linux-kernel - Re: [RFC PATCH v1 08/37] KVM: guest_memfd: Don't set FGP

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Message-ID: <b73fdd99-befe-4e2b-b029-909c4b31902b@suse.cz>
Date: Mon, 27 Oct 2025 14:39:20 +0100
From: Vlastimil Babka <vbabka@...e.cz>
To: Ackerley Tng <ackerleytng@...gle.com>, cgroups@...r.kernel.org,
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Subject: Re: [RFC PATCH v1 08/37] KVM: guest_memfd: Don't set FGP_ACCESSED
 when getting folios

On 10/17/25 22:11, Ackerley Tng wrote:
> guest_memfd folios don't care about accessed flags since the memory is
> unevictable and there is no storage to write back to, hence, cleanup the
> allocation path by not setting FGP_ACCESSED.
> 
> Signed-off-by: Ackerley Tng <ackerleytng@...gle.com>
> [sean: split to separate patch, write changelog]
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>

Acked-by: Vlastimil Babka <vbabka@...e.cz>

> ---
>  virt/kvm/guest_memfd.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
> index 855e682041311..2a9e9220a48aa 100644
> --- a/virt/kvm/guest_memfd.c
> +++ b/virt/kvm/guest_memfd.c
> @@ -167,14 +167,13 @@ static struct folio *kvm_gmem_get_folio(struct inode *inode, pgoff_t index)
>  	 * Fast-path: See if folio is already present in mapping to avoid
>  	 * policy_lookup.
>  	 */
> -	folio = __filemap_get_folio(inode->i_mapping, index,
> -				    FGP_LOCK | FGP_ACCESSED, 0);
> +	folio = filemap_lock_folio(inode->i_mapping, index);
>  	if (!IS_ERR(folio))
>  		return folio;
>  
>  	policy = kvm_gmem_get_folio_policy(GMEM_I(inode), index);
>  	folio = __filemap_get_folio_mpol(inode->i_mapping, index,
> -					 FGP_LOCK | FGP_ACCESSED | FGP_CREAT,
> +					 FGP_LOCK | FGP_CREAT,
>  					 mapping_gfp_mask(inode->i_mapping), policy);
>  	mpol_cond_put(policy);
>