linux-kernel - Re: [PATCH RFC] gen_init_cpio: Do fsync() only on regular files

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Message-ID: <aOSZo8h6l2XNin3C@infradead.org>
Date: Mon, 6 Oct 2025 21:40:03 -0700
From: Christoph Hellwig <hch@...radead.org>
To: dima@...sta.com
Cc: Nathan Chancellor <nathan@...nel.org>,
	Nicolas Schier <nicolas.schier@...ux.dev>,
	linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
	David Disseldorp <ddiss@...e.de>, Nicolas Schier <nsc@...nel.org>
Subject: Re: [PATCH RFC] gen_init_cpio: Do fsync() only on regular files

On Tue, Oct 07, 2025 at 12:55:03AM +0100, Dmitry Safonov via B4 Relay wrote:
> From: Dmitry Safonov <dima@...sta.com>
> 
> Here at Arista gen_init_cpio is used in testing in order to create
> an initramfs for specific tests. Most notably, there is a test that does
> essentially a fork-bomb in kdump/panic kernel, replacing build-time
> generated init script: instead of doing makedumpfile, it does call
> shell tests.

Why is is using fsync at all?  Seems like this was added in

commit ae18b94099b04264b32e33b057114024bc72c993
Author: David Disseldorp <ddiss@...e.de>
Date:   Tue Aug 19 13:05:45 2025 +1000

    gen_init_cpio: support -o <output_file> parameter

without any good explanation.  In general doing a per-file fsync
is going to horrible wreck performance, and given that no one is
interested in partial initramfs archives also rather pointless.