Tony Battersby wrote:
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: Tony Battersby <tonyb@xxxxxxxxxxxxxxx> --- --- linux-2.6.24-git14/drivers/scsi/scsi_lib.c.orig 2008-02-05 09:33:05.000000000 -0500 +++ linux-2.6.24-git14/drivers/scsi/scsi_lib.c 2008-02-05 09:33:10.000000000 -0500 @@ -301,7 +301,6 @@ static int scsi_req_map_sg(struct reques page = sg_page(sg); off = sg->offset; len = sg->length; - data_len += len;
Thanks for finding this. I am not sure what happened. That line got deleted in this commit when we fixed this problem:
http://git.kernel.org/?p=linux/kernel/git/jejb/scsi-misc-2.6.git;a=commit;h=bd441deaf341c524b28fd72831ebf6fef88f1c41 but was added back here: http://git.kernel.org/?p=linux/kernel/git/jejb/scsi-misc-2.6.git;a=commitdiff;h=c6132da1704be252ee6c923f47501083d835c238 Acked-by: Mike Christie <michaelc@xxxxxxxxxxx> - To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
