Documentation/filesystems/cifs/TODO - kernel/bruno - Git at Google

 Version 2.03 August 1, 2014

 A Partial List of Missing Features
 ==================================

 Contributions are welcome.  There are plenty of opportunities
 for visible, important contributions to this module.  Here
 is a partial list of the known problems and missing features:

 a) SMB3 (and SMB3.02) missing optional features:
    - RDMA
    - multichannel (started)
    - directory leases (improved metadata caching)
    - T10 copy offload (copy chunk is only mechanism supported)
    - encrypted shares

 b) improved sparse file support

 c) Directory entry caching relies on a 1 second timer, rather than
 using FindNotify or equivalent.  - (started)

 d) quota support (needs minor kernel change since quota calls
 to make it to network filesystems or deviceless filesystems)

 e) improve support for very old servers (OS/2 and Win9x for example)
 Including support for changing the time remotely (utimes command).

 f) hook lower into the sockets api (as NFS/SunRPC does) to avoid the
 extra copy in/out of the socket buffers in some cases.

 g) Better optimize open (and pathbased setfilesize) to reduce the
 oplock breaks coming from windows srv.  Piggyback identical file
 opens on top of each other by incrementing reference count rather
 than resending (helps reduce server resource utilization and avoid
 spurious oplock breaks).

 h) Add support for storing symlink info to Windows servers
 in the Extended Attribute format their SFU clients would recognize.

 i) Finish inotify support so kde and gnome file list windows
 will autorefresh (partially complete by Asser). Needs minor kernel
 vfs change to support removing D_NOTIFY on a file.

 j) Add GUI tool to configure /proc/fs/cifs settings and for display of
 the CIFS statistics (started)

 k) implement support for security and trusted categories of xattrs
 (requires minor protocol extension) to enable better support for SELINUX

 l) Implement O_DIRECT flag on open (already supported on mount)

 m) Create UID mapping facility so server UIDs can be mapped on a per
 mount or a per server basis to client UIDs or nobody if no mapping
 exists.  This is helpful when Unix extensions are negotiated to
 allow better permission checking when UIDs differ on the server
 and client.  Add new protocol request to the CIFS protocol
 standard for asking the server for the corresponding name of a
 particular uid.

 n) DOS attrs - returned as pseudo-xattr in Samba format (check VFAT and NTFS for this too)

 o) mount check for unmatched uids

 p) Add support for new vfs entry point for fallocate

 q) Add tools to take advantage of cifs/smb3 specific ioctls and features
 such as "CopyChunk" (fast server side file copy)

 r) encrypted file support

 s) improved stats gathering, tools (perhaps integration with nfsometer?)

 t) allow setting more NTFS/SMB3 file attributes remotely (currently limited to compressed
 file attribute via chflags)

 u) mount helper GUI (to simplify the various configuration options on mount)


 KNOWN BUGS
 ====================================
 See http://bugzilla.samba.org - search on product "CifsVFS" for
 current bug list.  Also check http://bugzilla.kernel.org (Product = File System, Component = CIFS)

 1) existing symbolic links (Windows reparse points) are recognized but
 can not be created remotely. They are implemented for Samba and those that
 support the CIFS Unix extensions, although earlier versions of Samba
 overly restrict the pathnames.
 2) follow_link and readdir code does not follow dfs junctions
 but recognizes them

 Misc testing to do
 ==================
 1) check out max path names and max path name components against various server
 types. Try nested symlinks (8 deep). Return max path name in stat -f information

 2) Improve xfstest's cifs enablement and adapt xfstests where needed to test
 cifs better

 3) Additional performance testing and optimization using iozone and similar -
 there are some easy changes that can be done to parallelize sequential writes,
 and when signing is disabled to request larger read sizes (larger than
 negotiated size) and send larger write sizes to modern servers.

 4) More exhaustively test against less common servers
	Version 2.03 August 1, 2014

	A Partial List of Missing Features
	==================================

	Contributions are welcome. There are plenty of opportunities
	for visible, important contributions to this module. Here
	is a partial list of the known problems and missing features:

	a) SMB3 (and SMB3.02) missing optional features:
	- RDMA
	- multichannel (started)
	- directory leases (improved metadata caching)
	- T10 copy offload (copy chunk is only mechanism supported)
	- encrypted shares

	b) improved sparse file support

	c) Directory entry caching relies on a 1 second timer, rather than
	using FindNotify or equivalent. - (started)

	d) quota support (needs minor kernel change since quota calls
	to make it to network filesystems or deviceless filesystems)

	e) improve support for very old servers (OS/2 and Win9x for example)
	Including support for changing the time remotely (utimes command).

	f) hook lower into the sockets api (as NFS/SunRPC does) to avoid the
	extra copy in/out of the socket buffers in some cases.

	g) Better optimize open (and pathbased setfilesize) to reduce the
	oplock breaks coming from windows srv. Piggyback identical file
	opens on top of each other by incrementing reference count rather
	than resending (helps reduce server resource utilization and avoid
	spurious oplock breaks).

	h) Add support for storing symlink info to Windows servers
	in the Extended Attribute format their SFU clients would recognize.

	i) Finish inotify support so kde and gnome file list windows
	will autorefresh (partially complete by Asser). Needs minor kernel
	vfs change to support removing D_NOTIFY on a file.

	j) Add GUI tool to configure /proc/fs/cifs settings and for display of
	the CIFS statistics (started)

	k) implement support for security and trusted categories of xattrs
	(requires minor protocol extension) to enable better support for SELINUX

	l) Implement O_DIRECT flag on open (already supported on mount)

	m) Create UID mapping facility so server UIDs can be mapped on a per
	mount or a per server basis to client UIDs or nobody if no mapping
	exists. This is helpful when Unix extensions are negotiated to
	allow better permission checking when UIDs differ on the server
	and client. Add new protocol request to the CIFS protocol
	standard for asking the server for the corresponding name of a
	particular uid.

	n) DOS attrs - returned as pseudo-xattr in Samba format (check VFAT and NTFS for this too)

	o) mount check for unmatched uids

	p) Add support for new vfs entry point for fallocate

	q) Add tools to take advantage of cifs/smb3 specific ioctls and features
	such as "CopyChunk" (fast server side file copy)

	r) encrypted file support

	s) improved stats gathering, tools (perhaps integration with nfsometer?)

	t) allow setting more NTFS/SMB3 file attributes remotely (currently limited to compressed
	file attribute via chflags)

	u) mount helper GUI (to simplify the various configuration options on mount)


	KNOWN BUGS
	====================================
	See http://bugzilla.samba.org - search on product "CifsVFS" for
	current bug list. Also check http://bugzilla.kernel.org (Product = File System, Component = CIFS)

	1) existing symbolic links (Windows reparse points) are recognized but
	can not be created remotely. They are implemented for Samba and those that
	support the CIFS Unix extensions, although earlier versions of Samba
	overly restrict the pathnames.
	2) follow_link and readdir code does not follow dfs junctions
	but recognizes them

	Misc testing to do
	==================
	1) check out max path names and max path name components against various server
	types. Try nested symlinks (8 deep). Return max path name in stat -f information

	2) Improve xfstest's cifs enablement and adapt xfstests where needed to test
	cifs better

	3) Additional performance testing and optimization using iozone and similar -
	there are some easy changes that can be done to parallelize sequential writes,
	and when signing is disabled to request larger read sizes (larger than
	negotiated size) and send larger write sizes to modern servers.

	4) More exhaustively test against less common servers