Re: [PATCH 1/2] trace-cmd: Implemented new API tracecmd_add_option_v()

[Steven Rostedt <rostedt@goodmis.org>]

On Mon, 17 Jun 2019 14:52:17 +0300
tz.stoyanov@gmail.com wrote:

> From: "Tzvetomir Stoyanov (VMware)" <tz.stoyanov@gmail.com>
> 
> From: Tzvetomir Stoyanov <tstoyanov@vmware.com>
> 
> This patch implements a new tracecmd API, tracecmd_add_option_v()
> It adds new option in trace.dat, similar to tracecmd_add_option(),
> but the option's data is passed as list of buffers. The standard
> struct iovec is used as input parameter, containing the option's
> data buffers.
> 
> Signed-off-by: Tzvetomir Stoyanov <tstoyanov@vmware.com>
> ---
>  include/trace-cmd/trace-cmd.h    |   5 ++
>  include/traceevent/event-parse.h |   1 +
>  tracecmd/trace-output.c          | 117 ++++++++++++++++++++++++++-----
>  3 files changed, 106 insertions(+), 17 deletions(-)
> 
> diff --git a/include/trace-cmd/trace-cmd.h b/include/trace-cmd/trace-cmd.h
> index ceb03f4..3919673 100644
> --- a/include/trace-cmd/trace-cmd.h
> +++ b/include/trace-cmd/trace-cmd.h
> @@ -245,11 +245,16 @@ struct tracecmd_output *tracecmd_create_init_file_override(const char *output_fi
>  struct tracecmd_option *tracecmd_add_option(struct tracecmd_output *handle,
>  					    unsigned short id, int size,
>  					    const void *data);
> +struct tracecmd_option *
> +tracecmd_add_option_v(struct tracecmd_output *handle,
> +		    unsigned short id, const struct iovec *vector, int count);
> +
>  struct tracecmd_option *tracecmd_add_buffer_option(struct tracecmd_output *handle,
>  						   const char *name, int cpus);
>  
>  int tracecmd_write_cpus(struct tracecmd_output *handle, int cpus);
>  int tracecmd_write_options(struct tracecmd_output *handle);
> +int tracecmd_append_options(struct tracecmd_output *handle);

The change log doesn't mention anything about tracecmd_append_options()?

>  int tracecmd_update_option(struct tracecmd_output *handle,
>  			   struct tracecmd_option *option, int size,
>  			   const void *data);
> diff --git a/include/traceevent/event-parse.h b/include/traceevent/event-parse.h
> index 5e0fd19..62057b3 100644
> --- a/include/traceevent/event-parse.h
> +++ b/include/traceevent/event-parse.h
> @@ -11,6 +11,7 @@
>  #include <stdio.h>
>  #include <regex.h>
>  #include <string.h>
> +#include <sys/uio.h>
>  
>  #include "trace-seq.h"
>  
> diff --git a/tracecmd/trace-output.c b/tracecmd/trace-output.c
> index 33d6ce3..f7a2791 100644
> --- a/tracecmd/trace-output.c
> +++ b/tracecmd/trace-output.c
> @@ -883,21 +883,23 @@ static struct tracecmd_output *create_file(const char *output_file,
>  }
>  
>  /**
> - * tracecmd_add_option - add options to the file
> + * tracecmd_add_option_v - add options to the file
>   * @handle: the output file handle name
>   * @id: the id of the option
> - * @size: the size of the option data
> - * @data: the data to write to the file.
> + * @vector: array of vectors, pointing to the data to write in the file
> + * @count: number of items in the vector array
>   *
>   * Returns handle to update option if needed.
>   *  Just the content can be updated, with smaller or equal to
>   *  content than the specified size.
>   */
>  struct tracecmd_option *
> -tracecmd_add_option(struct tracecmd_output *handle,
> -		    unsigned short id, int size, const void *data)
> +tracecmd_add_option_v(struct tracecmd_output *handle,
> +		    unsigned short id, const struct iovec *vector, int count)

Hmm, I think this is a bit overkill. I don't really see anything using
more than one or two data vectors. All I see would be at most a "count"
followed by a list of data, which is what I think you are using this
for.

I rather wait to implement something like this when there's more of a
need for it. I don't believe this change really requires it.

