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SubjectRe: [PATCH v3] kvmalloc: always use vmalloc if CONFIG_DEBUG_SG
On Mon 23-04-18 20:06:16, Mikulas Patocka wrote:
[...]
> @@ -404,6 +405,12 @@ void *kvmalloc_node(size_t size, gfp_t f
> */
> WARN_ON_ONCE((flags & GFP_KERNEL) != GFP_KERNEL);
>
> +#ifdef CONFIG_DEBUG_SG
> + /* Catch bugs when the caller uses DMA API on the result of kvmalloc. */
> + if (!(prandom_u32_max(2) & 1))
> + goto do_vmalloc;
> +#endif

I really do not think there is anything DEBUG_SG specific here. Why you
simply do not follow should_failslab path or even reuse the function?

> +
> /*
> * We want to attempt a large physically contiguous block first because
> * it is less likely to fragment multiple larger blocks and therefore
> @@ -427,6 +434,9 @@ void *kvmalloc_node(size_t size, gfp_t f
> if (ret || size <= PAGE_SIZE)
> return ret;
>
> +#ifdef CONFIG_DEBUG_SG
> +do_vmalloc:
> +#endif
> return __vmalloc_node_flags_caller(size, node, flags,
> __builtin_return_address(0));
> }

--
Michal Hocko
SUSE Labs

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