linux-kernel - Re: [PATCH 5.18 112/181] vmcore: convert copy_oldmem_page() to take an iov

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Date:   Mon, 27 Jun 2022 18:27:12 +0200
From:   Heiko Carstens <hca@...ux.ibm.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        Baoquan He <bhe@...hat.com>, Christoph Hellwig <hch@....de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Sasha Levin <sashal@...nel.org>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>
Subject: Re: [PATCH 5.18 112/181] vmcore: convert copy_oldmem_page() to take
 an iov_iter

On Mon, Jun 27, 2022 at 01:21:25PM +0200, Greg Kroah-Hartman wrote:
> From: Matthew Wilcox (Oracle) <willy@...radead.org>
> 
> [ Upstream commit 5d8de293c224896a4da99763fce4f9794308caf4 ]
> 
> Patch series "Convert vmcore to use an iov_iter", v5.
> 
> For some reason several people have been sending bad patches to fix
> compiler warnings in vmcore recently.  Here's how it should be done.
> Compile-tested only on x86.  As noted in the first patch, s390 should take
> this conversion a bit further, but I'm not inclined to do that work
> myself.
> 
> This patch (of 3):
> 
> Instead of passing in a 'buf' and 'userbuf' argument, pass in an iov_iter.
> s390 needs more work to pass the iov_iter down further, or refactor, but
> I'd be more comfortable if someone who can test on s390 did that work.
> 
> It's more convenient to convert the whole of read_from_oldmem() to take an
> iov_iter at the same time, so rename it to read_from_oldmem_iter() and add
> a temporary read_from_oldmem() wrapper that creates an iov_iter.
> 
> Link: https://lkml.kernel.org/r/20220408090636.560886-1-bhe@redhat.com
> Link: https://lkml.kernel.org/r/20220408090636.560886-2-bhe@redhat.com
> Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
> Signed-off-by: Baoquan He <bhe@...hat.com>
> Reviewed-by: Christoph Hellwig <hch@....de>
> Cc: Heiko Carstens <hca@...ux.ibm.com>
> Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
> Signed-off-by: Sasha Levin <sashal@...nel.org>
> ---
>  arch/arm/kernel/crash_dump.c     | 27 +++-------------
>  arch/arm64/kernel/crash_dump.c   | 29 +++--------------
>  arch/ia64/kernel/crash_dump.c    | 32 +++----------------
>  arch/mips/kernel/crash_dump.c    | 27 +++-------------
>  arch/powerpc/kernel/crash_dump.c | 35 +++------------------
>  arch/riscv/kernel/crash_dump.c   | 26 +++------------
>  arch/s390/kernel/crash_dump.c    | 13 +++++---
>  arch/sh/kernel/crash_dump.c      | 29 +++--------------
>  arch/x86/kernel/crash_dump_32.c  | 29 +++--------------
>  arch/x86/kernel/crash_dump_64.c  | 41 +++++++-----------------
>  fs/proc/vmcore.c                 | 54 ++++++++++++++++++++------------
>  include/linux/crash_dump.h       |  9 +++---
>  12 files changed, 91 insertions(+), 260 deletions(-)

This one breaks s390. You would also need to apply the following two commits:

cc02e6e21aa5 ("s390/crash: add missing iterator advance in copy_oldmem_page()")
af2debd58bd7 ("s390/crash: make copy_oldmem_page() return number of bytes copied")