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Commit bf682c31 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Steven Rostedt
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tracing: Change remove_event_file_dir() to clear "d_subdirs"->i_private 

Change remove_event_file_dir() to clear ->i_private for every
file we are going to remove.

We need to check file->dir != NULL because event_create_dir()
can fail. debugfs_remove_recursive(NULL) is fine but the patch
moves it under the same check anyway for readability.

spin_lock(d_lock) and "d_inode != NULL" check are not needed
afaics, but I do not understand this code enough.

tracing_open_generic_file() and tracing_release_generic_file()
can go away, ftrace_enable_fops and ftrace_event_filter_fops()
use tracing_open_generic() but only to check tracing_disabled.

This fixes all races with event_remove() or instance_delete().
f_op->read/write/whatever can never use the freed file/call,
all event/* files were changed to check and use ->i_private
under event_mutex.

Note: this doesn't not fix other problems, event_remove() can
destroy the active ftrace_event_call, we need more changes but
those changes are completely orthogonal.

Link: http://lkml.kernel.org/r/20130728183527.GB16723@redhat.com



Reviewed-by: default avatarMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent f6a84bdc

kernel/trace/trace_events.c

+15 −32
Original line number Diff line number Diff line
@@ -428,39 +428,23 @@ static void *event_file_data(struct file *filp) 


static void remove_event_file_dir(struct ftrace_event_file *file)

{

	list_del(&file->list);

	debugfs_remove_recursive(file->dir);

	remove_subsystem(file->system);

	kmem_cache_free(file_cachep, file);

}



/*

 * Open and update trace_array ref count.

 * Must have the current trace_array passed to it.

 */

static int tracing_open_generic_file(struct inode *inode, struct file *filp)

{

	struct ftrace_event_file *file = inode->i_private;

	struct trace_array *tr = file->tr;

	int ret;

	struct dentry *dir = file->dir;

	struct dentry *child;



	if (trace_array_get(tr) < 0)

		return -ENODEV;



	ret = tracing_open_generic(inode, filp);

	if (ret < 0)

		trace_array_put(tr);

	return ret;

	if (dir) {

		spin_lock(&dir->d_lock);	/* probably unneeded */

		list_for_each_entry(child, &dir->d_subdirs, d_u.d_child) {

			if (child->d_inode)	/* probably unneeded */

				child->d_inode->i_private = NULL;

		}

		spin_unlock(&dir->d_lock);



static int tracing_release_generic_file(struct inode *inode, struct file *filp)

{

	struct ftrace_event_file *file = inode->i_private;

	struct trace_array *tr = file->tr;



	trace_array_put(tr);

		debugfs_remove_recursive(dir);

	}



	return 0;

	list_del(&file->list);

	remove_subsystem(file->system);

	kmem_cache_free(file_cachep, file);

}



/*
@@ -1281,10 +1265,9 @@ static const struct file_operations ftrace_set_event_fops = { 
};



static const struct file_operations ftrace_enable_fops = {

	.open = tracing_open_generic_file,

	.open = tracing_open_generic,

	.read = event_enable_read,

	.write = event_enable_write,

	.release = tracing_release_generic_file,

	.llseek = default_llseek,

};