Re: [PATCH 06/10] nvdimm-btt: use bvec_kmap_local in btt_rw_integrity

[Christoph Hellwig <hch@lst.de>]

On Mon, Feb 28, 2022 at 07:59:06PM -0800, Ira Weiny wrote:
> On Tue, Feb 22, 2022 at 04:51:52PM +0100, Christoph Hellwig wrote:
> > Using local kmaps slightly reduces the chances to stray writes, and
> > the bvec interface cleans up the code a little bit.
> > 
> > Signed-off-by: Christoph Hellwig <hch@lst.de>
> > ---
> >  drivers/nvdimm/btt.c | 10 ++++------
> >  1 file changed, 4 insertions(+), 6 deletions(-)
> > 
> > diff --git a/drivers/nvdimm/btt.c b/drivers/nvdimm/btt.c
> > index cbd994f7f1fe6..9613e54c7a675 100644
> > --- a/drivers/nvdimm/btt.c
> > +++ b/drivers/nvdimm/btt.c
> > @@ -1163,17 +1163,15 @@ static int btt_rw_integrity(struct btt *btt, struct bio_integrity_payload *bip,
> >  		 */
> >  
> >  		cur_len = min(len, bv.bv_len);
> > -		mem = kmap_atomic(bv.bv_page);
> > +		mem = bvec_kmap_local(&bv);
> >  		if (rw)
> > -			ret = arena_write_bytes(arena, meta_nsoff,
> > -					mem + bv.bv_offset, cur_len,
> > +			ret = arena_write_bytes(arena, meta_nsoff, mem, cur_len,
> 
> Why drop bv.bv_offset here and below?

Because bvec_kmap_local includes bv_offset in the pointer that it
returns.