Commit 7d7fe3e4 authored by Yu Kuai's avatar Yu Kuai Committed by Zheng Zengkai
Browse files

scsi: sd: Revert "scsi: sd: Remove a local variable" 

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5YRAC


CVE: NA

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

This reverts commit 84f7a9de.

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 e383e16e ("scsi: sd: Remove
WRITE_SAME support") from mainline, hence this patch is only needed for
stable kernels.

Fixes: 84f7a9de ("scsi: sd: Remove a local variable")
Signed-off-by: default avatarYu Kuai <yukuai3@huawei.com>
Reviewed-by: default avatarBart Van Assche <bvanassche@acm.org>
Reviewed-by: default avatarJason Yan <yanaijie@huawei.com>
Signed-off-by: default avatarZheng Zengkai <zhengzengkai@huawei.com>
parent e97b8eb2

drivers/scsi/sd.c

+2 −1
Original line number Diff line number Diff line
@@ -1074,6 +1074,7 @@ static blk_status_t sd_setup_write_same_cmnd(struct scsi_cmnd *cmd) 
	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_cmnd(struct scsi_cmnd *cmd) 
	 */

	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;

}