[linux-cifs-client] w2k server "unix extensions"?
conrad at mac.com
conrad at mac.com
Fri Oct 22 23:24:12 GMT 2004
At 10:12 AM -0500 10/22/04, Steven French wrote:
>1) mapping of symlinks on files to a client only symlink format (Conrad's
>Apple client calls them xsymlinks and a definition for them is in the Linux
>cifs client header fs/cifs/cifspdu.h, but not implemented in
>Linux's cifs_symlink function yet).
>Reparse points will likely work for directory
>symlinks although investigation is needed whether relative paths are
>supported (all junction reparse points that I have seen have Windows
>local server absolute paths with drive_letter:\path)
Just in case I'd been unclear... those "xsymlinks" are created w/o
regard to destination existence, type, etc. In particular a symlink
to a file is no different than a symlink to a directory.
>2) mapping of the Windows file owner (in the SID) to its equivalent of
>local Unix UID so the correct owner shows up on the POSIX client side.
Performance *sigh* A UID & GID are wanted to satisfy "stat" calls,
but that means "stat" needs to do a wire-open (to get the SIDs via
>3) mapping of file permissions - either from the Windows ACL to an
>approximate mode that it would represent or simply storing them in an extended
>attribute or alternate data stream.
IMO clients shouldn't second guess server ACL enforcement algorithms.
A server might be presenting "Windows ACLs" based upon actual Windows
ACLs in the server's local filesystem, or the "Windows ACLs" might be
artificial - based upon Posix "mode", Posix ACLs, or even something
else. There's a downside, but I suggest client filesystems return a
permissive/optimistic mode (0777 for instance) ... the intention is
to keep application level code from preventing operations which the
server might in fact permit.
>jra and I and a few others have done some initial work exploring what
>needed for a version 2 of the CIFS Unix Extensions, perhaps called "CIFS
>POSIX Extensions" (a better name would be welcome) whose highlights would
>include a slightly improved form of CreateX and an alternative for POSIX
>byte range locking and support for "POSIX ACLs" on the wire (among other
A *nix system might choose to implement Windows ACLs locally and OTW,
and provide no support for "POSIX ACLs".
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