linux-kernel - Re: [PATCH 06/17] staging: lustre: tidy up ldlm_resource

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Date:   Fri, 30 Mar 2018 19:58:35 +0100 (BST)
From:   James Simmons <jsimmons@...radead.org>
To:     NeilBrown <neilb@...e.com>
cc:     Oleg Drokin <oleg.drokin@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andreas Dilger <andreas.dilger@...el.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Lustre Development List <lustre-devel@...ts.lustre.org>
Subject: Re: [PATCH 06/17] staging: lustre: tidy up ldlm_resource_putref()


> 1/ the return value of ldlm_resource_putref() is never
>   used, so change it to return 'void'.
> 2/ Move all of the code to run on the last putref to
>    __ldlm_resource_putref_final().  This means a lock
>    is taken in one function and dropped in another, but
>    that isn't too uncommon, and will disappear in a future
>    patch.
>    Now that the code it together, it becomes apparent that
>    we are dropping a ref on the namespace *before* the last
>    use.  So keep the ref until after.

Reviewed-by: James Simmons <jsimmons@...radead.org>
 
> Signed-off-by: NeilBrown <neilb@...e.com>
> ---
>  drivers/staging/lustre/lustre/include/lustre_dlm.h |    2 +-
>  drivers/staging/lustre/lustre/ldlm/ldlm_resource.c |   21 +++++++++-----------
>  2 files changed, 10 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/staging/lustre/lustre/include/lustre_dlm.h b/drivers/staging/lustre/lustre/include/lustre_dlm.h
> index 5a355fbab401..d668d86423a4 100644
> --- a/drivers/staging/lustre/lustre/include/lustre_dlm.h
> +++ b/drivers/staging/lustre/lustre/include/lustre_dlm.h
> @@ -1190,7 +1190,7 @@ struct ldlm_resource *ldlm_resource_get(struct ldlm_namespace *ns,
>  					struct ldlm_resource *parent,
>  					const struct ldlm_res_id *,
>  					enum ldlm_type type, int create);
> -int ldlm_resource_putref(struct ldlm_resource *res);
> +void ldlm_resource_putref(struct ldlm_resource *res);
>  void ldlm_resource_add_lock(struct ldlm_resource *res,
>  			    struct list_head *head,
>  			    struct ldlm_lock *lock);
> diff --git a/drivers/staging/lustre/lustre/ldlm/ldlm_resource.c b/drivers/staging/lustre/lustre/ldlm/ldlm_resource.c
> index 4c44603ab6f9..8841a1bb2c0a 100644
> --- a/drivers/staging/lustre/lustre/ldlm/ldlm_resource.c
> +++ b/drivers/staging/lustre/lustre/ldlm/ldlm_resource.c
> @@ -1195,6 +1195,7 @@ static void __ldlm_resource_putref_final(struct cfs_hash_bd *bd,
>  					 struct ldlm_resource *res)
>  {
>  	struct ldlm_ns_bucket *nsb = res->lr_ns_bucket;
> +	struct ldlm_namespace *ns = nsb->nsb_namespace;
>  
>  	if (!list_empty(&res->lr_granted)) {
>  		ldlm_resource_dump(D_ERROR, res);
> @@ -1206,15 +1207,18 @@ static void __ldlm_resource_putref_final(struct cfs_hash_bd *bd,
>  		LBUG();
>  	}
>  
> -	cfs_hash_bd_del_locked(nsb->nsb_namespace->ns_rs_hash,
> +	cfs_hash_bd_del_locked(ns->ns_rs_hash,
>  			       bd, &res->lr_hash);
>  	lu_ref_fini(&res->lr_reference);
> +	cfs_hash_bd_unlock(ns->ns_rs_hash, bd, 1);
> +	if (ns->ns_lvbo && ns->ns_lvbo->lvbo_free)
> +		ns->ns_lvbo->lvbo_free(res);
>  	if (cfs_hash_bd_count_get(bd) == 0)
> -		ldlm_namespace_put(nsb->nsb_namespace);
> +		ldlm_namespace_put(ns);
> +	kmem_cache_free(ldlm_resource_slab, res);
>  }
>  
> -/* Returns 1 if the resource was freed, 0 if it remains. */
> -int ldlm_resource_putref(struct ldlm_resource *res)
> +void ldlm_resource_putref(struct ldlm_resource *res)
>  {
>  	struct ldlm_namespace *ns = ldlm_res_to_ns(res);
>  	struct cfs_hash_bd   bd;
> @@ -1224,15 +1228,8 @@ int ldlm_resource_putref(struct ldlm_resource *res)
>  	       res, atomic_read(&res->lr_refcount) - 1);
>  
>  	cfs_hash_bd_get(ns->ns_rs_hash, &res->lr_name, &bd);
> -	if (cfs_hash_bd_dec_and_lock(ns->ns_rs_hash, &bd, &res->lr_refcount)) {
> +	if (cfs_hash_bd_dec_and_lock(ns->ns_rs_hash, &bd, &res->lr_refcount))
>  		__ldlm_resource_putref_final(&bd, res);
> -		cfs_hash_bd_unlock(ns->ns_rs_hash, &bd, 1);
> -		if (ns->ns_lvbo && ns->ns_lvbo->lvbo_free)
> -			ns->ns_lvbo->lvbo_free(res);
> -		kmem_cache_free(ldlm_resource_slab, res);
> -		return 1;
> -	}
> -	return 0;
>  }
>  EXPORT_SYMBOL(ldlm_resource_putref);
>  
> 
> 
>