ocfs2: o2dlm fix race in purge lockres and newlock (orabug 9094491) -backport to 1.2

This patch fixes the following hole.
dlmlock tries to create a new lock on a lockres that is on purge list. It calls dlm_get_lockresource and later adds a lock to blocked list. But in this window, dlm_thread can purge the lockres and unhash it. This will cause a BUG, as when the AST comes back from the master lockres is not found

This patch marks the lockres with a new state DLM_LOCK_RES_IN_USE which would protect lockres from dlm_thread purging it.

Signed-off-by Srinivas Eeda<[email protected]>

Signed-off-by Sunil Mushran<[email protected]>

---
  dlmcommon.h |    1 +
  dlmlock.c   |    4 ++++
  dlmmaster.c |    5 ++++-
  dlmthread.c |    1 +
  4 files changed, 10 insertions(+), 1 deletion(-)

diff -upr ocfs2-1.2.9-8-test/fs/ocfs2/dlm/dlmcommon.h ocfs2-1.2.9-8.2/fs/ocfs2/dlm/dlmcommon.h

fs/ocfs2/dlm/dlmcommon.h +1 -0

@@ -218,6 +218,7 @@ static inline void __dlm_set_joining_nod
  #define DLM_LOCK_RES_IN_PROGRESS          0x00000010
  #define DLM_LOCK_RES_MIGRATING            0x00000020
  #define DLM_LOCK_RES_DROPPING_REF         0x00000040
+#define DLM_LOCK_RES_IN_USE               0x00000100
  #define DLM_LOCK_RES_BLOCK_DIRTY          0x00001000
  #define DLM_LOCK_RES_SETREF_INPROG        0x00002000
 

diff -upr ocfs2-1.2.9-8-test/fs/ocfs2/dlm/dlmlock.c ocfs2-1.2.9-8.2/fs/ocfs2/dlm/dlmlock.c

fs/ocfs2/dlm/dlmlock.c +4 -0

@@ -116,6 +116,8 @@ static enum dlm_status dlmlock_master(st
  	if (status != DLM_NORMAL&&
  	lock->ml.node != dlm->node_num) {
  		/* erf.  state changed after lock was dropped. */
+		/* DLM_LOCK_RES_IN_USE is set in dlm_get_lock_resource */
+		res->state&= ~DLM_LOCK_RES_IN_USE;
  		spin_unlock(&res->spinlock);
  		dlm_error(status);
  		return status;

@@ -162,6 +164,7 @@ static enum dlm_status dlmlock_master(st
  			kick_thread = 1;
  		}
  	}
+	res->state&= ~DLM_LOCK_RES_IN_USE;
  	/* reduce the inflight count, this may result in the lockres
  	 * being purged below during calc_usage */
  	if (lock->ml.node == dlm->node_num)

@@ -228,6 +231,7 @@ static enum dlm_status dlmlock_remote(st
 
  	spin_lock(&res->spinlock);
  	res->state&= ~DLM_LOCK_RES_IN_PROGRESS;
+	res->state&= ~DLM_LOCK_RES_IN_USE;
  	lock->lock_pending = 0;
  	if (status != DLM_NORMAL) {
  		if (status == DLM_RECOVERING&&

diff -upr ocfs2-1.2.9-8-test/fs/ocfs2/dlm/dlmmaster.c ocfs2-1.2.9-8.2/fs/ocfs2/dlm/dlmmaster.c

fs/ocfs2/dlm/dlmmaster.c +4 -1

@@ -804,12 +804,15 @@ lookup:
  	if (tmpres) {
  		int dropping_ref = 0;
 
+		tmpres->state |= DLM_LOCK_RES_IN_USE;
  		spin_lock(&tmpres->spinlock);
  		if (tmpres->owner == dlm->node_num) {
  			BUG_ON(tmpres->state&  DLM_LOCK_RES_DROPPING_REF);
  			dlm_lockres_grab_inflight_ref(dlm, tmpres);
-		} else if (tmpres->state&  DLM_LOCK_RES_DROPPING_REF)
+		} else if (tmpres->state&  DLM_LOCK_RES_DROPPING_REF) {
+			tmpres->state&= ~DLM_LOCK_RES_IN_USE;
  			dropping_ref = 1;
+		}
  		spin_unlock(&tmpres->spinlock);
  		spin_unlock(&dlm->spinlock);
 

diff -upr ocfs2-1.2.9-8-test/fs/ocfs2/dlm/dlmthread.c ocfs2-1.2.9-8.2/fs/ocfs2/dlm/dlmthread.c

fs/ocfs2/dlm/dlmthread.c +1 -0

@@ -97,6 +97,7 @@ int __dlm_lockres_has_locks(struct dlm_l
  int __dlm_lockres_unused(struct dlm_lock_resource *res)
  {
  	if (!__dlm_lockres_has_locks(res)&&
+	    !(res->state&  DLM_LOCK_RES_IN_USE)&&
  	(list_empty(&res->dirty)&&  !(res->state&  DLM_LOCK_RES_DIRTY))) {
  		/* try not to scan the bitmap unless the first two
  		 * conditions are already true */

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