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From:   Michael Ellerman <mpe@ellerman.id.au>
To:     Peter Xu <peterx@redhat.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Cc:     Peter Xu <peterx@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Gerald Schaefer <gerald.schaefer@de.ibm.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Will Deacon <will@kernel.org>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH 16/26] mm/powerpc: Use general page fault accounting
In-Reply-To: <20200626223622.199765-1-peterx@redhat.com>
References: <20200626223130.199227-1-peterx@redhat.com> <20200626223622.199765-1-peterx@redhat.com>
Date:   Fri, 03 Jul 2020 21:08:15 +1000
Message-ID: <875zb47t5s.fsf@mpe.ellerman.id.au>
MIME-Version: 1.0
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Sender: linux-kernel-owner@vger.kernel.org
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Peter Xu <peterx@redhat.com> writes:
> Use the general page fault accounting by passing regs into handle_mm_fault().
>
> CC: Michael Ellerman <mpe@ellerman.id.au>
> CC: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> CC: Paul Mackerras <paulus@samba.org>
> CC: linuxppc-dev@lists.ozlabs.org
> Signed-off-by: Peter Xu <peterx@redhat.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@ellerman.id.au>

cheers