linux-kernel - Re: [PATCH 03/10] mm: make hugetlb.c explicitly non-modular

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Date:	Wed, 26 Aug 2015 09:47:13 -0700
From:	Mike Kravetz <mike.kravetz@...cle.com>
To:	Paul Gortmaker <paul.gortmaker@...driver.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	David Rientjes <rientjes@...gle.com>,
	Hillf Danton <hillf.zj@...baba-inc.com>,
	Davidlohr Bueso <dave@...olabs.net>
Subject: Re: [PATCH 03/10] mm: make hugetlb.c explicitly non-modular

On 08/24/2015 03:14 PM, Paul Gortmaker wrote:
> The Kconfig currently controlling compilation of this code is:
> 
> config HUGETLBFS
>         bool "HugeTLB file system support"
> 
> ...meaning that it currently is not being built as a module by anyone.
> 
> Lets remove the modular code that is essentially orphaned, so that
> when reading the file there is no doubt it is builtin-only.
> 
> Since module_init translates to device_initcall in the non-modular
> case, the init ordering remains unchanged with this commit.  However
> one could argue that fs_initcall() would make more sense here.

I would prefer that it NOT be changed to fs_initcall() as this is more
about generic mm code than fs code.  If this was in a hugetlbfs specific
file, fs_initcall() might make more sense.

More about changing initcall below.

> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
> Cc: Mike Kravetz <mike.kravetz@...cle.com>
> Cc: David Rientjes <rientjes@...gle.com>
> Cc: Hillf Danton <hillf.zj@...baba-inc.com>
> Cc: Davidlohr Bueso <dave@...olabs.net>
> Cc: linux-mm@...ck.org
> Signed-off-by: Paul Gortmaker <paul.gortmaker@...driver.com>
> ---
>  mm/hugetlb.c | 39 +--------------------------------------
>  1 file changed, 1 insertion(+), 38 deletions(-)
> 
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 586aa69df900..1154152c8b99 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -4,7 +4,6 @@
>   */
>  #include <linux/list.h>
>  #include <linux/init.h>
> -#include <linux/module.h>
>  #include <linux/mm.h>
>  #include <linux/seq_file.h>
>  #include <linux/sysctl.h>
> @@ -2439,25 +2438,6 @@ static void hugetlb_unregister_node(struct node *node)
>  	nhs->hugepages_kobj = NULL;
>  }
>  
> -/*
> - * hugetlb module exit:  unregister hstate attributes from node devices
> - * that have them.
> - */
> -static void hugetlb_unregister_all_nodes(void)
> -{
> -	int nid;
> -
> -	/*
> -	 * disable node device registrations.
> -	 */
> -	register_hugetlbfs_with_node(NULL, NULL);
> -
> -	/*
> -	 * remove hstate attributes from any nodes that have them.
> -	 */
> -	for (nid = 0; nid < nr_node_ids; nid++)
> -		hugetlb_unregister_node(node_devices[nid]);
> -}
>  
>  /*
>   * Register hstate attributes for a single node device.
> @@ -2522,27 +2502,10 @@ static struct hstate *kobj_to_node_hstate(struct kobject *kobj, int *nidp)
>  	return NULL;
>  }
>  
> -static void hugetlb_unregister_all_nodes(void) { }
> -
>  static void hugetlb_register_all_nodes(void) { }
>  
>  #endif
>  
> -static void __exit hugetlb_exit(void)
> -{
> -	struct hstate *h;
> -
> -	hugetlb_unregister_all_nodes();
> -
> -	for_each_hstate(h) {
> -		kobject_put(hstate_kobjs[hstate_index(h)]);
> -	}
> -
> -	kobject_put(hugepages_kobj);
> -	kfree(hugetlb_fault_mutex_table);
> -}
> -module_exit(hugetlb_exit);
> -
>  static int __init hugetlb_init(void)
>  {
>  	int i;
> @@ -2580,7 +2543,7 @@ static int __init hugetlb_init(void)
>  		mutex_init(&hugetlb_fault_mutex_table[i]);
>  	return 0;
>  }

I am all for removal of the module_exit and associated code.  It is
dead and is not used today.  It would be a good idea to remove this
in any case.

> -module_init(hugetlb_init);
> +device_initcall(hugetlb_init);

Other more experienced people have opinions on your staged approach
to changing these init calls.  If the consensus is to take this
approach, I would have no objections.

-- 
Mike Kravetz

>  
>  /* Should be called on processing a hugepagesz=... option */
>  void __init hugetlb_add_hstate(unsigned order)
> 
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