Re: extended attributes and lsextattr/extattr_list_file

[Emmanuel Dreyfus <manu%netbsd.org@localhost>]

On Wed, Jun 29, 2011 at 04:55:30AM +0200, Emmanuel Dreyfus wrote:
> perhaps this is just a bug, since the documentation does not tell about
> this prepended one byte length. The funny thing is that glusterfs has a
> code section for FreeBSD that uses extattr_list_link(), but it assumes
> the behavior from the documentation and is therefore broken with the
> original extattr_list_link() implementation.

I checked FreeBSD status on this. The original documentation we 
imported from them describe extattr_list_file() returning
data like the Linux flavor listxattr(), that is with NUL-terminated
strings. 

FreeBSD's doc/79261 reports that problem, and they decided to stick
with this implementation and to fix the documentation:
http://www.freebsd.org/cgi/query-pr.cgi?pr=79261
http://www.freebsd.org/cgi/cvsweb.cgi/src/lib/libc/sys/extattr_get_file.2.diff?r1=1.16;r2=1.17

That weakens my point about sticking to the documentd behaviour, and I guess 
I need to revert extattr_list__file() output to what it was before and fix
the doc like FreeBSD did.

It is easy to do the conversion so that our Linux-like listexattr() returns
NUL-separated strings, while our FreeBSD-like extattr_list_file() returns
one-byte length prefixed strings. The question is what should our vnode
interface (VOP_LISTEXTATTR) require? Linux-like format is also used 
by MacOS X and FUSE, so it will make FUSE code simplier, so I will go
for that second option. This means I leave src/sys/ufs/ufs/ufs_extattr.c
as is and just convert the output in src/sys/kern/vfs_xattr.c

-- 
Emmanuel Dreyfus
manu%netbsd.org@localhost