Re: [PATCH v3 4/4] trace: create new directory for each trace dump

["Mattias Rönnblom" <hofors@lysator.liu.se>]

On 2022-10-25 11:00, David Marchand wrote:
> Rather than always overwrite the content of the trace directory, create
> new directories for each call to rte_trace_save().
> 
> In the unlikely event that multiple rte_trace_save() gets called many
> times in a single second, try to suffix the name with a digit.
> 
> Signed-off-by: David Marchand <david.marchand@redhat.com>
> ---
>   lib/eal/common/eal_common_trace.c       |  4 ++
>   lib/eal/common/eal_common_trace_utils.c | 89 +++++++++++--------------
>   lib/eal/common/eal_trace.h              |  1 +
>   3 files changed, 45 insertions(+), 49 deletions(-)
> 
> diff --git a/lib/eal/common/eal_common_trace.c b/lib/eal/common/eal_common_trace.c
> index bb26af618a..7d411b336e 100644
> --- a/lib/eal/common/eal_common_trace.c
> +++ b/lib/eal/common/eal_common_trace.c
> @@ -92,6 +92,10 @@ eal_trace_fini(void)
>   	trace_mem_free();
>   	trace_metadata_destroy();
>   	eal_trace_args_free();
> +	free(trace.rootdir);
> +	trace.rootdir = NULL;
> +	free(trace.dir);
> +	trace.dir = NULL;
>   }
>   
>   bool
> diff --git a/lib/eal/common/eal_common_trace_utils.c b/lib/eal/common/eal_common_trace_utils.c
> index 8561a0e198..6256ef6703 100644
> --- a/lib/eal/common/eal_common_trace_utils.c
> +++ b/lib/eal/common/eal_common_trace_utils.c
> @@ -87,9 +87,10 @@ trace_uuid_generate(void)
>   }
>   
>   static int
> -trace_session_name_generate(char **trace_dir)
> +trace_dir_name_generate(char **trace_dir)
>   {
>   	char date[sizeof("YYYY-mm-dd-AM-HH-MM-SS")];
> +	struct trace *trace = trace_obj_get();
>   	struct tm *tm_result;
>   	time_t tm;
>   
> @@ -106,7 +107,8 @@ trace_session_name_generate(char **trace_dir)
>   		goto fail;
>   	}
>   
> -	if (asprintf(trace_dir, "%s-%s", eal_get_hugefile_prefix(), date) == -1)
> +	if (asprintf(trace_dir, "%s/%s-%s", trace->rootdir,
> +			eal_get_hugefile_prefix(), date) == -1)
>   		goto fail;
>   
>   	return 0;
> @@ -115,21 +117,6 @@ trace_session_name_generate(char **trace_dir)
>   	return -1;
>   }
>   
> -static int
> -trace_dir_update(const char *str)
> -{
> -	struct trace *trace = trace_obj_get();
> -	char *dir;
> -	int rc;
> -
> -	rc = asprintf(&dir, "%s%s", trace->dir != NULL ? trace->dir : "", str);
> -	if (rc != -1) {
> -		free(trace->dir);
> -		trace->dir = dir;
> -	}
> -	return rc;
> -}
> -
>   int
>   eal_trace_args_save(const char *val)
>   {
> @@ -240,17 +227,16 @@ eal_trace_mode_args_save(const char *val)
>   int
>   eal_trace_dir_args_save(char const *val)
>   {
> -	char *dir_path;
> -	int rc;
> +	struct trace *trace = trace_obj_get();
>   
> -	if (asprintf(&dir_path, "%s/", val) == -1) {
> +	free(trace->rootdir);
> +	trace->rootdir = strdup(val);
> +	if (trace->rootdir == NULL) {
>   		trace_err("failed to copy directory: %s", strerror(errno));
>   		return -ENOMEM;
>   	}
>   
> -	rc = trace_dir_update(dir_path);
> -	free(dir_path);
> -	return rc;
> +	return 0;
>   }
>   
>   int
> @@ -293,7 +279,7 @@ trace_dir_default_path_get(char **dir_path)
>   	}
>   
>   	/* Append dpdk-traces to directory */
> -	if (asprintf(dir_path, "%s/dpdk-traces/", home_dir) == -1)
> +	if (asprintf(dir_path, "%s/dpdk-traces", home_dir) == -1)
>   		return -ENOMEM;
>   
>   	return 0;
> @@ -303,14 +289,11 @@ static int
>   trace_mkdir(void)
>   {
>   	struct trace *trace = trace_obj_get();
> -	static bool already_done;
> -	char *session;
> +	unsigned int try;
> +	char *trace_dir;
>   	int rc;
>   
> -	if (already_done)
> -		return 0;
> -
> -	if (trace->dir == NULL) {
> +	if (trace->rootdir == NULL) {
>   		char *dir_path;
>   
>   		rc = trace_dir_default_path_get(&dir_path);
> @@ -318,38 +301,46 @@ trace_mkdir(void)
>   			trace_err("fail to get default path");
>   			return rc;
>   		}
> -
> -		rc = trace_dir_update(dir_path);
> -		free(dir_path);
> -		if (rc < 0)
> -			return rc;
> +		trace->rootdir = dir_path;
>   	}
>   
>   	/* Create the path if it t exist, no "mkdir -p" available here */
> -	rc = mkdir(trace->dir, 0700);
> +	rc = mkdir(trace->rootdir, 0700);
>   	if (rc < 0 && errno != EEXIST) {
> -		trace_err("mkdir %s failed [%s]", trace->dir, strerror(errno));
> +		trace_err("mkdir %s failed [%s]", trace->rootdir, strerror(errno));
>   		rte_errno = errno;
>   		return -rte_errno;
>   	}
>   
> -	rc = trace_session_name_generate(&session);
> -	if (rc < 0)
> -		return rc;
> -	rc = trace_dir_update(session);
> -	free(session);
> +	rc = trace_dir_name_generate(&trace_dir);
>   	if (rc < 0)
>   		return rc;
> -
> -	rc = mkdir(trace->dir, 0700);
> -	if (rc < 0) {
> -		trace_err("mkdir %s failed [%s]", trace->dir, strerror(errno));
> -		rte_errno = errno;
> -		return -rte_errno;
> +	rc = mkdir(trace_dir, 0700);
> +	if (rc == 0)
> +		goto out;
> +
> +	/* 1000 tries are definitely enough :-) */

