netdev - Re: [PATCH 16/22] xen-blkfront: Make use of the new sg_map helper function

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Message-ID: <20170418142723.GA27133@char.us.oracle.com>
Date:   Tue, 18 Apr 2017 10:27:23 -0400
From:   Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:     David Laight <David.Laight@...LAB.COM>,
        xen-devel@...ts.xensource.com
Cc:     "'Logan Gunthorpe'" <logang@...tatee.com>,
        Christoph Hellwig <hch@....de>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Sagi Grimberg <sagi@...mberg.me>, Jens Axboe <axboe@...nel.dk>,
        Tejun Heo <tj@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Ross Zwisler <ross.zwisler@...ux.intel.com>,
        Matthew Wilcox <mawilcox@...rosoft.com>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Ming Lin <ming.l@....samsung.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
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        Steve Wise <swise@...ngridcomputing.com>
Subject: Re: [PATCH 16/22] xen-blkfront: Make use of the new sg_map helper
 function

On Tue, Apr 18, 2017 at 02:13:59PM +0000, David Laight wrote:
> From: Logan Gunthorpe
> > Sent: 13 April 2017 23:05
> > Straightforward conversion to the new helper, except due to
> > the lack of error path, we have to warn if unmapable memory
> > is ever present in the sgl.

Interesting that you didn't CC any of the maintainers. Could you 
do that in the future please?

> > 
> > Signed-off-by: Logan Gunthorpe <logang@...tatee.com>
> > ---
> >  drivers/block/xen-blkfront.c | 33 +++++++++++++++++++++++++++------
> >  1 file changed, 27 insertions(+), 6 deletions(-)
> > 
> > diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
> > index 5067a0a..7dcf41d 100644
> > --- a/drivers/block/xen-blkfront.c
> > +++ b/drivers/block/xen-blkfront.c
> > @@ -807,8 +807,19 @@ static int blkif_queue_rw_req(struct request *req, struct blkfront_ring_info *ri
> >  		BUG_ON(sg->offset + sg->length > PAGE_SIZE);
> > 
> >  		if (setup.need_copy) {
> > -			setup.bvec_off = sg->offset;
> > -			setup.bvec_data = kmap_atomic(sg_page(sg));
> > +			setup.bvec_off = 0;
> > +			setup.bvec_data = sg_map(sg, SG_KMAP_ATOMIC);
> > +			if (IS_ERR(setup.bvec_data)) {
> > +				/*
> > +				 * This should really never happen unless
> > +				 * the code is changed to use memory that is
> > +				 * not mappable in the sg. Seeing there is a
> > +				 * questionable error path out of here,
> > +				 * we WARN.
> > +				 */
> > +				WARN(1, "Non-mappable memory used in sg!");
> > +				return 1;
> > +			}
> ...
> 
> Perhaps add a flag to mark failure as 'unexpected' and trace (and panic?)
> inside sg_map().
> 
> 	David
> 
> 
> _______________________________________________
> Linux-nvdimm mailing list
> Linux-nvdimm@...ts.01.org
> https://lists.01.org/mailman/listinfo/linux-nvdimm

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