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SubjectRe: [PATCH V5 02/17] perf mmap: fix: recalculate size for overwrite mode.
Em Thu, Jan 18, 2018 at 01:26:17PM -0800, kan.liang@intel.com escreveu:
> From: Kan Liang <kan.liang@intel.com>
>
> In perf_mmap__push(), the 'size' need to be recalculated, otherwise the
> invalid data might be pushed to the record in overwrite mode.
>
> The issue is introduced by commit 7fb4b407a124 ("perf mmap: Don't
> discard prev in backward mode").

In these cases, please add the Fixes tag, like:

Fixes: 7fb4b407a124 ("perf mmap: Don't discard prev in backward mode")

I'm doing it this time.

Thanks,

- Arnaldo

> When the ringbuffer is full in overwrite mode, backward_rb_find_range
> will be called to recalculate the 'start' and 'end'. The 'size' needs to
> be recalculated accordingly.
>
> Unconditionally recalculate the 'size', not just for full ringbuffer in
> overwrite mode. Because,
> - There is no harmful to recalculate the 'size' for other cases.
> - The code of calculating 'start' and 'end' will be factored out later.
> The new function does not need to return 'size'.
>
> Signed-off-by: Kan Liang <kan.liang@intel.com>
> ---
> tools/perf/util/mmap.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/tools/perf/util/mmap.c b/tools/perf/util/mmap.c
> index 05076e6..97cf4fa 100644
> --- a/tools/perf/util/mmap.c
> +++ b/tools/perf/util/mmap.c
> @@ -302,6 +302,8 @@ int perf_mmap__push(struct perf_mmap *md, bool overwrite,
> return -1;
> }
>
> + size = end - start;
> +
> if ((start & md->mask) + size != (end & md->mask)) {
> buf = &data[start & md->mask];
> size = md->mask + 1 - (start & md->mask);
> --
> 2.5.5

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