> >From Tony Battersby:
>
> When sending a SCSI command to a tape drive via the SCSI Generic (sg)
> driver, if the command has a data transfer length more than
> scatter_elem_sz (32 KB default) and not a multiple of 512, then I either
> hit BUG_ON(!valid_dma_direction(direction)) in dma_unmap_sg() or else
> the command never completes (depending on the LLDD).
>
> When constructing scatterlists, the sg driver rounds up the scatterlist
> element sizes to be a multiple of 512. This can result in
> sum(scatterlist lengths) > bufflen. In this case, scsi_req_map_sg()
> incorrectly sets bio->bi_size to sum(scatterlist lengths) rather than to
> bufflen. When the command completes, req_bio_endio() detects that
> bio->bi_size != 0, and so it doesn't call bio_endio(). This causes the
> command to be resubmitted, resulting in BUG_ON or the command never
> completing.
>
> This patch makes scsi_req_map_sg() set bio->bi_size to bufflen rather
> than to sum(scatterlist lengths), which fixes the problem.
>
> Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
>
> --- linux-2.6.24.2/drivers/scsi/scsi_lib.c 2008-02-10 23:51:11.000000000
> -0600
> +++ linux-2.6.24.2.work/drivers/scsi/scsi_lib.c 2008-02-22
> 16:20:09.000000000 -0600
> @@ -298,7 +298,6 @@ static int scsi_req_map_sg(struct reques
> page = sg_page(sg);
> off = sg->offset;
> len = sg->length;
> - data_len += len;
>
> while (len > 0 && data_len > 0) {
> /*
>
>
> Did this ever get sent to the stable team?
>
> Regards
> Mark
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