[Ocfs2-devel] [PATCH 2/2] ocfs2: o2dlm fix race in purge lockres and newlock (orabug 9094491) -backport to 1.2

[Sunil Mushran]

Just to be clear. This is just an interim patch for 1.2. Not for
inclusion in mainline.

On 06/26/2010 04:32 AM, Wengang Wang wrote:
> 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<srinivas.eeda at oracle.com>
> Signed-off-by: Sunil Mushran<sunil.mushran at oracle.com>
> ---
>   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
> --- ocfs2-1.2.9-8-test/fs/ocfs2/dlm/dlmcommon.h	2010-06-26 19:04:32.000000000 +0800
> +++ ocfs2-1.2.9-8.2/fs/ocfs2/dlm/dlmcommon.h	2010-06-26 19:18:33.000000000 +0800
> @@ -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
> --- ocfs2-1.2.9-8-test/fs/ocfs2/dlm/dlmlock.c	2010-06-26 19:04:22.000000000 +0800
> +++ ocfs2-1.2.9-8.2/fs/ocfs2/dlm/dlmlock.c	2010-06-26 19:21:06.000000000 +0800
> @@ -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
> --- ocfs2-1.2.9-8-test/fs/ocfs2/dlm/dlmmaster.c	2010-06-26 19:04:22.000000000 +0800
> +++ ocfs2-1.2.9-8.2/fs/ocfs2/dlm/dlmmaster.c	2010-06-26 19:23:57.000000000 +0800
> @@ -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
> --- ocfs2-1.2.9-8-test/fs/ocfs2/dlm/dlmthread.c	2010-06-26 19:04:32.000000000 +0800
> +++ ocfs2-1.2.9-8.2/fs/ocfs2/dlm/dlmthread.c	2010-06-26 19:25:06.000000000 +0800
> @@ -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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