linux-kernel - [PATCH] mm: kmalloc_index: remove case when size is more than 32MB

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Date:   Sun,  9 May 2021 07:13:28 +0900
From:   Hyeonggon Yoo <42.hyeyoo@...il.com>
To:     cl@...ux.com, penberg@...nel.org, rientjes@...gle.com,
        iamjoonsoo.kim@....com, vbabka@...e.cz
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Hyeonggon Yoo <42.hyeyoo@...il.com>
Subject: [PATCH] mm: kmalloc_index: remove case when size is more than 32MB

the return value of kmalloc_index is used as index of kmalloc_caches,
which is defined as:
  struct kmem_cache *
  kmalloc_caches[NR_KMALLOC_TYPES][KMALLOC_SHIFT_HIGH + 1]

and KMALLOC_SHIFT_HIGH is defined as:
  #define KMALLOC_SHIFT_HIGH    ((MAX_ORDER + PAGE_SHIFT - 1) <= 25 ? \
                              (MAX_ORDER + PAGE_SHIFT - 1) : 25)

KMALLOC_SHIFT_HIGH is maximum 25 by its definition. thus index of
kmalloc_caches cannot be 26. so this case should be removed.

Signed-off-by: Hyeonggon Yoo <42.hyeyoo@...il.com>
---
 include/linux/slab.h | 1 -
 1 file changed, 1 deletion(-)

diff --git a/include/linux/slab.h b/include/linux/slab.h
index 0c97d788762c..4694b1db4cb2 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -382,7 +382,6 @@ static __always_inline unsigned int kmalloc_index(size_t size)
 	if (size <=  8 * 1024 * 1024) return 23;
 	if (size <=  16 * 1024 * 1024) return 24;
 	if (size <=  32 * 1024 * 1024) return 25;
-	if (size <=  64 * 1024 * 1024) return 26;
 	BUG();
 
 	/* Will never be reached. Needed because the compiler may complain */
-- 
2.25.1