[Ocfs2-devel] [PATCH] ocfs2/dlm: remove BUG_ON in a rare case

[Sunil Mushran <sunil.mushran@oracle.com>]

Signed-off-by: Sunil Mushran<sunil.mushran@oracle.com>


On 07/14/2010 07:38 AM, Wengang Wang wrote:
> For migration, we are waiting for DLM_LOCK_RES_MIGRATING flag to be set
> before sending DLM_MIG_LOCKRES_MSG message to the target. We are using
> dlm_migration_can_proceed() for that purpose. while, dlm_migration_can_proceed()
> also returns "go ahead" if target node is down. In this rare case, the
> DLM_LOCK_RES_MIGRATING maybe is not set yet. Remove the BUG_ON() in this case.
>
> Signed-off-by: Wengang Wang<wen.gang.wang@oracle.com>
> ---
>   fs/ocfs2/dlm/dlmmaster.c |   22 ++++++++++++++--------
>   1 files changed, 14 insertions(+), 8 deletions(-)
>
> diff --git a/fs/ocfs2/dlm/dlmmaster.c b/fs/ocfs2/dlm/dlmmaster.c
> index 4a7506a..94b97fc 100644
> --- a/fs/ocfs2/dlm/dlmmaster.c
> +++ b/fs/ocfs2/dlm/dlmmaster.c
> @@ -2808,14 +2808,8 @@ again:
>   		mlog(0, "trying again...\n");
>   		goto again;
>   	}
> -	/* now that we are sure the MIGRATING state is there, drop
> -	 * the unneded state which blocked threads trying to DIRTY */
> -	spin_lock(&res->spinlock);
> -	BUG_ON(!(res->state&  DLM_LOCK_RES_BLOCK_DIRTY));
> -	BUG_ON(!(res->state&  DLM_LOCK_RES_MIGRATING));
> -	res->state&= ~DLM_LOCK_RES_BLOCK_DIRTY;
> -	spin_unlock(&res->spinlock);
>
> +	ret = 0;
>   	/* did the target go down or die? */
>   	spin_lock(&dlm->spinlock);
>   	if (!test_bit(target, dlm->domain_map)) {
> @@ -2826,9 +2820,21 @@ again:
>   	spin_unlock(&dlm->spinlock);
>
>   	/*
> +	 * if target is down, we need to clear DLM_LOCK_RES_BLOCK_DIRTY for
> +	 * another try; otherwise, we are sure the MIGRATING state is there,
> +	 * drop the unneded state which blocked threads trying to DIRTY
> +	 */
> +	spin_lock(&res->spinlock);
> +	BUG_ON(!(res->state&  DLM_LOCK_RES_BLOCK_DIRTY));
> +	res->state&= ~DLM_LOCK_RES_BLOCK_DIRTY;
> +	if (!ret)
> +		BUG_ON(!(res->state&  DLM_LOCK_RES_MIGRATING));
> +	spin_unlock(&res->spinlock);
> +
> +	/*
>   	 * at this point:
>   	 *
> -	 *   o the DLM_LOCK_RES_MIGRATING flag is set
> +	 *   o the DLM_LOCK_RES_MIGRATING flag is set if target not down
>   	 *   o there are no pending asts on this lockres
>   	 *   o all processes trying to reserve an ast on this
>   	 *     lockres must wait for the MIGRATING flag to clear
>