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

Christoph Hellwig
2025-11-24T17:00:40Z

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.