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Date: Tue, 17 Jun 2025 06:43:42 +0200
From: Christoph Hellwig <hch@lst.de>
To: Ming Lei <ming.lei@redhat.com>
Cc: "Martin K . Petersen" <martin.petersen@oracle.com>,
	linux-scsi@vger.kernel.org, linux-block@vger.kernel.org,
	"K. Y. Srinivasan" <kys@microsoft.com>,
	Haiyang Zhang <haiyangz@microsoft.com>,
	Wei Liu <wei.liu@kernel.org>, Christoph Hellwig <hch@lst.de>,
	"Ewan D. Milne" <emilne@redhat.com>,
	Laurence Oberman <loberman@redhat.com>
Subject: Re: [PATCH] scsi: storvsc: set max_segment_size as UINT_MAX
 explicitly
Message-ID: <20250617044342.GB1824@lst.de>
References: <20250616160509.52491-1-ming.lei@redhat.com>
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In-Reply-To: <20250616160509.52491-1-ming.lei@redhat.com>
User-Agent: Mutt/1.5.17 (2007-11-01)

On Tue, Jun 17, 2025 at 12:05:09AM +0800, Ming Lei wrote:
> Set max_segment_size as UINT_MAX explicitly:
> 
> - storvrc uses virt_boundary to define `segment`
> 
> - strovrc does not define max_segment_size
> 
> So define max_segment_size as UINT_MAX, otherwise __blk_rq_map_sg() takes
> default 64K max segment size and splits one virtual segment into two parts,
> then breaks virt_boundary limit.
> 
> Before commit ec84ca4025c0 ("scsi: block: Remove now unused queue limits helpers"),
> max segment size is set as UINT_MAX in case that virt_boundary is
> defined.

Drivers should not have done this.  If you need this someone (probably
me) broke the block layer code ensuring it's not needed, and that
affects all drivers using virt_boundary.