[PATCH 03/11] VFS: add dentry_lookup_killable()

[Al Viro]

On Tue, Aug 12, 2025 at 12:25:06PM +1000, NeilBrown wrote:
> btrfs/ioctl.c uses a "killable" lock on the directory when creating an
> destroying subvols.  overlayfs also does this.
> 
> This patch adds dentry_lookup_killable() for these users.
> 
> Possibly all dentry_lookup should be killable as there is no down-side,
> but that can come in a later patch.

Same objections re lookup_flags and it would be better to do that
at the same point where you convert the (btrfs and overlayfs?) callers.