From: Yu Kuai yukuai3@huawei.com
This reverts commit 84f7a9de0602704bbec774a6c7f7c8c4994bee9c.
Because it introduces a problem that rq->__data_len is set to the wrong value.
before the patch: 1) nr_bytes = rq->__data_len 2) rq->__data_len = sdp->sector_size 3) scsi_init_io() 4) rq->__data_len = nr_bytes
after the patch: 1) rq->__data_len = sdp->sector_size 2) scsi_init_io() 3) rq->__data_len = rq->__data_len -> __data_len is wrong
It will cause that io can only complete one segment each time, and the io will requeue in scsi_io_completion_action(), which will cause severe performance degradation.
Scsi write same is removed in commit e383e16e84e9 ("scsi: sd: Remove WRITE_SAME support") from mainline, hence this patch is only needed for stable kernels.
Fixes: 84f7a9de0602 ("scsi: sd: Remove a local variable") Signed-off-by: Yu Kuai yukuai3@huawei.com Reviewed-by: Bart Van Assche bvanassche@acm.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/scsi/sd.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
--- a/drivers/scsi/sd.c +++ b/drivers/scsi/sd.c @@ -1074,6 +1074,7 @@ static blk_status_t sd_setup_write_same_ struct bio *bio = rq->bio; u64 lba = sectors_to_logical(sdp, blk_rq_pos(rq)); u32 nr_blocks = sectors_to_logical(sdp, blk_rq_sectors(rq)); + unsigned int nr_bytes = blk_rq_bytes(rq); blk_status_t ret;
if (sdkp->device->no_write_same) @@ -1110,7 +1111,7 @@ static blk_status_t sd_setup_write_same_ */ rq->__data_len = sdp->sector_size; ret = scsi_alloc_sgtables(cmd); - rq->__data_len = blk_rq_bytes(rq); + rq->__data_len = nr_bytes;
return ret; }