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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Wed, 22 Aug 2018 11:41:11 -0700
Message-ID: <CA+55aFyLmwm2CDcXXhUpmovKjYaFfeP+95Bx5OZDsYT5iiHTCQ@mail.gmail.com>
Subject: Re: [GIT PULL] XArray for 4.19
To:     Matthew Wilcox <willy@infradead.org>
Cc:     linux-mm <linux-mm@kvack.org>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Wed, Aug 22, 2018 at 11:23 AM Matthew Wilcox <willy@infradead.org> wrote:
>
> Dan added an entirely new function here:
>
> http://git.infradead.org/users/willy/linux-dax.git/commitdiff/c2a7d2a115525d3501d38e23d24875a79a07e15e
>
> which needed to be converted to XArray.  So I should have pulled in his
> branch as a merge somewhere close to the end of my series, then done a
> fresh patch on top of that to convert it?

No, it doesn't matter if you rebase on top of a broken branch, or you
merge it in. Either way, it's broken and I can't merge your end
result.

You should simply NOT CARE about other branches. Particularly not
other branches that might not even get merged in the first place!

You should care about *YOUR* work.  You should make sure *your* work
is rock solid, and that it is based on a rock solid base. Not some
random shifting quick-sand of somebody elses development branch.

Sure, then linux-next will give a merge conflict, but at that point
YOU DO NOT REBASE OR MERGE. You tell linux-next how to merge it, and
mention it to me in the pull request.

Because at that point, I have the *choice* of merging just one of the
branches or both.  Or I can merge them in either order, and test them
independently?

See how that is fundamentally different from you tying the two
branches together and handing me a fait accompli?

Yes, yes, sometimes you have to tie branches together because one
branch fundamentally depends on the features the other branch offers.
But that should be avoided like a plague if at all possible.

And it damn well isn't an issue for something like xarray, which has a
life entirely independently of libnvdimm (and vice versa), and the
conflict was just random happenstance, not some "my changes
fundamentally rely on the new features you provide".

              Linus