Any function which use scsi_execute_async() and transfers "odd" sized
data that doesn't align correctly with the segment sizes may have its
transfer length padded out to the closest segment size.
For writes, this results in unnecessary data being transfered to the
SCSI target. For reads, it affects the residual data length being
returned to the application since the residual length will be based on
the padded transfer size rather than the actual request size.
The easiest way to see this is by trying to read using the SG_IO ioctl a
large (>32k) buffer size from a tape device that only has a few bytes of
data stored for the current block. The resulting resid will generally be
incorrect.
I've fixed this simply by changing scsi_req_map_sg() so that it places
the requested transfer length in rq->data_len rather than the sum of all
the sg segments.
This patch applies against scsi_lib.c in 2.6.22.
Signed-off-by: Jeremy Linton <[email protected]>
--- linux-2.6.22/drivers/scsi/scsi_lib.c.orig 2007-07-11
19:07:06.000000000 -0500
+++ linux-2.6.22/drivers/scsi/scsi_lib.c 2007-07-11
18:43:36.000000000 -0500
@@ -350,7 +350,7 @@ static int scsi_req_map_sg(struct reques
}
rq->buffer = rq->data = NULL;
- rq->data_len = data_len;
+ rq->data_len = bufflen;
return 0;
free_bios:
-
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