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linux/fs/cifs/Kconfig
David Howells 70431bfd82 cifs: Support fscache indexing rewrite 
Change the cifs filesystem to take account of the changes to fscache's
indexing rewrite and reenable caching in cifs.

The following changes have been made:

 (1) The fscache_netfs struct is no more, and there's no need to register
     the filesystem as a whole.

 (2) The session cookie is now an fscache_volume cookie, allocated with
     fscache_acquire_volume().  That takes three parameters: a string
     representing the "volume" in the index, a string naming the cache to
     use (or NULL) and a u64 that conveys coherency metadata for the
     volume.

     For cifs, I've made it render the volume name string as:

	"cifs,<ipaddress>,<sharename>"

     where the sharename has '/' characters replaced with ';'.

     This probably needs rethinking a bit as the total name could exceed
     the maximum filename component length.

     Further, the coherency data is currently just set to 0.  It needs
     something else doing with it - I wonder if it would suffice simply to
     sum the resource_id, vol_create_time and vol_serial_number or maybe
     hash them.

 (3) The fscache_cookie_def is no more and needed information is passed
     directly to fscache_acquire_cookie().  The cache no longer calls back
     into the filesystem, but rather metadata changes are indicated at
     other times.

     fscache_acquire_cookie() is passed the same keying and coherency
     information as before.

 (4) The functions to set/reset cookies are removed and
     fscache_use_cookie() and fscache_unuse_cookie() are used instead.

     fscache_use_cookie() is passed a flag to indicate if the cookie is
     opened for writing.  fscache_unuse_cookie() is passed updates for the
     metadata if we changed it (ie. if the file was opened for writing).

     These are called when the file is opened or closed.

 (5) cifs_setattr_*() are made to call fscache_resize() to change the size
     of the cache object.

 (6) The functions to read and write data are stubbed out pending a
     conversion to use netfslib.

Changes
=======
ver #8:
 - Abstract cache invalidation into a helper function.
 - Fix some checkpatch warnings[3].

ver #7:
 - Removed the accidentally added-back call to get the super cookie in
   cifs_root_iget().
 - Fixed the right call to cifs_fscache_get_super_cookie() to take account
   of the "-o fsc" mount flag.

ver #6:
 - Moved the change of gfpflags_allow_blocking() to current_is_kswapd() for
   cifs here.
 - Fixed one of the error paths in cifs_atomic_open() to jump around the
   call to use the cookie.
 - Fixed an additional successful return in the middle of cifs_open() to
   use the cookie on the way out.
 - Only get a volume cookie (and thus inode cookies) when "-o fsc" is
   supplied to mount.

ver #5:
 - Fixed a couple of bits of cookie handling[2]:
   - The cookie should be released in cifs_evict_inode(), not
     cifsFileInfo_put_final().  The cookie needs to persist beyond file
     closure so that writepages will be able to write to it.
   - fscache_use_cookie() needs to be called in cifs_atomic_open() as it is
     for cifs_open().

ver #4:
 - Fixed the use of sizeof with memset.
 - tcon->vol_create_time is __le64 so doesn't need cpu_to_le64().

ver #3:
 - Canonicalise the cifs coherency data to make the cache portable.
 - Set volume coherency data.

ver #2:
 - Use gfpflags_allow_blocking() rather than using flag directly.
 - Upgraded to -rc4 to allow for upstream changes[1].
 - fscache_acquire_volume() now returns errors.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Jeff Layton <jlayton@kernel.org>
cc: Steve French <smfrench@gmail.com>
cc: Shyam Prasad N <nspmangalore@gmail.com>
cc: linux-cifs@vger.kernel.org
cc: linux-cachefs@redhat.com
Link: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=23b55d673d7527b093cd97b7c217c82e70cd1af0 [1]
Link: https://lore.kernel.org/r/3419813.1641592362@warthog.procyon.org.uk/ [2]
Link: https://lore.kernel.org/r/CAH2r5muTanw9pJqzAHd01d9A8keeChkzGsCEH6=0rHutVLAF-A@mail.gmail.com/ [3]
Link: https://lore.kernel.org/r/163819671009.215744.11230627184193298714.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/163906982979.143852.10672081929614953210.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/163967187187.1823006.247415138444991444.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/164021579335.640689.2681324337038770579.stgit@warthog.procyon.org.uk/ # v4
Link: https://lore.kernel.org/r/3462849.1641593783@warthog.procyon.org.uk/ # v5
Link: https://lore.kernel.org/r/1318953.1642024578@warthog.procyon.org.uk/ # v6
Signed-off-by: Steve French <stfrench@microsoft.com>
2022-01-19 11:21:08 -06:00

