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SubjectRe: [PATCH] block: bio: use struct_size() in kmalloc()
Date
Looks good.

Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>

On 5/17/19 2:17 AM, xiaolinkui wrote:
> 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 foo {
> int stuff;
> struct boo entry[];
> };
>
> instance = kmalloc(sizeof(struct foo) + count * sizeof(struct boo), GFP_KERNEL);
>
> Instead of leaving these open-coded and prone to type mistakes, we can
> now use the new struct_size() helper:
>
> instance = kmalloc(struct_size(instance, entry, count), GFP_KERNEL);
>
> Signed-off-by: xiaolinkui <xiaolinkui@kylinos.cn>
> ---
> block/bio.c | 7 ++-----
> 1 file changed, 2 insertions(+), 5 deletions(-)
>
> diff --git a/block/bio.c b/block/bio.c
> index 683cbb4..847ac60 100644
> --- a/block/bio.c
> +++ b/block/bio.c
> @@ -436,9 +436,7 @@ struct bio *bio_alloc_bioset(gfp_t gfp_mask, unsigned int nr_iovecs,
> if (nr_iovecs > UIO_MAXIOV)
> return NULL;
>
> - p = kmalloc(sizeof(struct bio) +
> - nr_iovecs * sizeof(struct bio_vec),
> - gfp_mask);
> + p = kmalloc(struct_size(bio, bi_io_vec, nr_iovecs), gfp_mask);
> front_pad = 0;
> inline_vecs = nr_iovecs;
> } else {
> @@ -1120,8 +1118,7 @@ static struct bio_map_data *bio_alloc_map_data(struct iov_iter *data,
> if (data->nr_segs > UIO_MAXIOV)
> return NULL;
>
> - bmd = kmalloc(sizeof(struct bio_map_data) +
> - sizeof(struct iovec) * data->nr_segs, gfp_mask);
> + bmd = kmalloc(struct_size(bmd, iov, data->nr_segs), gfp_mask);
> if (!bmd)
> return NULL;
> memcpy(bmd->iov, data->iov, sizeof(struct iovec) * data->nr_segs);



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