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

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Message-ID: <20251124143044.GA17164@lst.de>
Date: Mon, 24 Nov 2025 15:30:44 +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 Fri, Nov 21, 2025 at 02:21:34PM +0100, Uladzislau Rezki wrote:
> -               offset &= -DM_BUFIO_WRITE_ALIGN;
> -               end += DM_BUFIO_WRITE_ALIGN - 1;
> -               end &= -DM_BUFIO_WRITE_ALIGN;
> +               align = max(DM_BUFIO_WRITE_ALIGN, bdev_logical_block_size(b->c->bdev));
> +               offset &= -align;
> +               end += align - 1;
> +               end &= -align;
>                 if (unlikely(end > b->c->block_size))
>                         end = b->c->block_size;
> <snip>
> 
> and it fixes the setup which i described in the commit message, but i
> have question.

And this patch, using bdev_logical_block_size looks correct.

> 
> 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?