> +     /*
> +      ** Below code detects gaps/holes in IO data buffers.
> +      ** What does holes/gaps mean?
> +      ** Any SGE except first one in a SGL starts at non NVME page size
> +      ** aligned address OR Any SGE except last one in a SGL ends at
> +      ** non NVME page size boundary.
> +      **
> +      ** Driver has already informed block layer by setting boundary rules
> +      ** for bio merging done at NVME page size boundary calling kernel API
> +      ** blk_queue_virt_boundary inside slave_config.
> +      ** Still there is possibility of IO coming with holes to driver because
> +      ** of IO merging done by IO scheduler.

All this SGL to PRP code needs to go.

If you are seeing anything that's not a valid PRP after setting the
queue virt boundary then there's a block layer bug that needs to be
debugged and fixed. Regardless of whether you are using an I/O scheduler
or not.

Martin K. Petersen      Oracle Linux Engineering

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