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

Uladzislau Rezki
2025-11-24T18:05:27Z

On Mon, Nov 24, 2025 at 06:00:37PM +0100, Christoph Hellwig wrote:
> 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.
>
No problem, i am fine with it.

Thank you for your input especially explaining the difference
between logical_block_size and physical_block_size for nvme device.

Appreciate it!

--
Uladzislau Rezki