linux-kernel - Re: Backport dependencies helper

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Message-ID: <20200403142456.GC4088318@kroah.com>
Date:   Fri, 3 Apr 2020 16:24:56 +0200
From:   Greg KH <greg@...ah.com>
To:     Sasha Levin <sashal@...nel.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: Backport dependencies helper

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