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Date:   Wed, 2 May 2018 04:02:09 +0100 (BST)
From:   James Simmons <jsimmons@infradead.org>
To:     NeilBrown <neilb@suse.com>
cc:     Oleg Drokin <oleg.drokin@intel.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Andreas Dilger <andreas.dilger@intel.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Lustre Development List <lustre-devel@lists.lustre.org>
Subject: Re: [PATCH 02/10] staging: lustre: make struct lu_site_bkt_data
 private
In-Reply-To: <152514675889.17843.8198702967686860985.stgit@noble>
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References: <152514658325.17843.11455067361317157487.stgit@noble> <152514675889.17843.8198702967686860985.stgit@noble>
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> This data structure only needs to be public so that
> various modules can access a wait queue to wait for object
> destruction.
> If we provide a function to get the wait queue, rather than the
> whole bucket, the structure can be made private.
> 
> Signed-off-by: NeilBrown <neilb@suse.com>
> ---
>  drivers/staging/lustre/lustre/include/lu_object.h  |   36 +-------------
>  drivers/staging/lustre/lustre/llite/lcommon_cl.c   |    8 ++-
>  drivers/staging/lustre/lustre/lov/lov_object.c     |    8 ++-
>  drivers/staging/lustre/lustre/obdclass/lu_object.c |   50 +++++++++++++++++---
>  4 files changed, 54 insertions(+), 48 deletions(-)
> 
> diff --git a/drivers/staging/lustre/lustre/include/lu_object.h b/drivers/staging/lustre/lustre/include/lu_object.h
> index c3b0ed518819..f29bbca5af65 100644
> --- a/drivers/staging/lustre/lustre/include/lu_object.h
> +++ b/drivers/staging/lustre/lustre/include/lu_object.h
> @@ -549,31 +549,7 @@ struct lu_object_header {
>  };
>  
>  struct fld;
> -
> -struct lu_site_bkt_data {
> -	/**
> -	 * number of object in this bucket on the lsb_lru list.
> -	 */
> -	long			lsb_lru_len;
> -	/**
> -	 * LRU list, updated on each access to object. Protected by
> -	 * bucket lock of lu_site::ls_obj_hash.
> -	 *
> -	 * "Cold" end of LRU is lu_site::ls_lru.next. Accessed object are
> -	 * moved to the lu_site::ls_lru.prev (this is due to the non-existence
> -	 * of list_for_each_entry_safe_reverse()).
> -	 */
> -	struct list_head		lsb_lru;
> -	/**
> -	 * Wait-queue signaled when an object in this site is ultimately
> -	 * destroyed (lu_object_free()). It is used by lu_object_find() to
> -	 * wait before re-trying when object in the process of destruction is
> -	 * found in the hash table.
> -	 *
> -	 * \see htable_lookup().
> -	 */
> -	wait_queue_head_t	       lsb_marche_funebre;
> -};
> +struct lu_site_bkt_data;
>  
>  enum {
>  	LU_SS_CREATED	 = 0,
> @@ -642,14 +618,8 @@ struct lu_site {
>  	struct percpu_counter	 ls_lru_len_counter;
>  };
>  
> -static inline struct lu_site_bkt_data *
> -lu_site_bkt_from_fid(struct lu_site *site, struct lu_fid *fid)
> -{
> -	struct cfs_hash_bd bd;
> -
> -	cfs_hash_bd_get(site->ls_obj_hash, fid, &bd);
> -	return cfs_hash_bd_extra_get(site->ls_obj_hash, &bd);
> -}
> +wait_queue_head_t *
> +lu_site_wq_from_fid(struct lu_site *site, struct lu_fid *fid);
>  
>  static inline struct seq_server_site *lu_site2seq(const struct lu_site *s)
>  {
> diff --git a/drivers/staging/lustre/lustre/llite/lcommon_cl.c b/drivers/staging/lustre/lustre/llite/lcommon_cl.c
