d08089f649
Currently, the cifs I/O paths hand lists of pages from the VM interface
routines at the top all the way through the intervening layers to the
socket interface at the bottom.
This is a problem, however, for interfacing with netfslib which passes an
iterator through to the ->issue_read() method (and will pass an iterator
through to the ->issue_write() method in future). Netfslib takes over
bounce buffering for direct I/O, async I/O and encrypted content, so cifs
doesn't need to do that. Netfslib also converts IOVEC-type iterators into
BVEC-type iterators if necessary.
Further, cifs needs foliating - and folios may come in a variety of sizes,
so a page list pointing to an array of heterogeneous pages may cause
problems in places such as where crypto is done.
Change the cifs I/O paths to hand iov_iter iterators all the way through
instead.
Notes:
(1) Some old routines are #if'd out to be removed in a follow up patch so
as to avoid confusing diff, thereby making the diff output easier to
follow. I've removed functions that don't overlap with anything
added.
(2) struct smb_rqst loses rq_pages, rq_offset, rq_npages, rq_pagesz and
rq_tailsz which describe the pages forming the buffer; instead there's
an rq_iter describing the source buffer and an rq_buffer which is used
to hold the buffer for encryption.
(3) struct cifs_readdata and cifs_writedata are similarly modified to
smb_rqst. The ->read_into_pages() and ->copy_into_pages() are then
replaced with passing the iterator directly to the socket.
The iterators are stored in these structs so that they are persistent
and don't get deallocated when the function returns (unlike if they
were stack variables).
(4) Buffered writeback is overhauled, borrowing the code from the afs
filesystem to gather up contiguous runs of folios. The XARRAY-type
iterator is then used to refer directly to the pagecache and can be
passed to the socket to transmit data directly from there.
This includes:
cifs_extend_writeback()
cifs_write_back_from_locked_folio()
cifs_writepages_region()
cifs_writepages()
(5) Pages are converted to folios.
(6) Direct I/O uses netfs_extract_user_iter() to create a BVEC-type
iterator from an IOBUF/UBUF-type source iterator.
(7) smb2_get_aead_req() uses netfs_extract_iter_to_sg() to extract page
fragments from the iterator into the scatterlists that the crypto
layer prefers.
(8) smb2_init_transform_rq() attached pages to smb_rqst::rq_buffer, an
xarray, to use as a bounce buffer for encryption. An XARRAY-type
iterator can then be used to pass the bounce buffer to lower layers.
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Steve French <sfrench@samba.org>
cc: Shyam Prasad N <nspmangalore@gmail.com>
cc: Rohith Surabattula <rohiths.msft@gmail.com>
cc: Paulo Alcantara <pc@cjr.nz>
cc: Jeff Layton <jlayton@kernel.org>
cc: linux-cifs@vger.kernel.org
Link: https://lore.kernel.org/r/164311907995.2806745.400147335497304099.stgit@warthog.procyon.org.uk/ # rfc
Link: https://lore.kernel.org/r/164928620163.457102.11602306234438271112.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/165211420279.3154751.15923591172438186144.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/165348880385.2106726.3220789453472800240.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/165364827111.3334034.934805882842932881.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/166126396180.708021.271013668175370826.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/166697259595.61150.5982032408321852414.stgit@warthog.procyon.org.uk/ # rfc
Link: https://lore.kernel.org/r/166732031756.3186319.12528413619888902872.stgit@warthog.procyon.org.uk/ # rfc
Signed-off-by: Steve French <stfrench@microsoft.com>
206 lines
7.5 KiB
Plaintext
206 lines
7.5 KiB
Plaintext
# SPDX-License-Identifier: GPL-2.0-only
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config CIFS
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tristate "SMB3 and CIFS support (advanced network filesystem)"
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depends on INET
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select NLS
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select CRYPTO
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select CRYPTO_MD5
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select CRYPTO_SHA256
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select CRYPTO_SHA512
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select CRYPTO_CMAC
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select CRYPTO_HMAC
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select CRYPTO_AEAD2
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select CRYPTO_CCM
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select CRYPTO_GCM
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select CRYPTO_ECB
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select CRYPTO_AES
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select KEYS
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select DNS_RESOLVER
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select ASN1
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select OID_REGISTRY
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select NETFS_SUPPORT
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help
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This is the client VFS module for the SMB3 family of network file
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protocols (including the most recent, most secure dialect SMB3.1.1).
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This module also includes support for earlier dialects such as
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SMB2.1, SMB2 and even the old Common Internet File System (CIFS)
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protocol. CIFS was the successor to the original network filesystem
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protocol, Server Message Block (SMB ie SMB1), the native file sharing
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mechanism for most early PC operating systems.
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The SMB3.1.1 protocol is supported by most modern operating systems
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and NAS appliances (e.g. Samba, Windows 11, Windows Server 2022,
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MacOS) and even in the cloud (e.g. Microsoft Azure) and also by the
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Linux kernel server, ksmbd. Support for the older CIFS protocol was
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included in Windows NT4, 2000 and XP (and later). Use of dialects
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older than SMB2.1 is often discouraged on public networks.
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This module also provides limited support for OS/2 and Windows ME
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and similar very old servers.
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This module provides an advanced network file system client for
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mounting to SMB3 (and CIFS) compliant servers. It includes support
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for DFS (hierarchical name space), secure per-user session
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establishment via Kerberos or NTLMv2, RDMA (smbdirect), advanced
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security features, per-share encryption, packet-signing, snapshots,
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directory leases, safe distributed caching (leases), multichannel,
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Unicode and other internationalization improvements.
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In general, the default dialects, SMB3 and later, enable better
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performance, security and features, than would be possible with CIFS.
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If you need to mount to Samba, Azure, ksmbd, Macs or Windows from this
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machine, say Y.
