From: Steven Rostedt Add a method to the hijacked dentry descriptor of the "instances" directory to allow for rmdir to remove an instance of a multibuffer. Example: cd /debug/tracing/instances mkdir hello ls hello/ rmdir hello ls Like the mkdir method, the i_mutex is dropped for the instances directory. The instances directory is created at boot up and can not be renamed or removed. The trace_types_lock mutex is used to synchronize adding and removing of instances. I've run several stress tests with different threads trying to create and delete directories of the same name, and it has stood up fine. Cc: Al Viro Signed-off-by: Steven Rostedt --- kernel/trace/trace.c | 68 +++++++++++++++++++++++++++++++++++++++++++ kernel/trace/trace.h | 1 + kernel/trace/trace_events.c | 33 +++++++++++++++++++++ 3 files changed, 102 insertions(+) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 079f909..af7be82 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -5101,6 +5101,42 @@ static int new_instance_create(const char *name) } +static int instance_delete(const char *name) +{ + struct trace_array *tr; + int found = 0; + int ret; + + mutex_lock(&trace_types_lock); + + ret = -ENODEV; + list_for_each_entry(tr, &ftrace_trace_arrays, list) { + if (tr->name && strcmp(tr->name, name) == 0) { + found = 1; + break; + } + } + if (!found) + goto out_unlock; + + list_del(&tr->list); + + event_trace_del_tracer(tr); + debugfs_remove_recursive(tr->dir); + free_percpu(tr->data); + ring_buffer_free(tr->buffer); + + kfree(tr->name); + kfree(tr); + + ret = 0; + + out_unlock: + mutex_unlock(&trace_types_lock); + + return ret; +} + static int instance_mkdir (struct inode *inode, struct dentry *dentry, umode_t mode) { struct dentry *parent; @@ -5128,9 +5164,41 @@ static int instance_mkdir (struct inode *inode, struct dentry *dentry, umode_t m return ret; } +static int instance_rmdir(struct inode *inode, struct dentry *dentry) +{ + struct dentry *parent; + int ret; + + /* Paranoid: Make sure the parent is the "instances" directory */ + parent = hlist_entry(inode->i_dentry.first, struct dentry, d_alias); + if (WARN_ON_ONCE(parent != trace_instance_dir)) + return -ENOENT; + + /* The caller did a dget() on dentry */ + mutex_unlock(&dentry->d_inode->i_mutex); + + /* + * The inode mutex is locked, but debugfs_create_dir() will also + * take the mutex. As the instances directory can not be destroyed + * or changed in any other way, it is safe to unlock it, and + * let the dentry try. If two users try to make the same dir at + * the same time, then the instance_delete() will determine the + * winner. + */ + mutex_unlock(&inode->i_mutex); + + ret = instance_delete(dentry->d_iname); + + mutex_lock_nested(&inode->i_mutex, I_MUTEX_PARENT); + mutex_lock(&dentry->d_inode->i_mutex); + + return ret; +} + static const struct inode_operations instance_dir_inode_operations = { .lookup = simple_lookup, .mkdir = instance_mkdir, + .rmdir = instance_rmdir, }; static __init void create_trace_instances(struct dentry *d_tracer) diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h index 8aeac9b..592e8f2 100644 --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -997,6 +997,7 @@ filter_check_discard(struct ftrace_event_call *call, void *rec, extern void trace_event_enable_cmd_record(bool enable); extern int event_trace_add_tracer(struct dentry *parent, struct trace_array *tr); +extern int event_trace_del_tracer(struct trace_array *tr); extern struct mutex event_mutex; extern struct list_head ftrace_events; diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c index 58a6130..06d6bc2 100644 --- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -1709,6 +1709,20 @@ __trace_add_event_dirs(struct trace_array *tr) } } +/* Remove the event directory structure for a trace directory. */ +static void +__trace_remove_event_dirs(struct trace_array *tr) +{ + struct ftrace_event_file *file, *next; + + list_for_each_entry_safe(file, next, &tr->events, list) { + list_del(&file->list); + debugfs_remove_recursive(file->dir); + remove_subsystem(file->system); + kfree(file); + } +} + static void __add_event_to_tracers(struct ftrace_event_call *call, struct ftrace_module_file_ops *file_ops) @@ -1793,6 +1807,25 @@ int event_trace_add_tracer(struct dentry *parent, struct trace_array *tr) return 0; } +int event_trace_del_tracer(struct trace_array *tr) +{ + /* Disable any running events */ + __ftrace_set_clr_event(tr, NULL, NULL, NULL, 0); + + mutex_lock(&event_mutex); + + down_write(&trace_event_mutex); + __trace_remove_event_dirs(tr); + debugfs_remove_recursive(tr->event_dir); + up_write(&trace_event_mutex); + + tr->event_dir = NULL; + + mutex_unlock(&event_mutex); + + return 0; +} + static __init int event_trace_enable(void) { struct trace_array *tr = top_trace_array(); -- 1.7.10.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/