linux-kernel - Re: [PATCH 2/2] mm: swap: print starting physical block offset in swapon

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Date: Wed, 22 May 2024 07:59:35 -0700
From: Christoph Hellwig <hch@...radead.org>
To: "Darrick J. Wong" <djwong@...nel.org>
Cc: Sukrit Bhatnagar <Sukrit.Bhatnagar@...y.com>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Pavel Machek <pavel@....cz>, Christian Brauner <brauner@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-xfs@...r.kernel.org, linux-pm@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: Re: [PATCH 2/2] mm: swap: print starting physical block offset in
 swapon

On Wed, May 22, 2024 at 07:56:37AM -0700, Darrick J. Wong wrote:
> On Wed, May 22, 2024 at 04:46:58PM +0900, Sukrit Bhatnagar wrote:
> > When a swapfile is created for hibernation purposes, we always need
> > the starting physical block offset, which is usually determined using
> > userspace commands such as filefrag.
> 
> If you always need this value, then shouldn't it be exported via sysfs
> or somewhere so that you can always get to it?  The kernel ringbuffer
> can overwrite log messages, swapfiles can get disabled, etc.

Scraping a block address from anything is just broken.

Wher is the code using this?  It needs a proper kernel interface.

Same about the warning crap in patch 1.