linux-kernel - Re: [PATCH] Export MDRAID bitmap on disk structure in UAPI header file

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Message-ID: <CAH2-hcK-yF2SbxpXzB2c1Y73gjJxRfbPkmAOvmfM1Uh6QyT06g@mail.gmail.com>
Date: Mon, 6 Jan 2025 16:40:52 +0100
From: Tomáš Mudruňka <tomas.mudrunka@...il.com>
To: Christoph Hellwig <hch@...radead.org>
Cc: Song Liu <song@...nel.org>, Yu Kuai <yukuai3@...wei.com>, linux-raid@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Export MDRAID bitmap on disk structure in UAPI header file

> the bitmap format is not a userspace ABI, it is an on-disk format.
> As such it does not belong into the uapi.  It might make sense to
> create a clean standalone header just for the on-disk format that
> you could copy, though.

If you inspect the header in question, you'll find that this is the exact
reason why this header exists. To describe "physical layout" of
MD RAID devices. Which is just fancy way to say "on disk format".


$ head /usr/include/linux/raid/md_p.h
/* SPDX-License-Identifier: GPL-2.0+ WITH Linux-syscall-note */
/*
   md_p.h : physical layout of Linux RAID devices
          Copyright (C) 1996-98 Ingo Molnar, Gadi Oxman

po 6. 1. 2025 v 16:25 odesílatel Christoph Hellwig <hch@...radead.org> napsal:
>
> On Tue, Dec 31, 2024 at 04:09:27AM +0100, Tomas Mudrunka wrote:
> > When working on software that manages MD RAID disks from
> > userspace. Currently provided headers only contain MD superblock.
> > That is not enough to fully populate MD RAID metadata.
> > Therefore this patch adds bitmap superblock as well.
>
> the bitmap format is not a userspace ABI, it is an on-disk format.
> As such it does not belong into the uapi.  It might make sense to
> create a clean standalone header just for the on-disk format that
> you could copy, though.
>