On Wed, Mar 26, 2025 at 8:18 AM Cedric Blancher <cedric.blanc...@gmail.com> wrote: > > On Wed, 26 Mar 2025 at 10:39, Lionel Cons <lionelcons1...@gmail.com> wrote: > > > > On Tue, 25 Mar 2025 at 22:14, Rick Macklem <rick.mack...@gmail.com> wrote: > > > > > > On Tue, Mar 25, 2025 at 1:53 PM Rick Macklem <rick.mack...@gmail.com> > > > wrote: > > > > > > > > On Tue, Mar 25, 2025 at 12:06 PM Lionel Cons <lionelcons1...@gmail.com> > > > > wrote: > > > > > > > > > > On Sat, 22 Mar 2025 at 21:34, Rick Macklem <rick.mack...@gmail.com> > > > > > wrote: > > > > > > > > > > > > On Sun, Mar 9, 2025 at 5:38 AM Andrew Walker > > > > > > <awal...@ixsystems.com> wrote: > > > > > > > > > > > > > > > Since ZFS is already wired for them, adding the basics is pretty > > > > > > > > straightforward. I am not suggesting that they should replace > > > > > > > > the > > > > > > > > current FreeBSD extended attributes > > > > > > > > > > > > > > The ZFS story is more complicated. When ZFS is configured with > > > > > > > `xattr=sa`, xattrs are preferentially written into system > > > > > > > attributes > > > > > > > (SA). This was introduced IIRC primarily for performance reasons > > > > > > > This allows tiny xattrs (~100 bytes) to be stored with the dnode > > > > > > > and > > > > > > > up to 64 KiB of xattrs to be stored in the dnode spill block. If > > > > > > > additional space is needed then they are written using the > > > > > > > older-style > > > > > > > file-backed approach. > > > > > > > > > > > > > > What this means is that if someone is using this relatively common > > > > > > > configuration (the default in TrueNAS and in many Linux distros), > > > > > > > then > > > > > > > the result would be that only some xattrs written via extattr > > > > > > > would be > > > > > > > visible by directly opening the ZFS attr dir. It would also > > > > > > > introduce > > > > > > > a mechanism whereby an xattr with the same name is written to two > > > > > > > different ZFS locations, which would potentially cause you to see > > > > > > > different xattr data depending on whether you read it from > > > > > > > extattr or > > > > > > > via the attr dir. I don't know off-hand whether this could lead to > > > > > > > corruption / unexpected behavior in ZFS but if you haven't looked > > > > > > > into > > > > > > > it yet you may want to make sure you're properly handling the case > > > > > > > where someone has already written SA-backed xattrs. > > > > > > I am in the process of defining a new setting for the xattr property > > > > > > I've called "named" which would need to be set for the Solaris style > > > > > > extended attributes to work. > > > > > > > > > > > > I am making progress on the patch and am currently working through > > > > > > permissions (or authorization if you prefer). > > > > > > > > > > > > Here is what OpenZFS appears to do currently. > > > > > > I am wondering if these sound reasonable for these attributes? > > > > > > > > > > > > - When an attr directory is created for a file object, the ownership > > > > > > (uid and gid) is set to the same value as the file object. > > > > > > The mode is set to 041777 (a directory with sticky bit set and > > > > > > permissions for everyone. (It ignores the "mode" argument to > > > > > > the open.) > > > > > > --> As such, anyone who has access to the file object can access > > > > > > the extended attribute directory. > > > > > > > > > > Yes, that is the expected behaviour > > > > > > > > > > > > > > > > > - When an attribute is created in the attribute directory, the uid > > > > > > is > > > > > > set to that of the creating process (cr_uid), the gid is set to > > > > > > that > > > > > > of the directory (which is also the gid of the file object). > > > > > > The mode is set to that of a regular file with low order mode > > > > > > bits > > > > > > as specified by the "mode" argument to the openat() that created > > > > > > it. > > > > > > The mode can be changed with fchmod(2). > > > > > > --> As such, access to each attribute file is controlled by the > > > > > > attribute file's creator. > > > > > > > > > > > > Any comments on the above? > > > > > > > > > > Yes, that would be the expected behaviour. > > > > > > > > > > > > > > > > > A couple of other questions... > > > > > > - Should subdirectories of the