Do you need an upper bound at all?

Is there a point in retrying for anything other than EEXIST?

> +	for (try = 1; try < 1000; try++) {
> +		char *trace_dir_suffix;
> +
> +		if (asprintf(&trace_dir_suffix, "%s.%u", trace_dir, try) == -1)
> +			continue;
> +		rc = mkdir(trace_dir_suffix, 0700);
> +		if (rc == 0) {
> +			free(trace_dir);
> +			trace_dir = trace_dir_suffix;
> +			goto out;
> +		}
> +		free(trace_dir_suffix);
>   	}
>   
> +	trace_err("mkdir %s failed [%s]", trace->dir, strerror(errno));
> +	rte_errno = errno;
> +	return -rte_errno;
> +out:
> +	free(trace->dir);
> +	trace->dir = trace_dir;
>   	RTE_LOG(INFO, EAL, "Trace dir: %s\n", trace->dir);
> -	already_done = true;
>   	return 0;
>   }
>   
> diff --git a/lib/eal/common/eal_trace.h b/lib/eal/common/eal_trace.h
> index d66bcfe198..8991088253 100644
> --- a/lib/eal/common/eal_trace.h
> +++ b/lib/eal/common/eal_trace.h
> @@ -48,6 +48,7 @@ struct trace_arg {
>   };
>   
>   struct trace {
> +	char *rootdir;
>   	char *dir;
>   	int register_errno;
>   	uint32_t status;