Re: [PATCH] block: set rq->cmd_flags with bio->opf instead of data->cmd_flags when bio is not Null

[John Garry]

On 28/01/2019 14:07, Christoph Hellwig wrote:
> > > 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.

As I understood, the problem is the scenario of calling 
blk_mq_make_request()->bio_integrity_prep() where we then allocate a bio 
integrity payload in calling bio_integrity_alloc().

In this case, bio_integrity_alloc() sets bio->bi_opf |= REQ_INTEGRITY, 
which is no longer consistent with data.cmd_flags.

John

> .