[PATCH] trace-cmd: Write the actual size of compressed block in the trace file

["Tzvetomir Stoyanov (VMware)" <tz.stoyanov@gmail.com>]

Before a data block is compressed using the chosen compression
algorithm, a hook function is called to calculate the size of the
required buffer to compress the data. In most cases that size is bigger
than the actual size of the compressed data. The current logic writes
into the trace file that buffer with its calculated size, even though
part of it is not used. In the trace file should be written only the
compressed data block, with its real size.

fixes: 3f8447b1 ("trace-cmd library: Add support for compression algorithms")
Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com>
---
 lib/trace-cmd/trace-compress.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/lib/trace-cmd/trace-compress.c b/lib/trace-cmd/trace-compress.c
index aa03d17c..a63295e6 100644
--- a/lib/trace-cmd/trace-compress.c
+++ b/lib/trace-cmd/trace-compress.c
@@ -303,7 +303,7 @@ error:
  */
 int tracecmd_compress_block(struct tracecmd_compression *handle)
 {
-	unsigned int size;
+	unsigned int size, real_size;
 	char *buf;
 	int endian4;
 	int ret;
@@ -318,12 +318,14 @@ int tracecmd_compress_block(struct tracecmd_compression *handle)
 	if (!buf)
 		return -1;
 
-	ret = handle->proto->compress_block(handle->context, handle->buffer, handle->pointer, buf, size);
-	if (ret < 0)
+	real_size = handle->proto->compress_block(handle->context, handle->buffer, handle->pointer, buf, size);
+	if (real_size < 0) {
+		ret = real_size;
 		goto out;
+	}
 
 	/* Write compressed data size */
-	endian4 = tep_read_number(handle->tep, &ret, 4);
+	endian4 = tep_read_number(handle->tep, &real_size, 4);
 	ret = do_write(handle, &endian4, 4);
 	if (ret != 4)
 		goto out;
@@ -337,8 +339,8 @@ int tracecmd_compress_block(struct tracecmd_compression *handle)
 	}
 
 	/* Write compressed data */
-	ret = do_write(handle, buf, size);
-	if (ret != size) {
+	ret = do_write(handle, buf, real_size);
+	if (ret != real_size) {
 		ret = -1;
 		goto out;
 	}
-- 
2.35.1