Re: [PATCH] trace-cmd: Try alternate path for message cache

[Steven Rostedt <rostedt@goodmis.org>]

On Sun, 3 Apr 2022 15:24:33 +0000
Joel Fernandes <joel@joelfernandes.org> wrote:

> Something like the following seems to work, and the file grows to only 4KB.
> Note with memfd, the file name does not have to be unique and the fd entry
> in the process denotes the file's uniqueness.
> 
> I'll roll it into a patch, let me know if you disagree:

I'm OK with this, but I would really like a "Reviewed-by" from Tzvetomir.

Go ahead and send a real patch.

Thanks,

-- Steve

> 
> ---8<---
> 
> diff --git a/lib/trace-cmd/include/private/trace-cmd-private.h b/lib/trace-cmd/include/private/trace-cmd-private.h
> index 6934376..3aee139 100644
> --- a/lib/trace-cmd/include/private/trace-cmd-private.h
> +++ b/lib/trace-cmd/include/private/trace-cmd-private.h
> @@ -377,7 +377,6 @@ enum tracecmd_msg_flags {
>  };
>  
>  /* for both client and server */
> -#define MSG_CACHE_FILE "/tmp/trace_msg_cacheXXXXXX"
>  struct tracecmd_msg_handle {
>  	int			fd;
>  	short			cpu_count;
> @@ -386,7 +385,6 @@ struct tracecmd_msg_handle {
>  	bool			done;
>  	bool			cache;
>  	int			cfd;
> -	char			cfile[sizeof(MSG_CACHE_FILE)];
>  };
>  
>  struct tracecmd_tsync_protos {
> diff --git a/lib/trace-cmd/trace-msg.c b/lib/trace-cmd/trace-msg.c
> index 03b853e..1472f20 100644
> --- a/lib/trace-cmd/trace-msg.c
> +++ b/lib/trace-cmd/trace-msg.c
> @@ -593,11 +593,9 @@ tracecmd_msg_handle_alloc(int fd, unsigned long flags)
>  int tracecmd_msg_handle_cache(struct tracecmd_msg_handle *msg_handle)
>  {
>  	if (msg_handle->cfd < 0) {
> -		strcpy(msg_handle->cfile, MSG_CACHE_FILE);
> -		msg_handle->cfd = mkstemp(msg_handle->cfile);
> +		msg_handle->cfd = memfd_create("trace_msg_cache", 0);
>  		if (msg_handle->cfd < 0)
>  			return -1;
> -		unlink(msg_handle->cfile);
>  	}
>  	msg_handle->cache = true;
>  	return 0;