LOCK_RES_DROPPING_REF
>>> | -> spin_unlock(&res->spinlock)
>>> | -> spin_unlock(&dlm->spinlock)
>>> -> spin_lock(&tmpres->spinlock)|
>>> DLM_LOCK_RES_DROPPING_REF cleared |
>>> -> spin_unlock(&tmpres->spinlock) |
>>> return the purged lockres |
>>>
>>> So after this, once ast comes, it will ignore the ast because the
>>> lockres cannot be found anymore. Thus the OCFS2_LOCK_BUSY won't be
>>> cleared and corresponding thread hangs.
>>> The &dlm->spinlock was hold when checking DLM_LOCK_RES_DROPPING_REF at
>>> the very beginning. And commit 7b791d68562e ("ocfs2/dlm: Fix race during
>>> lockres mastery") moved it up because of the possible wait.
>>> So take the &dlm->spinlock and introduce a new wait function to fix the
>>> race.
>> The fix to this issue seemed a little complicated.
>>
>> Indeed this is a similar issue with commit cb79662bc2f83f7b3b60970ad88df43085f96514 ("ocfs2: o2dlm: fix a race between purge and master query"), we can reference that fix. How about the following fix?
>>
>> diff --git a/fs/ocfs2/dlm/dlmmaster.c b/fs/ocfs2/dlm/dlmmaster.c
>> index a6944b2..25314d2 100644
>> --- a/fs/ocfs2/dlm/dlmmaster.c
>> +++ b/fs/ocfs2/dlm/dlmmaster.c
>> @@ -757,6 +757,18 @@ lookup:
>> if (tmpres) {
>> spin_unlock(&dlm->spinlock);
>> spin_lock(&tmpres->spinlock);
>> +
>> + /*
>> + * Right after dlm spinlock was released, dlm_thread could have
>> + * purged the lockres. Check if lockres got unhashed. If so
>> + * start over.
>> + */
>> + if (hlist_unhashed(&tmpres->hash_node)) {
>> + spin_unlock(&tmpres->spinlock);
>> + dlm_lockres_put(tmpres);
>> + goto lookup;
>> + }
>> +
>> /* Wait on the thread that is mastering the resource */
>> if (tmpres->owner == DLM_LOCK_RES_OWNER_UNKNOWN) {
>> __dlm_wait_on_lockres(tmpres);
>>
>> Thanks,
>> Junxiao.
> Thanks very much for the above fix.
> It looks good to me and much simpler than my fix.
> A small suggestion is setting tmpres to NULL after dlm_lockres_put to keep
> consistency.
> Could you please send a new version?
Sure, patch sent, thanks for your advice.
Thanks,
Junxiao.
>
>>> Signed-off-by: Joseph Qi <joseph.qi@huawei.com>
>>> Reviewed-by: joyce.xue <xuejiufei@huawei.com>
>>> Cc: <stable@vger.kernel.org>
>>> ---
>>> fs/ocfs2/dlm/dlmcommon.h | 2 ++
>>> fs/ocfs2/dlm/dlmmaster.c | 13 +++++++++----
>>> fs/ocfs2/dlm/dlmthread.c | 23 +++++++++++++++++++++++
>>> 3 files changed, 34 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/fs/ocfs2/dlm/dlmcommon.h b/fs/ocfs2/dlm/dlmcommon.h
>>> index e88ccf8..c6b76f4 100644
>>> --- a/fs/ocfs2/dlm/dlmcommon.h
>>> +++ b/fs/ocfs2/dlm/dlmcommon.h
>>> @@ -1014,6 +1014,8 @@ void dlm_move_lockres_to_recovery_list(struct dlm_ctxt *dlm,
>>>
>>> /* will exit holding res->spinlock, but may drop in function */
>>> void __dlm_wait_on_lockres_flags(struct dlm_lock_resource *res, int flags);
>>> +void __dlm_wait_on_lockres_flags_new(struct dlm_ctxt *dlm,
>>> + struct dlm_lock_resource *res, int flags);
>>>
>>> /* will exit holding res->spinlock, but may drop in function */