> index df5c0c0ae703..d5b42fb1d601 100644
> --- a/drivers/staging/lustre/lustre/llite/lcommon_cl.c
> +++ b/drivers/staging/lustre/lustre/llite/lcommon_cl.c
> @@ -211,12 +211,12 @@ static void cl_object_put_last(struct lu_env *env, struct cl_object *obj)
>  
>  	if (unlikely(atomic_read(&header->loh_ref) != 1)) {
>  		struct lu_site *site = obj->co_lu.lo_dev->ld_site;
> -		struct lu_site_bkt_data *bkt;
> +		wait_queue_head_t *wq;
>  
> -		bkt = lu_site_bkt_from_fid(site, &header->loh_fid);
> +		wq = lu_site_wq_from_fid(site, &header->loh_fid);
>  
>  		init_waitqueue_entry(&waiter, current);
> -		add_wait_queue(&bkt->lsb_marche_funebre, &waiter);
> +		add_wait_queue(wq, &waiter);
>  
>  		while (1) {
>  			set_current_state(TASK_UNINTERRUPTIBLE);
> @@ -226,7 +226,7 @@ static void cl_object_put_last(struct lu_env *env, struct cl_object *obj)
>  		}
>  
>  		set_current_state(TASK_RUNNING);
> -		remove_wait_queue(&bkt->lsb_marche_funebre, &waiter);
> +		remove_wait_queue(wq, &waiter);
>  	}
>  
>  	cl_object_put(env, obj);
> diff --git a/drivers/staging/lustre/lustre/lov/lov_object.c b/drivers/staging/lustre/lustre/lov/lov_object.c
> index f7c69680cb7d..adc90f310fd7 100644
> --- a/drivers/staging/lustre/lustre/lov/lov_object.c
> +++ b/drivers/staging/lustre/lustre/lov/lov_object.c
> @@ -370,7 +370,7 @@ static void lov_subobject_kill(const struct lu_env *env, struct lov_object *lov,
>  	struct cl_object	*sub;
>  	struct lov_layout_raid0 *r0;
>  	struct lu_site	  *site;
> -	struct lu_site_bkt_data *bkt;
> +	wait_queue_head_t *wq;
>  	wait_queue_entry_t	  *waiter;
>  
>  	r0  = &lov->u.raid0;
> @@ -378,7 +378,7 @@ static void lov_subobject_kill(const struct lu_env *env, struct lov_object *lov,
>  
>  	sub  = lovsub2cl(los);
>  	site = sub->co_lu.lo_dev->ld_site;
> -	bkt  = lu_site_bkt_from_fid(site, &sub->co_lu.lo_header->loh_fid);
> +	wq   = lu_site_wq_from_fid(site, &sub->co_lu.lo_header->loh_fid);
>  
>  	cl_object_kill(env, sub);
>  	/* release a reference to the sub-object and ... */
> @@ -391,7 +391,7 @@ static void lov_subobject_kill(const struct lu_env *env, struct lov_object *lov,
>  	if (r0->lo_sub[idx] == los) {
>  		waiter = &lov_env_info(env)->lti_waiter;
>  		init_waitqueue_entry(waiter, current);
> -		add_wait_queue(&bkt->lsb_marche_funebre, waiter);
> +		add_wait_queue(wq, waiter);
>  		set_current_state(TASK_UNINTERRUPTIBLE);
>  		while (1) {
>  			/* this wait-queue is signaled at the end of
> @@ -408,7 +408,7 @@ static void lov_subobject_kill(const struct lu_env *env, struct lov_object *lov,
>  				break;
>  			}
>  		}
> -		remove_wait_queue(&bkt->lsb_marche_funebre, waiter);
> +		remove_wait_queue(wq, waiter);
>  	}
>  	LASSERT(!r0->lo_sub[idx]);
>  }
> diff --git a/drivers/staging/lustre/lustre/obdclass/lu_object.c b/drivers/staging/lustre/lustre/obdclass/lu_object.c
> index 3de7dc0497c4..2a8a25d6edb5 100644
> --- a/drivers/staging/lustre/lustre/obdclass/lu_object.c
> +++ b/drivers/staging/lustre/lustre/obdclass/lu_object.c
> @@ -56,6 +56,31 @@
>  #include <lu_ref.h>
>  #include <linux/list.h>
>  
> +struct lu_site_bkt_data {
> +	/**
> +	 * number of object in this bucket on the lsb_lru list.
> +	 */
> +	long			lsb_lru_len;
> +	/**
> +	 * LRU list, updated on each access to object. Protected by
> +	 * bucket lock of lu_site::ls_obj_hash.
