On Tue, 31 Oct 2023 18:33:27 -0400 Steven Rostedt rostedt@goodmis.org wrote:

From: "Steven Rostedt (Google)" rostedt@goodmis.org

The eventfs_inode->is_freed was a union with the rcu_head with the assumption that when it was on the srcu list the head would contain a pointer which would make "is_freed" true. But that was a wrong assumption as the rcu head is a single link list where the last element is NULL.

Instead, split the nr_entries integer so that "is_freed" is one bit and the nr_entries is the next 31 bits. As there shouldn't be more than 10 (currently there's at most 5 to 7 depending on the config), this should not be a problem.

Yeah, even 16 bit nr_entries is enough.. (maybe the biggest user is syscall event group)

Looks good to me.

Reviewed-by: Masami Hiramatsu (Google) mhiramat@kernel.org

Thank you,

Cc: stable@vger.kernel.org Fixes: 63940449555e7 ("eventfs: Implement eventfs lookup, read, open functions") Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org

---

fs/tracefs/event_inode.c | 2 ++ fs/tracefs/internal.h | 6 +++--- 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c index 754885dfe71c..2c2c75b2ad73 100644 --- a/fs/tracefs/event_inode.c +++ b/fs/tracefs/event_inode.c @@ -824,6 +824,8 @@ static void eventfs_remove_rec(struct eventfs_inode *ei, struct list_head *head, eventfs_remove_rec(ei_child, head, level + 1); }

• ei->is_freed = 1;
• list_del_rcu(&ei->list); list_add_tail(&ei->del_list, head);

} diff --git a/fs/tracefs/internal.h b/fs/tracefs/internal.h index 64fde9490f52..c7d88aaa949f 100644 --- a/fs/tracefs/internal.h +++ b/fs/tracefs/internal.h @@ -23,6 +23,7 @@ struct tracefs_inode {

• @d_parent: pointer to the parent's dentry
• @d_children: The array of dentries to represent the files when created
• @data: The private data to pass to the callbacks

• • @is_freed: Flag set if the eventfs is on its way to be freed
  • @nr_entries: The number of items in @entries
  */

struct eventfs_inode { @@ -38,14 +39,13 @@ struct eventfs_inode { * Union - used for deletion * @del_list: list of eventfs_inode to delete * @rcu: eventfs_inode to delete in RCU

• * @is_freed:	node is freed if one of the above is set
  

  */ union { struct list_head del_list; struct rcu_head rcu;

• unsigned long		is_freed;
  

  };
• int nr_entries;

• unsigned int is_freed:1;
• unsigned int nr_entries:31;

}; static inline struct tracefs_inode *get_tracefs(const struct inode *inode) -- 2.42.0