Date: Thu, 10 Jul 2025 20:54:51 +0300 From: Konstantin Belousov <kostikbel@gmail.com> To: Rick Macklem <rick.macklem@gmail.com> Cc: FreeBSD CURRENT <freebsd-current@freebsd.org>, Alexander Motin <mav@freebsd.org> Subject: Re: RFC: Documenting weird case w.r.t. Solaris style extended attr (ZFS) Message-ID: <aG_-a-mKGn3N-AzY@kib.kiev.ua> In-Reply-To: <CAM5tNy7QCg=Rhb%2BkPbXP0WfK8VcebV1RkgJsy7eDn=njLYXzqQ@mail.gmail.com>
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On Thu, Jul 10, 2025 at 06:59:35AM -0700, Rick Macklem wrote: > I've done a series of commits to main to add support for > Solaris style extended attributes (which I called named attributes, > which is the NFSv4 term for them). > > ZFS is currently the only local file system that will support them > and only if the ZFS property "xattr" is set to "dir". > > If "zfs set xattr=dir <volume>" is done before any user namespace > extended attributes are created for files via extattr(2), I think > everything makes sense. > --> There is one set of extended attributes that are visible through > both extattr(2) and named_attribute(7). > > However, if extattr(2) is used to create user namespace extended > attributes when "xattr=sa" and then "xattr" is set to "dir", these > extended attributes are only visible to extattr(2) and not > named_attribute(7). > --> I will note that you can use tar(1) to copy the files and then the > extended attributes become visible to named_attribute(7). > I do not see any way to avoid this, but it should at least be documented. > > So, where do you think I should document this? > - I could put it in named_attribute(7) as an additional case where > the two extended attribute system call mechanisms cannot be > used. (I was hesitant, since this is ZFS specific). > Does this sound ok, or is there somewhere better to put it? > (zfsprops(7) is another possibility, since it already documents > "sa" and "dir" values for the "xattr" property.) I do not see why not put it to named_attribute(7) page. We do not have a ban on adding important fs-specific notes in the generic documentation. More, I think it is a proper place to document the details instead of spreading them into corners. BTW, would you consider adding named attrs support to tmpfs? I believe it is useful for tmpfs to be on par with the union of all features of our local filesystems.help
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