hugetlb: make mm and fs code explicitly non-modular

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.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Reported-by: kernel test robot <ying.huang@linux.intel.com>
Cc: Nadia Yvette Chambers <nyc@holomorphy.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Acked-by: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

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 */
@@ -1202,7 +1202,6 @@ 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];
 
@@ -1356,26 +1355,4 @@ 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)

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)