hugetlb: multiple hstates for multiple page sizes

Add basic support for more than one hstate in hugetlbfs.  This is the key
to supporting multiple hugetlbfs page sizes at once.

- Rather than a single hstate, we now have an array, with an iterator
- default_hstate continues to be the struct hstate which we use by default
- Add functions for architectures to register new hstates

[akpm@linux-foundation.org: coding-style fixes]
Acked-by: Adam Litke <agl@us.ibm.com>
Acked-by: Nishanth Aravamudan <nacc@us.ibm.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/sysctl.c

@@ -959,7 +959,7 @@ static struct ctl_table vm_table[] = {
 #ifdef CONFIG_HUGETLB_PAGE
 	 {
 		.procname	= "nr_hugepages",
-		.data		= &max_huge_pages,
+		.data		= NULL,
 		.maxlen		= sizeof(unsigned long),
 		.mode		= 0644,
 		.proc_handler	= &hugetlb_sysctl_handler,
@@ -985,10 +985,12 @@ static struct ctl_table vm_table[] = {
 	{
 		.ctl_name	= CTL_UNNUMBERED,
 		.procname	= "nr_overcommit_hugepages",
-		.data		= &sysctl_overcommit_huge_pages,
-		.maxlen		= sizeof(sysctl_overcommit_huge_pages),
+		.data		= NULL,
+		.maxlen		= sizeof(unsigned long),
 		.mode		= 0644,
 		.proc_handler	= &hugetlb_overcommit_handler,
+		.extra1		= (void *)&hugetlb_zero,
+		.extra2		= (void *)&hugetlb_infinity,
 	},
 #endif
 	{