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Date: Tue, 2 Apr 2024 15:18:22 +0200
From: Christoph Hellwig <hch@lst.de>
To: Hannes Reinecke <hare@suse.de>
Cc: Christoph Hellwig <hch@lst.de>,
	"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>
Subject: Re: Oddities in brd queue limits
Message-ID: <20240402131822.GA32081@lst.de>
References: <0cba8c5d-f014-4e48-9a6f-7724cf939c5c@suse.de>
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On Tue, Apr 02, 2024 at 03:17:26PM +0200, Hannes Reinecke wrote:
> Hi Christoph,
>
> brd ends up with the following queue limits:
>
> optimal_io_size: 0
> minimum_io_size: 4096
> hw_sector_size: 512
> physical_block_size: 4096
>
> which I find particularly odd; how can the minimum I/O size be _larger_ 
> than the hw_sector_size? Wouldn't that imply that we can only send I/O
> in units of physical block size, rendering the hw_sector_size pretty much 
> pointless?

The minimum_io_size is always larger or equal to hw sector size.
It really is the minimal efficient I/O size.