linux-kernel - Re: [PATCH] mm/madvise: don't forget to leave lazy MMU mode in madvise_cold_or_pageout_pte

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Date: Thu, 25 Jan 2024 22:53:36 -0800
From: Andrew Morton <akpm@...ux-foundation.org>
To: Sergey Senozhatsky <senozhatsky@...omium.org>
Cc: Jiexun Wang <wangjiexun@...ylab.org>, linux-kernel@...r.kernel.org,
 linux-mm@...ck.org
Subject: Re: [PATCH] mm/madvise: don't forget to leave lazy MMU mode in
 madvise_cold_or_pageout_pte_range()

On Fri, 26 Jan 2024 12:25:48 +0900 Sergey Senozhatsky <senozhatsky@...omium.org> wrote:

> We need to leave lazy MMU mode before unlocking.

What might be the userspace-visible effects of this?

> Fixes: b2f557a21bc8 ("mm/madvise: add cond_resched() in madvise_cold_or_pageout_pte_range()"
> Signed-off-by: Sergey Senozhatsky <senozhatsky@...omium.org>

I'll add a cc:stable.

> --- a/mm/madvise.c
> +++ b/mm/madvise.c
> @@ -451,6 +451,7 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd,
>  		if (++batch_count == SWAP_CLUSTER_MAX) {
>  			batch_count = 0;
>  			if (need_resched()) {
> +				arch_leave_lazy_mmu_mode();
>  				pte_unmap_unlock(start_pte, ptl);
>  				cond_resched();
>  				goto restart;