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

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Message-ID: <20231031223326.794680978@goodmis.org>
Date:   Tue, 31 Oct 2023 18:33:26 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org
Cc:     Masami Hiramatsu <mhiramat@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Ajay Kaher <akaher@...are.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH v5 0/7] eventfs: Fixing dynamic creation

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(-)