Re: [PATCH v18 04/18] trace-cmd: Add new library APIs for ftrace instances.

[Tzvetomir Stoyanov <tz.stoyanov@gmail.com>]

On Sat, Dec 21, 2019 at 5:03 AM Steven Rostedt <rostedt@goodmis.org> wrote:
>
> On Fri, 13 Dec 2019 17:30:15 +0200
> "Tzvetomir Stoyanov (VMware)" <tz.stoyanov@gmail.com> wrote:
>
> > +/**
> > + * tracecmd_get_instance_file - return the path to a instance file
> > + * @instance: buffer instance for the file, can be NULL for the top instance
> > + * @file: name of file to return
> > + *
> > + * Returns the path name of the @file for the given @instance
> > + *
> > + * Must use tracecmd_put_tracing_file() to free the returned string
> > + */
> > +char *
> > +tracecmd_get_instance_file(struct tracecmd_instance *instance, const char *file)
> > +{
> > +     char *path;
> > +     char *buf;
> > +     int ret;
> > +
> > +     if (instance && instance->name) {
> > +             ret = asprintf(&buf, "instances/%s/%s", instance->name, file);
> > +             if (ret < 0)
> > +                     die("Failed to allocate name for %s/%s", instance->name, file);
> > +             path = tracecmd_get_tracing_file(buf);
> > +             free(buf);
> > +     } else
> > +             path = tracecmd_get_tracing_file(file);
> > +
> > +     return path;
> > +}
> > +
> > +/**
> > + * tracecmd_get_instance_file - return the path to a instance file
> > + * @instance: buffer instance for the file, can be NULL for the top instance
> > + * @file: name of file to return
> > + *
> > + * Returns the path name of the @file for the given @instance
> > + *
> > + * Must use tracecmd_put_tracing_file() to free the returned string
>
> The above is a cut and paste of tracecmd_get_instance_file, not of the
> instance_dir.
>
> > + */
> > +char *tracecmd_get_instance_dir(struct tracecmd_instance *instance)
> > +{
> > +     char *buf;
> > +     char *path;
> > +     int ret;
> > +
> > +     if (instance->name) {
> > +             ret = asprintf(&buf, "instances/%s", instance->name);
> > +             if (ret < 0)
> > +                     die("Failed to allocate for instance %s", instance->name);
> > +             path = tracecmd_get_tracing_file(buf);
> > +             free(buf);
> > +     } else
> > +             path = tracecmd_find_tracing_dir();
> > +
> > +     return path;
> > +}
> > +
> > +/**
> > + * tracecmd_write_instance_file - Write in trace file of specific instance
> > + * @instance: buffer instance for the file, can be NULL for the top instance
> > + * @file: name of the file
> > + * @str: Nul terminated string, that will be written in the file
> > + * @type: Nul terminated string, describing the current write operation
> > + *     Used for logging purposes
> > + *
> > + * Returns the number of written bytes, or -1 in case of an error
> > + */
> > +int tracecmd_write_instance_file(struct tracecmd_instance *instance,
> > +                              const char *file, const char *str,
> > +                              const char *type)
>
> I think we should get rid of the type and move the logic that needs it
> to the callers.
>
>
> > +{
> > +     struct stat st;
> > +     char *path;
> > +     int ret;
> > +
> > +     path = tracecmd_get_instance_file(instance, file);
> > +     ret = stat(path, &st);
> > +     if (ret == 0)
> > +             ret = tracecmd_write_file(path, str, type);
> > +     tracecmd_put_tracing_file(path);
> > +
> > +     return ret;
> > +}
> > +
>
> [..]
>
> > +/*
> > + * tracecmd_write_file - Write in trace file
> > + * @file: Full name of the trace file.
> > + * @str: Null terminated string, that will be written in the file.
> > + * @type: Null terminated string, describing the current write operation.
> > + *     Used for logging purposes.
> > + *
> > + * Returns the number of written bytes, or -1 in case of an error
> > + */
> > +int tracecmd_write_file(const char *file, const char *str, const char *type)
> > +{
> > +     char buf[BUFSIZ];
> > +     int ret;
> > +     int fd;
> > +
> > +     fd = open(file, O_WRONLY | O_TRUNC);
> > +     if (fd < 0)
> > +             die("opening to '%s'", file);
> > +     ret = write(fd, str, strlen(str));
> > +     close(fd);
> > +     if (ret < 0 && type) {
> > +             /* write failed */
> > +             fd = open(file, O_RDONLY);
> > +             if (fd < 0)
> > +                     die("writing to '%s'", file);
> > +             /* the filter has the error */
> > +             while ((ret = read(fd, buf, BUFSIZ)) > 0)
> > +                     fprintf(stderr, "%.*s", ret, buf);
> > +             die("Failed %s of %s\n", type, file);
>
> Yeah, the above needs to be moved to the upper layers. It even has a
> comment about "the filter has the error". That's reference to the
> filter file of trace events, which is the only file that really does
> that.
>
> -- Steve
>

These new instance APIs are going to be part of the new libtracefs,
I'll remove this patch
from the series, when the libtracefs code is merged.

> > +             close(fd);
> > +     }
> > +     return ret;
> > +}
> >



-- 
Tzvetomir (Ceco) Stoyanov
VMware Open Source Technology Center