linux-kernel - Re: [PATCH 16/26] mm/powerpc: Use general page fault accounting

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Date:   Fri, 03 Jul 2020 21:08:15 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Peter Xu <peterx@...hat.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Cc:     Peter Xu <peterx@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Gerald Schaefer <gerald.schaefer@...ibm.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Will Deacon <will@...nel.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH 16/26] mm/powerpc: Use general page fault accounting

Peter Xu <peterx@...hat.com> writes:
> Use the general page fault accounting by passing regs into handle_mm_fault().
>
> CC: Michael Ellerman <mpe@...erman.id.au>
> CC: Benjamin Herrenschmidt <benh@...nel.crashing.org>
> CC: Paul Mackerras <paulus@...ba.org>
> CC: linuxppc-dev@...ts.ozlabs.org
> Signed-off-by: Peter Xu <peterx@...hat.com>
> ---
>  arch/powerpc/mm/fault.c | 11 +++--------
>  1 file changed, 3 insertions(+), 8 deletions(-)
>
> diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
> index 992b10c3761c..e325d13efaf5 100644
> --- a/arch/powerpc/mm/fault.c
> +++ b/arch/powerpc/mm/fault.c
> @@ -563,7 +563,7 @@ static int __do_page_fault(struct pt_regs *regs, unsigned long address,
>  	 * make sure we exit gracefully rather than endlessly redo
>  	 * the fault.
>  	 */
> -	fault = handle_mm_fault(vma, address, flags, NULL);
> +	fault = handle_mm_fault(vma, address, flags, regs);
>  
>  #ifdef CONFIG_PPC_MEM_KEYS
>  	/*
> @@ -604,14 +604,9 @@ static int __do_page_fault(struct pt_regs *regs, unsigned long address,
>  	/*
>  	 * Major/minor page fault accounting.
>  	 */
> -	if (major) {
> -		current->maj_flt++;
> -		perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, address);
> +	if (major)
>  		cmo_account_page_fault();
> -	} else {
> -		current->min_flt++;
> -		perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, address);
> -	}
> +
>  	return 0;
>  }
>  NOKPROBE_SYMBOL(__do_page_fault);


You do change the logic a bit if regs is NULL (in mm_account_fault()),
but regs can never be NULL in this path, so it looks OK to me.

Acked-by: Michael Ellerman <mpe@...erman.id.au>

cheers