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-rw-r--r--kernel/relay.c34
1 files changed, 32 insertions, 2 deletions
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