-- Steve


>  {
>  	struct tracecmd_option *option;
> +	char *data = NULL;
> +	int i, size = 0;
>  
>  	/*
>  	 * We can only add options before they were written.
> @@ -906,32 +908,63 @@ tracecmd_add_option(struct tracecmd_output *handle,
>  	if (handle->options_written)
>  		return NULL;
>  
> -	handle->nr_options++;
> +	for (i = 0; i < count; i++)
> +		size += vector[i].iov_len;
> +
> +	/* Some IDs (like TRACECMD_OPTION_TRACECLOCK) pass vector with 0 / NULL data */
> +	if (size) {
> +		data = malloc(size);
> +		if (!data) {
> +			warning("Insufficient memory");
> +			return NULL;
> +		}
> +	}
>  
>  	option = malloc(sizeof(*option));
>  	if (!option) {
>  		warning("Could not allocate space for option");
> +		free(data);
>  		return NULL;
>  	}
>  
> -	option->id = id;
> -	option->size = size;
> -	option->data = malloc(size);
> -	if (!option->data) {
> -		warning("Insufficient memory");
> -		free(option);
> -		return NULL;
> +	handle->nr_options++;
> +	option->data = data;
> +	for (i = 0; i < count; i++) {
> +		if (vector[i].iov_base && vector[i].iov_len) {
> +			memcpy(data, vector[i].iov_base, vector[i].iov_len);
> +			data += vector[i].iov_len;
> +		}
>  	}
> -
> -	/* Some IDs (like TRACECMD_OPTION_TRACECLOCK) pass 0 / NULL data */
> -	if (size)
> -		memcpy(option->data, data, size);
> +	option->size = size;
> +	option->id = id;
>  
>  	list_add_tail(&option->list, &handle->options);
>  
>  	return option;
>  }
>  
> +/**
> + * tracecmd_add_option - add options to the file
> + * @handle: the output file handle name
> + * @id: the id of the option
> + * @size: the size of the option data
> + * @data: the data to write to the file.
> + *
> + * Returns handle to update option if needed.
> + *  Just the content can be updated, with smaller or equal to
> + *  content than the specified size.
> + */
> +struct tracecmd_option *
> +tracecmd_add_option(struct tracecmd_output *handle,
> +		    unsigned short id, int size, const void *data)
> +{
> +	struct iovec vect;
> +
> +	vect.iov_base = (void *) data;
> +	vect.iov_len = size;
> +	return tracecmd_add_option_v(handle, id, &vect, 1);
> +}
> +
>  int tracecmd_write_cpus(struct tracecmd_output *handle, int cpus)
>  {
>  	cpus = convert_endian_4(handle, cpus);
> @@ -979,6 +1012,56 @@ int tracecmd_write_options(struct tracecmd_output *handle)
>  	return 0;
>  }
>  
> +int tracecmd_append_options(struct tracecmd_output *handle)
> +{
> +	struct tracecmd_option *options;
> +	unsigned short option;
> +	unsigned short endian2;
> +	unsigned int endian4;
> +	off_t offset;
> +	int r;
> +
> +	/* If already written, ignore */
> +	if (handle->options_written)
> +		return 0;
> +
> +	if (lseek64(handle->fd, 0, SEEK_END) == (off_t)-1)
> +		return -1;
> +	offset = lseek64(handle->fd, -2, SEEK_CUR);
> +	if (offset == (off_t)-1)
> +		return -1;
> +
> +	r = pread(handle->fd, &option, 2, offset);
> +	if (r != 2 || option != TRACECMD_OPTION_DONE)
> +		return -1;
> +
> +	list_for_each_entry(options, &handle->options, list) {
> +		endian2 = convert_endian_2(handle, options->id);
> +		if (do_write_check(handle, &endian2, 2))
> +			return -1;
> +
> +		endian4 = convert_endian_4(handle, options->size);
> +		if (do_write_check(handle, &endian4, 4))
> +			return -1;
> +
> +		/* Save the data location in case it needs to be updated */
> +		options->offset = lseek64(handle->fd, 0, SEEK_CUR);
> +
> +		if (do_write_check(handle, options->data,
> +				   options->size))
> +			return -1;
> +	}
> +
> +	option = TRACECMD_OPTION_DONE;
> +
> +	if (do_write_check(handle, &option, 2))
> +		return -1;
> +
> +	handle->options_written = 1;
> +
> +	return 0;
> +}
> +
>  int tracecmd_update_option(struct tracecmd_output *handle,
>  			   struct tracecmd_option *option, int size,
>  			   const void *data)