hugetlbfs: correct handling of negative input to /proc/sys/vm/nr_hugepages

When the user inserts a negative value into /proc/sys/vm/nr_hugepages it
will cause the kernel to allocate as many hugepages as possible and to
then update /proc/meminfo to reflect this.

This changes the behavior so that the negative input will result in
nr_hugepages value being unchanged.
Signed-off-by: Petr Holasek <pholasek@redhat.com>
Signed-off-by: Anton Arapov <anton@redhat.com>
Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Acked-by: David Rientjes <rientjes@google.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Acked-by: Eric B Munson <emunson@mgebm.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/hugetlb.c

@@ -1872,8 +1872,7 @@ static int hugetlb_sysctl_handler_common(bool obey_mempolicy,
 	unsigned long tmp;
 	int ret;
 
-	if (!write)
-		tmp = h->max_huge_pages;
+	tmp = h->max_huge_pages;
 
 	if (write && h->order >= MAX_ORDER)
 		return -EINVAL;
@@ -1938,8 +1937,7 @@ int hugetlb_overcommit_handler(struct ctl_table *table, int write,
 	unsigned long tmp;
 	int ret;
 
-	if (!write)
-		tmp = h->nr_overcommit_huge_pages;
+	tmp = h->nr_overcommit_huge_pages;
 
 	if (write && h->order >= MAX_ORDER)
 		return -EINVAL;