linux-kernel - Re: [RESEND PATCH] dm-ebs: Mark full buffer dirty even on partial write

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Message-ID: <20251124170037.GA28939@lst.de>
Date: Mon, 24 Nov 2025 18:00:37 +0100
From: Christoph Hellwig <hch@....de>
To: Uladzislau Rezki <urezki@...il.com>
Cc: Christoph Hellwig <hch@....de>, Mikulas Patocka <mpatocka@...hat.com>,
	Benjamin Marzinski <bmarzins@...hat.com>,
	Alasdair Kergon <agk@...hat.com>, DMML <dm-devel@...ts.linux.dev>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mike Snitzer <snitzer@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RESEND PATCH] dm-ebs: Mark full buffer dirty even on partial
 write

On Mon, Nov 24, 2025 at 04:30:25PM +0100, Uladzislau Rezki wrote:
> > 
> > > 
> > > Why in dm-ebs we need to offload partial buffer < ubf size?
> > 
> > I don't understand this question.  What is ubf?  What does partial
> > buffer mean in this context, and what does offload mean?
> > 
> That was a typo :) i meant ubs - which is underlying block size or number
> of sectors which define the logical block size of the device. In our case
> it is 8K thus is 16 = 512 * 16 = 8K.
> 
> Partial buffer means, in context of dm-ebs, that within 8K buffer only
> part of it can be modified. For example, since we emulate 512B to 8K
> from upper layer to the device, a file system can write for example
> just first 4K within 8K window buffer and only that part is marked as
> dirty.
> 
> offloading or imposing the data to the lower layer. i.e. writing dirty
> buffers to the device calling submit_io().
> 
> Is it better? It might be that i missed something, feel free to correct.

I'm still lost what the question is, sorry.