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config CIFS_STATS2
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bool "Extended statistics"
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depends on CIFS
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default y
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help
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Enabling this option will allow more detailed statistics on SMB
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request timing to be displayed in /proc/fs/cifs/DebugData and also
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allow optional logging of slow responses to dmesg (depending on the
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value of /proc/fs/cifs/cifsFYI). See Documentation/admin-guide/cifs/usage.rst
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for more details. These additional statistics may have a minor effect
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on performance and memory utilization.
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If unsure, say Y.
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config CIFS_ALLOW_INSECURE_LEGACY
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bool "Support legacy servers which use less secure dialects"
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depends on CIFS
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default y
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help
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Modern dialects, SMB2.1 and later (including SMB3 and 3.1.1), have
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additional security features, including protection against
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man-in-the-middle attacks and stronger crypto hashes, so the use
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of legacy dialects (SMB1/CIFS and SMB2.0) is discouraged.
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Disabling this option prevents users from using vers=1.0 or vers=2.0
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on mounts with cifs.ko
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If unsure, say Y.
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config CIFS_UPCALL
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bool "Kerberos/SPNEGO advanced session setup"
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depends on CIFS
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help
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Enables an upcall mechanism for CIFS which accesses userspace helper
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utilities to provide SPNEGO packaged (RFC 4178) Kerberos tickets
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which are needed to mount to certain secure servers (for which more
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secure Kerberos authentication is required). If unsure, say Y.
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config CIFS_XATTR
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bool "CIFS extended attributes"
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depends on CIFS
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help
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Extended attributes are name:value pairs associated with inodes by
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the kernel or by users (see the attr(5) manual page for details).
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CIFS maps the name of extended attributes beginning with the user
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namespace prefix to SMB/CIFS EAs. EAs are stored on Windows
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servers without the user namespace prefix, but their names are
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seen by Linux cifs clients prefaced by the user namespace prefix.
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The system namespace (used by some filesystems to store ACLs) is
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not supported at this time.
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If unsure, say Y.
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config CIFS_POSIX
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bool "CIFS POSIX Extensions"
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depends on CIFS && CIFS_ALLOW_INSECURE_LEGACY && CIFS_XATTR
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help
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Enabling this option will cause the cifs client to attempt to
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negotiate a feature of the older cifs dialect with servers, such as
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Samba 3.0.5 or later, that optionally can handle more POSIX like
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(rather than Windows like) file behavior. It also enables support
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for POSIX ACLs (getfacl and setfacl) to servers (such as Samba 3.10
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and later) which can negotiate CIFS POSIX ACL support. This config
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option is not needed when mounting with SMB3.1.1. If unsure, say N.
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config CIFS_DEBUG
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bool "Enable CIFS debugging routines"
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default y
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depends on CIFS
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help
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Enabling this option adds helpful debugging messages to
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the cifs code which increases the size of the cifs module.
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If unsure, say Y.
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config CIFS_DEBUG2
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bool "Enable additional CIFS debugging routines"
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depends on CIFS_DEBUG
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help
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Enabling this option adds a few more debugging routines
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to the cifs code which slightly increases the size of
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the cifs module and can cause additional logging of debug
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messages in some error paths, slowing performance. This
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option can be turned off unless you are debugging
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cifs problems. If unsure, say N.
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config CIFS_DEBUG_DUMP_KEYS
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bool "Dump encryption keys for offline decryption (Unsafe)"
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depends on CIFS_DEBUG
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help
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Enabling this will dump the encryption and decryption keys
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used to communicate on an encrypted share connection on the
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console. This allows Wireshark to decrypt and dissect
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encrypted network captures. Enable this carefully.
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If unsure, say N.
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config CIFS_DFS_UPCALL
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bool "DFS feature support"
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depends on CIFS
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help
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Distributed File System (DFS) support is used to access shares
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transparently in an enterprise name space, even if the share
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moves to a different server. This feature also enables
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an upcall mechanism for CIFS which contacts userspace helper
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utilities to provide server name resolution (host names to
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IP addresses) which is needed in order to reconnect to
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servers if their addresses change or for implicit mounts of
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DFS junction points. If unsure, say Y.
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config CIFS_SWN_UPCALL
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bool "SWN feature support"
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depends on CIFS
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help
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The Service Witness Protocol (SWN) is used to get notifications
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from a highly available server of resource state changes. This
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feature enables an upcall mechanism for CIFS which contacts a
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userspace daemon to establish the DCE/RPC connection to retrieve
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the cluster available interfaces and resource change notifications.
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If unsure, say Y.
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config CIFS_NFSD_EXPORT
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bool "Allow nfsd to export CIFS file system"
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depends on CIFS && BROKEN
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help
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Allows NFS server to export a CIFS mounted share (nfsd over cifs)
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if CIFS
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config CIFS_SMB_DIRECT
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bool "SMB Direct support"
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depends on CIFS=m && INFINIBAND && INFINIBAND_ADDR_TRANS || CIFS=y && INFINIBAND=y && INFINIBAND_ADDR_TRANS=y
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help
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Enables SMB Direct support for SMB 3.0, 3.02 and 3.1.1.
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SMB Direct allows transferring SMB packets over RDMA. If unsure,
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say Y.
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config CIFS_FSCACHE
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bool "Provide CIFS client caching support"
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depends on CIFS=m && FSCACHE || CIFS=y && FSCACHE=y
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help
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Makes CIFS FS-Cache capable. Say Y here if you want your CIFS data
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to be cached locally on disk through the general filesystem cache
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manager. If unsure, say N.
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config CIFS_ROOT
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bool "SMB root file system (Experimental)"
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depends on CIFS=y && IP_PNP
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help
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Enables root file system support over SMB protocol.
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Most people say N here.
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endif
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