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Version 1.53 May 20, 2008
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) Support for SecurityDescriptors(Windows/CIFS ACLs) for chmod/chgrp/chown
so that these operations can be supported to Windows servers
b) Mapping POSIX ACLs (and eventually NFSv4 ACLs) to CIFS
c) Better pam/winbind integration (e.g. to handle uid mapping
d) Cleanup now unneeded SessSetup code in
fs/cifs/connect.c and add back in NTLMSSP code if any servers
need it
e) fix NTLMv2 signing when two mounts with different users to same
f) Directory entry caching relies on a 1 second timer, rather than
using FindNotify or equivalent. - (started)
g) quota support (needs minor kernel change since quota calls
to make it to network filesystems or deviceless filesystems)
h) investigate sync behavior (including syncpage) and check
for proper behavior of intr/nointr
i) improve support for very old servers (OS/2 and Win9x for example)
Including support for changing the time remotely (utimes command).
j) hook lower into the sockets api (as NFS/SunRPC does) to avoid the
extra copy in/out of the socket buffers in some cases.
k) 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).
l) Improve performance of readpages by sending more than one read
at a time when 8 pages or more are requested. In conjuntion
add support for async_cifs_readpages.
m) Add support for storing symlink info to Windows servers
in the Extended Attribute format their SFU clients would recognize.
n) Finish fcntl D_NOTIFY 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.
o) Add GUI tool to configure /proc/fs/cifs settings and for display of
the CIFS statistics (started)
p) implement support for security and trusted categories of xattrs
(requires minor protocol extension) to enable better support for SELINUX
q) Implement O_DIRECT flag on open (already supported on mount)
r) 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.
s) Add support for CIFS Unix and also the newer POSIX extensions to the
server side for Samba 4.
t) In support for OS/2 (LANMAN 1.2 and LANMAN2.1 based SMB servers)
need to add ability to set time to server (utimes command)
u) DOS attrs - returned as pseudo-xattr in Samba format (check VFAT and NTFS for this too)
v) mount check for unmatched uids
w) Add support for new vfs entry points for setlease and fallocate
x) Fix Samba 3 server to handle Linux kernel aio so dbench with lots of
processes can proceed better in parallel (on the server)
y) Fix Samba 3 to handle reads/writes over 127K (and remove the cifs mount
restriction of wsize max being 127K)
KNOWN BUGS (updated April 24, 2007)
See - search on product "CifsVFS" for
current bug list.
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
3) create of new files to FAT partitions on Windows servers can
succeed but still return access denied (appears to be Windows
server not cifs client problem) and has not been reproduced recently.
NTFS partitions do not have this problem.
4) Unix/POSIX capabilities are reset after reconnection, and affect
a few fields in the tree connection but we do do not know which
superblocks to apply these changes to. We should probably walk
the list of superblocks to set these. Also need to check the
flags on the second mount to the same share, and see if we
can do the same trick that NFS does to remount duplicate shares.
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) Modify file portion of ltp so it can run against a mounted network
share and run it against cifs vfs in automated fashion.
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. More testing
against Windows 9x, Windows ME servers.