attribute directory be supported? > > > > > > I currently do not allow this, but it appears to be supportable > > > > > > by both OpenZFS and NFSv4. > > > > > > > > > > No, please no subdirs for now. As far as I can see all consumes of > > > > > such an API (Windows, MacOS etc) use flat layouts for the attribute > > > > > and alternate data streams virtual dirs > > > > > > > > > > > > > > > > > - Does restricting this support to ZFS file systems with the > > > > > > xattr property set to "named" sound reasonable? > > > > > > > > > > What does that mean? > > > > > Also, it should be "on" by default, both in FreeBSD ZFS, UFS and NFS > > > > > >= v4.1 > > > > Hmm. I think (and the discussion with Andrew seemed to confirm it) > > > > that they do not > > > > mix well with FreeBSD/Linux style extended attributes. (For example, > > > > the code that > > > > checked access for the parent directory is disabled for FreeBSD style > > > > attributes and > > > > this is intentional, according to the comment.) > > > > > > > > Also, I doubt anyone will ever do support for UFS? (I am certainly not > > > > volunteering.) > > > > > > > > The above means that a sysadmin will need to choose between which style > > > > of extended attributes they want on a "per file system basis" and that > > > > FreeBSD > > > > style will be the default, since to change that would be a POLA > > > > violation, imho. > > > > (If others feel that having the two styles co-exist on the same file > > > > system is needed, > > > > there might be a way to do it, but doing so properly won't be easy. > > > > Another example > > > > is naming. If both co-exist on the same file system, you can end up > > > > with two different > > > > attributes with the same name. I did this during testing, so I know it > > > > can happen.) > > > > > > > > > > > > > > > > > > > > > Thanks for any comments, rick > > > > > > ps: I have not, as yet, heard any comments w.r.t. whether or > > > > > > not this should go into FreeBSD15. (No rush on this one, > > > > > > but comments would be appreciated. > > > > > > > > > > I'd prefer the integration as soon as possible. > > > > A couple of problems here. > > > > 1 - You and Cedric are the only ones that have spoken up with support > > > > for this. > > > > (Having said that, no one has spoken up against it.) > > > > 2 - Someone needs to do the "userspace" lifting at some point. > > > > I haven't yet asked, so I do not know if you feel commands like > > > > "chmod(1)" > > > > need to be "named attribute aware"? (The fchmod(2) syscall works, > > > > but > > > > does the command line need to know how to do it? If yes, this is > > > > work. > > > > Probably more than I've spent getting the syscalls to work.) > > > > 3 - A lot of the changes need to go into OpenZFS and I have no idea what > > > > their position will be? (Most of the changes are in the > > > > os/freebsd/zfs > > > > source subtree, which may make it easier?) > > > Oh, and another one... > > > Testing. I have yet to hear from anyone trying to test the code. I > > > obviously > > > do some testing, but my resources are limited. > > > > How can we do this? Grab patch, apply patch, build FreeBSD, install > > new FreeBSD kernel? > > > > The biggest issue for me is building and installing a new kernel in an > > existing FreeBSD installation, or finding someone in-house who can do > > that. > > Howto or short blog post would be nice > > @Rick: Can https://docs.freebsd.org/en/books/developers-handbook/kernelbuild/ > be used to built your patch? Not sure that still works? (At least, I think you need SRCTOP=/usr/src on the make command?)
I'd just do "make buildkernel" when in the top level of the source tree. (You need the full source tree and not just kernel sources.) Then "make installkernel" will install it. --> If you want the kernel installed under a different name, you can.. # cd /usr/obj # cd down into GENERIC (can't remember all the subdirs in between) # make KERNEL=<yourkernelname> install Once you've done a "make buildkernel", you can do the same as above and use "make SRCTOP=/usr/src" to build a kernel again, but I'm not sure thats any easier than "make buildkernel" in /usr/src? rick > > Ced > -- > Cedric Blancher <cedric.blanc...@gmail.com> > [https://plus.google.com/u/0/+CedricBlancher/] > Institute Pasteur
