linux-kernel - Re: [PATCHv3] perf: Fix vmalloc ring buffer free function

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Message-ID: <20130312170416.GD32001@krava.brq.redhat.com>
Date:	Tue, 12 Mar 2013 18:04:16 +0100
From:	Jiri Olsa <jolsa@...hat.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	linux-kernel@...r.kernel.org,
	Corey Ashford <cjashfor@...ux.vnet.ibm.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...e.hu>,
	Namhyung Kim <namhyung@...nel.org>,
	Paul Mackerras <paulus@...ba.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: Re: [PATCHv3] perf: Fix vmalloc ring buffer free function

On Tue, Mar 12, 2013 at 05:24:50PM +0100, Peter Zijlstra wrote:
> Right you are..
> 
> How about something like the below; using that 0 << -1 is still 0.

hum.. we are obviously not on the same page wrt 'confusing' ;-)

looks ok, I'll test it

jirka

> 
> ---
>  kernel/events/ring_buffer.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
> index 23cb34f..e72ca70 100644
> --- a/kernel/events/ring_buffer.c
> +++ b/kernel/events/ring_buffer.c
> @@ -316,7 +316,7 @@ void rb_free(struct ring_buffer *rb)
>  struct page *
>  perf_mmap_to_page(struct ring_buffer *rb, unsigned long pgoff)
>  {
> -	if (pgoff > (1UL << page_order(rb)))
> +	if (pgoff > (rb->nr_pages << page_order(rb)))
>  		return NULL;
>  
>  	return vmalloc_to_page((void *)rb->user_page + pgoff * PAGE_SIZE);
> @@ -336,10 +336,10 @@ static void rb_free_work(struct work_struct *work)
>  	int i, nr;
>  
>  	rb = container_of(work, struct ring_buffer, work);
> -	nr = 1 << page_order(rb);
> +	nr = rb->nr_pages << page_order(rb);
>  
>  	base = rb->user_page;
> -	for (i = 0; i < nr + 1; i++)
> +	for (i = 0; i <= nr; i++)
>  		perf_mmap_unmark_page(base + (i * PAGE_SIZE));
>  
>  	vfree(base);
> @@ -373,7 +373,7 @@ struct ring_buffer *rb_alloc(int nr_pages, long watermark, int cpu, int flags)
>  	rb->user_page = all_buf;
>  	rb->data_pages[0] = all_buf + PAGE_SIZE;
>  	rb->page_order = ilog2(nr_pages);
> -	rb->nr_pages = 1;
> +	rb->nr_pages = !!nr_pages;
>  
>  	ring_buffer_init(rb, watermark, flags);
>  
> 
> 
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