linux-kernel - Re: [PATCH v1] perf session: fix loading of compressed data split across adjacent records

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Date:   Sun, 14 Jul 2019 17:49:32 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Alexey Budankov <alexey.budankov@...ux.intel.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Andi Kleen <ak@...ux.intel.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1] perf session: fix loading of compressed data split
 across adjacent records

On Tue, Jul 09, 2019 at 05:48:14PM +0300, Alexey Budankov wrote:

SNIP

>  	decomp->file_pos = file_offset;
> +	decomp->mmap_len = mmap_len;
>  	decomp->head = 0;
>  
> -	if (decomp_last) {
> -		decomp_last_rem = decomp_last->size - decomp_last->head;
> +	if (decomp_last_rem) {
>  		memcpy(decomp->data, &(decomp_last->data[decomp_last->head]), decomp_last_rem);
>  		decomp->size = decomp_last_rem;
>  	}
> @@ -61,7 +67,7 @@ static int perf_session__process_compressed_event(struct perf_session *session,
>  	decomp_size = zstd_decompress_stream(&(session->zstd_data), src, src_size,
>  				&(decomp->data[decomp_last_rem]), decomp_len - decomp_last_rem);
>  	if (!decomp_size) {
> -		munmap(decomp, sizeof(struct decomp) + decomp_len);
> +		munmap(decomp, mmap_len);
>  		pr_err("Couldn't decompress data\n");
>  		return -1;
>  	}
> @@ -255,15 +261,15 @@ static void perf_session__delete_threads(struct perf_session *session)
>  static void perf_session__release_decomp_events(struct perf_session *session)
>  {
>  	struct decomp *next, *decomp;
> -	size_t decomp_len;
> +	size_t mmap_len;
>  	next = session->decomp;
> -	decomp_len = session->header.env.comp_mmap_len;
>  	do {
>  		decomp = next;
>  		if (decomp == NULL)
>  			break;
>  		next = decomp->next;
> -		munmap(decomp, decomp_len + sizeof(struct decomp));
> +		mmap_len = decomp->mmap_len;
> +		munmap(decomp, mmap_len);

what's the need for extra mmap_len variable in here?
could you just use decomp->mmap_len directly?

otherwise it lookgs good to me

thanks,
jirka