mm/mm_init.c: remove obsolete macro HASH_SMALL

HASH_SMALL only works when parameter numentries is 0. But the sole caller
futex_init() never calls alloc_large_system_hash() with numentries set to
0. So HASH_SMALL is obsolete and remove it.

Link: https://lkml.kernel.org/r/20230625021323.849147-1-linmiaohe@huawei.comSigned-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: André Almeida <andrealmeid@igalia.com>
Cc: Darren Hart <dvhart@infradead.org>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/linux/memblock.h

@@ -581,9 +581,7 @@ extern void *alloc_large_system_hash(const char *tablename,
 				     unsigned long high_limit);
 
 #define HASH_EARLY	0x00000001	/* Allocating during early boot? */
-#define HASH_SMALL	0x00000002	/* sub-page allocation allowed, min
-					 * shift passed via *_hash_shift */
-#define HASH_ZERO	0x00000004	/* Zero allocated hash table */
+#define HASH_ZERO	0x00000002	/* Zero allocated hash table */
 
 /* Only NUMA needs hash distribution. 64bit NUMA architectures have
  * sufficient vmalloc space.

kernel/futex/core.c

@@ -1132,8 +1132,7 @@ static int __init futex_init(void)
 #endif
 
 	futex_queues = alloc_large_system_hash("futex", sizeof(*futex_queues),
-					       futex_hashsize, 0,
-					       futex_hashsize < 256 ? HASH_SMALL : 0,
+					       futex_hashsize, 0, 0,
 					       &futex_shift, NULL,
 					       futex_hashsize, futex_hashsize);
 	futex_hashsize = 1UL << futex_shift;

mm/mm_init.c

@@ -2489,15 +2489,7 @@ void *__init alloc_large_system_hash(const char *tablename,
 		else
 			numentries <<= (PAGE_SHIFT - scale);
 
-		/* Make sure we've got at least a 0-order allocation.. */
-		if (unlikely(flags & HASH_SMALL)) {
-			/* Makes no sense without HASH_EARLY */
-			WARN_ON(!(flags & HASH_EARLY));
-			if (!(numentries >> *_hash_shift)) {
-				numentries = 1UL << *_hash_shift;
-				BUG_ON(!numentries);
-			}
-		} else if (unlikely((numentries * bucketsize) < PAGE_SIZE))
+		if (unlikely((numentries * bucketsize) < PAGE_SIZE))
 			numentries = PAGE_SIZE / bucketsize;
 	}
 	numentries = roundup_pow_of_two(numentries);