X-Git-Url: http://git.cascardo.info/?a=blobdiff_plain;f=kernel%2Frelay.c;h=d797502140b9a0f1ceb36f5ccbb4b9c66382a44e;hb=d52bd54db8be8999df6df5a776f38c4f8b5e9cea;hp=04d7cf3ef8cf932e036c7c76f6a27cefa962efc0;hpb=44d624622e57ad60e652da4d7bde43aadab350bf;p=cascardo%2Flinux.git

diff --git a/kernel/relay.c b/kernel/relay.c
index 04d7cf3ef8cf..d797502140b9 100644
--- a/kernel/relay.c
+++ b/kernel/relay.c
@@ -451,6 +451,13 @@ static struct rchan_buf *relay_open_buf(struct rchan *chan, unsigned int cpu)
 		if (!dentry)
 			goto free_buf;
 		relay_set_buf_dentry(buf, dentry);
+	} else {
+		/* Only retrieve global info, nothing more, nothing less */
+		dentry = chan->cb->create_buf_file(NULL, NULL,
+						   S_IRUSR, buf,
+						   &chan->is_global);
+		if (WARN_ON(dentry))
+			goto free_buf;
 	}
 
  	buf->cpu = cpu;
@@ -562,6 +569,10 @@ static int relay_hotcpu_callback(struct notifier_block *nb,
  *	attributes specified.  The created channel buffer files
  *	will be named base_filename0...base_filenameN-1.  File
  *	permissions will be %S_IRUSR.
+ *
+ *	If opening a buffer (@parent = NULL) that you later wish to register
+ *	in a filesystem, call relay_late_setup_files() once the @parent dentry
+ *	is available.
  */
 struct rchan *relay_open(const char *base_filename,
 			 struct dentry *parent,
@@ -640,8 +651,12 @@ static void __relay_set_buf_dentry(void *info)
  *
  *	Returns 0 if successful, non-zero otherwise.
  *
- *	Use to setup files for a previously buffer-only channel.
- *	Useful to do early tracing in kernel, before VFS is up, for example.
+ *	Use to setup files for a previously buffer-only channel created
+ *	by relay_open() with a NULL parent dentry.
+ *
+ *	For example, this is useful for perfomring early tracing in kernel,
+ *	before VFS is up and then exposing the early results once the dentry
+ *	is available.
  */
 int relay_late_setup_files(struct rchan *chan,
 			   const char *base_filename,
@@ -666,6 +681,20 @@ int relay_late_setup_files(struct rchan *chan,
 	}
 	chan->has_base_filename = 1;
 	chan->parent = parent;
+
+	if (chan->is_global) {
+		err = -EINVAL;
+		if (!WARN_ON_ONCE(!chan->buf[0])) {
+			dentry = relay_create_buf_file(chan, chan->buf[0], 0);
+			if (dentry && !WARN_ON_ONCE(!chan->is_global)) {
+				relay_set_buf_dentry(chan->buf[0], dentry);
+				err = 0;
+			}
+		}
+		mutex_unlock(&relay_channels_mutex);
+		return err;
+	}
+
 	curr_cpu = get_cpu();
 	/*
 	 * The CPU hotplug notifier ran before us and created buffers with
@@ -706,6 +735,7 @@ int relay_late_setup_files(struct rchan *chan,
 
 	return err;
 }
+EXPORT_SYMBOL_GPL(relay_late_setup_files);
 
 /**
  *	relay_switch_subbuf - switch to a new sub-buffer