[PATCH v7 03/12] nvdimm: pmem: guard data loop for dataless bios

[Li Chen]

pmem_submit_bio() handles flush-only bios before and after the data
loop. Keep dataless bios out of bio_for_each_segment() so the data path
only walks bios that actually carry bvec data.

Signed-off-by: Li Chen <me@linux.beauty>
---
Changes in v6:
- New patch.

 drivers/nvdimm/pmem.c | 36 +++++++++++++++++++++---------------
 1 file changed, 21 insertions(+), 15 deletions(-)

diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index 05d3de33e2706..82ee1ddb3a445 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -217,23 +217,29 @@ static void pmem_submit_bio(struct bio *bio)
 		}
 	}
 
-	do_acct = blk_queue_io_stat(bio->bi_bdev->bd_disk->queue);
-	if (do_acct)
-		start = bio_start_io_acct(bio);
-	bio_for_each_segment(bvec, bio, iter) {
-		if (op_is_write(bio_op(bio)))
-			rc = pmem_do_write(pmem, bvec.bv_page, bvec.bv_offset,
-				iter.bi_sector, bvec.bv_len);
-		else
-			rc = pmem_do_read(pmem, bvec.bv_page, bvec.bv_offset,
-				iter.bi_sector, bvec.bv_len);
-		if (rc) {
-			bio->bi_status = rc;
-			break;
+	if (bio_has_data(bio)) {
+		do_acct = blk_queue_io_stat(bio->bi_bdev->bd_disk->queue);
+		if (do_acct)
+			start = bio_start_io_acct(bio);
+		bio_for_each_segment(bvec, bio, iter) {
+			if (op_is_write(bio_op(bio)))
+				rc = pmem_do_write(pmem, bvec.bv_page,
+						   bvec.bv_offset,
+						   iter.bi_sector,
+						   bvec.bv_len);
+			else
+				rc = pmem_do_read(pmem, bvec.bv_page,
+						  bvec.bv_offset,
+						  iter.bi_sector,
+						  bvec.bv_len);
+			if (rc) {
+				bio->bi_status = rc;
+				break;
+			}
 		}
+		if (do_acct)
+			bio_end_io_acct(bio, start);
 	}
-	if (do_acct)
-		bio_end_io_acct(bio, start);
 
 	if ((bio->bi_opf & REQ_FUA) && !bio->bi_status)
 		ret = nvdimm_flush(nd_region, bio);
-- 
2.52.0