[PATCH] scsi: Update max_hw_sectors on rescan

[Brian King <brking@linux.vnet.ibm.com>]

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.
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@linux.vnet.ibm.com>
---
 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);
 }
-
-- 
2.39.3