Re: [PATCH 2/3] drm/i915/gem: split shared memory allocation table logic

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] Unreachable WARN_ON_ONCE and error return in `shmem_shrink_get_folio`.
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commit fe135bc87bdc96f8bc699495fde11dd752239633
Author: Krzysztof Karas <krzysztof.karas@intel.com>

drm/i915/gem: split shared memory allocation table logic

This commit factors out the scatterlist allocation logic in
shmem_sg_alloc_table into smaller helper functions. It introduces
shmem_shrink_get_folio and validate_size, while changing the main loop
structure to improve readability.

> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
> index 06543ae60706e..b5ae7e5f80a06 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
[ ... ]
> +static struct folio *shmem_shrink_get_folio(struct address_space *mapping,
> +					    unsigned long folio_index,
> +					    gfp_t gfp, unsigned int pages_left,
> +					    struct drm_i915_private *i915)
> +{
> +#define MAX_READS 2
> +	struct folio *folio;
> +	unsigned int i;
> +
> +	for (i = 0; i < MAX_READS; i++) {
> +		cond_resched();
> +		folio = shmem_read_folio_gfp(mapping, folio_index, gfp);
> +		if (!IS_ERR(folio) || i == MAX_READS - 1)
> +			return folio;
[ ... ]
> +		gfp |= __GFP_RETRY_MAYFAIL | __GFP_NOWARN;
> +	}
> +
> +	/* Should never happen */
> +	WARN_ON_ONCE(1);
> +	return ERR_PTR(-EINVAL);
> +}

[Severity: Low]
Is this code unreachable?

Looking at the loop termination logic above, the for loop will either exit
early when !IS_ERR(folio) is true, or it will return directly on the final
iteration when i == MAX_READS - 1. Because it always returns from within the
loop body, it never falls through to the end of the function.

Does this WARN_ON_ONCE and error return serve an intended purpose, or can it
be safely removed as dead code?

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Sashiko AI review · https://sashiko.dev/#/patchset/20260625134342.1102921-1-krzysztof.karas@intel.com?part=2