trace-cmd: Add tracecmd_refresh_record()

The data field in a struct record is a pointer to an mmap
section of memory. If other records are read, this mmap section
can be unmapped. The tracecmd_refresh_record() allows users to remap
that mmapped section for the record.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

2 files changed, 22 insertions, 0 deletions

diff --git a/trace-cmd.h b/trace-cmd.h
index a5cc217..f6141f4 100644
--- a/trace-cmd.h
+++ b/trace-cmd.h
@@ -72,6 +72,8 @@ struct record *
 tracecmd_read_cpu_first(struct tracecmd_input *handle, int cpu);
 struct record *
 tracecmd_read_cpu_last(struct tracecmd_input *handle, int cpu);
+int tracecmd_refresh_record(struct tracecmd_input *handle,
+                            struct record *record);
 
 int tracecmd_set_cpu_to_timestamp(struct tracecmd_input *handle,
                                   int cpu, unsigned long long ts);
diff --git a/trace-input.c b/trace-input.c
index 1657b2a..826fed9 100644
--- a/trace-input.c
+++ b/trace-input.c
@@ -815,6 +815,26 @@ tracecmd_read_at(struct tracecmd_input *handle, unsigned long long offset,
 }
 
 /**
+ * tracecmd_refresh_record - remaps the records data
+ * @handle: input handle for the trace.dat file
+ * @record: the record to be refreshed
+ *
+ * A record data points to a mmap section of memory.
+ * by reading new records the mmap section may be unmapped.
+ * This will refresh the record's data mapping.
+ */
+int tracecmd_refresh_record(struct tracecmd_input *handle,
+                            struct record *record)
+{
+        unsigned long long page_offset;
+
+        page_offset = record->offset & ~(handle->page_size - 1);
+        get_page(handle, record->cpu, page_offset);
+
+        return 0;
+}
+
+/**
  * tracecmd_read_cpu_first - get the first record in a CPU
  * @handle: input handle for the trace.dat file
  * @cpu: the CPU to search