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SubjectRe: [PATCH 2/2] tracing: Do not copy hash if O_TRUNC is set
On Wed, 11 Jun 2014 17:06:54 +0900
Namhyung Kim <namhyung@kernel.org> wrote:

> When a filter file is open for writing and O_TRUNC is set, there's no
> need to copy and free the filter entries.
>

Nice cleanup. I'll add it for 3.17.

Thanks,

-- Steve

> Signed-off-by: Namhyung Kim <namhyung@kernel.org>
> ---
> kernel/trace/ftrace.c | 12 +++++++-----
> 1 file changed, 7 insertions(+), 5 deletions(-)
>
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index ddfda763ded7..13885590a184 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -2759,7 +2759,13 @@ ftrace_regex_open(struct ftrace_ops *ops, int flag,
> hash = ops->filter_hash;
>
> if (file->f_mode & FMODE_WRITE) {
> - iter->hash = alloc_and_copy_ftrace_hash(FTRACE_HASH_DEFAULT_BITS, hash);
> + const int size_bits = FTRACE_HASH_DEFAULT_BITS;
> +
> + if (file->f_flags & O_TRUNC)
> + iter->hash = alloc_ftrace_hash(size_bits);
> + else
> + iter->hash = alloc_and_copy_ftrace_hash(size_bits, hash);
> +
> if (!iter->hash) {
> trace_parser_put(&iter->parser);
> kfree(iter);
> @@ -2768,10 +2774,6 @@ ftrace_regex_open(struct ftrace_ops *ops, int flag,
> }
> }
>
> - if ((file->f_mode & FMODE_WRITE) &&
> - (file->f_flags & O_TRUNC))
> - ftrace_filter_reset(iter->hash);
> -
> if (file->f_mode & FMODE_READ) {
> iter->pg = ftrace_pages_start;
>



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