[PATCH] trace-cmd: support -m parameter for virt instances

[Marcelo Tosatti <mtosatti@xxxxxxxxxx>]

Take into consideration the value passed in with "-m",
the max size in kilobytes that a per cpu buffer should be,
when reading trace data from guests.

This allows one to prevent running out of diskspace on long runs.

Reported-by: Junyao Zhao <junzhao@xxxxxxxxxx>
Signed-off-by: Marcelo Tosatti <mtosatti@xxxxxxxxxx>

diff --git a/lib/trace-cmd/include/private/trace-cmd-private.h b/lib/trace-cmd/include/private/trace-cmd-private.h
index f2cf8dc8..2d14ed7a 100644
--- a/lib/trace-cmd/include/private/trace-cmd-private.h
+++ b/lib/trace-cmd/include/private/trace-cmd-private.h
@@ -370,7 +370,7 @@ enum {
 void tracecmd_free_recorder(struct tracecmd_recorder *recorder);
 struct tracecmd_recorder *tracecmd_create_recorder(const char *file, int cpu, unsigned flags);
 struct tracecmd_recorder *tracecmd_create_recorder_fd(int fd, int cpu, unsigned flags);
-struct tracecmd_recorder *tracecmd_create_recorder_virt(const char *file, int cpu, unsigned flags, int trace_fd);
+struct tracecmd_recorder *tracecmd_create_recorder_virt(const char *file, int cpu, unsigned flags, int trace_fd, int maxkb);
 struct tracecmd_recorder *tracecmd_create_recorder_maxkb(const char *file, int cpu, unsigned flags, int maxkb);
 struct tracecmd_recorder *tracecmd_create_buffer_recorder_fd(int fd, int cpu, unsigned flags, struct tracefs_instance *instance);
 struct tracecmd_recorder *tracecmd_create_buffer_recorder(const char *file, int cpu, unsigned flags, struct tracefs_instance *instance);
diff --git a/lib/trace-cmd/trace-recorder.c b/lib/trace-cmd/trace-recorder.c
index 0633edf5..44f245d5 100644
--- a/lib/trace-cmd/trace-recorder.c
+++ b/lib/trace-cmd/trace-recorder.c
@@ -175,19 +175,46 @@ tracecmd_create_buffer_recorder_fd(int fd, int cpu, unsigned flags, struct trace
 
 static struct tracecmd_recorder *
 __tracecmd_create_buffer_recorder(const char *file, int cpu, unsigned flags,
-				  struct tracefs_instance *instance, int tfd)
+				  struct tracefs_instance *instance, int tfd, int maxkb)
 {
 	struct tracecmd_recorder *recorder;
-	int fd;
+	int fd, fd2 = -1;
+	char *file2;
 
-	fd = open(file, O_WRONLY | O_CREAT | O_TRUNC | O_LARGEFILE, 0644);
+	fd = open(file, O_RDWR | O_CREAT | O_TRUNC | O_LARGEFILE, 0644);
 	if (fd < 0)
 		return NULL;
 
-	recorder = create_buffer_recorder_fd2(fd, -1, cpu, flags, instance, 0, tfd);
+	if (maxkb) {
+		int len = strlen(file);
+
+		file2 = malloc(len + 3);
+		if (!file2)
+			return NULL;
+
+		sprintf(file2, "%s.1", file);
+
+		fd2 = open(file2, O_RDWR | O_CREAT | O_TRUNC | O_LARGEFILE, 0644);
+		if (fd2 < 0) {
+			close(fd);
+			unlink(file);
+			free(file2);
+			return NULL;
+		}
+	}
+
+	recorder = create_buffer_recorder_fd2(fd, fd2, cpu, flags, instance, maxkb, tfd);
 	if (!recorder) {
 		close(fd);
 		unlink(file);
+		if (fd2 != -1)
+			close(fd2);
+	}
+
+	if (fd2 != -1) {
+		/* Unlink file2, we need to add everything to file at the end */
+		unlink(file2);
+		free(file2);
 	}
 
 	return recorder;
@@ -242,7 +269,7 @@ struct tracecmd_recorder *
 tracecmd_create_buffer_recorder(const char *file, int cpu, unsigned flags,
 				struct tracefs_instance *instance)
 {
-	return __tracecmd_create_buffer_recorder(file, cpu, flags, instance, -1);
+	return __tracecmd_create_buffer_recorder(file, cpu, flags, instance, -1, 0);
 }
 
 /**
@@ -255,9 +282,9 @@ tracecmd_create_buffer_recorder(const char *file, int cpu, unsigned flags,
  */
 struct tracecmd_recorder *
 tracecmd_create_recorder_virt(const char *file, int cpu, unsigned flags,
-			      int trace_fd)
+			      int trace_fd, int maxkb)
 {
-	return __tracecmd_create_buffer_recorder(file, cpu, flags, NULL, trace_fd);
+	return __tracecmd_create_buffer_recorder(file, cpu, flags, NULL, trace_fd, maxkb);
 }
 
 struct tracecmd_recorder *tracecmd_create_recorder_fd(int fd, int cpu, unsigned flags)
diff --git a/tracecmd/trace-record.c b/tracecmd/trace-record.c
index 91cc90d4..69ea0cbd 100644
--- a/tracecmd/trace-record.c
+++ b/tracecmd/trace-record.c
@@ -3584,7 +3584,7 @@ create_recorder_instance(struct buffer_instance *instance, const char *file, int
 			flags |= TRACECMD_RECORD_NOBRASS;
 		else if (!trace_vsock_can_splice_read())
 			flags |= TRACECMD_RECORD_NOSPLICE;
-		return tracecmd_create_recorder_virt(file, cpu, flags, fd);
+		return tracecmd_create_recorder_virt(file, cpu, flags, fd, max_kb);
 	}
 
 	if (brass)