[PATCH v5 0/7] eventfs: Fixing dynamic creation

Steven Rostedt
2023-10-31T22:34:25Z

I found an issue with using a union between the rcu list head and
the "is_freed" boolean (word). That is, rcu list is a single link
list where the last element has a NULL pointer. That means, if
the eventfs_inode is the last element (which it likely will be)
it will not have its flag set to is_free.

Instead use a bit from nr_entries to be the is_freed flag.

Changes since v4: https://lore.kernel.org/linux-trace-kernel/20231031193109.018322397@goodmis.org/

- Updated on top of the change to separate out is_freed from the union

- Add another fix to only delete the eventfs_inode after the last
dentry has cleared its reference (there's more races there without
doing that)

- Make the top level eventfs directory the same as the rest in
being removed.

Steven Rostedt (Google) (7):
eventfs: Remove "is_freed" union with rcu head
eventfs: Have a free_ei() that just frees the eventfs_inode
eventfs: Test for ei->is_freed when accessing ei->dentry
eventfs: Save ownership and mode
eventfs: Hold eventfs_mutex when calling callback functions
eventfs: Delete eventfs_inode when the last dentry is freed
eventfs: Remove special processing of dput() of events directory

----
fs/tracefs/event_inode.c | 431 +++++++++++++++++++++++++++++++----------------
fs/tracefs/internal.h | 27 ++-
include/linux/tracefs.h | 43 +++++
3 files changed, 353 insertions(+), 148 deletions(-)