Re: [PATCH 1/8] hugetlb: make mm and fs code explicitly non-modular

[Mike Kravetz <mike.kravetz@oracle.com>]

On 12/17/2015 11:10 AM, 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 driver there is no doubt it is builtin-only.
> 
> Since module_init translates to device_initcall in the non-modular
> case, the init ordering gets moved to earlier levels when we use the
> more appropriate initcalls here.
> 
> Originally I had the fs part and the mm part as separate commits,
> just by happenstance of the nature of how I detected these
> non-modular use cases.  But that can possibly introduce regressions
> if the patch merge ordering puts the fs part 1st -- as the 0-day
> testing reported a splat at mount time.
> 
> Investigating with "initcall_debug" showed that the delta was
> init_hugetlbfs_fs being called _before_ hugetlb_init instead of
> after.  So both the fs change and the mm change are here together.
> 
> In addition, it worked before due to luck of link order, since they
> were both in the same initcall category.  So we now have the fs
> part using fs_initcall, and the mm part using subsys_initcall,
> which puts it one bucket earlier.  It now passes the basic sanity
> test that failed in earlier 0-day testing.
> 
> We delete the MODULE_LICENSE tag and capture that information at the
> top of the file alongside author comments, etc.
> 
> We don't replace module.h with init.h since the file already has that.
> Also note that MODULE_ALIAS is a no-op for non-modular code.
> 
> Cc: Nadia Yvette Chambers <nyc@holomorphy.com>
> Cc: Alexander Viro <viro@zeniv.linux.org.uk>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
> Cc: Mike Kravetz <mike.kravetz@oracle.com>
> Cc: David Rientjes <rientjes@google.com>
> Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
> Cc: Davidlohr Bueso <dave@stgolabs.net>
> Cc: linux-mm@kvack.org
> Cc: linux-fsdevel@vger.kernel.org
> Reported-by: kernel test robot <ying.huang@linux.intel.com>
> Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
> ---
>  fs/hugetlbfs/inode.c | 27 ++-------------------------
>  mm/hugetlb.c         | 39 +--------------------------------------
>  2 files changed, 3 insertions(+), 63 deletions(-)
> 
> diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
> index de4bdfac0cec..dd04c2ad23b3 100644
> --- a/fs/hugetlbfs/inode.c
> +++ b/fs/hugetlbfs/inode.c
> @@ -4,11 +4,11 @@
>   * Nadia Yvette Chambers, 2002
>   *
>   * Copyright (C) 2002 Linus Torvalds.
> + * License: GPL
>   */
>  
>  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
>  
> -#include <linux/module.h>
>  #include <linux/thread_info.h>
>  #include <asm/current.h>
>  #include <linux/sched.h>		/* remove ASAP */
> @@ -1201,7 +1201,6 @@ static struct file_system_type hugetlbfs_fs_type = {
>  	.mount		= hugetlbfs_mount,
>  	.kill_sb	= kill_litter_super,
>  };
> -MODULE_ALIAS_FS("hugetlbfs");
>  
>  static struct vfsmount *hugetlbfs_vfsmount[HUGE_MAX_HSTATE];
>  
> @@ -1355,26 +1354,4 @@ static int __init init_hugetlbfs_fs(void)
>   out2:
>  	return error;
>  }
> -
> -static void __exit exit_hugetlbfs_fs(void)
> -{
> -	struct hstate *h;
> -	int i;
> -
> -
> -	/*
> -	 * Make sure all delayed rcu free inodes are flushed before we
> -	 * destroy cache.
> -	 */
> -	rcu_barrier();
> -	kmem_cache_destroy(hugetlbfs_inode_cachep);
> -	i = 0;
> -	for_each_hstate(h)
> -		kern_unmount(hugetlbfs_vfsmount[i++]);
> -	unregister_filesystem(&hugetlbfs_fs_type);
> -}
> -
> -module_init(init_hugetlbfs_fs)
> -module_exit(exit_hugetlbfs_fs)
> -
> -MODULE_LICENSE("GPL");
> +fs_initcall(init_hugetlbfs_fs)
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index ef6963b577fd..be934df69b85 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>
> @@ -2549,25 +2548,6 @@ 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.
> @@ -2632,27 +2612,10 @@ 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;
> @@ -2690,7 +2653,7 @@ static int __init hugetlb_init(void)
>  		mutex_init(&hugetlb_fault_mutex_table[i]);
>  	return 0;
>  }
> -module_init(hugetlb_init);
> +subsys_initcall(hugetlb_init);
>  
>  /* Should be called on processing a hugepagesz=... option */
>  void __init hugetlb_add_hstate(unsigned int order)
> 

I like the removal of code.
Reviewed-By: Mike Kravetz <mike.kravetz@oracle.com>

-- 
Mike Kravetz