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# SPDX-License-Identifier: GPL-2.0-only
config CIFS
tristate "SMB3 and CIFS support (advanced network filesystem)"
depends on INET
select NLS
select CRYPTO
select CRYPTO_MD5
select CRYPTO_SHA256
select CRYPTO_SHA512
select CRYPTO_CMAC
select CRYPTO_HMAC
select CRYPTO_AEAD2
select CRYPTO_CCM
select CRYPTO_GCM
select CRYPTO_ECB
select CRYPTO_AES
select KEYS
select DNS_RESOLVER
select ASN1
select OID_REGISTRY
help
This is the client VFS module for the SMB3 family of NAS protocols,
(including support for the most recent, most secure dialect SMB3.1.1)
as well as for earlier dialects such as SMB2.1, SMB2 and the older
Common Internet File System (CIFS) protocol. CIFS was the successor
to the original dialect, the Server Message Block (SMB) protocol, the
native file sharing mechanism for most early PC operating systems.
The SMB3 protocol is supported by most modern operating systems
and NAS appliances (e.g. Samba, Windows 10, Windows Server 2016,
MacOS) and even in the cloud (e.g. Microsoft Azure).
The older CIFS protocol was included in Windows NT4, 2000 and XP (and
later) as well by Samba (which provides excellent CIFS and SMB3
server support for Linux and many other operating systems). Use of
dialects older than SMB2.1 is often discouraged on public networks.
This module also provides limited support for OS/2 and Windows ME
and similar very old servers.
This module provides an advanced network file system client
for mounting to SMB3 (and CIFS) compliant servers. It includes
support for DFS (hierarchical name space), secure per-user
session establishment via Kerberos or NTLM or NTLMv2, RDMA
(smbdirect), advanced security features, per-share encryption,
directory leases, safe distributed caching (oplock), optional packet
signing, Unicode and other internationalization improvements.
In general, the default dialects, SMB3 and later, enable better
performance, security and features, than would be possible with CIFS.
Note that when mounting to Samba, due to the CIFS POSIX extensions,
CIFS mounts can provide slightly better POSIX compatibility
than SMB3 mounts. SMB2/SMB3 mount options are also
slightly simpler (compared to CIFS) due to protocol improvements.
If you need to mount to Samba, Azure, Macs or Windows from this machine, say Y.
config CIFS_STATS2
bool "Extended statistics"
depends on CIFS
default y
help
Enabling this option will allow more detailed statistics on SMB
request timing to be displayed in /proc/fs/cifs/DebugData and also
allow optional logging of slow responses to dmesg (depending on the
value of /proc/fs/cifs/cifsFYI). See Documentation/admin-guide/cifs/usage.rst
for more details. These additional statistics may have a minor effect
on performance and memory utilization.
If unsure, say Y.
config CIFS_ALLOW_INSECURE_LEGACY
bool "Support legacy servers which use less secure dialects"
depends on CIFS
default y
help
Modern dialects, SMB2.1 and later (including SMB3 and 3.1.1), have
additional security features, including protection against
man-in-the-middle attacks and stronger crypto hashes, so the use
of legacy dialects (SMB1/CIFS and SMB2.0) is discouraged.
Disabling this option prevents users from using vers=1.0 or vers=2.0
on mounts with cifs.ko
If unsure, say Y.
config CIFS_UPCALL
bool "Kerberos/SPNEGO advanced session setup"
depends on CIFS
help
Enables an upcall mechanism for CIFS which accesses userspace helper
utilities to provide SPNEGO packaged (RFC 4178) Kerberos tickets
which are needed to mount to certain secure servers (for which more
secure Kerberos authentication is required). If unsure, say Y.
config CIFS_XATTR
bool "CIFS extended attributes"
depends on CIFS
help
Extended attributes are name:value pairs associated with inodes by
