ksmbd: add support for durable handles v1/v2

Durable file handles allow reopening a file preserved on a short
network outage and transparent client reconnection within a timeout.
i.e. Durable handles aren't necessarily cleaned up when the opening
process terminates.

This patch add support for durable handle version 1 and 2.

To prove durable handles work on ksmbd, I have tested this patch with
the following smbtorture tests:

smb2.durable-open.open-oplock
smb2.durable-open.open-lease
smb2.durable-open.reopen1
smb2.durable-open.reopen1a
smb2.durable-open.reopen1a-lease
smb2.durable-open.reopen2
smb2.durable-open.reopen2a
smb2.durable-open.reopen2-lease
smb2.durable-open.reopen2-lease-v2
smb2.durable-open.reopen3
smb2.durable-open.reopen4
smb2.durable-open.delete_on_close2
smb2.durable-open.file-position
smb2.durable-open.lease
smb2.durable-open.alloc-size
smb2.durable-open.read-only
smb2.durable-v2-open.create-blob
smb2.durable-v2-open.open-oplock
smb2.durable-v2-open.open-lease
smb2.durable-v2-open.reopen1
smb2.durable-v2-open.reopen1a
smb2.durable-v2-open.reopen1a-lease
smb2.durable-v2-open.reopen2
smb2.durable-v2-open.reopen2b

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

ksmbd: lazy v2 lease break on smb2_write()

Don't immediately send directory lease break notification on smb2_write().
Instead, It postpones it until smb2_close().

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

ksmbd: send v2 lease break notification for directory

If client send different parent key, different client guid, or there is
no parent lease key flags in create context v2 lease, ksmbd send lease
break to client.

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

ksmbd: downgrade RWH lease caching state to RH for directory

RWH(Read + Write + Handle) caching state is not supported for directory.
ksmbd downgrade it to RH for directory if client send RWH caching lease
state.

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

ksmbd: set epoch in create context v2 lease

To support v2 lease(directory lease), ksmbd set epoch in create context
v2 lease response.

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

smb: move client and server files to common directory fs/smb

Move CIFS/SMB3 related client and server files (cifs.ko and ksmbd.ko
and helper modules) to new fs/smb subdirectory:

fs/cifs --> fs/smb/client
fs/ksmbd --> fs/smb/server
fs/smbfs_common --> fs/smb/common

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>