On 6/24/2014 7:08 PM, Michael Christie wrote:
On Jun 24, 2014, at 7:53 AM, Martin K. Petersen <martin.petersen@xxxxxxxxxx> wrote:
"Mike" == Mike Christie <michaelc@xxxxxxxxxxx> writes:
Mike> The problem is WRITE_SAME requests are setup so that
Mike> req->__data_len is the value of the entire request when the setup
Mike> is completed but during the setup process it's value changes
Oh, I see. So things break because iSCSI uses scsi_transfer_length()
where the scatterlist length was used in the past.
How about this?
SCSI: Use SCSI data buffer length to extract transfer size
Commit 8846bab180fa introduced a helper that can be used to query the
wire transfer size for a SCSI command taking protection information into
account.
However, some commands do not have a 1:1 mapping between the block range
they work on and the payload size (discard, write same). After the
scatterlist has been set up these requests use __data_len to store the
number of bytes to report completion on. This means that callers of
scsi_transfer_length() would get the wrong byte count for these types of
requests.
To overcome this we make scsi_transfer_length() use the scatterlist
length in the scsi_data_buffer as basis for the wire transfer
calculation instead of __data_len.
Reported-by: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Debugged-by: Mike Christie <michaelc@xxxxxxxxxxx>
Signed-off-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
diff --git a/include/scsi/scsi_cmnd.h b/include/scsi/scsi_cmnd.h
index 42ed789ebafc..e0ae71098144 100644
--- a/include/scsi/scsi_cmnd.h
+++ b/include/scsi/scsi_cmnd.h
@@ -318,7 +318,7 @@ static inline void set_driver_byte(struct scsi_cmnd *cmd, char status)
static inline unsigned scsi_transfer_length(struct scsi_cmnd *scmd)
{
- unsigned int xfer_len = blk_rq_bytes(scmd->request);
+ unsigned int xfer_len = scsi_out(scmd)->length;
unsigned int prot_op = scsi_get_prot_op(scmd);
unsigned int sector_size = scmd->device->sector_size;
Do we need to check for the data direction. Something like
if (scmd->sc_data_direction == DMA_TO_DEVICE)
xfer_len = scsi_out(scmnd)->length;
else
xfer_len = scsi_in(scmnd)->length;
This condition only matters in the bidi case, which is not relevant for
the PI case.
I suggested to condition that in libiscsi (posted in the second thread,
copy-paste below).
Although I do agree that scsi_transfer_length() helper is not really
just for PI and not more.
I think Mike's way is cleaner.
diff --git a/drivers/scsi/libiscsi.c b/drivers/scsi/libiscsi.c
index 3f46234..abf0c3e 100644
--- a/drivers/scsi/libiscsi.c
+++ b/drivers/scsi/libiscsi.c
@@ -386,12 +386,14 @@ static int iscsi_prep_scsi_cmd_pdu(struct
iscsi_task *task)
rc = iscsi_prep_bidi_ahs(task);
if (rc)
return rc;
+ transfer_length = scsi_in(sc)->length;
+ } else {
+ transfer_length = scsi_transfer_length(sc);
}
if (scsi_get_prot_op(sc) != SCSI_PROT_NORMAL)
task->protected = true;
- transfer_length = scsi_transfer_length(sc);
hdr->data_length = cpu_to_be32(transfer_length);
if (sc->sc_data_direction == DMA_TO_DEVICE) {
struct iscsi_r2t_info *r2t = &task->unsol_r2t;
Sagi.
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