sparc/mm: fix MAX_ORDER usage in tsb_grow()

Patch series "Fix confusion around MAX_ORDER".

MAX_ORDER currently defined as number of orders page allocator supports:
user can ask buddy allocator for page order between 0 and MAX_ORDER-1.

This definition is counter-intuitive and lead to number of bugs all over
the kernel.

Fix the bugs and then change the definition of MAX_ORDER to be
inclusive: the range of orders user can ask from buddy allocator is
0..MAX_ORDER now.


This patch (of 10):

MAX_ORDER is not inclusive: the maximum allocation order buddy allocator
can deliver is MAX_ORDER-1.

Fix MAX_ORDER usage in tsb_grow().

Link: https://lkml.kernel.org/r/20230315113133.11326-1-kirill.shutemov@linux.intel.com
Link: https://lkml.kernel.org/r/20230315113133.11326-2-kirill.shutemov@linux.intel.comSigned-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Acked-by: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: David Miller <davem@davemloft.net>
Cc: David Hildenbrand <david@redhat.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

arch/sparc/mm/tsb.c

@@ -402,8 +402,8 @@ void tsb_grow(struct mm_struct *mm, unsigned long tsb_index, unsigned long rss)
 	unsigned long new_rss_limit;
 	gfp_t gfp_flags;
 
-	if (max_tsb_size > (PAGE_SIZE << MAX_ORDER))
-		max_tsb_size = (PAGE_SIZE << MAX_ORDER);
+	if (max_tsb_size > (PAGE_SIZE << (MAX_ORDER - 1)))
+		max_tsb_size = (PAGE_SIZE << (MAX_ORDER - 1));
 
 	new_cache_index = 0;
 	for (new_size = 8192; new_size < max_tsb_size; new_size <<= 1UL) {