vfs: add try_take_dentry_name_snapshot()

take_dentry_name_snapshot() requires the caller to keep the dentry
alive. The external name of a dead dentry has a zero refcount that
never changes, so atomic_inc_not_zero() fails on every retry and the
function never returns.

A caller in RCU walk holds no reference on the dentry. Add a variant
that fails instead of retrying when it cannot get a reference on the
external name, so such a caller can return -ECHILD.

Reviewed-by: Christian Brauner (Amutable) <brauner@kernel.org>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>

0 files changed, 0 insertions, 0 deletions