Tracing fixes for 6.9:

- Fix the buffer_percent accounting as it is dependent on three variables:
   1) pages_read - number of subbuffers read
   2) pages_lost - number of subbuffers lost due to overwrite
   3) pages_touched - number of pages that a writer entered
   These three counters only increment, and to know how many active pages
   there are on the buffer at any given time, the pages_read and
   pages_lost are subtracted from pages_touched. But the pages touched
   was incremented whenever any writer went to the next subbuffer even
   if it wasn't the only one, so it was incremented more than it should
   be causing the counter for how many subbuffers currently have content
   incorrect, which caused the buffer_percent that holds waiters until
   the ring buffer is filled to a given percentage to wake up early.
 
 - Fix warning of unused functions when PERF_EVENTS is not configured in
 
 - Replace bad tab with space in Kconfig for FTRACE_RECORD_RECURSION_SIZE
 
 - Fix to some kerneldoc function comments in eventfs code.
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Merge tag 'trace-v6.9-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace

Pull tracing fixes from Steven Rostedt:

 - Fix the buffer_percent accounting as it is dependent on three
   variables:

     1) pages_read - number of subbuffers read
     2) pages_lost - number of subbuffers lost due to overwrite
     3) pages_touched - number of pages that a writer entered

   These three counters only increment, and to know how many active
   pages there are on the buffer at any given time, the pages_read and
   pages_lost are subtracted from pages_touched.

   But the pages touched was incremented whenever any writer went to the
   next subbuffer even if it wasn't the only one, so it was incremented
   more than it should be causing the counter for how many subbuffers
   currently have content incorrect, which caused the buffer_percent
   that holds waiters until the ring buffer is filled to a given
   percentage to wake up early.

 - Fix warning of unused functions when PERF_EVENTS is not configured in

 - Replace bad tab with space in Kconfig for FTRACE_RECORD_RECURSION_SIZE

 - Fix to some kerneldoc function comments in eventfs code.

* tag 'trace-v6.9-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ring-buffer: Only update pages_touched when a new page is touched
  tracing: hide unused ftrace_event_id_fops
  tracing: Fix FTRACE_RECORD_RECURSION_SIZE Kconfig entry
  eventfs: Fix kernel-doc comments to functions

fs/tracefs/event_inode.c

@@ -336,6 +336,7 @@ static void update_inode_attr(struct dentry *dentry, struct inode *inode,
 
 /**
  * lookup_file - look up a file in the tracefs filesystem
+ * @parent_ei: Pointer to the eventfs_inode that represents parent of the file
  * @dentry: the dentry to look up
  * @mode: the permission that the file should have.
  * @attr: saved attributes changed by user
@@ -389,6 +390,7 @@ static struct dentry *lookup_file(struct eventfs_inode *parent_ei,
 /**
  * lookup_dir_entry - look up a dir in the tracefs filesystem
  * @dentry: the directory to look up
+ * @pei: Pointer to the parent eventfs_inode if available
  * @ei: the eventfs_inode that represents the directory to create
  *
  * This function will look up a dentry for a directory represented by
@@ -478,16 +480,20 @@ void eventfs_d_release(struct dentry *dentry)
 
 /**
  * lookup_file_dentry - create a dentry for a file of an eventfs_inode
+ * @dentry: The parent dentry under which the new file's dentry will be created
  * @ei: the eventfs_inode that the file will be created under
  * @idx: the index into the entry_attrs[] of the @ei
- * @parent: The parent dentry of the created file.
- * @name: The name of the file to create
  * @mode: The mode of the file.
  * @data: The data to use to set the inode of the file with on open()
  * @fops: The fops of the file to be created.
  *
- * Create a dentry for a file of an eventfs_inode @ei and place it into the
- * address located at @e_dentry.
+ * This function creates a dentry for a file associated with an
+ * eventfs_inode @ei. It uses the entry attributes specified by @idx,
+ * if available. The file will have the specified @mode and its inode will be
+ * set up with @data upon open. The file operations will be set to @fops.
+ *
+ * Return: Returns a pointer to the newly created file's dentry or an error
+ * pointer.
  */
 static struct dentry *
 lookup_file_dentry(struct dentry *dentry,

kernel/trace/Kconfig

@@ -965,7 +965,7 @@ config FTRACE_RECORD_RECURSION
 
 config FTRACE_RECORD_RECURSION_SIZE
 	int "Max number of recursed functions to record"
-	default	128
+	default 128
 	depends on FTRACE_RECORD_RECURSION
 	help
 	  This defines the limit of number of functions that can be

kernel/trace/ring_buffer.c

@@ -1393,7 +1393,6 @@ static void rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer,
 	old_write = local_add_return(RB_WRITE_INTCNT, &next_page->write);
 	old_entries = local_add_return(RB_WRITE_INTCNT, &next_page->entries);
 
-	local_inc(&cpu_buffer->pages_touched);
 	/*
 	 * Just make sure we have seen our old_write and synchronize
 	 * with any interrupts that come in.
@@ -1430,8 +1429,9 @@ static void rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer,
 		 */
 		local_set(&next_page->page->commit, 0);
 
-		/* Again, either we update tail_page or an interrupt does */
-		(void)cmpxchg(&cpu_buffer->tail_page, tail_page, next_page);
+		/* Either we update tail_page or an interrupt does */
+		if (try_cmpxchg(&cpu_buffer->tail_page, &tail_page, next_page))
+			local_inc(&cpu_buffer->pages_touched);
 	}
 }
 

kernel/trace/trace_events.c

@@ -1670,6 +1670,7 @@ static int trace_format_open(struct inode *inode, struct file *file)
 	return 0;
 }
 
+#ifdef CONFIG_PERF_EVENTS
 static ssize_t
 event_id_read(struct file *filp, char __user *ubuf, size_t cnt, loff_t *ppos)
 {
@@ -1684,6 +1685,7 @@ event_id_read(struct file *filp, char __user *ubuf, size_t cnt, loff_t *ppos)
 
 	return simple_read_from_buffer(ubuf, cnt, ppos, buf, len);
 }
+#endif
 
 static ssize_t
 event_filter_read(struct file *filp, char __user *ubuf, size_t cnt,
@@ -2152,10 +2154,12 @@ static const struct file_operations ftrace_event_format_fops = {
 	.release = seq_release,
 };
 
+#ifdef CONFIG_PERF_EVENTS
 static const struct file_operations ftrace_event_id_fops = {
 	.read = event_id_read,
 	.llseek = default_llseek,
 };
+#endif
 
 static const struct file_operations ftrace_event_filter_fops = {
 	.open = tracing_open_file_tr,