bio_vec start offset may be relatively large particularly when large
folio gets added to the bio. A bigger offset will result in avoiding the
single-segment mapping optimization and end up using expensive
mempool_alloc further.

Rather than using absolute value, adjust bv_offset by
NVME_CTRL_PAGE_SIZE while checking if segment can be fitted into one/two
PRP entries.

Suggested-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Kundan Kumar <kundan.kumar@samsung.com>
---
 drivers/nvme/host/pci.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 710043086dff..102a9fb0c65f 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -778,7 +778,8 @@ static blk_status_t nvme_map_data(struct nvme_dev *dev, struct request *req,
 		struct bio_vec bv = req_bvec(req);
 
 		if (!is_pci_p2pdma_page(bv.bv_page)) {
-			if (bv.bv_offset + bv.bv_len <= NVME_CTRL_PAGE_SIZE * 2)
+			if ((bv.bv_offset & (NVME_CTRL_PAGE_SIZE - 1)) +
+			     bv.bv_len <= NVME_CTRL_PAGE_SIZE * 2)
 				return nvme_setup_prp_simple(dev, req,
 							     &cmnd->rw, &bv);
 
-- 
2.25.1

On Thu, May 23, 2024 at 05:01:49PM +0530, Kundan Kumar wrote:
> bio_vec start offset may be relatively large particularly when large
> folio gets added to the bio. A bigger offset will result in avoiding the
> single-segment mapping optimization and end up using expensive
> mempool_alloc further.
> 
> Rather than using absolute value, adjust bv_offset by
> NVME_CTRL_PAGE_SIZE while checking if segment can be fitted into one/two
> PRP entries.

Thanks, applied to nvme-6.10.

Reviewed-by: Sagi Grimberg <sagi@grimberg.me>

Looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>