Re: [Intel-wired-lan] [PATCH 1/5] ethtool: use vmalloc_array() to simplify code

[Qianfeng Rong]

在 2025/8/13 0:34, Paul Menzel 写道:
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>
> Dear Qianfeng,
>
>
> Thank you for your patch.
>
> Am 12.08.25 um 15:32 schrieb Qianfeng Rong:
> > Remove array_size() calls and replace vmalloc() with vmalloc_array() to
> > simplify the code and maintain consistency with existing kmalloc_array()
> > usage.
>
> You could build it without and with your patch and look if the assembler
> code changes.

Very good point, the following experiment was done:
//before apply patch:
objdump -dSl --prefix-addresses fm10k_ethtool.o > original.dis

//after apply patch:
objdump -dSl --prefix-addresses fm10k_ethtool.o > patched.dis

diff -u original.dis patched.dis | diffstat
patched.dis | 1578 ... 1 file changed, 785 insertions(+), 793 deletions(-)

From the above results, we can see that the assembly instructions are
reduced after applying the patch.


#define array_size(a, b)    size_mul(a, b)

static inline size_t __must_check size_mul(size_t factor1, size_t factor2)
{
    size_t bytes;

    if (check_mul_overflow(factor1, factor2, &bytes))
        return SIZE_MAX;

    return bytes;
}

void *__vmalloc_array_noprof(size_t n, size_t size, gfp_t flags)
{
    size_t bytes;

    if (unlikely(check_mul_overflow(n, size, &bytes)))
        return NULL;
    return __vmalloc_noprof(bytes, flags);
}

And from the code, array_size() will return SIZE_MAX after detecting
overflow.  SIZE_MAX is passed to vmalloc for available memory
verification before exiting and returning NULL. vmalloc_array()
will directly return NULL after detecting overflow.

Best regards,
Qianfeng
> Reviewed-by: Paul Menzel <pmenzel@xxxxxxxxxxxxx>
>
>
> Kind regards,
>
> Paul