> +	 *
> +	 * "Cold" end of LRU is lu_site::ls_lru.next. Accessed object are
> +	 * moved to the lu_site::ls_lru.prev (this is due to the non-existence
> +	 * of list_for_each_entry_safe_reverse()).
> +	 */
> +	struct list_head		lsb_lru;
> +	/**
> +	 * Wait-queue signaled when an object in this site is ultimately
> +	 * destroyed (lu_object_free()). It is used by lu_object_find() to
> +	 * wait before re-trying when object in the process of destruction is
> +	 * found in the hash table.
> +	 *
> +	 * \see htable_lookup().
> +	 */
> +	wait_queue_head_t	       lsb_marche_funebre;
> +};
> +
>  enum {
>  	LU_CACHE_PERCENT_MAX	 = 50,
>  	LU_CACHE_PERCENT_DEFAULT = 20
> @@ -88,6 +113,17 @@ MODULE_PARM_DESC(lu_cache_nr, "Maximum number of objects in lu_object cache");
>  static void lu_object_free(const struct lu_env *env, struct lu_object *o);
>  static __u32 ls_stats_read(struct lprocfs_stats *stats, int idx);
>  
> +wait_queue_head_t *
> +lu_site_wq_from_fid(struct lu_site *site, struct lu_fid *fid)
> +{
> +	struct cfs_hash_bd bd;
> +	struct lu_site_bkt_data *bkt;
> +
> +	cfs_hash_bd_get(site->ls_obj_hash, fid, &bd);
> +	bkt = cfs_hash_bd_extra_get(site->ls_obj_hash, &bd);
> +	return &bkt->lsb_marche_funebre;
> +}
> +

Nak. You forgot the EXPORT_SYMBOL for this. Once I added the export symbol
it seems to work so far in my testing.

>  /**
>   * Decrease reference counter on object. If last reference is freed, return
>   * object to the cache, unless lu_object_is_dying(o) holds. In the latter
> @@ -288,7 +324,7 @@ static struct lu_object *lu_object_alloc(const struct lu_env *env,
>   */
>  static void lu_object_free(const struct lu_env *env, struct lu_object *o)
>  {
> -	struct lu_site_bkt_data *bkt;
> +	wait_queue_head_t *wq;
>  	struct lu_site	  *site;
>  	struct lu_object	*scan;
>  	struct list_head	      *layers;
> @@ -296,7 +332,7 @@ static void lu_object_free(const struct lu_env *env, struct lu_object *o)
>  
>  	site   = o->lo_dev->ld_site;
>  	layers = &o->lo_header->loh_layers;
> -	bkt    = lu_site_bkt_from_fid(site, &o->lo_header->loh_fid);
> +	wq     = lu_site_wq_from_fid(site, &o->lo_header->loh_fid);
>  	/*
>  	 * First call ->loo_object_delete() method to release all resources.
>  	 */
> @@ -324,8 +360,8 @@ static void lu_object_free(const struct lu_env *env, struct lu_object *o)
>  		o->lo_ops->loo_object_free(env, o);
>  	}
>  
> -	if (waitqueue_active(&bkt->lsb_marche_funebre))
> -		wake_up_all(&bkt->lsb_marche_funebre);
> +	if (waitqueue_active(wq))
> +		wake_up_all(wq);
>  }
>  
>  /**
> @@ -749,7 +785,7 @@ struct lu_object *lu_object_find_at(const struct lu_env *env,
>  				    const struct lu_fid *f,
>  				    const struct lu_object_conf *conf)
>  {
> -	struct lu_site_bkt_data *bkt;
> +	wait_queue_head_t	*wq;
>  	struct lu_object	*obj;
>  	wait_queue_entry_t	   wait;
>  
> @@ -762,8 +798,8 @@ struct lu_object *lu_object_find_at(const struct lu_env *env,
>  		 * wait queue.
>  		 */
>  		schedule();
> -		bkt = lu_site_bkt_from_fid(dev->ld_site, (void *)f);
> -		remove_wait_queue(&bkt->lsb_marche_funebre, &wait);
> +		wq = lu_site_wq_from_fid(dev->ld_site, (void *)f);
> +		remove_wait_queue(wq, &wait);
>  	}
>  }
>  EXPORT_SYMBOL(lu_object_find_at);
> 
> 
>