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-rw-r--r--drivers/scsi/sd.c17
1 files changed, 16 insertions, 1 deletions
diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 0b09638fa39b..1f5d92a25a49 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -836,6 +836,7 @@ static int sd_setup_write_same_cmnd(struct scsi_cmnd *cmd)
struct bio *bio = rq->bio;
sector_t sector = blk_rq_pos(rq);
unsigned int nr_sectors = blk_rq_sectors(rq);
+ unsigned int nr_bytes = blk_rq_bytes(rq);
int ret;
if (sdkp->device->no_write_same)
@@ -868,7 +869,21 @@ static int sd_setup_write_same_cmnd(struct scsi_cmnd *cmd)
cmd->transfersize = sdp->sector_size;
cmd->allowed = SD_MAX_RETRIES;
- return scsi_init_io(cmd);
+
+ /*
+ * For WRITE SAME the data transferred via the DATA OUT buffer is
+ * different from the amount of data actually written to the target.
+ *
+ * We set up __data_len to the amount of data transferred via the
+ * DATA OUT buffer so that blk_rq_map_sg sets up the proper S/G list
+ * to transfer a single sector of data first, but then reset it to
+ * the amount of data to be written right after so that the I/O path
+ * knows how much to actually write.
+ */
+ rq->__data_len = sdp->sector_size;
+ ret = scsi_init_io(cmd);
+ rq->__data_len = nr_bytes;
+ return ret;
}
static int sd_setup_flush_cmnd(struct scsi_cmnd *cmd)