linux-kernel - [PATCH] mm/sparse.c: Wrong allocation for mem

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Date:   Fri, 22 Dec 2017 16:48:18 +0800
From:   Baoquan He <bhe@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     Baoquan He <bhe@...hat.com>, Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andy Lutomirski <luto@...capital.net>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Atsushi Kumagai <ats-kumagai@...jp.nec.com>, linux-mm@...ck.org
Subject: [PATCH] mm/sparse.c: Wrong allocation for mem_section

In commit

  83e3c48729 "mm/sparsemem: Allocate mem_section at runtime for CONFIG_SPARSEMEM_EXTREME=y"

mem_section is allocated at runtime to save memory. While it allocates
the first dimension of array with sizeof(struct mem_section). It costs 
extra memory, should be sizeof(struct mem_section*).

Fix it.

Signed-off-by: Baoquan He <bhe@...hat.com>
Tested-by: Dave Young <dyoung@...hat.com>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Andy Lutomirski <luto@...capital.net>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Atsushi Kumagai <ats-kumagai@...jp.nec.com>
Cc: linux-mm@...ck.org

---
 mm/sparse.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/sparse.c b/mm/sparse.c
index 7a5dacaa06e3..2609aba121e8 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -211,7 +211,7 @@ void __init memory_present(int nid, unsigned long start, unsigned long end)
 	if (unlikely(!mem_section)) {
 		unsigned long size, align;
 
-		size = sizeof(struct mem_section) * NR_SECTION_ROOTS;
+		size = sizeof(struct mem_section*) * NR_SECTION_ROOTS;
 		align = 1 << (INTERNODE_CACHE_SHIFT);
 		mem_section = memblock_virt_alloc(size, align);
 	}
-- 
2.5.5