linux-kernel - Re: [PATCH 1/1] mm/madvise: enhance lazyfreeing with mTHP in madvise

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Date: Mon, 26 Feb 2024 10:38:31 +0800
From: Yin Fengwei <fengwei.yin@...el.com>
To: Lance Yang <ioworker0@...il.com>, <akpm@...ux-foundation.org>
CC: <zokeefe@...gle.com>, <shy828301@...il.com>, <david@...hat.com>,
	<mhocko@...e.com>, <ryan.roberts@....com>, <wangkefeng.wang@...wei.com>,
	<songmuchun@...edance.com>, <peterx@...hat.com>, <minchan@...nel.org>,
	<linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1] mm/madvise: enhance lazyfreeing with mTHP in
 madvise_free



On 1/1/70 08:00,  wrote:
> diff --git a/mm/madvise.c b/mm/madvise.c
> index cfa5e7288261..bcbf56595a2e 100644
> --- a/mm/madvise.c
> +++ b/mm/madvise.c
> @@ -676,11 +676,43 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr,
>  		 */
>  		if (folio_test_large(folio)) {
>  			int err;
> +			unsigned long next_addr, align;
>  
> -			if (folio_estimated_sharers(folio) != 1)
> -				break;
> -			if (!folio_trylock(folio))
> -				break;
> +			if (folio_estimated_sharers(folio) != 1 ||
> +			    !folio_trylock(folio))
> +				goto skip_large_folio;
> +
> +			align = folio_nr_pages(folio) * PAGE_SIZE;
> +			next_addr = ALIGN_DOWN(addr + align, align);
There is a possible corner case:
If there is a cow folio associated with this folio and the cow folio
has smaller size than this folio for whatever reason, this change can't
handle it correctly.


Regards
Yin, Fengwei