Re: [PATCH core] perf data: Adding error message if perf_data__create_dir fails

[Bayduraev, Alexey V]

On 21.02.2022 1:43, Jiri Olsa wrote:
> On Fri, Feb 18, 2022 at 06:23:40PM +0300, Alexey Bayduraev wrote:
>> There is no notification about data directory creation failure. Add it.
>>
>> Signed-off-by: Alexey Bayduraev <alexey.v.bayduraev@xxxxxxxxxxxxxxx>
>> ---
>>  tools/perf/builtin-record.c | 4 +++-
>>  1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
>> index 0bc6529814b2..0306d5911de2 100644
>> --- a/tools/perf/builtin-record.c
>> +++ b/tools/perf/builtin-record.c
>> @@ -1186,8 +1186,10 @@ static int record__mmap_evlist(struct record *rec,
>>  
>>  	if (record__threads_enabled(rec)) {
>>  		ret = perf_data__create_dir(&rec->data, evlist->core.nr_mmaps);
>> -		if (ret)
>> +		if (ret) {
>> +			pr_err("Failed to create data directory: %s\n", strerror(errno));
> 
> errno will be misleading in here, because perf_data__create_dir
> calls other syscalls on error path

Mostly I want to output something like:

  Failed to create data dir: Too many open files

This will trigger the user to increase the open files limit.
Would it be better to place such message to perf_data__create_dir after 
open() syscall?

Regards,
Alexey

> 
> jirka
> 
>>  			return ret;
>> +		}
>>  		for (i = 0; i < evlist->core.nr_mmaps; i++) {
>>  			if (evlist->mmap)
>>  				evlist->mmap[i].file = &rec->data.dir.files[i];
>> -- 
>> 2.19.0
>>