trace-cmd library: Fix tracecmd_read_at()

Commit Message

Steven Rostedt March 17, 2022, 8:55 p.m. UTC

From: "Steven Rostedt (Google)" <[e-mail]>

The compression logic set all the file_offsets for the cpu_data to zero to
just use absolute offsets. But this breaks tracecmd_read_at() that has a
requirement that every record in a handle has a unique offset. This
includes records on different CPUs.

Make the file_offset unique and start at a new page boundary from the
previous cpu_data. Use next_offset in the input handle to keep track of
the last stored cpu_data and set the next cpu_data file_offset to it.

Also slightly restructure the input handle structure to be a little more
compact.

Fixes: 5113584096350 ("trace-cmd library: Initialize CPU data decompression logic")
Signed-off-by: Steven Rostedt (Google) <[e-mail]>
---
 lib/trace-cmd/trace-input.c | 22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

Patch

diff --git a/lib/trace-cmd/trace-input.c b/lib/trace-cmd/trace-input.c
index aa40d2451ab6..56410fb0c228 100644
--- a/lib/trace-cmd/trace-input.c
+++ b/lib/trace-cmd/trace-input.c
@@ -158,11 +158,12 @@  struct file_section {
 
 struct tracecmd_input {
 	struct tep_handle	*pevent;
-	unsigned long		file_state;
 	struct tep_plugin_list	*plugin_list;
 	struct tracecmd_input	*parent;
-	unsigned long		flags;
+	unsigned long		file_state;
 	unsigned long long	trace_id;
+	unsigned long long	next_offset;
+	unsigned long		flags;
 	int			fd;
 	int			long_size;
 	int			page_size;
@@ -1349,6 +1350,8 @@  static void *read_zpage(struct tracecmd_input *handle, int cpu, off64_t offset)
 	int pindex;
 	int size;
 
+	offset -= cpu_data->file_offset;
+
 	/* Look in the cache of already loaded chunks */
 	list_for_each_entry(cache, &cpu_data->compress.cache, list) {
 		if (CHUNK_CHECK_OFFSET(cache->chunk, offset)) {
@@ -2665,8 +2668,11 @@  static int init_cpu_zfile(struct tracecmd_input *handle, int cpu)
 	if (lseek64(handle->fd, offset, SEEK_SET) == (off_t)-1)
 		return -1;
 
-	cpu_data->offset = 0;
-	cpu_data->file_offset = 0;
+	cpu_data->file_offset = handle->next_offset;
+	handle->next_offset = (handle->next_offset + size + handle->page_size - 1) &
+		~(handle->page_size - 1);
+	cpu_data->offset = cpu_data->file_offset;
+
 	cpu_data->file_size = size;
 	cpu_data->size = size;
 	return 0;
@@ -2688,12 +2694,15 @@  static int init_cpu_zpage(struct tracecmd_input *handle, int cpu)
 	cpu_data->compress.count = count;
 	cpu_data->compress.last_chunk = 0;
 
-	cpu_data->file_offset = 0;
-	cpu_data->file_size = 0;
+	cpu_data->file_offset = handle->next_offset;
+
 	for (i = 0; i < count; i++)
 		cpu_data->file_size += cpu_data->compress.chunks[i].size;
+
 	cpu_data->offset = cpu_data->file_offset;
 	cpu_data->size = cpu_data->file_size;
+	handle->next_offset = (handle->next_offset + cpu_data->size + handle->page_size - 1) &
+		~(handle->page_size - 1);
 	return 0;
 }
 
@@ -4249,6 +4258,7 @@  struct tracecmd_input *tracecmd_alloc_fd(int fd, int flags)
 
 	read4(handle, &page_size);
 	handle->page_size = page_size;
+	handle->next_offset = page_size;
 
 	offset = lseek64(handle->fd, 0, SEEK_CUR);
 	handle->total_file_size = lseek64(handle->fd, 0, SEEK_END);