korg/linux
0
0
Fork 0
mirror of https://mirrors.bfsu.edu.cn/git/linux.git synced 2024-12-28 21:45:01 +08:00
Code Issues Packages Projects Releases Wiki Activity

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

Browse Source 
This reverts commit 84f7a9de06.

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 e383e16e84 ("scsi: sd: Remove
WRITE_SAME support") from mainline, hence this patch is only needed for
stable kernels.

Fixes: 84f7a9de06 ("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>
This commit is contained in:
Yu Kuai 2022-11-01 09:31:24 +08:00 committed by Greg Kroah-Hartman
parent 52c2329147
commit aad798a0b3
1 changed files with 2 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
drivers/scsi/sd.c
View File

@ -1072,6 +1072,7 @@ 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)
@ -1108,7 +1109,7 @@ 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;
}