support for mknod to windows now in cifs vfs

Steve French smfrench at
Sat Nov 19 19:55:37 GMT 2005

Andrew Bartlett wrote:

>On Fri, 2005-11-18 at 22:30 -0600, Steve French wrote:
>>I added the code to cifs vfs to enable it do mknod of block and 
>>chardevice even if the server does not support the Unix extensions (such 
>>as Windows).  This requires the "sfu" mount option to be specified 
>Any reason why this isn't on by default? 
>Andrew Bartlett

I agree with most of Martin's points - even on Windows there are a few 
(possibly with Vista) three ways e.g. to do symlinks.  Although sfu is 
the most important way to do it it is a bit slower too.

The "sfu" mount option (services for Unix) is not turned on by default 
on mounts from cifs vfs to Windows servers (and servers which unlike 
Samba do not support the CIFS Unix/POSIX extensions) because it is 
slightly slower.

Checking the mode bits requires:
1) An extra roundtrip on each lookup for query of an Extended Attributed 
(xattr) for the top 3 bits of the mode and eventually an extra one 
beyond that for getting the security descriptor (for the bottom nine 
bits, 0777 part, of the mode).  This would be particularly expensive on 
2) An extra read for every non-empty file marked with the "system" 
attribute (dos attribute) to see if the file begins with a signature 
indicating (block, char or symlink)

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