On 1/18/24 9:44 AM, John Garry wrote: > On 17/01/2024 21:36, Brian King wrote: >> This addresses an issue discovered on ibmvfc LUNs. For this driver, >> max_sectors is negotiated with the VIOS. This gets done at initialization >> time, then LUNs get scanned and things generally work fine. However, >> this attribute can be changed on the VIOS, either due to a sysadmin >> change or potentially a VIOS code level change. If this decreases >> to a smaller value, due to one of these reasons, the next time the >> ibmvfc driver performs an NPIV login, it will only be able to use >> the smaller value. In the case of a VIOS reboot, when the VIOS goes >> down, all paths through that VIOS will go to devloss state. When >> the VIOS comes back up, ibmvfc negotiates max_sectors and will only >> be able to get the smaller value and it will update shost->max_sectors. > > Are you saying that the driver will manually update shost->max_sectors after adding the scsi host? I didn't think that was permitted. That is what happens. The characteristics of the underlying hardware can change across a virtual adapter reset. Thanks, Brian > > Thanks, > John > >> However, when LUNs are scanned, the devloss paths will be found >> and brought back online, still using the old max_hw_sectors. This >> change ensures that max_hw_sectors gets updated. >> >> Signed-off-by: Brian King <brking@xxxxxxxxxxxxxxxxxx> >> --- >> drivers/scsi/scsi_scan.c | 6 +++++- >> 1 file changed, 5 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c >> index 44680f65ea14..01f2b38daab3 100644 >> --- a/drivers/scsi/scsi_scan.c >> +++ b/drivers/scsi/scsi_scan.c >> @@ -1162,6 +1162,7 @@ static int scsi_probe_and_add_lun(struct scsi_target *starget, >> blist_flags_t bflags; >> int res = SCSI_SCAN_NO_RESPONSE, result_len = 256; >> struct Scsi_Host *shost = dev_to_shost(starget->dev.parent); >> + struct request_queue *q; >> /* >> * The rescan flag is used as an optimization, the first scan of a >> @@ -1182,6 +1183,10 @@ static int scsi_probe_and_add_lun(struct scsi_target *starget, >> *bflagsp = scsi_get_device_flags(sdev, >> sdev->vendor, >> sdev->model); >> + q = sdev->request_queue; >> + if (queue_max_hw_sectors(q) > shost->max_sectors) >> + blk_queue_max_hw_sectors(q, shost->max_sectors); >> + >> return SCSI_SCAN_LUN_PRESENT; >> } >> scsi_device_put(sdev); >> @@ -2006,4 +2011,3 @@ void scsi_forget_host(struct Scsi_Host *shost) >> } >> spin_unlock_irqrestore(shost->host_lock, flags); >> } >> - > -- Brian King Power Linux I/O IBM Linux Technology Center
