Re: MPSAFE VFS -- List of upcoming actions

On Wed, Sep 19, 2012 at 3:48 AM, Attilio Rao <attilio_at_freebsd.org> wrote:
> On Fri, Jul 13, 2012 at 12:18 AM, Attilio Rao <attilio_at_freebsd.org> wrote:
>> 2012/7/4 Attilio Rao <attilio_at_freebsd.org>:
>>> 2012/6/29 Attilio Rao <attilio_at_freebsd.org>:
>>>> As already published several times, according to the following plan:
>>>> http://wiki.freebsd.org/NONMPSAFE_DEORBIT_VFS
>>>>
>>>
>>> I still haven't heard from Vivien or Edward, anyway as NTFS is
>>> basically only used RO these days (also the mount_ntfs code just
>>> permits RO mounting) I stripped all the uncomplete/bogus write support
>>> with the following patch:
>>> http://www.freebsd.org/~attilio/ntfs_remove_write.patch
>>>
>>> This is an attempt to make the code smaller and possibly just focus on
>>> the locking that really matter (as read-only filesystem).
>>> On some points of the patch I'm a bit less sure as we could easily
>>> take into account also write for things like vaccess() arguments, and
>>> make easier to re-add correct write support at some point in the
>>> future, but still force RO, even if the approach used in the patch is
>>> more correct IMHO.
>>> As an added bonus this patch cleans some dirty code in the mount
>>> operation and fixes a bug as vfs_mountedfrom() is called before real
>>> mounting is completed and can still fail.
>>
>> A quick update on this.
>> It looks like NTFS won't be completed for this GSoC thus I seriously
>> need to find an alternative to not loose the NTFS support entirely.
>>
>> I tried to look into the NTFS implementation right now and it is
>> really a poor support. As Peter has also verified, it can deadlock in
>> no-time, it compeltely violates VFS rules, etc. IMHO it deserves a
>> complete rewrite if we would still support in-kernel NTFS. I also
>> tried to look at the NetBSD implementation. Their code is someway
>> similar to our, but they used very complicated (and very dirty) code
>> to do the locking. Even if I don't know well enough NetBSD VFS, I have
>> the impression not all the races are correctly handled. Definitively,
>> not something I would like to port.
>>
>> Considering all that the only viable option would be meaning an
>> userland filesystem implementation. My preferred choice would be to
>> import PUFFS and librefuse on top of it but honestly it requires a lot
>> of time to be completed, time which I don't currently have as in 2
>> months Giant must be gone by the VFS.
>>
>> I then decided to switch to gnn's rewamp of FUSE patches. You can find
>> his initial e-mail here:
>> http://lists.freebsd.org/pipermail/freebsd-fs/2012-March/013876.html
>>
>> I've precisely got the second version of George's patch and created
>> this dolphin branch:
>> svn://svn.freebsd.org/base/projects/fuse
>>
>> I'm fixing low hanging fruit for the moment (see r238411 for example)
>> and I still have to make a throughful review.
>> However my idea is to commit the support once:
>> - ntfs-3g is well stress-tested and proves to be bug-free
>> - there is no major/big technical issue pending after the reviews
>
> In the last weeks Peter, Florian, Gustau and I have been working in
> stabilizing fuse support. In the specific, Peter has worked hard on
> producing several utilities to nit stress-test fuse and in particular
> ntfs, Florian has improved fuse related ports (as explained later) and
> Gustau has done sparse testing. I feel moderately satisfied by the
> level of stability of fuse now to propose to wider usage, in
> particular given the huge amount of complaints I'm hearing around
> about occasional fuse users.
>
> The final target of the project is to completely import into base the
> content of fusefs-kmod starting from earlier posted patches by George.
> So far, we took care only of importing in the fuse branch the kernel
> part, so that fusefs-kmod userland part is still needed to be
> installed from ports, but I was studying the mount_fusefs licensing
> before to process with the import for the userland bits of it.
>
> The fixing has been happening here:
> svn://svn.freebsd.org/base/projects/fuse/
>
> which is essentially an HEAD branch + fuse kernel components. In order
> to get fuse, please compile a kernel from this branch with FUSE option
> or simply build and load fuse module.
> Alternatively, a kernel patch that should work with HEAD_at_240684 is here:
> http://www.freebsd.org/~attilio/fuse_import/fuse_240684.patch
>
> I guess the patch can easilly apply to all FreeBSD branches, really,
> but it is not tested to anything else different then -CURRENT.
>
> As said you still need currently to build fusefs-kmod port. However
> you need these further patches, to be put in the fusefs-kmod/files/
> directory::
> http://www.freebsd.org/~attilio/fuse_import/patch-Makefile
> http://www.freebsd.org/~attilio/fuse_import/patch-mount_fusefs__mount_fusefs2.c
>
> They both disable the old kernel building/linking and import new
> functionality to let the new kernel support work well in presence of
> many consumers.
>
> In addition to fusefs-kmod, Bryan and Florian have also updated
> fusefs-lib and fusefs-ntfs ports. For instance, please refer to this
> e-mail:
> http://lists.freebsd.org/pipermail/freebsd-ports/2012-August/077950.html
>
> Even if this work is someway independent by the fusefs-kmod import, I
> warmly suggest to all of you to use their patches (and this what we
> have been testing so far too.

So, after Bryan and Florian ports update, I've also committed userland
part of fusefs-kmod and now the project branch fully mirrors
functionality of fusefs-kmod. The code in projects/fuse, infact, will
also install mount_fusefs as part of the fuse support.

You can use the branch directly or this patch against -CURRENT at 240752:
http://www.freebsd.org/~attilio/fuse_import/fuse_240752.patch

In order to test this work, then, you just need to patch (or use
directly the branch) your sources with this patch and install ports
normally as they work.

If no major bugs are found before October 4th, this is the code that
is going to be committed to HEAD.

Thanks,
Attilio


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