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Date: Wed, 19 Nov 2025 06:45:24 +0100
From: Christoph Hellwig <hch@lst.de>
To: Mikulas Patocka <mpatocka@redhat.com>
Cc: Benjamin Marzinski <bmarzins@redhat.com>,
	"Uladzislau Rezki (Sony)" <urezki@gmail.com>,
	Alasdair Kergon <agk@redhat.com>, DMML <dm-devel@lists.linux.dev>,
	Andrew Morton <akpm@linux-foundation.org>,
	Mike Snitzer <snitzer@redhat.com>, Christoph Hellwig <hch@lst.de>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] dm-bufio: align write boundary on
 bdev_logical_block_size
Message-ID: <20251119054524.GA19993@lst.de>
References: <20251020123350.2671495-1-urezki@gmail.com> <cdb598ce-88ec-0c3c-8e4b-b557093bea92@redhat.com> <aRvvSvyG8AK9hiCX@redhat.com> <faafd90d-e41c-dcfc-cc25-7f29ff4f958c@redhat.com>
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On Tue, Nov 18, 2025 at 06:45:55PM +0100, Mikulas Patocka wrote:
> I changed the patch below, so that it aligns write bios on 
> max3(DM_BUFIO_WRITE_ALIGN, bdev_logical_block_size(b->c->bdev), 
> bdev_physical_block_size(b->c->bdev)); - so that if physical block size is 
> greater than logical block size, the writes are aligned so that the device 
> doesn't do read-modify-write.

That doesn't make any sense whatsoever.  The physical block size must
be >= logical block size, and the block enforces that.