Messages in this thread Patch in this message | | | Date | Tue, 19 Nov 2013 21:39:23 -0700 | From | David Ahern <> | Subject | Re: [PATCH] perf record: Delete file if a failure occurs writing the perf data file |
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On 11/12/13, 8:34 AM, Peter Zijlstra wrote: > On Tue, Nov 12, 2013 at 08:25:02AM -0700, David Ahern wrote: >> The patch in this thread deletes the file. Another option is to rewind the >> file to the last known good write (ie., length after last successful call to >> write_output). > > I'd report a warning and continue with all events that you could read > upto that point. >
Coming back to this: the answer to that statement is known. The attached patch attempt to rewind to the last good write. Subsequent reads to the file fail with:
WARNING: The /tmp/mnt/perf.data file's data size field is 0 which is unexpected. Was the 'perf record' command properly terminated? reading input file (size expected=3 received=-1)broken or missing trace data incompatible file format (rerun with -v to learn more)
Given that it would seem deleting the file is the best option.
David diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c index 65615a8bc25e..309f590cf267 100644 --- a/tools/perf/builtin-record.c +++ b/tools/perf/builtin-record.c @@ -99,7 +99,22 @@ static int do_write_output(struct perf_record *rec, void *buf, size_t size) static int write_output(struct perf_record *rec, void *buf, size_t size) { - return do_write_output(rec, buf, size); + off_t len; + int rc; + + /* save current length */ + len = rec->session->header.data_offset + rec->bytes_written; + + rc = do_write_output(rec, buf, size); + + /* on failure reset file to last known good length */ + if (rc < 0) { + pr_debug("truncating file to last known good write: len %ld\n", len); + if (ftruncate(rec->file.fd, len) != 0) + pr_err("Double failure -- write failed and then ftruncate\n"); + } + + return rc; } static int process_synthesized_event(struct perf_tool *tool, | |