From: James Smart <jsmart2021@xxxxxxxxx>
For some nvme command, when issued by the nvme core layer, there
is an internal buffer which can cause blk_rq_payload_bytes() to
return a non-zero value yet there is no actual/real command payload
and sg list. An example is the WRITE ZEROES command.
To address this, when making choices on whether to dma map an sgl,
use blk_rq_nr_phys_segments() instead of blk_rq_payload_bytes().
When there is a sgl, blk_rq_payload_bytes() will return the amount
of data to be transferred by the sgl.
Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@xxxxxxx>
Signed-off-by: James Smart <jsmart2021@xxxxxxxxx>
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
drivers/nvme/host/fc.c | 19 +++++++++++++++----
1 file changed, 15 insertions(+), 4 deletions(-)
diff --git a/drivers/nvme/host/fc.c b/drivers/nvme/host/fc.c
index b29b12498a1a..ba8f2a9cbdaf 100644
--- a/drivers/nvme/host/fc.c
+++ b/drivers/nvme/host/fc.c
@@ -2107,7 +2107,7 @@ nvme_fc_map_data(struct nvme_fc_ctrl *ctrl, struct request *rq,
freq->sg_cnt = 0;
- if (!blk_rq_payload_bytes(rq))
+ if (!blk_rq_nr_phys_segments(rq))
return 0;
freq->sg_table.sgl = freq->first_sgl;
@@ -2304,12 +2304,23 @@ nvme_fc_queue_rq(struct blk_mq_hw_ctx *hctx,
if (ret)
return ret;
- data_len = blk_rq_payload_bytes(rq);
- if (data_len)
+ /*
+ * nvme core doesn't quite treat the rq opaquely. Commands such
+ * as WRITE ZEROES will return a non-zero rq payload_bytes yet
+ * there is no actual payload to be transferred.
+ * To get it right, key data transmission on there being 1 or
+ * more physical segments in the sg list. If there is no
+ * physical segments, there is no payload.
+ */
+ if (blk_rq_nr_phys_segments(rq)) {
+ data_len = blk_rq_payload_bytes(rq);
io_dir = ((rq_data_dir(rq) == WRITE) ?
NVMEFC_FCP_WRITE : NVMEFC_FCP_READ);
- else
+ } else {
+ data_len = 0;
io_dir = NVMEFC_FCP_NODATA;
+ }
+
return nvme_fc_start_fcp_op(ctrl, queue, op, data_len, io_dir);
}
--
2.20.1
