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nvme-fc: use nr_phys_segments to determine existence of sgl

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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@wdc.com>
Signed-off-by: James Smart <jsmart2021@gmail.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
James Smart 2019-03-13 18:55:00 +01:00 committed by Jens Axboe
parent d11de63f2b
commit 9f7d8ae2f7
1 changed files with 15 additions and 4 deletions
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19
drivers/nvme/host/fc.c
View file

@ -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);
}