> -----Original Message----- > From: linux-scsi-ow...@vger.kernel.org [mailto:linux-scsi- > ow...@vger.kernel.org] On Behalf Of Elliott, Robert (Server Storage) > Sent: Sunday, 06 July, 2014 7:02 PM > To: Christoph Hellwig; James Bottomley > Cc: Martin K. Petersen; linux-scsi@vger.kernel.org > Subject: RE: [PATCH 06/10] sd: don't use scsi_setup_blk_pc_cmnd for discard > requests > > > > > -----Original Message----- > > From: linux-scsi-ow...@vger.kernel.org [mailto:linux-scsi- > > ow...@vger.kernel.org] On Behalf Of Christoph Hellwig > > Sent: Sunday, 29 June, 2014 8:35 AM > > To: James Bottomley > > Cc: Martin K. Petersen; linux-scsi@vger.kernel.org > > Subject: [PATCH 06/10] sd: don't use scsi_setup_blk_pc_cmnd for discard > > requests > > > > Simplify handling of discard requests by setting up the command directly > > instead of initializing request fields and then calling > > scsi_setup_blk_pc_cmnd to propagate the information into the command. > > > > Signed-off-by: Christoph Hellwig <h...@lst.de> > > --- > > drivers/scsi/sd.c | 43 ++++++++++++++++++++++++------------------- > > 1 file changed, 24 insertions(+), 19 deletions(-) > > > > diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c > > index 25f25dd..9737e78 100644 > > --- a/drivers/scsi/sd.c > > +++ b/drivers/scsi/sd.c > > @@ -691,8 +691,10 @@ static void sd_config_discard(struct scsi_disk *sdkp, > > unsigned int mode) > > * Will issue either UNMAP or WRITE SAME(16) depending on preference > > * indicated by target device. > > **/ > > -static int sd_setup_discard_cmnd(struct scsi_device *sdp, struct request > > *rq) > > +static int sd_setup_discard_cmnd(struct scsi_cmnd *cmd) > > { > > + struct request *rq = cmd->request; > > + struct scsi_device *sdp = cmd->device; > > struct scsi_disk *sdkp = scsi_disk(rq->rq_disk); > > sector_t sector = blk_rq_pos(rq); > > unsigned int nr_sectors = blk_rq_sectors(rq); > > @@ -704,9 +706,6 @@ static int sd_setup_discard_cmnd(struct scsi_device > *sdp, > > struct request *rq) > > > > sector >>= ilog2(sdp->sector_size) - 9; > > nr_sectors >>= ilog2(sdp->sector_size) - 9; > > - rq->timeout = SD_TIMEOUT; > > - > > - memset(rq->cmd, 0, rq->cmd_len); > > Is *cmd guaranteed to be zero at this point? > > With scsi-mq.2 I've seen UNMAP CDBs with garbage in CDB bytes > 2 to 5 (which causes a drive that checks reserved fields to > reject the command), which suggests there is a case in which > that is not guaranteed.
The problem in the existing sd_setup_discard_cmnd is that the memset runs before rq->cmd_len is set, so it zeroes out no bytes. sd_setup_write_same_ doesn't have that issue. --- Rob Elliott HP Server Storage -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
