[PATCH 3.15 001/122] SCSI: use the scsi data buffer length to extract transfer size

[Greg Kroah-Hartman]

3.15-stable review patch.  If anyone has any objections, please let me know.

------------------

From: "Martin K. Petersen" <martin.petersen@xxxxxxxxxx>

commit 5616b0a46ed82eb9a093f752fc4d7bd3cc688583 upstream.

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>
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Reviewed-by: Sagi Grimberg <sagig@xxxxxxxxxxxx>
Fixes: d77e65350f2d82dfa0557707d505711f5a43c8fd
Signed-off-by: James Bottomley <JBottomley@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 include/scsi/scsi_cmnd.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/include/scsi/scsi_cmnd.h
+++ b/include/scsi/scsi_cmnd.h
@@ -309,7 +309,7 @@ static inline void set_driver_byte(struc
 
 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;
 


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