ksmbd: close superseded durable handles through refcount handoff

ksmbd: close superseded durable handles through refcount handoff

ksmbd_close_disconnected_durable_delete_on_close() collects disconnected
durable handles for a name being superseded by a new delete-on-close
open, drops ci->m_lock, then closes each collected handle directly with
__ksmbd_close_fd().

That bypasses the FP_CLOSED and refcount handoff used by the other close
paths. If a durable reconnect or the durable scavenger already took a
reference to the same fp, the direct __ksmbd_close_fd() can free the
ksmbd_file while that other holder still owns a live reference.

Claim the disconnected durable handle before unlinking it from m_fp_list.
While holding ci->m_lock and global_ft.lock, only take ownership when the
durable lifetime reference is the only remaining reference. Then take a
transient reference, remove the fp from global_ft, mark it FP_CLOSED, and
move it to the local dispose list. If another holder already has a
reference, leave the fp linked and let that holder complete its path.

The dispose loop then drops both references owned by the claim. This keeps
the force-close path in the same refcount handoff model as the durable
scavenger and avoids leaving a live reconnected fp detached from
m_fp_list.

Fixes: 166e4c07023b ("ksmbd: supersede disconnected delete-on-close durable handle")
Signed-off-by: Gil Portnoy <dddhkts1@gmail.com>
Co-developed-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>