Re: [PATCH] err.h: use __always_inline on all error pointer helpers

[Alexander Lobakin]

From: Arnd Bergmann <arnd@xxxxxxxxxx>
Date: Tue, 26 May 2026 12:18:41 +0200

> From: Arnd Bergmann <arnd@xxxxxxxx>
> 
> While testing randconfig builds on s390, I came across a
> link failure with CONFIG_DMA_SHARED_BUFFER disabled:
> 
> ERROR: modpost: "dma_buf_put" [drivers/iommu/iommufd/iommufd.ko] undefined!
> 
> The problem here is that IS_ERR() is not inlined and dead code elimination
> fails as a consequence.
> 
> The err.h helpers all turn into a trivial assignment ot a bit mask

                                                       ^^
                                                       or

(nit)

> and should never result in a function call, so force them to always be
> inline. This should generally result in better object code aside from
> avoiding the link failure above.

bloat-o-meter would be nice to see but optional, it's obvious to me that
these helpers should always get inlined.

Not sure why compilers sometimes decide to uninline a couple
instructions (feels like there's sorta dumb logic "oh it's used more
than X times -- uninline no matter what").

> 
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
Reviewed-by: Alexander Lobakin <aleksander.lobakin@xxxxxxxxx>

Thanks,
Olek