[Crash-utility] [PATCH] Update trace extension for per-cpu buffer size

[Dave Anderson]

----- Original Message -----
> Since Linux v3.4 (specifically, commit 438ced1720b584000 "ring-buffer:
> Add per_cpu ring buffer control files"), the trace buffer size is now
> per-cpu.  The patch below updates the trace extension to handle this.
> 
> Rabin

The patch looks good to me -- deferring to the trace.c maintainer 
Lai Jiangshan (cc'd directory) for his ACK.

Thanks,
  Dave

> 
> diff --git a/extensions/trace.c b/extensions/trace.c
> index 831cc77..224c662 100644
> --- a/extensions/trace.c
> +++ b/extensions/trace.c
> @@ -24,6 +24,7 @@ static int nr_cpu_ids;
>   * lockless ring_buffer and old non-lockless ring_buffer are both
>   supported.
>   */
>  static int lockless_ring_buffer;
> +static int per_cpu_buffer_sizes;
>  
>  #define koffset(struct, member) struct##_##member##_offset
>  
> @@ -37,6 +38,7 @@ static int koffset(ring_buffer, buffers);
>  
>  static int koffset(ring_buffer_per_cpu, cpu);
>  static int koffset(ring_buffer_per_cpu, pages);
> +static int koffset(ring_buffer_per_cpu, nr_pages);
>  static int koffset(ring_buffer_per_cpu, head_page);
>  static int koffset(ring_buffer_per_cpu, tail_page);
>  static int koffset(ring_buffer_per_cpu, commit_page);
> @@ -71,6 +73,7 @@ struct ring_buffer_per_cpu {
>  	ulong real_head_page;
>  
>  	int head_page_index;
> +	unsigned int nr_pages;
>  	ulong *pages;
>  
>  	ulong *linear_pages;
> @@ -144,7 +147,14 @@ static int init_offsets(void)
>  	init_offset(trace_array, buffer);
>  	init_offset(tracer, name);
>  
> -	init_offset(ring_buffer, pages);
> +	if (MEMBER_EXISTS("ring_buffer_per_cpu", "nr_pages")) {
> +		per_cpu_buffer_sizes = 1;
> +		if (verbose)
> +			fprintf(fp, "per cpu buffer sizes\n");
> +	}
> +
> +	if (!per_cpu_buffer_sizes)
> +		init_offset(ring_buffer, pages);
>  	init_offset(ring_buffer, flags);
>  	init_offset(ring_buffer, cpus);
>  	init_offset(ring_buffer, buffers);
> @@ -155,6 +165,8 @@ static int init_offsets(void)
>  			fprintf(fp, "lockless\n");
>  	}
>  
> +	if (per_cpu_buffer_sizes)
> +		init_offset(ring_buffer_per_cpu, nr_pages);
>  	init_offset(ring_buffer_per_cpu, cpu);
>  	init_offset(ring_buffer_per_cpu, pages);
>  	init_offset(ring_buffer_per_cpu, head_page);
> @@ -362,6 +374,10 @@ static int ftrace_init_buffers(struct
> ring_buffer_per_cpu *buffers,
>  		buffer_read_value(reader_page);
>  		buffer_read_value(overrun);
>  		buffer_read_value(entries);
> +		if (per_cpu_buffer_sizes) {
> +			buffer_read_value(nr_pages);
> +			pages = buffers[i].nr_pages;
> +		}
>  #undef buffer_read_value
>  
>  		if (ftrace_init_pages(buffers + i, pages) < 0)
> --
> 1.7.9.5
> 
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