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Date: Tue, 27 Feb 2024 16:20:25 +0100
From: Christoph Hellwig <hch@lst.de>
To: Stefan Haberland <sth@linux.ibm.com>
Cc: Christoph Hellwig <hch@lst.de>, Jan Hoeppner <hoeppner@linux.ibm.com>,
	Heiko Carstens <hca@linux.ibm.com>,
	Vasily Gorbik <gor@linux.ibm.com>,
	Alexander Gordeev <agordeev@linux.ibm.com>,
	Christian Borntraeger <borntraeger@linux.ibm.com>,
	Sven Schnelle <svens@linux.ibm.com>, Jens Axboe <axboe@kernel.dk>,
	linux-block@vger.kernel.org, linux-s390@vger.kernel.org
Subject: Re: [PATCH 2/3] dasd: move queue setup to common code
Message-ID: <20240227152025.GB14628@lst.de>
References: <20240221125438.3609762-1-hch@lst.de> <20240221125438.3609762-3-hch@lst.de> <14bad51d-734e-4d4e-b47a-3f6af6794a40@linux.ibm.com>
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On Mon, Feb 26, 2024 at 05:49:30PM +0100, Stefan Haberland wrote:
> Could we call this dasd_*_max_sectors() or something like this?

Sure.

>> -	blk_queue_max_segment_size(q, PAGE_SIZE);
>> -	blk_queue_segment_boundary(q, PAGE_SIZE - 1);
>> -	blk_queue_dma_alignment(q, PAGE_SIZE - 1);
>> +	return DIAG_MAX_BLOCKS;
>
> You are dropping the shift here (and in the other discipline cases). This 
> might lead to smaller request sizes and decreased performance.
> Should be:
>
> return DIAG_MAX_BLOCKS << block->s2b_shift;

I actually wanted to move the shift to the caller, but forgot to add
it there.  But with the max_sectors naming it's probably better to
keep it in the disciplines.