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: replace one-element array with flex-array member in struct smb2_ea_info

UBSAN complains about out-of-bounds array indexes on 1-element arrays in
struct smb2_ea_info.

UBSAN: array-index-out-of-bounds in fs/smb/server/smb2pdu.c:4335:15
index 1 is out of range for type 'char [1]'
CPU: 1 PID: 354 Comm: kworker/1:4 Not tainted 6.5.0-rc4 #1
Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop
Reference Platform, BIOS 6.00 07/22/2020
Workqueue: ksmbd-io handle_ksmbd_work [ksmbd]
Call Trace:
<TASK>
__dump_stack linux/lib/dump_stack.c:88
dump_stack_lvl+0x48/0x70 linux/lib/dump_stack.c:106
dump_stack+0x10/0x20 linux/lib/dump_stack.c:113
ubsan_epilogue linux/lib/ubsan.c:217
__ubsan_handle_out_of_bounds+0xc6/0x110 linux/lib/ubsan.c:348
smb2_get_ea linux/fs/smb/server/smb2pdu.c:4335
smb2_get_info_file linux/fs/smb/server/smb2pdu.c:4900
smb2_query_info+0x63ae/0x6b20 linux/fs/smb/server/smb2pdu.c:5275
__process_request linux/fs/smb/server/server.c:145
__handle_ksmbd_work linux/fs/smb/server/server.c:213
handle_ksmbd_work+0x348/0x10b0 linux/fs/smb/server/server.c:266
process_one_work+0x85a/0x1500 linux/kernel/workqueue.c:2597
worker_thread+0xf3/0x13a0 linux/kernel/workqueue.c:2748
kthread+0x2b7/0x390 linux/kernel/kthread.c:389
ret_from_fork+0x44/0x90 linux/arch/x86/kernel/process.c:145
ret_from_fork_asm+0x1b/0x30 linux/arch/x86/entry/entry_64.S:304
</TASK>

Cc: stable@vger.kernel.org
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>