the kernel or by users (see the attr(5) manual page for details).
CIFS maps the name of extended attributes beginning with the user
namespace prefix to SMB/CIFS EAs. EAs are stored on Windows
servers without the user namespace prefix, but their names are
seen by Linux cifs clients prefaced by the user namespace prefix.
The system namespace (used by some filesystems to store ACLs) is
not supported at this time.
If unsure, say Y.
config CIFS_POSIX
bool "CIFS POSIX Extensions"
depends on CIFS && CIFS_ALLOW_INSECURE_LEGACY && CIFS_XATTR
help
Enabling this option will cause the cifs client to attempt to
negotiate a newer dialect with servers, such as Samba 3.0.5
or later, that optionally can handle more POSIX like (rather
than Windows like) file behavior. It also enables
support for POSIX ACLs (getfacl and setfacl) to servers
(such as Samba 3.10 and later) which can negotiate
CIFS POSIX ACL support. If unsure, say N.
config CIFS_DEBUG
bool "Enable CIFS debugging routines"
default y
depends on CIFS
help
Enabling this option adds helpful debugging messages to
the cifs code which increases the size of the cifs module.
If unsure, say Y.
config CIFS_DEBUG2
bool "Enable additional CIFS debugging routines"
depends on CIFS_DEBUG
help
Enabling this option adds a few more debugging routines
to the cifs code which slightly increases the size of
the cifs module and can cause additional logging of debug
messages in some error paths, slowing performance. This
option can be turned off unless you are debugging
cifs problems. If unsure, say N.
config CIFS_DEBUG_DUMP_KEYS
bool "Dump encryption keys for offline decryption (Unsafe)"
depends on CIFS_DEBUG
help
Enabling this will dump the encryption and decryption keys
used to communicate on an encrypted share connection on the
console. This allows Wireshark to decrypt and dissect
encrypted network captures. Enable this carefully.
If unsure, say N.
config CIFS_DFS_UPCALL
bool "DFS feature support"
depends on CIFS
help
Distributed File System (DFS) support is used to access shares
transparently in an enterprise name space, even if the share
moves to a different server. This feature also enables
an upcall mechanism for CIFS which contacts userspace helper
utilities to provide server name resolution (host names to
IP addresses) which is needed in order to reconnect to
servers if their addresses change or for implicit mounts of
DFS junction points. If unsure, say Y.
config CIFS_SWN_UPCALL
bool "SWN feature support"
depends on CIFS
help
The Service Witness Protocol (SWN) is used to get notifications
from a highly available server of resource state changes. This
feature enables an upcall mechanism for CIFS which contacts a
userspace daemon to establish the DCE/RPC connection to retrieve
the cluster available interfaces and resource change notifications.
If unsure, say Y.
config CIFS_NFSD_EXPORT
bool "Allow nfsd to export CIFS file system"
depends on CIFS && BROKEN
help
Allows NFS server to export a CIFS mounted share (nfsd over cifs)
config CIFS_SMB_DIRECT
bool "SMB Direct support"
depends on CIFS=m && INFINIBAND && INFINIBAND_ADDR_TRANS || CIFS=y && INFINIBAND=y && INFINIBAND_ADDR_TRANS=y
help
Enables SMB Direct support for SMB 3.0, 3.02 and 3.1.1.
SMB Direct allows transferring SMB packets over RDMA. If unsure,
say Y.
config CIFS_FSCACHE
bool "Provide CIFS client caching support"
depends on CIFS=m && FSCACHE || CIFS=y && FSCACHE=y
help
Makes CIFS FS-Cache capable. Say Y here if you want your CIFS data
to be cached locally on disk through the general filesystem cache
manager. If unsure, say N.
config CIFS_ROOT
bool "SMB root file system (Experimental)"
depends on CIFS=y && IP_PNP
help
Enables root file system support over SMB protocol.
Most people say N here.
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