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nvme-fc: use nr_phys_segments to determine existence of sgl
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>
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1 changed files with 15 additions and 4 deletions
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@ -2107,7 +2107,7 @@ nvme_fc_map_data(struct nvme_fc_ctrl *ctrl, struct request *rq,
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freq->sg_cnt = 0;
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if (!blk_rq_payload_bytes(rq))
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if (!blk_rq_nr_phys_segments(rq))
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return 0;
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freq->sg_table.sgl = freq->first_sgl;
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@ -2304,12 +2304,23 @@ nvme_fc_queue_rq(struct blk_mq_hw_ctx *hctx,
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if (ret)
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return ret;
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data_len = blk_rq_payload_bytes(rq);
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if (data_len)
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/*
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* nvme core doesn't quite treat the rq opaquely. Commands such
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* as WRITE ZEROES will return a non-zero rq payload_bytes yet
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* there is no actual payload to be transferred.
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* To get it right, key data transmission on there being 1 or
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* more physical segments in the sg list. If there is no
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* physical segments, there is no payload.
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*/
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if (blk_rq_nr_phys_segments(rq)) {
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data_len = blk_rq_payload_bytes(rq);
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io_dir = ((rq_data_dir(rq) == WRITE) ?
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NVMEFC_FCP_WRITE : NVMEFC_FCP_READ);
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else
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} else {
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data_len = 0;
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io_dir = NVMEFC_FCP_NODATA;
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}
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return nvme_fc_start_fcp_op(ctrl, queue, op, data_len, io_dir);
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}
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