Date:   Thu, 6 Sep 2018 09:25:04 +1000
From:   Stephen Rothwell <sfr@...b.auug.org.au>
To:     Chao Yu <yuchao0@...wei.com>,
        "David Howells" <dhowells@...hat.com>,
        Al Viro <viro@...IV.linux.org.uk>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Gao Xiang <gaoxiang25@...wei.com>,
        <devel@...verdev.osuosl.org>, Miao Xie <miaoxie@...wei.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Matthew Wilcox <willy@...radead.org>, <weidu.du@...wei.com>,
        <linux-erofs@...ts.ozlabs.org>
Subject: Re: [PATCH] Revert "staging: erofs: disable compiling temporarile"

Hi all,

On Wed, 29 Aug 2018 09:44:03 +1000 Stephen Rothwell <sfr@...b.auug.org.au> wrote:
>
> On Tue, 28 Aug 2018 22:13:02 +0800 Chao Yu <yuchao0@...wei.com> wrote:
> >
> > On 2018/8/28 21:05, Greg Kroah-Hartman wrote:  
> > > On Tue, Aug 28, 2018 at 04:56:43PM +0800, Chao Yu wrote:    
> > >>
> > >> On 2018/8/28 14:28, Gao Xiang wrote:    
> > >>>
> > >>> On 2018/8/28 13:44, Greg Kroah-Hartman wrote:    
> > >>>> On Tue, Aug 28, 2018 at 11:39:48AM +0800, Gao Xiang wrote:    
> > >>>>> This reverts commit 156c3df8d4db4e693c062978186f44079413d74d.
> > >>>>>
> > >>>>> Since XArray and the new mount apis aren't merged in 4.19-rc1
> > >>>>> merge window, the BROKEN mark can be reverted directly without
> > >>>>> any problems.
> > >>>>>
> > >>>>> Fixes: 156c3df8d4db ("staging: erofs: disable compiling temporarile")
> > >>>>> Cc: Matthew Wilcox <willy@...radead.org>
> > >>>>> Cc: David Howells <dhowells@...hat.com>
> > >>>>> Reviewed-by: Chao Yu <yuchao0@...wei.com>
> > >>>>> Signed-off-by: Gao Xiang <gaoxiang25@...wei.com>
> > >>>>> ---
> > >>>>>
> > >>>>> Hi Greg,
> > >>>>>
> > >>>>>  Could you please apply this patch to enable EROFS from 4.19-rc2, thanks...
> > >>>>>
> > >>>>>  p.s. We would like to provide a more stable EROFS when linux-4.19 is out,
> > >>>>>       and there are also two patchsets (the one is already sent out by Chao
> > >>>>>       and me, the other is previewing in linux-erofs mailing list and it will
> > >>>>>       be sent out after gathering enough testdata and feedback from community
> > >>>>>       and carefully reviewed), could you also please consider applying these
> > >>>>>       two patchsets in the later 4.19-rc (both >2, or the first patchset
> > >>>>>       could be in rc2 in advance) if it is convenient to do so, or the next
> > >>>>>       4.20 is also ok...
> > >>>>>
> > >>>>>  LINK: https://lore.kernel.org/lkml/20180821144937.20555-1-chao@kernel.org/
> > >>>>>        https://lore.kernel.org/lkml/1535076160-99466-1-git-send-email-gaoxiang25@huawei.com/    
> > >>>>
> > >>>> I applied those patch sets to my -next branch already, right?  So those    
> > >>>
> > >>> Yes, Thank you for applying those patches. :)
> > >>>    
> > >>>> would be going into 4.20-rc1, it is time now for "bugfixes only" for
> > >>>> 4.19-final.
> > >>>>
> > >>>> So perhaps we should just leave it as "BROKEN" for now for 4.19 and add
> > >>>> this to my tree now and let people work on it for the next few months in    
> > >>
> > >> I'm worry about that once we plan to reenable erofs in next x.xx-rc1, in the
> > >> merge window, if there are any other features change common api or structure in
> > >> vfs/mm/block, but related patch didn't cover erofs, that would make conflict
> > >> with erofs.
> > >>
> > >> So if that happens, we can just reminder them to cover erofs? or we should
> > >> handle this by just delay removing 'BROKEN' state?
> > >>
> > >> Thanks,
> > >>    
> > >>>> linux-next so that 4.20 has a solid base to start with?
> > >>>>    
> > >>>
> > >>> EROFS is be marked as "BROKEN" just because of conflict with
> > >>> XArray and the new mount apis, as Stephen Rothwell suggested in
> > >>>
> > >>> https://lore.kernel.org/lkml/20180802010705.24a72730@canb.auug.org.au/
> > >>>    
> > >>>> It might be easiest for Greg to add the disabling CONFIG_EROFS_FS patch
> > >>>> to the staging tree itself for his first pull request during the merge
> > >>>> window and then send a second pull request (after the vfs and maybe the
> > >>>> Xarray stuff has been merged by Linus) with these patches followed by a
> > >>>> revert of the disabling patch.    
> > >>>
> > >>> But these two features was still discussing in the mailing list even at the
> > >>> last time of 4.19-rc1 merge window. I cannot decide whether they were eventually
> > >>> get merged in 4.19 or not. But it seems that it is regretful that linux-4.19
> > >>> is out without XArray and the new mount apis.
> > >>>
> > >>> Therefore, I think EROFS should work for linux-4.19 without any modification
> > >>> if just revert the BROKEN mark.    
> > > 
> > > Ok, you are right, I'll go apply this.
> > >     
> > >>> EROFS works fine with the 4.19-rc1 code except that it has some __GFP_NOFAIL
> > >>> and BUG_ONs on error handling paths and very rarely race between memory
> > >>> reclaiming and decompression... :( I personally think it is complete enough
> > >>> for people to test since it is an independent and staging filesystem driver (no
> > >>> other influence...) Anyway, removing EROFS BROKEN mark at 4.20 is also ok of course...
> > >>>
> > >>> On the other head, if XArray and the new mount apis is still pending for 4.20,
> > >>> should EROFS uses the same policy as Stephen suggested? I have no idea how to do next...    
> > > 
> > > As the code is now part of the common tree that everyone works off of,
> > > any filesystem changes that happen will normally cover erofs as well.
> > > So this shouldn't be an issue anymore.    
> > 
> > Thanks very much for the help and explanation, we will keep an eye on those vfs
> > changes. :)  
> 
> Unfortunately, those vfs changes are still in the vfs tree in
> linux-next and cause a build failure in the erofs code.  I have
> disabled the build of erofs again for today.
> 
> Dave, Al, it would be good if you could add a patch/revise the series
> that adds the necessary erofs changes.

I still have to disable erofs .....

-- 
Cheers,
Stephen Rothwell

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