linux-kernel - Re: [PATCH v2] ath10k: sdio: remove redundant check in for loop

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Message-ID: <87h7rnnnrb.fsf@codeaurora.org>
Date:   Thu, 24 Sep 2020 19:27:36 +0300
From:   Kalle Valo <kvalo@...eaurora.org>
To:     Julian Calaby <julian.calaby@...il.com>
Cc:     Alex Dewar <alex.dewar90@...il.com>, netdev@...r.kernel.org,
        linux-wireless@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>, ath10k@...ts.infradead.org,
        Jakub Kicinski <kuba@...nel.org>,
        Saeed Mahameed <saeedm@...dia.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH v2] ath10k: sdio: remove redundant check in for loop

Julian Calaby <julian.calaby@...il.com> writes:

> On Thu, Sep 17, 2020 at 3:09 AM Alex Dewar <alex.dewar90@...il.com> wrote:
>>
>> The for loop checks whether cur_section is NULL on every iteration, but
>> we know it can never be NULL as there is another check towards the
>> bottom of the loop body. Refactor to avoid this unnecessary check.
>>
>> Also, increment the variable i inline for clarity
>
> Comments below.
>
>> Addresses-Coverity: 1496984 ("Null pointer dereferences)
>> Suggested-by: Saeed Mahameed <saeedm@...dia.com>
>> Signed-off-by: Alex Dewar <alex.dewar90@...il.com>
>> ---
>> v2: refactor in the manner suggested by Saeed
>>
>>  drivers/net/wireless/ath/ath10k/sdio.c | 12 +++---------
>>  1 file changed, 3 insertions(+), 9 deletions(-)
>>
>> diff --git a/drivers/net/wireless/ath/ath10k/sdio.c b/drivers/net/wireless/ath/ath10k/sdio.c
>> index 81ddaafb6721..486886c74e6a 100644
>> --- a/drivers/net/wireless/ath/ath10k/sdio.c
>> +++ b/drivers/net/wireless/ath/ath10k/sdio.c
>> @@ -2307,8 +2307,8 @@ static int ath10k_sdio_dump_memory_section(struct ath10k *ar,
>>         }
>>
>>         count = 0;
>> -
>> -       for (i = 0; cur_section; i++) {
>> +       i = 0;
>> +       for (; cur_section; cur_section = next_section) {
>
> You can have multiple statements in each section of a for() if you need to, e.g.
>
> for (i = 1; cur_section; cur_section = next_section, i++) {
>
> which means that the increment of i isn't hidden deep in the function body.

Yeah, I was thinking the same. But I'll apply this patch anyway, it's
still an improvement.

> That said, this function is a mess. Something (approximately) like
> this might be more readable:
>
> prev_end = memregion->start;
> for (i = 0; i < mem_region->section_table.size; i++) {
>     cur_section = &mem_region->section_table.sections[i];
>
>     // fail if prev_end is greater than cur_section->start - message
> from line 2329 and 2294
>     // check section size - from line 2315
>
>     skip_size = cur_section->start - prev_end;
>
>     // check buffer size - from line 2339 - needs to account for the
> skip size too.
>     // fill in the skip size amount - from line 2358 and 2304
>     // ath10k_sdio_read_mem - from line 2346
>
>     prev_end = cur_section->end;
> }

I agree. Anyone can come up with a patch?

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