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Subject[PATCH] percpu: Use struct_size() helper
One of the more common cases of allocation size calculations is finding
the size of a structure that has a zero-sized array at the end, along
with memory for some number of elements for that array. For example:

struct pcpu_alloc_info {
...
struct pcpu_group_info groups[];
};

Make use of the struct_size() helper instead of an open-coded version
in order to avoid any potential type mistakes.

So, replace the following form:

sizeof(*ai) + nr_groups * sizeof(ai->groups[0])

with:

struct_size(ai, groups, nr_groups)

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
---
mm/percpu.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/percpu.c b/mm/percpu.c
index 7e2aa0305c27..7e06a1e58720 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -2125,7 +2125,7 @@ struct pcpu_alloc_info * __init pcpu_alloc_alloc_info(int nr_groups,
void *ptr;
int unit;

- base_size = ALIGN(sizeof(*ai) + nr_groups * sizeof(ai->groups[0]),
+ base_size = ALIGN(struct_size(ai, groups, nr_groups),
__alignof__(ai->groups[0].cpu_map[0]));
ai_size = base_size + nr_units * sizeof(ai->groups[0].cpu_map[0]);

--
2.23.0
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