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Date:   Fri, 7 Aug 2020 20:54:25 +0800
From:   Baoquan He <bhe@redhat.com>
To:     Wei Yang <richard.weiyang@linux.alibaba.com>
Cc:     mike.kravetz@oracle.com, akpm@linux-foundation.org,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 04/10] mm/hugetlb: count file_region to be added when
 regions_needed != NULL
Message-ID: <20200807125425.GO14854@MiWiFi-R3L-srv>
References: <20200807091251.12129-1-richard.weiyang@linux.alibaba.com>
 <20200807091251.12129-5-richard.weiyang@linux.alibaba.com>
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On 08/07/20 at 05:12pm, Wei Yang wrote:
> There are only two cases of function add_reservation_in_range()
> 
>     * count file_region and return the number in regions_needed
>     * do the real list operation without counting
> 
> This means it is not necessary to have two parameters to classify these
> two cases.
> 
> Just use regions_needed to separate them.
> 
> Signed-off-by: Wei Yang <richard.weiyang@linux.alibaba.com>

Nice clean up.

Reviewed-by: Baoquan He <bhe@redhat.com>

> ---
>  mm/hugetlb.c | 33 +++++++++++++++++----------------
>  1 file changed, 17 insertions(+), 16 deletions(-)
> 
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 929256c130f9..d775e514eb2e 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -321,16 +321,17 @@ static void coalesce_file_region(struct resv_map *resv, struct file_region *rg)
>  	}
>  }
>  
> -/* Must be called with resv->lock held. Calling this with count_only == true
> - * will count the number of pages to be added but will not modify the linked
> - * list. If regions_needed != NULL and count_only == true, then regions_needed
> - * will indicate the number of file_regions needed in the cache to carry out to
> - * add the regions for this range.
> +/*
> + * Must be called with resv->lock held.
> + *
> + * Calling this with regions_needed != NULL will count the number of pages
> + * to be added but will not modify the linked list. And regions_needed will
> + * indicate the number of file_regions needed in the cache to carry out to add
> + * the regions for this range.
>   */
>  static long add_reservation_in_range(struct resv_map *resv, long f, long t,
>  				     struct hugetlb_cgroup *h_cg,
> -				     struct hstate *h, long *regions_needed,
> -				     bool count_only)
> +				     struct hstate *h, long *regions_needed)
>  {
>  	long add = 0;
>  	struct list_head *head = &resv->regions;
> @@ -366,14 +367,14 @@ static long add_reservation_in_range(struct resv_map *resv, long f, long t,
>  		 */
>  		if (rg->from > last_accounted_offset) {
>  			add += rg->from - last_accounted_offset;
> -			if (!count_only) {
> +			if (!regions_needed) {
>  				nrg = get_file_region_entry_from_cache(
>  					resv, last_accounted_offset, rg->from);
>  				record_hugetlb_cgroup_uncharge_info(h_cg, h,
>  								    resv, nrg);
>  				list_add(&nrg->link, rg->link.prev);
>  				coalesce_file_region(resv, nrg);
> -			} else if (regions_needed)
> +			} else
>  				*regions_needed += 1;
>  		}
>  
> @@ -385,13 +386,13 @@ static long add_reservation_in_range(struct resv_map *resv, long f, long t,
>  	 */
>  	if (last_accounted_offset < t) {
>  		add += t - last_accounted_offset;
> -		if (!count_only) {
> +		if (!regions_needed) {
>  			nrg = get_file_region_entry_from_cache(
>  				resv, last_accounted_offset, t);
>  			record_hugetlb_cgroup_uncharge_info(h_cg, h, resv, nrg);
>  			list_add(&nrg->link, rg->link.prev);
>  			coalesce_file_region(resv, nrg);
> -		} else if (regions_needed)
> +		} else
>  			*regions_needed += 1;
>  	}
>  
> @@ -484,8 +485,8 @@ static long region_add(struct resv_map *resv, long f, long t,
>  retry:
>  
>  	/* Count how many regions are actually needed to execute this add. */
> -	add_reservation_in_range(resv, f, t, NULL, NULL, &actual_regions_needed,
> -				 true);
> +	add_reservation_in_range(resv, f, t, NULL, NULL,
> +				 &actual_regions_needed);
>  
>  	/*
>  	 * Check for sufficient descriptors in the cache to accommodate
> @@ -513,7 +514,7 @@ static long region_add(struct resv_map *resv, long f, long t,
>  		goto retry;
>  	}
>  
> -	add = add_reservation_in_range(resv, f, t, h_cg, h, NULL, false);
> +	add = add_reservation_in_range(resv, f, t, h_cg, h, NULL);
>  
>  	resv->adds_in_progress -= in_regions_needed;
>  
> @@ -549,9 +550,9 @@ static long region_chg(struct resv_map *resv, long f, long t,
>  
>  	spin_lock(&resv->lock);
>  
> -	/* Count how many hugepages in this range are NOT respresented. */
> +	/* Count how many hugepages in this range are NOT represented. */
>  	chg = add_reservation_in_range(resv, f, t, NULL, NULL,
> -				       out_regions_needed, true);
> +				       out_regions_needed);
>  
>  	if (*out_regions_needed == 0)
>  		*out_regions_needed = 1;
> -- 
> 2.20.1 (Apple Git-117)
> 
>