>>> static inline void __dlm_wait_on_lockres(struct dlm_lock_resource *res)
>>> diff --git a/fs/ocfs2/dlm/dlmmaster.c b/fs/ocfs2/dlm/dlmmaster.c
>>> index a6944b2..9a5f45d 100644
>>> --- a/fs/ocfs2/dlm/dlmmaster.c
>>> +++ b/fs/ocfs2/dlm/dlmmaster.c
>>> @@ -755,13 +755,16 @@ lookup:
>>> spin_lock(&dlm->spinlock);
>>> tmpres = __dlm_lookup_lockres_full(dlm, lockid, namelen, hash);
>>> if (tmpres) {
>>> - spin_unlock(&dlm->spinlock);
>>> spin_lock(&tmpres->spinlock);
>>> /* Wait on the thread that is mastering the resource */
>>> if (tmpres->owner == DLM_LOCK_RES_OWNER_UNKNOWN) {
>>> - __dlm_wait_on_lockres(tmpres);
>>> + __dlm_wait_on_lockres_flags_new(dlm, tmpres,
>>> + (DLM_LOCK_RES_IN_PROGRESS|
>>> + DLM_LOCK_RES_RECOVERING|
>>> + DLM_LOCK_RES_MIGRATING));
>>> BUG_ON(tmpres->owner == DLM_LOCK_RES_OWNER_UNKNOWN);
>>> spin_unlock(&tmpres->spinlock);
>>> + spin_unlock(&dlm->spinlock);
>>> dlm_lockres_put(tmpres);
>>> tmpres = NULL;
>>> goto lookup;
>>> @@ -770,9 +773,10 @@ lookup:
>>> /* Wait on the resource purge to complete before continuing */
>>> if (tmpres->state & DLM_LOCK_RES_DROPPING_REF) {
>>> BUG_ON(tmpres->owner == dlm->node_num);
>>> - __dlm_wait_on_lockres_flags(tmpres,
>>> - DLM_LOCK_RES_DROPPING_REF);
>>> + __dlm_wait_on_lockres_flags_new(dlm, tmpres,
>>> + DLM_LOCK_RES_DROPPING_REF);
>>> spin_unlock(&tmpres->spinlock);
>>> + spin_unlock(&dlm->spinlock);
>>> dlm_lockres_put(tmpres);
>>> tmpres = NULL;
>>> goto lookup;
>>> @@ -782,6 +786,7 @@ lookup:
>>> dlm_lockres_grab_inflight_ref(dlm, tmpres);
>>>
>>> spin_unlock(&tmpres->spinlock);
>>> + spin_unlock(&dlm->spinlock);
>>> if (res)
>>> dlm_lockres_put(res);
>>> res = tmpres;
>>> diff --git a/fs/ocfs2/dlm/dlmthread.c b/fs/ocfs2/dlm/dlmthread.c
>>> index 69aac6f..505730a 100644
>>> --- a/fs/ocfs2/dlm/dlmthread.c
>>> +++ b/fs/ocfs2/dlm/dlmthread.c
>>> @@ -77,6 +77,29 @@ repeat:
>>> __set_current_state(TASK_RUNNING);
>>> }
>>>
>>> +void __dlm_wait_on_lockres_flags_new(struct dlm_ctxt *dlm,
>>> + struct dlm_lock_resource *res, int flags)
>>> +{
>>> + DECLARE_WAITQUEUE(wait, current);
>>> +
>>> + assert_spin_locked(&dlm->spinlock);
>>> + assert_spin_locked(&res->spinlock);
>>> +
>>> + add_wait_queue(&res->wq, &wait);
>>> +repeat:
>>> + set_current_state(TASK_UNINTERRUPTIBLE);
>>> + if (res->state & flags) {
>>> + spin_unlock(&res->spinlock);
>>> + spin_unlock(&dlm->spinlock);
>>> + schedule();
>>> + spin_lock(&dlm->spinlock);
>>> + spin_lock(&res->spinlock);
>>> + goto repeat;
>>> + }
>>> + remove_wait_queue(&res->wq, &wait);
>>> + __set_current_state(TASK_RUNNING);
>>> +}
>>> +
>>> int __dlm_lockres_has_locks(struct dlm_lock_resource *res)
>>> {
>>> if (list_empty(&res->granted) &&
>>
>> .
>>
>
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2015-04-30 14:30 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2015-04-25 10:44 [Ocfs2-devel] [PATCH v2] ocfs2/dlm: fix race between purge and get lock resource Joseph Qi
2015-04-30 6:16 ` Junxiao Bi
2015-04-30 7:04 ` Joseph Qi
2015-04-30 14:30 ` Junxiao Bi
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