Re: [PATCH v2 0/3] kernfs: Add inotify IN_DELETE_SELF, IN_IGNORED support for files

[Amir Goldstein <amir73il@gmail.com>]

On Thu, Feb 12, 2026 at 01:58:11PM -0800, T.J. Mercier wrote:
> This series adds support for IN_DELETE_SELF and IN_IGNORED inotify
> events to kernfs files.
> 
> Currently, kernfs (used by cgroup and others) supports IN_MODIFY events
> but fails to notify watchers when the file is removed (e.g. during
> cgroup destruction). This forces userspace monitors to maintain resource
> intensive side-channels like pidfds, procfs polling, or redundant
> directory watches to detect when a cgroup dies and a watched file is
> removed.
> 
> By generating IN_DELETE_SELF events on destruction, we allow watchers to
> rely on a single watch descriptor for the entire lifecycle of the
> monitored file, reducing resource usage (file descriptors, CPU cycles)
> and complexity in userspace.
> 
> The series is structured as follows:
> Patch 1 refactors kernfs_elem_attr to support arbitrary event types.
> Patch 2 implements the logic to generate DELETE_SELF and IGNORED events
>         on file removal.
> Patch 3 adds selftests to verify the new behavior.
> 
> ---
> Changes in v2:
> Remove unused variables from new selftests per kernel test robot
> Fix kernfs_type argument per Tejun
> Inline checks for FS_MODIFY, FS_DELETE in kernfs_notify_workfn per Tejun
> 
> T.J. Mercier (3):
>   kernfs: allow passing fsnotify event types
>   kernfs: send IN_DELETE_SELF and IN_IGNORED on file deletion
>   selftests: memcg: Add tests IN_DELETE_SELF and IN_IGNORED on
>     memory.events
> 
>  fs/kernfs/dir.c                               |  21 +++
>  fs/kernfs/file.c                              |  20 ++-
>  fs/kernfs/kernfs-internal.h                   |   3 +
>  include/linux/kernfs.h                        |   1 +
>  .../selftests/cgroup/test_memcontrol.c        | 122 ++++++++++++++++++
>  5 files changed, 161 insertions(+), 6 deletions(-)
> 
> 
> base-commit: ba268514ea14b44570030e8ed2aef92a38679e85
> -- 
> 2.53.0.273.g2a3d683680-goog
> 

In future posts, please CC inotify patches to fsdevel and inotify maintainers.

Thanks,
Amir.