Re: Backport dependencies helper

From: Greg KH
Date: Fri Apr 03 2020 - 10:25:02 EST


On Tue, Mar 31, 2020 at 08:32:17AM -0400, Sasha Levin wrote:
> Hi all,
>
> I wanted to share a resource I've been using to help me with doing
> backports to various stable kernels.
>
> In the Stable Kernel world, when we need to backport a patch, we'd
> rather take any relevant dependencies to make the patch work cleanly on
> an older kernel, rather than modifying the patch and diverging from
> upstream.
>
> This raises an interesting problem: how do we figure out which other
> patches might be "interesting" to look at? git-blame is a great tool,
> but it takes a while to go through the history of a patch, and given the
> volume of patches we need to look at, it just isn't enough.
>
> So here's a tool in the form of a git repo that can help point out these
> interesting patches:
>
> https://git.kernel.org/pub/scm/linux/kernel/git/sashal/deps.git/
>
> How does it work, you might ask? It's actually quite simple: Each
> directory represents a kernel version which we'll call K, and each file
> inside that directory is named after an upstream commit we'll call C,
> and it's content are the list of commits one would need to apply on top
> of kernel K to "reach" commit C.
>
> For example, let's say we want to apply:
>
> f8788d86ab28 ("Linux 5.6-rc3")
>
> On top of the v5.5 kernel tree. All we need to do is:
>
> $ cat v5.5/f8788d86ab28f61f7b46eb6be375f8a726783636
> f8788d86ab28 ("Linux 5.6-rc3")
> 11a48a5a18c6 ("Linux 5.6-rc2")
> bb6d3fb354c5 ("Linux 5.6-rc1")
>
> If you don't feel like cloning the repo (which contains quite a few
> files), you can also use kernel.org's web interface in a script that
> might look something like this:
>
> #!/bin/bash
> curl https://git.kernel.org/pub/scm/linux/kernel/git/sashal/deps.git/plain/$1/$2
>
> And then simply:
>
> $ ./deps.sh v5.5 f8788d86ab28f61f7b46eb6be375f8a726783636
> f8788d86ab28 ("Linux 5.6-rc3")
> 11a48a5a18c6 ("Linux 5.6-rc2")
> bb6d3fb354c5 ("Linux 5.6-rc1")
>
> Caveats:
>
> - Each file is limited to 50 entries. I feel that at that point it
> stops being useful.
> - Each file stops if a merge commit is hit.
> - I might have bugs in my scripts and some entries are broken, please
> report those if you see them.

This is really cool, thanks for posting this, and for doing this work.

greg k-h