On Fri, Apr 18, 2025 at 05:02:38PM +0900, Damien Le Moal wrote:
> On 4/18/25 15:47, Leon Romanovsky wrote:
> > From: Kanchan Joshi <joshi.k@xxxxxxxxxxx>
> >
> > blk_rq_dma_map API is costly for single-segment requests.
> > Avoid using it and map the bio_vec directly.
> >
> > Signed-off-by: Kanchan Joshi <joshi.k@xxxxxxxxxxx>
> > Signed-off-by: Nitesh Shetty <nj.shetty@xxxxxxxxxxx>
> > Signed-off-by: Leon Romanovsky <leonro@xxxxxxxxxx>
> > ---
> > drivers/nvme/host/pci.c | 65 +++++++++++++++++++++++++++++++++++++----
> > 1 file changed, 60 insertions(+), 5 deletions(-)
<...>
> > static void nvme_unmap_data(struct nvme_dev *dev, struct request *req)
> > {
> > struct nvme_iod *iod = blk_mq_rq_to_pdu(req);
> > + unsigned int nr_segments = blk_rq_nr_phys_segments(req);
> > + dma_addr_t dma_addr;
> > +
> > + if (nr_segments == 1 && (iod->flags & IOD_SINGLE_SEGMENT)) {
>
> nvme_pci_setup_prps() calls nvme_try_setup_prp_simple() which sets
> IOD_SINGLE_SEGMENT if and only if the req has a single phys segment. So why do
> you need to count the segments again here ? Looking at the flag only should be
> enough, no ?
Yes, you are right. There is no need in extra check of nr_segments and
it is enough to rely on IOD_SINGLE_SEGMENT.
Thanks
