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Date: Mon, 24 Nov 2025 18:00:37 +0100
From: Christoph Hellwig <hch@lst.de>
To: Uladzislau Rezki <urezki@gmail.com>
Cc: Christoph Hellwig <hch@lst.de>, Mikulas Patocka <mpatocka@redhat.com>,
	Benjamin Marzinski <bmarzins@redhat.com>,
	Alasdair Kergon <agk@redhat.com>, DMML <dm-devel@lists.linux.dev>,
	Andrew Morton <akpm@linux-foundation.org>,
	Mike Snitzer <snitzer@redhat.com>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [RESEND PATCH] dm-ebs: Mark full buffer dirty even on partial
 write
Message-ID: <20251124170037.GA28939@lst.de>
References: <aRx_lCimJco5BPKA@redhat.com> <230baa83-cd79-f232-5fb8-1476115e1ae7@redhat.com> <20251119054635.GB19993@lst.de> <bcd929c2-88b0-36e9-0e22-4bb0293300b5@redhat.com> <20251120062146.GA29990@lst.de> <aR8E2ZZtOi0RZt06@pc636> <20251121072421.GA29754@lst.de> <aSBnXqX9jmoKuv4Y@pc636> <20251124143044.GA17164@lst.de> <aSR6EZrxvlseRhZp@pc636>
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User-Agent: Mutt/1.5.17 (2007-11-01)

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.