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

[T.J. Mercier]

On Mon, Feb 16, 2026 at 10:43 PM Tejun Heo <tj@xxxxxxxxxx> wrote:
>
> 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.
>
> The patchset looks good to me.
>
> Acked-by: Tejun Heo <tj@xxxxxxxxxx>
>
> Thanks.
>
> --
> tejun

Thanks Tejun.

Amir would prefer I remove the new DELETE event support and keep only
the part for DELETE_SELF + IGNORED since adding only DELETE would
create an asymmetry with the missing CREATE support. So I will plan to
do that in V3 for this series.

Thanks,
T.J.