linux-kernel - Re: [PATCH] perf: Remove setting of page->index and ->mapping

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Message-ID: <20240810221507.GI11646@noisy.programming.kicks-ass.net>
Date: Sun, 11 Aug 2024 00:15:07 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: "Matthew Wilcox (Oracle)" <willy@...radead.org>
Cc: Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf: Remove setting of page->index and ->mapping

On Fri, Aug 09, 2024 at 09:10:36PM +0100, Matthew Wilcox (Oracle) wrote:
> I have no idea why perf is setting these fields.  There should be
> no need to do this.

Because these are not shared pages and nobody will ever look at these
fields? Yeah, I can't for the life of me remember why I did that.

> Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
> ---
>  kernel/events/core.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index aa3450bdc227..f55ab04f3df0 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -6221,8 +6221,6 @@ static vm_fault_t perf_mmap_fault(struct vm_fault *vmf)
>  		goto unlock;
>  
>  	get_page(vmf->page);
> -	vmf->page->mapping = vmf->vma->vm_file->f_mapping;
> -	vmf->page->index   = vmf->pgoff;
>  
>  	ret = 0;
>  unlock:
> -- 
> 2.43.0
>