[SCSI] fix BUG when sum(scatterlist) > bufflen
authorTony Battersby <tonyb@cybernetics.com>
Tue, 5 Feb 2008 15:36:10 +0000 (10:36 -0500)
committerJames Bottomley <James.Bottomley@HansenPartnership.com>
Fri, 8 Feb 2008 00:02:44 +0000 (18:02 -0600)
commit4d2de3a50ce19af2008a90636436a1bf5b3b697b
tree7bf2d1974e54567cba53f258ccfaaa8d9922319a
parent76d78300a6eb8b7f08e47703b7e68a659ffc2053
[SCSI] fix BUG when sum(scatterlist) > bufflen

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@cybernetics.com>
Acked-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
drivers/scsi/scsi_lib.c