nvme-fc: use nr_phys_segments to determine existence of sgl (9f7d8ae2) · Commits · 戴 / test

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>

drivers/nvme/host/fc.c

+15 −4

Original line number	Diff line number	Diff line
		@@ -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;

		/*
		* 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);
		if (data_len)
		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);
		}

Admin message