The patch titled
Subject: ocfs2/dlm: fix race between purge and get lock resource
has been added to the -mm tree. Its filename is
ocfs2-dlm-fix-race-between-purge-and-get-lock-resource.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/ocfs2-dlm-fix-race-between-purge-and-get-lock-resource.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/ocfs2-dlm-fix-race-between-purge-and-get-lock-resource.patch
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------------------------------------------------------
From: Joseph Qi <joseph.qi@xxxxxxxxxx>
Subject: ocfs2/dlm: fix race between purge and get lock resource
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 ingore 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 held when checking DLM_LOCK_RES_DROPPING_REF at the
very begining. And commit 7b791d6856 ("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@xxxxxxxxxx>
Reviewed-by: joyce.xue <xuejiufei@xxxxxxxxxx>
Cc: Mark Fasheh <mfasheh@xxxxxxxx>
Cc: Joel Becker <jlbec@xxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
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 -puN fs/ocfs2/dlm/dlmcommon.h~ocfs2-dlm-fix-race-between-purge-and-get-lock-resource fs/ocfs2/dlm/dlmcommon.h
--- a/fs/ocfs2/dlm/dlmcommon.h~ocfs2-dlm-fix-race-between-purge-and-get-lock-resource
+++ a/fs/ocfs2/dlm/dlmcommon.h
@@ -1014,6 +1014,8 @@ void dlm_move_lockres_to_recovery_list(s
/* 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 -puN fs/ocfs2/dlm/dlmmaster.c~ocfs2-dlm-fix-race-between-purge-and-get-lock-resource fs/ocfs2/dlm/dlmmaster.c
--- a/fs/ocfs2/dlm/dlmmaster.c~ocfs2-dlm-fix-race-between-purge-and-get-lock-resource
+++ a/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 -puN fs/ocfs2/dlm/dlmthread.c~ocfs2-dlm-fix-race-between-purge-and-get-lock-resource fs/ocfs2/dlm/dlmthread.c
--- a/fs/ocfs2/dlm/dlmthread.c~ocfs2-dlm-fix-race-between-purge-and-get-lock-resource
+++ a/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) &&
_
Patches currently in -mm which might be from joseph.qi@xxxxxxxxxx are
ocfs2-fix-a-tiny-race-when-truncate-dio-orohaned-entry.patch
ocfs2-use-retval-instead-of-status-for-checking-error.patch
ocfs2-dlm-cleanup-unused-function-__dlm_wait_on_lockres_flags_set.patch
ocfs2-dlm-fix-race-between-purge-and-get-lock-resource.patch
ocfs2-set-filesytem-read-only-when-ocfs2_delete_entry-failed.patch
ocfs2-set-filesytem-read-only-when-ocfs2_delete_entry-failed-v2.patch
ocfs2-avoid-access-invalid-address-when-read-o2dlm-debug-messages.patch
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