linux-kernel - Re: [PATCH 3/4] mm/memory: convert do_shared

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Message-ID: <ZKNaVJCDH7ac8SCu@casper.infradead.org>
Date:   Tue, 4 Jul 2023 00:31:32 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Sidhartha Kumar <sidhartha.kumar@...cle.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        akpm@...ux-foundation.org
Subject: Re: [PATCH 3/4] mm/memory: convert do_shared_fault() to folios

On Sun, Jul 02, 2023 at 10:58:49PM -0700, Sidhartha Kumar wrote:
> Saves three implicit calls to compound_head().
> 
> Signed-off-by: Sidhartha Kumar <sidhartha.kumar@...cle.com>
> ---
>  mm/memory.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/mm/memory.c b/mm/memory.c
> index 93480e846ace6..33bf13431974c 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -4594,6 +4594,7 @@ static vm_fault_t do_shared_fault(struct vm_fault *vmf)
>  {
>  	struct vm_area_struct *vma = vmf->vma;
>  	vm_fault_t ret, tmp;
> +	struct folio *folio = page_folio(vmf->page);

You can't call page_folio() until after __do_fault().  Did you test this
series?

>  	ret = __do_fault(vmf);
>  	if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)))