linux-kernel - [PATCH] kmalloc_index optimization(add kmalloc max size check)

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Date:   Fri, 17 Apr 2020 00:09:35 -0700
From:   Bernard Zhao <bernard@...o.com>
To:     Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Cc:     kernel@...o.com, Bernard Zhao <bernard@...o.com>
Subject: [PATCH] kmalloc_index optimization(add kmalloc max size check)

kmalloc size should never exceed KMALLOC_MAX_SIZE.
kmalloc_index realise if size is exceed KMALLOC_MAX_SIZE, e.g 64M,
kmalloc_index just return index 26, but never check with OS`s max
kmalloc config KMALLOC_MAX_SIZE. This index`s kmalloc caches maybe
not create in function create_kmalloc_caches.
We can throw an warninginfo in kmalloc at the beginning, instead of
being guaranteed by the buddy alloc behind.

Signed-off-by: Bernard Zhao <bernard@...o.com>
---
 include/linux/slab.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/include/linux/slab.h b/include/linux/slab.h
index 6d45488..59b60d2 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -351,6 +351,10 @@ static __always_inline unsigned int kmalloc_index(size_t size)
 	if (!size)
 		return 0;
 
+	/* size should never exceed KMALLOC_MAX_SIZE. */
+	if (size > KMALLOC_MAX_SIZE)
+		WARN(1, "size exceed max kmalloc size!\n");
+
 	if (size <= KMALLOC_MIN_SIZE)
 		return KMALLOC_SHIFT_LOW;
 
-- 
2.7.4