Adding eventfs_remove(), this function will recursively remove dir or file info from eventfs. added a recursion check to eventfs_remove_rec() as it is really dangerous to have unchecked recursion in the kernel (we do have a fixed size stack). have the free use srcu callbacks. After the srcu grace periods are done, it adds the eventfs_file onto a llist (lockless link list) and wakes up a work queue. Then the work queue does the freeing (this needs to be done in task/workqueue context, as srcu callbacks are done in softirq context). Signed-off-by: Ajay Kaher <akaher@xxxxxxxxxx> Co-developed-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx> Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx> Tested-by: Ching-lin Yu <chinglinyu@xxxxxxxxxx> Reported-by: kernel test robot <lkp@xxxxxxxxx> Closes: https://lore.kernel.org/oe-kbuild-all/202305030611.Kas747Ev-lkp@xxxxxxxxx/ --- fs/tracefs/event_inode.c | 110 +++++++++++++++++++++++++++++++++++++++ include/linux/tracefs.h | 4 ++ 2 files changed, 114 insertions(+) diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c index 75dc8953d813..322a77be5a56 100644 --- a/fs/tracefs/event_inode.c +++ b/fs/tracefs/event_inode.c @@ -45,6 +45,7 @@ struct eventfs_file { }; static DEFINE_MUTEX(eventfs_mutex); +DEFINE_STATIC_SRCU(eventfs_srcu); static const struct file_operations eventfs_file_operations = { }; @@ -299,3 +300,112 @@ int eventfs_add_file(const char *name, umode_t mode, mutex_unlock(&eventfs_mutex); return 0; } + +static LLIST_HEAD(free_list); + +static void eventfs_workfn(struct work_struct *work) +{ + struct eventfs_file *ef, *tmp; + struct llist_node *llnode; + + llnode = llist_del_all(&free_list); + llist_for_each_entry_safe(ef, tmp, llnode, llist) { + if (ef->created && ef->dentry) + dput(ef->dentry); + kfree(ef->name); + kfree(ef->ei); + kfree(ef); + } +} + +DECLARE_WORK(eventfs_work, eventfs_workfn); + +static void free_ef(struct rcu_head *head) +{ + struct eventfs_file *ef = container_of(head, struct eventfs_file, rcu); + + if (!llist_add(&ef->llist, &free_list)) + return; + + queue_work(system_unbound_wq, &eventfs_work); +} + + + +/** + * eventfs_remove_rec - remove eventfs dir or file from list + * @ef: eventfs_file to be removed. + * + * This function recursively remove eventfs_file which + * contains info of file or dir. + */ +static void eventfs_remove_rec(struct eventfs_file *ef, int level) +{ + struct eventfs_file *ef_child; + + if (!ef) + return; + /* + * Check recursion depth. It should never be greater than 3: + * 0 - events/ + * 1 - events/group/ + * 2 - events/group/event/ + * 3 - events/group/event/file + */ + if (WARN_ON_ONCE(level > 3)) + return; + + if (ef->ei) { + /* search for nested folders or files */ + list_for_each_entry_srcu(ef_child, &ef->ei->e_top_files, list, + lockdep_is_held(&eventfs_mutex)) { + eventfs_remove_rec(ef_child, level + 1); + } + } + + if (ef->created && ef->dentry) + d_invalidate(ef->dentry); + + list_del_rcu(&ef->list); + call_srcu(&eventfs_srcu, &ef->rcu, free_ef); +} + +/** + * eventfs_remove - remove eventfs dir or file from list + * @ef: eventfs_file to be removed. + * + * This function acquire the eventfs_mutex lock and call eventfs_remove_rec() + */ +void eventfs_remove(struct eventfs_file *ef) +{ + if (!ef) + return; + + mutex_lock(&eventfs_mutex); + eventfs_remove_rec(ef, 0); + mutex_unlock(&eventfs_mutex); +} + +/** + * eventfs_remove_events_dir - remove eventfs dir or file from list + * @dentry: events's dentry to be removed. + * + * This function remove events main directory + */ +void eventfs_remove_events_dir(struct dentry *dentry) +{ + struct tracefs_inode *ti; + struct eventfs_inode *ei; + + if (!dentry || !dentry->d_inode) + return; + + ti = get_tracefs(dentry->d_inode); + if (!ti || !(ti->flags & TRACEFS_EVENT_INODE)) + return; + + ei = ti->private; + d_invalidate(dentry); + dput(dentry); + kfree(ei); +} diff --git a/include/linux/tracefs.h b/include/linux/tracefs.h index a51312ff803c..2c08edd4a739 100644 --- a/include/linux/tracefs.h +++ b/include/linux/tracefs.h @@ -40,6 +40,10 @@ int eventfs_add_top_file(const char *name, umode_t mode, struct dentry *parent, void *data, const struct file_operations *fops); +void eventfs_remove(struct eventfs_file *ef); + +void eventfs_remove_events_dir(struct dentry *dentry); + struct dentry *tracefs_create_file(const char *name, umode_t mode, struct dentry *parent, void *data, const struct file_operations *fops); -- 2.39.0
