Re: [PATCH 2/3] kernfs: don't hold kernfs_rwsem across dir_emit()

[Tejun Heo <tj@kernel.org>]

Hello, Shakeel.

On Wed, Sep 09, 2026 at 05:36:49PM -0700, Shakeel Butt wrote:
> under the lock and emit the copy, and pass it to the resume so that a
> resume within one call keys on (hash, ns_id, name) and not on the hash
> alone.

Please split this into a preparation patch for full-key resumption,
including the name copy, and a separate patch dropping kernfs_rwsem around
dir_emit(). Keep the existing locking in the preparation patch.

> +	pos = kernfs_dir_pos(ns, parent, hash, pos, name, &resumed);

The fast path in kernfs_dir_pos() still accepts the pinned node based on
active state, parent and hash alone. Please compare the saved name too
before setting resumed.

For example, akl, ala and baa have the same kernfs hash. If readdir emits
akl and it is renamed to baa while unlocked, the fast path accepts the
renamed node and rb_next() skips the unchanged ala. Falling back to the
saved key would preserve ala.

Thanks.

-- 
tejun