linux-kernel - Re: [Cocci] [PATCH] coccinelle: api: add kvfree script

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Message-ID: <43cead50-05f8-67ce-c1de-ce3acefb0dec@linux.com>
Date:   Sat, 6 Jun 2020 00:15:03 +0300
From:   Denis Efremov <efremov@...ux.com>
To:     Julia Lawall <julia.lawall@...ia.fr>
Cc:     cocci@...teme.lip6.fr, linux-kernel@...r.kernel.org
Subject: Re: [Cocci] [PATCH] coccinelle: api: add kvfree script

On 6/5/20 11:51 PM, Julia Lawall wrote:
> Is there a strong reason for putting the choice rule first?  It may make
> things somewhat slower than necessary, if it matches in many places,
> because the opportunity rule will have to detect that it doesn't care
> about all of those places.

No, I didn't know that order of rules matters. I just checked it, my PC
shows no difference in exec time if I swap these rules.

"choice" doesn't check the size. "opportunity" is more strict.
The motivation for adding 2 rules is that we could recommend to use
kvmalloc* only when there is a size condition. At the same time, we
should skip all if (...) {kmalloc()} else {vmalloc()},
res = kmalloc() if (!res) {vmalloc()} cases as false positives.

It seems that it's not possible to use subexpression rule
"expression size <= choice.E" in this case.

> Also, there is no need to exceed 80 characters here.  You can put a
> newline in the middle of a \( ... \)

Ok, I will fix it in v2 after all comments/suggestions.

Thanks,
Denis