Re: [PATCH] mm: Do not keep page locked during page fault whilecharging it for memcg

[Christoph Hellwig]

> +
> +			/* We have to drop the page lock here because memcg
> +			 * charging might block for unbound time if memcg oom
> +			 * killer is disabled.
> +			 */
> +			unlock_page(vmf.page);
> +			ret = mem_cgroup_newpage_charge(page, mm, GFP_KERNEL);
> +			lock_page(vmf.page);

This introduces a completely poinless unlock/lock cycle for non-memcg
pagefaults.  Please make sure it only happens when actually needed.

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