Re: [PATCH 01/61] Coccinelle: Prefer IS_ERR_OR_NULL over manual NULL check

[Krzysztof Kozlowski]

On 10/03/2026 12:48, Philipp Hahn wrote:
> Find and convert uses of IS_ERR() plus NULL check to IS_ERR_OR_NULL().
> 
> There are several cases where `!ptr && WARN_ON[_ONCE](IS_ERR(ptr))` is
> used:
> - arch/x86/kernel/callthunks.c:215 WARN_ON_ONCE
> - drivers/clk/clk.c:4561 WARN_ON_ONCE
> - drivers/interconnect/core.c:793 WARN_ON
> - drivers/reset/core.c:718 WARN_ON
> The change is not 100% semantical equivalent as the warning will now
> also happen when the pointer is NULL.
> 
> To: Julia Lawall <Julia.Lawall@xxxxxxxx>
> To: Nicolas Palix <nicolas.palix@xxxxxxx>
> Cc: cocci@xxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> 
> ---
> drivers/clocksource/mips-gic-timer.c:283 looks suspicious: ret != clk,
> but Daniel Lezcano verified it as cottect.
> 
> There are some cases where the checks are part of a larger expression:
> - mm/kmemleak.c:1095
> - mm/kmemleak.c:1155
> - mm/kmemleak.c:1173
> - mm/kmemleak.c:1290
> - mm/kmemleak.c:1328
> - mm/kmemleak.c:1241
> - mm/kmemleak.c:1310
> - mm/kmemleak.c:1258
> - net/netlink/af_netlink.c:2670
> Thanks to Julia Lawall for the help to also handle them.
> 
> Signed-off-by: Philipp Hahn <phahn-oss@xxxxxx>
> ---
>  scripts/coccinelle/api/is_err_or_null.cocci | 125 ++++++++++++++++++++++++++++
>  1 file changed, 125 insertions(+)
> 

Neither this, nor try from 2011, nor any future try should be accepted,
because it creates impression IS_ERR_OR_NULL is somehow okay. No, it is
not okay, it is a discouraged pattern leading to less readable and
maintainable code. We should not have therefore any tools suggesting
usage of IS_ERR_OR_NULL, because people will be converting poor code
into that, instead of fixing that poor code.

Best regards,
Krzysztof