From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoph Hellwig <hch@infradead.org>
Subject: Re: [PATCH] block: set rq->cmd_flags with bio->opf instead of
 data->cmd_flags when bio is not Null
Date: Mon, 28 Jan 2019 06:07:16 -0800
Message-ID: <20190128140716.GA18162@infradead.org>
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> > for rq->cmd_flags. It will cause dix=0 in function
> > sd_setup_read_write_cmnd() when enabled DIX, which will cause IO
> > exception when enabled DIX.
> > 
> > For some IOs such as internal IO from SCSI layer, the parameter bio of
> > function blk_mq_get_request() is Null, so need to check bio to
> > decise rq->cmd_flags.

We have data->cmd_flags to deal with the NULL bio case.
blk_mq_make_request initializes data->cmd_flags from bio->bi_opf
just before calling blk_mq_get_request, so I'm really missing what you
are trying to fix here.