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Date:   Sat, 28 Oct 2023 16:10:09 +0200
From:   Christian Brauner <brauner@kernel.org>
To:     David Sterba <dsterba@suse.cz>
Cc:     Stephen Rothwell <sfr@canb.auug.org.au>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux Next Mailing List <linux-next@vger.kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Christoph Hellwig <hch@lst.de>, Jan Kara <jack@suse.cz>
Subject: upcoming merge window: Where did the patches we had intended to
 depend on go? vfs-brauner tree with the btrfs tree
Message-ID: <20231028-heutzutage-wortfetzen-a54cdb387623@brauner>
References: <20231009104840.1bdadc80@canb.auug.org.au>
 <20231009-bauch-gedanken-e02e35804e03@brauner>
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 <20231011092004.GE2211@suse.cz>
 <20231012154210.GI2211@suse.cz>
 <20231023175513.GL26353@twin.jikos.cz>
 <20231024082543.575b3edd@canb.auug.org.au>
 <20231024-kolossal-ungelegen-f95c436de174@brauner>
 <20231024154620.GQ26353@twin.jikos.cz>
 <20231025-braumeister-sprung-44d486e2d721@brauner>
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In-Reply-To: <20231025-braumeister-sprung-44d486e2d721@brauner>
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On Wed, Oct 25, 2023 at 03:19:11PM +0200, Christian Brauner wrote:
> On Tue, Oct 24, 2023 at 05:46:20PM +0200, David Sterba wrote:
> > On Tue, Oct 24, 2023 at 10:59:39AM +0200, Christian Brauner wrote:
> > > On Tue, Oct 24, 2023 at 08:25:43AM +1100, Stephen Rothwell wrote:
> > > > Hi David,
> > > > 
> > > > On Mon, 23 Oct 2023 19:55:13 +0200 David Sterba <dsterba@suse.cz> wrote:
> > > > >
> > > > > I have updated my for-next branch again, sorry (top commit 1a4dc97c883a4f763cbaf50).
> > > > > There are some fixes I don't want to miss from the 6.7 pull request.
> > > > > There should be minimal change to the VFS tree conflict resolution so
> > > > > the diff should be reusable.
> > > > 
> > > > So, why did you not just merge in v6.6-rc7 (or better yet, the branch
> > > > that contains the fix(es) that Linus merged) and then apply your new
> > > > commits on top of that?  All the commits that were in the btrfs tree
> > > > have been rebased unchanged.
> > > 
> > > Please reconsider that and follow Stephen's suggestion. I'm sending pull
> > > requests this week and it'd be really annoying having to rebase
> > > vfs.super right before sending them.
> > > 
> > > We let you carry the required patches in btrfs on your insistence even
> > > though this effectively blocked two patchsets for a whole cycle
> > 
> > I hope I explained my reasons already under that series, core btrfs
> > changes should not go via VFS tree.
> > 
> > > and then
> > > merged in btrfs into vfs.super for that. Rebasing on such short notice
> > > is really not very nice.
> > 
> > Like said in the my other reply, the amount of VFS changes asks for
> > stopping taking new patches to btrfs and not continuing the patch
> > workflow that I've been doing. I understand that the inter-tree
> > dependencies are never easy so it's about finding some common way and
> > splitting the work over more releases eventually.
> > 
> > A resync of our branches a week before merge window, when there are no
> 
> Pull requests for VFS and a bunch of other trees are going out the week
> before the merge window opens. This has been requested multiple times.
> It's mentioned in almost every kernel release mail that pull requests
> should go out early.
> 
> So you rebasing a week before the merge window means rebasing
> right before the pr is sent for us. You might send pull requests later
> and are free to do so of course but you made us depend on your tree so
> we need some stability. That's why the rebase is problematic here.
> 
> > significant changes on my side does not sound like too short notice, but
> > you can feel otherwise of course.
> > 
> > > I'm going to wait with the rebase for a bit.
> > 
> > Ok, don't rebase. I'll push to linux-next the previous snapshot and will
> > find a way how to deliver the new patches.
> 
> Thanks! So I know you have your workflow and that's obviously fine but
> rebasing when other major trees depend on your tree is a problem and I
> believe Stephen has already linked to our official "Rebasing and
> merging" documentation:
> 
> "- Do not reparent a tree without a good reason to do so.  Just being on a
>    newer base or avoiding a merge with an upstream repository is not
>    generally a good reason."
> 
> [...]
> 
> "A frequent cause of merge-window trouble is when Linus is presented with a
> patch series that has clearly been reparented, often to a random commit,
> shortly before the pull request was sent.  The chances of such a series
> having been adequately tested are relatively low - as are the chances of
> the pull request being acted upon."
> 
> So I'll make sure to point out that we're depending on the btrfs tree
> and I have a clear merge commit explaining why we're pulling it in. All
> of that would be invalidated if you're rebasing. So not rebasing really
> helps us a lot.
> 
> I specifically put Linus in Cc so hopefully everyone is aware up front
> and there are no unnecessary suprises during the merge window.

So now I'm confused.

I prepared the vfs-6.7.super pull request yesterday and was about to
write the pull request message earlier and was about to send it out. And
I did the usual checklist and takinga another close look at all the
patches:

Where are the patches that you insisted go through the btrfs tree and
that made us merge in the btrfs/for-next tree into vfs.super?

commit d6b5ffd5520a ("btrfs: use the super_block as holder when mounting file systems")
commit 6d0eb684ad4a ("btrfs: open block devices after superblock creation")
commit 8f05745a1bf9 ("btrfs: split btrfs_fs_devices.opened")
commit 987b157f182e ("btrfs: call btrfs_close_devices from ->kill_sb")
commit b87aed6ff4c3 ("btrfs: always open the device read-only in btrfs_scan_one_device")

They were in btrfs/for-next on October 10, then you rebased and whatever
is in btrfs/for-next that we merged in doesn't contain any of these
patches. The top commit I have and that's visible in your repo is:
c6e8f898f56f ("btrfs: open code timespec64 in struct btrfs_inode")

So what happened and why weren't we told any of this as we did point out
that we want to depend on this?

I'm rebasing vfs.super onto plain v6.6-rc7 and dropping the btrfs merge
completely as this is now completely pointless and it doesn't feely very
transparent.

If the btrfs tree somehow ends up bringing in these changes then that's
fine. We've reworked locking requirements this cycle and so we will be
fine without these changes.

But you're actively blocking Jan from making progress with restricting
writers to a block device because they are required for that for the
second merge window.

And I hope we won't be repeating this cycle's churn again coming cycle.

And btw, as mentioned multiple times and reported upstream
https://lore.kernel.org/linux-btrfs/20230908-merklich-bebauen-11914a630db4@brauner
btrfs is broken when freezing block devices through the block layer
(e.g., device mapper). Something we also can't fix without these
patches.