ksmbd: start file id allocation at 1

ksmbd: start file id allocation at 1

ksmbd allocates both the volatile id (per-session file table) and the
persistent id (global file table) with idr_alloc_cyclic() starting at 0.
The first open after the module loads therefore gets volatile id 0 and
persistent id 0, and ksmbd returns an SMB2 FileId of {0, 0} in the create
response.

Clients treat an all-zero FileId as a null handle. smbtorture's
smb2_util_handle_empty() considers {0, 0} empty, so tests that guard the
close with it (e.g. smb2.oplock.statopen1, smb2.lease.statopen*) never
close that first handle. The leaked open keeps the inode's oplock count
non-zero, so a later batch oplock request on the same file is downgraded
to level II and the test fails.

Start the id allocation at 1 (KSMBD_START_FID) so no handle is ever
assigned a {0, 0} FileId, matching the behaviour of other SMB servers.

Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>